A printing method based on a sinking type light curing printing device

Abstract

The application discloses a printing method based on a sinking type light curing printing device, and the device comprises a multi-axis mechanical arm, and a printing platform fixed at the end of the multi-axis mechanical arm. The printing method comprises the following steps: acquiring a critical liquid surface support control angle of printing paste, setting a liquid surface support control angle of a frame protection model according to the critical liquid surface support control angle, constructing the frame protection model according to the size of a printing model, acquiring slice files of the printing model and the frame of the protection model, laying the printing paste on the printing platform according to the slice graphic shape with the outer contour of the frame of the protection model as a boundary, scraping the printing paste with a scraper after the laying is completed, projecting and selectively curing the printing paste according to the slice graphic by using a DLP projection light machine, and printing layer by layer until the printing is completed. The printing platform is arranged at the end of the multi-axis mechanical arm, the deposition direction of the material can be changed in the manufacturing process, and the support-free printing of curved structure parts, overhanging parts and the like can be realized.

Description

Technical Field

[0001] This invention relates to the field of additive manufacturing technology, and in particular to a printing method based on a sunken photopolymerization printing device. Background Technology

[0002] Stereolithography (SLA), as the earliest 3D printing technology, is one of the most mature and widely used in the industry. The working principle of SLA is to use a laser beam of a specific wavelength to irradiate liquid photosensitive resin, causing it to solidify in the area scanned by the laser beam. During the printing process, the platform descends layer by layer, and the laser beam tracks and fills the two-dimensional cross-section of the model, repeating the solidification process layer by layer until a solid 3D object is formed. The pattern formation of each layer is precisely controlled by the movement of the laser beam, so theoretically, large-sized models can be printed. The newly developed DLP 3D printing technology, or Digital Light Processing 3D printing technology, is also a type of stereolithography 3D printing technology and is known as digital light processing rapid prototyping technology.

[0003] However, due to its layered manufacturing strategy, where material is deposited unidirectionally along the vertical direction (z-axis) during printing, current photopolymer 3D printing technology requires the addition of numerous support structures when printing overhanging structures. First, these support structures increase the complexity of the printing process. To maintain the stability of the printed object and prevent deformation or collapse during layer-by-layer curing, support structures need to be added at specific locations. These support structures not only increase printing complexity but also require post-processing after printing, such as grinding and cutting, to remove them, increasing the overall workload. Second, support structures can lead to a decrease in surface quality. The contact surface between the support structure and the printed object may leave marks after printing, affecting the surface quality of the printed object. This effect is particularly pronounced in applications requiring high-precision surfaces. Finally, the design of support structures requires experience and skill. Designing support structures reasonably to ensure the stability of the printed object while minimizing the impact on surface quality and reducing material and cost consumption requires operators with extensive experience and expertise. Improper design can lead to printing failures or poor-quality printed objects.

[0004] Therefore, the existing technology still needs further improvement and enhancement. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the present invention provides a printing method based on a sunken photopolymerization printing device, which aims to solve the problem that the existing photopolymerization printing method requires the addition of a support structure, which affects the surface quality of the printed object.

[0006] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows:

[0007] In a first aspect, a printing method based on a recessed photopolymerization printing device is provided, wherein the recessed photopolymerization printing device includes: a DLP projection optical engine, a doctor blade feeding mechanism, a printing platform, and a multi-axis robotic arm; the printing platform is located below the DLP projection optical engine, and the printing platform is fixed to the end of the multi-axis robotic arm;

[0008] The printing method includes:

[0009] Obtain the critical liquid surface support control angle of the printing paste, and set the liquid surface support control angle of the frame protection model based on the critical liquid surface support control angle;

[0010] Based on the size of the printed model, construct a border protection model that surrounds the outside of the printed model and is at the same height as the highest point of the printed model in the vertical direction. Obtain slice files of the border of the printed model and the protection model. The slice files include slice graphics and printing parameters of the corresponding layers.

[0011] Layer printing: Adjust the position of the printing platform so that the surface of the printing platform is at the focal point of the DLP projection engine; adjust the height of the squeegee so that the bottom of the squeegee is level with the top of the printing platform; using the outer contour of the protective model's frame as the boundary, lay the printing paste on the printing platform according to the shape of the slice pattern, and scrape the paste with the squeegee after laying; use the DLP projection engine to project and selectively cure the printing paste according to the slice pattern;

[0012] Repeat the layer printing steps until printing is complete.

[0013] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. The purpose and beneficial effects of the present invention can be better achieved and realized through the following preferred technical solutions.

[0014] As a preferred technical solution, in the printing method based on the sinking photopolymerization printing device, the liquid surface support control angle is not less than the critical liquid surface support control angle.

[0015] As a preferred technical solution, the printing method based on the sunken photopolymerization printing device, wherein the slice pattern of the border protection model includes a first pattern and a second pattern, the first pattern is disposed around the periphery of the second pattern, the second pattern surrounds the periphery of the slice pattern of the printing model, and the outline of the second pattern is the same as or similar to the outline of the slice pattern of the printing model.

[0016] As a preferred technical solution, in the printing method based on the sunken photopolymerization printing device, the distance between the outline of the second pattern and the outline of the slice pattern of the printing model is 0.5-5mm.

[0017] As a preferred technical solution, the printing method based on a submerged photopolymerization printing device, wherein obtaining the critical liquid level support control angle of the printing paste specifically includes:

[0018] Construct a square printing test model, obtain the slice file of the printing test model, and import it into the printing device control software;

[0019] The printing platform is positioned horizontally, and the printing platform is located at the first printing position in the height direction;

[0020] Add the printing paste to the feeding device and print layer by layer according to the slice file until printing is complete;

[0021] Measure the tilt angles corresponding to the four sides of the printed part, and take the largest angle as the critical liquid level support control angle corresponding to the printing paste.

[0022] As a preferred technical solution, the printing method based on a sunken photopolymerization printing device, wherein the printing model can be a curved or overhanging structure, and the printing method further includes:

[0023] Select the corresponding axis according to the curved structure, and slice the printed model with the axis as the reference to obtain the corresponding slice file. The slice file includes the slice graphic and the printing parameters of the corresponding layer.

[0024] According to the method for obtaining the critical liquid level support control angle of the printing paste, the liquid level support control angle of the printing paste is defined;

[0025] Based on the curved structure printing model, select the corresponding axis and set the border of the protective model. In the slicing software, use the axis as a reference to slice the printing model and the border protection model to obtain the corresponding slice file;

[0026] Import the sliced ​​file into the printing device control software;

[0027] Based on the slicing parameters of the current printing layer in the slicing file, the multi-axis robotic arm is controlled to move the printing platform to the printing position of the current printing layer, and the posture of the printing platform is adjusted so that the layer to be cured on the printed part is always in a horizontal state.

[0028] Secondly, a sunken photopolymerization printing device includes: a printing platform, a doctor blade feeding mechanism, and a DLP projection optical engine, wherein it further includes: a multi-axis robotic arm; the printing platform is fixed to the end of the multi-axis robotic arm, and the movement and posture of the printing platform are controlled by the robotic arm.

[0029] Beneficial effects: Compared with existing technologies, this invention, based on sunken photopolymerization printing technology, eliminates the need for a release film and release process, and the printed parts are unaffected by release forces. Therefore, it has a wide range of material adaptability and produces high-quality printed parts. The printing platform is located at the end of a multi-axis robotic arm, allowing for changes in material deposition direction during manufacturing. This enables supportless printing of curved structures, overhanging parts, etc., and improves print quality due to the supportless printing capability. Attached Figure Description

[0030] Figure 1 This is a partial structural diagram of the sunken photopolymerization printing device in this invention;

[0031] Figure 2 This is a schematic diagram of the multi-material feeding device in this invention;

[0032] Figure 3 This is a schematic diagram of the critical liquid level support control angle δ0 in this invention;

[0033] Figure 4 This is a schematic diagram of the liquid surface support printing method in this invention;

[0034] Figure 5 This is a schematic diagram of another liquid surface support printing method in this invention;

[0035] Figure 6 This is a schematic diagram showing the relative positions of the inner and outer frames of the liquid level protection and the printed parts during the printing process in this invention.

[0036] Figure 7 This is a schematic diagram of the printing method of the inner frame with conformal liquid surface support in this invention;

[0037] Figure 8 This is a schematic diagram of the printed part with a triangular cross-section and its inner and outer frame structures for liquid level protection in this invention;

[0038] Figure 9 This is a schematic diagram of the slicing method in this invention;

[0039] Figure 10This is a schematic diagram illustrating the principle of unsupported printing setup for printing curved structural components in this invention;

[0040] Figure 11 This invention relates to the calibration of the critical liquid level support control angle δ0 of Forml Ab's White resin.

[0041] Figure 12 This is a schematic diagram of the standard printing method in this invention;

[0042] Figure 13 The conformal liquid surface protection frame in this invention improves the edge morphology of the printed parts;

[0043] Figure 14 This is a schematic diagram of the printed curved sample structure in this invention. Detailed Implementation

[0044] This invention provides a printing method based on a recessed photopolymerization printing device. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0045] Furthermore, the features, operations, or characteristics described in the specification can be combined in any suitable manner to form various embodiments. Simultaneously, the steps or actions in the method description can be rearranged or adjusted in a manner readily apparent to those skilled in the art. Therefore, the various orders in the specification and drawings are merely for the clear description of a particular embodiment and do not imply a mandatory order, unless otherwise stated that a particular order must be followed. The component designations used herein, such as "first," "second," etc., are merely for distinguishing the described objects and do not have any sequential or technical meaning.

[0046] This invention discloses a submerged photopolymerization printing device, such as... Figure 1 As shown, it mainly includes: a DLP projection engine 10, a doctor blade 21, a guide rail 22, a slider 23, a feed head 24, a printing platform 30, and a multi-axis robotic arm 40. The printing platform 30 is fixed to the end of the multi-axis robotic arm via a flange, and the printing platform 30 is located below the DLP projection engine. The printing platform 30 is a flat plate structure, and its upper surface is used to support the printing paste and the printed parts formed by the printing paste. The multi-axis robotic arm 40 can drive the printing platform 30 to move in different directions, such as controlling the tilt and rotation angle of the printing platform.

[0047] In the embodiments disclosed in this invention, the DLP projection optical engine 10 is fixed above the printing platform 30. The DLP projection optical engine 10 has a light outlet facing the printing platform 30 to project UV light in the direction of the printing platform 30. It is readily understood that the DLP projection optical engine 10 is fixed to a support structure.

[0048] In the embodiments disclosed in this invention, the scraper feeding mechanism is located between the printing platform 30 and the DLP projection engine 10. This scraper feeding mechanism consists of a scraper, a connecting assembly, a first moving module, and a second moving module. The scraper is mounted on the connecting assembly, which is connected to the first moving module, which drives the connecting plate to move horizontally. The second moving module is mounted on one side of the connecting assembly and is used to mount the feeding head of the feeding assembly. The second moving module drives the feeding head to move horizontally along the guide rail 22. The feeding head is connected to the feeding device via pipeline, and the printing paste is extruded on demand using methods such as air pressure, a peristaltic pump, an injection pump, or a screw pump. The direction of movement of the feeding head is perpendicular to the overall running direction of the connecting assembly in the horizontal plane. Figure 2 This is a schematic diagram of a multi-material feeding device, showing a peristaltic pump controlling material extrusion. Resin A is a rigid photosensitive resin, and resin B is a flexible photosensitive resin. Using the device described in this invention, multi-material and continuous material gradient drop-down photopolymerization printing can be achieved.

[0049] Combination Figure 1 The first moving module includes a guide rail and a slider along the X-axis, and the second moving module includes a guide rail and a slider along the Y-axis. It is easy to understand that the drive mechanism for moving the moving modules can be a motor belt drive mechanism commonly used in the prior art, or other drive mechanisms.

[0050] Based on the same inventive concept, this invention also discloses a printing method based on a sunken photopolymerization printing device, the printing method comprising:

[0051] Step S10: Obtain the critical liquid level support control angle of the printing paste, and set the liquid level support control angle of the frame protection model according to the critical liquid level support control angle.

[0052] Step S20: Construct a border protection model that surrounds the outside of the printed model and is at the same height as the highest point of the printed model in the vertical direction, according to the size of the printed model. Obtain the slice file of the border of the printed model and the protection model. The slice file includes slice graphics and printing parameters of the corresponding layers.

[0053] In this invention, a protective frame for the printing paste is designed based on the dimensions of the printed part, enclosing the printed part; and the height of the frame is equal to the height of the highest point of the printed part. During the printing process, the frame is printed synchronously with the printed part. The frame can define the area of ​​the printed part, retaining the paste within the printing area. The protective frame model surrounds the part to be printed, forming a liquid surface support for the layer to be printed within the printing area.

[0054] In this invention, the critical liquid surface support control angle δ0 of the printing paste is obtained in advance, and the liquid surface support control angle of the protective model's frame is set based on δ0. The liquid surface support control angle is not less than the critical liquid surface support control angle. This avoids structural defects at the edges of the frame during printing, which could lead to liquid surface support failure and printing failure.

[0055] Specifically, the inventors discovered in their research that when there is no resin level around the printed part to provide liquid level support for the layer to be cured, under the influence of gravity and liquid-solid interface wetting, the slurry above the printed part will exhibit a phenomenon of top flattening and edge slippage. The intended square printed part cannot be formed, instead presenting a gradually converging four-sided pyramid shape. Depending on the different rheological properties of the printing slurry, each slurry has a corresponding critical liquid level support control angle δ0 at its corresponding printing layer thickness setting, such as... Figure 3 As shown. With the same slurry, the critical liquid level support control angle δ0 may differ depending on the printing layer thickness setting.

[0056] In this invention, the calibration steps for the critical liquid level support control angle δ0 are as follows:

[0057] For any type of slurry, it is necessary to first calibrate its critical liquid level support control angle δ0 under different layer thickness settings. For the same slurry, the critical liquid level support control angle δ0 may be different depending on the printing layer thickness setting.

[0058] Design a square part for printing test, such as a 20x20x10mm square part. The part's STL file is sliced ​​to generate a slice file suitable for the printer, which is then imported into the printer control software.

[0059] The robotic arm is set back to its initial default position. At this point, the printing platform is horizontal and positioned at the first printing level in the vertical direction.

[0060] Add the printing paste into the feeding device and start printing according to the set square part slice file.

[0061] During the printing process, due to gravity and the wetting effect of the liquid-solid interface, the ink spreads evenly on the top of the printed part and slides along the edges, forming a gradually converging four-sided pyramid shape. After printing, the printed part is removed, and the tilt angles of the four sides are measured. The largest angle is defined as the critical liquid surface support control angle δ0 corresponding to the current printing ink.

[0062] Step S30, Layer Printing: Adjust the position of the printing platform so that the surface of the printing platform is at the focal point of the DLP projection engine; adjust the height of the squeegee so that the bottom of the squeegee is level with the top of the printing platform; using the outer contour of the protective model's frame as the boundary, lay the printing paste on the printing platform according to the shape of the slice pattern, and scrape the paste with the squeegee after laying; use the DLP projection engine to project and selectively cure the printing paste according to the slice pattern.

[0063] Specifically, the multi-axis robotic arm is returned to its initial default position, at which point the printing platform is horizontal and positioned for the first layer of printing. The scraper and feed head return to their initial positions. Under motor control, the feed head lays the printing paste according to the predetermined trajectory and spacing, using the outer contour of the sliced ​​graphic (including the printed part and protective frame) as the boundary. The feeding device continuously supplies paste during the feed head's movement. After feeding is complete, the scraper scrapes the paste; the DLP projection engine projects the printing paste according to the sliced ​​graphic and selectively cures it; during printing, the sliced ​​files corresponding to the inner and outer frames of the liquid surface protection are formed along with the printed part. Under the control of the multi-axis robotic arm, the printing platform descends by one layer thickness, completing one layer of printing.

[0064] Step S40: Repeat the layer printing steps until printing is complete. Remove the protective frame, take out the printed part, and perform subsequent cleaning, post-curing and other treatments.

[0065] This invention employs a material extrusion device to supply material from the top of the printing platform, eliminating the need to pre-fill the resin tank with a large amount of printing paste, thus significantly saving paste and reducing printing costs. The printing platform, located at the end of the robotic arm, can change the material deposition direction during printing. Reducing or even eliminating support components during printing simplifies the printing process and improves print quality.

[0066] In one implementation of the present invention, such as Figure 4 As shown, a liquid level protection frame is set around the printed part. During the printing process, the liquid level protection frame is printed synchronously and layer by layer with the printed part. The liquid level support control angle of the liquid level protection frame is δ. The liquid level support control angle δ is set not less than the critical liquid level support control angle δ0. The liquid level protection frame maintains a certain distance from the printed part to prevent the liquid from over-curing and sticking to the printed part due to slurry scattering.

[0067] In one implementation of the present invention, such as Figure 5 As shown, the outer liquid level protection frame provides liquid surface support for the printing area, ensuring relatively good liquid surface flatness. The inner liquid level protection frame maintains a small frame-sample distance from the printed part (depending on the degree of over-curing of the ink; generally, for high-precision inks with low over-curing, a smaller frame-sample distance can be used, such as 0.5-5mm), providing high-quality liquid surface support for the cured layer on the printed part, preventing edge distortion and achieving high morphological accuracy. The outer and inner liquid level protection frames can be designed to be connected or disconnected at the top. During printing, the relative positions of the outer and inner liquid level protection frames, the printed part, and the ink are as follows... Figure 6 As shown.

[0068] In one implementation of the present invention, the inner frame for liquid level protection can be set as a conformal frame, such as... Figure 7 As shown, the inner frame for liquid level protection follows the outer contour of the printed part and always maintains a close distance from it. By setting the inner frame for liquid level protection as a conformal frame, the inner frame for liquid level protection can always maintain a close distance from the printed part, providing high-quality liquid level support and achieving high-precision printing.

[0069] Furthermore, in the horizontal direction, for irregularly shaped printed parts, the liquid level protection inner frame can also be designed as a conformal frame in the X and Y planes, rather than a typical rectangle or circle. For example... Figure 8 The printed part shown has a triangular cross-section and its inner and outer frames for liquid level protection.

[0070] In one implementation of the present invention, when printing a curved structural component, a corresponding axis is selected based on the curved structure, and the border of the protective model is set. In slicing software, the printed model and the border protection model are sliced ​​using the axis as a reference to obtain corresponding slice files; all sliced ​​graphics obtained are perpendicular to the axis (e.g., ...). Figure 9 (As shown); import the slice file into the printing device control software, and according to the slice parameters of the current printing layer in the slice file, control the multi-axis robotic arm to move the printing platform to the printing position of the current printing layer, and adjust the posture of the printing platform so that the layer to be cured on the printed part is always in a horizontal state.

[0071] Specifically, printing such as Figure 10 When printing a sample with a cantilevered bending structure as shown in (a), the printing process can be divided into the following steps: Figure 10 The three stages (stages I, II, and III) in (b) are described. For the corresponding printed copy, add the following: Figure 10 The liquid level protection frame shown in (c) is used in Part I of the printout. Figure 10Print using the settings shown in (d), keeping the printing platform level, and print layer by layer. Part II of the printed document should be printed as shown in [reference needed]. Figure 10 Printing is performed using the settings shown in (e). Depending on the angle of the printed part, the printing platform, under the control of a multi-axis robotic arm, rotates at a certain angle to print layer by layer. During the printing process, the angle α between the printing platform and the horizontal line... II It changes gradually, ensuring that the layer to be cured on the printed part remains horizontal at all times. Part III of the printed part uses the following... Figure 10 Printing is performed using the settings shown in (f). Depending on the angle of the printed part, the printing platform, controlled by a multi-axis robotic arm, rotates at a certain angle to print layer by layer. Since part III of the printed part is a straight rod, the angle α between the printing platform and the horizontal line during printing is... III It is fixed, ensuring that the layer to be cured on the printed part remains horizontal at all times.

[0072] The following specific embodiments will further explain and illustrate the above-mentioned technical solutions provided by the present invention.

[0073] Example 1: Test of critical liquid level support control angle δ0;

[0074] Using Forml AB's WHITE resin and the aforementioned printing method, a 20x20x10mm square part was printed directly on the printing platform without a liquid level protection frame. The print layer thickness was set to 50µm, and the printing parameters were set to an ultraviolet light intensity of 8mW / cm². 2 The single-layer exposure time was set to 6 seconds. Because the printed part and the layer to be cured remained above the liquid surface during printing, under the influence of gravity and the wetting effect of the liquid-solid interface, the layer of slurry to be cured above the printed part exhibited a phenomenon of flattening at the top and slipping at the edges. The pre-set square printed part could not be formed, instead appearing as a gradually converging four-sided pyramid shape, such as... Figure 11 As shown. Along the direction of the scraper's movement, the left and right tilt angles are basically the same; comparing the front and rear tilt angles, the rear liquid surface support control angle δ is larger. This is because Form Labs' white resin exhibits a certain degree of shear-thinning characteristics. The front liquid surface support control angle δfront is mainly affected by the static viscosity of the slurry, while the rear liquid surface support control angle δrear is mainly affected by the dynamic viscosity of the slurry (corresponding to the shear rate of the scraper's movement). The largest tilt angle δrear is defined as the critical liquid surface support control angle δ0 (e.g., ...). Figure 11 (As shown, 24°).

[0075] Example 2: Schematic diagram of standard printing method;

[0076] Using Forml AB's white resin, printing as shown Figure 12Based on the critical liquid level support control angle δ0 determined in Example 1, the inner and outer frames for liquid level protection of printed samples 101 and 102 are designed as shown in the figure. The liquid level protection frame is divided into inner and outer frames, and the liquid level support control angle δ is set to δ0 + 5°. The height of the liquid level protection frame is set to the height of the tallest sample among printed samples 101 and 102, i.e., the height of sample 101. The frame-sample spacing is set to 1 mm. The printing layer thickness is set to 50 μm, and the printing parameters are set to an ultraviolet light intensity of 8 mW / cm². 2 The single-layer exposure time is set to 6 seconds.

[0077] Example 3: Printing using a conformal liquid surface protection frame

[0078] Using zirconia ceramic slurry, printing such as Figure 12 For sample printout 101, the liquid surface support control angle δ was set to 30°, the inner frame for liquid surface protection was a conformal frame, and the frame-sample spacing was set to 1mm. The printing layer thickness was set to 25µm, and the printing parameters were set to an ultraviolet light intensity of 8mW / cm². 2 The single-layer exposure time was set to 6 seconds. The edge morphology of the printed part is as follows: Figure 13 As shown, under a light microscope, the edges exhibit a good right-angle shape, which matches the original design model.

[0079] Example 4:

[0080] (1) Slice file settings: according to Figure 14 The sample structure is determined by selecting a suitable 3D curve as the axis. Using this axis as a reference, the border of the protective model is defined. In slicing software, the printed model and the border protective model are sliced ​​using this axis as a reference to obtain corresponding slice files; ensuring that all sliced ​​graphics are perpendicular to this axis. The slice layer thickness is set based on the spacing dimensions along this axis. The slice file includes the sliced ​​graphics and their X / Y / Z positions, tilt angles, rotation angles, printing parameters, and other information.

[0081] (2) The printing device is reset; the robotic arm is reset, and the scraper and feed head return to their initial positions.

[0082] (3) The printing platform moves to the printing position of the current layer: Based on the X / Y / Z position, tilt angle, and rotation angle of the current printing layer in the slice file, the robotic arm controls the molding platform to move to the printing position and posture of the current layer.

[0083] (4) Under the control of the motor, the feeding head lays the material according to a certain trajectory and spacing, based on the outer contour of the sliced ​​graphic (including the printed part and the liquid level protection frame). The feeding device continuously feeds the material during the feeding head's movement.

[0084] (5) After the material is fed, the scraper will scrape the material.

[0085] (6) The UV light machine projects and selectively cures the printing paste according to the slice file graphic; during the printing process, the slice files corresponding to the inner and outer frames of the liquid surface protection are formed together with the printed parts.

[0086] (7) Repeat steps (3), (4), (5), and (6) until printing is complete.

[0087] (8) Remove the inner and outer frames of the liquid level protection, take out the printed parts, and perform subsequent cleaning, post-curing and other treatments.

[0088] In summary, this invention provides a printing method based on a recessed photopolymerization printing device, which includes: a DLP projection optical engine, a doctor blade feeding mechanism, a printing platform, and a multi-axis robotic arm; the printing platform is located below the DLP projection optical engine and is fixed to the end of the multi-axis robotic arm; the printing method includes: obtaining the critical liquid level support control angle of the printing paste; setting the liquid level support control angle of the frame protection model based on the critical liquid level support control angle; and constructing a frame protection model that surrounds the outside of the printing model and is vertically level with the highest point of the printing model according to the size of the printing model. The process involves: obtaining slice files of the printed model and the border protection model, the slice files including slice graphics and corresponding layer printing parameters; layer printing: adjusting the position of the printing platform so that the surface of the printing platform is at the focal point of the DLP projector; adjusting the height of the squeegee so that the bottom of the squeegee is level with the top of the printing platform; using the outer contour of the border protection model as the boundary, laying the printing paste on the printing platform according to the shape of the slice graphics, and scraping the paste with a squeegee after laying; using the DLP projector to project and selectively cure the printing paste according to the slice graphics; repeating the layer printing steps until printing is complete.

[0089] This invention combines a multi-axis robotic arm with a printing platform, and sets the liquid surface support control angle of the frame protection model based on the critical liquid surface support control angle of different printing materials. The printing protection frame is designed with two parts, an inner and an outer one, with the inner one being a conformal frame that can change the material deposition direction during manufacturing. Therefore, it enables supportless printing of curved structural parts, overhanging parts, etc. By setting a liquid surface support fence that is printed synchronously with the printed part, liquid surface support is provided, significantly improving the morphological accuracy of the printed part. Furthermore, this invention uses a material extrusion device to supply material from the top of the printing platform, eliminating the need to pre-fill the resin tank with a large amount of printing paste, resulting in significant paste savings and reduced printing costs. Based on sink-type photopolymerization printing technology, this invention does not require a release film or release process, and the printed part is not affected by release force. Therefore, it has a wide range of material adaptability and produces high-quality printed parts.

[0090] It should be understood that the application of the present invention is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A printing method based on a recessed photopolymerization printing device, characterized in that, The sunken photopolymerization printing device includes: a DLP projection optical engine, a doctor blade feeding mechanism, a printing platform, and a multi-axis robotic arm; the printing platform is located below the DLP projection optical engine and is fixed to the end of the multi-axis robotic arm; The printing method includes: Obtain the critical liquid surface support control angle of the printing paste, and set the liquid surface support control angle of the frame protection model according to the critical liquid surface support control angle; the liquid surface support control angle is the angle between the plane where the liquid surface protection outer frame is located and the vertical direction. Based on the size of the printed model, construct a border protection model that surrounds the outside of the printed model and is at the same height as the highest point of the printed model in the vertical direction. Obtain slice files of the printed model and the border protection model. The slice files include slice graphics and printing parameters of the corresponding slice layers. Layer printing: Adjust the position of the printing platform so that its surface is at the focal point of the DLP projector; adjust the squeegee height so that the bottom of the squeegee is level with the top of the printing platform; using the outer contour of the border as the boundary, lay the printing paste on the printing platform according to the shape of the slice pattern, and scrape the paste with the squeegee after laying; use the DLP projector to project and selectively cure the printing paste according to the slice pattern. Repeat the layer printing process until printing is complete; The liquid surface support control angle is not less than the critical liquid surface support control angle; The border protection model's border slice graphic includes a first pattern and a second pattern. The first pattern is set around the second pattern, and the second pattern surrounds the periphery of the printed model's slice graphic. The outline of the second pattern is similar to the outline of the printed model's slice graphic. The outer border protection frame is printed according to the first pattern; the inner border protection frame is printed according to the second pattern; the inner border protection frame and the outer border protection frame are connected at the top.

2. The printing method based on a recessed photopolymerization printing device according to claim 1, characterized in that, The distance between the outline of the second pattern and the outline of the slice graphic of the printed model is 0.5-5mm.

3. The printing method based on a recessed photopolymerization printing device according to claim 1, characterized in that, The critical liquid level support control angle for obtaining the printing paste specifically includes: Construct a square printing test model, obtain the slice file of the printing test model, and import it into the printing device control software; The printing platform is positioned horizontally, and the printing platform is located at the first printing position in the height direction; Add the printing paste to the feeding device and print layer by layer according to the slice file until printing is complete; Measure the angles between the planes containing the four sides of the printed part and the vertical direction, and define the largest angle as the critical liquid level support control angle corresponding to the printing paste.

4. The printing method based on a recessed photopolymerization printing device according to claim 3, characterized in that, The printed model is a curved or overhanging structure, and the printing method further includes: The liquid level support control angle of the printing paste is defined according to the method for obtaining the critical liquid level support control angle of the printing paste. Select the corresponding axis line according to the curved structure printing model, and set the border of the border protection model; In the slicing software, the printed model and the border protection model are sliced ​​based on the axis to obtain the corresponding slice file; The slice file is imported into the printing device control software; based on the slice parameters of the current printing layer in the slice file, the multi-axis robotic arm is controlled to move the printing platform to the printing position of the current printing layer, and the posture of the printing platform is adjusted so that the layer to be cured on the printed part is always in a horizontal state.

Images