Pull-up type light-cured 3D printer printing platform and 3D printing method

Abstract

This application discloses a printing platform for an up-pull photopolymerization 3D printer. The printing platform includes a main body and a model plate. A hanging screw screwed onto the main body passes downwards through the model plate. The model has structural columns bonded to the working surface. The hanging screw can move downwards and be screwed into an internal hole in the structural column, and can also move upwards and exit the internal hole. A central gear is arranged within a gear cavity of the main body. The hanging screw is evenly distributed around the central gear, and a screw gear meshing with the central gear is fixed at its top. A central rod extends into the gear cavity and connects to the central gear. A drive device is fixed to the printing platform and connected to the central rod. This application also discloses a 3D printing method. This application utilizes the hanging screw to increase the strength of the structural column, allowing the model to be stably held on the printing platform. After printing the model, the hanging screw exits the structural column, cutting it off, thus allowing the model to be removed from the model plate, achieving efficient model removal and ensuring model integrity.

Description

[0001] This application is a divisional application. The original application was filed on October 27, 2025, with application number 2025115347855, and the invention title was: Pull-up photopolymerization 3D printer and 3D printing method with quick-release model printing platform. Technical Field

[0002] This invention relates to a printing platform for an uplift photopolymerization 3D printer and a 3D printing method using the uplift photopolymerization 3D printer having the printing platform. Background Technology

[0003] In the process of up-curing photopolymer 3D printing, a light source is used to irradiate liquid photosensitive resin, which is then cured and bonded to the printing platform. Each photopolymerization typically forms a cured layer with a thickness of only 0.05-0.2mm. Each product model requires at least hundreds of up-and-down movements of the printing platform to allow the newly formed cured layer to peel off from the release film.

[0004] Because frequent peeling of the cured layer and release film is required, a base layer is first formed on the printing platform at the beginning of the printing process to prevent the model from detaching. This base layer has a longer exposure time during its formation to improve its own strength and adhesion to the printing platform. However, this strong adhesion between the base layer and the printing platform becomes a challenge when removing the model from the platform. Currently, model removal from the printing platform mainly uses tools such as scrapers. This process easily damages or scratches the model and requires careful handling, resulting in low removal efficiency.

[0005] Therefore, how to efficiently remove the model from the printing platform while maintaining its integrity is also a problem that needs to be solved to improve the level of pull-up photopolymerization 3D printing technology. Summary of the Invention

[0006] To address the problem in existing technologies where models are difficult to detach from the printing platform, this application first proposes a printing platform for an up-pull photopolymerization 3D printer, which includes a main body and a model plate detachably mounted on the lower side of the main body. The lower surface of the model plate forms a working surface. Several hanging screws are screwed onto the main body. Corresponding to each hanging screw, the model plate has a through-hole-shaped template hole, allowing the hanging screws to freely pass downward through the corresponding template hole. A drive device for driving the hanging screws to rotate is also installed on the printing platform.

[0007] The model is bonded to the printing platform. The model includes several structural columns bonded to the working surface, a bottom layer connected to the lower end of the structural columns, and a model body connected to the lower side of the bottom layer. A structural column is provided for each hanging screw, and the structural column is located directly below the corresponding hanging screw. An internal hole is provided in the structural column, and the internal hole is connected upward to the template hole corresponding to the structural column.

[0008] The main body includes a connecting part and an end plate detachably mounted on the lower end of the connecting part. The model plate is detachably connected to the lower side of the end plate. A gear cavity is formed between the end plate and the connecting part. A central gear is arranged in the gear cavity. Each hanging screw is evenly arranged around the central gear. A screw gear is fixedly installed on the top of each hanging screw. Each screw gear meshes with the central gear. A central rod passes freely through the main body in the vertical direction and extends into the gear cavity, and is fixedly connected to the central gear. A drive device is fixedly mounted on the top of the printing platform and connected to the central rod. Both the central gear and the screw gear are spur gears.

[0009] Driven by the drive device, the hanging screw can reciprocate vertically. When the hanging screw moves downward, it extends downward into the corresponding template hole and is screwed into the internal hole of the corresponding structural column. When the hanging screw moves upward, it can exit from the internal hole and the lower end of the hanging screw detaches from the structural column. The hanging screw is specifically made of metal material, preferably a material with strong durability.

[0010] In this application, during the model printing process, hanging screws are used to increase the strength of the structural columns, allowing the model to be stably held on the printing platform. After printing is complete, the hanging screws are removed from the structural columns, and the model plate is then disassembled. The model is positioned on top of the model plate, and the structural columns are cut using tools such as scissors or a hacksaw to remove the model from the model plate. The remaining portion of the structural columns on the model is then completely removed. Because the area around the structural columns is open, cutting the columns does not damage the model itself, and the cutting speed is relatively fast, effectively increasing the disassembly speed. After cleaning away any remaining structural columns from the model plate, the model plate can be reused.

[0011] When assembling the printing platform, first install the central gear at the lower end of the central rod, then screw the hanging screw carrying the screw gear into the corresponding threaded hole on the end plate, and make the lower ends of each hanging screw on the same horizontal plane. Then install the end plate on the lower surface of the connecting part, so that the central gear and the screw gear mesh together. Finally, install the model plate on the end plate.

[0012] When the drive device drives the center rod to rotate, it can drive the hanging screw to rotate via the center gear and the screw gear. Since the hanging screw is screwed onto the end plate, it will move up and down synchronously when the hanging screw rotates. Since both the center gear and the screw gear are spur gears, the teeth of the center gear and the screw gear extend in the vertical direction. Therefore, when the hanging screw rotates, it can drive the screw gear to reciprocate in the vertical direction relative to the center gear.

[0013] During the process of screwing the hanging screw into the built-in hole, some resin debris will inevitably be produced. This resin debris will fall into the photosensitive resin in the material tank. In order to avoid damage to the release film, the inner cavity of the material tank is divided into a working area and a non-working area surrounding the working area. A scraper is installed in the material tank. The scraper can move from one side of the material tank to the opposite side to push the solid particles deposited at the bottom of the material tank from the working area to the non-working area. In the vertical direction, the projection of the printing platform is located in the working area.

[0014] A scraper is used to push resin debris and other solid particles that have fallen and settled at the bottom of the trough from the working area to the non-working area. This prevents the model from pressing against larger solid particles during its descent, which could damage the release film. To avoid resin debris remaining in the working area during scraper operation, the hanging screw stops rotating and remains stationary after each cured layer is printed and before the next cured layer is printed. The hanging screw only rotates during each cured layer printing process, allowing it to be gradually screwed into the internal hole. When screwing the hanging screw, its lower end must always remain within the internal hole and must not extend downwards to avoid the hanging screw touching the release film and causing damage.

[0015] Specifically, the built-in hole extends downwards into the bottom layer, but does not penetrate the bottom layer; when the hanging screw moves downwards, the lower end of the hanging screw can be screwed into the area where the built-in hole is located on the bottom layer. This design improves the connection strength between the model and the printing platform, preventing breakage from the connection between the structural column and the bottom layer.

[0016] Furthermore, the hanging screw is a hollow screw with a downward opening. The inner cavity of the hanging screw can contain some of the resin powder generated during the screw's twisting process, reducing the amount of resin powder falling into the material trough.

[0017] Specifically, the drive device is a hollow shaft torque motor, which includes a stator and a mover rotatably disposed within the stator. The hollow shaft torque motor is mounted on the top of the printing platform via the stator, the hollow shaft is fixed on the mover, and the center rod is fixedly installed in the center hole of the hollow shaft. The hollow shaft and the center rod are coaxially arranged. The hollow shaft torque motor is a servo motor.

[0018] Alternatively, the drive unit may be a solid shaft servo motor, which is fixedly mounted on the top of the printing platform, and the output shaft of the drive unit is connected to the central rod.

[0019] Both of the above-mentioned structural forms of the drive device can meet the driving needs of the hanging screw, and the choice can be made according to the specific structure of the equipment and usage habits.

[0020] Secondly, this application also discloses a 3D printing method, which uses an up-type photopolymerization 3D printer having the printing platform described in any of the above claims. The 3D printing method includes the following steps:

[0021] (1) After the 3D modeling of the main body of the model to be printed is completed, the starting surface of the main body of the model is determined, and the thickness of the bottom layer is determined on the starting surface. Then, the position of the structural column is determined on the side of the bottom layer away from the main body of the model, and each hanging screw corresponds to a structural column.

[0022] (2) Print the structural columns and the bottom layer in sequence, and form an internal hole in the structural columns and the bottom layer. The internal hole is coaxially set with the corresponding hanging screw. The inner diameter of the internal hole is less than the outer diameter of the thread of the hanging screw. Rotate the hanging screw to screw it into the internal hole. During the printing interval of the two adjacent curing layers, the hanging screw remains stationary.

[0023] The material trough is fixedly installed on the worktable. The material trough is rectangular and its inner cavity is divided into a working area and a non-working area surrounding the working area. A scraper is installed in the material trough. The scraper can move from one side of the material trough to the opposite side to push the solid particles deposited at the bottom of the material trough from the working area to the non-working area. In the vertical direction, the projection of the printing platform is located in the working area.

[0024] When printing structural columns and the bottom layer, after each cured layer is printed, the printing platform is lifted upwards, and after the cured layer separates from the release film of the material tank, the scraper is activated, moving from one side of the material tank to the opposite side, pushing the solid particles deposited at the bottom of the material tank from the working area to the non-working area.

[0025] (3) Print the main body of the model. After printing the main body of the model, remove the hanging screw from the structural column and remove the model from the printing platform.

[0026] In the 3D printing method of this application, during the printing process, the structural columns and the bottom layer are printed first, and internal holes are formed within the structural columns and the bottom layer. Simultaneously, a hanging screw is screwed into the internal hole. The hanging screw is used to improve the connection strength between the structural columns and the bottom layer and the main body of the model, preventing the structural columns from breaking during printing. After the main body of the model is printed, the hanging screw is withdrawn from the internal hole and retracted into the printing platform. This application utilizes the good toughness of resin so that when the hanging screw is screwed into the internal hole, the cutting action of the hanging screw's thread forms an internal thread that meshes with the thread of the hanging screw.

[0027] During the process of screwing the hanger screw into the internal hole, a scraper pushes resin debris and other solid particles that fall into the material trough from the working area to the non-working area. This prevents the mold from pressing against larger solid particles during descent, which could damage the release film. To avoid resin debris generated during scraper operation remaining in the working area, the hanger screw stops rotating and remains stationary after each cured layer is printed and before the next cured layer is printed. The hanger screw only rotates during each cured layer printing process and gradually screws downward as the internal hole extends. When screwing the hanger screw, the lower end of the hanger screw must always remain inside the internal hole and must not extend downward to avoid the hanger screw touching the release film and causing damage.

[0028] After printing the model, remove the hanging screws from the structural columns, then disassemble the model plate and position the model on top of it. Use scissors or a hacksaw to cut the structural columns, thus removing the model from the model plate. Then, completely remove the remaining structural columns from the model. Because the area around the structural columns is open, cutting them will not damage the model itself, and the cutting speed is relatively fast, effectively increasing the disassembly speed. After cleaning away any remaining structural columns from the model plate, the model plate can be reused.

[0029] Specifically, to ensure that the structural column can still bear the weight of the model when the suspension bolt is withdrawn from the internal hole, the diameter of the structural column is ≥10mm larger than the outer diameter of the suspension bolt. This design ensures that the wall thickness of the structural column is at least 5mm, so that the structural column still has high strength after the suspension bolt is removed. However, the above limitation only sets a lower limit for the wall thickness of the structural column, and there is no definite upper limit. In specific embodiments, the wall thickness of the structural column needs to be determined according to the specific weight of the model to ensure that the structural column can independently bear the weight of the model.

[0030] Furthermore, in order to ensure that the hanging screw is smoothly screwed into the internal hole, D1-D2=(0.5-1)W, where D1 is the outer diameter of the thread of the hanging screw, D2 is the inner diameter of the internal hole, and W is the height of the thread of the hanging screw.

[0031] Since the model is a resin product, it has a certain degree of deformability. Even if the difference between D1 and D2 is less than W, a complete thread can still be formed by utilizing the deformability of the resin. The difference between D1 and D2 is determined based on the deformability of the resin. In specific embodiments, corresponding experiments are required to determine the difference between D1 and D2.

[0032] Specifically, the height of the structural column is 2-5mm, and the thickness of the bottom layer is 2-5mm. The height of the structural column and the thickness of the bottom layer need to be determined based on the size of the model's cross-section. When the model's cross-section is large, the upper limit is used for both the height of the structural column and the thickness of the bottom layer to facilitate cutting the structural column and to ensure sufficient strength of the bottom layer. When the model's cross-section is small, the lower limit can be used for both the height of the structural column and the thickness of the bottom layer. In specific embodiments, the specific height of the structural column and the specific thickness of the bottom layer need to be determined experimentally.

[0033] This application is not applicable to all pull-out photopolymer 3D printers. For some smaller models, where disassembling the model with a spatula will not damage the model, existing technology can still be used for printing. Furthermore, smaller models have a lower cost-effectiveness when setting up structural columns. Therefore, the use of this application needs to be determined based on the specific circumstances. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of an embodiment of the pull-up photopolymerization 3D printer of the present invention.

[0035] Figure 2 yes Figure 1 A view from the center AA direction.

[0036] Figure 3 yes Figure 2 Enlarged view of section B.

[0037] Figure 4 This is a diagram showing the dimensional relationship between the built-in hole and the hanging screw.

[0038] Figure 5 This is a schematic diagram of the connecting arm.

[0039] Figure 6 This is a top view of the trough.

[0040] Figure 7 yes Figure 6 A view directed towards the center (CC).

[0041] Figure 8 This is a schematic diagram of another embodiment of the pull-up photopolymerization 3D printer of the present invention. Detailed Implementation

[0042] Example 1

[0043] See Figures 1-7 A pull-up photopolymer 3D printer with a quick-release printing platform includes a worktable 11. A transmission mechanism is mounted on the worktable 11, employing existing mature technology. The transmission mechanism includes a vertical rod 12 fixed to the worktable 11 and a ball screw 13 rotatably mounted on one side of the vertical rod. The ball screw 13 extends vertically, and one end of a connecting arm 14 is engaged with the ball screw via a screw hole. The connecting arm 14 extends horizontally, and a printing platform 20 is detachably mounted on the end of the connecting arm 14 away from the ball screw. A servo motor 15 is mounted at the lower end of the ball screw and is fixedly mounted on the vertical rod. The servo motor can drive the ball screw to rotate, enabling the connecting arm to drive the printing platform to reciprocate vertically.

[0044] The material trough 17 is fixedly installed on the worktable. The material trough 17 is rectangular and specifically includes a vertically extending trough wall 171. A release film 174 is provided at the bottom of the trough wall, and a trough flange 175 is provided on the outer side of the bottom of the trough wall. Bolts pass through the trough flange 175 and are screwed onto the worktable, detachably fixing the material trough to the worktable. The inner cavity of the material trough is divided into a working area 173 and a non-working area 172, with the non-working area surrounding the working area. Figure 6 In the diagram, a double-dotted line 176 is used as the boundary between the working area 173 and the non-working area 172. Vertically, the projection of the printing platform lies within the working area.

[0045] A scraper system 18 is also installed on the worktable. This scraper system 18 includes a scraper 181 arranged within a material trough, parallel to one side wall of the trough wall 171. A lead screw 183 and a slide rail 185 are respectively provided at both ends along the length of the scraper. Both the lead screw and the slide rail are located outside the material trough. The lead screw is rotatably mounted on the worktable via a bearing seat, and the slide rail is fixedly mounted on the worktable. Both the lead screw and the slide rail are perpendicular to the length of the scraper. A first U-shaped arm 182 is connected to one end of the scraper along its length, and the first U-shaped arm 182 is engaged with the lead screw via a lead screw nut. A second U-shaped arm 186 is connected to the other end of the scraper along its length, and the second U-shaped arm 186 is slidably supported on the slide rail via a sliding groove. One end of the lead screw is fixedly connected to the output shaft of a drive motor 184, which is mounted on the worktable. The blade of the scraper abuts against the release film. Driven by the drive motor, the lead screw can move the scraper from one side of the material trough to the opposite side, pushing the solid particles deposited at the bottom of the material trough from the working area to the non-working area.

[0046] A liquid crystal display screen 191 is fixedly mounted on the top plate 111 of the workbench 11, and an irradiation unit 19 is fixedly mounted in the inner cavity 112 of the workbench 11. The irradiation unit 19 is fixed on the bottom plate 113 of the workbench and is located below the liquid crystal display screen 191. The irradiation unit provides a shaping beam for curing the photosensitive resin in the material tank 17. The irradiation unit 19 can be a digital light source processing (DLP) projection device or other types of projection devices (such as LCOS, LCD), but is not limited thereto.

[0047] The printing platform 20 includes a main body and a model plate 23 detachably mounted on the lower side of the main body, with the lower surface of the model plate 23 forming a working surface 231. The main body includes a connecting part 21 and an end plate 22 detachably mounted on the lower end of the connecting part by bolts. The model plate 23 is detachably connected to the lower side of the end plate 22 by bolts. A gear cavity 26 is formed between the end plate and the connecting part, specifically formed by an upward indentation of the lower surface of the connecting part 21.

[0048] In this embodiment, the connecting arm 14 has two horizontally spaced retaining arms 141 at the end away from the ball screw. The two retaining arms 141 extend away from the ball screw and are parallel to each other, forming a platform receiving cavity 142 between the two retaining arms. The platform receiving cavity has an opening away from the ball screw. Corresponding to each retaining arm 141, a slot 25 is provided on opposite sides of the connecting part. The printing platform 20 is inserted into the platform receiving cavity 142, and each retaining arm 141 is inserted into the corresponding slot 25. The first bolt 16 passes through the retaining arm and is screwed into the first screw hole 251 located in the slot, so that the retaining arm is detachably fixed to the printing platform. To avoid shaking, each retaining arm is fixed to the printing platform by two first bolts.

[0049] A central gear 43 is arranged within the gear cavity 26. Suspension screws 45 are evenly arranged around this central gear. A screw gear 44 is fixedly installed on the top of each suspension screw 45, and all screw gears mesh with the central gear. The number of suspension screws 45 can be determined based on the size of the printing platform and the weight of the printed model; there are no specific requirements, but generally 3-10 screws are sufficient. In this embodiment, four suspension screws are provided. Both the central gear and the screw gears are spur gears. The suspension screws are made of stainless steel.

[0050] For each hanging screw 45, a screw hole 221 is provided on the end plate 22. The screw hole is an internally threaded hole. For each hanging screw 45, a through-hole template hole 232 is provided on the model plate 23. The template hole 232 extends vertically through the upper and lower sides of the model plate. The screw hole and template hole corresponding to the same hanging screw are coaxially arranged. The hanging screw 45 is screwed into the corresponding screw hole 221 and can freely pass downward through the corresponding template hole. Specifically, in this embodiment, the hanging screw is a hollow screw with a downward opening.

[0051] A through hole 24 is provided vertically on the connecting part 21. The first central rod 41 passes freely through the through hole 24 from top to bottom and extends into the gear cavity 26. One end of the first central rod 41 extending into the gear cavity 26 is fixed to the central shaft hole of the central gear 43.

[0052] A drive device for rotating the first central rod is installed on the top of the printing platform. In this embodiment, the drive device is a hollow shaft torque motor 70, which includes a stator 71 and a mover 75 rotatably disposed within the stator 71. A hollow shaft 81 is fixed to the mover 75. An upper end cover 72 and a lower end cover 73 are respectively installed at the upper and lower ends of the stator 71. The upper end cover 72 is bolted to the upper flange 711 at the upper end of the stator 71, and the lower end cover 73 is bolted to the lower flange 712 at the lower end of the stator 71. Both the upper flange 711 and the lower flange 712 are integrally formed on the stator 71. A winding 74 is provided on the inner side of the stator.

[0053] In this embodiment, an upper connecting flange 76 is provided on the outer peripheral surface of the hollow shaft 81, and the upper end cover has an inwardly protruding upper abutting flange 721. The lower surface of the upper abutting flange 721 is a downward-facing stepped surface. The upper abutting flange 721 presses against the upper side of the outer ring of the upper angular contact bearing 78 through its lower surface, and the upper connecting flange 76 presses against the lower side of the inner ring of the upper angular contact bearing, so that the upper end cover is rotatably connected to the hollow shaft 81 through the upper angular contact bearing.

[0054] A lower step portion 77 is provided at the lower end of the hollow shaft 81. This lower step portion has a downward-facing stepped surface and is formed by a radial inward recess from the outer circumferential surface of the hollow shaft 81. The lower end cover abuts against the lower side of the outer ring of the lower angular contact bearing 79 via its upper surface, and the lower step portion 77 presses against the lower side of the inner ring of the lower angular contact bearing, so that the lower end cover is rotatably connected to the hollow shaft 81 via the lower angular contact bearing. The structure of the hollow shaft torque motor can be completed using existing mature technology and will not be described in detail here.

[0055] The lower end cover 73 is detachably mounted on the upper surface of the connecting part by bolts, thereby mounting the hollow shaft torque motor 70 on the upper surface of the connecting part.

[0056] In this embodiment, the central hole 82 of the hollow shaft 81 is a threaded hole, and the first central rod 41 is an externally threaded rod. The first central rod 41 is screwed into the central hole 82 of the hollow shaft 81 and extends upward from the central hole. The locking nut 42 is screwed onto the first central rod and presses against the upper end face of the hollow shaft 81. A flat key 83 is installed between the hollow shaft 81 and the first central rod, thereby fixing the first central rod in the central hole of the hollow shaft 81, so that the hollow shaft can drive the first central rod to rotate. The hollow shaft and the first central rod are coaxially arranged.

[0057] Model 30 is bonded to the working surface of the printing platform. Figure 2 In this embodiment, the model is represented by dashed lines and no cross-sectional lines are provided. Specifically, the model 30 includes four structural columns 33 bonded to the working surface, a bottom layer 32 connected to the lower ends of the four structural columns, and a model body 31 connected to the lower side of the bottom layer. A structural column is provided corresponding to each hanging screw 45, and the structural column is located directly below the corresponding hanging screw. An internal hole 34 is provided within the structural column, which connects upwards to the template hole corresponding to the structural column. The internal hole extends downwards into the bottom layer, but does not penetrate the bottom layer.

[0058] When the hollow shaft torque motor drives the first central rod to rotate, it can drive the hanging screw to rotate via the central gear and the screw gear. Since the hanging screw is screwed onto the end plate, it will move up and down synchronously when it is screwed. Since both the central gear and the screw gear are spur gears, the teeth of the central gear and the screw gear extend in the vertical direction. Therefore, when the hanging screw rotates, it can drive the screw gear to move in the vertical direction relative to the central gear.

[0059] Driven by the drive device, the hanging screw can reciprocate in the vertical direction. When the hanging screw moves downward, it can extend downward into the corresponding template hole and be screwed into the built-in hole of the corresponding structural column. The lower end of the hanging screw can be screwed into the area where the built-in hole is located at the bottom layer. When the hanging screw moves upward, it can exit from the built-in hole and the lower end of the hanging screw can be detached from the structural column.

[0060] For details regarding the structural columns, the bottom layer, and the internal holes, please refer to Example 3.

[0061] Example 2

[0062] Please see Figure 8 This embodiment is basically the same as Embodiment 1, except that the driving device is different. Figure 8 and Figures 1-7 The same reference numerals in the figures represent the same technical features.

[0063] In this embodiment, the driving device is a solid shaft servo motor 60. A motor base 61 is fixedly installed on the top of the connecting part 21. The solid shaft servo motor 60 is fixedly installed on the motor base. The output shaft of the solid shaft servo motor 60 extends downward in the vertical direction and is connected to the second center rod 47 via a coupling 62. In this embodiment, the second center rod 47 is cylindrical.

[0064] It is understood that in other embodiments, the solid shaft servo motor 60 may also be mounted on one side of the second center rod and then connected to the second center rod by a belt or gear.

[0065] Example 3

[0066] The 3D printing method in this application is described below. This 3D printing method uses the pull-out photopolymerization 3D printer described in Embodiment 1 or Embodiment 2 above. The 3D printing method includes the following steps:

[0067] (1) After the 3D modeling of the main body 31 of the model to be printed is completed, the starting surface 311 for printing the main body of the model is determined, and the thickness of the bottom layer 32 is determined on the starting surface. Then, the position of the structural column 33 is determined on the side of the bottom layer 32 away from the main body 31 of the model, and each hanging screw 45 corresponds to a structural column 33. The height of the structural column is set to 3mm, and the thickness of the bottom layer is also set to 3mm. In this embodiment, the height of the structural column and the thickness of the bottom layer are the same. It can be understood that in other embodiments, the height of the structural column and the thickness of the bottom layer can be different, for example, the height of the structural column is 2mm and the thickness of the bottom layer is 4mm.

[0068] (2) Print structural columns 33 and bottom layer 32 in sequence, and form built-in holes in structural columns and bottom layers. The built-in holes are coaxially set with the corresponding hanging screws. The inner diameter of the built-in holes is less than the outer diameter of the screw thread of the hanging screw. Rotate the hanging screws to screw them into the built-in holes. During the printing interval of two adjacent curing layers, the hanging screws remain stationary while printing structural columns and bottom layers.

[0069] Specifically, in this embodiment, the outer diameter D1 of the threaded rod of the hanging screw is 5mm, the height W of the threaded rod of the hanging screw is approximately 0.49mm, and the inner diameter D2 of the internal hole is 4.6mm. That is, the inner diameter of the internal hole is approximately 0.82 times the height of the threaded rod of the hanging screw compared to the outer diameter of the hanging screw. The diameter of the structural column is 20mm, which is 10mm larger than the outer diameter of the hanging screw, resulting in a wall thickness of 5mm for the structural column.

[0070] When printing structural columns and the bottom layer, after each cured layer is printed, the printing platform is lifted upwards, and after the cured layer separates from the release film of the material tank, the scraper is activated, moving from one side of the material tank to the opposite side, pushing the solid particles deposited at the bottom of the material tank from the working area to the non-working area.

[0071] (3) Print the main body of the model. After printing the main body of the model, remove the hanging screws from the structural columns and remove the model from the printing platform. When removing the model from the printing platform, the hanging screws have completely exited the structural columns. Simply remove the model plate 23, place the model on top of the model plate, and use tools such as scissors or a hacksaw to cut the structural columns. Then, completely remove the remaining structural columns from the model. Since the area around the structural columns is open, cutting the structural columns will not damage the model itself, and the cutting speed of the structural columns is relatively fast, which can effectively improve the disassembly speed of the model. After cleaning up the structural columns remaining on the model plate, the model plate can be reused.

Claims

1. A printing platform for an up-pull photopolymerization 3D printer, characterized in that, The device includes a main body and a model plate detachably mounted on the lower side of the main body. The lower surface of the model plate forms a working surface. Several hanging screws are screwed onto the main body. Corresponding to each hanging screw, the model plate has a through-hole-shaped template hole, through which the hanging screw can freely pass downward. A drive device for driving the hanging screw to rotate is also installed on the printing platform. The model is bonded to the printing platform. The model includes several structural columns bonded to the working surface, a bottom layer connected to the lower end of the structural columns, and a model body connected to the lower side of the bottom layer. A structural column is provided for each hanging screw, and the structural column is located directly below the corresponding hanging screw. An internal hole is provided in the structural column, and the internal hole is connected upward to the template hole corresponding to the structural column. The main body includes a connecting part and an end plate detachably mounted on the lower end of the connecting part. The model plate is detachably connected to the lower side of the end plate. A gear cavity is formed between the end plate and the connecting part. A central gear is arranged in the gear cavity. Each hanging screw is evenly arranged around the central gear. A screw gear is fixedly installed on the top of each hanging screw. Each screw gear meshes with the central gear. A central rod passes freely through the main body in the vertical direction and extends into the gear cavity, and is fixedly connected to the central gear. A drive device is fixedly mounted on the top of the printing platform and connected to the central rod. Both the central gear and the screw gear are spur gears. Driven by the drive device, the hanging screw can reciprocate in the vertical direction. When the hanging screw moves downward, it can extend downward into the corresponding template hole and be screwed into the built-in hole of the corresponding structural column. When the hanging screw moves upward, it can exit from the built-in hole and the lower end of the hanging screw can be disengaged from the structural column.

2. The printing platform according to claim 1, characterized in that, The built-in hole extends downward into the bottom layer, but does not penetrate the bottom layer; when the hanging screw moves downward, the lower end of the hanging screw can be screwed into the area where the built-in hole is located in the bottom layer.

3. The printing platform according to claim 1, characterized in that, The hanging screw is a hollow screw with an opening at the bottom.

4. The printing platform according to claim 1, characterized in that, The drive device is a hollow shaft torque motor, which includes a stator and a mover rotatably disposed within the stator. The hollow shaft torque motor is mounted on the top of the printing platform via the stator, the hollow shaft is fixed on the mover, and the center rod is fixedly installed in the center hole of the hollow shaft. The hollow shaft and the center rod are coaxially arranged. The hollow shaft torque motor is a servo motor.

5. The printing platform according to claim 1, characterized in that, The drive unit is a solid shaft servo motor, which is fixedly mounted on the top of the printing platform, and the output shaft of the drive unit is connected to the central rod.

6. A 3D printing method, characterized in that, The 3D printing method, performed using a pull-up photopolymerization 3D printer having the printing platform described in any one of claims 1-5, comprises the following steps: (1) After the 3D modeling of the main body of the model to be printed is completed, the starting surface of the main body of the model is determined, and the thickness of the bottom layer is determined on the starting surface. Then, the position of the structural column is determined on the side of the bottom layer away from the main body of the model, and each hanging screw corresponds to a structural column. (2) Print the structural columns and the bottom layer in sequence, and form an internal hole in the structural columns and the bottom layer. The internal hole is coaxially set with the corresponding hanging screw. The inner diameter of the internal hole is less than the outer diameter of the thread of the hanging screw. Rotate the hanging screw to screw it into the internal hole. During the printing interval of the two adjacent curing layers, the hanging screw remains stationary. The material trough is fixedly installed on the worktable. The material trough is rectangular and its inner cavity is divided into a working area and a non-working area surrounding the working area. A scraper is installed in the material trough. The scraper can move from one side of the material trough to the opposite side to push the solid particles deposited at the bottom of the material trough from the working area to the non-working area. In the vertical direction, the projection of the printing platform is located in the working area. When printing structural columns and the bottom layer, after each cured layer is printed, the printing platform is lifted upwards, and after the cured layer separates from the release film of the material tank, the scraper is activated, moving from one side of the material tank to the opposite side, pushing the solid particles deposited at the bottom of the material tank from the working area to the non-working area. (3) Print the main body of the model. After printing the main body of the model, remove the hanging screw from the structural column and remove the model from the printing platform.

7. The 3D printing method according to claim 6, characterized in that, The diameter of the structural column is ≥10mm larger than the outer diameter of the hanging screw.

8. The 3D printing method according to claim 6, characterized in that, D1-D2=(0.5-1)W, where D1 is the outer diameter of the thread of the hanging screw, D2 is the inner diameter of the internal hole, and W is the height of the thread of the hanging screw.

9. The 3D printing method according to claim 6, characterized in that, The height of the structural columns is 2-5mm, and the thickness of the bottom layer is 2-5mm.

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