CN101422963A - Method and equipment for manufacturing three-dimensional workpiece - Google Patents

Abstract

The invention provides a method and equipment for manufacturing a three-dimensional workpiece by using an organic adhesive mixed solvent and powder; the working principle is that the raw materials are stirred into slurry, and the slurry is paved into a green compact thin layer which can be disintegrated in a disintegrating agent; scanning the green compact thin layer by an energy beam to form a workpiece thin layer which is not disintegrated in a disintegrating agent; repeating the two steps of thin layer laying and energy beam scanning in such a circulating way to form a three-dimensional workpiece; the green body, which has not been scanned by the energy beam, is separated from the workpiece by the disintegrant, leaving the desired three-dimensional workpiece. The invention is widely applicable to the manufacture of plastic, metal, ceramic and composite workpieces, overcomes the defects of the selective laser sintering method, can use fine powder, and has very thin layer thickness, so that finished products with better surface roughness and texture fineness than the traditional selective laser sintering method can be manufactured, and the metal and ceramic workpieces subjected to post-densification sintering treatment can obtain better strength than the traditional selective laser sintering method.

Description

A method and device for manufacturing a three-dimensional workpiece

technical field

The invention relates to a method and equipment for manufacturing plastic material workpieces, ceramic and plastic composite material workpieces, metal and plastic composite material workpieces, and other composite material workpieces, in particular to the use of organic binders in layered processing to produce three-dimensional A manufacturing method and equipment for plastic material workpieces, three-dimensional ceramic and plastic composite material workpieces, three-dimensional metal and plastic composite material workpieces, and other three-dimensional composite material workpieces.

Background technique

The rapid prototyping method can manufacture three-dimensional workpieces. The common methods are stereolithography (Stereolithography), selective laser sintering (Selective Laser Sintering), melt extrusion molding (Fused Deposition Modeling), thermal spraying (Thermo -Jet), wax spray modeling (Model Maker), etc., can be used to manufacture plastic workpieces. The first two methods are the illumination method, and the last three methods are the nozzle method. The illumination method is to use ultraviolet light to irradiate liquid photosensitive resin to solidify it, or use infrared light to fuse and link thermoplastic powder to form. The nozzle method is to use a nozzle to extrude or spray liquid plastic, and then solidify it after cooling down. The latest OB jetting method (OBJET) uses a composite method of nozzle and light, which uses a nozzle to spray liquid photosensitive resin and then irradiates it with ultraviolet light to cure the resin. Compared with the nozzle method, the illumination method uses laser light to shape, and has the potential to manufacture finer workpieces.

Both Stereolithography and Selective Laser Sintering, which belong to the illumination method, have their own advantages and disadvantages. Stereolithography uses photosensitive polymer liquid materials, which can lay a relatively thin (50um) layer thickness, but supports must be designed to support the protruding cantilever structure, and because the resin is irradiated with ultraviolet light, it can be more accurate and accurate. Workpieces with obvious fine features. Selective Laser Sintering uses powder as material, whether it is plastic powder, metal powder or ceramic powder, it can be processed. And when the selective laser sintering method (Selective LaserSintering) processes plastic materials, if the studio temperature is maintained at 20°C below the melting point of the powder, the temperature rise will not be high during heating, and the warping of the powder will not be serious, because the powder can support the protruding cantilever structure. No special design support is required. Because there is no supporting structure, it is only necessary to remove loose powder when lifting the workpiece.

The powder method of Selective Laser Sintering has many advantages over the liquid method of stereolithography (Stereolithography). Plastic materials do not need to be specially constructed for support, but they have a serious disadvantage, that is, the commonly used powder particles are about 50 μm, which is 1000 times larger than the liquid polymer material of stereolithography (Stereolithography) about 50 nm, because it cannot use fine ( For example, 1μm) powder, and it belongs to the dry powder manufacturing method, dispersant cannot be used, and the workpiece made is difficult to achieve 95% compactness, and because fine (such as 1μm) powder cannot be used, the layer thickness should not be too thin (The existing technology is about 75um or more), and the workpieces made are less detailed. These two shortcomings limit the scope of use of the selective laser sintering method.

The inventors of the present invention created ceramic high-energy beam sintering method (US Patent No.6217816, China Taiwan Patent No. I228114). A thin layer of slurry is laid on the slurry through the feeding equipment, and after drying into raw materials, the raw materials are selectively scanned by high-energy beams immediately, and directly sintered into ceramics. Such repeated actions complete the 3D workpiece, and then disintegrate the raw and damaged parts that have not been sintered by the high-energy beam, and then take out the ceramic workpiece. This method can be called the ceramic high-energy beam melting method. Ceramic workpieces can be made directly on the rapid prototyping machine without post-sintering. Subsequently, a high-energy beam sintering method (China Taiwan Patent No. I272261) was created to produce 3D ceramic material workpieces and 3D ceramic gold material workpieces based on the principle of liquid sintering; it is to mix ceramic powder with inorganic binders and diluents, and stir them into a slurry. Pave a thin layer of slurry, heat and dry, and the ceramic particles in the slurry are connected to each other by the bonding of inorganic adhesives to generate strength and become a green body. The green body is quickly scanned with a high-energy beam to melt the inorganic binder at a temperature below the melting point of the ceramic powder with the highest melting point to produce a bonding effect. In addition to producing an extremely thin sintered layer, it can also be made more delicate than the sintering method. surface. These two patents can use inorganic binders to make ceramic and pottery gold workpieces, but they cannot be widely used in the manufacture of plastics, metals, ceramics and composite workpieces like the selective laser sintering method.

Contents of the invention

In order to overcome the deficiencies of the prior art, the present invention provides a manufacturing method and equipment for a three-dimensional workpiece.

The technical solution adopted by the present invention to solve the technical problem is to provide a manufacturing method of a three-dimensional workpiece, comprising the following steps: (1) mixing the powder with an organic adhesive and a solvent to make a slurry; (2) mixing the above-mentioned The slurry is spread into a thin layer of slurry in a limited area, and the thin layer is hardened due to the volatilization of the solvent; (3) The above-mentioned hardened thin layer is scanned with an energy beam according to a specific path, so that the scanned (4) Repeat steps (2), (3) to a predetermined number of times to produce a predetermined number of stacked layers, and these The stacked layers are connected to each other when being scanned by the energy beam in step (3) to form the shape of the three-dimensional workpiece; and (5) removing the hardened block that has not been sintered by the energy beam scanning from around the sintered three-dimensional workpiece to obtain the three-dimensional workpiece.

Another embodiment is as follows, providing a method for manufacturing a three-dimensional workpiece, comprising the following steps: (1) mixing the powder with an organic adhesive and a solvent to form a slurry; (2) placing the slurry in a limited area A thin layer of slurry is laid inside, and the thin layer is hardened by the volatilization of the solvent; (3) The above-mentioned hardened thin layer is scanned by an energy beam according to a specific path, and the scanned area on the above-mentioned thin layer is heated and sintered Become metamorphic thin layer, this metamorphic thin layer comprises workpiece part and supporting part, and workpiece part has the cross-sectional shape of three-dimensional workpiece; (4) repeat step (2), (3) to predetermined number of times, and make predetermined quantity stacked layers, and these stacked layers are connected to each other when being scanned by the energy beam in step (3), forming the shape of the three-dimensional workpiece and the shape of the support; and (5) sintering the hardened block and the support structure without energy beam scanning The periphery of the sintered three-dimensional workpiece is removed to obtain a three-dimensional workpiece.

The present invention also provides a device for manufacturing a green body block containing a three-dimensional workpiece by using a slurry containing an organic binder, powder, and solvent, including: a device for manufacturing a green body thin layer, including a thin layer laying device and a working platform; the thin-layer laying device moves relative to the worktable at a certain distance, and spreads the slurry on the worktable to form a thin layer of slurry, and the thin layer can be dried by the organic binder that links the powder. and hardened into a green thin layer; the workbench supports the thin layer; also includes an energy beam sintering device, including an energy beam generating device, and an energy beam scanning device; wherein the energy beam scanner guides the energy beam in the aforementioned The green thin layer moves along a specific path, so that the area of the green thin layer scanned by the energy beam is heated up and sintered into a workpiece thin layer.

The first step of making a three-dimensional workpiece in the present invention is to mix powder (plastic powder, ceramic powder, metal powder or composite powder) with solvent (water or organic solvent) and organic binder to prepare slurry. The characteristic of the slurry is that the green body made by it can be disintegrated by the disintegrating agent, and the green body is not disintegrated in the disintegrating agent after being irradiated by the energy beam in step (3) and sintered. This slurry can be spread in thin layers. When the thin-layer slurry is dried in a proper way, the particles in the slurry are connected to each other by the gluing of the organic adhesive, resulting in a solid green thin layer with strength. The green thin layer is selectively scanned by an energy beam, and the scanned part can be transformed into an extremely thin workpiece thin layer that does not disintegrate in the disintegrating agent. Below the thin layer of the workpiece is still a thin layer of unmodified green body. The green body forms a solid support sufficient to prevent thermal deformation of thin layers of the workpiece caused by energy beam scanning. Such repeated actions complete the 3D workpiece, and then place the workpiece in a disintegrant to disintegrate the green body that has not been scanned by the energy beam to obtain the desired three-dimensional workpiece.

If the solid support formed by the part of the green body that has not been scanned by the energy beam is not enough to prevent the thermal deformation caused by the energy beam scanning, the thin layer of the workpiece above and the thin layer of the green body below may be separated, resulting in warping, then Structural support should be specially added to the green part to connect with the thin layer of the workpiece to prevent the thin layer of the workpiece from warping.

Manufacturing method of the present invention comprises four steps:

(1). Preparation of slurry;

(2). Manufacture green thin layer;

(3). Energy beam sintering green body thin layer into workpiece or workpiece plus structural support;

(4). Remove unsintered green body or green body plus structural support.

Here, the methods and equipment related to each step in the manufacturing method of the present invention will be discussed first.

Step 1: Prepare raw materials

In this step, powder 1a is mixed with solvent 1b and organic adhesive 1c to prepare slurry 2 .

Powder 1a refers to plastic powder, ceramic powder, metal powder or composite powder containing two or more materials (including ceramic/metal composite powder, plastic/ceramic composite powder, plastic/metal composite powder, etc.).

The solvent 1b is water or an organic solvent such as methyl ethyl ketone (MEK), toluence, etc. Its function is to dissolve the organic adhesive 1c so that it can be mixed with the powder 1a uniformly, and the viscosity of the slurry 2 can be adjusted.

The organic adhesive 1c is a water-soluble organic adhesive such as polyvinyl alcohol (PVA), starch, cellulose (Cellulose), or a water-insoluble organic adhesive such as polyvinyl butyral (PVB). Its property is that it can be dissolved in the solvent 1b, and after being mixed with the powder, the powder can be connected into a green body after being dried, but the green body can be immersed in the disintegrating agent 14 to disintegrate, and the green body can also be scanned and sintered by the energy beam 10. The workpiece that has deteriorated into a disintegrating agent 14, and the green body that has not been scanned by the laser can be used to support the workpiece; thus, the disintegrating agent 14 can be used to remove the green body supporting the workpiece in the fourth step.

Polyvinyl alcohol (PVA) is soluble in water, mixed with ceramic powder and dried to form a green body. The green body can be immersed in water and disintegrated, but the water resistance of the green body will be improved after heating and melting, so Polyvinyl alcohol is suitable as the organic adhesive 1c of the present invention, and can be used to connect plastic powder, metal powder or ceramic powder to make three-dimensional workpieces according to the manufacturing method of the present invention. However, other water-soluble binders such as cellulose do not improve the water resistance much after heating and melting, so although the cellulose and ceramic powder are mixed and dried to form a green body, the green body can also be immersed in water and collapse. However, the water resistance of the green body does not change much after heating and melting, and it will also disintegrate when immersed in water. Therefore, there is no proper way to separate the workpiece from the green body to form the workpiece made of cellulose-linked metal powder or ceramic powder.

However, the workpiece made of polyvinyl alcohol linked with acrylic coated metal powder or acrylic coated ceramic powder can be separated from the green body and formed by immersing in water. Acrylic (PMMA) is insoluble in water, and acrylic latex for paint contains acrylic particles dispersed in water. Acrylic latex can form a film at room temperature, and the formed acrylic film has waterproof properties. If acrylic (PMMA) is used to coat the surface of ceramic powder or metal powder, a water-insoluble film can be formed. The green body made of polyvinyl alcohol linked with acrylic-coated metal powder or acrylic-coated ceramic powder can disintegrate the green body if placed in water; but when the green body is irradiated by the energy beam 10, the powder surface The acrylic (PMMA) film and the adjacent polyvinyl alcohol are melted and mixed to form a water-insoluble composite material, so the workpiece made by this method is insoluble in water, and it is quite easy to remove the green support with water.

The above three materials (powder 1a, solvent 1b and organic adhesive 1c) are mixed in an appropriate proportion, placed in a stirring device 3 or a conventional ball mill and uniformly stirred to obtain a suitable slurry 2 .

In order to make the powder suspend, improve the uniformity of the slurry, increase the content of the powder, reduce the viscosity, and reduce the air bubbles, other additives 1d can be added to the slurry, such as dispersant (ammonium polyacrylate), defoamer, light absorbing agent, etc. , and implement two-stage treatment, first add the dispersant to disperse the powder and then add the binder 1c.

Step 2: Fabrication of Green Thin Layers

Making the green thin layer is to spread the prepared slurry 2 into an extremely thin layer of slurry thin layer 7, and make it dry and harden. This hardened thin layer is called green thin layer 9. For this purpose, first of all, the green sheet 9 must be produced by means of a green sheet production device 16 . The thin layer manufacturing equipment 16 includes a thin layer device 4 and a workbench 6 . Some of the solvent 1b in the slurry 2 can volatilize at normal temperature, and some need to add a heater 8 to rapidly heat the thin layer of slurry 7 to harden it.

If the slurry 2 flows by gravity, then the simple container can be the thin-layer device 4, and the slurry 2 flows out from the outlet of the thin-layer device 4, and the thin-layer device 4 and the workbench 6 move relative to each other at a certain distance. The slurry 2 can be spread into a thin layer 7 of the slurry on the green block 5 by scraping with a simple scraper 20 . But because most of the slurry 2 has high viscosity and is not easy to flow, a pressurizing device, such as a screw mechanism 18, can be used to provide delivery pressure, and the slurry 2 is extruded through most of the small holes on the rectangular outlet end of a batcher 19; 19. The length of the outlet edge is approximately equal to the wide side of the slurry thin layer 7, so the extruded slurry 2 forms a long line; The gap allows the scraper 20 to move in the long-side direction of the slurry thin layer 7 to scrape the long line of slurry to form the shape of the slurry thin layer 7 . Furthermore, it is also possible to connect a circular flexible pipe with an outlet after the pressurizing equipment, and the extruded slurry 2 is dotted, so that the circular flexible pipe can do the linear movement in the direction of the wide side of the slurry thin layer 7, then The extruded slurry will form a long line, so that its length is equal to the broadside of the slurry thin layer 7, and then a scraper 20 is used to scrape the long line slurry to move in the direction of the long side of the slurry thin layer 7. The shape of the slurry thin layer 7 is formed. When utilizing the above-mentioned green body thin layer manufacturing equipment 16 to form the shape of the slurry thin layer 7, the slurry must be evenly coated on the green body block 5 and pressurized so that the slurry thin layer 7 is connected with the lower layer of green body and the green body is controlled. The density of the billet. The thin-layer device 4 has this function, and it includes a feeding device for quantitatively delivering the slurry 2 to the top surface of the green block 5 , and a film-making tool that can apply a certain pressure on the thin layer of slurry 7 . The method of laying the slurry into a thin layer in a limited area is the rolling rolling method, the sliding scraping method and the scraper forming method. The film-making tools they use can be rollers, splitting plates, and scrapers. The roller is the film-making tool of the rolling rolling method; the rolling rolling method is to apply pressure to the rolling wheel to roll the slurry. After the slurry is compressed, it flows from the pressure point to the lower pressure point, which has the effect of reducing thickness and compacting. The splitting plate is a film-making tool of the sliding scraping method; the sliding scraping method is to apply pressure to a splitting plate and push the splitting plate forward at the same time, because the splitting plate and the slurry surface form a small angle , The aforementioned action of the splitting plate has the triple effect of compacting, sliding and smoothing the paste ingredients. The scraper is the film-making tool of the scraper forming method; the material is spread by the scraper forming method, although only the scraper 20 is used, and no special pressurizing tool is used, but if the fine enough powder is used together, the effect of compressing the powder will be achieved. When material 2 is dried, capillary pressure will be generated to make the powders approach each other and increase the density. For example, when the particle size of the powder is 0.35 μm and 0.68 μm, the maximum stress generated is about 2 MPa and 1.1 MPa respectively.

The workbench 6 for manufacturing green thin-layer equipment 16 may include a workpiece seat 21 and a lifting platform 22. The workpiece seat 21 carries the green block 5 and the workpiece 12, and the lifting platform 22 carries the workpiece seat 21 for vertical movement.

Must use thrust when coating slurry 2 with scraper 20, may make the workpiece thin layer 11 of lower layer move, cause upper and lower layer workpiece section to be unable to align, the workpiece size of making is incorrect. If the solvent 1b in the slurry thin layer 7 volatilizes, the organic binder 1c connects the powder 1a to form a green body with considerable strength, which can withstand the thrust when the upper layer of slurry 2 is coated, and the lower workpiece thin layer 11 will not move. Then this problem can be solved. In the manufacturing method, before the thin layer of slurry 7 is scanned by the energy beam 10 in a specific path, it is heated in advance, so that it can be quickly dried and hardened, and the working speed is accelerated. The heating method can be heated from above the green block 5 or from below the green block 5; the energy can be directly added to the thin layer of slurry 7 by radiation heat transfer from above the green block 5, which can quickly harden the thin layer of slurry 7 , can be heated by microwave, infrared, etc.; experiments show that the use of far-infrared rays (wavelength above 6 μm) has a good effect; from the top of the green block 5, the energy is added to the thin layer of slurry 7 by convective heat transfer and hot air, and it can also be quickly The thin layer of slurry 7 is hardened. The green body 5 is directly heated by the electric heating wire under the workpiece seat 21 by conduction heat transfer, and the effect is good on the green body 5 with a small thickness, and because the entire green body 5 stores heat, the drying is extremely fast. These heating methods can be realized by using heaters such as infrared heaters, microwave generators, hot fans, and electric heating wires.

The third step: the energy beam scans the green body and sinters to form a thin layer of the workpiece

The energy beam sintering equipment includes an energy beam generating device and an energy beam scanner. When the energy beam 10 emitted from the energy beam generating device irradiates the green body thin layer 9, the energy beam 10 interacts with the green body material on the surface to generate heat, and the heat is conducted to the inside through the surface, which can make the green body of a certain depth and width Billet deterioration. By adjusting the parameters of the manufacturing method to control the depth and width of material deterioration, the scanned areas can be linked to each other. The energy beam scanner guides the energy beam 10 to move along a specific path on the green thin layer 9. Points overlap each other to form a line, lines overlap each other to form a plane, and planes overlap to form a three-dimensional Workpiece 12.

When the energy beam 10 irradiates the green thin layer 9, it usually causes the temperature difference between the surface and the inside, resulting in different shrinkage. During cooling, the cooling rate of the outer surface is faster than that of the inner layer, which is prone to buckling. In the present invention, because there is a binder between the powders, if the sintering temperature does not burn the organic binder in the workpiece thin layer 11, usually the lower green block 5 and the upper workpiece thin layer 11 can be well connected without warping , so there is no need to build structural supports in particular. However, if the sintering temperature is high, for example, ceramic powder can be sintered, the organic binder in the workpiece thin layer 11 will be burned, and the upper workpiece thin layer 11 will be separated from the lower green body 5, resulting in warping At this time, a special structural support should be added to the green part. The sintering parameters of this structural support are the same as those of the thin layer 11 of the workpiece. The ceramic powder is also sintered. The experimental results show that the structural support and the thin layer 11 of the workpiece are connected. Buckling of the thin layer 11 of the workpiece can be prevented.

If the green body uses PVA as the organic adhesive 1c to bond the powder 1a, the laser beam 26 scans and heats to melt the PVA, and after solidification, the PVA can be changed to be insoluble in water, so the thin layer 11 of the workpiece scanned by the laser beam 26 has insoluble properties. However, the organic adhesive 1c of the green body thin layer 9 that has not been scanned by the laser is still the original water-soluble PVA; thus, the workpiece 12 scanned by the laser beam 26 is similar in nature to the raw material that has not been scanned by the laser beam. The compact 5 is different, water can be used as the disintegrating agent 14 to disintegrate the green compact 5, and the shape of the workpiece 12 scanned by the laser beam 26 can be preserved.

Such as coating acrylic (PMMA) on the surface of ceramic powder or metal powder, when the energy beam 10 scans the PMMA film coated on the powder surface, the PMMA and the adjacent PVA binder melt simultaneously, and the mixture solidifies after cooling to form an insoluble The PMMA/PVA composite material of water, because PMMA is insoluble in water originally, so this composite material just possesses better water resistance, can make stronger workpiece thin layer 11.

Commonly used CO2 laser beams and Nd:YAG laser beams are the energy beams 10 of the present invention. Different powders 1a have different absorption rates for CO2 laser beams and Nd:YAG laser beams, and organic adhesives 1c have different absorption rates for different laser beams 26. The present invention mainly utilizes the melting of organic adhesives 1c to bond powders 1a, If the absorption rate of the organic adhesive 1c and the powder 1a is not high for special lasers, a light absorbing agent can also be added to achieve the effect of melting the organic adhesive 1c at an elevated temperature. The absorption rate of the beam is not high, so the light absorption effect of the acrylic coating ceramic powder is not good, you can add carbon black into the slurry 2, and the carbon black absorbs light and heats up and transfers the heat to the acrylic to heat up and melt to connect the ceramic powder .

Mask-type projection device, which utilizes the visible light source to pass through the mask to image the profile image of the workpiece on the green surface through the optical system. The mask can be penetrating, such as a general projection film or a liquid crystal mask, or It can be reflective, such as the microlens mask of Texas Instruments, which can withstand higher energy density, and the processing and production speed of the green body can be faster by using a mask-type projection device to irradiate the green body. The energy beam scanning device may also include a beam moving device and a beam focusing device. The relative movement between the energy beam 10 and the green body 5 in the X-Y direction may be that the green body 5 moves while the energy beam 10 is stationary, or that the energy beam 10 moves while the green body 5 is stationary. The X-Y direction movement of the energy beam 10 can be realized by using a galvanometer scanner (Galvometer) or an X-Y table 29 (X-Y table), and these two technologies are very mature. Energy beam focusing mirror 36 can be a lens or a face mirror

The vertical relative movement between the energy beam 10 and the green body 5 may be that the green body 5 moves while the energy beam 10 is stationary, or it may be that the energy beam 10 moves while the green body 5 is stationary.

Using the commonly used CAD\CAM software package can automatically create a vector-based scanning path. First, use the three-dimensional drawing software to draw the three-dimensional image of the workpiece, and then cut it into many parallel sections, and then create the NC program for each section. , transforming the difficult three-dimensional processing problem into a simple two-dimensional processing method, avoiding the processing dead angle problem often encountered in three-dimensional processing.

The main manufacturing method parameters for the energy beam 10 to scan the green thin layer 9, taking the laser beam 26 as an example, are power and scanning speed. The power required by this manufacturing method depends on the photothermal conversion efficiency. Scanning the silicon oxide ceramic green body with a high-efficiency C02 laser beam has the ability to melt the organic adhesive 1c at a power above 3W. The setting of the scanning speed is also closely related to the properties of the material. For example, materials with high melting point, thick melting layer and low thermal conductivity require a lower scanning speed.

After each section of the workpiece is sintered, the distance between the green body block 5 and the laser beam 26 is expanded, and a space of one layer thickness is vacated for laying a thin layer of slurry 7 again.

Step Four: Removal of Unsintered Green Body

Repeat the aforementioned two steps of manufacturing green body thin layer 9 and energy beam 10 to scan green body thin layer 9 and sinter to form workpiece thin layer 11 for many times, and workpiece 12 can be made. This workpiece 12 is embedded in the hardened green body block 5 and must be The workpiece 12 can only be obtained by removing the green block 5 surrounding the workpiece.

The method of removing the hardened blocks and supporting structures that have not been sintered by energy beam scanning is soaking the disintegrating agent 14 or destroying with force, or immersing the disintegrating agent 14 and destroying with force. It is very effective to remove the green body and support structure with ultrasonic vibration force, especially when the workpiece is placed in the disintegrant 14 and the effect of ultrasonic vibration is better.

The region forming the workpiece 12 has the property of not being disintegrated by the disintegrating agent 14 as described in the previous step, but the region of the unsintered green body 5 can be disintegrated by the disintegrating agent 14 . The disintegrant 14 can be water, organic solvent, strong acid or strong base.

Polyvinyl alcohol is soluble in water, so water can be used as a disintegrant14. When polyvinyl alcohol is used, when the green body 5 of the organic adhesive 1c is immersed in water, it will disintegrate due to the dissolution of polyvinyl alcohol in water. Whether the workpiece 12 is connected to powder by laser melting PVA, or laser melting PVA and PMMA coated on the surface of the powder to connect powder, the original shape can be retained when placed in water. After the sintering is completed, the unsintered green block 5 together with the workpiece 12 is placed in a green body removal container 13. Putting water in the container, or washing with water beams or adding ultrasonic vibration, can remove the green body. The purpose of the compact 5.

In addition, a strong base, such as sodium hydroxide (NaOH) aqueous solution, can also be used as the disintegrant 14 . Utilizing the characteristics that polyvinyl alcohol is easily soluble in sodium hydroxide but PMMA is insoluble in sodium hydroxide, the green body made of the slurry system of PVA binder and PMMA coated ceramic powder can be made into PVA as the linking phase and PMMA coated The ceramic powder is a dispersed phase, which disintegrates when placed in sodium hydroxide. The part of the workpiece that has been scanned by laser can be made into PMMA as the linking phase, and PVA and ceramic powder are both dispersed phases, which will not disintegrate when placed in sodium hydroxide.

When the present invention compares with other conventional technologies, such as selective laser sintering, it has the following characteristics and advantages:

1. The present invention is characterized in that materials are joined by two different joining mechanisms of cementation and heating and melting. First connect a layer of plastic granules, ceramic granules, metal granules or composite material granules with an organic adhesive to form an extremely thin, simple-shaped thin-layer green body. Thin-layer green body, connecting part of the green body into a certain cross-sectional shape of the finished product, the properties of the sintered thin layer formed by energy beam scanning are different from the green body, and will not dissolve in the disintegrant, so it can be immersed in the disintegrant In the disintegrating agent, the green body is partially disintegrated and separated from the workpiece part, and no trace is left on the workpiece after the green body is removed.

2. The present invention uses a slurry, which is a mixture of powder and water, wherein the size of the powder can be mm level, μm level, or a mixture of different levels of the aforementioned. Therefore, when laying layers in the present invention, the lower limit of the thickness of the laying layer will not be limited because the powder particles are too large, and a very thin laying layer can be laid out, which reduces the step effect of the laying layer. In addition, after the slurry is laid, it is heated and dried to form a hardened green body. When laying the slurry on the hardened green body, if the thickness of the layer is thinner, the greater the force must be applied to the layer, and the green body will also be affected. The greater the force, but the organic adhesive cemented green body used in the present invention naturally forms a solid support when constructing the workpiece, and the green body can resist the force generated during the layup during production, and the workpiece and the green body will not be affected by the layup. Therefore, the present invention can reliably lay extremely thin slices. According to experiments, the thickness of the present invention can reach about 10 μm, so that the vertical axis resolution of the workpiece produced by the present invention can be higher than that of conventional methods.

On the contrary, the existing selective laser sintering method uses dry powder as the material. If the powder particles are large, such as greater than 30 μm, it is easy to flow and flatten, but when the powder particles are small, such as less than 20 μm, it is difficult to flow and scrape. Therefore, the particles that can be processed by the method cannot be too small, so the pavement layer cannot be too thin.

3. When the high-energy beam scans, a temperature gradient is formed on the workpiece, which will generate thermal stress during cooling and cause the workpiece to warp upward and deform. The green solid support of the unique organic adhesive cemented by the present invention can prevent the workpiece from deforming, and this function is especially required in the construction part of the workpiece cantilever. Because the workpiece will not warp upward, it will not touch the workpiece when making the next layer, and can be processed smoothly.

4. The slurry of the present invention is a mixture of water and powder. A dispersant can be added to disperse the fine powder evenly, and a capillary force is generated when the water or organic solvent evaporates. When the powder particles are fine, the capillary force increases and can be compacted Powder, to increase the density of the green body. The traditional selective laser sintering method uses dry powder, which lacks the aforementioned functions, and the workpiece made is difficult to be dense.

5. Because the slurry layer can be laid into a very thin layer, the step effect is reduced, the resolution in the vertical direction of the workpiece is increased, and the surface texture of the workpiece is more detailed; and the use of the slurry layer can use fine The powder can improve the surface roughness. According to the experiment, the surface roughness of Ra=1.5μm can be achieved. The two aforementioned features reduce the necessity for subsequent machining of workpieces produced by the invention.

6. The powder of the present invention may be plastic powder, ceramic powder, metal powder or composite powder. Due to the use of organic binders, the organic polymer/ceramic composite workpieces and organic polymer/metal composite workpieces formed by the present invention can use conventional burn-out organic polymer materials, high-temperature densification sintering or doping with low-melting point materials and other technologies to obtain high-strength ceramic workpieces and metal workpieces.

Combining the above features and advantages of the present invention, it can be seen that the present invention can be widely applied to the manufacture of plastics, metal and ceramic workpieces, and eliminates the shortcomings of traditional powder methods, such as selective laser sintering, and can use fine powder, layer thickness It can be very thin, so it can produce finished products with better surface roughness, texture fineness, and strength than traditional powder methods, such as selective laser sintering, which reduces the necessity of subsequent mechanical processing. Therefore, the present invention can be applied in industry, and has novelty and progress.

The purpose of the present invention is to provide a manufacturing method and equipment for three-dimensional workpieces, which can be widely used in the manufacture of plastics, metals, ceramics and composite workpieces, and eliminate the shortcomings of selective laser sintering, and can use fine powder, layer thickness It can be very thin, so it can make finished products with better surface roughness and texture fineness than the traditional selective laser sintering method, and the metal and ceramic workpieces that have been densified and sintered can be obtained better than the traditional selective laser sintering method. The sintering method is the best strength.

Description of drawings

1A to 1I are schematic diagrams of the production process of the present invention.

Fig. 2A shows the assembly diagram of three-dimensional workpiece rapid prototyping machine according to the present invention

Figure 2B is an exploded view of the ceramic rapid prototyping machine

Fig. 3 is a block diagram of the control system architecture of the three-dimensional workpiece rapid prototype machine.

Detailed ways

The following content is a further detailed description of the present invention in conjunction with specific preferred embodiments, and it cannot be assumed that the specific implementation of the present invention is limited to these descriptions. For those of ordinary skill in the technical field of the present invention, without departing from the concept of the present invention, some simple deduction or replacement can be made, which should be regarded as belonging to the protection scope of the present invention.

Description of main component symbols in Figure 1-Figure 3

1a, powder; 1b, solvent; 1c, organic adhesive; 1d, additive; 2, slurry; 3, stirring device; 4, laying thin layer device; 5, green block; 6, workbench; 7, slurry Thin layer; 8. Heater; 9. Green thin layer; 10. Energy beam; 11. Workpiece thin layer; 12. Workpiece; 13. Green body removal container; 14. Disintegrant; 15. Rapid prototyping machine; 16 17. Energy beam sintering equipment; 18. Screw mechanism; 19. Batching device; 20. Scraper; 21. Workpiece seat; 22. Lifting platform; 23. Rack; 24. Reciprocating mechanism; 25 , CO ₂ laser machine; 26, laser beam; 27, mirror; 28, convex lens; 29, XY table; 30, heating motion controller; ; 33. XY table controller; 34. Heating temperature controller; 35. Laser controller; 36. Manufacturing method computer manufacturing method manufacturing method embodiment

Please refer to shown in Fig. 1, place the aluminum oxide powder (powder 1a), water (solvent 1b), polyacrylamine (additive 1d) coated with PMMA in the stirring device 3 and mix and stir in an appropriate ratio, and the aforementioned coating Disperse PMMA-coated alumina powder in water, then add an appropriate amount of PVA (organic adhesive 1c), stir well to make slurry 2 (Fig. 1A); put slurry 2 into thin layer device 4 and extrude it onto On the green block 5 (Fig. 1B), and move the thin layer device 4 to lay the slurry 2 on the top surface of the green block 5 to form a thin layer of slurry 7 (Fig. 1C), and then use the heater 8 to apply infrared energy to the On the slurry thin layer 7, heat it up (Fig. 1D), dry and harden to form a green thin layer 9, which has high water solubility; the thickness of the first layer of green body can be thicker, about 1mm, and then The green thin layer 9 is covered on the previous layer, and the thickness should be reduced as much as possible, about 30 μm, so that the fine part shape of the workpiece can be made; thereafter, the green thin layer 9 is irradiated with an energy beam 10 [ Fig. 1E], make it absorb heat and heat up, make the PMMA film on the aluminum oxide surface below the surface to a certain depth (for example 45 μ m) and be used as two kinds of organic materials of polyvinyl alcohol as binder 1c to melt, link the aluminum oxide powder, A water-insoluble workpiece thin layer 11 is formed; the travel path of the laser beam 26 is automatically created by a computer program according to the profile of the three-dimensional workpiece to be formed, and a two-dimensional thin layer of any shape can be produced by controlling the scanning path of the laser beam 26. profile. Since the laser beam 26 scans the plane vertically from top to bottom, any point on the surface of the green thin layer 9 can be irradiated, and any complex object has no problem of processing dead ends; The distance is equal to the thickness of each workpiece thin layer 11 (for example, 30 μm) [FIG. 1F]; repeating the process from step B to step F repeatedly can stack the workpiece thin layers 11 required for the three-dimensional workpiece sequentially [FIG. 1G]. Finally, the green body block 5 containing the workpiece 12 is taken out and placed in the green body removal container 13 (Fig. 1H), and the water (disintegrant 14) in the green body removal container 13 causes the green body block 5 covering the workpiece 12 to collapse. solution, the three-dimensional ceramic/plastic workpiece 12 (Fig. 1I) to be made can be obtained.

The ceramic/plastic composite workpiece made by this manufacturing method can be post-processed, for example, the organic matter is first burned off and then sintered at 1600° C. for one hour to obtain an alumina ceramic workpiece with a density of more than 95%.

device embodiment

The manufacturing method of the present invention includes four steps. The first step (preparation of slurry) can use conventional stirring device 3 . The fourth step (removal of unsintered green body or green body plus structural support) can use a conventional container 13 for liquid (disintegrant 14) for removal of unsintered green body 5 or use a container Ultrasonic device slot for disintegrating agent 14 for removing green body block 5 and its contained structural support. The second step (manufacturing green thin layer) and the third step (energy beam sintering green thin layer into workpiece or workpiece plus structural support) must be repeated many times, it is necessary to develop tools and mechanisms, and use computers to control all work . The equipment for performing these two steps is the device for manufacturing three-dimensional workpieces of the present invention, which is called rapid prototyping machine 15, please refer to Fig. 2 and Fig. 3 .

FIG. 2A shows a combination diagram of a three-dimensional workpiece rapid prototyping machine 15 according to the present invention. This machine includes two parts: green thin-layer manufacturing equipment 16 and energy beam sintering equipment 17 .

FIG. 2B is an exploded view of the rapid prototyping machine 15 , showing the shapes and relative positions of various components. Each important component of this equipment moves according to the working method shown in Fig. 1B to Fig. 1F.

The green thin-layer manufacturing equipment 16 is mainly composed of a thin-layer device 4 , a workbench 6 and a heater 8 . The thin-layer device 4 includes a feeding device and a film-making tool. The feeding device includes a screw mechanism 18, a batcher 19 and related motion mechanisms, and the film-making tool is a scraper 20. The slurry 2 is pumped out by the screw mechanism 18, passed through the outlet of the batcher 19, extruded and falls on the top surface of the green block 5, forming a long strip. The scraper 20 is installed behind the batcher 19, and there is a gap between the bottom of the scraper 20 and the top surface of the green block 5. After the batcher 19 is unloaded, it moves together with the scraper 20, and the scraper 20 will fall on the top surface of the green block 5. Slurry 2 is scraped off. Changing the height of the gap between the bottom of the scraper 20 and the top surface of the green block 5 can adjust the thickness of the slurry thin layer 7 .

The workbench 6 includes a workpiece seat 21, a lifting platform 22 and related motion mechanisms. The workpiece seat 21 is placed on the lifting platform 22, and its function is to load the green body block 5 and the workpiece 12; after each green body thin layer 9 is manufactured and the workpiece thin layer 11 is sintered with the energy beam 10, the lifting platform 22 is downward Move the distance of one thin layer thickness to continue work on another layer.

The infrared heater 8 is installed between the frame 23 and the workpiece seat 21, and a reciprocating mechanism 24 is used to extend into the top of the workpiece seat 21 when the manufacturing method needs to be heated and dried, so that the infrared energy is irradiated on the slurry thin film in the form of radiation heat transfer. Layer 7 on top, allowing it to dry and harden quickly.

The energy beam sintering equipment 17 includes two parts: an energy beam generating device and an energy beam scanning device. The energy beam generating device generates a laser beam 26 for the _CO2 laser machine 25, and converts electrical energy into light energy. The energy beam scanning device includes an energy beam light guiding device, an energy beam focusing device and an energy beam moving device. The energy beam light guiding device is a reflector 27, and the direction of the laser beam is changed by one fixed and two moving reflectors 27, so that the scanning of the two-dimensional plane can be performed. The energy beam focusing device is a convex lens 28 . The energy beam moving device is an XY worktable 29, and the XY worktable 29 guides the focused laser beam 26 to move along a specific path on the XY plane according to the instructions of the numerical control program, and irradiates the powder in the green body to connect them to form the workpiece. Profile shape.

FIG. 3 is a block diagram of the control system architecture of the three-dimensional workpiece rapid prototyping machine 15 . The action of the rapid prototyping machine 15 is controlled by the heating motion controller 30, the thin layer device controller 31, the lifting platform controller 32, and the X-Y worktable controller 33; the energy required for drying is controlled by the heating temperature controller 34. The laser controller 35 regulates the on and off, power and pulse frequency of the laser light necessary for sintering. The sequence of these actions is controlled by a manufacturing method computer 36 . The manufacturing method computer 36 is a personal computer, which cuts the three-dimensional workpiece solid model drawn by three-dimensional drawing software such as PRO/E into multi-piece two-dimensional sections with the set accuracy, converts it into an NC program, and then starts three-dimensional processing. For workpiece production, first order the thin-layer device controller 31 of the thin-layer device 4 to discharge the material onto the top surface of the green block 5, and then the scraper 20 starts to move according to the set speed of the thin-layer device controller 31, and acts on the slurry to form a thin layer 7 of slurry. The heating motion controller 30 of the heater 8 accepts the instruction of the manufacturing method computer 36 during heating and drying. A reciprocating mechanism 24 extends the heater 8 into the top surface of the block 5, and irradiates infrared energy on the slurry thin layer 7. On the surface, make it quickly dry and harden to form a green thin layer 9, the energy of infrared radiation is regulated by the heating temperature controller 34; then coordinate the laser controller 35 and the X-Y table controller 33 to use the laser according to the instructions of the NC program code The beam 26 scans the green sheet 9, which is sintered to form the workpiece sheet 11. After scanning, notify the elevator controller 32 to lower the elevator 22, and then continue to make the next section until the finished product is completed.

The present invention includes various modifications of the present invention as long as the modifications are within the scope of the stated claims and their equivalents.

Claims (40)

1, a kind of manufacturing method of three-dimensional workpiece, is characterized in that: comprise the following steps: (1) Mix the powder with an organic adhesive and a solvent to make a slurry; (2) Spread the above-mentioned slurry into a thin layer of slurry in a limited area, and make the thin layer harden due to the volatilization of the solvent; (3) Scanning the above-mentioned hardened thin layer with an energy beam according to a specific path, heating up the scanned area on the above-mentioned thin layer and sintering the thin layer of the workpiece, and the thin layer of the workpiece has the cross-sectional shape of the three-dimensional workpiece; (4) repeating steps (2), (3) to a predetermined number of times to produce a predetermined number of stacked layers, and these stacked layers are linked to each other when being scanned by the energy beam in step (3) to form the shape of a three-dimensional workpiece; and (5) removing the hardened block that has not been sintered by energy beam scanning from around the sintered three-dimensional workpiece to obtain a three-dimensional workpiece. 2, a kind of manufacturing method of three-dimensional workpiece, it is characterized in that: comprise the following steps: (1) Mix the powder with an organic adhesive and a solvent to make a slurry; (2) Spread the above-mentioned slurry into a thin layer of slurry in a limited area, and make the thin layer harden due to the volatilization of the solvent; (3) Scan the above-mentioned hardened thin layer with an energy beam according to a specific path, so that the scanned area on the above-mentioned thin layer is heated up and sintered into a metamorphic thin layer. This metamorphic thin layer includes the workpiece part and the supporting part, and the workpiece Sectional shapes of some three-dimensional workpieces; (4) Repeat steps (2), (3) to a predetermined number of times to produce a predetermined number of stacked layers, and these stacked layers are linked to each other when they are scanned by the energy beam in step (3) to form the shape and support of the three-dimensional workpiece shape; and (5) removing the hardened blocks and supporting structures that have not been sintered by energy beam scanning from around the sintered three-dimensional workpiece to obtain a three-dimensional workpiece. 3. The manufacturing method according to claim 1 or 2, characterized in that the powder is a single powder or a composite powder in which two or more powders are mixed. 4. The manufacturing method according to claim 3, characterized in that: the single powder is alumina, silicon oxide, zirconia, iron, stainless steel, copper, aluminum, nylon, acrylonitrile-butadiene-styrene copolymer polymer, polyethylene or polymethylmethacrylate. 5. The manufacturing method according to claim 3, characterized in that: the composite powder obtained by mixing two or more powders is plastic and ceramic composite powder, plastic and metal composite powder, high melting point plastic and low melting point plastic composite powder, high melting point plastic and low melting point plastic composite powder, Composite powder of melting point metal and low melting point metal, composite powder of high melting point ceramic and low melting point ceramic or metal and ceramic composite powder. 6. The manufacturing method according to claim 5, characterized in that: the plastic and ceramic composite powder is aluminum oxide powder coated with polymethyl methacrylate or aluminum oxide powder coated with modified polyvinyl alcohol. 7. The manufacturing method according to claim 1 or 2, characterized in that: the solvent is water or an organic solvent. 8. The manufacturing method according to claim 1 or 2, characterized in that: the organic adhesive includes a water-soluble organic adhesive and a water-insoluble organic adhesive. 9. The manufacturing method according to claim 8, characterized in that: the water-soluble organic adhesive is polyvinyl alcohol, starch, or cellulose. 10. The manufacturing method according to claim 8, characterized in that the water-insoluble organic adhesive is polyvinyl butyral. 11. The manufacturing method according to claim 1 or 2, characterized in that: the slurry further includes a dispersant, an antifoaming agent, and/or a light absorbing agent. 12. The manufacturing method according to claim 1 or 2, characterized in that the method of spreading the slurry into a thin layer in a limited area is rolling rolling method, sliding scraping method and scraper forming method. 13. The manufacturing method according to claim 1 or 2, characterized in that the slurry thin layer is heated in advance to dry and harden quickly before being scanned by an energy beam in a specific path. 14. The manufacturing method according to claim 13, characterized in that: the heating method is heating by radiation heat transfer from above the green body, convection heat transfer or conduction heat transfer from below the green body. 15. The manufacturing method according to claim 14, characterized in that: said radiant heat transfer heating is heating the slurry thin layer with visible light, infrared light or microwave energy. 16. The manufacturing method according to claim 14, characterized in that: said convective heat transfer heating uses hot air as a medium to heat the slurry thin layer. 17. The manufacturing method according to claim 14, characterized in that: said conduction heat transfer heating is a heater installed under the workpiece plate to heat the slurry thin layer. 18. The manufacturing method according to claim 1 or 2, characterized in that the energy beam is a CO ₂ laser beam or a Nd:YAG laser beam. 19. The manufacturing method according to claim 1 or 2, characterized in that: the method of removing the hardened blocks and supporting structures that have not been scanned and sintered by energy beams is soaking a disintegrating agent or destroying with force, or dipping and disintegrating Potion plus power to destroy. 20. The production method according to claim 19, characterized in that the disintegrant is water, organic solvent, strong acid or strong base. 21. The manufacturing method according to claim 19, characterized in that said force is ultrasonic vibration. 22. An equipment for manufacturing a green block containing a three-dimensional workpiece by using a slurry containing an organic binder, powder, and solvent, characterized in that it includes: A device for manufacturing green thin layers, including a thin layer laying device and a workbench; the thin layer laying device and the workbench make a relative movement at a certain distance, and spread the slurry on the workbench into a thin layer of slurry , and the thin layer can be hardened into a green thin layer due to the drying of the organic binder connecting the powder; the workbench supports the thin layer; An energy beam sintering equipment, including an energy beam generating device, and an energy beam scanning device; wherein the energy beam scanner guides the energy beam to move along a specific path on the aforementioned green body thin layer, so that the above green body thin layer is energy The area scanned by the beam heats up and sinters into a thin layer of the workpiece. 23. The device according to claim 22, characterized in that the device for manufacturing the thin layer of green body further comprises a heater for rapidly heating the thin layer of slurry to harden it. 24. The equipment according to claim 22, characterized in that the thin layer laying device includes a slurry pressurizing device, which is connected with a distributor with a rectangular outlet, and the long side of the outlet is approximately equal to the thickness of the slurry thin layer. On the wide side, the extruded slurry is moved in the direction of the long side by a scraper integrated in the thin layer laying device to form a thin layer of slurry. 25. The equipment according to claim 22, characterized in that: said thin layer laying device includes a slurry pressurizing device, which is connected with a circular pipe, and the extruded slurry is used to make the width of the slurry thin layer. The movement in the side direction forms the long strip shape of the wide side of the slurry thin layer, and then it is acted by a scraper integrated in the thin layer device to move in the long side direction to form the shape of the slurry thin layer. 26. The apparatus according to claim 22, wherein said thin layer laying device comprises: A feeding device, quantitatively conveying the slurry to the top surface of the green body, A film-making tool, which lays the slurry on the top surface of the green block with a certain pressure. 27. The equipment according to claim 26, characterized in that: the film-making tool is a roller, the height of which in space can be adjusted according to the working position of the energy beam, and can move in the vertical direction. The lower force applying device can adjust the force, so that when the slurry is expanded, the pressure can be changed. 28. The equipment according to claim 26, characterized in that: the film-making tool is a split-shaped plate, and the plate surface acting on the slurry is inclined at a small angle to the horizontal plane, and its height in the space can match the height of the energy beam. It can be adjusted according to the working position and can move in the vertical direction. A downward force applying device is attached to it, and the force applied can be adjusted so that the pressure can be changed when expanding the slurry. 29. The apparatus of claim 26, wherein the film forming tool is a scraper. 30. The equipment according to claim 22, wherein the workbench includes a workpiece seat and a lifting table, the workpiece seat carries the green body and the workpiece, and the lifting table carries the workpiece seat for vertical movement. 31. The equipment according to claim 22, characterized in that the heater is an infrared heater, which is placed above the thin layer of slurry to transfer heat by radiation heat. 32. The equipment according to claim 23, characterized in that: the heater is a microwave generating device placed above the slurry thin layer to conduct heat by radiation heat. 33. The equipment according to claim 23, characterized in that the heater is a hot fan placed above the thin slurry layer for convective heat transfer. 34. The apparatus according to claim 23, characterized in that the heater is an electric heating wire placed under the green body for heat conduction and heat transfer. 35. The apparatus according to claim 22, characterized in that the energy beam scanning device is a mask projection device. 36. The apparatus according to claim 22, wherein the energy beam scanning device comprises an energy beam moving device and an energy beam focusing device. 37. The device according to claim 36, characterized in that: the energy beam movement device is a vibrating mirror scanner, and the energy beam can be scanned in a two-dimensional plane by changing its direction through two rotating mirrors. 38. The equipment according to claim 36, characterized in that: the energy beam movement device is an X-Y table, and the energy beam can be scanned in a two-dimensional plane by changing its direction through two moving mirrors. 39. The apparatus of claim 36, wherein said energy beam focusing means is a lens. 40. The apparatus of claim 36, wherein said energy beam focusing means is a mirror.

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