JPH03211040A - System of duplicating three-dimen- sional object using solid flat plate technique based on various transmission depth and beam profile data - Google Patents

Abstract

PURPOSE: To use a plurality of penetration depths independently or in simultaneous combination corresponding to conditions by providing a stimulating radiation source simultaneously containing at least two kinds of separate wavelengths having different penetration depths into a curable material and a platform control device for regulating the height of a platform. CONSTITUTION: A light source consists of several different light sources actually and each of the light sources generates a single or a plurality of stimulating radiation wavelengths. Stimulating radiations of different wavelengths generate different penetration depth values in a generally given photopolymer 22. Two kinds or more wavelengths are simultaneously used in order to solidify a resin or stimulating radiations of two or more kinds of wavelengths are used but, in a solidifying process, only one wavelength is used at a time and respective wavelengths are absorbed at the given depth of an imaginary photopolymerization initiator having different penetration depths into a resin to be used. A photopolymer mainly comprises various monomers generally and contains a photopolymerization initiator or other various components.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention generally relates to a three-dimensional plate technique and system for replicating three-dimensional objects.

[Prior Art and I\F1 Issues] In recent years, "three-dimensional plate" systems have come into use, such as those described in US Pat. No. 4,575,330.

Fundamentally, stereolithographic technology is a method for automatically forming complex three-dimensional objects by exposing multiple thin layers of a solidifiable fluid-like medium to approximate stimuli and solidifying them sequentially. The next layer is formed on top of each layer in sequence until all eight layers have been formed to form the entire object (the object thus formed is often referred to as a "part"). In a preferred embodiment, the fluid medium is a liquid photopolymer that is polymerized and solidified by exposure to UV radiation. Each polymerized layer forms a thin cross-section of a new type of three-dimensional part.

This fabrication method is an extremely powerful means of quickly reducing design ideas to physical form to form prototypes. Additionally, complex three-dimensional parts can be quickly fabricated without machining. Since this system uses a computer to generate the batten cross-sections, it is easily connected to a CAD/CAM system.

Presently preferred polymers are cured by ultraviolet light, and the curing rate of these polymers using conventional ultraviolet light is sufficiently rapid for their use as suitable forming materials. The liquid that is not polymerized during the formation of the three-dimensional part is still usable and remains in the container for the formation of the next three-dimensional part. The ultraviolet laser forms a small, intense U-spot that is moved along the liquid surface with a predetermined flick by a galvanometer or servo-mirror X-Y scanner. The scanner is driven by computer generated vectors or the like. With this technique, precise intricate bangs are formed.

A preferred three-dimensional plate system includes a laser scanner;
It includes a container containing a polymerizable liquid and an object support platform that is moved up and down, and a control computer. The system is programmed to form plastic parts by forming one thin section at a time, layer by layer, to form the desired three-dimensional object.

In early volumetric plate technology devices, actinic radiation was used to solidify the fluid medium. This technique is described in the aforementioned US Pat. No. 4,575,330.

In this referenced patent, there is a teaching that the actinic radiation absorption capacity of a fluid medium is an important factor in determining its ability to solidify to form a thin layer of condensable material. However, this reference patent does not disclose methods, techniques and apparatus for predicting desired properties of solidified materials, nor does it disclose methods and techniques for controlling such properties. Other techniques that do not develop this aspect of the invention are disclosed by E. V. Fudim. This technology is described in U.S. Pat. Nos. 4,752,498 and 4,801,477, Mechanical
An article in the September 1985 issue of Engineering,
”A New Method of Three-D
annual Hieromachine
g” and an article in the March 1986 issue of Machine Design, “Sculpting Parts w.
The most interesting of these citations is the paper, “Sculpting P.
“arts with Light”.

In this paper, Fudim describes the use of Beer's law and the transmission coefficient. The author also uses the minority Web equation derived from Beer's law.

But the author makes the same mistakes as his predecessors. The authors are not aware of the effectiveness of each wavelength's respective penetration depth or beam profile information to make accurate predictions of cure depth and other related cure parameters. This failure is related to the author's emphasis on the use of French exposure through masks. Another approach before the above two approaches is Applied Photo
l1erb of graphic engineering
ert paper, “5olid 0bject Gener
a-tion (August 1982). In this paper, Herbert appears to describe the use of a possibly single wavelength laser to expose and solidify the material. Herbert does not explain the relationship between wavelength absorption and layer forming ability. In this regard,
Herbert recommended instead the use of photobleached liquid photopolymers, but this makes it more difficult to obtain predictable and controllable results. Photobleaching means that resins and partially set materials lose their ability to absorb actinic radiation as they absorb successive doses of radiation. For example, photoinitiator byproducts do not absorb relatively as strongly as the photoinitiator itself. He
As described by Robert, the polymerized material completely stopped wicking, exposing the lower area to the full light intensity of the beam. Herbert describes the formation of test objects to determine effectiveness parameters such as cure depth and overeffect required for interlayer adhesion.

Another prior approach is the Review of Science
1981 9 of ``ntific Instruments''
Monthly issue of Kodama paper, “Au7omatic Meth”
od for Fabricating a
Three-Dimensional Plastic
Model with Photo-hardeni
In this paper, Kodama describes the use of actinic radiation sources and also presents plots of cure depth:exposure curves.Kodama, like Herbert, describes the use of actinic radiation sources and shows plots of cure depth:exposure curves. It does not teach the interrelationship of formative abilities.

All these approaches have the disadvantage that each time the desired 3D part is created, multiple test 3D parts must be created to determine the cure depth: exposure parameters and other required characteristics. There is. This is especially true when using multiple wavelength sources. Since the first sale of this technology by 3DS Systems, Inc. of Valencia, Calif., there has been an increasing need in the industry to develop techniques to rapidly create more accurate and stronger three-dimensional parts. Unless there is a technology that solves these problems, further development of this technology will be prohibited. The technology of the present invention solves these problems and has higher resolution, higher precision, shorter forming time, greater efficiency, and higher physical properties, thus facilitating the recruitment of workers in the forming process. It enables the formation of three-dimensional parts with less

Many curable materials closely follow Beer's law upon absorption of actinic radiation. According to this law, the intensity of radiation (I) at a certain depth (d) in a material is the optical intensity at the surface of the material IOX divided by the depth (d) of the base of the natural logarithm (e) divided by the penetration depth of the material It is related to negative powers of distance (Dp). This is expressed by the formula below.

I (d) = 工 o/ed/l)p The penetration depth is inversely proportional to the radiation absorption capacity of the material.

For the photopolymers used in the cited art above, and for many other photopolymers, the depth of penetration is wavelength dependent. These cited techniques use resin and wavelength combinations that reach various net penetration depths. The three-dimensional part formation in all of these references is based on the concept of net penetration depth rather than a superposition of various penetration depths. However, these references do not disclose that different wavelength penetration depths can be used to obtain different properties from partially solidified polymers. Nor does the reference indicate that using a particular actinic wavelength can optimize the penetration depth of a given resin to form a three-dimensional part using a particular layer thickness. Further, it does not disclose that in order to effectively use multiple wavelengths, the penetration depth of each wavelength must be considered. Neither of the references proposes considering multiple penetration depths when forming laminated three-dimensional parts by stereolithographic techniques. In this sense, unlike the multi-faceted consideration of the present invention, only the penetration depth and solidification ability of the material were considered in the past.

The first commercially available stereolithographic devices used a single actinic wavelength and corresponding resin, and combinations of wavelengths and curable resins with properties suitable for use with specific layer thicknesses. Therefore, this approach still considered only the penetration depth and the combination of cohesive properties and hardening depth.

In summary, in conventional stereolithography (SLA) equipment, the combination of stimulating radiation and photopolymer resin is
Only the penetration depth of radiation into the curable resin was considered and utilized. However, the ideal penetration depth varies from case to case, as discussed in detail below. Therefore, it would be desirable to be able to use a plurality of penetration depths, either singly or in simultaneous combinations, depending on the situation, when operating an SLA, and this constitutes a primary objective of the present invention.

A large penetration depth may be preferred in order for each layer of the three-dimensional part to be formed as quickly as possible for a given layer thickness, all other things being equal. But all other conditions are not equal.

Such a claim states that the deeper the penetration depth, the faster the required amount of radiation stimulation rays will reach and solidify a given point, thus producing the deepest thickness of cured material in the shortest amount of time. I'm assuming. Part of this assumption is accurate: the greater the amount of radiation that reaches a particular point in the resin, the deeper the penetration depth. However, this assumption is incorrect in other respects.

This is because the solidification (gelation) point of a material is not based on the amount of light that reaches a unit volume, but rather on the amount of light absorbed by that unit volume that can produce the desired solidification reaction. In the case of liquid photopolymers, this corresponds to the absorption per unit volume of stimulating radiation by the photoreactive element in the resin (generally the photoinitiator) and the polymer formation efficiency of the radiation/initiator. There is. In the case of a reaction that melts a powder and then solidifies the liquid formed again to form a truly solidified three-dimensional part, this is the net energy (per unit volume) produced in a given volume at a particular time. corresponds to the energy of human power minus the energy emitted from this unit volume),
Since this is the amount of absorption, it depends on the wavelength. - There is therefore a certain penetration depth characterized by a minimum time for gelling the material to a certain depth. Other penetration depths (depending on wavelength, resin, and other parameters) require longer gelation times due to gelation. However, drawing speed is not the only criterion included in the objectives of these techniques. In the case of photopolymers, for example, the stiffness of the gelled material, the amount of strain, and the effect of overexposure in a given area must also be considered. The penetration depth will therefore be optimized by the present invention to yield the most desirable net result based on a variety of conflicting factors. The dominance of these factors varies from case to case. There are also several factors.

Conventional SLA uses multiple penetration depths based on the above considerations, resulting in a few problems.

For example, some lasers have multiple wavelengths or multiple lines, requiring special considerations to use these wavelengths with maximum efficiency in fabricating high-resolution volumetric plates. Without such special considerations, the ways in which such lasers can be used are limited. i.e. 1
2) use a filter that blocks all wavelengths from the beam except those used during SLA, since different wavelengths generally have different penetration depths; 2) remove the photopolymer/ A three-dimensional part for testing is formed to determine the forming characteristics of the beam combination. However, in the first approach mentioned above, some of the light is not used, so
Wastes laser power.

Therefore, it would be desirable to avoid such waste of power without sacrificing SLA performance. Under current SLA usage conditions, wasted power is extremely costly.

A second approach is necessary to determine the formation properties. This is because the output loss of each line of multiple lasers is different, so if only the overall light intensity is considered, the effect of multiple lines becomes unpredictable11. However, this second approach is laborious and time consuming. Powerful argon ion lasers that emit multiple lines are now available and it is desirable to use such lasers in SLA.

Bending of three-dimensional parts is another problem that occurs when using SLA.
There are two problems. This bending occurs because the photopolymer contracts upon effect. As the top layer becomes effective and contracts, it pulls up on the previous layer, creating a strain called bending. This is undesirable because it distorts the shape of the three-dimensional part so that it no longer matches the desired shape. SLAs that minimize such distortions are highly desirable. This type of distortion is described in detail in US Pat. No. 339,246.

For a more detailed description of volumetric plate technology, see U.S. Pat. No. 4,575,330 and co-pending U.S. patent applications listed below. These patent applications, together with their appendices and attached materials, are cited as references.

U.S. Patent No. 339,246, filed April 17, 1989, “5TEI?EOLIT) IOGRAPHICCUR
L REDUCTION"; Dkt.

2- No. 186/166: U.S. Patent No. 331,664, filed on March 31, 1989, “METHOD AND APPARATUS F
ORPRODUCTION 0FHIGHRESOLU
TION THREE-DIMENSIONALOBJ
ECT BY 5TEREOLITHOGRAPHY”
; U.S. Patent No. 183,015, 1988, filed on April 18, ``METHOD AND APPARATUS''
FORPRODUCTION OFTHREE-DIM
ENSIONAL 0BJECTIONS BY 5T
EREO-LITHOHOGRAPHY”: U.S. Patent No. 268,429, filed November 8, 1988, “METHOD FORCURING PARTI
ALLY POLYMERIZED PARTS”; U.S. Patent No. 268,428, filed November 8, 1988, METHOD FORFINISHING PAR
TIALLY POLYMERIZED PARTS”
: U.S. Patent No. 268, No. 408, filed November 8, 1988, METHOD FORDRAINING PA
RTIALLY POLYME-RIZED PART
S”: U.S. Patent No. 268, No. 816, filed November 8, 1988, APPARATUS AND METHOD F
ORPROFILING ABEAM": U.S. Patent No. 268, No. 907, filed November 8, 1988, "APPARATUS AND METHOD
FORC0RRECTING FORDRIFT IN
PRODUCTION OF 0BJECTS BY
STEREOLITHOGRAPHY”: US Patent No. 2
68, No. 837, filed on November 8, 1988, '”A
PPARATUS AND METHOD FORCA
LIBRATING AND NORMALIZING
A 5TEREOLITHOGRAPHICAPPAR
ATUS”: U.S. Patent No. 249, No. 399, September 1988, 26
DAY APPLICATION, METHOD AND APPARATUS
FORPRODUCTION OFTHREE-DIM
ENSIONAL 0BJECTS BY 5TERE
O-LITHOGRAPHY''; U.S. Patent No. 365,444, filed June 12, 1988, INTEGRATED 5TEREOLITHO
GRAPHY”: U.S. Patent No. 265,039, 198
8. Filed on October 31st, “APPARATUS AND
METHOD FORMEASURING ANDC
,0NTROLLING THE' LEVEL OF
A FLUID”; and U.S. Patent No. 289,801
No., filed March 31, 1989, “METHOD AN
D APPARATUS FORPRODUCTION
0F=15 HIGHDIMENSIONAL 0BJECTS
SUMMARY OF THE INVENTION Briefly, the present invention provides an improved stereolithographic apparatus (SLA) and improved method for forming three-dimensional parts from effective materials in general. irritating properties (i.e.,
chemical action or melting action) that enables (predicts, determines, generates or controls) multiple penetration depths of radiation (such as ultraviolet light, visible infrared radiation, electron beams, or chemical sprays). From a determinative and/or predictive point of view, these desirable properties include determining the depth of cure resulting from a given exposure, determining the effect width, determining the required minimum surface angle (MSA), determining the optimal skin fill spacing, and determining the partial skin fill spacing. These include, but are not limited to, determining the cross-sectional stiffness of the polymerized material, determining the amount of bending strain, and determining the overeffect necessary to create interlayer adhesion. From these determined values, specific forming techniques are used to form the proper three-dimensional part. From a control and fabrication perspective, the penetration depth can be controlled to obtain optimal properties such as layer thickness, maximum drawing speed, minimum print-through, maximum hardness, maximum bending, and maximum resolution. I can do it. Important aspects of the invention are the properties of the resin used, the corresponding penetration depth for that resin, the wavelength of the stimulating radiation used to solidify this resin, and the stimulating radiation beam acting on the resin surface. to integrate light intensity profiles. Prediction, determination, creation or control of multiple penetration depths is performed in an automated manner.

Various factors are optimized by considering multiple penetration depths. The production speed of the three-dimensional part is optimized to the extent permitted by other factors.

The first factor is the vertical resolution used to form the three-dimensional part. In other words, this factor is the selected layer thickness. The greater the layer thickness (and cure depth), the more inaccurate the resolution of the shape of the three-dimensional part. The resolution required by the user varies from case to case.

The second factor is the additional exposure added to a location by chance. This is called "print-through." For example, SL
A crosshatch vector (tracing of UV rays to cure the photopolymer surface) to form a three-dimensional part
When using , the intersection points of the traces receive twice the exposure of the rest of the traces. Such a method of formation is described in US Pat. No. 331,664. The deeper the penetration depth, the deeper the overhardening at the intersection point. User tolerance for such overcuring varies.

The third factor is the hardness of the layer and the difference in hardness between the top and bottom of the layer. If the penetration depth is much shorter than the layer thickness,
The top of the layer is harder than the bottom. This is because by the time the bottom part has received enough exposure to gel, the top part has received additional exposure to polymerize and harden well beyond the gel point. This affects adhesion to the next layer, cantilever stiffness, and "green" stiffness before the object is fully cured and hardened. The desired hardness of the layer and the difference in hardness between the upper and lower portions of the layer will vary.

The fourth factor is the radiation beam profile (eg, laser beam profile), which is described in co-pending US patent application Ser. No. 268,816.

Commercially available laser beams may not have a uniform light intensity cross section or "profile." Many parts of the beam may have greater light intensity than other parts, thus resulting in greater exposure. For example, the center of the beam may have a higher light intensity than the outer periphery. Because of this greater light intensity and exposure in the center, the cure depth is greater in the center. Differences in cure depth are caused by differences in exposure. The degree of this difference in cure depth also depends on the penetration depth of the material and the polymerization and gelation properties of the material. This combination influences the solidification properties of the material and thus controls the type of processing techniques that can be implemented to produce the desired net result. For example, a non-uniform profile of the beam scan 19- along a line results in non-uniform cure depth (non-uniform shape of the bottom of the formed solidified material).

The depth of cure of a solidified (or at least gelled) material can no longer be determined by the average light intensity and scanning speed of the beam, but must be determined by the beam profile. The width of the line formed is no longer a function of the beam diameter, but of the exact profile of the beam and the scanning speed.

As the penetration depth varies, the interrelationship between cure width and cure depth changes.

The equilibrium conditions necessary to obtain the desired three-dimensional part vary.

These factors vary from application to application, from SLA to SLA, from 3D part to 3D part, and from part to part of each layer of the 3D part. The present approach uses multiple penetration depths and beam profile systems during and between SLA operations to aid in determining, creating and/or controlling proper variables.

In a first preferred embodiment, multiple penetration depths are provided by different wavelengths of actinic radiation, and each wavelength has a different penetration depth into the resin, so that 20- each wavelength is This results in different properties of the partially solidified volume that is forming from the coalescence. These different properties give rise to the possibility of using different wavelengths to obtain different desired properties for different formation situations. Examples include using different wavelengths to optimize forming properties for different layer thicknesses, using different wavelengths to control print-through, and using different wavelengths to optimize part forming times. Includes examples of wavelength usage. Different wavelengths can be used singly (once at a time) or simultaneously.

The apparatus and method of the present invention allows for the controlled and/or automated use of multiple wavelengths of stimulating radiation simultaneously in a stereolithographic formation process. This is a major advance over traditional approaches that used any one of the approaches described below. 1) the use of a single wavelength of actinic radiation, or 2) the use of multiple wavelengths in an inconsistent, haphazard, unevaluable, uncontrollable, and non-automatic manner, resulting in the laborious use of multiple parts. Requires assembly steps and/or results in low quality, low resolution three-dimensional parts. The first approach reduces the efficiency with which the actinic radiation generated is used to solidify the liquid photopolymer. Although the second approach described above is more efficient in the use of radiation, it provides less control over the properties of the partially solidified material from the photopolymer. A novel feature of the present invention lies in overcoming these drawbacks of conventional approaches. The automated and/or controlled use of multiple wavelengths according to the present invention constitutes a variety of useful approaches: 1) minimal control over the irritating radiation source, but the desirable ability to predict formation properties; , thus predicting the possibility of producing an acceptable product before forming and knowing whether to use a different forming technique; 2) controlling a multi-wavelength radiation source to control different wavelengths; Therefore, the penetration depth can be controlled, and the power and power distribution of each wavelength can be controlled to produce the desired specific properties in a partially solidified unit volume, much better than if a single wavelength were used. Performs characteristic control.

3) Easy forming techniques using a single wavelength (single penetration depth) with efficient production with multiple wavelengths, balancing the resin to produce the same penetration depth (and critical exposure and efficiency) for each wavelength. can be used.

In a second preferred embodiment, multiple penetration depths are provided by varying the liquid photopolymer. As a result, optimum characteristics can be obtained from different formation conditions. The cured material is modified by substitution or alteration.

These embodiments can be combined with each other and other embodiments are possible within the scope of the invention. Hereinafter, the present invention will be explained in detail with reference to embodiments shown in the drawings.

73- [Embodiment 1] The stereolithographic apparatus to which the present invention is applied is capable of producing physical and A three-dimensional part is made by forming a cross-sectional pattern of the object to be made on a selected surface of a fluid medium, such as a UV-curable medium, which can change the physical state. Radiation assimilable powders can be used, for example plastic powders and sinterable metal powders.

Successive adjacent layers representing successive adjacent cross-sections of the object are automatically formed and integrated into each other to form a graded laminate or laminar structure of the object, thus substantially eliminating the fluid medium during the plate-making process. Three-dimensional parts are formed from flat or sheet-like surfaces.

FIG. 1 is a cross-sectional view of a stereolithography system. The container 21 is filled with a UV-curable zeta polymer 22 or similar and forms a processed surface (!3). A programmable light source 26 or the like of ultraviolet light forms an ultraviolet spot 27 on the surface 23. The spot 27 is 26 is movable along the surface by a reflector or other mechanical or engineering element (not shown in FIG. 1) used with surface 23.
The position of the upper spot is controlled by computer controller 28. A control device 28 controls the formation of the cross section by means of CAD data, which is generated by a data generating device 20, such as a CAD design system, and transmitted, for example, in Figs format, to a computer conversion system 19, where it defines the object. The information is specially sliced and processed to reduce stress, curl, and distortion, and to increase prepress resolution, intensity, and accuracy before being transmitted to system 28.

A movable elevator platform 21 inside the container 21 is selectively moved up and down, the position of which is controlled by a system 28. 30c, 30 as the device operates
A three-dimensional part 30 is formed by stepwise formation of integrated layers such as b, 30a, etc.

The surface of the UV curable liquid 22 is maintained at a constant level within the container 21 and exposed to ultraviolet light or other suitable form of reactivity of sufficient intensity to produce a bath that cures and converts the liquid into a solid material. A spot 27 of stimulation is moved along the work surface 23 according to programming. As the liquid 22 hardens to form a solid material, the elevator platform 29, which was initially just below the surface 23, is lowered from this surface in a programmed manner by a suitable actuator. In this way, the initially formed solid material is lowered below the liquid surface 23 and waits for new liquid 22 to cover this layer and form a new working line 23. The distance between the new working surface 23 and the upper side of the previously hardened layer is equal to the thickness of the layer to be formed next. This new liquid portion is converted into a solid by the programmed UV spot 27, and this newly solidified layer adheres to the layer below it. This process continues until the entire three-dimensional part 30 is formed. Then, this three-dimensional part 3° is taken out from the container 21 and prepared for forming the second part. The next section, or any other new section, can be created by changing the design, data, or program of the computer 28 or CAD data generator 2°.

The light source 26 of the stereolithographic system according to the preferred embodiment of the invention is typically an argon ion ultraviolet laser. Another embodiment is Liconix 5unnyval
e California model 4240-NH
A helium-cadmium ultraviolet laser such as the eCd Multimode La5er is used.

Commercially available stereolithography systems have other components and subsystems than those shown in FIG. For example, commercially available systems include a frame, a housing, and a control panel. Commercially available systems may also include means for shielding personnel from excessive ultraviolet light and may include means for observing the three-dimensional part 30 as it is formed. Commercially available units also include safety measures to control ozone and hazardous gases, and the usual high pressure safeguards and interlocks. Some commercially available units also include means for effectively shielding sensitive electronic equipment from electronic noise sources. Commercially available SLA
is a self-contained system that includes a CAD system or interface directly connected to the user's CAD system 27-. A commercially available SLA like this
Systems are California, Valencia, 3D Sy
commercially available from Stems Inc.

In most radiation-absorbing materials, the amount of radiation absorbed is proportional to the amount of radiation present. This radiation dose is proportional to the transmitted intensity according to Beer's law. Beer's law is useful in explaining this process because it provides a good approximation of light absorption behavior, attenuation, etc. even in the presence of other mechanisms such as photobleaching. Even if the blotting materials do not obey Beer's law, the techniques of the present invention apply to these materials. Preferred embodiments use resin/wavelength combinations that closely follow Beer's law.

Many of the methods described in the invention are therefore based on the use of this law. However, it will be clear to those skilled in the art how to use the method of the invention with blotting materials that follow other rules.

FIG. 2 is a vertical cross-sectional view of a container of photopolymer 22 according to Beer's law. A monochromatic light beam 44 in the form of a beam of uniform intensity impinges on a spot 27 on the surface 23 of the photopolymer 22 . The intensity of light 44 is measured in watts/cm 2 or similar units. At the surface of the photopolymer 22, the light intensity has a value of zero. Each element of photopolymer 22 absorbs a portion of the light incident on it and transmits the other portion, except for a small amount that is scattered.

By the time ray 44 is partially transmitted to level 60,
The light intensity is reduced by a factor of 1/e.

Here e is the base of numbers for nature, which is about 2.7
Equal to 18. The intensity of ray 44 at level 48 is I
0, the intensity of the transmitted light ray 56 at level 60 is 1:O/e. The distance (distance from the surface 48 to the level 60) over which the light ray 44 is attenuated by a factor of 1/e is defined as the penetration depth Dp or 1 penetration depth (PD).

From level 60, a portion of the light ray 56 is transmitted down to level 70, and a portion is absorbed (for the sake of explanation, scattered light is ignored). The distance from level 60 to level Z6-70 is another PD. The intensity of the ray 56 reaching level 70 is therefore less than the intensity of the ray 56 reaching level 60 by a factor of 1/e.

Therefore, level 70 has two P below the photopolymer surface 23.
D, and has a light intensity of TO/e2. The introduction level 80 has 3PD below the surface 23 and the light intensity of the level 80 is I O/e'. In general, surface strength■
The strength ■ of the depth d below the surface 23 receiving 0 is ■(d
) = O/ed/Dp. Here Dp is the penetration depth and d/Dp is expressed by a specific PD number.

Therefore, for example, at a level of 2.3 PD below the surface 23, the light intensity is Q/e23=0/1.0.

The present invention applies to various penetration depths Dp in order to solve the problems and obtain other advantages described in the prior art and its problems.

Exposure (E) is defined as the amount of energy that impinges on the surface. Exposure is therefore measured as energy/area. A typical unit is joule/cm2. The photopolymer 22 transforms from a liquid state to a gel when exposed to sufficient ultraviolet light. The maximum/JX limit of exposure that results in a sufficient number of reactions to form a gel is called the critical exposure Ec. This critical exposure is the material,
Depends on wavelength etc. If the photopolymer 22 receives an exposure greater than Ec, the gelled material will further polymerize and become rigid until sufficient exposure is provided to terminate the polymerization process. Exposure does not result in complete polymerization, but absorption of a suitable dose of radiation from the light source causes polymerization within a portion of the photopolymer. Because the light beam 44 travels deeper into the photopolymer 22 and is attenuated, the upper levels experience greater light intensity and therefore greater exposure than the lower levels. Above this, the upper level gels first. For example, when level 60 receives Ec, lower level 70 receives an exposure approximately a factor of 3 below Ec. FIG. 3 shows that only material above level 60 undergoes at least EC, such that the photopolymer 22 above level 60 receives light 44 and converts to a gel in area 84, whereas the material below level 60 receives at least EC. Polymer 22 is light 44
Indicates a state in which a portion of the gel is exposed and not yet gelled.

Level 70 reaches Ec after the longer exposure rIR (approximately 27 times as long). The state at this time is illustrated in FIG. All material above level 70 exposed to light beam 44 has solidified from liquid to non-liquid. For example, area 86
is currently in a gel state. By this moment area 84 is Ec
It has undergone much greater exposure and therefore the photopolymer 22 in this area 84 has become harder and more condensable.

After a longer exposure (2.7x exposure) level 80 reaches Ec. This moment is shown in Figure 5. By the time of FIG. 5, the material above level 70 has been further exposed to light beam 44 and has hardened from a liquid state to a non-liquid state. For example, area 88 is gel-like. By this point, area 86 has received much more light (approximately 2.7 times) than Ec, and the photopolymer 22 in this area 86 has further polymerized, becoming harder and forming a more condensable mass. There is. By the time shown in FIG. 5, area 84 has received much more exposure than Ec, and the photopolymer 22 in area 84 has further polymerized into a harder, more condensable mass. In this way, the process of increasing the hardness and cure depth of the photopolymer by increasing the amount of exposure can be continued. In Figures 3, 4 and 5 above, there is a continuous polymerization gradient vertically through the gelling material. Different exposure amounts between levels 60 and 80 result in different cure depths. There is a minimum amount of exposure with a minimum condensation depth for a particular material/wavelength combination. In this example, this maximum depth is level 2.
It is considered to be between level 3 and level 60.

As mentioned above, the light intensity as a function of depth (d) below the surface 23 (in mils) is: I (d) = Q / e d /D p;
Here, IO is the intensity of the light ray 44 incident on the spot 27 on the surface 23 of FIG. 2, and Dp is the penetration depth PD measured with a mil.

Since the exposure E is proportional to the intensity (L), E (d
)=EO/e”Dp.

FIG. 6 is an "actuation curve" plotting critical exposure Ec as a function of depth below surface 23 and surface exposure EO.

In other words, FIG. 6 is a plot of cure depth versus exposure. As discussed with respect to FIGS. 3, 4, and 5, the critical exposure Ec just sufficient to gel the photopolymer 22 occurs only after the surface exposure EO becomes large. Reached deep within. This is because not all of the light rays 44 resulting in surface exposure EO are transmitted to the depths. In FIG. 6, the depth axis of the O mil below surface 23 is shown. In this example Ec is equal to 0.01 J/am2. Therefore, the actuation curve 90 intersects the EO axis at a point 92 resulting in a depth (d) equal to O and 0.01 J/cm2. Point 92 is the critical exposure of spot 27 in Figure 2, EC = 16 MJ/cm2.
It corresponds to the state after receiving it. At this point spot 27 begins to gel.

As previously mentioned, the light intensity (2) at the lower level will vary from application to application, depending on the absorption properties of the material chosen as the photopolymer 22, the wavelength of the incident light beam 44, etc. The critical exposure Ec also varies depending on the application.

The value of Ec depends on the resin used, the wavelength, and the (equilibrium) above the resin.
Depends on atmosphere, temperature, etc. Therefore, actuation curve 94 is only useful for certain applications.

In this actuation curve 94, point 96 indicates that the surface exposure EO is 2.
The depth at which the exposure becomes equal to the critical exposure Ec when increasing slightly above 56 M J / 0 m2 (in this case 2
1 mil). In this example, the depth of point 96 is 21 mils, which is, for example, level 80 of FIG.
corresponds to

In FIG. 6, the area 100 to the right of the actuation curve 94 is
This embodiment shows a combination of depth and surface exposure EO such that the actual exposure E is greater than Ec. In these combinations, photopolymer 22 is no longer a liquid.

Generally, the further away from the operating curve 94 in this region 100 the more polymerized and condensable the photopolymer 22 becomes.

For example, point 102 in FIG. 6 corresponds to area 84 near level 60 in FIG. The level 60 is shallower than the level 70 from the surface 23. Therefore, level 60 receives a greater amount of exposure E than level 70 after reaching a constant surface exposure EO. Point 96 is on the actuation curve (the point where level 80 just gelled), but point 102 is off the actuation curve 94 and level 60 is much more polymerized.

Opposite zone 100 is zone 104 to the left of actuation curve 94.
35- indicates the combination of depth and surface exposure EO such that the actual exposure E is less than Ec in this embodiment.

In this zone, the photopolymer 22 is still in liquid form.

The operating curve 94 is valid for a particular application, for a particular photopolymer exposed to a particular wavelength or wavefront combination, for the amount and type of gas absorbed into the resin, etc. . It is assumed that history (amount of light already absorbed) and light intensity do not affect the % absorption of the photopolymer. In practice, most materials obey this simple rule over a very wide range of exposures and light intensities (element volume fractions).

In many other cases where this rule is not followed exactly,
It provides an excellent approximation for the polymerization of this photopolymer and requires only very slight corrections.

If the actuation curve 94 moves to the right in FIG. 6, this means an application where the critical exposure Ec is large. Actuation curve 94
If the slope is steeper (larger Pd), this means that the photopolymer transmits more of the incident light rays 44. Conversely, if the slope of the actuation curve 94 is flat (low Pd), this would imply an application in which the photopolymer transmits less of the incident light ray 44 than the application of FIG.

Many advantages are obtained by allowing different values of penetration depth Dp using the system of the invention. this is,
Allows maximum speed of SLA operation, saves power, prevents distortion, facilitates obtaining desired resolution, limits crosshatch overcure, and increases cure depth uniformity. In a first preferred embodiment, different depths of penetration can be produced in the SLA by one or more radiation sources of different wavelengths. In a second preferred embodiment, different degrees of transmission can be created in the SLA by photopolymers of different transmission/absorption rates.

Since SLA is used to quickly reduce computer-aided designs to three-dimensional prototypes, speed of operation is an important goal. For a given critical exposure, greater depth of penetration increases speed. If the penetration depth is deep, a large portion of each layer is solidified with each pass of the laser beam. Also, if the penetration depth is deep for the same critical exposure, a rapid laser beam pass can be generated to harden a given point to a desired depth.

The importance of using a deep penetration depth to improve speed is that
In part, this is because increases in beam intensity/exposure result in relatively small increases in cure depth.

In other words, even if the exposure is doubled, (In 2) ・ (D
p) results in a change in hardening depth. Therefore, as long as the initial hardening depth dl is greater than (in 2) · (Dp), even if the surface exposure EO is doubled, the initial hardening depth dl will be less than twice the initial hardening depth dl.

Therefore, the use of deep cure depths is important for rapid increase in cure depth. For a constant critical exposure, a material with twice the penetration depth will reach a certain hardening depth faster by a factor of e(d/2Pd). A penetration depth (Dp) of about 30-40% of the desired layer thickness has been found to be adequate with respect to the rate and condensability of the layer formed.

For example, for a 20 mil thick layer, this corresponds to 5-7 mils of Pd. Table 2 below shows that layer thickness affects the rate of formation of three-dimensional parts. Table 2 shows the polymerization times reflecting the amount of surface exposure EO required to cure to a given layer thickness. Also shown is the surface coating time, that is, the preparation time for polymerization of each layer. Recoat is discussed in the '330 patent and co-pending U.S. Patent Application No. 249.399.
No. 1, and this is cited as an example. Essentially after each layer is completed, a new layer of liquid photopolymer 22 is recoated onto the surface 23 and the next three-dimensional component layer 30 is selectively cured. For example, in FIG. 1, after layer 30C is formed,
A new photopolymer N22 is coated on this j130c,
This layer 30c must then be selectively solidified to form layer 30b. Thin recoats require longer coating times than thicker recoats. This is because the photopolymer is viscous and requires time to spread, even with mechanical assistance, when the elevator is lowered by a thin layer thickness.

(Table 2) This Table 2 shows that 4 layers of 5 mil thickness require 5.5 times as much time as 2 layers of 10 mil thickness, mainly due to the 9-height time. It shows that. To produce a cure depth (in this case layer thickness) of 10 mils polymerization time is longer, but to produce a 5 mil thickness of 2N much greater coating time is required.

In the example of Table 2, one layer that is 5 mils thick requires the same amount of time as a 20 mil layer that is four times thicker.

If more material is to be polymerized in each layer, a thinner layer is advantageous if the minimum time to form a given thickness.

As the penetration depth increases, thicker layers are advantageous and thus the formation of three-dimensional parts is faster. However, the thicker the layer, the lower the resolution. The resolution of the three-dimensional part 30 is inversely proportional to the layer thickness. This is because thick layers result in inaccurate approximations for non-vertical design surfaces. For example, if you are designing a wheelchair to have a smooth slope, if you use multiple layers of resolution and each layer is 8 inches thick to approximate the design, the printed object will not be able to move up the stairs due to its low resolution. It becomes like this. However, multiple layers of 5 mil thickness will produce a very smooth gradient. Certain portions of three-dimensional parts may require greater resolution for a number of reasons (eg, due to intended mechanical interactions with other objects). Vertical surfaces of three-dimensional parts do not necessarily require thin layers. This is because, using any suitable layer thickness, the shape will be approximately the same (vertical). Similarly, a multi-step staircase 10 inches high can be made with 5 mil or 10 inch layers with equal precision. Three-dimensional parts consisting only of rough designs may have low resolution. That is, if platemaking speed is an important factor, resolution can be sacrificed for increased penetration depth.

The increase in penetration depth Dp is also limited by print-through. A scan batt that causes portions of the layer to undergo extra scanning will result in exposure errors in these areas. This exposure error results in a cure depth error. this is,
This can occur when SLA uses crosshatch traces of ultraviolet light to cure one layer of three-dimensional part 30. The features require a shallow penetration depth so that exposure errors result in only small variations in cure depth.

Exposure is determined by controlling the laser output (actually, the intensity (1) per unit area) and the drawing speed (time t per unit area). Currently commercially available SLAs are
Control exposure to within about 10% or better.

Intersections of the line double the exposure of other line parts. As mentioned earlier, doubling the exposure increases the hardening depth (In 2)
・Increases DP and height. Therefore, if the penetration depth increases, the print-through depth increases proportionately.

The user's print-through tolerance depends on the three-dimensional part being created.

Additionally, the user's tolerance for this overcuring varies from layer to layer and from layer to layer section. Even if the point of intersection is beyond the intended cure point, some overcure is allowed to adhere the layer to the underlying layer. Conversely, if the intersection is above the downward facing surface, the overcure will protrude beyond the desired downward facing profile.

As penetration depth increases, exposure (power or scan speed)
Errors in curing depth result from errors in curing depth.

In other words, a 4X penetration depth must be used to keep the print-through error within the desired range. For example, if formed from 10 mils (0,010") N, the actual cure depth can be 14 mils ± 1.5 mils. If the penetration depth is 3 mils (30% of layer thickness) Then, if the exposure is increased by a factor of e 2 = 1.65, the intended exposure increases the cure depth by 11.5 mils. It is relatively easy to control exposure within a 65% variation range and control cure depth within these limits. Against this 6
If using a penetration depth of mils, then to yield an extra depth of 1.5 mils as before, the exposure should be e"' = 1.2
It would be necessary to increase the size by eight times, which would make control work that much more difficult. In this case, the cure depth error is 1.5 mils, so the exposure needs to be controlled to within 28% error rather than within 65% error.

Over-curing is a major problem with respect to downward facing surfaces in the orientation when three-dimensional parts are being formed.

Control system 28 determines which portions are often overcured and reduces penetration depth.

42 Alternatively, the user can manually select an appropriate penetration depth.

Polymer hardness is another factor that limits penetration depth. In FIG. 5, area 84 has received several times more radiation than area 88, so by the time area 88 gels, area 88 is much more condensable (hardened).

This is because area 84 is at several times the DP than area 88.

If the penetration depth Dp were much first and the surface 23 was below the upper IDP of the level 80, the area 84 would be much less condensable compared to the area 88.

However, the "green" hardness of the partially cured part is related to the degree of polymerization of each unit volume. Green hardness can be considered as the sum of hardness of each unit volume. Therefore, the higher the degree of polymerization, the higher the green hardness. High green stiffness is extremely important for three-dimensional parts that are not well supported from below by other parts. If the top of the cantilevered layer is solid (
[If compressible], this provides great strain resistance. In a preferred embodiment, the controller 28 determines how stiff the top of each subsequent layer in the unsupported area must be to resist deflection due to gravity or distortion due to bending to adjust the depth of penetration. do. Once the resin resists bending, gravitational deflection, and tensile strain, the distance between the bending points (bottom or top) and the stiffness factor of each unit volume within this distance can be combined to calculate the resistance to the bending moment. It is preferable to measure the raw hardness of the three-dimensional part as the resistance force.

The cantilevered portions of three-dimensional part 30 may be further supported by other supports or inert materials, if desired. The user or controller 28 determines the need by considering the bending resistance (cantilever strength), the desired bending moment, and the desired degree of bending. The cantilever strength varies in proportion to the cube of the layer thickness. As mentioned above, the layer thickness and the desired degree of bending vary with the penetration depth Dp. The said support is
It can be a Watsuful grid that is cured but not an actual part of the three-dimensional part 30 and thus removed from the three-dimensional part. Regarding this support, co-pending Special Feature III 33
1, 664 and 182,801.

Alternatively, an inert material that is flowed around the three-dimensional part 30 supports the unsupported portions of the three-dimensional part 30. Preferred materials of this type are hot melt adhesives or waxes. Inert materials that are melted and then suitably solidified to support the required areas are generally not cured by ultraviolet light. A dispensing device can be provided to properly place (amount and location) this inert material.

Different light wavelengths have different absorption properties in a given polymer and therefore generally have different DP values.

Also, different photopolymers 22 generally have different penetration depth values Dp.

IV. A first preferred embodiment of the invention is an SLA with light sources generating different wavelengths. This light source actually consists of several different light sources, each of which generates one or more stimulating radiation wavelengths.

An important aspect of this embodiment is that different wavelengths of stimulating radiation generally result in different penetration depth values Dp within a given photopolymer 22.

This implementation is basically divided into two approaches.

The first approach consists in using two or more wavelengths simultaneously to solidify the resin. A second approach uses two or more wavelengths of stimulating radiation, but only one wavelength at a time in the curing process, with each wavelength having a different transmission into the resin used. 1 is a graph plotting the percentage of incident light absorbed at a given depth of a hypothetical photoinitiator versus wavelength λ in nanometers (nm); In general, a photopolymer is mainly composed of various monomers, contains a photopolymerization initiator, and also contains various other components. These other ingredients include light absorbers, inhibitors,
Contains fillers, etc. In many photopolymers, the main absorbing element is the photoinitiator. For convenience of explanation, it is assumed herein that the photoinitiator is the primary absorbing element in the resin (the analytical values are similar even if other elements contribute to light absorption). Photoinitiators are reactive elements capable of initiating polymerization reactions when exposed to stimulating radiation. Many monomers begin absorbing radiation at wavelengths much lower than about 300 nm. In the case of the hypothetical photoinitiator shown in FIG. 13, very much lJX% of light is absorbed at 290 nm. If a small percentage of the light is absorbed, most of the incident light ray 44 will be transmitted deep within the container 21. -However, many monomers absorb strongly at this wavelength, and this absorption causes transmission to a certain depth. Therefore 290n
Radiation with a wavelength of m is expected to have a shallow penetration depth through the photopolymer 22. In FIG. 13, the photopolymerization initiator alone exhibits absorption characteristics at a wavelength of 360 nm that are comparable to those at 290 nm. However, the monomers do not produce strong absorption, and the photopolymer as a whole appears to have a large penetration depth, ignoring the presence of additional components. However, at 325 nm, most of the incident light beam 44 is absorbed by the photoinitiator. This indicates a shallow penetration depth. In this example, the penetration depth varies continuously and rapidly within the wavelength range from 290 nm to 360 nm.

Lasers commonly used in stereolithography equipment are:
It is a helium-cadmium laser that produces a single wavelength or "line" at 325 nm.

However, embodiments of the invention are preferably argon ion lasers, which can generate laser radiation at a single wavelength or at several wavelengths simultaneously. - Argon ion lasers have higher output (light intensity) than conventionally used lasers. When operating in multiple wavelength mode, the power is distributed over several lines. When operating in this mode, the laser has a greater total power than when operating in any single wavelength mode, so the method of using all lines for polymerization has a power advantage.

FIG. 14 shows the respective operating curves for two wavelengths with different absorption/transmission depths and different critical exposures. λ
1 (e.g., 360 nm) is steeper than the actuation curve 302 at λ2 (e.g., 325 nm).

This indicates that at each level of the photopolymer 22, a smaller amount of λ1 is absorbed than λ2.

In other words, λ1 is transmitted more than λ2, so the transmittance is deeper.

When both wavelengths are present simultaneously, the effective operating curve is generally equal to each surface exposure E. For the operating curve 94 or 302
It is the deeper part of either. That is, the operating curve 9
4 and a portion 304 of the operating curve 302.

However, if the exposures from each wavelength are nearly identical, the resulting cure depth will be the accumulation of the two exposures and will increase somewhat.

This can be understood by considering that the difference between gels and liquids is based on different degrees of polymerization. The portion of the plot above each operating curve indicates that no polymerization occurred;
It only shows that insufficient polymerization occurred to form a gel. Therefore, if two or more wavelengths are used and the cure depth for each wavelength is approximately the same, it is believed that sufficient polymerization will occur to cause gelation to a depth greater than that produced by each wavelength alone. . This is especially true when the hardening depth due to the wavelength with greater penetration depth is shallower. This is indicated by the dashed area 305. As this graph shows, λ1 (radiation with low absorption and large penetration depth) takes precedence over λ2 in determining penetration depth after this area 305. All points 306 on the left side of both actuation curves represent uncured liquid. All points 1 to the right of each actuation curve, ie, area 308 or 100, represent solidified material. This 14th
The levels along the depth axis of the diagram are similar to those shown in FIG. The above description is based on equivalent light intensities and therefore equivalent exposures at a given time. If the intensities of the two beams are different, the cure depth induced by each wavelength cannot be read from the same vertical line. Since the two wavelengths are considered to be operating simultaneously, the exposure times will be the same, but if the light intensities are different, the exposure times will be different. The cure depth for each line must be read from the operating curve at the effective exposure that occurs for that line. Please refer to the table below to explain these points. This table shows that, in conjunction with the actuation curve of FIG. 14, different relative strengths affect cure depth.

1- (Original p. 40 table) 917- This table shows four important points regarding cure depth.

1) Curing depth depends on the wavelength used. 2) When multiple wavelengths are used, the cure depth depends on the intensity ratio. 3) The cure depth depends on the critical energy for each wavelength. and 4) the depth of cure depends on the desired depth of cure. The table above does not indicate the net cure depth obtained by the combined exposures. As previously explained, when both cure depths are approximate, the combination results in a net cure depth.

FIG. 15 is a cross-sectional view of the photopolymer 22 taken at the same time as FIG. 5, but in this case two wavelengths λ1 and λ2 are used, each wavelength having a different penetration depth. They also each have the same output/light intensity, resulting in the same exposure at a given time. Instead of the light 44 in Figure 5,
A light beam 320 is incident on surface 23. Light beam 320 is generated by two lasers producing wavelengths λ1 and λ2 of equal intensity. As discussed with respect to FIG. 14, λ1 is dominant in the cure depth and is the envelope of the point at the boundary between the liquid and non-liquid areas. The hardness of sections 84 and 86 of three-dimensional part 30 is increased by the wavelength λ2 that is hardened to the middle of section 86. −
The area thus affected consists of three areas. That is, the region 314.316.318° region 318 is the deepest,
Although the least cured of the three regions, it is still more condensable than the material solidified by λ1 in this area 86. This is because region 318 absorbed more rays 320 per single volume. Region 316 is surface 23
Since this is the second region, it is harder than region 318.

Region 314 is much harder because it receives a higher light dose per unit volume than the other regions.

If FIG. 15 shows a single-layer three-dimensional part 30, this layer has areas (regions 314, 316,
318) Much harder, but relatively soft for most others up to level 80. In this case, the wavelengths λ2 and 53
− Without its shallow penetration depth, such a hard zone would not exist. Without the wavelength λ1 and its deep penetration depth, this layer would have been cured only very close to the surface 481 and would have required an excessively long time to cure to the desired level 80.

Therefore, it can be seen that the combination of each wavelength and its corresponding penetration depth produced effective characteristics.

This first preferred embodiment, as seen in its two main approaches, takes advantage of such dual (multiple) penetration depths to form hard or very hard shallow areas near the surface to while producing a "green" hardness, the long penetration depth can be used to quickly form relatively soft areas at deeper depths (low degree of polymerization, but still condensable and short formation times). area).

In the embodiment illustrated in FIGS. 14 and 15, the wavelength λ1
and λ2 are each treated separately to determine the cure depth. This is possible due to a combination of the following two or three factors.

1) λ1 has a much deeper penetration depth than λ2 4- Ru.

2) The relative light intensities are the same.

3) The total exposure is much larger than each critical exposure.

However, this is not always possible. Different three-dimensional parts have similar penetration depths for the two wavelengths, the relative light intensities are mismatched, or the exposure required to obtain the desired cure depth is critical for both wavelengths. It may not be much larger than the exposure.

Therefore, the net cure depth cannot be determined by considering each wavelength separately. As mentioned above, if a given photopolymer has similar penetration depths for two or more wavelengths and the light intensity corresponding to each wavelength is similar, the cumulative effect will increase the cure depth. You will have to consider it as a decision.

To experimentally obtain the curing depth of a single wavelength or the cumulative curing depth of multiple wavelengths emitted by the laser simultaneously,
You can use "Panjiyou Top". A puncture top is a series of strings hardened to different depths by different exposures.

FIG. 16b is a plan view of the punch top 330. First, frame 332 of the punch top is formed by deeply curing a rectangular profile on surface 23.

FIG. 16a is a perspective view looking down in the direction of ray 320 of FIG. 15. FIG.

Next, ray 320 traverses passageway 334 with very low surface exposure EO, condensing string 336 transversely to frame 332 .

As shown in FIG. 6 or FIG. 14, multiple strings are formed to plot the actuation curves. aisle 3
38 by a slightly larger exposure, for example 2Eo. This forms string 340 which is slightly wider and deeper than string 336. Passage 342 is traversed with a slightly larger exposure, for example 4Eo. This is stopper ring 3
A string 344 slightly wider and deeper than 40 is formed. Two further channels and a plastic hardening strip are shown but not numbered.

Finally, the top 330 is removed from the photopolymer 22, and Figure 16b is a side view taken along line 16b--16b of Figure 16a. Therefore, if a transparent material is used as the frame 332, the string 3 can be passed through the frame.
36, string 340 and string 344 and two strings without numbers are visible and can be measured from the side. Alternatively, the depth d can be measured using a caliper, a micrometer, a measuring microscope, etc., or if necessary, the punch top 330 can be cut open to get closer to the string. From the string depth d obtained from a known surface exposure, for at least two strings simultaneously, the formula E c = E o / e
By solving ``'', the penetration depth and critical exposure Ec can be obtained. An indirect way to solve the above equation for strings is to solve the surface 1i I! The actuation curve is formed by plotting the cure depth d against the logarithm of BE o. We plot case depth against the logarithm of exposure because our theory (Beer's law) predicts a linear increase in d with a logarithmic increase in E. This operating curve takes the following form: Case depth = d = Pd - Ln (E) o constant where the slope is the penetration depth and the constant is the natural logarithm of penetration depth x Ec.

The above description of Panjiyou Top has been made to illustrate a few basic characteristics. Similarly, FIGS. 2, 3, 4, 5, and 15 are illustrated to show certain features. These descriptions assumed the use of a uniformly intense light beam. That is, the output per unit area of the cross section of the beam was assumed to be constant. However, the beams used in actual stereolithographic techniques generally do not have such a uniform power distribution. There may be variations in light intensity in the radius of the beam. These variations generally result in non-uniform strings of polymerized material. Generally, the centerline of a string of cured plastic is thicker than the edges, and the width of the plastic string decreases from the top surface of the three-dimensional part to the point of maximum cure depth. In other words, to predict the hardening depth of a plastic string,
Average exposure -b'/- maximum exposure rather than exposure (if the beam is scanned).

The light source 26 may vary in light intensity after or during the formation of the three-dimensional part 30. Therefore, the light intensity (power per unit area) must be checked before forming each new three-dimensional part, or before each step of forming a new three-dimensional part. In practice, since the beam is used to expose the photopolymer during its scan, it is desirable to know the integrated firing light intensity along the scan axis. This light intensity check is carried out in co-pending patent applications S, N, 3.
31,664, by a beam profiler using a raw data file containing top information along with the beam power at the time the beam was generated. Lasers generally lose power and optical intensity during their lifetime. In single wavelength SLA, -58 = loss of power and light intensity can be reduced by creating a punch top and/or by using a beam profiler when the laser power or light intensity varies significantly. It can be considered. In a multi-line SLA, the above technique can be used as long as the power loss is not proportionally the same for each line. If the output variation is proportional, punch-top test parts must be made more frequently.

Since the power loss may not be the same for each wavelength, if you want to know the cure depth and other cure characteristics,
Each wavelength must be profiled separately. A preferred system for measuring the light intensity of each wavelength consists in filtering all but one line each time. This is carried out, for example, by placing a movable filter in the beam width between the light source and the scanning mirror. Another approach consists in using one or more beam profilers with multiple optical sensors, each with a different narrow band pass filter on each optical sensor corresponding to each line wavelength. If the required parameters of the resin are known, different curing parameters can be determined for each wavelength once the light intensity profile for each wavelength is created. Once these curing parameters have been calculated, it can further be determined which wavelengths and corresponding light intensities should be used in the curing process. Controlling which wavelengths and their relative intensities are used can be performed automatically by various approaches. One possible approach consists in using various filters to receive the beam and attenuate the output corresponding to specific wavelengths. Furthermore, the degree of attenuation achieved by these filters can be varied by designing filters of different opacity, depending on how far the filter is inserted into the beam path.

Alternatively, circular filters can be used that range from O attenuation to very high attenuation for specific wavelengths depending on the angular orientation of the filter. As an additional example, another approach consists in using separate controllable light sources for each wavelength and combining the different beams. These various approaches can be controlled directly by the control system 28 with or without an operator. On the other hand, if the resin balun = 61 is not known, a punch top or other similar part will need to be fabricated, and other experiments can be performed to determine additional resin parameters.

Panjiyo top measurement can be automated. For example, a robot can pick up a punch top from where it was formed, spray or dip a solvent onto it, wash off excess resin, and then post-cure it. , and then its thickness is measured by mechanical, electrical or optical means. However, this is a complex process. A more preferred approach is to use beam profile information in conjunction with specific resin properties to make all necessary measurements. This is one of the objectives of the invention.

First approach of first embodiment (simultaneous use of multiple wavelengths)
There are a few preferred methods.

1) Use of equilibrium resins with or without equilibrium efficiency;
2) a method that does not control the radiation but uses the planned output completely, and 3) control of the radiation source.

The first method of the first embodiment described above allows multiple wavelengths to be used simultaneously with the simplicity of a single wavelength approach.

Instead of measuring the output of each wavelength separately to account for the light intensity of each wavelength, the photopolymer is carefully selected. For example, the same penetration depth (and the same critical exposure and polymer formation efficiency) for each wavelength at which a photopolymer is used.
, then changes in the relative power (total light intensity) of different wavelengths do not affect the curing properties. This method does not produce a very intense zone near the surface and a weak (quick) zone below, but it allows the use of the full power of the laser at multiple wavelengths and reduces the power loss of each of the multiline radiation sources. No need to measure.

One way to obtain the same depth of penetration for each wavelength is to choose a photopolymer that has the same absorption for all wavelengths used. For example, in FIG. 13, if the laser emits at 290 nm and 360 nm, the photoinitiator shown in the graph has the same absorption at both these wavelengths.

Therefore, ignoring sorption by monomers and other components, both wavelengths are considered to have the same penetration depth into the initiator and photopolymer. Similarly, the light source (
2b) emits radiation of the wavelengths A and B shown in the figure, it can be assumed that both have the same penetration depth.

FIG. 17 is a block diagram showing typical chemical reactions in SLA. The liquids used in commercially available SLAs generally polymerize in response to ultraviolet light due to the presence of UV-sensitive photoinitiators. Photoinitiator 350 splits into free radicals 352 in response to ultraviolet light exposure. This free radical 352 initiates a chemical reaction between monomer molecules 354 to convert it into polymer 356.

After further exposure and blotting, more monomer 354 is added to polymer 356. When sufficient density of polymer 356 occurs, gel 358 forms. Upon further polymerization, gel 358 fully polymerizes to form plastic 360.

FIG. 18 is an absorption/wavelength graph of a photopolymer containing a plurality of photopolymerization initiators that exhibit different differential absorptions depending on the wavelength. The amount of each photoinitiator is adjusted until the penetration depth is the same for each wavelength. While the absorption characteristics of a particular photoinitiator determine the overall shape of the graph of FIG. 18, the warpage concentration determines the amount of absorption and penetration depth at each wavelength. Increasing the amount of photopolymerization initiator is 11S! This means an increase in the amount, ie the high curve in FIG. 18. curve 3
70 is the first type of photoinitiator having maximum absorption at λ3. Curve 372 is a second type of photoinitiator that exhibits maximum absorption at λ4. The cumulative effect when these two photoinitiators are combined into a single resin is curve 3
74. Curve 374 is relatively flat between λ3 and λ4, indicating that intermediate wavelengths have similar absorption as λ3 and λ4.

Multi-line lasers with wavelengths between 13 and λ4 can therefore be used to maintain a single uniform penetration depth.

The resin requires careful "tuning" to produce the same penetration depth for each line. Commercially available argon-ion lasers can be configured to generate radiation in the ultraviolet range at various single wavelengths or at multiple wavelengths simultaneously. The main UV lines for argon lasers are approximately 364 nm, 351 nm, and 334 nm, among others. The lasers are 364nm line and 351nm line respectively.
It can be set to emit simultaneously at all these wavelengths with approximately 40%, 40% and 20% power for lines and 334 nm lines/other lines, respectively. The laser can also be suitably tuned to emit with other powers for each wavelength. In the most preferred mode the laser delivers 480% and 4% of the total beam power for the 364nm line, 351nm line and 334nm line/other lines, respectively.
Adjusted to have 8% and 4% output. The relative energies of these other wavelengths are so low that they do not substantially contribute to the curing parameters obtained by radiation of this beam. That is, mainly 2
A beam with two penetration depths is obtained. This beam is the preferred beam by all multi-wavelength embodiments. Preferred equilibrium resins for the formation of 355-dimensional parts include 49 parts acrylic acid adduct to bisphenol A diglycidyl ether (Novacure 63700), 2-phenoxyethyl acrylate (Sartomer O33)
9) 5 parts, trimethylolpropane trimethacrylate)
(Sartomer@-350) 12 parts and ethoxylate bisphenol A (Sartomer@
348) and 25 parts of dimethyl acrylate (Luciri
n@TPO) and 2.68 parts of 1-hydroxycyclohexylphenyl ketone. (Parts are parts by weight) This composition shows the same absorption for 351 nm and 364 nm wavelength argon-laser radiation [1 m
Optical density 1 g (IO/
I)] This resin composition has excellent sensitivity for printing three-dimensional objects by stereolithographic techniques (24 mJ/
depth 0,3m by radiation with energy of cm2
m polymerization occurs).

Various types of photoinitiators can generate light energy (e.g. one photon).
These photoinitiators are capable of producing varying amounts of photopolymerization. The efficiency of a photoinitiator/monopolymer combination is related to its ability to form chemical bonds in response to absorbed photons.

If the two photoinitiators have different efficiencies, the same amount (or the same percentage) of light absorbed (same - penetration depth) will result in different cure depths. Therefore, the photopolymer of this embodiment must be balanced not only for depth of penetration (% absorption) but also for efficiency with absorption.

Figure 19a is an absorption/wavelength graph of two other photoinitiators. Figures 19a to 19g show how to consider efficiency. Curve 380 is the appropriate concentration of photoinitiator that absorbs a constant percentage of light at peak absorption wavelength λ5. Curve 382 shows the appropriate concentration of the fourth photoinitiator absorbing the same percentage of light at peak absorption wavelength λ7. This light percentage is Pl in Figure 19a.
Indicated by 'yl' qL. These two wavelengths (λ5 and λ
7) have the same absorption rate and therefore the same penetration depth. However, if the first photoinitiator has a higher efficiency than the second photoinitiator, the first photoinitiator will exhibit a higher efficiency in polymerization. In other words, λ5 produces a higher degree of polymerization than λ7 for a given exposure and therefore exhibits a higher cure depth. The first photoinitiator has the efficiency shown in curve 386 in Figure 19b, while the fourth photoinitiator 382 has the efficiency shown in curve 388 of Figure 19b.

When considering efficiency differences, Figure 19 shows that for a given exposure, λ5 produces more polymer (EFI) than λ7 produces (EF2). To obtain the same cure depth for these wavelengths, the effectiveness as well as the absorption must be equalized.

This is achieved by lowering the concentration of the first photoinitiator and by lowering the concentration of the first photoinitiator.
This can be done by reducing the height of 0.386 to the curves 390.396 shown in Figures 19c and 19d, respectively. However, in this case, the absorption rates (penetration depths) of the two types of photopolymerization initiators do not match. Therefore, in order to match these absorption rates, a portion of the incident light must be absorbed so as not to contribute to polymerization. For example, a light absorber can be added to the resin containing the first photopolymerization initiator. The light absorber is λ5
is selected to absorb (or block) light near the .

Its absorption capacity is illustrated by curve 398 in Figure 19e. By adding curve 398 and curve 390, we get the 19th curve.
form a curve 380 at least at λ5 in the f diagram (
(same as curve 380 in Figure 19a). When the light absorber is added until the first photoinitiator is able to absorb the incident light dose shown by curve 380 in Figures 19f and 19d, λ5 becomes λ7 in curve 388 in Figures 19d.
, and the same efficiency EFI as curve 396 of FIG. 19d, and the same penetration depth as FIG. 19f. In this way, the efficiency completely matched that of Pd, as shown in FIG. 19g. As a result, Figures 19h and 19I
A resin that can be used at any wavelength as shown in the figure is obtained. The equilibrium approach is similar, although more than one photoinitiator, light absorber, and other elements are required to achieve the desired equilibrium state.

For multi-line visible light lasers, similar materials could be made and used that yield the same efficiency and absorption capacity for any wavelength of visible light. However, this type of material cures in response to visible light, so appropriate precautions must be taken. Such precautions include shielding the SLA and live volume from irritating visible radiation or removing such radiation from visible light.

A second method of the first approach consists in using the predicted output to aid part formation while using multiple stimulating wavelengths. This method consists in using beam profile characteristics corresponding to each wavelength and known resin parameters to predict various forming and curing parameters. Such predictions/decisions are mainly made for the following three purposes. 1) determining whether the desired object can be made using currently available multi-wavelength radiation sources; 2) determining what forming parameters should be used initially; and 3) forming the object, if necessary. Determining the exposure parameters that will be used in the future. These various predictions include case depth, case width, green hardness, and others. The most important predictive parameter is green hardness. Because this method uses multiple wavelengths and the light intensity of these wavelengths is not controlled, it is possible to obtain a wide range of green hardness for a given volume of plastic depending on the exact wavelength and depth of penetration. . The determination of green hardness is therefore of paramount importance in determining what forming parameters are most appropriate for forming three-dimensional parts. For example, for some energy/wavelength combinations the lack of green hardness makes it impossible to form a separate 5 mil layer, while for other combinations the green hardness is 5.
The formation of a 20 mil layer is sufficient, and the penetration depth of the dominant wavelength is small, so it may be difficult to form a 20 mil layer.

The prediction and subsequent determination of the best formation parameters of this method may also be performed for other implementations, but we limit the prediction and determination possibilities as a minimal approach to automated use of multiple wavelengths.

A preferred third method of the first major approach may or may not include all aspects of the second method, but is designed to obtain constant wavelengths and light intensities or at least light intensity ratios of each wavelength. including the ability to control radiation sources. The controlled radiation dose for each wavelength, the various penetration depths obtained in this method, and the combination of predictability and determinability make this method a preferred choice for the simultaneous use of multiple wavelength approaches. This is an embodiment.

The third of the first major approaches considers multiple penetration depths, typically using shallow penetration depths near the surface to form hard or extremely hard hardened zones resulting in extreme green hardness, and deep There is an advantage in utilizing hardening depth to generally form deep soft zones per unit volume rapidly and in a short period of time. The green three-dimensional part 30 is harder than if it were formed with only a single wavelength and has a correspondingly greater penetration depth in a given liquid. By using one wavelength for shallow cure depth and another wavelength for deep gelation, the time required to form a durable three-dimensional part that lasts through formation and post-cure. is shortened. This is advantageous because polymerization is faster and cheaper in the post hardening equipment than in SLA.

The post-cure process is rapid because the entire part is fully exposed to ultraviolet light rather than being polymerized one section at a time. Also, the reason for the post-curing process is that the light source is not a hardening UV laser but an inexpensive fluorescent lamp.

The third method reduces the bending effect as described in [Prior Art and Problems]. There are at least two reasons for this. 1st
The reason for this is that the increased green hardness creates hard areas that resist the moments associated with bending. The second reason is that the soft areas absorb stress from enforcement while the hard areas retain their shape. The soft zone acts as a stress relief ensuring adequate adhesion and limits the transmission of internal stresses. These internal stresses can induce strain when they reach a certain level.

Controlling the properties of three-dimensional parts, from the rapid formation of very soft parts to the very slow formation of very hard parts, depending on the energy ratio of the two or more wavelengths used. I can do it. With such a wide range of properties, different hardness ratios can be varied in one layer from another, and can be varied in the thickness of each layer, and in the construction of specific areas. It can be varied depending on whether hardness or speed is more important.

Such an approach presents many advantages that will be obvious to those skilled in the art.

A specific embodiment of this method is described with respect to FIG.

If we use the two wavelengths of Figure 14 and have comparable light intensities and power for both wavelengths, these wavelengths can be used to cure very thin layers, forming layers of about 4 or 5 mils or less. For thickness, a very shallow penetration depth or a penetration depth of 2 mils could be produced. Exposures below Ecl cannot cause significant polymerization. On the other hand, deep curing depth (
Therefore, if a thick layer is to be obtained, Ec2 and its corresponding penetration depth are dominant, resulting in rapid curing of the desired thickness. Also in this case, areas of much harder solidified material are formed to enhance green hardness. As previously mentioned, for thin layers, a small penetration depth is desirable, resulting in superior hardness, which can minimize print-through problems due to exposure errors. For thicker layers, on the other hand, a high penetration depth is obtained in order to obtain an adequate curing rate. Even with the use of high cure depths, the hardness of the three-dimensional part is still sufficient because a large amount of material is cured.

Since the critical exposure for wavelengths with small penetration depths is lower than the critical exposure for wavelengths with high penetration depths, a proper relationship between penetration depth and layer thickness can be automatically obtained (at least if it is possible). be). As a result, exposure errors result in changes in cure depth that are proportional to layer thickness. This method of making the cure depth error proportional to layer thickness extends to three or more wavelengths as long as the critical exposure and penetration depth follow the same pattern.

The preferred approach described above uses multiple lines simultaneously. In this second major approach, lines are each used singly.

This embodiment works on a similar principle to that described above, with each line having its own depth. Light beams of different wavelengths are selectively emitted onto the photopolymer 22 in several ways as described below. 1) Selectively obtain wavelengths from a multiline laser by transient or other methods. 2) selectively reflecting multiple laser beams, each having a different wavelength, onto the surface 23 by a rotating mirror; 3) A method of switching a single line laser by changing the angle of a prismatic refractive reflector in the laser's lasing cavity, and similar methods to obtain selectable wavelengths.

4) Appropriate use of other multi-line radiation sources or single-line sources.

First, a multi-line laser is used similar to the preferred embodiment described above, but with the addition of a filter. These filters block certain lines leaving one or more selected lines behind. Preferably multiple filters are used, each filter blocking a single line.

These filters are mechanically moved into and out of the laser beam by a control system in response to exposure commands. Alternatively, these filters may be stationary and the 7-fu multiline laser beam may be selectively reflected through one or more filters with movable mirrors.

Such filter systems are also used for simultaneous multi-line curing to measure differential power variations.

One line at a time is directed into the beam profiler to measure the light intensity at each wavelength.

Second, multiple lasers are used to generate multiple lines. In order to narrow the line, the reflector is the light source 2.
6 to a position where it reflects other adjacent light sources of different wavelengths. The reflector reflects the selected line onto the surface 23.

Third, laser beam 44 is selectively modified to have a selected wavelength.

The main advantage of line selection is the ability to select the depth of penetration. This presents many advantages as also described in this chapter under "Penetration Depth".

Line selection is a very efficient method of selecting penetration depth. This can be done manually or by control system 28. Each of the above three examples of wavelength selection was performed very quickly and without major interruptions. The position of the spot on the liquid surface may change or increase if the beam is moved due to the need to pass through a filter or due to misalignment as the beams from different lasers or light sources are moved into the passage. The offset is corrected by the offset correction technique described in previously referenced US Pat. No. 268,907. This allows the penetration depth to be selected from three-dimensional part to three-dimensional part, from layer to layer, and from part to part of the same layer, as described in the previous chapter regarding penetration depth.

Each of the above embodiments can be combined to allow the user or control system 28 to select one or more lines. When multiple lines are selected to use multiple penetration depths simultaneously, SLA can gain benefits such as increased efficiency, increased green hardness, and reduced bending. If a single line is selected to vary the penetration depth, the SLA can gain the advantages described in "Penetration Depth", such as maximum speed and accuracy. All of the above advantages are obtained when combined into a single three-dimensional part.

In addition to the various approaches described above for obtaining different wavelengths singly, and in addition to the methods and advantages of using multiple wavelengths singly as described in the ``Penetration Depth'' chapter, multiple wavelengths used singly. The main usage of is described below: 1)
Different wavelengths are used for different layer thicknesses. 2)
Use different wavelengths for maximum speed. 3) Using different wavelengths for maximum hardness. 4) Bending to maximum IJ
Different wavelengths are used to reach the X limit. 5) Multipath with different wavelengths. The first four of these approaches have been described above and require no further explanation. However, the fifth approach has not yet been described, so it will be described here. This fifth technology is disclosed in U.S. Patent No. 339.
, 246. This patent application has been cited earlier in this patent application. The first multiplex approach consisted of multiple scans for each vector. However, the same wavelength was used for each pass. The first pass mostly solidified the layer thickness of material, but it did not actually solidify and therefore did not adhere to the underlying layer. The first pass was followed by one or more additional passes such that at least the last pass produced adhesion and thus the cure depth reached the desired final overcure depth. The purpose of the first pass was twofold. First, the material in the first pass cures without adhering to the underlying layer and can shrink without applying a bending moment to the underlying layer during curing. Second, the material cured during the first pass acts to resist the upward bending moment as the sandwiched underlying layer solidifies. Multipass was shown to be reasonably effective in minimizing bending. However, if the material hardness during the first pass increases significantly and/or reaches a high degree of polymerization and does not exhibit a tendency to further harden and shrink with the sandwiching material layer upon continued exposure, the multilayer The effectiveness of the pass is greatly increased. This high degree of polymerization and hardness is due to the first
This is accomplished by using low penetration depth wavelengths in the passes and curing the first or subsequent passes as close to the layer thickness as possible without causing adhesion. Subsequent passes or passes are then switched to deeper penetration depths to cause adhesion.

The drawing speed of each pass, the number of short Pd passes before adhesion, and the number of long Pd passes that cause adhesion can be varied. Also, multiple wavelengths and corresponding penetration depths can be used in this approach to balance the reduction in bending with the reduction in required scan time. Typically, the penetration depth for forming a medium hard layer is about 30% of the layer thickness.
It is 40%.

Perhaps a penetration depth in the range of about 15% to 25% of the layer thickness is adequate for short PD exposures, but 30% to 4
A penetration depth in the range of 0% or more may be sufficient for exposure to produce adhesion. Because of the bird beam formation problem that occurs when using multipass, see US Patent Application No. 183,015, which uses Smaley to minimize this problem. This patent application is cited as a reference. No. 182,800 also discloses the use of webs or other supports to minimize distortions including this bird's nest problem.
Please refer to No. 1. Use this as an example.

Most of the embodiments described in this chapter relate to the case where curing is carried out by a radiation beam, in particular by an ultraviolet beam. The radiation beam covers a wide range of the electromagnetic spectrum (e.g. infrared, visible, ultraviolet and x-rays)
or a beam of various particles (electrons), as long as the material has a reactive element that absorbs the radiation, this absorption causing a reaction and converting the material from a liquid state to a condensed state. In many embodiments and approaches of the present invention, multiple (at least two) penetration depths need to be considered since such absorption is wavelength dependent and energy dependent. When using a radiation beam, the light intensity profile of this beam is needed to predict the curing parameters. However, when each cross section is exposed using a radiation flood radiation source with a desired cross-sectional pattern having uniform light intensity, such profile dependence can be eliminated. This uniform radiation flood can have similar desired properties in terms of wavelength, penetration depth and relative power as previously described for the beam approach. This uniform flood is similar to the 1575
It can be generated from a short-arc mercury vapor lamp, as described in the patent, or from a xenon-type arc lamp, or from a variety of other light sources or combinations of light sources. - The radiation source includes a diffusing element to ensure uniform exposure of the entire surface. There are also several light intensity monitoring devices (cured material one device for each wavelength used to Also included are various filters inserted into the radiation path to remove specific wavelengths from the beam and/or to attenuate the light intensity corresponding to each wavelength to some extent. Devices such as refractive gratings or prisms can be used to sort desirable wavelengths from undesirable wavelengths. Additionally, various elements can be used to produce the desired cross-sectional pattern of radiation.

For illustrative purposes, some of the embodiments included in this chapter are summarized below. The preferred embodiments described above fall into the following two categories. 1) embodiments that use multiple wavelengths simultaneously; and 2) embodiments that use multiple wavelengths non-simultaneously. This first category includes the embodiments described below.

1) Equilibrium resin - penetration depth only, 2) Equilibrium resin - penetration depth and efficiency, 3) Multiple wavelengths with uncontrolled but predicted properties (
4) multiple wavelengths with controlled properties; a) to obtain superior speed and stiffness; and b) to minimize bending.

All of these approaches use beam profile prediction and control to some degree. To take full advantage of the beam's profiling capabilities, predictions are based on a superposition of exposures at each wavelength. For example, the cure depth is based on a measured average of critical exposures, but the total exposure is derived from all existing wavelengths.

Alternatively, the cure depth can be defined from the polymerization percentage required for gelation and the polymerization percentage determined by each wavelength. There are three levels of making these predictions using multiple wavelengths. Namely: 1) O order, in which case a prediction is performed for each wavelength and a net prediction is selected from the list. (Main Prediction = Net Prediction) - 12) A simple hypothesis is made regarding the degree of interaction of the effects of each wavelength to produce a first order, in this case a net prediction. and 3
) of the second order, in this case performing detailed calculations on the degree of polymerization caused by each wavelength, taking into account the interaction between the wavelengths, and then combining the results to obtain a net prediction. In this method,
Depending on the situation, some predictions are of O order, some of them are of first order, and some of them are of second order.

The second category includes the following embodiments.

1) different wavelengths selected for different layer thicknesses based on best overall properties; 2) different wavelengths selected for maximum velocity; 3) different wavelengths selected for maximum intensity; 4) minimum. 5) using multipath techniques, tfi p
d, a first pass is performed to achieve a high degree of polymerization without adhesion to the underlying layer, and then a second or subsequent pass is performed to create adhesion.

6) Using different wavelengths chosen to prioritize other arbitrary properties.

Each selected wavelength can be obtained by filtering, by switching the wavelength of lasers, by switching from one laser to another, and by using other types of radiation sources.

(2) A second embodiment with varying penetration depths in SLA involves changing the photopolymer 22. Different photopolymers have different penetration depths for a given wavelength. If different penetration depths are desired, other photopolymers may be used in place of photopolymer 22.

Alternatively, the photopolymer 22 may be left as is and processed.

Figure 20 shows a second embodiment in which the photopolymer 22 is replaced. Container 21 contains photopolymer 22 as described above. The selection of the penetration depth is carried out by the user or the control system 28 according to the principles described in the previous section "Penetration Depth". When another penetration depth is selected, the elevator 29 is raised in the Z direction until it is above the top of the container 21.

Co-pending patent application No. 249,399 and PCT, EP○
As described in Patent Application No. 188/189, three-dimensional parts 3
After overflowing the liquid onto the doctor blade 41
0 to cut off the photopolymer 22 to the surface 23.

In the conventional SLA, the doctor blade 410 was fixed to the container 21. This becomes a hindrance to replacing the container 21. However, in the present invention, the doctor blade 410 is attached to the frame of the SLA, to which the elevator 29 is also attached. This simplifies replacement of the container 21.

The container 21 is temporarily below the elevator 29 and collects the droplets of photopolymer 22 that fall from this elevator 29.

Optionally, the three-dimensional part 30 can be immersed in a photopolymer bath to remove excess resin adhering to the three-dimensional part from the container 21.
remove from

Container 21 has wheels 412 and 414. This container 21 is moved by rolling. A container 421 holding another photopolymer 422 rolls below the elevator 29 in place of the container 21 . - The photopolymer 422 has a selected penetration depth. When elevator 29 is lowered into 421,
The three-dimensional part 30 is covered with a photopolymerized resin 422, and the three-dimensional part is placed one layer thickness below the surface 423. Doctor blade 410 chips away photopolymer 422 to level 423.

The three-dimensional component 30 is installed in the elevator 2 while the container 21 is being replaced.
9 remains attached. Since layer 30d was formed last, the next layer of the three-dimensional part can be formed on surface 423 of photopolymer 422. container 2
1 and container 421 is a quick and easy way to replace photopolymer 22 if a different penetration depth is desired.

FIG. 21 shows another system for replacing photopolymer 22 with another photopolymer 422. FIG. If another penetration depth is desired,
A pump 440 pumps the photopolymer 22 from the container 21 and sends it through a hose 442 into a holding tank 44.

Pump 444 then pumps another photopolymer 422 from holding tank 448 through hose 452 to container 21.
send to This photopolymer replacement system can be easily controlled by a computer controlled by control system 258 to obtain different penetration depths.

FIG. 22 shows another system for replacing the photopolymer 22. This system does not replace the photopolymer 22, but processes it to provide a different penetration depth.

A given photopolymer 22 can be modified to have a different value of Dp. For example, if a photoinitiator is added to the photopolymer 22, the amount 44 of light absorbed at each level of the photopolymer 22 will increase and the Dp value will decrease. If a shallow penetration depth is desired, the photoinitiator tank 4
62, a photopolymerization initiator 350 is added to the container 21. If a deep penetration depth is desired, the resin tank 464
66 is added to container 21 to reduce the concentration of photoinitiator 350.

Below is a summary of embodiments that vary materials.

1) similar to the embodiments using multiple wavelengths described above; 2) resin switching between stages of forming the three-dimensional part; 3) resin switching during the formation of the three-dimensional part; a) without stripping the three-dimensional part; b) when stripping three-dimensional parts; 4) adding other elements to the resin.

A beam profiler can be used with each resin parameter file (one file for each resin).

Vl, Beam Profile Other features of the invention are implemented for each of the embodiments described above. That is, beam profile information is used in conjunction with resin parameters to predict curing parameters. Generally, the profile or cross-sectional light intensity of a laser beam is not constant. This is true even when the beam is focused to a small spot, as is done in the practice of standard stereolithography techniques. For example, in a laser beam, the light intensity is highest at the center and decreases as the distance from the center increases.

Taking into account the profile characteristics of the beam, along with various resin parameters, enhances various properties of the embodiments described above and produces additional advantages of these embodiments, and is therefore necessary. Furthermore, the combination of beam profile information and various resin parameters can also be used to
is a powerful means to automate single wavelength approaches.

Beam profiling is simultaneous! ltS,
N.

No. 268.816. This patent application is a partial continuation of the present patent application. This cited patent application is added as a reference.

FIG. 7 shows the beam light intensity (beam profile) inside the spot 27 on the surface 23 when viewed in the cross-sectional direction of the light beam 44.
A simple example of variation is shown below. In this embodiment, the beam power (light intensity) per unit area is a function of the radial distance from the center of the beam. The center 150 is where the light intensity is greatest. In this area, the light intensity is constant and I m
aw. The area between rings 151 and 152 has a somewhat lower light intensity than center 150. Let the light intensity in this area be uniform and have I max / 1B. The area between rings 152 and 154 is also constant but has a lower light intensity than the previous area. This constant light intensity is difficult. It is ax/e2. Generally, the beam width is considered to be the beam diameter when its light intensity falls below ff188/e2. For this example, the beam diameter is therefore considered to be a ring 154. rings 154 and 156
The area between is also considered to have uniform strength, aX/e3.

FIG. 8 is a bar graph of light intensity taken along line 8-8 of FIG. The center 150 is the light intensity T indicated by the bar 160, and the beam is at the time (1).
This is the point where the highest exposure (light intensity (■) x time (T)) is obtained when exposed to a single point. The X-axis indicates the position along line 8-8 in FIG. Similarly, ring 152 includes the next highest light intensity areas indicated by bars 162a and 162b on the right and left sides of ring 152, respectively, and also exhibits the next highest amount of exposure. Similarly, bars 164a and 164b indicate light intensity across ring 154. Finally, bars 166a and 166b indicate the strength of the intersection of ring 156 and line 88.

The bar graph in FIG. 8 shows the light intensity ■0 on the surface 23 at each radial position of the beam. The exposure caused by the light intensity distribution is dependent on the exposure time and how well the beam is moved along the surface of the liquid. If the beam is stationary, the exposure at that location is simply the light intensity at that location times the material radiation time. In this embodiment, light intensity is a function of radial distance, and therefore exposure is a function of this radial distance times a scale factor. Figure 8a shows this exposure as a relative unit. For a moving beam, the exposure/light intensity interaction becomes somewhat more complex. The exposure at a point traversed by a beam with different intensity zones at a velocity V is the light intensity of each intensity zone traversing the point times the cumulative amount of time each intensity exposes the point. be. For example, if the center of the beam moves along line 9 with velocity V and a portion of the beam intersects point (p), then the exposure given to point P is expressed by the equation below.

Exposure (point p) ==Sun (I(n)1%1I(n)
)/v=(0166)*W(166)+0164
)*W(164) +I(162)*W(162) +
(160*W(160))/v where I (n) is the light intensity of area n, W(n) is the width of area n where the beam intersects point P as it scans along line Q, Further, V indicates the scanning speed of the beam. Point p is from line 2 to line 1 in Figure 7.
If moving within a radius of 50 (within area 160), all light intensity areas contribute to the exposure at this point.

The W(n) value for each area is non-zero. If point p is separated from line 9 by a distance between radii 150 and 152 (area 1
62), only the outer three zones contribute to exposure.

In that case all W(n) values are non-zero except W (16B). Similarly, point P has radius 152 and 154 from line Q.
(zones 164), only the outer two zones contribute to exposure. In this third case, W (
164) and W (166) are non-zero. lastly,
If point p is spaced from line Q by a distance between radii 154 and 156 (area 166), then only the outermost area contributes to the exposure. In this last case, only the W (166) value is non-zero. FIG. 8b shows the exposure in relative units along a series of points placed at different radial distances from line 1. FIG. Scanning exposure (for this type of profile) tends to narrow the relative exposure widths at different radial distances.

FIG. 9 is a juxtaposition of FIG. 8a and a cross section of the photopolymer 22 taken along line 8--8 in FIG. This cross-section is an enlarged view of area 84 taken at the same point in time (stationary beam) as in FIG. As illustrated in FIG. 3, area 84 in FIG. 9 indicates the point at which the critical exposure Ec necessary to gel the photopolymer 22 to a distance Pd below the surface 23 is reached.

FIG. 10 is a diagram taken at the same time as FIG. 4, which follows this. At this point, area 86 has undergone critical exposure Ec and is in a gelled state. Area 84 has received much more exposure than the EC and has polymerized into a -layer condensable polymer.

FIG. 11 is a diagram taken even later, at the same point in time as FIG. In this case, the area 88 has gelled as a result of the neighbor price exposure Ec. Area 86 receives more exposure than Ec and is a more condensable polymer. Area 84 is Ec
It is a much harder polymer because it has undergone much more exposure to E.

2E(d)=EO/e"" can be used to calculate the depth at which the critical exposure has been reached. At each location along the X-axis in FIGS. 9, 10, and 11, this depth determines at least the shape of the photopolymer 22 in its solidified gel state. The bottom 174 of this shape is the deepest part (maximum d value) at the center where the photopolymer x time (exposure) is maximum. In practice, this bottom 174 must be more rounded than indicated by the bar graphs in these figures.

This is because in the actual profile the photopolymer layer varies continuously from the center 150 to the outer ring 156.

Below is an example calculation for determining the shape and size of the bottom portion 174. To determine the hardening depth d caused by the surface exposure E(0), the depth d must be the depth at which the exposure falls to Ec. Therefore, from a known critical exposure value, the cure depth can be determined as follows.

E(d)=Eo/e”Dp, and E(d)=
Since Ec, d = Dp −I n (E O/
E c) is obtained.

For example, in the actuation curve of FIG. 6, E (c) = 16
millijoules/cm2, so the penetration depth is 7.0 mils, and the radius 150 in Figure 7 (area 1 in Figure 8a)
60) For a light intensity of E(0) = 256 millijoules/c, 2 and 9, the following cure depth d is obtained.

δ=7. O* L n (256/16) = 19.
4 mils, so the bottom 174 is the center 1 of the spot 27 on the surface 23.
Located 19.4 mils below 50. If Eo is X-Y
If obtained as a function of the axis 97- line, the hardening depth Pd (keeping Ec constant) can be determined as a function of the X-Y position.

As seen in FIG. 6, the operating curve is plotted as a continuous line up to a certain minimum cure depth; at cure depths below this point, the curve is a dashed line. Such a curve is generally obtained by forming a d1 object as shown in FIG. Such objects have several strings (generally 5 to 9), each string being made with a known different exposure. These exposures are usually determined as a factor of two different exposures. This allows a wide range of cure depths and exposures to be covered with a small number of strings. These strings are generally 2
made by one of two methods. The first law is
Each string is plotted by one scan of the beam with a known profile, a known total power, and a known scan speed. From these parameters, it is possible to determine the maximum exposure line and the amount of exposure at this line. The second method consists in constructing each string using 98 slightly offset paths. The number of these passes is sufficient to produce a uniformly exposed area somewhat wider than the beam width of each string. The amount of exposure of each of these uniformly exposed areas is determined from the total power of the beam, the size of the area covered and the scanning time of this area. Uniform exposure areas result in uniform depth areas. The existence of this uniform hardening depth zone allows the scanning parameters to be selected rationally. In either case, the cure depth can be determined from the known exposed area of each string. Each of these cure depths is plotted against the natural logarithm of exposure. Since the preferred resins obey Beer's law (to a certain extent), the slope (penetration depth) and the X-intersection (critical exposure) can be determined from the straight line formed by these plots. Since these strings are formed in a viscous material, they must have a minimum condensation stiffness such that they can be removed in one piece from the photopolymer container. Since each resin has a different condensation hardness for a given cure depth (specific wavelength of exposure), each resin will exhibit a different minimum thickness of string from which it will be removed (under reasonable conditions). . Reasonable conditions relate to tolerances set for maximum strain due to self-weight. Said minimum thickness is related to several factors regarding the resin, including its depth of penetration for the wavelength used;
These include its viscosity and the atmosphere surrounding the resin.

This minimum thickness can be considered to indicate the minimum effective net exposure. The dashed portion of the curve indicates the area where gelling material can be removed from the resin. This curve section corresponds to exposure values between the critical exposure and a somewhat larger exposure as the minimum exposure. The continuous portion of the curve indicates the areas where strings are formed and removed, and thus where the exposure exceeds its minimum value.

Accurate measurements of peak exposure are required to make accurate cure depth predictions. For a stationary beam, this corresponds to an accurate measurement of the peak intensity. In the case of a scanning beam, this corresponds to the sum of the light intensity elements measured by the light intensity element size parallel to the scanning direction. Generally, the line containing the peak light intensity is the line that produces the maximum cure depth. The net exposure produced by a scanning beam is less sensitive to error variations in peak light intensity than is the case with a stationary beam. However, both of these approaches require fairly accurate knowledge of the light intensity profile and peak light intensity values. In FIG. 7, it was assumed that the light intensity within ring 150 had a constant value equal to the peak value. This may or may not have been a reasonable assumption.

There may have been small areas within ring 150 that had light intensity values greater or less than the average value taken as the peak value. Assuming that this value is a peak value, it may be possible to reduce the penetration depth by up to 70% for each underestimated factor 2. For example, in FIG. 7, the profile is divided into four sections, each section differing from the other by a factor e or 1/e. The following table was obtained from the beam size shown in FIG. 7 and the area and energy of each area.

Area % of total area 160 ・7.4 162 22.4 164 22.9 166 47.3 Light intensity % of total output Hmax) 35.1 1(max)/e 39. I Hmax)/e214.6 Hmax)/e311.2 From the above table, the peak light intensity can be obtained without knowing which rings are sequentially closer to the center. This approach also allows one to predict the amount of error that may be introduced into the case depth.

Peak area 160 + 162 160 + 162 +164 160 + 162 +164+166 + 164 + 166 % of total area Light intensity Error of C, D, 29.8 52.5%Hmax) 70% Dp5
2.7 35-4%I (max) 103% Dp
00 21.1% I(max) 155%op The above table shows the importance that proper determination of maximum light intensity has on cure depth. To ensure adequate cure depth, elements must be selected with relatively small area for a rate of light intensity change per unit length close to the peak light intensity point. One way to make the sample size small enough is to perform profile measurements such that the peak light intensity values are approximately the same in several areas (cells). If, using a grid of uniformly spaced cells, four adjacent cells yield approximately the same maximum reading, it may be safe to assume that the peak light intensity has been properly found. If a greater safety margin is desired, the cell considered to be the peak should be surrounded by nine or more adjacent cells (given that the beam is somewhat radially symmetrical and has a single peak, a square shape cells) to obtain relatively uniform readings for all these cells. Fortunately,
Scanning beam exposure is much less sensitive to deviations in peak intensity, so some error in peak value is generally not a problem.

Preferred materials for stereolithographic techniques generally obey Beer's law up to a certain hardening depth/penetration depth combination.

That is, for any effective penetration depth to cure to a particular cure depth, the resin follows Beer's law very well until this cure depth is exceeded. For example, if 5LR-800 manufactured by Dead, Inc. of Des Plaines, Illinois is used in layers from about 5 or 10 mils to about 30 mils thick, 325
It exhibits a penetration depth of approximately 7 mils when cured at nm wavelengths. Within this range the resin follows Beer's law well, but at a cure depth of about 40 mils the material begins to absorb more strongly than predicted by the power law.

The curing width can be determined by determining the X-Y position where the curing depth is zero. Determine the width (x-y dimensions) of the batten cured material formed by these transition points. If the exposure due to a given area is less than the critical area, then using the above formula will result in a negative cure depth which is interpreted as zero cure depth. When determining the cure width using the beam profile and cure depth, it is more accurate to determine the cure depth based on the minimum exposure Em rather than the critical exposure. When considering cure depth, exposures slightly higher than the critical exposure will not result in any effective cured material. Similarly, when considering cure width, effective cured material is not reduced as critical exposure is approached. The cure width predicted using E(c) gives satisfactory results if beam and scan techniques are used to produce a rapid transition from high to low exposure near Ec. However, using beam and scanning techniques Ec
The cure depth predicted using Em gives a better prediction if it causes a slow spatial return from high to low exposure near .

In order to make accurate predictions of cure width, one must have light intensity profile information consisting of light intensity measurements in the spatial gap that are at least about twice as accurate as the expected cure depth is to be determined. Must be.

Although most of the examples described above were based on stationary beam exposure, once the surface exposure has been determined, the remaining steps in determining the cure depth and width can be performed even when the beam is stationary. Same thing when scanning - IO! l)-.

Decreasing the critical exposure Ec and increasing the penetration depth DP while holding Ec constant increases the distance d of the surface 23 over which the bottom 174 is formed at a particular time. The amount is predicted by 2E (d)=Eo/e"",
In this equation, E(d)=Ec. Penetration depth DP while maintaining a specific surface exposure EO and a specific critical exposure
The depth of the bottom 174 in each area is adjusted by adjusting . This also allows the transition depth 172 between the condensed plastic in area 86 and the gel in area 88 to be varied. Similarly, the transition depth 1 between the highly plastic plastic of zone 84 and the condensable plastic of zone 86
70 can be adjusted.

Further, these transition depths can be easily determined by substituting Ec·21 and EC−e2 in place of E(d) in the above equation. Curve 174.1
It appears that 72 and 170 do not correspond to actual bodies of solidified material. This is because there appears to be no discontinuity in beam strength.

By varying the penetration depth, and thus by adjusting the location of each zone of partially solidified plastic, the overall percent polymerization of the gelling material can be varied. Therefore, the overall green hardness of the gelling material is also changed.

Such changes in overall green hardness, and changes in the polymerization extension gradient through the thickness of the assimilated material layer, alter the ability of this thickness of material to resist bending moments. For a given cure depth, increasing penetration depth tends to decrease percent polymerization, green hardness, and bending moment resistance. However, for similar case depths, increasing penetration depth tends to increase percent polymerization, green hardness, and bending moment resistance.

In summary, a more detailed beam profile than that shown in FIG. 7 can be used to more accurately predict and control the bottom shape and transition. To make accurate predictions from the scanned beam, this beam motion must be taken into account to determine the net exposure at a given point. 1
The net exposure at a point is the sum of the exposures of each element taken along a line passing through point P and parallel to the scanning direction.

Therefore, if the exposure is accurately determined, the effective cure depth and width can be obtained.

As described in U.S. Patent Box 4,575,330, SL
A beam of radiation in A scans along the surface 23 of the photopolymer 22 to cure one layer. The diagram in FIG. 7 shows the intensity profile of the light beam 44.

If this beam is stationary as shown in Figure 8a, this pattern times the exposure time represents the exposure pattern of such a stationary beam. However, due to the motion of the light beam in a typical SLA, the light intensity pattern in Figure 7 is
An exposure bar similar to figure b is produced, which shows the highest exposure bar at the center of the motion path corresponding to the center of area 150. The diagram also shows a steeper drop in relative exposure with distance from the center than for static beam exposure. In actual use, the intensity gradient in the cross section of the laser beam is a continuous line rather than a broken line.

Thus, in the above example, the actual pattern of the moving beam decays from the highest exposure near the center of the motion path to the lowest exposure at the outer edges.

In a scanning laser beam, the overall exposure is controlled in part by controlling the speed of motion. Exposure at a given point is inversely proportional to scanning speed.

In the SLA of the present invention, the beam profiles do not have to be concentric. For example, the maximum light intensity may be off-center, or there may actually be multiple peak light intensity areas. Although the two-dimensional light intensity profiles of the stationary beam need not be concentric, it is highly desirable that the one-dimensional total light intensity profiles obtained by scanning the beam in various directions have similar characteristics. Of course, it is highly desirable that these two-dimensional profiles be the same regardless of the scanning direction and be symmetrical with respect to one of them. It is then desirable for the scanning beam to produce similar cure depths and widths within a tolerance of 10% of the layer thickness and 10% of the nominal width, regardless of the scanning direction. This allows the exposure parameters used during the system to be determined and controlled independently of the scanning method. If the beam does not meet these requirements, the laser and/or optics are adjusted to meet these requirements. If this requirement became too burdensome, these beam profile characteristics could be mixed in the exposure control system to accommodate the differences between different scan directions.

Table 1 below is an example of a real beam profile, each number determining the surface light intensity IO in the measurement point grid.

0100 1200 2831 31120 0211 According to Table 1, the light intensity at each point is the power at that point, which is determined by a determined number (such that the sum of the values at each point is correlated to the actual total power of the beam). (needs normalization) divided by the area represented by each point. If the beam moves at a constant speed from left to right in the diagram, the exposure ramp for this profile can be determined by adding a column of numbers from left to right to determine the net light intensity value for this column. Ru. This net light intensity value is multiplied by the time it takes to traverse the length of one cell. - In this way, the total value of each column was obtained as the corresponding number in the rightmost column.

0010011 0120 Old 3 1 2 8 3 11 15 Table-1a0
311 2 01 16 0021114 By the way, let the planning constant be 1 and the time to traverse one cell be 1. The numbers in the rightmost column thus indicate the exposure (and total light intensity) by the beam running in the indicated direction. The horizontal swath traversed by this movement is 12a
The exposure pattern is shown in the figure. Stripe 206 has the highest exposure and stripe 204 has a lower exposure. The exposure falls off rapidly above and below these stripes 206 and 204. These stripe exposures are in a proportional relationship given by adding each beam profile exposure from left to right.

E200: E20.2: E204: E20
6: E208: :1:3:15:16:4 If the 5 horizontal sum of Table 1a above is the exposure of each stripe in millijoules/cm2, then the hardening depth of the scanning path in Figure 12a is given by the formula: It can be determined using E(d)=Eo/e"". The hardening depth is the depth at which the critical exposure Ec has just been reached. If the penetration depth is 7.0 mils and the critical exposure is 2 mj/cm2, then the exposure EO is 15 mj/cm
The hardening depth of the stripe 204, which is 2, is given by the following equation.

d=Dp・1~(Eo/Ec)=7. Ox
1 ~ (15/2) = 1. Ox2.0=14.0
The bottom of the mil and gelled area below stripe 204 is 14.0 mil below surface 23.

Similarly, if a beam with the profile shown in Table 1 moves at a constant speed from the top to the bottom of the 113 drawing, then
The surface exposure is obtained by summing the column of surface exposure Eo values as shown in Table 1b below.

0100 1200 2831 31120 TABLE-1b The swath traversed by this movement exhibits the exposure pattern shown in FIG. 12b. The pattern is mostly symmetrical, with the center stripe 214 of the swath having the highest exposure.

The five-stripe exposure has the following ratio values corresponding to the movement speed:

E210:E212:E214:E216:E21B:
:1:6:24:6:2Similarly, if the beam path moves diagonally toward the bottom right of the drawing, the exposure pattern will have values arranged diagonally of the surface exposure Eo. By adding, the result will be as shown in the table below.

00 00 8 3 1 10 11 2 D /2 2 1 1 15 /12 /14 6 0 The diagonal path drawn by the movement in the table is the exposure pattern shown in FIG. 12c. The width of the cell changes by a factor of 1/v2 since the distance between the measurement points is small. This factor must be taken into account when determining the exposure. Stripe 226 has the highest exposure and stripe 228 has the lesser exposure. On either side of these stripes 226 and 228 the exposure falls off rapidly. These stripe exposures have the following proportional relationship by adding each exposure from the top left to the bottom right of the drawing.

E220: E222: E224: E226
: E228 : E230 : E232 : E2
34: E2360: O: 6:14:12:
5: 2: O: 0 In this example, the outer stripes 220.222.234, and 236
each receive zero exposure, so Figure 12c shows that the other 5
Limited to stripes.

As mentioned above, these stripes are merely a stepwise representation of continuous exposure changes along the path of the laser beam.

The light intensity profile described above and the corresponding light intensity profile sum value give somewhat specific results regarding the symmetry of the profile on either side of the maximum total light intensity maximum and the overall beam width. Therefore, while such a distribution is useful for displaying a few points, it cannot be used in an SLA unless the SLA has software or hardware to compensate for variations in exposure due to scan direction. It's not appropriate. Although such performance has not yet been achieved in the SLA software of the present invention, it can be easily obtained. The SLA of the present invention controls exposure by changing the scan speed. Also, since this SLA scans on a vector x vector basis, the scan direction must be matched to a precompiled relative exposure list based on the scan phrase to compensate for the lack of symmetry in the total light intensity distribution. It is easy to set the parameters necessary to adjust exposure. This lookup table interpolates scan direction values that are not present in the table and requires only decimal correction values. In a preferred embodiment utilizing beam profile characteristics, the spacing between each cell is 1 to 4 mils along the X and Y axes and there are 10 to 20 cells along each axis. This creates a square of 100-400 cells covering a range of 10 mils by 10 mils to 80 mils by 80 mils. Commonly used beam diameters are on the order of 10 mils. Additionally, each cell is generally capable of recording light intensity values on the order of four magnitudes.

17- Once the exposure buttons are known, these exposures and/or total light intensity profiles form fill areas (areas where all area is exposed) to optimize SLA performance for skin fill creation. It can be slammed like this. This optimization process consists in balancing the following few parameters: 1) the need to produce skins of uniform thickness; 2) the need to keep the number of skin fill vectors within proper limits; and 3) the need to not exceed a few scan speed limits. For example, if the exposed button of FIG. 12b is obtained, four adjacent traces repeat the same exposed button four times.

G6:24:6:21:6:24:6:21:6:24
:6:21:6:24:6:2 However, if the outer two stripes of each set of 6 balanced traces are overlapped, this overlapping platform will cause a slight offset in constructing parallel skin vectors. . If each cell is 2 mil square, the vector offset is 1 if they do not overlap.
0 mil and if the two stripes overlap, the offset is 6 mil. Although the cumulative exposure pattern in the same area is less uniform than before, it is still very uniform.

This overlapping process is continued until a cumulative exposure that provides the desired uniformity is obtained. For example, three overlapping stripes would result in the following cumulative exposure:

16251227122712271227, . 12
2662° On the other hand, the overlapping of quadruple platform stripes results in the following.

17313739393939 , , 393282 In the above embodiments, the four stripe overlap produces the most uniform exposure and therefore the most uniform cure depth. However, with this degree of overlap, the offset between the fill vectors is one cell, where one cell is 2 mils. The closer the vectors are to each other, the more vectors are required to cover a given area.

Therefore, if the vectors had to be stored before drawing, the size of the vector storage file would become excessively large.

Therefore, it must be ensured that a specific offset is required before creating the vector.

This is because using a large offset reduces the number of vectors that need to be stored. In this example,
In certain conditions, a 3-stripe overlap (2-stripe offset = 4 mils) provides sufficient cure uniformity, so using this spacing reduces storage requirements by half. Another issue to consider when determining the skin fill spacing is the limited scan speed at which the beam can be moved in a controlled manner. Therefore, there is a minimum vector offset that can be used to create a skin fill. G
5L using eneral scanning reflector
For the A250, a reasonable maximum scan speed is approximately 32 inches per second. For a large volumetric plate apparatus called the 5LA500, which uses a Greyhawk scanning mirror, the maximum scanning speed is approximately 100 inches per second. These speeds can be adjusted somewhat up or down according to the beam profile. For example, with respect to the graph of FIG. 6, it was stated that a particular exposure is required to obtain a particular cure depth. Required exposure E and laser power.

If P and the maximum scan speed are known, the following equation can be used to determine the nearest (minimum) skin fill vector spacing (offset).

Maximum 41 intervals = L, P, / (E * maximum speed) For example,
If you have a layer thickness of 5 mils and are trying to obtain a corresponding skin fill depth, as shown in the graph of FIG.
mJ/cm2. If the laser power used is a beam with a total power of 20 mW and a maximum scanning speed of 32 inches per second (81 cm/sec), then the minimum fill vector spacing is: 0.020/(0,032 zero 81) - 0 ,0077cm
= 3 mil.

Depending on the light intensity profile of the beam, this minimum vector spacing or even larger spacing can be used to obtain a reasonably uniform cure depth.

On the other hand, the maximum drawing speed is 100 inches per second (254 cm/second).
If the laser output is 4001, the minimum vector spacing for the same hardening depth is 0.100/(0,032*
254) 0.0123 cm = 4.8 mil. For beam diameters of about 10 mils, this minimum vector spacing presents some difficulty in producing areas of uniform hardening depth.

If this minimum vector spacing is too large to achieve the desired uniformity, one of the parameters in the above equation must be changed so that a smaller minimum value can be used.

To obtain greater exposure for a given cure depth, the laser power can be reduced or the wavelength or material changed, or the maximum scan speed can be increased somewhat (with a loss in accuracy). . Furthermore, not only do these parameters require modification, but the ability to make these modifications can be built into the system. For example, during the formation of a three-dimensional part, the laser power can be varied by inserting an attenuation device into the beam path running from the laser to the scanning mirror. This damping device can be inserted and withdrawn as required by computer control.

The damping device can have different degrees of opacity depending on how far it is inserted into the beam path. This method allows vector spacing to be sufficiently shortened without excessive loss in formation speed as when a single opaque element is used. Another method is 5pec used on 5LA500
tra-Physics or Coherent Ar
The laser's emission (and thus its output) can be directly controlled, such as by using a gon ion laser.

Yet another method consists in using filters that attenuate the energy output of some wavelengths (if a multi-wavelength laser is used) to obtain different operating curves and therefore different exposures. Another method is an automatic method and apparatus that switches the radiation of a laser between its various wavelengths and uses the optimal wavelength (switching of the argon ion laser is possible by changing the prism angle within the laser path). ). As is clear from the above discussion, the spacing of the skin fill vectors can be optimized by using beam profile characteristics and, if necessary, by changing some shaping parameters or by automatically controlling these parameters. Variations can be used.

A specific depth of hardening is reached as a result of a specific exposure.

Therefore, if we increase the number of fill vectors covering a given width of the area to be cured, the scan speed must also be increased - to obtain the same exposure. Therefore, for a given cure thickness, given wavelength used, and given resin used, there is an amount of exposure necessary to cure the area to the desired depth. For a given laser power and number of vectors covering this area, there is a scan rate required to produce the desired amount of exposure.

There are many additional refinements and improvements to the present invention that can be obtained using a beam profiler.

First, the beam profiler of the present invention uses a punch top to more accurately determine critical exposure EC and penetration depth. A beam profiler is used to more accurately determine the depth of penetration and the exposure required to obtain the critical exposure Ec from the top. Basically the surface exposure E of the string part whose depth d is to be measured
O can be measured more accurately. The example of Figure 16b shows that the bottom of each string should be of uniform depth. This is because the light intensity of the beam is assumed to be uniform. Because the exposure is generally not uniform, these strings generally have curved bottoms. The maximum depth area is the area corresponding to the maximum exposure area.

For example, for a beam profiler, the beam used is shown in Table 1.
It is found that it has a profile of 6a.

Assuming that the beam scans downward along the path 334, the cross-section (silhouette) of the string 336 is as shown in Table 1b.
has a varying depth d based on the total value of . string 33
The center of the cross-section of 6 is the deepest as it receives more exposure than its edge portions. The deepest part of the string 336 is measured because it is easier to approach than other parts. Table 1b
The sum value 24 at corresponds to the deepest part, or center, of string 336.

As shown in Table 1b, the center 115 of the string receives 24/39 of the total exposure. If the surface exposed EO applied to string 336 is 10 mJ/cm2, then the center 115 of string 336 is (24/39) - 10 mJ/cm2.
Cm2 or 6.15 mJ/cm2. This amount of exposure per unit area is used as the EO for plotting the actuation curve or for determining the depth of cure.

Second, the beam profiler of the present invention reduces the number of pans and tops required. Once the initial punch top is created for a given polymer and laser (single wavelength), a beam profiler is used to correct for variations in light intensity. If a beam profiler is not used, punch tops must be made frequently. A beam profiler is used to measure the change in light intensity at each wavelength and change the beam scanning speed accordingly. A beam profiler provides the information necessary to predict cure depth and width. For a resin with known penetration depth and critical exposure,
Since the beam profiler controls the cure depth and cure width by the control system 28, a punch top is not necessary.

Beam profilers can also be used with multiple wavelength sources to reduce the need for making punch tops and predicting curing parameters based solely on resin properties. this is,
This is accomplished by creating a separate beam profiler for each wavelength used, and using the profile information for each wavelength in combination with the resin properties for that wavelength. For example, each wavelength will have a different critical exposure and penetration depth that must be taken into account. It is possible to determine the degree of contribution to curing by each wavelength. Each contribution can then be compared to see which contribution dominates the considered curing parameter (eg curing depth). If one wavelength dominates a curing parameter, it can be considered the only dominant wavelength for that parameter. However, if a dominant wavelength does not exist, other approaches to predicting curing parameters can be used. For example, a certain degree of polymerization is required to produce a gelling material. Therefore, instead of using the amount of cure corresponding to each wavelength, it is possible to measure the degree of polymerization induced by all wavelengths for each unit volume and from this degree of polymerization to determine the cure characteristics of each unit volume.

Third, FIG. 23 shows that the beam profiler in the present invention allows accurate edge grading.

The main feature of the invention is to determine the cure depth and the cure width corresponding to a given depth. A number of guidelines, such as those described above, exist for selecting the depth and width of cure considering the beam profile.

FIG. 23 shows a design m610 of a three-dimensional part 30 formed from photopolymer 22. FIG. To the right of this design edge is the three-dimensional part 30 and to the left is the uncured polymer 22, which is placed in the container 21. Design edges 610 are where the computer-aided design has a non-horizontal boundary between the desired three-dimensional part 30 and the uncured photopolymer 22. Since the beam profile of the light 44 is not uniform, the cure depth and cure width will vary depending on the design edge 610.
is not uniform. Overlapping beams can flatten the cure depth along the downward horizontal plane, but cannot modify the shape of the vertical edges.

Figure 23 shows a few preferred means of solving this problem. These means are selected by the user or control system 28 according to the desired finish.

When finishing the edges of the three-dimensional part 30 by sanding or sandblasting to obtain the design m 610, an oversized structure 620 may be selected. Steady state 622 shows the shape of photopolymer 22 cured in the last light pass perpendicular to the drawing. Shape 624 shows the shape of photopolymer 22 cured in the last laser pass of layer 626. front surface 62
8 had the same extension as surface 48 when N626 was formed. These areas 630 and 632 must be sanded away leaving three-dimensional part 30 with design a 610. The bottom of shape 622 hangs below front surface 628 and is secured to layer 626, and similarly the bottom of shape 624 is secured to extend forward.

There must be material to stick on top of the previous layer129
- If so, the feature 624 will harden to a thickness of IN. layer 6
If 24 and 626 were cured to different depths, the layers would have different widths and would therefore require different amounts of offset for the edges or centers of each layer to be properly positioned. will need it.

Since the cure depth and cure width can be predicted using beam profile information and resin properties, appropriate corrections to the cure width can be determined.

The lower structure 640 is selected when finishing the edge of the three-dimensional part 30 by filling to obtain the design edge 610. Shapes 642 and 644 are respectively three-dimensional parts 3
This is the shape cured by light path 44 for layers 646 and 648 of 0. When three-dimensional part 30 is removed from container 21, areas 650 and 652 are free of cured polymer. These areas 650 and 652 are therefore designed m
Must be filled to make 610.

One method consists in pouring the photopolymer 22 over the three-dimensional part 30 before it is placed into a post-curing device. The method is described in US Pat. No. 2,680,428.

130- When painting or coating the edges of the three-dimensional part 30, a primer structure 660 is selected. Shapes 662 and 664 are intentionally hardened a distance to the right of design edge 610. The selected intervals are painted with an average thickness of paint. The method is described in US Pat. No. 339,246, which is incorporated by reference.

Average structure 680 is chosen for minimal three-dimensional part post-processing. In many applications of three-dimensional parts 30, this average structure 680 is a preferred compromise when design edges 610 are not available.

FIG. 24 shows the above structure applied to a design slope 710. Depending on the situation, there are various possible movements of the boundary vector (vector of the boundary between the outer and inner areas). This depends on the slope of the bounding surfaces, the type of post-treatment performed, and primarily on the depth of hardening. Therefore,
Determining the beam profile is most important in determining the proper offset, especially when the offset is automatically achieved.

Fourth, the use of a beam profiler in the present invention facilitates calculation of the minimum surface angle (MSA) for a given cure depth. The MSA is the minimum angle at which a semi-perpendicular surface of three-dimensional part 330 can be tilted from a horizontal plane without leaking uncured photopolymer 22. When the three-dimensional part 30 is removed from its container 21, it contains some amount of uncured photopolymer 22 that flows out of the part before undergoing post-curing. This results in cost and time savings since curing of photopolymer 21 in a post-curing device is cheaper and faster than curing in SLA. Also, if curing is performed during a post-cure process rather than forming during SLA, some of the distortions (eg, bending) are reduced, which is favorable for accuracy and platemaking.

As shown in FIG. 24, the design slope 710 allows the photopolymer 22 and the three-dimensional part 3 to move more easily than the design edges 610.
The boundaries between the two become uncertain. That is, the polymer flows between each pair of layers shown. For example, in average structure 680 layer 71
Most of the liquid polymer remaining in 2 leaks out through the void 670 when the three-dimensional part 30 is removed from the container 21. Therefore, the angle 711 of the design slope 710 with respect to the horizontal is MSA. This is because if this angle 711 is further reduced, actual leakage will occur.

FIG. 25 shows a design slope 720 having a larger surface angle 721 than MSA 711. In this case, leakage is expected. In fact, liquid exiting layer 724 leaks through gap 726 and void 728. The beam profiler has shapes 730 and 732. Predict leaks by showing

Control system 28 can compare these shapes to surface angle 721 to determine if surface angle 721 is less than or equal to MSA. If it is less than MSA, CAD
The data generator is the skin 7 between shapes 730 and 732.
29 to prevent such leakage.

The relationship between such surface angles and parameters can be expressed by the following equation.

MSA = ArcTan (21 Thickness / (Maximum Width + Minimum Width)) where maximum width is the maximum width of the solidified material created by the boundary on the bottom layer, and minimum width is one level below the top surface of the top layer. is the width of the solidified material. These widths can be predicted from beam profile information and known cure depths, allowing for the required MSA for each parameter set.
It is possible to predict 133-. If the inclination angle with respect to the horizontal is greater than MSA, then
Whether this side faces upwards or downwards, some type of filling is required next to the lower layer. Areas requiring this type of filling are called near-flat areas or areas requiring near-flat skin.

Other information regarding MSA and near flat skins is contained in the aforementioned US patent application Ser. No. 331,664.

Depending on how the near-flat boundary is created, other important properties can be predicted by the method described above. In the method described in the above-mentioned US patent application Ser. No. 331,664, the downward near-flat area is used to form part of the superstructure of a three-dimensional part and for filling leak areas. In this case, even though the filling need not exceed this value, the formation of these near-flat boundaries will reduce the MSA
There is no need to exceed the value. Beam profile parameters can be used to predict what non-perpendicular angles will contribute to the creation of such structural boundaries. The surface angle (each surface triangle as used by current CAD interfaces) becomes steep enough to a certain extent that the formation of a near-flat downward boundary becomes unnecessary.

Fifth, beam profile information can be used in conjunction with resin parameters to determine the amount of polymerization for each unit volume. Therefore, a table or formula is used that relates the amount of exposure (ie, the energy absorbed in a given volume) to the amount of polymerization (eg, percent) induced in this volume. Several tables or formulas can be used that correspond to each wavelength used in the solidification process. From the beam profile and the amount of surface exposure, it is possible to know how much exposure each unit volume has received, and therefore it is possible to determine the average amount of polymerization in a specific unit volume. Determination of the average polymerization is obtained by summing or integrating the degree of polymerization in all elements. Polymerization gradients are determined by comparing the degree of polymerization in adjacent cells. The determination of such degree of polymerization can be considered as the basis for determining other related parameters. The degree of polymerization is related to the gel point of the material and therefore to the cure depth and cure width formed by a given exposure. In this way, the polymerization induced by several different wavelengths can be accumulated to determine the amount of net polymerization for each unit volume, from which the net cure depth and width can be predicted. The degree of polymerization induced in the resin by each wavelength at a given exposure can be determined by various chemical methods, extraction methods, or spectrophotometric methods. Once determinations have been made, such as critical exposure and transmission source, beam profile information can be used to make the necessary determinations and predictions to know the exact conditions. Various other parameters affect these predictions, so these other factors must be held constant or listed in the variation list. These parameters include the temperature at which the exposure is carried out, the amount of oxygen absorbed into the resin (and thus the gas surrounding the resin), the presence of other inhibitors, and the properties of the resin used.

Sixth, the use of beam profiler pairs provides superior information regarding green hardness in the present invention.

Figure 15, without the beam profiler, shows the levels of hardness. Areas 318, 316 and 314 are very hard plastic and extend an unknown width across area 84. This green hardness value can be used as a relative measurement based on the different amounts of exposure received by each unit volume. In this case, the average green hardness is considered to be the sum of the exposed amounts of all unit volumes divided by the total volume. This is very close to the relative polymerization amounts made based on the same calculations. However, it is more effective to have an absolute or relative hardness that corresponds to a specific degree of polymerization per unit volume. This is because the change in green hardness from the gel point to the complete solidification point is not necessarily linear. The relationship between green hardness and degree of polymerization can be entered in the table above, or can be expressed by a suitable formula.

By this method, the green hardness can be determined for each unit volume and integrated to obtain the overall hardness parameter of the partially solidified material, and the average value can be obtained for the entire volume. Since green hardness is a function of degree of polymerization, this method (comparison of degree of polymerization and green hardness) can be used to determine the net green hardness of solidification at multiple wavelengths. The degree of polymerization per unit volume in this case is determined and this is combined with the specific green hardness (relative or absolute) per unit volume.

The chemical composition of the gas surrounding the resin (assuming that the gases absorbed in the resin and the surrounding gas are in equilibrium) has a large effect on the curing parameters. For example, oxygen acts as an inhibitor of polymerization reactions. This is because oxygen destroys free radicals before they can induce polymerization. Oxygen also reduces the average molecular weight of the polymer chains by prematurely terminating the polymerization zone. This effect on molecular weight has a large impact on polymer properties. As another example, if two similar resins and wavelengths are used, one in equilibrium with nitrogen gas and the other in equilibrium with air, the resin in equilibrium with nitrogen gas has a lower critical energy. and form a gel at a much lower level of exposure than the underlying material. However, the green hardness of this gel is much lower and is therefore not effective. When these separate bodies complete polymerization in equilibrium with their respective gases, the properties of the resulting plastics differ due to the different bond structures. Therefore, it is important to consider the atmospheric gas in which the resin is used when determining resin parameters. The use of different atmospheres may be an effective way to vary resin parameters to obtain different cure parameters for green-cured and post-cured parts.

Seventh, the beam profiler has the ability to predict at least the relative value of bending resistance of a certain amount of solidified material. Generally, the solidified material is a single line of hardened material, but it can be a specific layer of raised areas or a combination of several layers of solidified material. This bending resistance is related to the stiffness of each unit volume, which must be measured by its distance from the bending axis.

For example, FIG. 26 shows a beam profile 760.

This beam profile 780 has two wavelengths λl and λ2.
receive equivalent power and light intensity from. The operating curves for these wavelengths are illustrated in FIG.

At the same time that λ2 forms zone 314, wavelength λ1 of deep penetration depth 38 forms zone 770. At an even longer time, the area 316 is formed by the short penetration depth wavelength λ 2 while the long penetration depth wavelength λ
1 forms area 772 with λ2. At the same time as zone 318 is formed, wavelength λ1 of long penetration depth is formed in zone 77.
form 4.

When implementing the invention without a beam profiler, various information, predictions and control values are lost. It becomes difficult or impossible to determine the width and depth of hardened areas, such as very hardened area 318, more hardened area 316, and most hardened area 314.

Beam profile 760 is very stiff so zone 3
18 indicates that the area 772 is not very wide.

Eighth, a beam profiler can be used to predict the overcure needed to obtain proper adhesion between layers. Proper adhesion between the layers requires some degree of cross-polymerization between the assimilated material at the bottom of one layer and the solidified material at the top of the previous layer. A certain amount of material must be over-polymerized to adhere to the previous layer. That is, overcuring is necessary to fully polymerize the top of the previous layer and ensure adhesion between the previous layer and the current layer. Given resin and forming conditions (e.g. ambient gas temperature and chemical composition)
1 to guarantee adhesion with one unit volume.
It is possible to create a table regarding the degree of polymerization of one unit volume (the previously cured volume) and the degree of polymerization required for the second volume.

Alternatively, it is possible to create a table of maximum exposure differences that will ensure adhesion between two sides (one side cured first).

Using the above table with the beam profile information, the beam profiler can determine and predict the degree of polymerization and exposure of the top of the previous layer and the bottom of the current layer.
You can determine and set the required overcure. Stiffness tables only need to be created for a given resin and wavelength. Therefore, by using such a table when the resin is supplied to the user, there is no need to worry about determining the required overcure. This technology can also further automate the manufacturing process of 3D parts through the use of beam profilers, thus bringing stereolithography one step closer to a push-button (turnkey) prototyping/modeling system. .

Ninth, as mentioned above, the beam profiler can use a single wavelength or multiple wavelengths to determine various curing parameters. When multiple wavelengths are used, it is preferred that a beam profiler analyze the output/light intensity of each wavelength alone. The analysis for each wavelength is as follows:
This can be done by using various filters to block the beam either in the beam profiler itself or placed at appropriate points along the beam path. Preferably, a filter is used so that only the wavelengths to be scanned are present in the beam. However, this is not always possible, so another approach is to perform a number of scans with and without different filters with known transmittances, and then use the data obtained and the filter's transmission characteristics to determine the output at each wavelength. and confirm the profile.

Such determined values can be associated with various resin properties. From this association a number of important curing properties can be determined. Also, as mentioned above, beam profilers can play other important roles in the implementation of stereolithographic techniques. This includes the ability to automatically set and update desired formation parameters without user intervention, the ability to automatically switch between wavelengths when multiple wavelengths are used individually, and the ability to use wavelengths simultaneously or singly. This includes the ability to control the energy ratio between different wavelengths and the ability to alert the scanner to the occurrence of a problem. The switching function between wavelengths is performed by the computer in response to forming parameters determined by analysis of beam profile information and known information about the object being formed. Each wavelength is obtained individually by filtering a multi-wavelength beam, or by sending the beam into an optical path that each emanates from a single wavelength source, or by switching a radiation generator to produce the desired wavelength. Control of the energy associated with each wavelength can be accomplished by filtering or by combining two beams from each source and adjusting the output of each source appropriately.

In summary, various approaches and advantages of using beam profiler information (along with resin parameters) to predict and/or control cure parameters have been described, some of which are listed below.

Other than 1) the ability to establish a beam profile for each wavelength, and 2) initial evaluation of resin parameters based on various physical, optical, and chemical tests (based on the beam profile and known resin properties),
3) A combination of suitable control mechanisms to form a feedback loop to ensure a specific output ratio for each wavelength; 4) Ability to predict cure depth; 5) Curing width prediction function, 6) Average polymerization amount prediction function, 7) Hardness prediction function of solidified material, 8) Prediction function of bending moment resistance of solidified material, 9) Required MSA prediction function, 10) Best Skin fill vector interval prediction function, 11
) the ability to predict the overcuring required to produce (a certain amount of) adhesion between two layers; 12) the ability to select beamwidth correction parameters.

To make the above first-order prediction, two types of information are required: 1) a list of resin properties for each wavelength used to solidify the resin, and 2) beam profile information.

Higher order predictions use additional resin properties and more complex radiation/resin interaction theory. The resin properties necessary to achieve the above prediction are as follows = 1) Transmission depth of each wavelength, 2
) the lowest critical exposure of each wavelength ~ 3) the efficiency of each wavelength; 4) the percent polymerization for various exposures of each wavelength; 5) the percent polymerization required for gelation; and 6) the degree of adhesion with previously partially polymerized materials. and 7) appropriate hardness parameters for various degrees of polymerization. Temperature is generally a controlled parameter, but if the temperature is to be varied this must be taken into account. Various other parameters can be used instead of the above parameters. This and that parameter can be determined when each resin loft is manufactured.
Alternatively, each resin loft can be quality tested to ensure that the values of each parameter are within a specified range. In order to make all the necessary predictions, a resin parameter list can be provided and combined with the specific beam profile information of a given device. These predictions can be used to further automate the forming process. These predictions can be used to control various parameters necessary to form a three-dimensional part with specific characteristics, as described in (2) above. For example, several filter banks can be computer controlled to block or not block the beam. Each filter is used to attenuate a particular wavelength by an approximate amount. These filters 145- are then used in conjunction with the beam profile to ensure that the various wavelengths present have the desired ratio ranges of power and peak power (this is a multi-wavelength implementation). These beam profile predictions can be used for single wavelength and multi-wavelength applications. The invention is not limited to the embodiments described above; other embodiments will be apparent to those skilled in the art.

[Brief explanation of drawings]

FIG. 1 is a block diagram and cross-sectional view of the stereolithographic apparatus (SLA) of the present invention; FIG. 2 is a vertical cross-sectional view of the photopolymer container of the SLA; and FIG. 3 is a cross-section of FIG. 2 after small exposure. 4 is a sectional view of FIG. 3 after further exposure, FIG. 5 is a sectional view of FIG. 4 after exposure, and FIG. 9 is an enlarged cross-sectional view of the bar graph of FIG. 8 and the cured photopolymer of FIG. 3; FIG. 10 is a cross-sectional view of the bar graph of FIG. 8 and the hardened L' of FIG.
FIG. 11 is an enlarged cross-sectional view of the cured photopolymer shown in FIG. 8, an enlarged cross-sectional view of the cured photopolymer shown in FIG.
The figures show an exposure button in which a specific laser beam is moved along the surface of the container after photopolymerization, with horizontal movement in Fig. 12a, vertical movement in Fig. 12b, and diagonal movement in Fig. 12c. Figure 13 is a graph showing the relationship between light absorption and wavelength of a photopolymer, Figure 14 is an operating curve for each of two wavelengths in the photopolymer, and Figure 15 is a photopolymer cured at two penetration depths. Figure 16a is a plan view of Panjiyo Top, Figure 16b is a side view of Panjiyo Top, Figure 17 is a block diagram of the chemical reaction during SLA, and Figure 18 is a diagram of two types of photopolymerization. Figure 19 is a graph showing the relationship between wavelength and energy absorption of initiators, absorption and effective polymerization of two types of photopolymerization initiators, Figure 20 is a bar graph of Figure 8 and curing of Figure 3. 21 is a cross-sectional view of another system for exchanging photopolymers in SLA, and FIG. 22 is a cross-sectional view of another system for exchanging photopolymers in SLA. A cross-sectional view of yet another system for exchanging photopolymers; FIG. 23 is a schematic diagram showing four structures on the vertical edges of a three-dimensional part made during SLA; FIG. FIG. 25 is a schematic view showing four structures of the sloped edge portion of the original part, FIG. 25 is a schematic view showing a steeper sloped edge than FIG. 24, and FIG. 26 is a view showing the hardening depth corresponding to the beam profile. 20, CAD data generator, 21. ,, container, 2
2. , , photopolymer, 23. ,, Processed surface, 2B, , Light source, 30. ,, three-dimensional parts, 30a, 30b, 30c, ,
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Claims (1)

[Scope of Claims] 1. In a stereolithographic apparatus for replicating a three-dimensional object by irradiating stimulating radiation and forming successive layers of material that harden in response to said stimulating radiation, comprising: a stimulating radiation source simultaneously comprising at least two distinct wavelengths having different penetration depths into the material; a platform affixed to a first layer of the three-dimensional object; and adjusting the height of the platform. A three-dimensional flat plate device comprising a platform control device for controlling the device.