3D printer with center pull-down stripping function and 3D printing method

Abstract

The 3D printer with the center pull-down stripping function comprises a workbench and a center stripping mechanism, a transmission mechanism is installed on the workbench, a printing platform is installed on the transmission mechanism, an air guide hole is formed in the printing platform, a model is bonded to the printing platform, a demolding hole communicated with the air guide hole is formed in the model, and the center stripping mechanism is installed on the center stripping mechanism. An adsorber of the center stripping mechanism can move between a working position and a parking position, when the adsorber is located at the working position, the adsorber can adsorb the release film right opposite to the air guide hole, and when the adsorber is located at the parking position, the adsorber is located on the outer side of the projection of the printing platform in the vertical direction. The invention further discloses a 3D printing method. And after printing of one curing layer is completed, the adsorber moves to a working position to adsorb the release film, so that the release film and the curing layer are stripped from inside to outside, meanwhile, the release film and the curing layer are stripped from outside to inside, a bidirectional stripping mode is formed, and the stripping speed and the printing speed are increased.

Description

Technical Field

[0001] The present invention relates to a 3D printer with a central downward peeling function and a 3D printing method. Background Art

[0002] When an upward-pulling stereolithography 3D printer is working, every time a cured layer is formed on the printing platform, the printing platform needs to be lifted to separate the cured layer from the release film and make a distance equal to the thickness of a cured layer between the cured layer and the release film, so as to facilitate the formation of the next cured layer, and thus gradually stack the cured layers until the printing of the model is completed.

[0003] Since each cured layer is hermetically connected to the release film after printing, and since the space between the cured layer and the release film is in a sealed state, when the cured layer is peeled off from the release film, it is necessary to overcome the low-pressure area generated by the atmospheric pressure between the release film and the cured layer, resulting in difficulty in peeling the cured layer from the release film. During the peeling process, the release film is gradually peeled off from the periphery to the center of the cured layer, resulting in low peeling efficiency and also limiting the improvement of the printing efficiency.

[0004] In order to improve the peeling efficiency of the cured layer from the release film, an inclined peeling method has emerged. The inclined peeling method is to tilt the material tank while lifting the printing platform upward, so as to generate a peeling notch on one side of the cured layer from the release film. As the peeling notch gradually expands, finally the release film is completely peeled off from the cured layer. Although the inclined peeling method can accelerate the peeling of the cured layer from the release film, in the inclined state, the photosensitive resin is likely to overflow from the material tank. To avoid the overflow of the photosensitive resin, it is necessary to increase the depth of the material tank or reduce the liquid holding capacity of the material tank.

[0005] Therefore, how to accelerate the peeling of the cured layer from the release film to improve the printing efficiency remains a problem that needs to be continuously improved in the stereolithography 3D printing technology. Summary of the Invention

[0006] To solve the problem of low peeling efficiency between the cured layer and the release film in the prior art and improve the 3D printing efficiency, the present application proposes a 3D printer with a central downward peeling function, which includes a workbench and a central peeling mechanism. A transmission mechanism is installed on the workbench. 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 installed 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; A vent hole is formed in the printing platform, and the vent hole penetrates through the upper and lower sides of the printing platform. The upper end of the vent hole forms an air inlet, and the lower end of the vent hole forms an air outlet;

[0007] The center peeling mechanism includes a vacuum device, an adsorber, and a swinging device. The vacuum device is fixedly installed in the inner cavity of the workbench. The adsorber has adsorption holes, and the adsorption holes communicate with the vacuum port of the vacuum device. The swinging device is installed on the workbench, and the adsorber is installed on the swinging device. The swinging device can drive the adsorber to swing between the working position and the parking position.

[0008] A material trough is arranged on the workbench. The printing platform can enter the material trough and print a model on its working surface. The model is bonded to the printing platform, and a demolding hole is formed in the model. The upper end of the demolding hole communicates with the air outlet, and the demolding hole penetrates at least one curing layer downward. When the adsorber is in the working position, the adsorption hole is directly below the lower port of the demolding hole. When the adsorber is in the parking position, the adsorber is located outside the projection of the printing platform in the vertical direction.

[0009] When a curing layer penetrated by the demolding hole is completed, the adsorber can be in the working position and can adsorb the release film opposite to the lower port of the demolding hole. When the transmission mechanism drives the printing platform to move upward, the release film can be peeled off from the inner edge to the outer edge along the lower edge of the demolding hole with the curing layer.

[0010] During the model printing process, when a curing layer is printed, the swinging device is started immediately to move the adsorber from the parking position to the working position. Using the adsorption force generated by the vacuum device, the release film opposite to the lower port of the demolding hole is adsorbed on the adsorber. Due to the fixing effect of the adsorber, the part of the release film adsorbed by the adsorber remains in place. When the transmission mechanism drives the printing platform to move upward, an inner peeling opening can be generated between the lower port edge of the demolding hole and the curing layer for the release film to peel off from the inside to the outside. At the same time, due to the limitation of the groove wall of the material trough, an outer peeling opening can also be generated between the outer edge of the model and the curing layer for the release film. As the model is lifted, the inner peeling opening continuously expands and expands outward, and the outer peeling opening continuously expands and expands inward, forming a two-way peeling method inside and outside until the outer peeling opening and the inner peeling opening communicate with each other, so that the release film is completely peeled off from the curing layer. Since the release film can be peeled off from two directions inside and outside at the same time, the peeling speed of the release film is increased, and thus the printing speed can be increased.

[0011] Furthermore, to avoid friction between the adsorber and the release film, which affects the light transmittance and reduces the service life of the release film, the distance between the upper surface of the adsorber and the lower surface of the release film is 0.1 - 0.5 mm.

[0012] Specifically, one 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 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 groove is respectively arranged on the 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 groove. Each clamping arm is fixed to the printing platform by bolts. In this design, the printing platform is installed on the connecting arm by using the clamping arms, so that the top of the printing platform is vacated, enabling the air guide hole to penetrate upward through the top of the printing platform and communicate with the atmosphere.

[0013] Specifically, for easy control, the swinging device includes a swinging motor, which is a servo motor. The swinging motor is fixed in the inner cavity of the workbench, and the output shaft of the swinging motor extends upward out of the top plate of the workbench. The air inlet pipe of the adsorber is fixed to the output shaft of the swinging motor.

[0014] Furthermore, the adsorber includes a circular adsorption disc. The adsorption disc has a hollow cavity inside. The central part of the upper surface of the adsorption disc is recessed downward to form an adsorption cavity with an arc-shaped bottom surface. The adsorption holes communicate the hollow cavity and the adsorption cavity. When the adsorption disc adsorbs on the release film, the release film will be recessed downward and closely adhere to the upper surface of the adsorption cavity, so that a downwardly protruding concave shape is formed in the corresponding area of the release film, which is beneficial to generating an internal peeling opening between the lower edge of the air guide hole and the cured layer of the release film, and is beneficial to accelerating the peeling speed of the release film from the cured layer.

[0015] Secondly, the present application also discloses a 3D printing method, which is carried out by using the 3D printer described in any one of the above. The 3D printing method includes the following steps:

[0016] (1) After the 3D modeling of the model to be printed is completed, a cylindrical hole-forming area with a set diameter is calculated. The hole-forming area can at least extend to one outer end surface of the model to be printed, and this outer end surface is used as the starting surface when printing the model; the model to be printed is composed of N cured layers, and the hole-forming area extends downward from the starting surface for N - M cured layers, where N > M;

[0017] (2) Printing the model to be printed with this outer end surface as the starting surface. During the printing process of the cured layer of the model, a demolding hole is formed in the hole-forming area. The demolding hole communicates with the air guide hole upward; the demolding hole penetrates downward through the lower end surface of the lowermost cured layer;

[0018] After each cured layer is printed, start the swinging device to move the adsorber from the parked position to the working position. Start the vacuum device to adsorb the release film onto the adsorber. Then start the transmission mechanism to lift the printing platform upward, so that the release film is peeled outward along the lower edge of the demolding hole, and at the same time the release film is peeled inward along the outer edge of the model until the cured layer is completely peeled from the release film. Turn off the vacuum device, and the release film detaches from the adsorber. Start the swinging device again to move the adsorber from the working position to the parked position;

[0019] Continue to print the cured layers until the printing of N - M cured layers is completed;

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

[0021] When using the 3D printing method in this application to print the model of a 3D product, during the printing process of the first N - M cured layers, after each cured layer is printed, start the swinging device to move the adsorber from the parked position to the working position. Utilize the adsorption force generated by the vacuum device to adsorb the release film opposite the lower port of the demolding hole onto the adsorber. Due to the fixing effect of the adsorber, the part of the release film adsorbed by the adsorber remains in place. When the transmission mechanism drives the printing platform to move upward, since the air guide hole is directly connected to the atmosphere, the negative pressure of the release film in the area corresponding to the lower port of the demolding hole is eliminated, and an inner peeling opening can be generated between the lower edge of the demolding hole and the cured layer for the release film to peel from the inside out; at the same time, due to the limitation of the groove wall of the material tank, the release film can also generate an outer peeling opening between the outer edge of the model and the cured layer. As the model is lifted, the inner peeling opening continuously expands and expands outward, and the outer peeling opening continuously expands and expands inward, forming a two-way peeling method inside and outside until the outer peeling opening and the inner peeling opening are interconnected, so that the release film is completely peeled from the cured layer. Since the release film can be peeled from both the inside and outside directions simultaneously, the peeling speed of the release film is increased, thereby improving the printing speed.

[0022] When printing the last M cured layers, different treatment methods are adopted according to different needs. When the air guide hole penetrates downward through the cured layer at the lowest side of the model and does not affect the appearance and use function of the model, the two-way peeling method inside and outside can continue to be used to complete the peeling of the release film from the last M cured layers. However, when the air guide hole penetrates downward through the cured layer at the lowest side of the model and has an adverse effect on the appearance or use function of the model, it is recommended to still use the traditional method to complete the peeling of the release film from the last M cured layers, that is, the air guide hole does not penetrate downward into the last M cured layers, and the last M cured layers are used to complete the sealing of the air guide hole. After the model is printed and taken off the printing platform, the photosensitive resin remaining in the air guide hole is poured out from the hole opening at the starting surface, and the air guide hole is cleaned.

[0023] Specifically, during the peeling process of the release film and the cured layer, the photosensitive resin in the demolding holes can flow downward smoothly, and the demolding holes are linear and extend in the vertical direction.

[0024] Furthermore, the set diameter of the pore-forming area is ≥10 mm larger than the inner diameter of the demolding holes. This design enables the wall thickness of the demolding holes to be at least 5 mm, endowing the area of the demolding holes with relatively high strength.

[0025] Specifically, the inner diameter of the demolding holes is 5 - 20 mm. During the printing process, the photosensitive resin will enter the demolding holes. The inner diameter of the demolding holes should not be too small. When the inner diameter is too small, it will not only increase the resistance of the photosensitive resin flowing out of the demolding holes but also cause the photosensitive resin to solidify in the demolding holes, thus blocking the demolding holes. The inner diameter of the demolding holes should not be too large either. When the demolding holes are too large, it is likely to lead to insufficient strength of the model, affecting the quality of the product.

[0026] Furthermore, the total thickness of the M cured layers is 1 - 5 mm, and the demolding holes do not penetrate through the M cured layers. A closed layer is formed by using the M cured layers located at the lowermost side, and this closed layer is used to seal the lower end of the demolding holes to ensure the integrity of the model appearance. When printing the last M cured layers, the peeling of the release film and the cured layer still adopts the traditional method, and the peeling is completed only by the rising of the printing platform. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a schematic structural diagram of an embodiment of a 3D printer in the present application.

[0028] Figure 2 is Figure 1 the view in the A - A direction in

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

[0030] Figure 4 is Figure 1 the view in the B - B direction in

[0031] Figure 5 is Figure 1 the enlarged view of part C in

[0032] Figure 6 is a state diagram when the 3D printer is working.

[0033] Figure 7 is a state diagram when the partial peeling of the release film and the cured layer is completed.

[0034] Figure 8 is a state diagram when the release film and the cured layer are completely peeled off. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0035] Embodiment 1

[0036] Please refer to Figures 1-5 , a 3D printer with a central downward peeling function, which includes a workbench 11 and a central peeling mechanism 40. A transmission mechanism is installed on the workbench 11, and this transmission mechanism adopts existing mature technologies. The transmission mechanism includes a vertical rod 12 fixed on the workbench 11 and a ball screw 13 rotatably installed on one side of the vertical rod. The ball screw 13 extends in the vertical direction, and one end of a connecting arm 14 is engaged on the ball screw through a threaded hole. The connecting arm 14 extends in the horizontal direction, and a printing platform 20 is detachably installed at 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 installed on the vertical rod, and the servo motor can drive the ball screw to rotate, so that the connecting arm can drive the printing platform to reciprocate in the vertical direction.

[0037] A liquid crystal display screen 191 is fixedly installed on the top plate 111 of the workbench 11, and an irradiation unit 19 is fixedly installed in the inner cavity 112 of the workbench 11. The irradiation unit 19 is fixed on the bottom plate 113 of the workbench, and the irradiation unit 19 is located below the liquid crystal display screen 191.

[0038] A support ring 114 is arranged on the top plate 111 of the workbench. A material tank 17 is fixedly installed on the top of the support ring 114 and is located above the liquid crystal display screen. The irradiation unit provides a forming light beam for curing the photosensitive resin in the material tank 17. The irradiation unit 19 can be a digital light processing (DLP) projection device or other types of projection devices (such as LCOS, LCD), but is not limited thereto.

[0039] The material tank 17 specifically includes a tank wall 171 extending in the vertical direction and a release film 174 hermetically arranged at the bottom of the tank wall. A material tank flange 175 is arranged on the outside of the bottom of the tank wall. After a bolt passes through the material tank flange 175, it is screwed onto the support ring to detachably fix the material tank on the support ring. The printing platform can enter the material tank and print a model on its working surface.

[0040] In this embodiment, the printing platform 20 includes a body 21 and a model plate 23. A platform flange 22 is arranged on the lower side of the body 21, and the model plate 23 is detachably installed on the platform flange 22 by bolts. The lower surface of the model plate 23 forms a working surface 231.

[0041] In this embodiment, at one end of the connecting arm 14 away from the ball screw, there are two clamping arms 141 arranged at intervals in the horizontal direction. The two clamping arms 141 extend away from the ball screw and are parallel to each other. A platform accommodation cavity 142 is formed between the two clamping arms. The platform accommodation cavity has an opening facing away from the ball screw. Corresponding to each clamping arm 141, a clamping groove 25 is respectively arranged on the opposite sides of the body. The printing platform 20 is inserted into the platform accommodation cavity 142, and each clamping arm 141 is inserted into the corresponding clamping groove 25. The first bolt 16 passes through the clamping arm and is screwed into the first screw hole 251 located in the clamping groove, detachably fixing the clamping arm on the printing platform. To avoid shaking, each clamping arm is fixed to the printing platform by two first bolts.

[0042] A vent hole is provided on the printing platform. In this embodiment, the vent hole includes an upper air hole 211 arranged in the body and a lower air hole 232 arranged in the template. 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 vertically communicated. The upper air hole 211 penetrates upward through the upper end face of the body, and the lower air hole 232 penetrates downward through the lower end face of the template. That is, the upper air hole 211 and the lower air hole 232 together form the vent hole, and the vent hole penetrates through the upper and lower sides of the printing platform. The upper end of the vent hole forms an air inlet, and the lower end of the vent hole forms an air outlet.

[0043] Since the upper air hole 211 and the lower air hole 232 both extend in the vertical direction and are coaxially arranged, the vent hole extends in the vertical direction.

[0044] The central peeling mechanism includes a vacuum device 41, an adsorber 45 and a swing device 50. In this embodiment, the vacuum device 41 specifically uses a Roots vacuum pump, and the Roots vacuum pump is fixedly installed in the inner cavity 112 of the workbench.

[0045] The adsorber 45 includes a circular adsorption disc 451. The adsorption disc is horizontal, and the outer peripheral surface of the adsorption disc is arc-shaped. The adsorption disc has a hollow cavity 452 inside. The central part of the upper surface of the adsorption disc is recessed downward to form an adsorption cavity 453 with an arc-shaped bottom surface. A plurality of adsorption holes 454 are arranged on the upper wall of the adsorption disc. The plurality of adsorption holes are arranged in the area where the adsorption cavity is located, and the adsorption holes communicate the hollow cavity and the adsorption cavity.

[0046] The swing device 50 includes a swing motor 51, which is a servo motor. The swing motor is fixed on the lower surface of the top plate of the workbench, so that the swing motor is located in the inner cavity of the workbench, and the output shaft 52 of the swing motor 51 extends upward through the top plate of the workbench. One end of the vacuum pipe 44 is welded with a connecting cross bar 43, and a positioning hole is provided at the end of the connecting cross bar away from the vacuum pipe. The connecting cross bar is sleeved on the output shaft 52 of the swing motor 51 through the positioning hole, and the set screw 53 is screwed on the hole wall of the positioning hole, and the set screw 53 tightly presses against the output shaft of the swing motor 51 after passing through the hole wall of the positioning hole, so that the vacuum pipe is fixed on the output shaft of the swing motor 51 through the connecting cross bar. A notch 115 is provided on the support ring, and the connecting cross bar 43 freely passes through the notch and is installed on the output shaft 52 of the swing motor 51.

[0047] To facilitate driving the vacuum pipe 44 to rotate, the cross-section of the output shaft of the swing motor 51 is square, and the positioning hole is square and adapted to the output shaft.

[0048] The other end of the vacuum pipe 44 is bent upward and welded to the bottom of the adsorption disc 451, and the vacuum pipe communicates with the hollow cavity 452 of the adsorption disc upward, so that the adsorber 45 is installed on the swing device. The vacuum port of the Roots vacuum pump is communicated with the vacuum pipe 44 through the negative pressure pipe 42, so that the adsorption holes are communicated with the vacuum port of the vacuum device through the hollow cavity of the adsorption disc, the vacuum pipe and the negative pressure pipe in sequence.

[0049] Driven by the swing device, the adsorber swings between the working position and the parking position. Please refer to Figure 4 , Figure 4 In, the adsorber shown by the solid line is in the working position, and the adsorber shown by the dotted line is in the parking position.

[0050] The model 30 is bonded to the working surface 231 of the printing platform, and a demolding hole 31 is formed in the model. The upper end of the demolding hole 31 communicates with the air outlet, and the demolding hole penetrates at least one cured layer downward. For the detailed content of the demolding hole 31, please refer to the relevant content in Embodiment 2 below.

[0051] When the adsorber is in the working position, the adsorption hole is directly below the lower port of the demolding hole; when the adsorber is in the parking position, the adsorber is located outside the projection of the printing platform in the vertical direction, Figure 4 The area shown by the dotted line 1121 in is the projection range of the printing platform in the vertical direction.

[0052] When a cured layer penetrated by the demolding hole is completed, the adsorber can be in the working position and can adsorb the release film opposite to the lower port of the demolding hole. When the transmission mechanism drives the printing platform to move upward, the release film can be peeled off from the cured layer from the inside to the outside along the lower edge of the demolding hole.

[0053] To avoid the wear caused by the contact between the adsorber and the release film and affect the service life of the release film, there is a spacing of 0.1 - 0.5 mm between the upper surface of the adsorber and the lower surface of the release film. Specifically, in this embodiment, the spacing between the upper surface of the adsorber and the lower surface of the release film is 0.3 mm. It can be understood that in other embodiments, the spacing between the upper surface of the adsorber and the lower surface of the release film can also be 0.1 mm, 0.2 mm, 0.4 mm, or 0.5 mm, or other data between 0.1 - 0.5 mm. For clarity of display, in the drawings, the distance between the upper surface of the adsorber and the lower surface of the release film is magnified with an over - appropriate ratio.

[0054] Example 2

[0055] Please refer to Figures 6-8 , this embodiment describes the 3D printing method. This 3D printing method is carried out using the 3D printer in Example 1. This 3D printing method includes the following steps:

[0056] (1) After the 3D modeling of the model to be printed is completed, calculate a cylindrical hole - forming area with a set diameter. Please also refer to Figure 2 , in Figure 2 the model 30 shown, the model 30 is represented by a dotted line. The area enclosed by the double - dotted line 91 is the hole - forming area. For clarity of display, the double - dotted line 91 extends upward to the model plate 23 and downward below the model 30. Also for clarity of display, the model 30 is not provided with hatching. In this embodiment, the demolding hole is linear and the demolding hole extends in the vertical direction

[0057] The set diameter of the hole - forming area is 20 mm, the demolding hole is a circular hole, and the inner diameter of the demolding hole is 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 extending direction of the hole - forming area is perpendicular to this outer end face, and this outer end face can be used as the starting face during model printing. In this embodiment, the model to be printed is composed of 1000 solidification layers. The hole - forming area extends 990 solidification layers downward from the starting face, that is, N = 1000, M = 10, N - M = 990, N > M. The thickness of each solidification layer is 0.1 mm.

[0058] It can be understood that the inner diameter of the demolding hole can also be 5 mm, 7 mm, or 9 mm. When the set diameter of the hole - forming area is larger, the inner diameter of the demolding hole can also be 12 mm, 15 mm, or 20 mm. Of course, according to the different sizes of the hole - forming area, the inner diameter of the demolding hole can be flexibly selected between 5 - 20 mm.

[0059] (2) Starting from this outer end face, print the model to be printed. During the printing process of the cured layer of the model, demolding holes 31 are formed within the hole-forming area. The demolding holes 31 communicate upward with the air guide holes, and the demolding holes penetrate downward through the lower end face of the lowermost cured layer.

[0060] After printing each cured layer, start the swing device 50, move the adsorber from the parked position to the working position, start the vacuum device 41, adsorb the release film onto the adsorber, and then start the transmission mechanism to lift the printing platform upward, causing the release film to peel outward along the lower edge of the demolding hole. At the same time, the release film peels inward along the outer edge of the model until the cured layer is completely peeled from the release film. Then, turn off the vacuum device, and the release film detaches from the adsorber. Start the swing device again to move the adsorber from the working position to the parked position. Then lower the printing platform so that the distance between the model and the release film is the thickness of one cured layer, and continue to print the next cured layer.

[0061] Please refer to Figure 7 , 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 to be lifted upward, causing an outer peeling opening 902 to be generated between the outer edge of the cured layer and the release film. At the same time, since the release film below the demolding hole is fixed by the adsorber, the release film can also generate an inner peeling opening 901 between the lower edge of the demolding hole and the cured layer, causing the release film to peel outward along the edge of the demolding hole, enabling the release film to peel from the cured layer in both the inner and outer directions, forming an inner and outer two-way peeling method.

[0062] Please refer to Figure 8 , 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 communicate with each other, causing the release film to be completely peeled from the cured layer. When the cured layer is completely peeled from the release film, turn off the vacuum device, and the release film detaches from the adsorber. Start the swing device again to move the adsorber from the working position to the parked position.

[0063] Since the release film can be peeled in both the inner and outer directions, the peeling efficiency is improved, and the lifting height of the printing platform during the peeling of the release film can be reduced, thereby improving the printing efficiency.

[0064] Continue to print the cured layer until the printing of 990 cured layers is completed, that is, the printing of N - M cured layers is completed. As the printing progresses, the demolding holes extend with the extension of the model.

[0065] (3) Complete the printing of the last 10 cured layers, that is, complete the printing of the last M cured layers.

[0066] To maintain the integrity of the model's appearance, the M curing layers located at the lowermost side jointly form a closed layer 32, which closes the lower end of the demolding hole to maintain the integrity of the model's appearance. In this embodiment, the closed layer is jointly constituted by the 10 lowermost curing layers, that is, the closed layer is jointly constituted by M curing layers. For details, please refer to Figure 2 , in this embodiment, the thickness H of the closed layer is 1 mm. It can be understood that according to different requirements, the thickness of the closed layer can also be 2 mm, 3 mm, 4 mm or 5 mm, or other thicknesses between 1 - 5 mm.

[0067] When printing the last 10 curing layers, the release film is still peeled off from the curing layer in the traditional way, and the release film is peeled off from the curing layer only by raising the printing platform.

[0068] After completing the printing of the model, after removing the model from the printing platform, the photosensitive resin remaining in the air vent holes is poured out from the orifice located at the starting surface, and the air vent holes are cleaned.

Claims

1. A 3D printer with a center-pull-down peeling function, characterized in that: The invention comprises a workbench and a central peeling mechanism, a transmission mechanism is installed on the workbench, the transmission mechanism has a ball screw extending in a vertical direction and a connecting arm meshed on the ball screw, the free end of the connecting arm forms a working end, a printing platform is detachably installed 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, the air guide hole runs 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; The central peeling mechanism includes a vacuum device, an absorber and a swing device, wherein the vacuum device is fixedly installed in the inner cavity of the workbench, the absorber has an absorption hole, and the absorption hole is connected to the vacuum port of the vacuum device, the swing device is installed on the workbench, and the absorber is installed on the swing device, and the swing device can drive the absorber to swing between the working position and the parking position; A material trough is arranged on the workbench, and the printing platform can enter the material trough and print the model on its working surface; 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; when the absorber is located at the working position, the absorber is located directly below the lower end of the demolding hole; when the absorber is located at the parking position, the absorber is located outside the projection of the printing platform in the vertical direction; After completing a solidified layer through which a demolding hole passes, the absorbent can be located in the working position and can absorb the release film directly opposite to the lower end of the demolding hole, and when the transmission mechanism drives the printing platform to move upward, the release film can be peeled off from the solidified layer from the inside to the outside along the lower end edge of the demolding hole.

2. The 3D printer according to claim 1, characterized in that: The distance between the upper surface of the adsorber and the lower surface of the release film is 0.1-0.5 mm.

3. The 3D printer according to claim 2, characterized in that: One 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 groove is respectively provided on two 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 groove. Each clamping arm is fixed to the printing platform by bolts.

4. The 3D printer according to claim 1, characterized in that: The swing device comprises a swing motor which is a servo motor fixed in the inner cavity of the workbench, the output shaft of the swing motor extends upward out of the top plate of the workbench, and the air inlet pipe of the adsorber is fixed on the output shaft of the swing motor.

5. The 3D printer according to claim 1, characterized in that: The adsorber includes a circular adsorption disk with a hollow cavity inside. The center of the upper surface of the adsorption disk is recessed downward to form an adsorption cavity with an arc-shaped bottom surface. The adsorption hole connects the hollow cavity and the adsorption cavity.

6. A 3D printing method, characterized in that: The 3D printing method is performed using the 3D printer according to any one of claims 1 to 5, 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 at least extend to an 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; (2) Printing the model to be printed with the outer end surface as the starting surface, and forming a demolding hole in the hole forming area during the printing process of the solidified layer of the model, wherein the demolding hole is connected to the air guide hole upward; and the demolding hole penetrates downward through the lower end surface of the solidified layer located at the lowermost side; After each solidified layer is printed, the swing device is started to move the absorber from the parking position to the working position, the vacuum device is started to absorb the release film onto the absorber, and then the transmission mechanism is started to lift the printing platform upward, so that the release film is peeled off outward along the lower edge of the demolding hole, and at the same time, the release film is peeled off inward along the outer edge of the model until the solidified layer and the release film are completely peeled off, the vacuum device is turned off, the release film is separated from the absorber, and the swing device is started again to move the absorber from the working position to the parking position; Continue printing the solidified layer until NM solidified layers are printed; (3) Complete the printing of the last M solidified layers.

7. The 3D printing method according to claim 6, characterized in that: The demoulding hole is linear and extends in the vertical direction.

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

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

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

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