A three-dimensional printer and a three-dimensional printing method with inside-out stripping of a release film

Abstract

The application discloses a three-dimensional printer with an inside-out stripping type release film, which comprises a workbench, a material pump, a transmission mechanism installed on the workbench, a printing platform installed on the transmission mechanism, a liquid guide hole formed on the printing platform, a release film of a material tank, which divides the material tank into a gas chamber and a material chamber, gas filled in the gas chamber, photosensitive resin contained in the material chamber, and the material pump used for guiding the photosensitive resin in the material chamber into a demolding hole of a model through the liquid guide hole, so that the release film and the model form an inside-out stripping type release mode by adjusting the pressure of the gas chamber. The application further discloses a three-dimensional printing method. The photosensitive resin in the material tank is injected into the demolding hole of the model by the material pump, so that the release film is separated from the model from two directions of inside and outside of the model, and the release speed and the printing speed of the release film are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to a pull-up type light-cured 3D, in particular to a three-dimensional printer and three-dimensional printing method with inner and outer stripping of release film. BACKGROUND

[0002] The pull-up type light-cured three-dimensional printer is rapidly promoted due to its small size and low price, especially the desktop three-dimensional printer, which is a necessary device for three-dimensional printing research. The three-dimensional printing product is formed by a plurality of stacked cured layers. A release film is needed to reduce the adhesion between the cured layer and the bottom of the tank, so that each cured layer can be smoothly stripped from the bottom of the tank and lifted one printing height upward, so that the printing can continue.

[0003] When the printing of a cured layer is completed, the cured layer will be attached to the bottom surface of the printing platform and the surface of the release film. When the printing platform is lifted upward, the cured layer needs to be lifted upward to complete the stripping of the release film, and the uncured photosensitive resin needs to be filled between the cured layer and the release film. However, a sealed area is formed between the release film and the cured layer, which makes it difficult to strip the cured layer and the release film.

[0004] Therefore, in order to facilitate the stripping of the cured layer and the release film, an inclined stripping method is generated. The inclined stripping method is to incline the tank when lifting the printing platform, so that a stripping gap is generated on one side of the cured layer. With the gradual expansion of the stripping gap, the release film and the cured layer are completely stripped.

[0005] Although the inclined stripping method can accelerate the stripping of the cured layer and the release film, the photosensitive resin is easy to overflow the tank in the inclined state. In order to avoid the overflow of the photosensitive resin, the depth of the tank needs to be increased or the liquid capacity of the tank needs to be reduced. At the same time, due to the inclination, the photosensitive resin will shake greatly, which will expand the contact area between the photosensitive resin and the air, and easily mix the air into the photosensitive resin, affecting the printing quality of the product model.

[0006] Therefore, how to accelerate the stripping of the cured layer and the release film to improve the printing efficiency is still a problem that needs to be improved in the light-cured three-dimensional printing technology. SUMMARY

[0007] In order to improve the peeling speed of the solidified layer and the release film during the printing of the model, and improve the printing efficiency, the application discloses a three-dimensional printer with inner and outer peeling release film, which comprises a workbench and a material pump, 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 is formed as a working end, a printing platform is detachably installed on the working end, the lower surface of the printing platform is formed as a working surface, and the connecting arm can drive the printing platform to reciprocate in the vertical direction; a liquid guide hole is formed in the printing platform, the liquid guide hole penetrates through the upper and lower sides of the printing platform, the upper end of the liquid guide hole is formed as a liquid inlet, and the lower end of the liquid guide hole is formed as a liquid outlet.

[0008] A trough is fixedly installed on the workbench, the trough comprises a groove wall and a light-transmitting plate sealingly installed at the bottom of the groove wall, a release film is installed in the trough, the release film is located at the middle part of the trough in the up-down direction, the release film divides the inner cavity of the trough into a gas chamber and a material chamber in the up-down direction, the material chamber is located above the gas chamber, the gas chamber is filled with gas, the material chamber contains photosensitive resin, and an exhaust pipe and an air inlet pipe communicating with the gas chamber are installed on the groove wall; an air charging device is connected to the air inlet pipe, and an air inlet valve is installed on the air inlet pipe; an air outlet valve is installed on the exhaust pipe.

[0009] The air charging device is used for charging gas into the gas chamber, and the exhaust pipe is used for discharging the gas in the gas chamber; the gas in the gas chamber is discharged through the exhaust pipe to reduce the supporting force of the gas in the gas chamber on the release film, so that the release film between the solidified layer and the groove wall protrudes downward, and the release film gradually peels off from the outside to the inside along the edge of the solidified layer; the air charging device can charge gas into the gas chamber to restore the release film to its original state.

[0010] The inlet of the material pump communicates with the material chamber of the trough, and the outlet of the material pump communicates with the liquid outlet; the model is bonded to the printing platform, a release hole is formed in the model, the upper end of the release hole communicates with the liquid outlet, and the release hole penetrates at least one solidified layer downward; after completing the solidified layer penetrated by one release hole, the photosensitive resin in the trough can be sent into the liquid guide hole under the driving of the material pump, so that the release film gradually peels off from the inside to the outside of the solidified layer. Preferably, the liquid guide hole extends in the vertical direction.

[0011] In the model printing process, after the printing of a solidified layer is completed, the photosensitive resin in the tank is injected into the liquid guide hole through the material pump, and then into the demolding hole in the model. Under the push of the photosensitive resin in the demolding hole, the release film starts to peel off from the edge of the demolding hole, forming an inner peeling opening between the release film and the solidified layer. The photosensitive resin enters the inner peeling opening at the same time. As the photosensitive resin is continuously injected, the inner peeling opening continuously expands and expands outward. At the same time, the transmission mechanism lifts the model upward through the printing platform and reduces the pressure in the air chamber, so that the release film starts to peel off along the outer edge of the solidified layer at the same time, and an outer peeling opening is formed between the outer edge of the solidified layer and the release film. As the model is lifted, the outer peeling opening continuously expands and expands inward, forming an inner and outer peeling mode, 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. Because the release film can be peeled off from the inside and outside at the same time, the peeling speed of the release film is improved, so that the printing speed can be improved.

[0012] Specifically, 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 is formed as a working surface on which the model is bonded. The liquid guide hole includes an upper liquid hole arranged in the body and a lower liquid hole arranged in the model plate. A liquid guide pipe is inserted into the lower liquid hole from top to bottom through the upper liquid hole in a sealed manner. The outlet of the material pump is communicated with the liquid guide pipe. The upper end of the demolding hole is communicated with the lower liquid hole.

[0013] The liquid guide pipe can be conveniently connected to the outlet of the material pump through the pipeline. Preferably, the liquid guide pipe is screwed on the printing platform in a threaded manner.

[0014] Further, the lower liquid hole is a stepped hole. The large hole of the stepped hole faces upward. The lower end of the liquid guide pipe is sealingly pressed against the stepped surface of the stepped hole. The stepped hole is used to avoid the liquid guide pipe extending downward out of the liquid guide hole due to misoperation. When the liquid guide pipe extends downward out of the liquid guide hole, the distance between the printing platform and the release film is relatively small at the initial stage of printing, which is easy to cause the liquid guide pipe to press against the release film, causing damage to the release film or directly piercing the release film, resulting in waste of the release film.

[0015] Specifically, the end of the connecting arm away from the ball screw has two clamping arms arranged in a 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. A clamping groove is arranged on the opposite side of each clamping arm. 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.

[0016] In the design, the printing platform is installed on the connecting arm by the clamping arm, so that the top of the printing platform is left empty, and the outlet of the material pump can be communicated with the liquid guide hole through the pipeline.

[0017] Further, in order to facilitate the overall movement of the 3D printer, the material pump is fixedly installed in the inner cavity of the workbench.

[0018] Secondly, the application also discloses a three-dimensional printing method, which is performed by using the three-dimensional printer with the inner and outer stripping type release film.

[0019] (1) After the 3D modeling of the to-be-printed model is completed, a cylindrical hole forming area with a set diameter is calculated, the hole forming area can extend to at least one outer end face of the to-be-printed model, and the outer end face is taken as a starting face in model printing; the to-be-printed model is composed of N solidified layers, and the hole forming area extends downward by (N-M) solidified layers from the starting face, and N>M;

[0020] (2) The pressure on the upper and lower sides of the release film is made the same, so that the release film is horizontally arranged;

[0021] The to-be-printed model is printed with the outer end face as the starting face, and a release hole is formed in the hole forming area in the printing process of the solidified layer of the model, the release hole is communicated with the liquid guide hole upward, and the release hole penetrates the lower end face of the solidified layer located at the lowermost side downward;

[0022] After each solidified layer is printed, the following steps (2.1), (2.2) and (2.3) are synchronously performed:

[0023] (2.1) The printing platform is lifted upward;

[0024] (2.2) The material pump is started, the photosensitive resin in the trough is sent into the liquid guide hole and then into the release hole, the release film is stripped from inside to outside along the edge of the release hole until the solidified layer and the release film are completely stripped, and the photosensitive resin in the liquid guide hole returns to the trough;

[0025] (2.3) The pressure of the air chamber is reduced, the release film between the solidified layer and the groove wall protrudes downward, the release film is gradually stripped from outside to inside along the edge of the solidified layer, and the printing platform is synchronously lifted upward, so that the release film and the solidified layer are completely stripped;

[0026] After the release film and the solidified layer are stripped, the pressure of the air chamber is increased, the pressure on the upper and lower sides of the release film is made the same, and the horizontal arrangement of the release film is restored;

[0027] The solidified layer is continuously printed until the printing of (N-M) solidified layers is completed;

[0028] The material pump is temporarily stopped during the printing interval of the two adjacent solidified layers;

[0029] (3) printing of the last M solidified layers is completed.

[0030] When the three-dimensional product model is printed by the three-dimensional printing method in the present application, during the printing process of the first (N-M) solidified layers, after the printing of each solidified layer is completed, the light-sensitive resin in the tank is injected into the liquid guide hole by the material pump, and then into the demolding hole in the model. Under the pushing of the light-sensitive resin in the demolding hole, the release film starts to peel off from the edge of the demolding hole, forming an internal peeling gap between the release film and the solidified layer. As the light-sensitive resin continues to be injected, the internal peeling gap continues to expand and expand outward. At the same time, the transmission mechanism lifts the model upward through the printing platform and reduces the pressure in the air chamber, so that the release film starts to peel off along the outer edge of the solidified layer, and an external peeling gap is formed between the outer edge of the solidified layer and the release film. As the model is lifted, the external peeling gap continues to expand and expand inward, forming an internal and external peeling method, until the external peeling gap and the internal peeling gap are connected to each other, so that the release film and the solidified layer are completely peeled off. Because the release film can be peeled off from the inside and outside at the same time, the peeling speed of the release film is improved, so that the printing speed can be improved.

[0031] When the last M solidified layers are printed, different processing methods are adopted according to different needs. When the liquid guide hole penetrates downward through the solidified layer located at the lowermost side of the model, and does not affect the appearance and use function of the model, the internal and external peeling method can be continued to complete the peeling of the release film and the last M solidified layers. However, when the liquid guide hole penetrates downward through the solidified layer located at the lowermost side of the model, which will adversely affect the appearance or use function of the model, it is recommended to only use the method of lifting the printing platform combined with adjusting the pressure in the air chamber to complete the peeling of the release film and the last M solidified layers, that is, the liquid guide hole does not enter the last M solidified layers, and the last M solidified layers are used to complete the sealing of the liquid guide hole. After the printing of the model is completed, the model is removed from the printing platform, the light-sensitive resin remaining in the liquid guide hole is poured out from the hole at the starting surface, and the liquid guide hole is cleaned.

[0032] Specifically, the demolding hole is linear, and the angle between the demolding hole and the vertical direction is 0-20°. When the angle between the demolding hole and the vertical direction is 0°, the demolding hole extends along the vertical direction. During the specific printing process of the model, the inclination angle of the demolding hole can be set according to the shape of the model, but the angle between the demolding hole and the vertical direction tends to be 0°, so that the light-sensitive resin can flow downward along the demolding hole smoothly.

[0033] Further, to avoid cracks or breakage of the model due to the pressure of the photosensitive resin in the release hole, the set diameter of the hole forming area is ≥10 mm larger than the inner diameter of the release hole. This design makes the wall thickness of the release hole at least 5 mm, so that the area of the release hole has higher strength and can withstand the pressure of the photosensitive resin in the release hole during the stripping process of the release film.

[0034] Specifically, the inner diameter of the release hole is 5-20 mm. The inner diameter of the release hole should not be too small, and the inner diameter of the release hole is too small, which not only increases the resistance of the photosensitive resin, but also causes the photosensitive resin to solidify in the release hole, thereby blocking the release hole. The inner diameter of the release hole should not be too large, and the release hole is too large, which easily leads to insufficient strength of the model and affects the quality of the product.

[0035] Further, the total thickness of the M cured layers is 1-5 mm, and the release hole does not penetrate the M cured layers. A closed layer is formed by the M cured layers located at the lowermost side, which is used to close the lower end of the release hole to ensure the integrity of the appearance of the model. When printing the last M cured layers, the stripping of the release film and the cured layer is only dependent on the lifting of the printing platform and the adjustment of the air chamber pressure to complete the stripping of the release film and the cured layer. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 is a structural schematic diagram of an embodiment of a three-dimensional printer in the present application.

[0037] Figure 2 is a structural schematic diagram of a three-dimensional printer in the present application. Figure 1 is a view of A-A in

[0038] Figure 3 is a structural schematic diagram of a connecting arm.

[0039] Figure 4 is a structural schematic diagram of a trough.

[0040] Figure 5 is an enlarged view of part B in Figure 4

[0041] Figure 6 is a state diagram of a three-dimensional printer when working.

[0042] Figure 7 is a state diagram of the release film and the cured layer when the partial stripping is completed.

[0043] Figure 8 is a state diagram of the release film and the cured layer when the complete stripping is completed.

[0044] Figure 9 is an attached diagram of the release film when it returns to the printing working state. DETAILED DESCRIPTION

[0045] Embodiment 1​

[0046] Referring to Figures 1-3 A three-dimensional printer with a release film inside-out stripping method comprises a workbench 11 and a material pump 18, the workbench 11 is provided with a transmission mechanism, the transmission mechanism adopts existing mature technology. The transmission mechanism comprises a vertical rod 12 fixed on the workbench 11 and a ball screw 13 rotatably installed on one side of the vertical rod 12, the ball screw 13 extends in the vertical direction, and one end of a connecting arm 14 is engaged with the ball screw through a screw 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, and the servo motor is fixedly installed on the vertical rod. The servo motor can drive the ball screw to rotate, so that the connecting arm can drive the printing platform to move up and down.

[0047] A liquid crystal 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 screen 191. A tank 40 is fixedly installed on the top plate of the workbench and located above the liquid crystal screen. The irradiation unit provides a forming light beam for curing the photosensitive resin in the tank 40. 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.

[0048] The specific structure of the tank 40 is described below. Referring to Figure 4 and Figure 5 The tank 40 specifically comprises a tank wall 41 and a light-transmitting plate 43 sealingly installed at the bottom of the tank wall 41. The light-transmitting plate is a glass plate. It can be understood that in other embodiments, the light-transmitting plate can also be a plastic plate or an acrylic plate or other plates that can provide sufficient supporting force. A tank flange 46 is connected to the outside of the bottom of the tank wall 41. A bolt 175 passes through the tank flange 46 to fix the tank on the top plate 111 of the workbench, so that the tank is detachably fixed on the workbench. In the vertical direction, the tank 40 is located directly above the liquid crystal screen 191.

[0049] A release film 44 is installed in the tank 40. The release film is a flexible thin film made of soft material. In this embodiment, the release film is specifically a polytetrafluoroethylene release film. The release film is located at the middle part of the tank in the up-down direction. The release film 44 divides the inner cavity of the tank 40 into an air chamber 402 and a material chamber 401 in the up-down direction. The material chamber 401 is located on the upper side of the release film, and the air chamber 402 is located on the lower side of the release film, i.e. the material chamber 401 is located on the upper side of the air chamber 402. The material chamber contains photosensitive resin.

[0050] In order to facilitate the installation of the release film 44, in the embodiment, a first step surface 411 facing upward is arranged on the inner circumferential surface of the groove wall 41, the first step surface 411 is formed by the inner circumferential surface of the groove wall being recessed outward in the horizontal direction, the first step surface is provided with an annular groove 412, a first screw 413 is screwed in the groove wall after penetrating an annular metal gasket 414 and the release film, the annular metal gasket 414 is located on the upper side of the release film, and the annular metal gasket faces the annular groove 412, the annular cylinder 42 is lined in the groove wall and is pressed against the first step surface 411, and a sealing ring 415 is arranged between the annular cylinder and the first step surface, a second screw 416 is screwed in the groove wall after penetrating the annular cylinder in the horizontal direction from inside to outside, so as to fix the annular cylinder on the groove wall, and only one second screw is shown in the drawing by way of example. When the gas chamber and the material chamber are both communicated with the atmosphere, the pressures on the upper and lower sides of the release film are the same, and the release film is in a flat state extending in the horizontal direction.

[0051] The gas chamber is filled with gas, and in the embodiment, air is directly used. In the application, the gas in the gas chamber has no special requirements, and colorless and transparent light can meet the requirements. It can be understood that in other embodiments, inert gases such as nitrogen can also be used. The material chamber is used to contain photosensitive resin. The printing platform can extend into the material chamber and form a solidified layer on the printing platform.

[0052] The exhaust pipe 56 and the air inlet pipe 51 communicating with the gas chamber 402 are arranged on the groove wall, the exhaust pipe 56 and the air inlet pipe 51 are connected to a total gas pipe 50, the total gas pipe 50 is fixed on the groove wall and communicates with the gas chamber 402. The air charging device 52 is connected to the air inlet pipe, and the air inlet valve 53 is arranged on the air inlet pipe and located on the side facing the material groove. In the embodiment, the air charging device is a high-pressure gas tank, which contains compressed air. It can be understood that in other embodiments, devices such as air compressors and high-pressure fans can also be used as the air charging device 52. The exhaust valve 57 is arranged on the exhaust pipe 56.

[0053] The air charging device is used to charge gas into the gas chamber, and the exhaust pipe is used to exhaust the gas in the gas chamber; the gas in the gas chamber is exhausted through the exhaust pipe to reduce the supporting force of the gas in the gas chamber on the release film, so that the release film between the solidified layer and the groove wall protrudes downward, and the release film gradually peels off from the outside to the inside along the edge of the solidified layer; the air charging device can charge gas into the gas chamber to restore the release film to its original state.

[0054] In order to monitor the pressure difference between the upper and lower sides of the release film, a differential pressure gauge 60 is installed on the outside of the tank, and two detection ends of the differential pressure gauge 60 are respectively referred to as a first detection end 61 and a second detection end 62, wherein the first detection end 61 is located at the bottom of the bin, and the second detection end 62 is located in the air bin. The differential pressure gauge is used to detect the pressure on the upper and lower sides of the release film, so as to quickly restore the release film to its original state.

[0055] A short pipe 172 is installed on the tank wall corresponding to the bin 401, which penetrates the tank wall in the radial direction and communicates with the bin 401.

[0056] In the embodiment, the printing platform 20 comprises 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 mounted on the platform flange 22 by bolts. The lower surface of the model plate 23 forms a working surface 231.

[0057] In the embodiment, the connecting arm 14 has two clamping arms 141 spaced apart in the horizontal direction at the end away from the ball screw. The two clamping arms 141 extend away from the ball screw and are parallel to each other, and a platform accommodating cavity 142 is formed between the two clamping arms, which has an opening away from the ball screw. Corresponding to each clamping arm 141, a clamping groove 25 is arranged on the opposite sides of the body. The printing platform 20 is inserted into the platform accommodating cavity 142, and each clamping arm 141 is inserted into the corresponding clamping groove 25. The first bolt 16 is screwed into the first screw hole 251 in the clamping groove after penetrating the clamping arm, so as to detachably fix the clamping arm on the printing platform. To avoid shaking, each clamping arm is fixed on the printing platform by two first bolts.

[0058] A liquid guide hole is formed in the printing platform. In the embodiment, the liquid guide hole comprises an upper liquid hole 211 arranged in the body and a lower liquid hole 232 arranged in the model plate. The upper liquid hole 211 and the lower liquid hole 232 are coaxially arranged and extend in the vertical direction. The upper liquid hole 211 and the lower liquid hole 232 are in communication with each other, and the upper liquid hole 211 penetrates the upper end surface of the body upward, and the lower liquid hole 232 penetrates the lower end surface of the model plate downward. That is, the upper liquid hole 211 and the lower liquid hole 232 jointly constitute the liquid guide hole, and the liquid guide hole penetrates the upper and lower sides of the printing platform. The upper end of the liquid guide hole forms a liquid inlet, and the lower end of the liquid guide hole forms a liquid outlet.

[0059] Since the upper liquid hole 211 and the lower liquid hole 232 are coaxially arranged and extend in the vertical direction, the liquid guide hole extends in the vertical direction.

[0060] For the convenience of connection, a liquid guide pipe 26 is installed on the printing platform, which is a stainless steel pipe and is inserted into the lower liquid hole from the upper liquid hole in a sealing manner. The material pump 18 is located in the inner cavity 112 of the workbench 11 and is fixed on the bottom plate 113. The inlet of the material pump 18 is connected to the short pipe 172 through the liquid inlet pipe 181, and the outlet of the material pump 18 is connected to the liquid guide pipe 26 through the liquid outlet pipe 182. In order to facilitate the up-down movement of the printing platform, the liquid outlet pipe is a plastic hose. Specifically, in the embodiment, the upper liquid hole is a threaded hole, and the liquid guide pipe is screwed into the upper liquid hole.

[0061] In order to avoid the liquid guide pipe extending downwardly out of the liquid guide hole, in the embodiment, the lower liquid hole is a stepped hole, the large hole of the stepped hole faces upwardly, so that the stepped hole has a second stepped surface facing upwardly, and the lower end of the liquid guide pipe is sealingly pressed against the second stepped surface of the stepped hole. In order to ensure the sealing, a rubber sealing ring is arranged between the second stepped surface and the liquid guide pipe to reduce or avoid the photosensitive resin in the liquid guide hole entering the gap between the body and the model plate.

[0062] The model 30 is bonded to the working surface 231 of the printing platform, and a release hole 31 is formed in the model, the upper end of the release hole 31 is connected to the liquid outlet, and the release hole penetrates part of the cured layer downwardly. When the cured layer penetrated by one release hole is completed, the photosensitive resin in the trough can be sent into the liquid guide hole under the driving of the material pump, so that the release film is gradually peeled off from the inside to the outside of the cured layer.

[0063] For details of the release hole 31, please refer to the related content in Embodiment 2 below.

[0064] Embodiment 2

[0065] Please refer to Figures 6-9 , the embodiment describes a three-dimensional printing method, which is carried out by using the three-dimensional printer of the inside-outside peeling type release film in Embodiment 1, and the three-dimensional printing method comprises the following steps:

[0066] (1) After the 3D modeling of the model to be printed is completed, a cylindrical hole-forming area with a set diameter is calculated, please refer to Figure 2 , and Figure 2 , the model 30 is represented by a dashed line, and the area enclosed by the double-dot chain line 91 is the hole-forming area. In order to show clearly, the double-dot chain line 91 extends upwardly to the model plate 23, and the double-dot chain line 91 extends downwardly to the lower side of the model 30. Similarly, in order to show clearly, the model 30 is not provided with a section line.

[0067] In this embodiment, the membrane stripping hole is linear, and the membrane stripping hole extends in the vertical direction, that is, the included angle between the membrane stripping hole and the vertical direction is 0°. It can be understood that in other embodiments, the membrane stripping hole can also be inclined, and the included angle between the membrane stripping hole and the vertical direction can be 1°, 5°, 8°, 12°, 16° or 20°, and of course it can also be other angles between 1-20°.

[0068] The set diameter of the pore-forming area is 20 mm, the membrane stripping hole is a circular hole, and the inner diameter of the membrane stripping hole is 10 mm, so that the set diameter of the pore-forming area is 10 mm larger than the inner diameter of the membrane stripping hole. The pore-forming area extends to one outer end surface 35 of the to-be-printed model, the extension direction of the pore-forming area is perpendicular to the outer end surface, and the outer end surface can be used as a starting surface during model printing. In this embodiment, the to-be-printed model is composed of 1000 solidified layers, and the pore-forming area extends downward by 990 solidified layers from the starting surface, that is, N=1000, M=10, (N-M)=990, and N>M. The thickness of each solidified layer is 0.1 mm.

[0069] It can be understood that the inner diameter of the membrane stripping hole can also be 5 mm, 7 mm or 9 mm, and when the set diameter of the pore-forming area is larger, the inner diameter of the membrane stripping hole can also be 12 mm, 15 mm or 20 mm. Of course, according to the different sizes of the pore-forming area, the inner diameter of the membrane stripping hole can be flexibly selected between 5-20 mm.

[0070] (2) Close the exhaust valve 57 and open the air inlet valve 53, fill gas into the air chamber through the gas filling device, so that the pressure on the upper and lower sides of the release film is the same, the release film is horizontally arranged, and the air inlet valve 53 is closed.

[0071] The to-be-printed model is printed with the outer end surface as the starting surface, and the membrane stripping hole 31 is formed in the pore-forming area during the printing process of the solidified layer of the model. The membrane stripping hole 31 is connected to the liquid guide hole upward, and the membrane stripping hole penetrates the lower end surface of the lowermost solidified layer downward.

[0072] Please refer to Figure 7 After each solidified layer is printed, the following steps (2.1), step (2.2) and step (2.3) are simultaneously performed:

[0073] (2.1) The printing platform is lifted upward;

[0074] (2.2) Start the material pump 18 to send the photosensitive resin in the trough into the liquid guide hole, and then into the membrane stripping hole 31, push the release film downward, and make the release film peel off from the inside to the outside along the edge of the membrane stripping hole, so as to generate an internal peeling hole 901 between the release film and the solidified layer, until the solidified layer and the release film are completely peeled off, and the photosensitive resin in the liquid guide hole returns to the trough.

[0075] (2.3) Open the exhaust valve 57, and exhaust the gas in the gas chamber to the outside, so as to reduce the pressure in the gas chamber. Under the pressure of the photosensitive resin, the release film between the solidified layer and the groove wall protrudes downward. At the same time, due to the upward lifting of the printing platform, the release film gradually peels off along the edge of the solidified layer from outside to inside, so as to form an outer peeling port 902 between the outer side edge of the solidified layer and the release film.

[0076] Please refer to Figure 8 As the inner peeling port 901 and the outer peeling port 902 continuously extend and expand, the inner peeling port 901 and the outer peeling port 902 are connected with each other, so as to completely peel off the release film from the solidified layer.

[0077] Due to the fact that the release film can be peeled off from the inside and the outside, the peeling efficiency is improved, and the lifting height of the printing platform during the peeling of the release film can be reduced, so as to improve the printing efficiency.

[0078] Continue to print the solidified layer until the printing of 990 solidified layers is completed, that is, the printing of (N-M) solidified layers is completed. As the printing proceeds, the release hole extends along with the extension of the model.

[0079] During the printing interval time of the adjacent two solidified layers, the material pump is temporarily stopped.

[0080] Please refer to Figure 9 When the peeling of the release film from the solidified layer is completed, the exhaust valve 57 is closed, and the inlet valve 53 is opened, so that the compressed air in the high-pressure gas tank enters the gas chamber, the pressure in the gas chamber is increased, the pressure difference meter 60 is observed, the pressure on the upper and lower sides of the release film is made the same, the horizontal arrangement of the release film is restored, and then the inlet valve 53 is closed.

[0081] (3) Complete the printing of the last 10 solidified layers, that is, complete the printing of the last M solidified layers.

[0082] In order to maintain the integrity of the appearance of the model, the M solidified layers located at the lowermost side jointly form a closed layer 32, which closes the lower end of the release hole to maintain the integrity of the appearance of the model. In the embodiment, the closed layer is jointly constituted by the 10 solidified layers at the lowermost side, that is, the closed layer is jointly constituted by the M solidified layers. Please refer to Figure 2 In the 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.

[0083] During the printing of the last 10 solidified layers, only the pressure of the gas chamber is adjusted to speed up the peeling process, and the photosensitive resin is no longer injected into the release hole to speed up the peeling process.

[0084] After the printing of the model is completed, the model is removed from the printing platform, the photoresin remaining in the liquid guide hole is poured out from the orifice located at the starting surface, and the liquid guide hole is cleaned.

Claims

1. A three-dimensional printer with release film peeling mechanism, characterized in that, The device includes a worktable and a material pump. A transmission mechanism is mounted on the worktable. The transmission mechanism has a ball screw extending vertically and a connecting arm meshing with the ball screw. The free end of the connecting arm forms a working end. A printing platform is detachably mounted on the working end. The lower surface of the printing platform forms a working surface. The connecting arm can drive the printing platform to reciprocate vertically. A liquid guide hole is opened on the printing platform, which extends through the upper and lower sides of the printing platform. The upper end of the liquid guide hole forms a liquid inlet, and the lower end forms a liquid outlet. The material tank is fixedly installed on the workbench. The material tank includes a tank wall and a light-transmitting plate that is sealed at the bottom of the tank wall. A release film is installed inside the material tank. The release film is located in the middle of the material tank in the vertical direction. The release film divides the inner cavity of the material tank into an air chamber and a material chamber in the vertical direction. The material chamber is located above the air chamber. The air chamber is filled with gas. The material chamber contains photosensitive resin. An exhaust pipe and an air inlet pipe that connect to the air chamber are installed on the tank wall. An inflation device is connected to the air inlet pipe and an air inlet valve is installed on the air inlet pipe. An exhaust valve is installed on the exhaust pipe. The inflation device is used to fill the air chamber with gas, and the exhaust pipe is used to expel the gas from the air chamber. Expelling the gas from the air chamber through the exhaust pipe reduces the supporting force of the gas on the release film, allowing the release film between the cured layer and the tank wall to protrude downwards and gradually peel off the release film from the outside to the inside along the edge of the cured layer. The inflation device can fill the air chamber with gas to restore the release film to its original shape. The inlet of the material pump is connected to the hopper of the material tank, and the outlet of the material pump is connected to the liquid inlet; The model is bonded to the printing platform, and a release hole is formed inside the model. The upper end of the release hole is connected to the liquid outlet, and the release hole penetrates at least one cured layer downwards. After a curing layer with a release hole is completed, the photosensitive resin in the material tank can be sent into the liquid guiding hole under the drive of the material pump, so that the release film is gradually peeled off from the curing layer from the inside to the outside.

2. The three-dimensional printer 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 liquid guiding hole includes an upper liquid hole disposed in the main body and a lower liquid hole disposed in the model plate. A liquid guiding tube is inserted into the lower liquid hole from top to bottom through the upper liquid hole in a sealed manner. The outlet of the material pump is connected to the liquid guiding tube, and the upper end of the demolding hole is connected to the lower liquid hole.

3. The three-dimensional printer according to claim 2, characterized in that, The liquid outlet is a stepped hole, with the larger opening facing upwards, and the lower end of the liquid guide tube is sealed against the stepped surface of the stepped hole.

4. The three-dimensional printer according to claim 1, characterized in that, The connecting arm has two horizontally spaced retaining arms at the end away from the ball screw. The two retaining arms 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.

5. The three-dimensional printer according to claim 1, characterized in that, The material pump is fixedly installed inside the workbench.

6. A three-dimensional printing method, characterized in that, The 3D printing method, employing a release film peel-off type 3D printer as described in any one of claims 1-5, comprises 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 cured layers, and the hole-forming area extends downward from the starting surface by (NM) cured layers, where N>M; (2) Make the pressure on the upper and lower sides of the release film the same so that the release film is set horizontally; The model to be printed is printed with the outer end face as the starting face. During the printing process of the curing layer of the model, a release hole is formed in the hole-forming area. The release hole is connected to the liquid guiding hole upwards and penetrates the lower end face of the curing layer located at the bottom. After each cured layer is printed, perform the following steps simultaneously: (2.1), (2.2), and (2.3): (2.1) Raise the printing platform upwards; (2.2) Start the material pump to send the photosensitive resin in the material tank into the liquid guiding hole, and then into the demolding hole, so that the release film peels off from the inside to the outside along the edge of the demolding hole until the cured layer is completely peeled off from the release film, and the photosensitive resin in the liquid guiding hole returns to the material tank. (2.3) Reduce the pressure of the air chamber, and the release film between the curing layer and the tank wall protrudes downward, so that the release film is gradually peeled off from the outside to the inside along the edge of the curing layer; at the same time, lift the printing platform upward to completely peel the release film off from the curing layer. After the release film and the curing layer are peeled off, the pressure of the air chamber is increased to make the pressure on the upper and lower sides of the release film the same, and the release film is restored to a horizontal setting. Continue printing the cured layers until (NM) cured layers have been printed; The material pump stops working during the printing interval between two adjacent cured layers; (3) Complete the printing of the last M curing layers.

7. The three-dimensional 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 three-dimensional 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 three-dimensional printing method according to claim 6, characterized in that, The inner diameter of the stripping hole is 5-20mm.

10. The three-dimensional 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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