Printing platform of pull-up DLP type 3D printer and 3D printing method

Abstract

The application provides a printing platform of an upper pull type DLP 3D printer, which comprises a gas source, a lower surface of the printing platform is formed as a working surface, a gas guide hole is formed in the printing platform, and the gas source is communicated with the gas guide hole; a demolding hole communicated with the gas guide hole is formed in a model, and the demolding hole at least penetrates one solidified layer downward; after the solidified layer penetrated by the demolding hole is completed, compressed gas in the gas source can enter the demolding hole through the gas guide hole, so that the release film is gradually peeled from the solidified layer from inside to outside. The application further provides a 3D printing method. During the printing of the model, after the printing of one solidified layer is completed, the compressed gas in the gas source enters the demolding hole through the gas guide hole, so that the release film is peeled from the model from inside to outside; meanwhile, the printing platform lifts the model upward, so that the release film is peeled from the model from outside to inside, a bidirectional peeling mode is formed, and the peeling speed of the release film and the printing speed are improved.

Description

[0001] This application is a divisional application. The original application was filed on March 7, 2025, with application number 2025102672143, and the invention title was: "An Upward-Pull DLP Type 3D Printer and 3D Printing Method". Technical Field

[0002] This invention relates to a printing platform and a 3D printing method for an up-pull DLP type 3D printer. Background Technology

[0003] When a pull-up photopolymer 3D printer is working, it stacks multiple cured layers together to form a product model. To reduce the adhesion between the cured layer and the bottom of the material tank so that the cured layer can be easily peeled off, a release film is usually placed on the bottom of the material tank. However, during the printing platform's ascent, because the cured layer and the release film are in a sealed state, the cured layer needs to overcome the low-pressure area between the release film and the cured layer during the peeling process, making it difficult for the cured layer and the release film to peel off.

[0004] Therefore, to facilitate the peeling of the cured layer from the release film, a tilting peeling method was developed. This method involves tilting the material tank while raising the printing platform, creating a peeling notch on one side of the cured layer. As the notch widens, the release film eventually peels completely off. While the tilting peeling method accelerates the peeling process, the photosensitive resin is prone to overflowing from the material tank when tilted. To prevent this, the depth of the material tank needs to be increased or the liquid volume reduced.

[0005] Therefore, how to accelerate the peeling of the cured layer from the release film to improve printing efficiency remains an issue that needs further improvement in photopolymer 3D printing technology. Summary of the Invention

[0006] To address the problem of low peeling efficiency between the cured layer and the release film in existing technologies and to improve 3D printing efficiency, this application proposes a printing platform for an up-pull DLP 3D printer, which includes an air source. The lower surface of the printing platform is formed as a working surface, and an air guide hole is formed on the printing platform. The air guide hole extends through the upper and lower sides of the printing platform, with the upper end of the air guide hole forming an air inlet and the lower end forming an air outlet.

[0007] The air supply pipe of the air source is connected to the air inlet, and a control valve is installed on the air supply pipe. The model is bonded to the printing platform, and a release hole is formed in the model. The upper end of the release hole is connected to the air outlet. The release hole penetrates at least one curing layer downwards. There is compressed gas in the air source. After the curing layer through which the release hole has been completed, the compressed gas in the air source can enter the release hole through the air guide hole, so that the release film is gradually peeled off from the curing layer from the inside to the outside.

[0008] During the model printing process, after the printing of one cured layer is completed, compressed gas from the air source enters the release liner through the air guide hole, pushing the release film downwards and causing it to peel off from the edge of the release liner. An inner peeling opening is formed between the release film and the cured layer. As compressed gas is continuously injected, the inner peeling opening continues to expand and extend outwards. Simultaneously, the transmission mechanism lifts the model upwards via the printing platform, allowing the release film to peel off along the outer edge of the cured layer, forming an outer peeling opening between the release film and the cured layer. As the model is lifted, the outer peeling opening continues to expand and extend inwards, creating a bidirectional peeling process until the outer and inner peeling openings connect, completely separating the release film from the cured layer. Because the release film can be peeled off simultaneously from both directions, the peeling speed is increased, thereby improving the printing speed.

[0009] Specifically, the printing platform includes a main body and a model plate detachably mounted on the lower end of the main body. The lower surface of the model plate forms a working surface, and the model is bonded to the working surface. The air guide hole includes an upper air hole disposed in the main body and a lower air hole disposed in the model plate. An air guide pipe is inserted into the lower air hole from top to bottom through the upper air hole in a sealed manner. An air supply pipe is connected to the air guide pipe, and the upper end of the demolding hole is connected to the lower air hole.

[0010] The air guide tube passes through the gap between the body and the mold plate, preventing compressed gas from leaking outwards through the gap as it flows through the air guide hole, thus affecting the release film peeling efficiency. Preferably, the air guide tube is screwed onto the printing platform using a threaded method.

[0011] Furthermore, the lower air hole is a stepped hole, with the larger opening facing upwards. The lower end of the air guide tube is sealed against the stepped surface of the stepped hole. The stepped hole is used to prevent the air guide tube from extending downwards due to misoperation. When the air guide tube extends downwards, the distance between the printing platform and the release film is relatively small in the initial stage of printing, making it easy for the air guide tube to press against the release film, causing damage or even puncture, resulting in waste of the release film.

[0012] Furthermore, the control valve is equipped with an opening controller. Using the opening controller, the opening of the control valve can be gradually increased, so that the compressed gas in the air source can slowly enter the demolding hole, avoiding damage or destruction to the model due to a large amount of compressed air suddenly entering the demolding hole. In actual operation, it is necessary to conduct tests on different models to determine the appropriate and safe air intake speed.

[0013] Specifically, the printing platform can be mounted on a connecting arm that engages with the ball screw of the 3D printer. The end of the connecting arm away from the ball screw has two horizontally spaced retaining arms that extend away from the ball screw and are parallel to each other, forming a platform receiving cavity between the two retaining arms. The platform receiving cavity has an opening facing away from the ball screw. Corresponding to each retaining arm, a slot is provided on opposite sides of the printing platform. The printing platform is inserted into the platform receiving cavity, and each retaining arm is inserted into its corresponding slot. Each retaining arm is fixed to the printing platform by bolts.

[0014] In this design, the printing platform is mounted onto the connecting arm using a clamping arm, thereby leaving the top of the printing platform open so that the air duct can extend upwards through the top of the printing platform to facilitate the connection of the air supply pipe.

[0015] Secondly, this application also discloses a 3D printing method, which uses the printing platform of the pull-up DLP type 3D printer described in any of the above claims, and the 3D printing method includes the following steps:

[0016] (1) After the 3D model of the model to be printed is completed, a cylindrical hole area with a set diameter is calculated. The hole area can extend to at least one outer end face of the model to be printed. The outer end face is used as the starting face when printing the model. The model to be printed consists of N curing layers. The hole area extends downward from the starting face by NM curing layers, where N>M.

[0017] (2) Print the model to be printed with the outer end face as the starting face. During the printing process of the curing layer of the model, a demolding hole is formed in the hole forming area. The demolding hole is connected to the air guide hole upward; the demolding hole penetrates the lower end face of the curing layer located at the bottom.

[0018] After each cured layer is printed, the printing platform is lifted upwards, and the control valve is opened to send the gas from the air source into the air guide hole, and then into the release hole, so that the release film peels off outwards along the edge of the release hole until the cured layer is completely separated from the release film. Then the control valve is closed.

[0019] Continue printing the cured layers until NM cured layers have been printed;

[0020] During the printing interval between two adjacent cured layers, the control valve remains closed;

[0021] (3) Complete the printing of the last M curing layers.

[0022] When printing a 3D product model using the 3D printing method described in this application, during the printing of the first NM cured layers, after each cured layer is printed, compressed gas from the gas source is introduced into the release hole through the gas guide hole. Driven by the compressed gas, the release film begins to peel off from the edge of the release hole, forming an inner peeling opening between the release film and the cured layer. As compressed gas continues to be introduced, the inner peeling opening continues to expand and extend outwards. Simultaneously, the transmission mechanism lifts the model upwards via the printing platform, causing the release film to peel off synchronously along the outer edge of the cured layer, forming an outer peeling opening between the release film and the cured layer. As the model is lifted, the outer peeling opening continues to expand and extend inwards, forming a bidirectional peeling method until the outer and inner peeling openings connect, completely separating the release film from the cured layer. Because the release film can be peeled off simultaneously from both directions, the peeling speed of the release film is increased, thereby increasing the printing speed.

[0023] During the printing of the final M cured layers, different processing methods are used depending on the needs. When the air vent penetrates the cured layer located at the bottom of the model without affecting the model's appearance or functionality, a bidirectional peeling method can be used to separate the release film from the final M cured layers. However, when the air vent penetrates the cured layer located at the bottom of the model and would adversely affect the model's appearance or functionality, it is recommended to use the traditional method to separate the release film from the final M cured layers. That is, the air vent should not penetrate the final M cured layers, and the final M cured layers should be used to seal the air vent. After printing the model, remove the model from the printing platform, pour out the photosensitive resin remaining in the air vent through the opening on the starting surface, and clean the air vent.

[0024] Specifically, the stripping hole is straight, and the angle between the stripping hole and the vertical direction is 0-20°. When the angle between the stripping hole and the vertical direction is 0°, the stripping hole extends vertically. During the actual printing process of the model, the tilt angle of the stripping hole can be set according to the shape of the model, but the angle between the stripping hole and the vertical direction should be as close to 0° as possible, so that the photosensitive resin in the stripping hole can flow out smoothly under the push of compressed gas.

[0025] Furthermore, to prevent cracks or ruptures in the model due to the pressure of compressed gas, the diameter of the perforated area is set to be ≥10mm larger than the inner diameter of the release hole. This design ensures that the wall thickness of the release hole is at least 5mm, giving the release hole area high strength and enabling it to withstand the pressure of compressed gas inside the release hole during the peeling process of the release membrane.

[0026] Specifically, the inner diameter of the stripping hole is 5-20mm. During the printing process, photosensitive resin enters the stripping hole. The inner diameter of the stripping hole should not be too small. If the inner diameter is too small, it will not only increase the resistance when the photosensitive resin flows out of the stripping hole, but also cause the photosensitive resin to solidify inside the stripping hole, thus clogging it. The inner diameter of the stripping hole should also not be too large. If the stripping hole is too large, it will easily lead to insufficient strength of the model, affecting the quality of the product.

[0027] Furthermore, the total thickness of the M cured layers is 1-5mm, and the release hole does not penetrate through these M cured layers. The bottom M cured layers form a sealing layer to seal the lower end of the release hole, ensuring the integrity of the model's appearance. When printing the last M cured layers, the release film is still peeled off from the cured layers using the traditional method, relying solely on the rise of the printing platform to complete the peeling. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the structure of an embodiment of the 3D printer in this application.

[0029] Figure 2 yes Figure 1 A view from the center AA direction.

[0030] Figure 3 This is a schematic diagram of the connecting arm.

[0031] Figure 4 This is a diagram showing the state of a 3D printer in operation.

[0032] Figure 5 This is a diagram showing the state when the release film and the cured layer have partially separated.

[0033] Figure 6 This is a diagram showing the state when the release film and the cured layer are completely separated. Detailed Implementation

[0034] Example 1

[0035] Please see Figures 1-3A pull-up DLP 3D printer includes a worktable 11 and an air source 40. A transmission mechanism, employing existing mature technology, is mounted on the worktable 11. 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 threaded onto the ball screw. 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 fixed to the vertical rod. The servo motor drives the ball screw to rotate, enabling the connecting arm to reciprocate the printing platform vertically.

[0036] 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. A material tank 17 is fixedly mounted on the top plate of the workbench and located above the liquid crystal display screen. 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.

[0037] The material trough 17 specifically includes a trough wall 171 extending in a vertical direction and a release film 174 sealed at the bottom of the trough wall. A material trough flange 175 is provided on the outer side of the bottom of the trough wall. Bolts pass through the material trough flange 175 and are screwed onto the worktable to detachably fix the material trough to the worktable.

[0038] In this embodiment, the printing platform 20 includes a body 21 and a model plate 23. A platform flange 22 is provided on the lower side of the body 21. The model plate 23 is detachably installed on the platform flange 22 by bolts. The lower surface of the model plate 23 is formed as a working surface 231.

[0039] 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 body. 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.

[0040] An air duct is provided on the printing platform. In this embodiment, the air duct includes an upper air duct 211 disposed in the main body and a lower air duct 232 disposed in the model plate. The upper air duct 211 and the lower air duct 232 extend vertically and are coaxially arranged. The upper air duct 211 and the lower air duct 232 are connected vertically. The upper air duct 211 penetrates the upper end face of the main body upward, and the lower air duct 232 penetrates the lower end face of the model plate downward. That is, the upper air duct 211 and the lower air duct 232 together constitute the air duct. The air duct penetrates the upper and lower sides of the printing platform. The upper end of the air duct forms an air inlet, and the lower end of the air duct forms an air outlet.

[0041] Since both the upper air hole 211 and the lower air hole 232 extend vertically and are coaxially arranged, the air guide hole extends vertically.

[0042] For ease of connection, a vent pipe 26 is installed on the printing platform. This vent pipe is specifically a stainless steel tube, and it is sealed from top to bottom through an upper vent hole into a lower vent hole. To prevent the vent pipe from extending downwards into the vent hole, in this embodiment, the lower vent hole is a stepped hole with the larger opening facing upwards, creating an upward-facing stepped surface. The lower end of the vent pipe is sealed against this stepped surface. To ensure a tight seal, a rubber sealing ring is placed between the stepped surface and the vent pipe. This prevents compressed gas from leaking outwards through the gap between the body and the model plate as it flows through the vent hole, and also reduces or prevents the resin in the vent hole from seeping into the gap between the body and the model plate. Specifically, in this embodiment, the upper vent hole is a threaded hole, and the liquid guide tube is screwed into this upper vent hole.

[0043] The air source 40 is specifically a compressed air tank that stores compressed air. The exhaust port of the compressed air tank is connected to the air delivery pipe 26 via an air delivery pipe 41. A control valve 42 is installed on the air delivery pipe 41, and an opening controller is installed on the control valve. Specifically, in this embodiment, the control valve is a diaphragm valve with a built-in opening controller.

[0044] Model 30 is bonded to the working surface 231 of the printing platform. A release hole 31 is formed inside the model. The upper end of the release hole 31 is connected to the air outlet, and the release hole penetrates a portion of the cured layer. After the cured layer penetrates through a release hole, gas from the air source can enter the release hole through the air guide hole, causing the release film to gradually peel off from the cured layer from the inside out.

[0045] For details regarding the demolding hole 31, please refer to the relevant content in Example 2 below.

[0046] Example 2

[0047] Please see Figures 4-6This embodiment describes a 3D printing method using the pull-up DLP 3D printer described in Embodiment 1. The 3D printing method includes the following steps:

[0048] (1) After the 3D model of the model to be printed is completed, calculate the cylindrical hole area with a set diameter. Please refer to the following: Figure 2 ,exist Figure 2 In the model 30 shown, model 30 is represented by a dashed line. The area enclosed by the double-dotted line 91 is the hole-forming area. For clarity, the double-dotted line 91 extends upward to the model plate 23 and downward to the bottom of model 30. Also for clarity, no section lines are set for model 30.

[0049] In this embodiment, the membrane removal hole is straight and extends vertically, meaning the angle between the membrane removal hole and the vertical direction is 0°. It is understood that in other embodiments, the membrane removal hole can also be inclined, and the angle between the membrane removal hole and the vertical direction can specifically be 1°, 5°, 8°, 12°, 16°, or 20°, or other angles between 1° and 20°.

[0050] The diameter of the hole-forming area is set to 20mm, and the release hole is a circular hole with an inner diameter of 10mm, making the set diameter of the hole-forming area 10mm larger than the inner diameter of the release hole. The hole-forming area extends to an outer end face 35 of the model to be printed, and the extension direction of the hole-forming area is perpendicular to the outer end face, which can serve as the starting face for model printing. In this embodiment, the model to be printed consists of 1000 cured layers, and the hole-forming area extends downward from the starting face by 990 cured layers, i.e., N=1000, M=10, NM=990, N>M. The thickness of each cured layer is 0.1mm.

[0051] It is understandable that the inner diameter of the demolding hole can also be 5mm, 7mm, or 9mm. When the set diameter of the pore area is larger, the inner diameter of the demolding hole can also be 12mm, 15mm, or 20mm. Of course, depending on the size of the pore area, the inner diameter of the demolding hole can be flexibly selected between 5-20mm.

[0052] (2) Print the model to be printed with the outer end face as the starting face. During the printing process of the curing layer of the model, a demolding hole 31 is formed in the hole area. The demolding hole 31 is connected to the air guide hole upward and penetrates the lower end face of the curing layer located at the bottom side downward.

[0053] After each cured layer is printed, the printing platform is raised upwards while the control valve 42 is slowly opened. This allows compressed air from the compressed air tank to enter the air guide hole, and then into the release hole 31. The compressed air pushes the release film downwards, causing it to peel off along the edge of the release hole until the cured layer is completely separated from the release film. Please refer to [link to relevant documentation]. Figure 5 Due to the adhesive force and the adsorption force generated by the vacuum, when the printing platform is lifted upward, it will drive the corresponding area of ​​the release film 174 upward, so that an outer peeling opening 902 is generated between the outer edge of the cured layer and the release film. At the same time, the compressed air entering the release hole 31 will push the release film downward, causing the release film to peel outward along the edge of the release hole, creating an inner peeling opening 901 between the release film and the cured layer. This allows the release film to be peeled from both the inside and outside of the cured layer, forming a bidirectional peeling method.

[0054] Please see Figure 6 As the inner peeling port 901 and the outer peeling port 902 continue to extend and expand, they become interconnected, allowing the release film to completely peel off from the cured layer. Once the cured layer and the release film are completely peeled off, the control valve is closed.

[0055] Because the release film can be peeled off from both the inside and outside, the peeling efficiency is improved, and the lifting height of the printing platform during release film peeling is reduced, thereby improving printing efficiency.

[0056] When opening the control valve, the opening degree of the control valve needs to be controlled by the opening degree controller so that the opening degree of the control valve gradually increases, so that the compressed gas in the air source can slowly enter the demolding hole, avoiding damage or destruction to the model due to a large amount of compressed air suddenly entering the demolding hole. In specific embodiments, it is necessary to conduct tests on specific models in advance to determine the appropriate and safe air intake speed.

[0057] Continue printing the cured layers until 990 cured layers have been printed, which is equivalent to printing NM cured layers. As printing progresses, the release holes lengthen with the model. During the interval between printing two adjacent cured layers, the control valve remains closed.

[0058] (3) Complete the printing of the last 10 curing layers, that is, complete the printing of the last M curing layers.

[0059] To maintain the integrity of the model's appearance, the M cured layers at the bottom layer together form a sealing layer 32. This sealing layer seals the lower end of the demolding hole to maintain the integrity of the model's appearance. In this embodiment, the sealing layer is composed of the 10 cured layers at the bottom layer, that is, M cured layers together constitute the sealing layer. Please refer to [link / reference] for details. Figure 2In this embodiment, the thickness H of the sealing layer is 1 mm. It can be understood that, depending on different requirements, the thickness of the sealing layer can also be 2 mm, 3 mm, 4 mm or 5 mm, or other thicknesses between 1 and 5 mm.

[0060] When printing the last 10 cured layers, the release film is still peeled off from the cured layer in the traditional way, relying solely on the rise of the printing platform to complete the peeling of the release film from the cured layer.

[0061] After printing the model, remove the model from the printing platform, pour out the photosensitive resin remaining in the air vent through the orifice on the starting surface, and clean the air vent.

Claims

1. The printing platform of an up-pull DLP 3D printer, characterized in that, It includes an air source, the lower surface of the printing platform is formed as the working surface, an air guide hole is opened on the printing platform, the air guide hole runs through the upper and lower sides of the printing platform, the upper end of the air guide hole is formed as the air inlet, and the lower end of the air guide hole is formed as the air outlet. The air supply pipe of the air source is connected to the air inlet, and a control valve is installed on the air supply pipe. The model is bonded to the printing platform, and a release hole is formed in the model. The upper end of the release hole is connected to the air outlet. The release hole penetrates at least one curing layer downwards. There is compressed gas in the air source. After the curing layer through which the release hole has been completed, the compressed gas in the air source can enter the release hole through the air guide hole, so that the release film is gradually peeled off from the curing layer from the inside to the outside.

2. The printing platform according to claim 1, characterized in that, The printing platform includes a main body and a model plate detachably mounted on the lower end of the main body. The lower surface of the model plate forms a working surface, and the model is bonded to the working surface. The air guide hole includes an upper air hole disposed in the main body and a lower air hole disposed in the model plate. An air guide pipe is inserted into the lower air hole from top to bottom through the upper air hole in a sealed manner. An air supply pipe is connected to the air guide pipe. The upper end of the demolding hole is connected to the lower air hole.

3. The printing platform according to claim 2, characterized in that, The lower air inlet is a stepped inlet with the larger opening facing upwards, and the lower end of the air guide tube is sealed against the stepped surface of the stepped inlet.

4. The printing platform according to claim 1, characterized in that, The control valve is equipped with an opening controller.

5. The printing platform according to claim 1, characterized in that, The printing platform can be mounted on a connecting arm that engages with the ball screw of the 3D printer. The end of the connecting arm away from the ball screw has two horizontally spaced retaining arms that extend away from the ball screw and are parallel to each other, forming a platform receiving cavity between the two retaining arms. The platform receiving cavity has an opening facing away from the ball screw. Corresponding to each retaining arm, a slot is provided on opposite sides of the printing platform. The printing platform is inserted into the platform receiving cavity, and each retaining arm is inserted into its corresponding slot. Each retaining arm is fixed to the printing platform with bolts.

6. A 3D printing method, characterized in that, The 3D printing method, using the printing platform of the pull-up DLP type 3D printer according to any one of claims 1-5, includes the following steps: (1) After the 3D model of the model to be printed is completed, a cylindrical hole area with a set diameter is calculated. The hole area can extend to at least one outer end face of the model to be printed, and the outer end face is used as the starting face when printing the model. The model to be printed consists of N curing layers, and the hole-forming area extends downward from the starting surface by NM curing layers, where N > M; (2) Print the model to be printed with the outer end face as the starting face. During the printing process of the curing layer of the model, a demolding hole is formed in the hole forming area. The demolding hole is connected to the air guide hole upward; the demolding hole penetrates the lower end face of the curing layer located at the bottom. After each cured layer is printed, the printing platform is lifted upwards, and the control valve is opened to send the gas from the air source into the air guide hole, and then into the release hole, so that the release film peels off outwards along the edge of the release hole until the cured layer is completely separated from the release film. Then the control valve is closed. Continue printing the cured layers until NM cured layers have been printed; During the printing interval between two adjacent cured layers, the control valve remains closed; (3) Complete the printing of the last M curing layers.

7. The 3D printing method according to claim 6, characterized in that, The membrane detachment holes are straight, and the angle between the membrane detachment holes and the vertical direction is 0-20°.

8. The 3D printing method according to claim 6, characterized in that, The diameter of the pore formation area is set to be ≥10mm larger than the inner diameter of the demolding hole.

9. The 3D printing method according to claim 6, characterized in that, The inner diameter of the stripping hole is 5-20mm.

10. The 3D printing method according to claim 6, characterized in that, The total thickness of the M cured layers is 1-5mm, and the demolding holes do not penetrate the M cured layers.

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