Release film inside and outside stripping type three-dimensional printer and three-dimensional printing method

Abstract

The invention discloses a release film inside and outside stripping type three-dimensional printer which comprises a workbench and a material pump, a transmission mechanism is installed on the workbench, a printing platform is installed on the transmission mechanism, a liquid guide hole is formed in the printing platform, a release film of a material groove divides the material groove into an air bin and a material bin, the air bin is filled with air, and the material bin is filled with material. Photosensitive resin is contained in the stock bin, the material pump is used for introducing the photosensitive resin in the stock bin into the demolding hole of the model through the liquid guide hole, and the release film and the model form an internal and external bidirectional stripping mode in combination with the adjustment of the pressure of the gas bin. The invention further discloses a three-dimensional printing method. The photosensitive resin in the trough is injected into the demolding hole of the model through the material pump, so that the release film is separated from the model from the inner direction and the outer direction of the model, and the stripping speed and the printing speed of the release film are increased.

Description

Technical Field

[0001] The invention relates to a top-pull light-curing 3D printer, and in particular to a 3D printer with a release film peeling inside and outside and a 3D printing method. Background Art

[0002] The top-down light-curing 3D printer has been rapidly promoted due to its small size and low price, especially the desktop 3D printer, which is an essential equipment for 3D printing research. The 3D printed product is formed by multiple stacked solidified layers. A release film is required to reduce the adhesion between the solidified layer and the bottom of the trough, so that each solidified layer can be smoothly peeled off from the bottom of the trough and raised to a printing height so that printing can continue.

[0003] After the printing of a solidified layer is completed, the solidified layer will adhere to the bottom surface of the printing platform and the surface of the release film at the same time. When the printing platform is lifted upward, the solidified layer needs to be lifted upward first to complete the peeling off from the release film, and then the uncured photosensitive resin is filled into the space between the solidified layer and the release film. However, since a sealing area is formed between the release film and the solidified layer, it is necessary to overcome the low pressure area generated between the release film and the solidified layer during the peeling process of the solidified layer and the release film, making it difficult for the solidified layer and the release film to be peeled off.

[0004] Therefore, in order to facilitate the peeling between the solidified layer and the release film, an inclined peeling method was created. The inclined peeling method is to tilt the material trough while lifting the printing platform upward, so that a peeling gap is generated on one side of the solidified layer of the release film. As the peeling gap gradually expands, the release film and the solidified layer are eventually completely peeled off.

[0005] Although the inclined peeling method can speed up the peeling of the solidified layer and the release film, the photosensitive resin is easy to overflow from the material tank in the inclined state. To avoid the overflow of the photosensitive resin, it is necessary to increase the depth of the material tank or reduce the liquid volume of the material tank. 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, making it easy for air to mix into the photosensitive resin, affecting the printing quality of the product model.

[0006] Therefore, how to speed up the peeling of the solidified layer and the release film to improve printing efficiency is still a problem that needs to be further improved in the light-curing 3D printing technology. Summary of the invention

[0007] In order to increase the peeling speed of the solidified layer and the release film during model printing and improve the printing efficiency, the present application first discloses a release film inner and outer peeling type 3D printer, which includes a workbench and a material pump. A transmission mechanism is installed on the workbench, and the transmission mechanism has a ball screw extending in a 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 liquid guide hole is provided on the printing platform, and the liquid guide hole runs through the upper and lower sides of the printing platform, and 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;

[0008] The material trough is fixedly installed on the workbench, and the material trough includes a trough wall and a light-transmitting plate sealedly installed at the bottom of the trough wall. A release film is installed in the material trough, and the release film is located in the middle part of the material trough in the up-down direction. The release film divides the inner cavity of the material trough into an air bin and a material bin in the up-down direction. The material bin is located on the upper side of the air bin, and is filled with gas. The material bin contains photosensitive resin. An exhaust pipe and an air inlet pipe connected to the air bin are installed on the trough wall, and an air charging device is connected to the air inlet pipe, and an air inlet valve is installed on the air inlet pipe, and an exhaust valve is installed on the exhaust pipe;

[0009] The gas charging device is used to charge gas into the gas chamber, and the exhaust pipe is used to discharge 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 can protrude downward, and the release film can be gradually peeled off from the outside to the outside along the edge of the solidified layer; the gas 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 is connected to the material bin 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 demolding hole is formed in the model, the upper end of which is connected to the liquid outlet, and the demolding hole penetrates at least one solidified layer downward; after a solidified layer penetrated by the demolding hole is completed, the photosensitive resin in the material tank can be fed into the liquid guide hole under the drive of the material pump, so that the release film is gradually peeled off from the solidified layer from the inside to the outside. Preferably, the liquid guide hole extends in the vertical direction.

[0011] During the model printing process, after the printing of a solidified layer is completed, the photosensitive resin in the material tank is injected into the liquid guide hole through the material pump, and then enters the demolding hole in the model. Under the push of the photosensitive resin in the demolding hole, 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, and the photosensitive resin enters the inner peeling opening at the same time. As the photosensitive resin 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 and reduces the pressure in the air chamber, so that the release film begins to peel off synchronously along the outer edge of the solidified layer, and forms an outer peeling opening between the outer edge of the solidified layer and the release film. As the model is lifted, the outer peeling opening continues to expand and expand inward, forming an inner and outer 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 inner and outer directions at the same time, the peeling speed of the release film is improved, thereby improving the printing speed.

[0012] Specifically, the printing platform includes a main body and a model plate detachably mounted at 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 liquid guide hole includes an upper liquid hole arranged in the main body and a lower liquid hole arranged in the model plate, a liquid guide tube is sealedly inserted into the lower liquid hole from top to bottom through the upper liquid hole, the outlet of the material pump is connected to the liquid guide tube, and the upper end of the demolding hole is connected to the lower liquid hole.

[0013] The liquid conduit can be conveniently connected to the outlet of the material pump via a pipeline. Preferably, the liquid conduit is screwed onto the printing platform in a threaded manner.

[0014] Furthermore, the lower liquid hole is a stepped hole, the large hole of which faces upward, and the lower end of the liquid guide tube is sealed against the stepped surface of the stepped hole. The stepped hole is used to prevent the liquid guide tube from extending downward out of the liquid guide hole due to misoperation. When the liquid guide tube extends downward out of the liquid guide hole, in the initial stage of printing, the distance between the printing platform and the release film is relatively narrow, and the liquid guide tube is easily pressed against the release film, causing damage to the release film or directly puncturing the release film, resulting in waste of the release film.

[0015] 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 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.

[0016] 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 to allow the outlet of the material pump to be connected to the liquid guide hole through a pipeline.

[0017] Furthermore, 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 present application also discloses a three-dimensional printing method, which is performed by using any of the above-mentioned three-dimensional printers with inner and outer peeling of the release film, and the three-dimensional printing method comprises the following steps:

[0019] (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;

[0020] (2) Make the pressure on the upper and lower sides of the release film the same so that the release film is placed horizontally;

[0021] 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 is formed in the hole forming area. The demolding hole is connected to the liquid guide hole upward. The demolding hole penetrates downward through the lower end surface of the solidified layer located at the lowermost side.

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

[0023] (2.1) Lift the printing platform upwards;

[0024] (2.2) Start the material pump to feed the photosensitive resin in the material tank into the liquid guide hole and then into the demolding hole, so that the release film is peeled off from the inside to the outside along the edge of the demolding hole until the solidified layer and the release film are completely peeled off, and the photosensitive resin in the liquid guide hole returns to the material tank;

[0025] (2.3) Reduce the pressure in the air chamber, so that the release film between the solidified layer and the groove wall protrudes downward, and the release film is gradually peeled off from the outside to the outside along the edge of the solidified layer; simultaneously, lift the printing platform upward, so that the release film and the solidified layer are completely peeled off;

[0026] After the release film and the solidified 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;

[0027] Continue printing the solidified layer until NM solidified layers are printed;

[0028] During the printing interval between two adjacent curing layers, the material pump stops working;

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

[0030] When the three-dimensional printing method in the present application is used to print the model of a three-dimensional product, during the printing process of the first NM solidified layers, after each solidified layer is printed, the photosensitive resin in the material tank is injected into the liquid guide hole through the material pump, and then enters the demolding hole in the model. Under the push of the photosensitive resin in the demolding hole, the release film begins to peel off from the edge of the demolding hole, and an inner peeling opening is formed between the release film and the solidified layer. As the photosensitive resin 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 and reduces the pressure in the air chamber, so that the release film begins to peel off synchronously along the outer edge of the solidified layer, 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 continues to expand and expand inward, forming an inner and outer 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 inner and outer directions at the same time, the peeling speed of the release film is improved, thereby improving the printing speed.

[0031] When printing the last M solidified layers, different processing methods are used according to different needs. When the liquid guide hole penetrates downward through the solidified layer located at the bottom of the model, it does not affect the appearance and use function of the model, and the internal and external bidirectional peeling method can continue to be used 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 bottom of the model, it will have an adverse effect on the appearance or use function of the model. It is recommended to only use the method of lifting the printing platform and 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 downward, and the last M solidified layers are used to complete the sealing of the liquid guide hole. After the model is printed, the model is removed from the printing platform, and the photosensitive resin retained in the liquid guide hole is poured out from the hole located on the starting surface, and the liquid guide hole is cleaned.

[0032] Specifically, the film stripping hole is in a straight line shape, and the angle between the film stripping hole and the vertical direction is 0-20°. When the angle between the film stripping hole and the vertical direction is 0°, the film stripping hole extends in the vertical direction. In the specific printing process of the model, the inclination angle of the film stripping hole can be set according to the shape of the model, but the angle between the film stripping hole and the vertical direction is as close to 0° as possible, so that the photosensitive resin can flow smoothly downward along the film stripping hole.

[0033] Furthermore, in order to prevent the model from cracking or breaking due to the pressure of the photosensitive resin in the demolding hole, the diameter of the hole area is set to be ≥10mm larger than the inner diameter of the demolding hole. This design makes the wall thickness of the demolding hole at least 5mm, so that the demolding hole area has a high strength and can withstand the pressure of the photosensitive resin in the demolding hole during the peeling process of the release film.

[0034] Specifically, the inner diameter of the demolding hole is 5-20 mm. 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 of the photosensitive resin, but also cause the photosensitive resin to solidify in the demolding hole, thereby blocking the demolding hole. The inner diameter of the demolding hole should not be too large. If the demolding hole is too large, it is easy to cause insufficient strength of the model and affect the quality of the product.

[0035] Furthermore, the total thickness of the M solidified layers is 1-5 mm, and the demolding hole does not penetrate the M solidified layers. The M solidified layers at the bottom are used to form a closed layer, which is used to close the lower end of the demolding hole to ensure the integrity of the model appearance. When printing the last M solidified layers, the peeling of the release film and the solidified layer is completed only by the rise of the printing platform and the adjustment of the air chamber pressure. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0037] Figure 2 yes Figure 1 Center AA view.

[0038] Figure 3 It is a schematic diagram of the structure of the connecting arm.

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

[0040] Figure 5 yes Figure 4 Magnified view of part B.

[0041] Figure 6 This is a state diagram of the 3D printer when it is working.

[0042] Figure 7 This is a diagram showing the state when the release film and the cured layer are partially peeled off.

[0043] Figure 8 This is a diagram showing the state when the release film and the cured layer are completely peeled off.

[0044] Fig. 9 This is a picture showing the release film returning to the printing working state. DETAILED DESCRIPTION

[0045] Example 1

[0046] See also Figure 1-Figure 3 A three-dimensional printer with inner and outer peeling of release film, comprising a workbench 11 and a material pump 18, on which a transmission mechanism is installed, 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 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 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, and 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 reciprocate in the vertical direction.

[0047] 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. The irradiation unit 19 is fixedly mounted on the bottom plate 113 of the workbench and is located below the liquid crystal screen 191. The material tank 40 is fixedly mounted on the top plate of the workbench and is located above the liquid crystal screen. The irradiation unit provides a shaped light beam for curing the photosensitive resin in the material tank 40. The irradiation unit 19 can be a digital light source processing (DLP) projection device or other types of projection devices (such as LCOS, LCD), but is not limited thereto.

[0048] The specific structure of the material tank 40 is described below. Figure 4 and Figure 5 The material trough 40 specifically includes a trough wall 41 and a light-transmitting plate 43 sealedly mounted at the bottom of the trough 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 support. A trough flange 46 is connected to the outside of the bottom of the trough wall 41. Bolts 175 fix the trough to the top plate 111 of the workbench through the trough flange 46, and the trough is detachably fixed to the workbench. In the vertical direction, the trough 40 is located directly above the LCD screen 191.

[0049] A release film 44 is installed in the material tank 40. The release film is a flexible film made of soft material. In this embodiment, the release film is specifically a polytetrafluoroethylene release film. The release film is located in the middle of the material tank in the vertical direction. The release film 44 divides the inner cavity of the material tank 40 into a gas bin 402 and a material bin 401 in the vertical direction, wherein the material bin 401 is located on the upper side of the release film, and the gas bin 402 is located on the lower side of the release film, that is, the material bin 401 is located on the upper side of the gas bin 402, and the photosensitive resin is contained in the material bin.

[0050] To facilitate the installation of the release film 44, in this embodiment, a first step surface 411 facing upward is provided on the inner circumferential surface of the groove wall 41, and the first step surface 411 is formed by the inner circumferential surface of the groove wall being recessed outward in the horizontal direction. An annular groove 412 is provided on the first step surface, and a first screw 413 passes through an annular metal gasket 414 and the release film and is screwed into the groove wall to fix the release film on the groove wall, wherein the annular metal gasket 414 is located on the upper side of the release film, and the annular metal gasket is opposite to the annular groove 412, the annular cylinder 42 is lined in the groove wall and pressed against the first step surface 411, and a sealing ring 415 is provided between the annular cylinder and the first step surface, and a second screw 416 passes through the annular cylinder from the inside to the outside in the horizontal direction and is screwed on the groove wall, thereby fixing the annular cylinder to the groove wall. In the accompanying drawings, only one second screw is shown as an example. When the air bin and the material bin are both connected to the atmosphere, the pressure on the upper and lower sides of the release film is the same, and the release film is in a flat state extending in the horizontal direction.

[0051] The gas bin is filled with gas. In this embodiment, air is directly used. In this application, there is no special requirement for the gas in the gas bin. Colorless and light-transmitting gas can meet the requirements. It can be understood that in other embodiments, inert gas such as nitrogen can also be used. The material bin is used to contain photosensitive resin. The printing platform can extend into the material bin and form a solidified layer on the printing platform.

[0052] An exhaust pipe 56 and an air intake pipe 51 connected to the gas bin 402 are installed on the tank wall. The exhaust pipe 56 and the air intake pipe 51 are connected to a main air pipe 50, which is fixed on the tank wall and connected to the gas bin 402. The charging device 52 is connected to the air intake pipe, and an air intake valve 53 is installed on the air intake pipe. The air intake valve 53 is located on the side facing the material tank. In this embodiment, the charging device is specifically a high-pressure gas tank with compressed air. It can be understood that in other embodiments, an air compressor, a high-pressure fan or other devices can also be directly used as the charging device 52. An exhaust valve 57 is installed on the exhaust pipe 56.

[0053] The inflation device is used to fill gas into the gas bin, and the exhaust pipe is used to discharge the gas in the gas bin; the gas in the gas bin is discharged through the exhaust pipe to reduce the supporting force of the gas in the gas bin on the release film, which can make the release film between the solidified layer and the groove wall protrude downward, and make the release film gradually peel off from the outside to the outside along the edge of the solidified layer; the inflation device can fill gas into the gas bin 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 material trough. The two detection ends of the differential pressure gauge 60 are respectively called the first detection end 61 and the second detection end 62, wherein the first detection end 61 is located at the bottom of the material bin, and the second detection end 62 is located in the air bin. The differential pressure gauge is used to detect the pressure between 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 groove wall corresponding to the silo 401 , and the short pipe 172 radially penetrates the groove wall and communicates with the silo 401 .

[0056] 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 forms a working surface 231.

[0057] In this embodiment, two clamping 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 clamping 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 clamping arms. The platform accommodating cavity has an opening facing away from the ball screw. Corresponding to each clamping 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 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, so that the clamping arm is detachably fixed to the printing platform. To avoid shaking, each clamping arm is fixed to the printing platform by two first bolts.

[0058] A liquid guide hole is provided on the printing platform. In the present embodiment, the liquid guide hole comprises an upper liquid hole 211 provided in the main body and a lower liquid hole 232 provided in the model plate. The upper liquid hole 211 and the lower liquid hole 232 both extend in the vertical direction and are coaxially provided. The upper liquid hole 211 and the lower liquid hole 232 are connected up and down, and the upper liquid hole 211 penetrates the upper end surface of the main 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 together 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 is formed as a liquid inlet, and the lower end of the liquid guide hole is formed as a liquid outlet.

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

[0060] For the convenience of connection, a liquid guide tube 26 is installed on the printing platform. The liquid guide tube is specifically a stainless steel tube. The liquid guide tube is sealed and inserted into the lower liquid hole from top to bottom through the upper liquid hole. The material pump 18 is located in the inner cavity 112 of the workbench 11 and 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 tube 26 through the liquid outlet pipe 182. In order to facilitate the up and down movement of the printing platform, the liquid outlet pipe adopts a plastic hose. Specifically in this embodiment, the upper liquid hole is a threaded hole, and the liquid guide tube is screwed into the upper liquid hole.

[0061] To prevent the liquid guide tube from extending downward out of the liquid guide hole, in this embodiment, the lower liquid hole is a stepped hole with a large hole facing upward, so that the stepped hole has a second stepped surface facing upward, and the lower end of the liquid guide tube is sealingly pressed against the second stepped surface of the stepped hole. To ensure the sealing, a rubber sealing ring is provided between the second stepped surface and the liquid guide tube to reduce or prevent the photosensitive resin in the liquid guide hole from entering the gap between the main body and the model plate.

[0062] 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 is connected to the liquid outlet, and the demolding hole penetrates part of the solidified layer downward. After a solidified layer penetrated by the demolding hole is completed, the photosensitive resin in the material tank can be fed into the liquid guide hole under the drive of the material pump, so that the release film is gradually peeled off from the solidified layer from the inside to the outside.

[0063] For details about the demolding hole 31, please refer to the relevant content in Example 2 below.

[0064] Example 2

[0065] See also Figure 6-Figure 9 This embodiment describes a three-dimensional printing method, which is performed using a three-dimensional printer with a release film inside and outside peeling in Embodiment 1. The three-dimensional printing method includes the following steps:

[0066] (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, and the area enclosed by the double-dotted line 91 is the hole forming area. For clear display, the double-dotted line 91 extends upward to the model plate 23, and the double-dotted line 91 extends downward to the bottom of the model 30. For clear display, the model 30 is not provided with a section line.

[0067] In this embodiment, the film stripping hole is in a straight line shape, and the film stripping hole extends in the vertical direction, that is, the angle between the film stripping hole and the vertical direction is 0°. It can be understood that in other embodiments, the film stripping hole can also be set at an angle, and the angle between the film stripping hole and the vertical direction can specifically 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 hole forming area is 20mm, the demolding hole is a circular hole, and the inner diameter of the demolding hole is 10mm, so that the set diameter of the hole forming area is 10mm 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, and the extension direction of the hole forming area is perpendicular to the outer end face, and the outer end face can be used as the starting face 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 990 solidified layers downward from the starting face, that is, N=1000, M=10, NM=990, N>M. The thickness of each solidified layer is 0.1mm.

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

[0070] (2) Close the exhaust valve 57 and open the air inlet valve 53. Fill the air chamber with gas through the inflation device to make the pressure on the upper and lower sides of the release film the same, so that the release film is placed horizontally, and close the air inlet valve 53.

[0071] 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 liquid guide hole upward and penetrates downward through the lower end surface of the solidified layer located at the lower side.

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

[0073] (2.1) Lift the printing platform upwards;

[0074] (2.2) Start the material pump 18 to feed the photosensitive resin in the material tank into the liquid guide hole, and then into the demolding hole 31, push the release film downward, so that the release film is peeled off from the inside to the outside along the edge of the demolding hole, and an inner peeling opening 901 is generated 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 material tank.

[0075] (2.3) Open the exhaust valve 57 to discharge the gas in the air chamber to the outside, thereby reducing the pressure in the air 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 is gradually peeled off from the outside to the inside along the edge of the solidified layer, so that an external peeling opening 902 is generated between the outer edge of the solidified layer and the release film.

[0076] See also 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 are connected to each other, so that the release film is completely peeled off from the solidified layer.

[0077] 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 can be reduced when the release film is peeled off, thereby improving the printing efficiency.

[0078] The solidified layers are continuously printed until 990 solidified layers are printed, that is, NM solidified layers are printed. As the printing progresses, the demolding hole is extended as the model is extended.

[0079] During the printing interval between two adjacent curing layers, the material pump stops working.

[0080] See also Fig. 9 After the release film and the solidified layer are peeled off, the exhaust valve 57 is closed and the air inlet valve 53 is opened to allow the compressed air in the high-pressure gas tank to enter the gas chamber, increase the pressure of the gas chamber, observe the differential pressure gauge 60, make the pressure on the upper and lower sides of the release film the same, restore the horizontal setting of the release film, and then close the air inlet valve 53.

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

[0082] In order to maintain the integrity of the model appearance, the M solidified layers at the bottom together form a closed layer 32, which closes the lower end of the demolding hole to maintain the integrity of the model appearance. In this embodiment, the closed layer is composed of the 10 solidified layers at the bottom, that is, the M solidified layers together constitute the closed layer. For details, please refer to Figure 2 In this embodiment, the thickness H of the sealing layer is 1 mm. It can be 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.

[0083] When printing the last 10 cured layers, the release film and the cured layer are peeled off by only adjusting the air pressure of the air chamber to speed up the peeling process, and the peeling process is no longer accelerated by injecting photosensitive resin into the demolding hole.

[0084] After the model is printed, the model is removed from the printing platform, the photosensitive resin retained in the liquid guide hole is poured out from the orifice located on the starting surface, and the liquid guide hole is cleaned.

Claims

1. A three-dimensional printer with a release film peeling inside and outside, characterized in that: The invention comprises a workbench and a material pump, 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; a liquid guide hole is provided on the printing platform, the liquid guide hole runs 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 of the liquid guide hole forms a liquid outlet; The material trough is fixedly installed on the workbench, and the material trough includes a trough wall and a light-transmitting plate sealedly installed at the bottom of the trough wall. A release film is installed in the material trough, and the release film is located in the middle part of the material trough in the up-down direction. The release film divides the inner cavity of the material trough into an air bin and a material bin in the up-down direction. The material bin is located on the upper side of the air bin, and is filled with gas. The material bin contains photosensitive resin. An exhaust pipe and an air inlet pipe connected to the air bin are installed on the trough wall, and an air charging device is connected to the air inlet pipe, and an air inlet valve is installed on the air inlet pipe, and an exhaust valve is installed on the exhaust pipe; The gas charging device is used to charge gas into the gas chamber, and the exhaust pipe is used to discharge 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 can protrude downward, and the release film can be gradually peeled off from the outside to the outside along the edge of the solidified layer; the gas charging device can charge gas into the gas chamber to restore the release film to its original state; The inlet of the material pump is connected to the material bin 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 demolding hole is formed in the model. The upper end of the demolding hole is connected to the liquid outlet, and the demolding hole penetrates at least one solidified layer downward; after completing a solidified layer penetrated by the demolding hole, the photosensitive resin in the material tank can be fed into the liquid guide hole under the drive of the material pump, so that the release film is gradually peeled off from the solidified 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 is formed as a working surface, and the model is bonded to the working surface; the liquid guide hole includes an upper liquid hole arranged in the main body and a lower liquid hole arranged in the model plate, a liquid guide tube is sealedly inserted into the lower liquid hole from top to bottom through the upper liquid hole, the outlet of the material pump is connected to the liquid guide 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 lower liquid hole is a stepped hole, the large hole of which faces upward, 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: 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.

5. The 3D printer according to claim 1, characterized in that: The material pump is fixedly installed in the inner cavity of the workbench.

6. A three-dimensional printing method, characterized in that: The three-dimensional printing method is performed by using a three-dimensional printer with an inner and outer peeling type of the release film according to any one of claims 1 to 5, and the three-dimensional printing method 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) Make the pressure on the upper and lower sides of the release film the same so that the release film is placed horizontally; 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 is formed in the hole forming area. The demolding hole is connected to the liquid guide hole upward. 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 following steps (2.1), (2.2) and (2.3) are performed simultaneously: (2.1) Lift the printing platform upwards; (2.2) Start the material pump to feed the photosensitive resin in the material tank into the liquid guide hole and then into the demolding hole, so that the release film is peeled off from the inside to the outside along the edge of the demolding hole until the solidified layer and the release film are completely peeled off, and the photosensitive resin in the liquid guide hole returns to the material tank; (2.3) Reduce the pressure in the air chamber, so that the release film between the solidified layer and the groove wall protrudes downward, and the release film is gradually peeled off from the outside to the outside along the edge of the solidified layer; simultaneously, lift the printing platform upward, so that the release film and the solidified layer are completely peeled off; After the release film and the solidified 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 solidified layer until NM solidified layers are printed; During the printing interval between two adjacent curing layers, the material pump stops working; (3) Complete the printing of the last M solidified layers.

7. The three-dimensional printing method according to claim 6, characterized in that: The film stripping hole is straight, and the angle between the film stripping hole and the vertical direction is 0-20°.

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

10. The three-dimensional 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.

Images