DE10236907A1 - Apparatus for making moldings using computer assisted design techniques by fusing layers of e.g. ceramic powder has leveling plate which smoothes off new layers of powder and bends over fixed obstructions - Google Patents

Abstract

Apparatus for making moldings by building up layers of metallic or ceramic powder which are fused or sintered using lasers has a leveling plate (68) which smoothes off each new layer of powder as it is applied. This is flexible and bends over fixed obstructions (55).

Description

The invention relates to a device for producing a shaped body by layer-by-layer build-up from powdery, in particular metallic, single or multi-component material, with a carrier for the layer structure, an irradiation device for irradiation of the material powder layer most recently prepared on the carrier in a cross-sectional area of the model assigned to this layer the molded body with radiation, in particular focused laser radiation, which brings the material powder in this cross-sectional area to heat by melting or possibly sintering, a leveling and smoothing device for the preparation of the following material powder layer on the last irradiated layer, the leveling and smoothing device at least one smoothing slide movable at a distance corresponding to the desired powder layer thickness over the last irradiated layer to level a respective amount Material powder has a layer of the desired thickness over the last irradiated layer. The invention relates in particular to the field of selective laser melting and is based, both in terms of method and device, on a technology such as that described in, for example, US Pat DE 199 05 067 A1 , in the DE 101 12 591 A1 , in WO 98/24 574 or in the corresponding DE 196 49 865.1 although the invention is applicable to the field of laser sintering.

With the technology considered here is about a method and an apparatus for producing a Molding, e.g. a prototype of a product or component, a tool or a spare part, according to three-dimensional CAD data a model of the molded body through layered build-up of powdered, metallic or ceramic Material in which several powder layers are stacked one after the other be applied, with each powder layer prior to application the next one Powder layer with a focused laser beam in a given area, the one selected Cross-sectional area corresponds to the model of the molded body, is heated and where the laser beam corresponds to the CAD cross-sectional data of the selected one Cross-sectional area of the model or data derived from it about the each powder layer led becomes. The material powder is used in selective laser melting Binder and flux free, metallic, ceramic or mixed metallic / ceramic material powder applied and heated by the laser beam to melting temperature, the energy of the laser beam so selected is that the material powder at the point of impact of the laser beam over its entire layer thickness if possible Completely is melted. about the interaction zone of the laser beam with the metallic material powder becomes a protective gas atmosphere maintained.

The from WO 98/24 574 and DE 196 49 865.1 Known device for performing the selective laser melting has a process chamber with an inert gas inlet and an inert gas outlet on opposite sides of the process chamber. A carrier in the form of a bulb is provided in the process chamber, which supports the layer structure and can be lowered by the amount of the desired layer thickness of the next layer after irradiation of the last layer prepared, so that the layer preparation and the subsequent radiation can always take place at the same height level ,

After each completed radiation procedure a respective amount of powder is introduced into the process chamber, the newly introduced material using a leveling device in the form of a smoothing slide over the last prepared Layer after its irradiation and lowering is distributed so that one if possible flat and smooth layer with a layer thickness of, for example 0.05 mm or 0.1 mm for the next irradiation process is formed.

The quality of the preparation of the successive Powder layers in the sense of adhering to a respective predetermined one Layer thickness and the creation of a respective flat powder layer surface plays play an essential role in selective laser melting, as they Homogeneity of from the powder melted and re-solidified material of the molding affected.

When operating a device after WO 98/24 574 has shown that during the fusion of the Metal powder splashes of melted material can arise themselves on the surface place previously irradiated areas of the layer in question and cling there. This creates undesirable bumps that the preparation the next Powder layer complicate or the quality of the preparation of the next powder layer impair can. Frequently there are such bumps the measure of desired next layer thickness from the last irradiated layer upwards, see above that in layer preparation a collision between such an unevenness and the smoothing slide take place can and the preparation process must be interrupted. leveling slider known design can thereby damaged and quickly become unusable.

In the DE 199 05 067 A1 A device of the type mentioned is described, in which the leveling and smoothing device has a grinding device which fuses with an electric motor-driven grinding shaft NEN and solidified areas of the last irradiated layer can at least partially grind up and stick out unevenness.

By means of the grinding device to bumps on the surface of the fused material at least froze sanded so far that their height does not exceed the desired thickness of the next one präparierenden Powder layer extends.

In a device according to the DE 199 05 067 A1 the leveling and smoothing device comprises a powder dispenser which can be moved over the last prepared layer and releases material powder for the layer to be prepared during its movement. The powder dispenser is part of a movable layer preparator assembly. The powder dispenser has a reservoir chamber for holding material powder and a dispensing gap between the grinding tool and the smoothing slide, which opens downwards just above the surface level of the next layer to be prepared in order to allow material powder to run downwards for layer formation, which is from the The following smoothing slide is then finely distributed and leveled in the desired layer thickness. The output gap of the powder dispenser extends essentially over the entire width of the smoothing slide. The same applies to the grinding shaft in the layer preparator assembly.

The invention has for its object a To provide a device of the type mentioned at the outset for producing a shaped body, where the leveling and smoothing device a reliable preparation of the respective material powder layers in a simpler way and made possible with simpler means than before.

To solve this problem, the invention proposes that in a device with the features of the preamble of Claim 1 of the smoothing slide is designed to level and level the Powdery local fixed obstacles yield in zones can dodge.

A designed according to the invention leveling slider is inherently stiff enough to move loose material powder over its respective smoothing motion level the last irradiated layer with the desired one Powder layer thickness. If the smoothing slider hits local fixed obstacles, such as the singular small ones already mentioned above Elevations or peaks due to solidified melt splashes or the like, so he runs over them Obstacles to further smoothing movement; the smoothing slide material only in the area of the collision with the obstacle a noteworthy predominantly undergoes elastic deformation and thus the smoothing slide Can yield flexibly to obstacles in zones.

According to a preferred embodiment of the Invention is the smoothing slide or its stripping element formed from a soft elastic material. Good results have been seen with plastic materials, especially silicone achieved. In experiments with such flexible plastic smoothing slides it was found that there was occasional injury or cracking of the smoothing slide due to collisions with sharp-edged tips of solidified melt spatter in powder layer preparation can come. It has also been shown that such individuals Cracked functionality of the smoothing slide do not interfere critically because the soft elastic Plastic material has shown the tendency to crack the gap immediately to close after crack formation or to make it very small. Wear in the sense such cracks that persist for a long time Use of the smoothing slide on random Form the plastic element, can thus be a comparative long periods of use are accepted. Only if after a long time Use shows a noticeable wear on the smoothing slide a replacement of the smoothing slide respectively. For this reason, it is proposed that the smoothing slide if necessary, replaceable on a smoothing slide holder Leveling and smoothing device is arranged. The replaceable plastic element can e.g. a rod-shaped square element which is normally in a horizontal orientation on the smoothing slide holder the leveling and smoothing device is arranged. As mentioned, can the rod-shaped Plastic element have a square cross-section. Are conceivable however, other cross-sectional shapes, such as triangular cross-section or circular cross-section, in the latter case the smoothing slide In one variant, it can also be designed as a roller that can rotate is stored, but not necessarily driven by a motor got to.

On a grinding shaft like the one from the DE 199 05 067 A1 is known, can be dispensed with in the device according to the present invention, whereby the construction of embodiments according to the present invention is considerably simplified. Operation with the layer preparation is also easier with the device according to the present invention, since it is made of DE 199 05 067 A1 known step of grinding locally fixed obstacles can be omitted. In other words, this means that when operating the device according to the present invention, such local obstacles due to solidified melt splashes or the like can be tolerated because the smoothing slide is designed in such a way that it can yield to them zone by zone and yet an otherwise level and on the required thickness nivel prepared powder layer. Any small peaks of solidified melt spatter from the previous exposure step that protrude upward above this powder layer can be tolerated and melted down again in the next exposure step.

According to a further embodiment of the invention has the smoothing slide a multitude of small ones, usually close together of one carrier hanging down Powder wiping elements, each of which is flexible and resilient their normal position are deflectable to a local obstacle the layer preparation dodge. In the simplest variant of this embodiment is the smoothing slide designed like a brush, the resiliently deflectable powder stripping elements the bristles form. It can relatively short and inherently stiff bristles are provided, which at are laterally deflected when hitting an obstacle and resilient after passing the obstacle in its starting position push back. tries have revealed that such brush-like leveling slider reliable work and little wear and tear in normal operation demonstrate.

According to a development of the invention it is provided that the leveling and smoothing device one over the powder dispenser that can be moved back and forth over the last irradiated layer, the while its driving motion powder material for each to be prepared Material powder layer can give up. Such a movable powder dispenser can pre-dose the amount of powder, so that at the layer preparation the smoothing slide following the powder dispenser is at most small Has to push amounts of powder in front of him. Preferably the powder dispenser and the leveling and smoother common components of a moveable layer preparator assembly.

It can be provided that the layer preparator assembly in the direction of their normal feed movement in front of and behind the powder dispenser has a respective smoothing slide, which is designed to level and level yielding local obstacles in zones can dodge. In the latter embodiment, the horizontal reciprocating layer preparator assembly both at Travel in one direction as well as travel in the other direction preparation of a powder layer in question, the respective Smoothing slide for Effect comes in relation to the respective direction of movement follows the powder dispenser. Idle runs of the layer preparator assembly are therefore not necessary. The powder dispenser should expediently a reservoir for the inclusion of one for have several layers of sufficient powder so that refilling the Material powder during the production of a shaped body if possible is rarely required.

The invention is described below Reference to the figures in more detail explained.

1 shows a schematic partial sectional side view of an embodiment of a device according to the invention.

2 shows in a partial section representation, not drawn to scale and partly broken, of a layer preparator assembly in its operating position relative to a molded part that has already been partially completed.

3 shows in a representation according to 2 a layer preparator assembly with brush-like smoothing slides.

4 shows a perspective view obliquely from below of a specific embodiment of the layer preparator assembly.

5 shows the layer preparator assembly 4 in a perspective view obliquely from above.

6 shows in one of the 2 similar representation of the layer preparator assembly in a gap filling mode.

In 1 an embodiment of a device according to the invention is shown schematically partially in section.

Apart from the layer preparator assembly, the device has a basic structure like that in DE 199 05 067 A1 described device and comprises an outer housing 3 in which there is a horizontal support plate 5 which is the housing 3 into an upper one, the process chamber 7 containing area 9 and in a control device 13 the lower part of the device 11 divided. In the of the process chamber housing 15 with lid 17 limited process chamber 7 is the controlled vertically movable carrier 19 to support the layer structure and the resulting molded body 21 , The carrier forming an essentially horizontal support surface 19 has a vertical drive shaft on its underside 23 on by guiding the platform 5 is guided through and at its lower end via two opposing side arms 24 with a respective vertically guided linear drive 25 connected is. The linear drive arrangement 25 is from the control device 13 that have a control computer in the housing 3 includes, driven to the carrier 19 for the preparation of a respective subsequent material powder layer, preferably in order to lower the dimension of the desired layer thickness or to increase it if necessary.

At the beginning of the production of a shaped body 21 the carrier i 9 is moved in a controlled manner into a vertical starting position, the position of which in 1 with S is indicated. Then the layer preparator assembly to be explained 32 activated to on the carrier 19 to prepare a first material powder layer P of a certain layer thickness. The layer thickness is approximately 0.1 mm, for example. However, depending on the circumstances, it can be chosen larger or smaller. After completion of the first layer L, the radiation device then comes 34 used to the layer L in an associated cross-sectional area of the model of the molded body to be produced 21 in sections with a focused laser beam 36 to scan, the energy density of which is sufficient in plane S to heat and melt the powder material above the melting point, so that after solidification of the melted areas, these form a solid phase which is as homogeneously coherent as possible. The optical focusing device 40 is between the laser 38 and an XY scanner 42 with (not shown in more detail) swivel mirrors, which in accordance with the respective CAD cross-sectional data of the molded body to be produced 21 under the control of the control device 13 be moved to the laser beam 36 to lead accordingly. The optical device 34 is outside the process chamber 7 , An upper window 44 in the lid 17 of the process chamber housing leaves the laser beam 36 to the process chamber 7 step through. Preferably the window 44 with one on the wavelength of the laser 38 matched anti-reflective coating.

After irradiation of the first layer L and thus production of the first layer of the shaped body 21 then becomes the carrier 19 is lowered in a controlled manner by the measure of the desired next layer thickness and the preparation of the next layer follows, which then again corresponds to the pattern of the cross section of the shaped body assigned to this next layer 21 using a laser beam 36 is selectively fused. This procedure is then repeated accordingly until the molded body 21 is finished.

On the facing 1 recognizable back of the process chamber 7 is a protective gas distributor just above level S. 45 provided, the protective gas, preferably argon, is supplied via an external protective gas supply. On the in 1 On the opposite side, which cannot be seen, there is preferably a corresponding protective gas collector at the same height level just above the level S, which leads the protective gas to a protective gas discharge line. The protective gas discharge line is preferably connected to the protective gas inlet via a filter and a pump, so that the protective gas can be pumped in the circuit. As already described in WO 98/24 574, the protective gas serves to keep atmospheric oxygen as far as possible away from the respective melting range (interaction range between laser radiation and powder) in order to avoid oxidation processes. Which preferably extends over almost the entire width of the process chamber 7 extending protective gas distributor 45 and the corresponding counterpart designed as a protective gas collector ensure that the protective gas flow is as laminar as possible.

On the housing cover 17 is a video surveillance camera at 48 48 provided by means of which the processes in the process chamber 7 on a monitor of the control device 13 or / and on a monitor of an external computer 50 can be observed. The external computer 50 is over a network 52 with the internal computer of the control device 13 connected.

The external computer 50 serves the CAD data to describe the molded body to be produced 21 prepare and in a for the computer of the control device 13 implement the required format and the data prepared in this way to the computer of the control device 13 over the network 52 to send. It should be noted that on the calculator 50 over the network 52 further devices for molding production can be connected.

To explain the structure and mode of operation of the layer preparator assembly already mentioned 32 and especially the associated smoothing slider 68 will appear below 2 Referred.

2 shows a broken partial view of the carrier in a highly schematic sectional side view 19 with a section of the molded body being created 21 , The platform 19 is in the representation according 2 has already been reduced by the amount of the material powder layer currently to be prepared. The layer preparator assembly 32 travels over the last irradiated layer L of the resulting molded body 21 away in the direction of arrow R, with the lower edge 69 the layer preparator assembly 32 has a vertical distance S from the horizontal flat surface of the last solidified layer L and this distance S corresponds to the desired powder layer thickness currently to be prepared.

From the layer preparator assembly 32 is in 2 only the lower part with two smoothing sliders 68 to recognize. Between the two smoothing sliders 68 is the output slot - offset upwards 66 of the layer preparator assembly 32 integrated powder dispenser 62 ,

The powder dispenser 62 can hold a supply of material powder and in the in 2 recognizable way powder P over the discharge gap 66 between the smoothing sliders 68 spend downwards.

2 provides a snapshot of the layer preparator assembly 32 when moving from left to right. In this direction of movement it is the smoothness shown on the left tung slide 68 , which is currently leveling the powder P at the desired layer thickness S. After the preparator assembly 32 When the preparation of the next layer to be exposed has been completed, it can remain in a parking position on the right-hand side as long as the process of irradiating the prepared layer and the process of subsequently lowering the platform 19 take. The layer preparator assembly can then be used to prepare the next powder layer 32 are moved in the opposite direction to the previous direction of travel in order to deposit powder on the last solidified layer and to prepare a relevant layer of powder. Relating to 2 would be the layer preparator assembly 32 thus after completion and irradiation of the currently prepared layer and after lowering the carrier platform 19 then move in the opposite direction from arrow R from right to left. To smooth the powder layer, the in 2 smoothing slider shown on the right 68 be effective.

With the smoothing slides 68 of the embodiment 2 These are square silicone rods, which are aligned in the manner shown such that a respective side 69 is at the bottom and is aligned horizontally. At this point, however, it should be pointed out immediately that other profile shapes or orientations also concern smoothing slides 68 are possible within the scope of the invention. Good results have been achieved in tests, for example with horizontally oriented, elongated smoothing slide elements which at the bottom had an edge or corner, for example a triangular profile. As already mentioned, round profiles can also be used. come. It is important, however, that the smoothing slides are stiff enough in themselves so that they collide with an obstacle 55 dodge only in the area of the collision zone, but displace the metal powder placed in front of them by the powder dispenser and be able to move it so that it forms a layer in the desired manner. Such a situation is in 2 outlined. Due to a solidified melt spatter fixed to the layer L, an elevation is produced when the last solidified layer L is irradiated 55 were created, the top area of which is still above the currently prepared powder layer and thus an obstacle for the smoothing slide 68 represents. As at 71 in 2 indicated, it happens when driving over the obstacle 55 to a selective, essentially elastic reversible material displacement on the smoothing slide in question 68 which, however, is limited to the immediate collision zone, so that the smoothing slide 68 regardless of the disturbance 55 can produce a very well leveled and leveled powder layer.

The smoothing slider 68 are interchangeable on smoothing slide holders if necessary 73 attached. Since it is with the smoothing slides acting as stripping elements 68 The smoothing slides are replaced by very inexpensive elements and can be replaced with little effort 68 no problem. As already mentioned, however, it is normally not necessary to replace a smoothing slide immediately after the first narrow cracks have appeared.

3 shows the embodiment 2 in one of the 2 corresponding representation, but with other smoothing slide elements 68a , As with the embodiment according to 2 extend the smoothing slider 68a and the output gap 66 perpendicular to the plane of the drawing over a sufficient length, so that normally a preparation run over the already created part 21 of the molded body is sufficient to deposit and smooth a complete powder layer.

With the smoothing slides 68a according to 3 are elongated brush elements with bristles 75 , which in the example shown are normally vertical from a support section 77 hang down. The bristle ensemble is stiff enough in itself to move away from the gap 66 level the powder dispensed by the powder dispenser and level it to the desired layer thickness. At the 55 in 3 obstacle shown, however, can be the bristles colliding directly with it 75 dodge to return to a position at least approximately corresponding to their starting position after overcoming the obstacle.

Even the smoothing slider 68a according to 3 work reliably and are not prone to wear.

In the 4 and 5 is a layer preparator assembly of the in 2 shown type shown in more detail and removed. At the in 4 recognizable underside of the preparator assembly 32 are the exchangeable smoothing slides made of silicone 68 in the smoothing slide holders 73 arranged. These are smoothing sliders 68 in the example the 4 around square silicone bars. Between the smoothing sliders 68 is the output slit 66 of the powder dispenser 62 recognizable. The powder dispenser 62 contains agents for the metered delivery of the material powder. In the example, these dosing means comprise a dosing shaft which, depending on its respective rotational position, powders of material over the gap 66 outputs. The general structure of such a metering shaft is, for example, in 5 the DE 199 05 067 A1 shown.

With 83 is in 4 and in 5 a controllable electric motor to drive the entire length of the output gap 66 dosing shaft extending parallel to and above it 85 designated. Also recognizable in the 4 and 5 are frame elements 76 for fastening the assembly 32 of linear guide means and drive means that the assembly 32 on their preparation trip lead and drive.

In 5 is at the top of the assembly 32 the powder feed port 79 the reservoir chamber 70 recognizable. In the in 1 The left-hand parking position shown can be the layer preparator assembly 32 if necessary, new material powder from the powder reservoir 80 refuel, for example in the DE 199 05 067 A1 described way. Means are preferably provided which cover the opening 79 seal outwards when refueling material powder. This includes the in 5 partially shown seal 81 which with a counter surface of the refill station 80 comes into contact when refueling.

With reference to 6 An interesting possible use of a device of the type considered here for producing a shaped body is explained below. The use of the device relates to the closing of pores, breakouts or other undesirable hole-like structures in surfaces. 6 shows a section of a metal or ceramic body, for example, which has an upper surface 90 which is substantially flat but has 92 undesirable depressions. According to 6 become these recesses 92 filled with material powder P, this in the process chamber according to a device 1 can be done. The level of the surface 90 is aligned horizontally. The layer preparator assembly 32 passes the powder P through the discharge gap 66 downwards, so that the smoothing slider in the direction of movement R 68 the powder in the area of the wells 92 can smooth out. The bottom 69 the smoothing slide 68 is essentially at the level of the level 90 the surface of the body 21a , so that after a smoothing run of the layer preparator assembly 32 the wells 92 essentially down to the level 90 are filled with material powder P. Then comes the optical device 34 according to 1 used to the material powder in the wells 92 to merge into a coherent solid phase so that the depressions 92 have subsequently disappeared. In the in 6 outlined manner can thus have perforated surfaces of, for example, metallic or ceramic bodies 21a can be repaired using selective laser melting. These bodies can otherwise have been made in any way.

Of course, in the 6 outlined way, also in the above-described layer-by-layer production of shaped bodies, if necessary repair a respective last solidified layer. In particular, the upper surface layer that closes off the molded body can be formed in this way with a high surface quality.

In 6 is the layer preparator assembly 32 with smoothing sliders 68 the in 2 shown type shown. Of course, the smoothing slides also come 68a according to 3 for the in 6 outlined use case in question. While accepting certain disadvantages, the application can be according to 6 if necessary, rigid smoothing slides of conventional type can also be used.

The point of view of surface repair, as he explained above was of independent importance in the context of the present invention to. The applicants reserve the right to claim this.

Claims (10)

Device for producing a shaped body ( 21 ) by building up in layers from powdery, in particular metallic or ceramic material, with a carrier ( 19 ) for the layer structure, an irradiation device ( 34 ) for irradiation of the last on the carrier ( 19 ) prepared material powder layer in a cross-sectional area of the model of the molded body assigned to this layer ( 21 ) with radiation, in particular focused laser radiation, which causes the material powder to melt or possibly sinter in this cross-sectional area, a leveling and smoothing device for the preparation of the following material powder layer on the last irradiated layer, the leveling and smoothing device at least has a smoothing slide movable at a distance of the desired powder layer thickness over the last irradiated layer for leveling and leveling a respective amount of material powder over the last irradiated layer, characterized in that the smoothing slide ( 68 ) is designed so that it fixes local fixed obstacles when leveling and leveling the material powder ( 55 ) can yield flexibly in zones. Device for producing a shaped body according to claim 1, characterized in that the smoothing slide ( 68 ) is formed from a soft elastic material. Device for producing a shaped body according to one of the preceding claims, characterized in that the smoothing slide ( 68 ) is formed from a plastic, in particular silicone material. Device for producing a shaped body according to one of the preceding claims, characterized in that the smoothing slide ( 68 ) consists of at least one essentially rod-shaped plastic element that is horizontally aligned on a smoothing slide holder ( 73 ) the leveling and smoothing device is arranged. Device for producing a shaped body according to claim 1, 2 or 3, characterized in that the smoothing slide ( 68a ) a variety of small, usually close to each other from a carrier ( 77 ) powder scraper elements hanging down ( 75 ), each of which can be deflected from its normal position in a flexible and resilient manner in order to avoid a local obstacle in the preparation of layers. Device for producing a shaped body according to claim 5, characterized in that the smoothing slide ( 68a ) is designed like a brush, the flexible deflectable powder wiping elements ( 75 ) form the bristles. Device for producing a shaped body according to one of the preceding claims, characterized in that the smoothing slide ( 68 . 68a ) can be replaced if necessary on a smoothing slide holder ( 73 ) the leveling and smoothing device is arranged. Device for producing a shaped body according to one of the preceding claims, characterized in that the leveling and smoothing device comprises a powder dispenser which can be moved back and forth over the last irradiated layer ( 62 ) comprises, which can deliver material powder for the respective material powder layer to be prepared during its movement. Device for producing a shaped body according to claim 8, characterized in that the powder dispenser ( 62 ) and the leveling and smoothing device are common components of a movable layer preparator assembly ( 32 ) are. Device for producing a shaped body according to claim 9, characterized in that the layer preparator assembly ( 32 ) in the direction of their normal feed movement in front of and behind the powder dispenser ( 62 ) a respective smoothing slide ( 68 ; 68a ) that is designed in such a way that it can yield locally to local obstacles in the leveling and leveling of the material powder.