A top-pull DLP 3D printer and 3D printing method

Abstract

The present application proposes a pull-up DLP type 3D printer, which includes a workbench and an air source. A transmission mechanism is installed on the workbench, and a printing platform is installed on the transmission mechanism. An air guide hole is opened on the printing platform, and the air source is connected to the air guide hole; a demolding hole connected to the air guide hole is formed in the model, and the demolding hole penetrates at least one solidified layer downward; after a solidified layer penetrated by the demolding hole is completed, the compressed gas in the air source can enter the demolding hole through the air guide hole, so that the release film is gradually peeled off from the solidified layer from the inside to the outside. The present application also proposes a 3D printing method. During the model printing process, after the printing of a solidified layer is completed, the compressed gas in the air source enters the demolding hole through the air guide hole, so that the release film and the model are peeled off from the inside to the outside; at the same time, the printing platform lifts the model upward, so that the release film and the model are peeled off from the outside to the inside, forming an internal and external bidirectional peeling method, which improves the peeling speed of the release film and the printing speed.

Description

Technical Field

[0001] The present invention relates to a top-pull DLP type 3D printer and a 3D printing method. Background Art

[0002] When a top-up light-curing 3D printer is working, it stacks multiple cured layers together to form a product model. In order to reduce the adhesion between the cured layer and the bottom of the material trough so that the cured layer and the bottom of the material trough can be smoothly peeled off, it is usually necessary to set a release film on the bottom of the material trough. However, during the rising process of the printing platform, since the cured layer and the release film are in a sealed state, the cured layer needs to overcome the low-pressure area generated between the release film and the cured layer during the peeling process, making it difficult for the cured layer and the release film to be peeled off.

[0003] To facilitate the separation of the cured layer from the release film, a tilted peeling method was developed. This method involves tilting the trough while lifting the print platform. This creates a peeling gap on one side of the release film from the cured layer. As the gap widens, the release film and the cured layer are eventually completely separated. While this method can expedite the separation of the cured layer from the release film, the tilted state can easily cause the photosensitive resin to overflow from the trough. To prevent this, the trough depth must be increased or the liquid volume must be reduced.

[0004] Therefore, how to speed up the peeling of the cured layer and the release film to improve printing efficiency is still a problem that needs to be further improved in light-curing 3D printing technology. Summary of the Invention

[0005] In order to solve the problem of low efficiency in peeling off the solidified layer and the release film in the prior art and to improve the efficiency of 3D printing, the present application proposes a top-pull DLP type 3D printer, which includes a workbench and an air source. A transmission mechanism is installed on the workbench, and the transmission mechanism has a ball screw extending in the vertical direction and a connecting arm engaged with the ball screw. The free end of the connecting arm forms a working end, and a printing platform is detachably mounted on the working end. The lower surface of the printing platform forms a working surface, and the connecting arm can drive the printing platform to reciprocate in the vertical direction; an air guide hole is provided on the printing platform, and the air guide hole passes through the upper and lower sides of the printing platform. The upper end of the air guide hole forms an air inlet, and the lower end of the air guide hole forms an air outlet;

[0006] 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 demolding hole is formed in the model. The upper end of the demolding hole is connected to the air outlet, and the demolding hole extends downward through at least one solidified layer. The air source contains compressed gas. After the solidified layer penetrated by the demolding hole is completed, the compressed gas in the air source can enter the demolding hole through the air guide hole, thereby gradually peeling the release film from the inside to the outside of the solidified layer. Preferably, the air guide hole extends in a vertical direction.

[0007] During the model printing process, after a solidified layer is printed, compressed gas from the air source enters the demolding hole through the air guide hole, pushing the release film downward, causing it to peel off from the edge of the demolding hole, forming an inner peeling opening between the release film and the solidified layer. As the compressed gas is continuously injected, the inner peeling opening continues to expand and expand outward. At the same time, the transmission mechanism lifts the model upward through the printing platform, enabling the release film to synchronously peel along the outer edge of the solidified layer, forming an outer peeling opening between the release film and the solidified layer. As the model is lifted, the outer peeling opening continues to expand and expand inward, forming a bidirectional peeling method until the outer peeling opening and the inner peeling opening are connected, completely separating the release film from the solidified layer. Since the release film can be peeled off from both the inner and outer directions, the peeling speed of the release film is increased, thereby increasing the printing speed.

[0008] 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 is formed as a working surface, and the model is bonded to the working surface; the air guide hole includes an upper air hole arranged in the main body and a lower air hole arranged in the model plate. An air guide tube is sealedly inserted into the lower air hole from top to bottom through the upper air hole, the air supply tube is connected to the air guide tube, and the upper end of the demolding hole is connected to the lower air hole.

[0009] The air guide tube can pass through the gap between the main body and the model plate to prevent the compressed gas from leaking out of the gap between the main body and the model plate when flowing through the air guide hole, thereby affecting the release film peeling efficiency. The air guide tube is preferably screwed onto the printing platform using a threaded method.

[0010] Furthermore, the lower air hole is a stepped hole with the larger hole facing upward. The lower end of the air tube sealably presses against the stepped surface of the stepped hole. The stepped hole prevents the air tube from extending downward from the hole due to misoperation. If the air tube extends downward from the hole, the distance between the print platform and the release film is relatively narrow during the initial printing phase, making it easy for the air tube to press against the release film, damaging it or even puncturing it, resulting in waste.

[0011] Furthermore, the control valve is equipped with an opening controller. This controller can gradually increase the opening of the control valve, allowing compressed air from the air source to slowly enter the mold removal hole. This prevents damage or destruction to the mold caused by a sudden influx of compressed air. In actual operation, experiments with different models are required to determine an appropriate and safe air intake speed.

[0012] Specifically, the end of the connecting arm away from the ball screw has two clamping arms arranged at intervals in the horizontal direction. The two clamping arms extend in a direction away from the ball screw and are parallel to each other. A platform accommodating cavity is formed between the two clamping arms. The platform accommodating cavity has an opening facing away from the ball screw. Corresponding to each clamping arm, a clamping slot is provided on opposite sides of the printing platform. The printing platform is inserted into the platform accommodating cavity, and each clamping arm is inserted into the corresponding clamping slot. Each clamping arm is fixed to the printing platform by bolts.

[0013] In this design, the printing platform is mounted on the connecting arm using a clamping arm, thereby leaving the top of the printing platform free so that the air guide hole can pass upward through the top of the printing platform to facilitate the connection of the air supply tube.

[0014] Secondly, the present application also discloses a 3D printing method, characterized in that it is performed using any of the above-mentioned top-pull DLP type 3D printers, and the 3D printing method includes the following steps:

[0015] (1) After the 3D modeling of the model to be printed is completed, a cylindrical hole-forming area with a set diameter is calculated, and the hole-forming area can extend to at least one outer end surface of the model to be printed, and the outer end surface is used as the starting surface when the model is printed; the model to be printed is composed of N solidified layers, and the hole-forming area extends downward from the starting surface by NM solidified layers, where N>M;

[0016] (2) Printing the model to be printed with the outer end surface as the starting surface, forming a demolding hole in the hole-forming area during the printing process of the solidified layer of the model, the demolding hole upwardly connected to the air guide hole; and the demolding hole downwardly penetrates the lower end surface of the solidified layer located at the lowermost side;

[0017] After each solidified layer is printed, the printing platform is lifted up and the control valve is opened at the same time. The gas in the air source is sent to the air guide hole and then into the demolding hole, so that the release film is peeled off along the edge of the demolding hole until the solidified layer and the release film are completely peeled off. Then the control valve is closed.

[0018] Continue printing the solidified layer until NM solidified layers are printed;

[0019] During the printing interval between two adjacent curing layers, the control valve remains closed;

[0020] (3) Complete the printing of the last M solidified layers.

[0021] When the 3D printing method in this application is used to print a model of a 3D product, during the printing process of the first NM solidified layers, after each solidified layer is printed, the compressed gas in the gas source is introduced into the demolding hole through the air guide hole. Under the push of the compressed gas, the release film begins to peel off from the edge of the demolding hole, forming an inner peeling opening between the release film and the solidified layer. As the compressed gas is continuously introduced, the inner peeling opening continues to expand and expand outward. At the same time, the transmission mechanism lifts the model upward through the printing platform, so that the release film begins to peel off along the outer edge of the solidified layer, and forms an outer peeling opening between the release film and the solidified layer. As the model is lifted, the outer peeling opening continues to expand and expand inward, forming an internal and external bidirectional peeling method, until the outer peeling opening and the inner peeling opening are connected to each other, so that the release film and the solidified layer are completely peeled off. Since the release film can be peeled off from both the internal and external directions at the same time, the peeling speed of the release film is improved, thereby increasing the printing speed.

[0022] When printing the last M solidified layers, different processing methods are adopted according to different needs. When the air guide holes penetrate downward through the solidified layer located at the bottom of the model and do not affect the appearance and usability of the model, the internal and external bidirectional peeling method can be continued to be used to complete the peeling of the release film and the last M solidified layers. However, when the air guide holes penetrate downward through the solidified layer located at the bottom of the model and have an adverse effect on the appearance or usability of the model, it is recommended to continue to use the traditional method to complete the peeling of the release film and the last M solidified layers. That is, the air guide holes do not penetrate downward into the last M solidified layers, and the last M solidified layers are used to complete the sealing of the air guide holes. After the model is printed, after removing the model from the print platform, pour out the photosensitive resin retained in the air guide holes from the hole located on the starting surface, and clean the air guide holes.

[0023] Specifically, the demolding hole is linear, with an angle between the hole and the vertical direction ranging from 0° to 20°. When the angle between the hole and the vertical direction is 0°, the hole extends vertically. During the specific printing process of the model, the inclination angle of the demolding hole can be adjusted according to the shape of the model, but the angle between the hole and the vertical direction should be kept close to 0° as much as possible to ensure that the photosensitive resin in the hole can flow smoothly out of the hole under the pressure of the compressed gas.

[0024] Furthermore, to prevent cracks or ruptures in the mold due to compressed gas pressure, the diameter of the hole-forming area is set to be ≥10mm larger than the inner diameter of the demolding hole. This design ensures a wall thickness of at least 5mm, giving the demolding hole area greater strength to withstand the pressure of the compressed gas in the demolding hole during the release film peeling process.

[0025] Specifically, the inner diameter of the demolding hole is 5-20mm. During the printing process, photosensitive resin will enter the demolding hole. The inner diameter of the demolding hole should not be too small. If the inner diameter of the demolding hole is too small, it will not only increase the resistance to the photosensitive resin flowing out of the hole, but also cause the photosensitive resin to solidify inside the demolding hole, thereby clogging the hole. The inner diameter of the demolding hole should also not be too large. If the inner diameter of the demolding hole is too large, it will easily lead to insufficient strength of the model, affecting the quality of the product.

[0026] Furthermore, the total thickness of the M solidified layers is 1-5 mm, and the demolding hole does not penetrate through the M solidified layers. The M solidified layers at the bottom form a sealing layer, which is used to seal the lower end of the demolding hole to ensure the integrity of the model's appearance. When printing the last M solidified layers, the release film and solidified layers are still separated using the traditional method, relying solely on the rise of the printing platform to complete the separation. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a structural diagram of an embodiment of a 3D printer in this application.

[0028] Figure 2 yes Figure 1 Center AA view.

[0029] Figure 3 It is a structural diagram of the connecting arm.

[0030] Figure 4 This is a state diagram of the 3D printer when it is working.

[0031] Figure 5 This is a diagram showing the state when the release film and the cured layer are partially peeled off.

[0032] Figure 6 This is a diagram showing the state when the release film and the cured layer are completely peeled off. DETAILED DESCRIPTION

[0033] Example 1

[0034] See also Figure 1-Figure 3, a top-pull DLP type 3D printer, which includes a workbench 11 and an air source 40. A transmission mechanism is installed on the workbench 11, and the transmission mechanism adopts existing mature technology. The transmission mechanism includes a vertical pole 12 fixed on the workbench 11 and a ball screw 13 rotatably installed on one side of the vertical pole. The ball screw 13 extends in the vertical direction, and one end of the connecting arm 14 is engaged with the ball screw through a screw hole. The connecting arm 14 extends in the horizontal direction, and the printing platform 20 is detachably mounted on the end of the connecting arm 14 away from the ball screw. A servo motor 15 is installed at the lower end of the ball screw. The servo motor is fixedly mounted on the vertical pole. The servo motor can drive the ball screw to rotate, so that the connecting arm can drive the printing platform to move back and forth in the vertical direction.

[0035] A liquid crystal 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. This irradiation unit 19 is fixedly mounted on the bottom plate 113 of the workbench and is located below the liquid crystal screen 191. A material trough 17 is fixedly mounted on the top plate of the workbench and is located above the liquid crystal screen. The irradiation unit 19 provides a shaped light beam for curing the photosensitive resin in the material trough 17. Irradiation unit 19 can be, but is not limited to, a digital light processing (DLP) projector or other types of projection devices (such as LCOS, LCD).

[0036] The material trough 17 specifically includes a trough wall 171 extending in the 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 workbench to detachably fix the material trough on the workbench.

[0037] In this embodiment, the printing platform 20 includes a main body 21 and a model plate 23. A platform flange 22 is provided on the lower side of the main body 21. The model plate 23 is detachably mounted on the platform flange 22 by bolts. The lower surface of the model plate 23 is formed as a working surface 231.

[0038] In this embodiment, two holding arms 141 are arranged at intervals in the horizontal direction at one end of the connecting arm 14 away from the ball screw. The two holding arms 141 extend in a direction away from the ball screw and are parallel to each other. A platform accommodating cavity 142 is formed between the two holding arms. The platform accommodating cavity has an opening facing away from the ball screw. Corresponding to each holding arm 141, a clamping groove 25 is respectively provided on the opposite sides of the main body. The printing platform 20 is inserted into the platform accommodating cavity 142, and each holding arm 141 is inserted into the corresponding clamping groove 25. The first bolt 16 passes through the holding arm and is screwed into the first screw hole 251 located in the clamping groove, so that the holding arm is detachably fixed to the printing platform. To avoid shaking, each holding arm is fixed to the printing platform by two first bolts.

[0039] An air guide hole is provided on the printing platform. In this embodiment, the air guide hole includes an upper air hole 211 provided in the main body and a lower air hole 232 provided in the model plate. The upper air hole 211 and the lower air hole 232 both extend in the vertical direction and are coaxially arranged. The upper air hole 211 and the lower air hole 232 are connected up and down, and the upper air hole 211 passes through the upper end surface of the main body upward, and the lower air hole 232 passes through the lower end surface of the model plate downward, that is, the upper air hole 211 and the lower air hole 232 together constitute the air guide hole, and the air guide hole passes through the upper and lower sides of the printing platform, the upper end of the air guide hole forms an air inlet, and the lower end of the air guide hole forms an air outlet.

[0040] Since the upper air hole 211 and the lower air hole 232 both extend in the vertical direction and are coaxially arranged, the air guide hole extends in the vertical direction.

[0041] To facilitate connection, an air duct 26 is installed on the printing platform. Specifically, the air duct is a stainless steel tube. The air duct is sealedly inserted from top to bottom through the upper air hole into the lower air hole. To prevent the air duct from extending downward from the air hole, in this embodiment, the lower air hole is a stepped hole with the large hole facing upward, resulting in an upward-facing stepped surface. The lower end of the air duct sealably presses against the stepped surface of the stepped hole. To ensure sealing, a rubber sealing ring is placed between the stepped surface and the air duct. This not only prevents compressed gas from leaking out of the gap between the body and the mold plate when flowing through the air duct, but also reduces or prevents sensitive resin in the air duct from seeping into the gap between the body and the mold plate. Specifically, in this embodiment, the upper air hole is a threaded hole, and the liquid duct is screwed into the upper air hole.

[0042] The air source 40 is specifically a compressed air storage tank storing compressed air. The exhaust port of the compressed air storage tank is connected to the air guide pipe 26 via an air supply pipe 41. A control valve 42 is installed on the air supply 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.

[0043] Model 30 is bonded to the work surface 231 of the print platform. A release hole 31 is formed within the model. The upper end of the release hole 31 is connected to the air outlet, and the release hole extends downward through a portion of the solidified layer. After a solidified layer is formed through the release hole, gas from the air source enters the release hole through the air guide hole, gradually peeling the release film from the inside out.

[0044] For details about the demolding hole 31 , please refer to the relevant content in Example 2 below.

[0045] Example 2

[0046] See also Figure 4-Figure 6This embodiment describes a 3D printing method. The 3D printing method is performed using the top-pull DLP 3D printer in Embodiment 1. The 3D printing method includes the following steps:

[0047] (1) After the 3D modeling of the model to be printed is completed, the cylindrical hole area with a set diameter is calculated. Please also refer to Figure 2 ,exist Figure 2 In the model 30 shown, the model 30 is represented by a dotted line. The area enclosed by the double-dashed line 91 is the hole-forming area. For clarity, the double-dashed line 91 extends upward to the model plate 23 and downward to the bottom of the model 30. For clarity, the model 30 is not provided with a cross-hatching line.

[0048] In this embodiment, the film removal holes are linear and extend in the vertical direction, i.e., the angle between the film removal holes and the vertical direction is 0°. It is understood that in other embodiments, the film removal holes can be arranged at an angle, and the angle between the film removal holes and the vertical direction can specifically be 1°, 5°, 8°, 12°, 16°, or 20°, and of course other angles between 1-20° are also possible.

[0049] The set diameter of the hole-forming area is 20 mm, and the demolding hole is a circular hole with an inner diameter of 10 mm, so that the set diameter of the hole-forming area is 10 mm larger than the inner diameter of the demolding hole. The hole-forming area extends to an outer end face 35 of the model to be printed. The extension direction of the hole-forming area is perpendicular to the outer end face, and the outer end face can serve as the starting surface when the model is printed. In this embodiment, the model to be printed is composed of 1000 solidified layers, and the hole-forming area extends downward from the starting surface by 990 solidified layers, that is, N = 1000, M = 10, NM = 990, and N>M. The thickness of each solidified layer is 0.1 mm.

[0050] It is understood that the inner diameter of the demolding hole can also be 5mm, 7mm, or 9mm. When the diameter of the hole-forming area is set larger, the inner diameter of the demolding hole can also be 12mm, 15mm, or 20mm. Of course, depending on the size of the hole-forming area, the inner diameter of the demolding hole can be flexibly selected between 5-20mm.

[0051] (2) The model to be printed is printed with the outer end surface as the starting surface. During the printing process of the solidified layer of the model, a demolding hole 31 is formed in the hole forming area. The demolding hole 31 is connected to the air guide hole upward, and the demolding hole downward passes through the lower end surface of the solidified layer located at the lower side.

[0052] After each solidified layer is printed, the printing platform is lifted upwards and the control valve 42 is slowly opened to allow the compressed air in the compressed air tank to be sent into the air guide hole and then into the demolding hole 31. The compressed air is used to push the release film downwards, causing the release film to peel outwards along the edge of the demolding hole until the solidified layer and the release film are completely separated. Figure 5 Due to the adhesive force and the adsorption force generated by the vacuum, when the printing platform is lifted upward, the corresponding area of ​​the release film 174 will be lifted upward, so that an external peeling opening 902 is generated between the outer edge of the solidified layer and the release film. At the same time, the compressed air entering the demolding hole 31 will push the release film downward, causing the release film to be peeled off outward along the edge of the demolding hole, and an internal peeling opening 901 is generated between the release film and the solidified layer. The release film can be peeled off from both the inside and outside directions of the solidified layer, forming an internal and external bidirectional peeling method.

[0053] See also Figure 6 As the inner peeling opening 901 and the outer peeling opening 902 continue to extend and expand, the inner peeling opening 901 and the outer peeling opening 902 are connected to each other, so that the release film is completely peeled off from the solidified layer. When the solidified layer and the release film are completely peeled off, the control valve is closed.

[0054] Since the release film can be peeled off from both the inside and outside directions, the peeling efficiency is improved, and the lifting height of the printing platform when the release film is peeled off can be reduced, thereby improving the printing efficiency.

[0055] When opening the control valve, it is necessary to use an opening controller to control the opening of the control valve so that the opening 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 a specific embodiment, it is necessary to conduct experiments on the specific model in advance to determine an appropriate and safe air intake speed.

[0056] Continue printing solidified layers until 990 solidified layers are complete, meaning NM solidified layers have been printed. As printing progresses, the demolding hole lengthens as the model lengthens. The control valve remains closed during the interval between printing two consecutive solidified layers.

[0057] (3) The printing of the last 10 solidified layers is completed, that is, the printing of the last M solidified layers is completed.

[0058] In order to maintain the integrity of the model appearance, the M solidified layers at the bottom together form a sealing layer 32, which seals the lower end of the demoulding hole to maintain the integrity of the model appearance. In this embodiment, the sealing layer is composed of the 10 solidified layers at the bottom, that is, the M solidified layers together constitute the sealing layer. For details, please refer to Figure 2In this embodiment, the thickness H of the sealing layer is 1 mm. It is understood that, according to different requirements, the thickness of the sealing layer can also be 2 mm, 3 mm, 4 mm or 5 mm, or other thicknesses between 1-5 mm.

[0059] When printing the last 10 solidified layers, the release film and the solidified layer are still peeled off in the traditional way, relying solely on the rise of the printing platform to complete the peeling of the release film and the solidified layer.

[0060] After the model is printed, remove the model from the printing platform, pour out the photosensitive resin retained in the air holes from the opening on the starting surface, and clean the air holes.

Claims

1. A top-pull DLP 3D printer, characterized in that: The invention comprises a workbench and an air source, wherein a transmission mechanism is mounted on the workbench, the transmission mechanism comprising a ball screw extending in a vertical direction and a connecting arm engaged with the ball screw, the free end of the connecting arm forming a working end, a printing platform being detachably mounted on the working end, the lower surface of the printing platform forming a working surface, and the connecting arm being capable of driving the printing platform to reciprocate in a vertical direction; an air guide hole is provided on the printing platform, the air guide hole penetrating the upper and lower sides of the printing platform, the upper end of the air guide hole forming an air inlet, and the lower end of the air guide hole forming an 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 demolding hole is formed in the model. The upper end of the demolding hole is connected to the air outlet, and the demolding hole penetrates at least one solidified layer downward. The air source contains compressed gas. After a solidified layer penetrated by the demolding hole is completed, the compressed gas in the air source can enter the demolding hole through the air guide hole, so that the release film is gradually peeled off from the solidified layer from the inside to the outside. The printing platform includes a body and a model plate detachably mounted at the lower end of the body. The lower surface of the model plate forms a working surface, to which the model is bonded. The air guide holes include an upper air hole provided in the body and a lower air hole provided in the model plate. An air guide tube is sealedly inserted from top to bottom through the upper air hole into the lower air hole. The air supply tube is connected to the air guide tube, and the upper end of the demolding hole is connected to the lower air hole. The lower air hole is a stepped hole with a large hole facing upwards, and the lower end of the air guide tube is sealed against the stepped surface of the stepped hole.

2. The top-pull DLP 3D printer according to claim 1, characterized in that: The control valve is equipped with an opening controller.

3. The top-pull DLP 3D printer according to claim 1, characterized in that: The end of the connecting arm away from the ball screw has two holding arms arranged at intervals in the horizontal direction. The two holding arms extend in a direction away from the ball screw and are parallel to each other. A platform accommodating cavity is formed between the two holding arms. The platform accommodating cavity has an opening facing away from the ball screw. Corresponding to each holding arm, a card slot is provided on opposite sides of the printing platform. The printing platform is inserted into the platform accommodating cavity, and each holding arm is inserted into the corresponding card slot. Each holding arm is fixed to the printing platform by bolts.

4. A 3D printing method, characterized in that: The 3D printing method is performed using the top-pull DLP 3D printer according to any one of claims 1 to 3, and comprises the following steps: (1) After the 3D modeling of the model to be printed is completed, a cylindrical hole-forming area with a set diameter is calculated, and the hole-forming area can extend to at least one outer end surface of the model to be printed, and the outer end surface is used as the starting surface for model printing; The model to be printed consists of N solidified layers, and the hole-forming area extends NM solidified layers downward from the starting surface, where N>M; (2) Printing the model to be printed with the outer end surface as the starting surface, forming a demolding hole in the hole forming area during the printing process of the solidified layer of the model, the demolding hole is connected to the air guide hole upward; the demolding hole penetrates the lower end surface of the solidified layer located at the lowermost side downward; After each solidified layer is printed, the printing platform is lifted up and the control valve is opened at the same time. The gas in the air source is sent to the air guide hole and then into the demolding hole, so that the release film is peeled off along the edge of the demolding hole until the solidified layer and the release film are completely peeled off. Then the control valve is closed. Continue printing the solidified layer until NM solidified layers are printed; During the printing interval between two adjacent curing layers, the control valve remains closed; (3) Complete the printing of the last M solidified layers.

5. The 3D printing method according to claim 4, characterized in that: The film stripping hole is straight, and the angle between the film stripping hole and the vertical direction is 0-20°.

6. The 3D printing method according to claim 4, characterized in that: The set diameter of the hole forming area is ≥10mm larger than the inner diameter of the demolding hole.

7. The 3D printing method according to claim 4, characterized in that: The inner diameter of the demoulding hole is 5-20mm.

8. The 3D printing method according to claim 4, characterized in that: The total thickness of the M solidified layers is 1-5 mm, and the demoulding holes do not penetrate the M solidified layers.

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