Method for improving quality of laser sintering body

Abstract

The invention relates to a method for improving the quality of a laser sintered body, which comprises the following steps of: firstly coating a release agent on a borosilicate glass plate, then paving a metal powder layer or a resin particle layer on the release agent, arranging a laser below the borosilicate glass plate, enabling a light beam of a laser to penetrate through the borosilicate glass plate from bottom to top to partially or completely sinter the metal powder layer or the resin particle layer, then cleaning a sintered body, removing the release agent, cleaning the surface of the borosilicate glass plate, and repeating the operation to enable the final sintered body to meet the shape and size requirements; according to the method, the laser sintering technology and the stereolithography technology are combined, the advantages of the two technologies can be fully played, precise parts can be manufactured according to the precision of the stereolithography technology, and the method has the advantages of the selective laser sintering technology in the aspects of material selection range, firmness and quality; the method has certain application potential in the fields of aerospace, biomedicine and the like.

Description

Technical Field

[0001] The invention discloses a method for improving the quality of a laser sintered body, and belongs to the technical field of wax mold manufacturing in a casting process. Background Art

[0002] In recent years, low-cost powder metallurgy technology has been widely used, including the use of laser sintering technology to process metal and plastic powders to produce high-strength parts, but the surface finish of such parts is relatively poor and the porosity is high; the use of stereolithography technology to process resin materials can obtain a smooth and strong surface, but the strength of the parts is often insufficient and is easily limited by the range of printable materials. Although the multi-material 3D printers that have emerged in recent years have expanded the material range, the printable materials usually belong to the same system and cannot form additive manufacturing of multi-system materials. Summary of the invention

[0003] The present invention provides a method for improving the quality of laser sintered bodies in response to the above-mentioned prior art conditions. Its purpose is to use the laser sintering method to not only ensure the strength of the parts, but also improve the surface integrity, smoothness and firmness of the parts.

[0004] To achieve the above object, the present invention proposes the following technical solutions:

[0005] The present invention proposes a method for improving the quality of laser sintered bodies. The method comprises the following steps: firstly coating a release agent on a borosilicate glass plate, and then laying a metal powder layer or a resin particle layer on the release agent. A laser is arranged below the borosilicate glass plate, and the laser beam is made to pass through the borosilicate glass plate from bottom to top to sinter part or all of the metal powder layer or the resin particle layer. Then, the sintered body is cleaned and the release agent is removed. After cleaning the surface of the borosilicate glass plate, the above operation is repeated so that the final sintered body meets the shape and size requirements.

[0006] In one implementation, the metal powder layer material is 4340 steel.

[0007] In addition, the thickness of the borosilicate glass plate is 5-10 mm.

[0008] Furthermore, a support column is installed below the borosilicate glass plate to enable the borosilicate glass plate to perform multi-degree-of-freedom movements.

[0009] In one implementation, a metal part is laminated on top of a metal powder layer or a resin particle layer so that the final sintered body becomes an additively manufactured part of the metal part.

[0010] In one implementation, the final sintered body is deformed to densify it and improve its fusion properties.

[0011] 7. The method for improving the quality of laser sintered bodies according to claim 1, characterized in that the steps of processing a cylindrical shaft part with a center hole by using the method are as follows:

[0012] Step 1: Raw material preparation

[0013] A circular 4340 steel billet is prepared as a substrate. The 4340 steel billet has a thickness of 10-15 mm and an outer diameter of 100-140 mm. The surface finish is greater than 0.6 by mechanical processing, and the 4340 steel billet is cleaned with gasoline, acetone and alcohol in turn.

[0014] Prepare 4340 steel powder, powder size -300--350 mesh, powder purity 99.99%;

[0015] Prepare resin pellets with a purity of 99.99%

[0016] Step 2: Device preparation

[0017] Prepare a borosilicate glass plate with a diameter of 200-300 mm and a thickness of 5-10 mm. Install 6 pillars under the glass plate to enable the glass plate to perform multi-degree-of-freedom movements.

[0018] Setting a laser below a borosilicate glass plate;

[0019] Step 3: Material Laying

[0020] Determine the single sintering thickness and the number of sintering layers through the three-dimensional digital model of the cylindrical shaft part to be processed, and then evenly lay a release agent with a thickness of 0.5-1mm on the borosilicate glass plate. After the release agent solidifies, evenly lay a layer of 4340 steel powder with a thickness of 1-2mm on the release agent, and then place the 4340 steel billet on the 4340 steel powder layer to complete the laying of the first layer of sintering material;

[0021] Step 4: Metal Sintering

[0022] Start the laser, and the light beam irradiates the release agent and 4340 steel powder from bottom to top through the borosilicate glass plate. The irradiated 4340 steel powder is connected with the 4340 steel billet and solidified. The 4340 steel billet is lifted up, the release agent is removed, and the additive preparation of the first layer of sintered material is completed.

[0023] Step 5: Composite sintering

[0024] Repeat steps 3 and 4 ten times in a row to complete the additive preparation of the subsequent ten layers of sintered material layers, and then repeat steps 3 and 4 again, replace the 4340 steel powder with resin particles to form a composite sintering of metal and resin materials to obtain a nearly net cylindrical shaft part;

[0025] Step 6: Plastic deformation

[0026] After completing step five, insert a conforming mandrel into the center hole of the cylindrical shaft part and place it on a rolling machine for surface plastic deformation. Before deformation, preheat the cylindrical shaft part and the rolling wheel of the rolling machine at a temperature of 80-100°C. The rolling of the cylindrical shaft part softens the resin material on its surface and re-integrates it with the 4340 steel material underneath, finally obtaining a full-size cylindrical shaft part.

[0027] In the above technical solution, the laser sintering device is inverted so that the laser beam irradiates from bottom to top through the borosilicate glass plate and acts on the sintered material, which can reduce the process difficulty because the release agent and the metal powder layer or resin particle layer can be easily fixed on the silicate glass plate, and then the substrate is pressed on it. After the sintering and fusion are completed, the substrate can be lifted to quickly and conveniently lay the next layer of sintered material until the component is formed.

[0028] In the above technical solution, laser sintering and photolithography technology are integrated together, and the manufacturing of multi-system material components is realized. In the existing process, ordinary laser sintering can realize the sintering of multi-system materials, but the surface of the sintered body is rough, and cold processing is required to reach the final part size, and the sintered body quality is poor. Ordinary photolithography can realize the preparation of high-quality sintered bodies, but the material system is limited to silicon wafers. Therefore, the solution of the present invention combines laser sintering and photolithography together, which realizes the sintering of multi-system materials and ensures the quality of the sintered body. The shape of the sintered body has no margin with the part, and cold processing is not required.

[0029] The technical solution of the present invention is to realize the combination of laser sintering and photolithography technology, and uses borosilicate glass plates and release agents, which are essential elements in photolithography technology. The release agent can ensure the surface quality of the sintered body. The borosilicate glass plate serves as a carrier to carry the release agent and the sintered material. In one embodiment, the sintered material is 4340 steel metal powder and resin material, which reflects the diversity of the material system.

[0030] The beneficial effects of the technical solution of the present invention are:

[0031] 1. The invention scheme develops a new type of additive manufacturing technology for multi-process additive manufacturing, which combines the selective laser sintering technology with the stereolithography technology, and can give full play to the advantages of the two technologies. It can not only manufacture precise parts with the accuracy of stereolithography technology, but also has the advantages of selective laser sintering technology in terms of the range of material selection, firmness and quality. It has certain application potential in many fields such as aerospace, biomedicine, etc.

[0032] 2. Through the scheme of the present invention, the reverse printing system directs its laser vertically upward through the borosilicate glass plate. Specifically, a controlled amount of polymer or metal powder is first deposited on the glass, and then the substrate is pressed on top of the unmelted powder monolayer, and the particulate material is selectively fused to it using the laser. Once the process is completed and the substrate is lifted, the material can be replenished and the process is repeated until the desired part is formed;

[0033] 3. Through the scheme of the present invention, it is possible to print resin materials and metal powders in the same component, and use laser to irradiate the powder from one side of the glass to fuse the powder on the substrate. Then transfer the substrate to another glass sheet coated with a resin film, and irradiate it with laser again to solidify the resin on the substrate. Repeat the above process according to the actual parts requirements;

[0034] 4. In the solution of the present invention, the laser printing system is inverted mainly to reduce the difficulty of the process. If the borosilicate glass plate is located above the part, the release agent and powder are not easy to be fixed on the silicate glass plate. Moreover, the potential weight of the glass plate will also have an uncontrollable impact on the structure of the part that has just been sintered. DETAILED DESCRIPTION

[0035] The technical solution of the present invention will be further described in detail below in conjunction with embodiments:

[0036] In this embodiment, a cylindrical shaft part with a center hole is processed by the method of the present invention, and the steps are as follows:

[0037] Step 1: Raw material preparation

[0038] A circular 4340 steel billet is prepared as a substrate. The 4340 steel billet has a thickness of 10-15 mm and an outer diameter of 100-140 mm. The surface finish is greater than 0.6 by mechanical processing, and the 4340 steel billet is cleaned with gasoline, acetone and alcohol in turn.

[0039] Prepare 4340 steel powder, powder size -300--350 mesh, powder purity 99.99%;

[0040] Prepare resin pellets with a purity of 99.99%

[0041] Step 2: Device preparation

[0042] Prepare a borosilicate glass plate with a diameter of 200-300 mm and a thickness of 5-10 mm. Install 6 pillars under the glass plate to enable the glass plate to perform multi-degree-of-freedom movements.

[0043] Setting a laser below a borosilicate glass plate;

[0044] Step 3: Material Laying

[0045] Determine the single sintering thickness and the number of sintering layers through the three-dimensional digital model of the cylindrical shaft part to be processed, and then evenly lay a release agent with a thickness of 0.5-1mm on the borosilicate glass plate. After the release agent solidifies, evenly lay a layer of 4340 steel powder with a thickness of 1-2mm on the release agent, and then place the 4340 steel billet on the 4340 steel powder layer to complete the laying of the first layer of sintering material;

[0046] Step 4: Metal Sintering

[0047] Start the laser, and the light beam irradiates the release agent and 4340 steel powder from bottom to top through the borosilicate glass plate. The irradiated 4340 steel powder is connected with the 4340 steel billet and solidified. The 4340 steel billet is lifted up, the release agent is removed, and the additive preparation of the first layer of sintered material is completed.

[0048] Step 5: Composite sintering

[0049] Repeat steps 3 and 4 ten times in a row to complete the additive preparation of the subsequent ten layers of sintered material layers, and then repeat steps 3 and 4 again, replace the 4340 steel powder with resin particles to form a composite sintering of metal and resin materials to obtain a nearly net cylindrical shaft part;

[0050] Step 6: Plastic deformation

[0051] After completing step five, insert a conforming mandrel into the center hole of the cylindrical shaft part and place it on a rolling machine for surface plastic deformation. Before deformation, preheat the cylindrical shaft part and the rolling wheel of the rolling machine at a temperature of 80-100°C. The rolling of the cylindrical shaft part softens the resin material on its surface and re-integrates it with the 4340 steel material underneath, finally obtaining a full-size cylindrical shaft part.

Claims

1. A method for improving the quality of a laser sintered body, characterized in that: The method is to first apply a release agent on a borosilicate glass plate, then lay a metal powder layer or a resin particle layer on the release agent, set a laser under the borosilicate glass plate, and make the laser beam pass through the borosilicate glass plate from bottom to top to sinter part or all of the metal powder layer or the resin particle layer, then clean the sintered body and remove the release agent, after cleaning the surface of the borosilicate glass plate, repeat the above operation, so that the final sintered body meets the shape and size requirements.

2. The method for improving the quality of laser sintered bodies according to claim 1, characterized in that: The metal powder layer material is 4340 steel.

3. The method for improving the quality of laser sintered bodies according to claim 1, characterized in that: The thickness of the borosilicate glass plate is 5-10 mm.

4. The method for improving the quality of laser sintered bodies according to claim 1 or 3, characterized in that: Support pillars are installed under the borosilicate glass plate to enable the borosilicate glass plate to perform multi-degree-of-freedom movements.

5. The method for improving the quality of laser sintered bodies according to claim 1, characterized in that: The metal part is laminated on top of the metal powder layer or resin particle layer so that the final sintered body becomes an additively manufactured part of the metal part.

6. The method for improving the quality of laser sintered bodies according to claim 1 or 5, characterized in that: The final sintered body is deformed to densify it and improve its fusion.

7. The method for improving the quality of laser sintered bodies according to claim 1, characterized in that: The steps for machining a cylindrical shaft part with a center hole using this method are as follows: Step 1: Raw material preparation A circular 4340 steel billet is prepared as a substrate. The 4340 steel billet has a thickness of 10-15 mm and an outer diameter of 100-140 mm. The surface finish is greater than 0.6 by mechanical processing, and the 4340 steel billet is cleaned with gasoline, acetone and alcohol in turn. Prepare 4340 steel powder, powder size -300--350 mesh, powder purity 99.99%; Prepare resin pellets with a purity of 99.99% Step 2: Device preparation Prepare a borosilicate glass plate with a diameter of 200-300 mm and a thickness of 5-10 mm. Install 6 pillars under the glass plate to enable the glass plate to perform multi-degree-of-freedom movements. Setting a laser below a borosilicate glass plate; Step 3: Material Laying Determine the single sintering thickness and the number of sintering layers through the three-dimensional digital model of the cylindrical shaft part to be processed, and then evenly lay a release agent with a thickness of 0.5-1mm on the borosilicate glass plate. After the release agent solidifies, evenly lay a layer of 4340 steel powder with a thickness of 1-2mm on the release agent, and then place the 4340 steel billet on the 4340 steel powder layer to complete the laying of the first layer of sintering material; Step 4: Metal Sintering Start the laser, and the light beam irradiates the release agent and 4340 steel powder from bottom to top through the borosilicate glass plate. The irradiated 4340 steel powder is connected with the 4340 steel billet and solidified. The 4340 steel billet is lifted up, the release agent is removed, and the additive preparation of the first layer of sintered material is completed. Step 5: Composite sintering Repeat steps 3 and 4 ten times in a row to complete the additive preparation of the subsequent ten layers of sintered material layers, and then repeat steps 3 and 4 again, replace the 4340 steel powder with resin particles to form a composite sintering of metal and resin materials to obtain a nearly net cylindrical shaft part; Step 6: Plastic deformation After completing step five, insert a conforming mandrel into the center hole of the cylindrical shaft part and place it on a rolling machine for surface plastic deformation. Before deformation, preheat the cylindrical shaft part and the rolling wheel of the rolling machine at a temperature of 80-100°C. The rolling of the cylindrical shaft part softens the resin material on its surface and re-integrates it with the 4340 steel material underneath, finally obtaining a full-size cylindrical shaft part.