A light-cured 3D printing system and a light-cured 3D printing method

Abstract

The present application relates to a kind of light-cured 3D printing system and light-cured 3D printing method, belong to by 3D printing, by light-cured additive manufacturing technical field.The transparent release film, build platform, composite coating release mechanism, projection module, position detection unit and control unit are included, and two working units are arranged in the exposure area two sides, and with scanning direction interchange resin coating and resin recycling, linear release function, coating roller can be actively or passively driven, control unit is refreshed digital micromirror device according to the real-time position of projection module, to form sub-pixel superposition with less than single projection pixel X axis displacement;When pixel grid is not zero deflection, form X, Y axis bidirectional sub-pixel sampling, zero deflection only form X axis sub-pixel sampling.The present application also has real-time focusing, uniform speed area exposure and up-down mirror image arrangement function, realize coating, exposure, recycling and local linear release continuous, to expand forming width, reduce release force and improve printing precision and efficiency.

Description

Technical Field

[0001] This invention belongs to the field of additive manufacturing technology through 3D printing and photopolymerization, specifically relating to a photopolymerization 3D printing system and a photopolymerization 3D printing method. Background Technology

[0002] Photopolymer 3D printing typically utilizes ultraviolet light or other curing light capable of initiating the polymerization reaction of photosensitive resin to selectively expose liquid photosensitive resin and form a three-dimensional solid layer by layer. Projection-type photopolymerization equipment employing digital micromirror devices can project an exposure image containing multiple pixels at once, resulting in higher forming efficiency compared to point-by-point scanning methods.

[0003] The print size of existing area array projection equipment is typically limited by both the physical resolution of the digital micromirror device (DMM) and the projection magnification. While increasing the projection magnification can expand the print size while keeping the DMM constant, it also increases the pixel size on the exposure surface and reduces print accuracy. Conversely, decreasing the projection magnification improves accuracy but reduces the print size. Therefore, there is a significant constraint between print size and print accuracy.

[0004] To create large-scale model cross-sections exceeding the width of a single projection, some equipment employs a zoned, paused exposure method. This involves the projection module or build area moving to one zone, stopping to complete the exposure for that zone, and then moving to the next zone. This method requires repeated start-up, stop, and positioning actions. Furthermore, seams, bright / dark bands, or curing boundaries can easily form between zones due to positioning errors, differences in exposure dosage, or resin conditions, making it difficult to obtain a continuous, smooth, large-format cured layer.

[0005] The physical pixels of digital micromirror devices are typically arranged in an orthogonal matrix. When directly using the orthogonal pixel grid to depict curves, diagonal lines, and fine contours, a staircase effect is prone to appear at the model edges. By adding microlens arrays, rotating prisms, or precision micro-displacement mechanisms to implement multiple step exposures, the staircase effect can be reduced to some extent, but this increases the complexity of the optical system, manufacturing costs, and calibration difficulties. Furthermore, frequent mechanical start-stop operations can easily introduce vibration errors.

[0006] In bottom-exposure photopolymerization equipment, the transparent release film is located between the molding interface and the projection module. After the entire layer of exposure is completed, traditional equipment typically drives the build platform to rise along the Z-axis, causing the entire cured area to separate from the transparent release film simultaneously. When the model cross-section is large or solid, a large planar peeling force will be generated between the transparent release film and the cured layer, which may cause model tearing, support structure breakage, build platform step loss, or reduced transparent release film life.

[0007] Furthermore, traditional equipment typically performs resin replenishment, leveling or settling, exposure, and full-layer release sequentially, with waiting times between each process. The transparent release film may also experience slight height fluctuations due to resin pressure, localized release action, installation tension, or temperature changes, causing the actual molded interface to deviate from the fixed focal plane of the projection module. If the projection light source, digital micromirror devices, and projection lens assembly move with the scanning mechanism, the relative vibration between the cooling fan, pump, and optical components may also affect exposure accuracy.

[0008] The projection module also needs to accelerate and decelerate at the beginning and end of the scanning stroke. If the curing light continues to be output according to the exposure sequence of the uniform speed stage in the speed change section, the cumulative exposure energy received per unit area will change with the scanning speed, resulting in over-curing or under-curing at both ends of the model.

[0009] Therefore, there is a need for a photopolymerization 3D printing system and method that can balance large format and high precision, reduce partition splicing marks, reduce release force, improve layer-by-layer molding efficiency, and adaptively control molding interface fluctuations, motion vibrations, and scanning start and stop stages. Summary of the Invention

[0010] This invention provides a photopolymerization 3D printing system and method, aiming to overcome the problems of existing technologies, such as difficulty in balancing printing size and printing accuracy, easy formation of splicing marks due to partial pauses in exposure, easy formation of step effects in orthogonal pixel grids, large release force of large cross-section cured layers, and insufficient stability of focal plane and exposure energy during scanning. It achieves a streamlined process of resin coating, continuous sliding exposure, resin recycling, and local linear release, and obtains a continuous, stable, and large-format forming effect with sub-pixel-level sampling capability.

[0011] The objective of this invention is achieved through the following technical solution: a photopolymerization 3D printing system, comprising: Transparent release film; A platform is constructed above the transparent release film and is capable of moving up and down along the Z-axis; A composite coating release mechanism is capable of reciprocating along a mechanical X-axis in a direction parallel to the transparent release film. The composite coating release mechanism includes a first working unit and a second working unit arranged opposite to each other along the mechanical X-axis. An exposure area is formed between the first working unit and the second working unit. The working unit located in front of the exposure area in the current scanning direction is used to apply liquid photosensitive resin between the transparent release film and the formed entity. The working unit located behind the exposure area in the current scanning direction is used to recover the uncured liquid photosensitive resin and separate the transparent release film from the newly cured layer along a local linear region. The projection module, disposed below the transparent release film, comprises a light source, a digital micromirror device and a projection lens set, and is capable of continuously sliding and scanning along the mechanical X-axis to project an exposure image to the exposure area through the transparent release film; The position detection unit, configured to acquire the real-time position coordinate of the projection module along the mechanical X-axis; and The control unit, connected to the composite coating and release mechanism, the projection module and the position detection unit respectively, is configured to control the composite coating and release mechanism and the projection module to move in the same direction synchronously, and dynamically refresh the slice data of the digital micromirror device according to the real-time position coordinate; Wherein, the projection dimension of a single projected pixel of the digital micromirror device projected onto the exposure surface in the direction of the mechanical X-axis is p_x, the displacement of the projection module along the mechanical X-axis between two adjacent refresh exposures of the digital micromirror device is d, and 0<d<p_x. The displacement d constitutes a sub-pixel step in the direction of the mechanical X-axis, so that the exposure image forms an exposure track with sub-pixel level misalignment superposition along the mechanical X-axis during the continuous sliding scanning process, and the model cross-section of the current layer is cured through time integral superposition of light energy.

[0012] Further, each of the first working unit and the second working unit comprises a resin extrusion and recovery device and a coating roller, and the coating roller adopts an active driving form or a passive driving form; when the active driving form is adopted, the coating roller is in transmission connection with a roller driving member, and the control unit controls the rotation direction and rotation speed of the roller driving member according to the scanning direction and scanning speed of the composite coating and release mechanism; when the passive driving form is adopted, the coating roller is rotatably mounted on the corresponding working unit, and passively rotates in the process of moving with the composite coating and release mechanism and contacting with the transparent release film or the liquid photosensitive resin; the first working unit and the second working unit are configured to selectively perform a resin coating function or a resin recovery and release function according to the scanning direction of the composite coating and release mechanism, so that the functions of the first working unit and the second working unit are interchanged when the composite coating and release mechanism performs reverse scanning.

[0013] Further, the working unit located at the rear side in the current scanning direction comprises a roller assembly acting on the transparent release film, and the roller assembly is configured to recover excess resin in the non-cured area during the movement with the composite coating and release mechanism, and change the local morphology and peeling angle of the transparent release film, so that the separation interface between the transparent release film and the newly cured layer continuously moves along a linear region perpendicular to the scanning direction.

[0014] Further, the position detection unit comprises an encoder or a linear displacement measurement device connected to the linear motion mechanism of the projection module, and the control unit establishes a correspondence between the mechanical displacement and the image refresh position of the digital micromirror device according to the real-time position coordinates, so that adjacent exposure images are continuously connected in the scanning direction.

[0015] Further, the pixel grid projected by the digital micromirror device onto the exposure surface is deflected around the Z axis relative to the mechanical X axis, the absolute value of the deflection angle is a non-zero preset angle θ, and 0°<θ<90°; the projection size of a single projection pixel in the Y axis direction perpendicular to the mechanical X axis is p_y, the deflection of the pixel grid enables two adjacent refresh exposures to form an equivalent interleaved sampling step d_y in the Y axis direction, and d_y=d·tanθ, 0<d_y<p_y, the equivalent interleaved sampling step d_y constitutes a sub-pixel step in the Y axis direction, so that the exposure image forms a sub-pixel level interleaved exposure trajectory in the mechanical X axis direction and the Y axis direction.

[0016] Further, the setting angle of the pixel grid projected by the digital micromirror device onto the exposure surface around the Z axis relative to the mechanical X axis is zero, and the two pixel arrangement directions of the pixel grid are respectively parallel to the mechanical X axis and the Y axis direction perpendicular to the mechanical X axis; only the displacement d along the mechanical X axis is generated between two adjacent refresh exposures, while the equivalent sampling position in the Y axis direction remains unchanged, so that sub-pixel level misalignment superposition exposure is formed only in the mechanical X axis direction in a matrix scanning mode, and no sub-pixel interleaved sampling is formed in the Y axis direction.

[0017] Further, the system further comprises a hardware logic array, in which a coordinate mapping lookup table corresponding to the non-zero preset angle θ is stored, and the hardware logic array is configured to reconstruct the original slice data based on the orthogonal coordinate system into oblique slice data corresponding to the deflected pixel grid according to the coordinate mapping lookup table, and then send the oblique slice data to the digital micromirror device.

[0018] Further, the light source, the digital micromirror device and the projection lens group are fixed on the same rigid base and move integrally with the projection module, and the relative position between the digital micromirror device and the projection lens group remains unchanged during the scanning process; the photocuring 3D printing system further comprises a lightweight liquid cooling end arranged on the projection module and a static heat dissipation base station arranged outside the movement range of the projection module, and the lightweight liquid cooling end is communicated with the static heat dissipation base station through a flexible pipeline, so as to prevent the vibration generated by the pump body, the fan and the radiator in the static heat dissipation base station from being transmitted to the projection module.

[0019] Furthermore, the projection module is also equipped with a molding interface height sensor and a Z-axis focusing actuator. The detection point of the molding interface height sensor is located in front of the projection area in the current scanning direction, and is used to acquire the molding interface height data of the transparent release film facing the liquid photosensitive resin in real time during the scanning process. The control unit associates the molding interface height data with the corresponding target position according to the molding interface height data, the real-time position coordinates, and the distance between the detection point and the projection area along the current scanning direction. When the projection area moves to the target position, the control unit drives the Z-axis focusing actuator to adjust the projection lens group in the Z direction, so that the focal plane of the projection module follows the height change of the molding interface in real time.

[0020] Furthermore, the scanning stroke of the projection module sequentially includes an initial acceleration section, a uniform exposure section, and an end deceleration section along the current scanning direction. The uniform exposure section corresponds to the effective exposure section of the current layer model cross-section, and the initial acceleration section and the end deceleration section are located outside the effective exposure section. The control unit is used to control the projection module to move according to an S-shaped acceleration and deceleration curve in the initial acceleration section and the end deceleration section and to prohibit curing exposure. When the projection module reaches a preset uniform scanning speed and enters the uniform exposure section, curing exposure is started. And curing exposure is stopped before the projection module leaves the uniform exposure section and enters the end deceleration section. The prohibition of curing exposure is achieved by turning off the light source or loading a non-exposure pattern onto the digital micromirror device, so that the light energy received by the exposure surface is lower than the curing threshold of the liquid photosensitive resin.

[0021] Furthermore, the scanning stroke of the projection module along the mechanical X-axis is greater than the single projection width of the projection module in the mechanical X-axis direction. The control unit is used to continuously map the model cross section of the current layer to the exposure window that moves with the projection module according to the real-time position coordinates, so as to form a solidified area that extends continuously along the mechanical X-axis without performing partitioned pause exposure.

[0022] Furthermore, when the projection module is positioned above the transparent release film, the composite coating release mechanism and the construction platform are positioned below the transparent release film, and the Z-axis lifting mechanism for driving the construction platform to rise and fall is positioned below the transparent release film. The projection module is configured to project an exposure image from top to bottom through the transparent release film to the exposure area located on the lower side of the transparent release film, and the composite coating release mechanism is configured to move along the lower side of the transparent release film, so as to coat liquid photosensitive resin between the transparent release film and the formed solid, recover the uncured liquid photosensitive resin, and separate the transparent release film from the newly cured layer along a partial linear region; the Z-axis lifting mechanism is configured to drive the build platform to move downward by one layer thickness in the direction away from the transparent release film after the curing of the current layer is completed.

[0023] The present invention further provides a photocuring 3D printing method, comprising: S1: moving the build platform located above the transparent release film upward by one layer thickness along the Z-axis, so as to form a forming gap for the current layer between the formed solid and the transparent release film; S2: driving the composite coating release mechanism and the projection module located below the transparent release film to move synchronously in the same direction from one side of the current layer to the other side along the mechanical X-axis; S3: coating the liquid photosensitive resin into the forming gap through the working unit located on the front side in the current scanning direction of the composite coating release mechanism; S4: after the liquid photosensitive resin passes through a preset leveling time, making the projection module sweep over the corresponding area, and dynamically refreshing the slice data of the digital micromirror device according to the real-time position coordinates of the projection module, wherein the projection size of a single projection pixel of the digital micromirror device projected onto the exposure surface in the direction of the mechanical X-axis is p_x, the displacement of the projection module along the mechanical X-axis between two adjacent refresh exposures of the digital micromirror device is d, and 0<d<p_x, the displacement d is taken as the sub-pixel step in the direction of the mechanical X-axis, so as to cure the current layer by utilizing the sub-pixel level misalignment superposition exposure track formed along the mechanical X-axis and the time integral superposition of light energy generated by continuous sliding; S5: recovering the uncured liquid photosensitive resin through the working unit located on the rear side in the current scanning direction of the composite coating release mechanism, and continuously separating the transparent release film from the newly cured layer of the current layer along a partial linear region; S6: and after the scanning of the current layer is completed, making the build platform move upward by one layer thickness again, and printing the next layer in the scanning direction opposite to that of the current layer until the three-dimensional model is completed.

[0024] Further, adjacent layers adopt opposite scanning directions, and when the scanning direction is changed, the first working unit and the second working unit of the composite coating release mechanism exchange the resin coating function and the resin recovery and release function, so that the composite coating release mechanism and the projection module directly start the scanning of the next layer from the position where the scanning of the current layer ends.

[0025] Further, the pixel grid projected by the digital micromirror device onto the exposure surface is deflected around the Z axis relative to the mechanical X axis, the absolute value of the deflection angle is a non-zero preset angle θ, and 0°<θ<90°; let the projection size of a single projected pixel in the Y axis direction perpendicular to the mechanical X axis be p_y, the deflection of the pixel grid is used to form an equivalent interleaved sampling step d_y in the Y axis direction for two adjacent refresh exposures, where d_y=d·tanθ and 0<d_y<p_y, the equivalent interleaved sampling step d_y is taken as the sub-pixel step in the Y axis direction, and sub-pixel level interleaved exposure is performed on the current layer according to the sampling positions corresponding to the displacement d and the equivalent interleaved sampling step d_y.

[0026] Further, the set angle of the pixel grid projected by the digital micromirror device onto the exposure surface around the Z axis relative to the mechanical X axis is set to zero, and the two pixel arrangement directions of the pixel grid are respectively parallel to the mechanical X axis and the Y axis direction perpendicular to the mechanical X axis; only the displacement d along the mechanical X axis is generated between two adjacent refresh exposures, while the equivalent sampling position in the Y axis direction remains unchanged, and sub-pixel level misalignment superimposed exposure is performed only in the mechanical X axis direction in a matrix scanning manner, without performing sub-pixel interleaved sampling in the Y axis direction.

[0027] Further, a coordinate mapping lookup table is established according to the non-zero preset angle θ, and the original slice data based on the orthogonal coordinate system is reconstructed in real time by the hardware logic array through the coordinate mapping lookup table into oblique slice data corresponding to the deflected pixel grid.

[0028] Further, during the scanning process of the projection module, the molding interface height sensor with the detection point located in front of the projection area in the current scanning direction is used to acquire the molding interface height data of the side of the transparent release film facing the liquid photosensitive resin in real time; the molding interface height data is associated with the corresponding target position according to the molding interface height data, the real-time position coordinates of the projection module, and the distance between the detection point and the projection area along the current scanning direction; when the projection area moves to the target position, the Z-direction focusing actuator is driven to adjust the projection lens group of the projection module, so that the focal plane of the projection module is kept at the molding interface between the transparent release film and the liquid photosensitive resin in real time.

[0029] Furthermore, the scanning path of the projection module is sequentially divided into an initial acceleration section, a uniform exposure section, and an end deceleration section along the current scanning direction. The uniform exposure section corresponds to the effective exposure section of the current layer model cross-section, and the initial acceleration section and the end deceleration section are located outside the effective exposure section. The projection module moves according to an S-shaped acceleration and deceleration curve in the initial acceleration section and the end deceleration section, and curing exposure is prohibited. Curing exposure is initiated when the projection module reaches a preset uniform scanning speed and enters the uniform exposure section, and curing exposure is stopped before the projection module leaves the uniform exposure section and enters the end deceleration section. Curing exposure is prohibited by turning off the light source of the projection module or by loading a non-exposure pattern onto the digital micromirror device, so that the light energy received by the exposure surface is lower than the curing threshold of the liquid photosensitive resin.

[0030] In summary, compared with the prior art, the present invention has the following advantages: 1. In the solution of the present invention, by utilizing the continuous sliding of the projection module and the exposure window that is dynamically refreshed according to the position, a continuous solidified area exceeding the width of a single projection can be formed, reducing partition pauses and the splicing marks they produce. 2. In the solution of the present invention, by making the mechanical displacement between two adjacent refresh exposures smaller than the projection size of a single projected pixel in the mechanical X-axis direction, the sub-pixel sampling capability in the X-axis direction is obtained without replacing the digital micromirror device. 3. In the solution of the present invention, by deflecting the pixel grid at a non-zero angle, sub-pixel staggered sampling can be further formed in the Y-axis direction; by using the zero-deflection matrix scanning method, sub-pixel misalignment superposition in the X-axis direction can be obtained with a relatively simplified structure and data processing. The two implementation methods can adapt to different precision and processing capability requirements. 4. In the present invention, resin coating, sliding exposure, resin recycling and local linear release are arranged in the same scanning pipeline, which can reduce global static waiting and convert the whole-layer linear release into local linear release that moves with the scan, thereby reducing the instantaneous peel load on the newly cured layer. 5. In the solution of this invention, the first working unit and the second working unit can exchange functions when scanning adjacent layers in reverse, reducing the reset idle stroke; the two forms of active roller and passive roller can adapt to different resin viscosities, feeding methods and equipment cost requirements; 6. In the solution of the present invention, a height sensor located in front of the projection area is used to perform position-related feedforward detection, and real-time focusing is performed when the projection area reaches the target position, which can compensate for local height changes of the transparent release film. 7. In the present invention, the light source, digital micromirror device and projection lens group are fixed on the same rigid base, and the pump body, fan and heat sink are placed outside the range of motion, which helps to maintain the relative position of the optical path during the scanning process and reduce the impact of vibration. 8. In the solution of the present invention, S-shaped acceleration and deceleration are completed outside the effective exposure section, and solidification exposure is prohibited during the speed change phase, which can avoid uneven exposure energy at both ends of the model caused by the change of scanning speed. 9. In the solution of the present invention, the optional upper and lower mirror arrangement allows for the selection of the manufacturing movement mode of the projection module being on top or bottom according to the overall machine space, maintenance method and molding object, thereby expanding the applicability of the system structure layout. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the overall structure of the present invention; Figure 2 This is a schematic diagram of the module structure of the present invention. Figure 3 This is a schematic diagram of the module distribution of the present invention; Figure 4 This is an enlarged view of a partial structure of the present invention; Figure 5 This is a schematic diagram of the deflection structure of the projection module of the present invention; Figure 6 This is a schematic diagram of the pixel grid deflection scheme of the present invention; Figure 7 This is a schematic diagram illustrating the pixel grid deflection effect of the present invention; Figure 8 This is a schematic diagram of the hardware logic array of the present invention; Figure 9 This is a schematic diagram of the mechanical position and time trajectory of the present invention; Figure 10 This is a schematic diagram of the printing process for the 10th layer of the present invention; Figure 11 This is a schematic diagram of the printing workflow for the 11th layer of this invention.

[0032] In the diagram: 1-Transparent release film, 2-Construction platform, 3-Composite coating release mechanism, 4-Projection module; 21-Z-axis lifting mechanism, 22-formed entity, 31-exposure area, 32-resin extrusion and recovery device, 33-coating roller, 41-linear motion mechanism, 42-stationary heat dissipation base station. Detailed Implementation

[0033] The technical solution of the present invention will be further described in detail below through specific embodiments, but the present invention is not limited to these embodiments. Unless otherwise stated, the terms "above," "below," "front," and "rear" in this specification are used to describe the relative positions between the components shown in the accompanying drawings; when the current scanning direction changes, "front" and "rear" change accordingly with the scanning direction. The mechanical X-axis is the scanning direction of the projection module 4 and the composite coating release mechanism 3, the Y-axis is located in the exposure surface and is perpendicular to the mechanical X-axis, and the Z-axis is perpendicular to the exposure surface.

[0034] In this specification, "synchronous movement" includes synchronization where speed and displacement are consistent under ideal conditions, as well as coordinated movement that maintains a predetermined relative position or following distance within a control tolerance range. "Cure exposure" refers to the light energy received by the exposed surface reaching or exceeding the curing threshold of the liquid photosensitive resin; "prohibited cure exposure" includes complete absence of light output and the presence of low-energy light output insufficient to trigger the target curing reaction.

[0035] Example 1

[0036] The projection module is located in a continuous production line forming system. The photopolymerization 3D printing system of this embodiment includes a frame, a transparent release film 1, a build platform 2, a Z-axis lifting mechanism 21, a composite coating release mechanism 3, a projection module 4, a position detection unit, and a control unit. The transparent release film 1 is tensioned and installed in the forming window of the frame, allowing the curing light output from the projection module 4 to pass through. The transparent release film 1 can be made of FEP film, PFA film, or other flexible films with light transmittance and release properties.

[0037] The build platform 2 is positioned above the transparent release film 1 and connected to the Z-axis lifting mechanism 21. The Z-axis lifting mechanism 21 can drive the build platform 2 closer to or further away from the transparent release film 1. At the start of printing, a gap is formed between the forming surface of the build platform 2 and the transparent release film 1, which is adapted to the thickness of the first layer; after each subsequent layer is completed, the build platform 2 moves upward by one layer thickness, forming a new forming gap between the formed entity 22 and the transparent release film 1.

[0038] The composite coating release mechanism 3 is mounted on the upper side of the transparent release film 1 via a transverse guide rail and can reciprocate along the mechanical X-axis. The first working unit and the second working unit are arranged at intervals along the mechanical X-axis, forming an exposure area 31 between them for the projection module 4 to project the exposed image. The first working unit and the second working unit can have essentially the same structure, or they can be installed in a mirror image manner.

[0039] Each working unit is equipped with a resin extrusion recovery device 32 and a coating roller 33. The resin extrusion recovery device 32 is connected to the resin storage unit through a resin fluid channel. The resin fluid channel can be connected to one or more of a feed pump, a recovery pump, a reversible pump, and a reversing valve. When the working unit performs the coating function, the resin extrusion recovery device 32 supplies liquid photosensitive resin quantitatively into the molding gap, and the coating roller 33 spreads the resin along the gap between the transparent release film 1 and the molded entity 22. When the working unit performs the recovery function, the resin extrusion recovery device 32 sucks up or scrapes away excess resin from the non-cured area through the recovery port.

[0040] In the current scanning direction from the first side to the second side, the first working unit is located in front of the exposure area 31 and performs the resin coating function, while the second working unit is located behind the exposure area 31 and performs the resin recovery and release functions. After the scanning direction is reversed, the second working unit is located in front of the exposure area 31 and performs the resin coating function, while the first working unit is located behind the exposure area 31 and performs the resin recovery and release functions. The control unit synchronously switches the operating states of the corresponding fluid channels, pumps, and valves.

[0041] The working unit located behind the current scanning direction also includes a roller assembly. The roller assembly extends along the Y-axis and acts on the transparent release film 1, causing the transparent release film 1 to form a localized bend or a predetermined peel angle near the roller assembly. As the composite coating release mechanism 3 moves along the mechanical X-axis, the separation line between the transparent release film 1 and the newly cured layer extends along the Y-axis and moves continuously along the mechanical X-axis. At any given time, only a localized area near the separation line peels off, thus preventing the entire cured layer from simultaneously detaching.

[0042] The projection module 4 is positioned below the transparent release film 1 and mounted on the linear motion mechanism 41. The projection module 4 includes a light source, a digital micromirror device, and a projection lens group. The curing light emitted by the light source is modulated by the digital micromirror device and then projected onto the exposure area 31 through the transparent release film 1 by the projection lens group. The linear motion mechanism 41 drives the projection module 4 to slide continuously along the mechanical X-axis.

[0043] The control unit controls the composite coating release mechanism 3 and the projection module 4 to move in the same direction at the same nominal scanning speed, and keeps the projection area between the first working unit and the second working unit. Preferably, the projection area maintains a following distance S with respect to the effective coating position of the working unit ahead in the current scanning direction. For uniform scanning, S = V_scan·t, where t is the time required for the resin to complete filling and leveling from the completion of coating. Thus, the resin has sufficient leveling time before reaching the projection area, without needing to wait uniformly after coating the entire layer.

[0044] The position detection unit may include a rotary encoder disposed on the drive motor of the linear motion mechanism 41, a grating ruler, a magnetic grating ruler, or a laser interferometric linear displacement measuring device arranged along the mechanical X-axis. The control unit receives the real-time position coordinate x, and determines the image content that the digital micromirror device should currently load according to the pre-established coordinate zero point, projection magnification, exposure window width and slice data coordinate system.

[0045] The complete model cross-section of the current layer is stored as layer slice data. Since the single projection width of the projection module 4 is smaller than its total scanning stroke, the control unit extracts the data corresponding to the current exposure window from the complete layer slice data according to the real-time position coordinate x. The exposure window moves continuously with the projection module 4, and the previous exposure image and the subsequent exposure image are misaligned and overlapped at a sub-pixel step in the mechanical X-axis direction, without requiring the projection module 4 to stop at each partition position.

[0046] Let the projection size of a single projection pixel in the mechanical X-axis direction be p_x, the constant scanning speed be V_scan, and the effective refresh frequency of the digital micromirror device be f_r. The control unit sets the displacement between two adjacent refresh exposures as d=V_scan / f_r, and makes 0<d<p_x. For example, when d is a fraction of p_x, multiple misaligned samplings can be formed within the width of one physical pixel. The above ratio only illustrates the control relationship, and the actual d is determined according to the optical resolution, resin response time, refresh frequency and target exposure dose.

[0047] The digital micromirror device sequentially loads position-varying exposure images during continuous sliding. The cumulative light energy received by a certain point on the exposure surface can be expressed as the integral of the instantaneous light intensity at this point over time during the passage of the projection window. The control unit sets the light source output, the exposure duty cycle of the digital micromirror device, the scanning speed and the refresh frequency, so that the target area within the model cross-section reaches the curing threshold, and the non-target area is below the curing threshold. The sub-pixel misalignment and time integration of adjacent exposure images jointly reduce the limitation of a single physical pixel boundary on the curing contour.

[0048] The scanning stroke of the projection module 4 reserves a start acceleration distance and an end deceleration distance on both sides of the effective model cross-section. The projection module 4 accelerates from a standstill to a preset constant scanning speed according to an S-shaped acceleration curve in the start acceleration section, at this time the light source is turned off or the digital micromirror device loads an all-black non-exposure pattern. When the projection area enters the constant-speed exposure section corresponding to the model cross-section, the control unit starts curing exposure; before the projection area leaves the effective exposure section, the control unit stops curing exposure, and then the projection module 4 decelerates and stops according to the S-shaped curve in the end deceleration section.

[0049] The above control method ensures that the exposure of the model cross-section entirely occurs in the constant-speed section where the scanning speed is stable. Even if a small amount of stray light exists in the starting acceleration section or the ending deceleration section, the control unit also controls the cumulative energy in this area below the resin curing threshold. The starting acceleration distance and the ending deceleration distance can be determined according to the mass of the projection module 4, the allowable acceleration of the guide rail, the preset constant scanning speed, and the S-curve parameters.

[0050] Embodiment 2

[0051] Non-zero deflection bidirectional sub-pixel scanning of X-axis and Y-axis: Based on Embodiment 1, this embodiment makes the pixel grid formed by the digital micromirror device through the projection lens group deflect a non-zero preset angle θ around the Z axis relative to the mechanical X axis. The deflection can be realized by rotatably installing the entire projection module 4 relative to the linear motion mechanism 41, or can be realized by installing the integral optical assembly composed of the digital micromirror device and the projection lens group at a predetermined angle while maintaining the connection relationship between the rigid base and the linear motion mechanism 41. No matter which method is adopted, the relative position between the digital micromirror device and the projection lens group remains unchanged during the scanning process.

[0052] After the pixel grid is deflected, when the projection module 4 moves a displacement d along the mechanical X axis, two adjacent refresh exposures generate an equivalent interleaved sampling step d_y in the Y-axis direction. According to the coordinate relationship adopted in this embodiment, d_y=d·tanθ. The control parameters satisfy 0<d<p_x and 0<|d_y|<p_y, where p_y is the projection size of a single projected pixel in the Y-axis direction. As a result, adjacent exposure trajectories are not only displaced along the mechanical X axis, but also interleaved along the Y axis.

[0053] When the preset angle θ decreases, the Y-axis interleaving amount corresponding to a single X-axis displacement decreases accordingly; when denser sampling in the Y-axis direction is required, d can be reduced within the refresh frequency range allowed by the digital micromirror device, or an appropriate θ can be selected. The control unit shall consider both the exposure trajectory density and the single exposure energy to avoid the cumulative exposure energy exceeding the target range due to the increase in the number of samplings.

[0054] The hardware logic array may adopt an FPGA or other programmable logic devices. In the calibration phase, the system establishes a coordinate mapping lookup table according to θ, the projection magnification, the pixel size, and the relationship between the mechanical coordinates and the image coordinates. The coordinate mapping lookup table records the correspondence between the sampling addresses of the original orthogonal layer slice data and the output addresses of the deflected pixel grid.

[0055] During printing, the control unit sends the real-time position coordinates and the current layer identifier to the hardware logic array. The hardware logic array determines the range of the current exposure window within the original layer slice based on the real-time position, and then uses a coordinate mapping lookup table to perform address rearrangement, interpolation selection, or bitmap reconstruction, forming oblique slice data corresponding to the deflection pixel grid, which is then sent to the digital micromirror device. Using a lookup table reduces real-time floating-point coordinate calculations during the scanning process.

[0056] For the oblique lines, arcs, and curved surface boundaries of the model, the exposure voxels at different refresh times are staggered to cover the target contour at sub-pixel intervals. After the resin integrates the continuous light energy, the curing boundary is determined by multiple staggered exposures, thereby reducing the stepped edges caused by the orthogonal pixel matrix.

[0057] Example 3

[0058] Zero-deflection X-axis unidirectional sub-pixel matrix scan: The difference between this embodiment and Embodiment 2 is that the pixel grid projected onto the exposure surface by the digital micromirror device has a zero angle relative to the mechanical X-axis around the Z-axis, and the row and column directions of the pixel grid are parallel to the mechanical X-axis and Y-axis, respectively. The projection module 4 still moves a displacement d along the mechanical X-axis between two adjacent refresh exposures, and 0 <d<p_x。

[0059] Since θ=0, the equivalent staggered sampling step size in the Y-axis direction is zero, and adjacent exposed images only produce sub-pixel-level misalignment along the mechanical X-axis. This mode does not increase the sampling position in the Y-axis direction, but it can reduce the sampling step size in the scanning direction and improve the contour continuity in the mechanical X-axis direction through continuous sliding and time integration of optical energy.

[0060] In zero-bias mode, the hardware logic array can continue to handle real-time exposure window extraction, bitmap caching, and digital micromirror device refresh timing control. However, coordinate transformations can employ identity mapping or bypass methods, eliminating the need to generate oblique pixel coordinates. This mode involves relatively less data processing and is suitable for printing tasks where Y-axis physical pixel accuracy is sufficient or where scanning direction accuracy is of greater concern.

[0061] The control unit can select between non-zero deflection mode and zero deflection mode according to the printing task. Both modes share the transparent release film 1, composite coating release mechanism 3, position detection unit, continuous exposure window, and local linear release structure, differing only in the pixel grid mounting angle and the corresponding data mapping method.

[0062] Example 4

[0063] Active coating rollers and passive coating rollers: In the active drive configuration, the coating roller 33 is connected to the roller drive unit via gears, synchronous belts, couplings, or other transmission mechanisms. The roller drive unit can be a servo motor, a stepper motor, or a DC motor with position feedback. The control unit controls the roller rotation direction according to the current scanning direction, ensuring that the tangential movement direction of the coating roller 33 in the resin contact area matches the coating direction, and sets the roller speed according to the scanning speed and target feed rate.

[0064] The active coating roller can adjust the shearing and conveying forces on the resin by changing the ratio of its circumferential speed to its scanning speed. When the resin viscosity is high, the layer thickness is small, or when it is necessary to improve the coating uniformity, the roller's circumferential speed can be slightly higher or slightly lower than the scanning speed to create a controlled squeezing or traction effect. The specific speed ratio is calibrated experimentally, and friction exceeding the allowable range on the transparent release film 1 is avoided.

[0065] In the passive drive configuration, the coating roller 33 is rotatably mounted on the working unit via bearings, without an independent roller drive component. When the composite coating release mechanism 3 moves, the coating roller 33 rotates passively through contact with the transparent release film 1, the liquid photosensitive resin, or adjacent guide surfaces. The passive configuration has a simple structure, fewer moving parts, and reduces the mass of the moving mechanism.

[0066] The first and second working units can both be active, both be passive, or a combination of active and passive modes. The specific drive mechanism of the rollers is not limited as long as the working units can complete resin application on the front side of the current scanning direction and resin recovery and localized linear release on the rear side.

[0067] Example 5

[0068] Real-time focusing and heat dissipation for static / dynamic separation: The light source, digital micromirror device, and projection lens assembly are fixed on the same rigid base. The rigid base is mounted on the movable seat of the linear motion mechanism 41, allowing the entire optical link to move as a whole along the mechanical X-axis. The rigid base can be a one-piece machined metal part, a carbon fiber composite support, or other structures with sufficient rigidity and dimensional stability.

[0069] The lightweight liquid-cooled end is mounted on a rigid base and is thermally connected to the light source, digital micromirror device, or corresponding drive circuit. The circulation pump, fan, and heat sink are centrally located within the stationary heat dissipation base station 42, outside the movement range of the projection module 4. A circulation loop is formed between the lightweight liquid-cooled end and the stationary heat dissipation base station 42 via flexible piping. The flexible piping can be guided by a cable chain, and a flexible buffer section is provided near the projection module 4 to reduce the impact of piping forces on the scanning straightness.

[0070] The focusing assembly includes a forming interface height sensor and a Z-axis focusing actuator. The detection point of the forming interface height sensor is located in front of the projection area along the current scanning direction. Let L be the distance along the mechanical X-axis between the detection point and the reference point of the projection area. When the sensor obtains the forming interface height z_0 at position x_0, the control unit associates this height data with the target position x_0+L. When the projection area reaches the target position, the Z-axis focusing actuator adjusts the projection lens group according to z_0 and the preset focal plane calibration relationship.

[0071] During the uniform scanning phase, height data can also be retrieved with a time delay Δt=L / V_scan; a triggering method based on real-time position coordinates is preferred to avoid focusing position deviation caused by minor speed fluctuations. The control unit can filter, remove outliers, and interpolate the height data, and limit the maximum displacement, speed, and acceleration of the Z-axis focusing actuator.

[0072] For reciprocating scanning, a molding interface height sensor can be placed on each side of the projection area. The control unit activates the sensor on the front according to the current scanning direction, while the sensor on the other side remains in standby mode; alternatively, a single sensor that can be swapped relative to the projection area can be used. Thus, even when adjacent layers use opposite scanning directions, height data for the corresponding area can still be obtained before exposure.

[0073] Example 6

[0074] Photopolymerization 3D printing method under standard setup: This embodiment uses any one of the systems in Embodiments 1 to 5 to perform printing, and includes the following steps.

[0075] S1. Data Preparation. Slice the 3D model to be printed into layers to obtain the original slice data of each layer; according to the selected non-zero deflection mode or zero deflection mode, load the corresponding coordinate mapping parameters, exposure parameters, scanning speed, refresh rate, following distance, and focus calibration parameters.

[0076] S2. Forming a forming gap. For the current layer other than the first layer, the Z-axis lifting mechanism 21 drives the construction platform 2 to move upward by one layer thickness, forming a forming gap for the current layer between the formed entity 22 and the transparent release film 1. The composite coating release mechanism 3 and the projection module 4 are located on the scanning start side of the current layer.

[0077] S3, Initial Acceleration. The control unit initiates the composite coating release mechanism 3 and the projection module 4 in tandem along the current scanning direction. Before the effective exposure section, the projection module 4 accelerates along an S-curve, the light source is turned off or the digital micromirror device loads a non-exposure pattern, and no curing exposure is applied to the resin.

[0078] S4. Coating and Smoothing. The working unit located in front of the current scanning direction extrudes liquid photosensitive resin quantitatively into the forming gap and spreads the resin using the coating roller 33. The projection area and the coating position maintain a following distance S, so that the newly coated area undergoes a filling and smoothing process of not less than a preset time t before exposure.

[0079] S5. Continuous Sliding Exposure. After the projection module 4 reaches the preset uniform scanning speed and enters the uniform exposure section, the control unit starts the solidification exposure. The position detection unit continuously outputs real-time position coordinates; the control unit or hardware logic array triggers an image update once for each displacement d, continuously mapping the current layer model section to the moving exposure window. When the non-zero deflection mode is selected, Y-axis sub-pixel interleaving sampling is formed simultaneously according to d_y=d·tanθ; when the zero deflection mode is selected, only X-axis sub-pixel misalignment superposition is formed.

[0080] S6. Real-time Focusing. Before the projection area reaches the corresponding position, the forming interface height sensor detects the height of the forming interface at that position. The control unit retrieves the corresponding height data according to the distance between the detection point and the projection area and the real-time position coordinates, and drives the Z-axis focusing actuator to make the focal plane follow the forming interface.

[0081] S7. Resin Recovery and Local Release. The working unit located behind the current scanning direction recovers excess resin from the uncured area; the roller assembly moves with the scan and changes the local morphology of the transparent release film 1, causing the linear separation interface between the transparent release film 1 and the newly cured layer to move forward continuously. Coating, exposure, recovery, and release are performed sequentially on the same local area within the same scanning stroke.

[0082] S8. Stop Exposure and End Deceleration. Before the projection area leaves the effective exposure section of the current layer model cross-section, the control unit stops the curing exposure; the projection module 4 and the composite coating release mechanism 3 then enter the end deceleration section and decelerate to a stop according to the S-curve. At this time, the coating, curing, recycling, and release of the current layer have all been completed.

[0083] S9. Reverse printing of the next layer. The Z-axis lifting mechanism 21 drives the build platform 2 to move upward again by one layer thickness. The control unit exchanges the fluid channels and roller working states of the first and second working units, so that the working unit located in front of the next scanning direction performs coating, and the working unit behind performs recycling and release. The composite coating and release mechanism 3 and the projection module 4 start the next layer cycle directly in the opposite direction from the position where the current layer scanning ends.

[0084] Repeat steps S2 to S9 until all layers are printed. For areas not covered by the model boundaries, the digital micromirror device remains unexposed; the recovered liquid photosensitive resin can be returned to the resin supply circuit after filtration and temperature regulation.

[0085] Example 7

[0086] The projection module creates a vertical mirror image of the movement: This embodiment is a mirror image of Embodiment 1 in the vertical direction. The projection module 4 is positioned above the transparent release film 1, while the composite coating release mechanism 3, the construction platform 2, and the Z-axis lifting mechanism 21 are positioned below the transparent release film 1. The projection module 4 moves continuously along the mechanical X-axis along the upper side of the transparent release film 1 and projects the exposure image from top to bottom through the transparent release film 1 onto the exposure area 31 located below it.

[0087] The composite coating release mechanism 3 moves along the underside of the transparent release film 1. The working unit at the front of the current scanning direction directly feeds liquid photosensitive resin into the space between the transparent release film 1 and the pre-formed entity 22 located below it via the resin extrusion and recovery device 32. The coating roller 33 holds and spreads the resin within the forming gap. This feeding method, primarily based on quantitative extrusion and roller constraint, does not rely on the free liquid surface in the open resin tank, thus adapting to coating positions below the transparent release film 1.

[0088] The projection area is exposed from top to bottom after the resin has been smoothed. The working unit behind the current scanning direction recovers the uncured resin and continuously separates the transparent release film 1 from the newly cured layer along a local linear area. The first and second working units can still exchange coating, recovery, and release functions when the scanning direction changes.

[0089] The Z-axis lifting mechanism 21 is located below the transparent release film 1 and drives the build platform 2 to move along the Z-axis. After the current layer is completed, the build platform 2 moves downwards by one layer thickness in a direction away from the transparent release film 1 to form the molding gap for the next layer. Except for the mirror-image changes in the layer-by-layer movement direction of the build platform 2 and the vertical positions of each component, the control methods for position detection, X-axis sub-pixel scanning, non-zero deflection or zero deflection mode, real-time focusing, uniform speed zone exposure, dynamic and static separation heat dissipation, and reverse scanning of adjacent layers can all refer to the aforementioned embodiments.

[0090] In the mirrored arrangement, the molding interface height sensor is positioned on one side of the projection module 4 or at an appropriate location capable of detecting the molding interface below the transparent release film 1. The control unit still associates the height data with the target position according to the positional interval between the detection point and the projection area, and performs focusing when the projection area is reached.

[0091] Example 8

[0092] Control parameter calibration and mode switching: After the equipment is assembled, the projection magnification, pixel sizes p_x and p_y, the directional relationship between the mechanical X-axis and the image coordinate system, the non-zero deflection angle θ, and the mapping relationship between the real-time position coordinates and the exposure window can be determined using a calibration board or standard exposure pattern. The control unit saves the calibration results as the parameter set for the corresponding equipment.

[0093] For each type of liquid photosensitive resin, the curing threshold, target cumulative exposure energy, settling time t, allowable layer thickness, suitable scanning speed, and coating parameters can be determined experimentally. The control unit calculates the refresh frequency f_r based on V_scan and the target d, or determines V_scan based on f_r and the target d when the refresh frequency is limited. In non-zero deflection mode, θ or d_y is also determined based on the target Y-axis sampling step size, and 0 < |d_y| is verified. <p_y。

[0094] The control unit can create mode configuration files for different printing tasks. When bidirectional sub-pixel sampling along both the X and Y axes is required, a non-zero deflection mode is selected and a coordinate mapping lookup table is enabled; when only increasing the sampling density in the scanning direction is needed, a zero deflection mode is selected and identity mapping or bypass transformation is used. Mode switching does not change the pipeline operation principle of the composite coating release mechanism 3.

[0095] During operation, the control unit monitors the status of the position detection unit, the molding interface height sensor, the light source, the roller drive, the fluid supply circuit, and the Z-axis lifting mechanism 21. When the real-time position exceeds the allowable error, the molding interface height change exceeds the focusing stroke, the resin supply is abnormal, or the projection module 4 fails to reach the preset uniform scanning speed, the control unit can maintain a non-exposed state and pause the current layer to avoid forming incorrect curing areas.

[0096] The embodiments of the present invention are not limited to those described above. Without departing from the core concept of the present invention, the material of the transparent release film, the wavelength of the projection light source, the form of the linear motion mechanism, the position detection method, the resin supply circuit, the number of rollers, the form of the focusing actuator, and the hardware configuration of the control unit can all be adjusted according to actual needs. Compatible technical features in the various embodiments can be combined, and these equivalent substitutions or combinations should be understood as falling within the protection scope of the present invention.

[0097] The embodiments of the present invention are not limited to those described above. Without departing from the spirit and scope of the present invention, those skilled in the art can make various changes and improvements to the present invention in form and detail, and these are all considered to fall within the protection scope of the present invention.

Claims

1. A photopolymerization 3D printing system, characterized in that: comprising: a transparent release film; a construction platform, disposed above the transparent release film and capable of moving up and down along the Z axis; a composite coating and release mechanism, capable of reciprocating along the mechanical X axis in a direction parallel to the transparent release film, the composite coating and release mechanism comprising a first working unit and a second working unit disposed oppositely along the mechanical X axis, an exposure area being formed between the first working unit and the second working unit, wherein the working unit located on the front side of the exposure area in the current scanning direction is configured to apply liquid photosensitive resin between the transparent release film and the formed entity, and the working unit located on the rear side of the exposure area in the current scanning direction is configured to recover uncured liquid photosensitive resin and separate the transparent release film from the newly cured layer along a local linear region; a projection module, disposed below the transparent release film, comprising a light source, a digital micromirror device and a projection lens set, and capable of continuously sliding and scanning along the mechanical X axis to project an exposure image to the exposure area through the transparent release film; a position detection unit, configured to acquire real-time position coordinates of the projection module along the mechanical X axis; and a control unit, connected to the composite coating and release mechanism, the projection module and the position detection unit respectively, and configured to control the composite coating and release mechanism and the projection module to move in the same direction synchronously, and dynamically refresh the slice data of the digital micromirror device according to the real-time position coordinates; wherein the projection size of a single projected pixel of the digital micromirror device projected onto the exposure surface in the mechanical X axis direction is p_x, the displacement of the projection module along the mechanical X axis between two adjacent refresh exposures of the digital micromirror device is d, and 0<d<p_x, the displacement d constitutes a sub-pixel step in the mechanical X axis direction, so that the exposure image forms an exposure trajectory with sub-pixel level misalignment and superposition along the mechanical X axis during continuous sliding scanning, and the model cross-section of the current layer is cured by time integral superposition of light energy.

2. The photopolymerization 3D printing system according to claim 1, characterized in that: Each of the first working unit and the second working unit comprises a resin extrusion and recovery device and a coating roller, and the coating roller adopts an active driving form or a passive driving form; when the active driving form is adopted, the coating roller is in transmission connection with a roller driving member, and the control unit controls the rotation direction and rotation speed of the roller driving member according to the scanning direction and scanning speed of the composite coating and release mechanism; when the passive driving form is adopted, the coating roller is rotatably mounted on the corresponding working unit, and passively rotates in the process of moving with the composite coating and release mechanism and contacting the transparent release film or the liquid photosensitive resin; the first working unit and the second working unit are configured to selectively perform the resin coating function or the resin recovery and release function according to the scanning direction of the composite coating and release mechanism, so that the functions of the first working unit and the second working unit are interchanged when the composite coating and release mechanism performs reverse scanning.

3. The photopolymerization 3D printing system according to claim 1, characterized in that: The working unit located on the rear side in the current scanning direction comprises a roller assembly acting on the transparent release film, and the roller assembly is configured to recover excess resin in the non-cured region while moving along with the composite coating release mechanism, and change the local morphology and peeling angle of the transparent release film, so that the separation interface between the transparent release film and the newly cured layer moves continuously along a linear region perpendicular to the scanning direction.

4. The photopolymerization 3D printing system according to claim 1, characterized in that: The position detection unit comprises an encoder or a linear displacement measurement device connected to the linear motion mechanism of the projection module, and the control unit establishes a corresponding relationship between the mechanical displacement and the image refresh position of the digital micromirror device according to the real-time position coordinates, so that adjacent exposure images are continuously connected in the scanning direction.

5. The photopolymerization 3D printing system according to claim 1, characterized in that: The pixel grid projected by the digital micromirror device onto the exposure surface is deflected about the Z axis relative to the mechanical X axis, the absolute value of the deflection angle is a non-zero preset angle θ, and 0°<θ<90°; the projection dimension of a single projected pixel in the Y axis direction perpendicular to the mechanical X axis is p_y, the deflection of the pixel grid enables two adjacent refresh exposures to form an equivalent interleaved sampling step d_y in the Y axis direction, where d_y=d·tanθ and 0<d_y<p_y, and the equivalent interleaved sampling step d_y constitutes a sub-pixel step in the Y axis direction, so that the exposure image forms a sub-pixel level interleaved exposure trajectory in the mechanical X axis direction and the Y axis direction.

6. The photopolymerization 3D printing system according to claim 1, characterized in that: The setting angle of the pixel grid projected by the digital micromirror device onto the exposure surface about the Z axis relative to the mechanical X axis is zero, and two pixel arrangement directions of the pixel grid are parallel to the mechanical X axis and the Y axis direction perpendicular to the mechanical X axis respectively; only the displacement d along the mechanical X axis is generated between two adjacent refresh exposures, while the equivalent sampling position in the Y axis direction remains unchanged, so that sub-pixel level misalignment superimposed exposure is formed only in the mechanical X axis direction in a matrix scanning mode, and no sub-pixel interleaved sampling is formed in the Y axis direction.

7. The photopolymerization 3D printing system according to any one of claims 5 and 6, characterized in that: The system further comprises a hardware logic array, wherein a coordinate mapping lookup table corresponding to the non-zero preset angle θ is stored in the hardware logic array, and the hardware logic array is configured to reconstruct original slice data based on an orthogonal coordinate system into oblique slice data corresponding to the deflected pixel grid according to the coordinate mapping lookup table, and then send the oblique slice data to the digital micromirror device.

8. The photopolymerization 3D printing system according to claim 1, characterized in that: The light source, the digital micromirror device and the projection lens group are fixed on the same rigid base and move integrally with the projection module, and the relative position between the digital micromirror device and the projection lens group remains unchanged during the scanning process; the photocuring 3D printing system further comprises a lightweight liquid cooling end arranged on the projection module and a static heat dissipation base station arranged outside the motion range of the projection module, wherein the lightweight liquid cooling end is communicated with the static heat dissipation base station through a flexible pipeline, so as to prevent the vibration generated by the pump body, the fan and the radiator in the static heat dissipation base station from being transmitted to the projection module.

9. The photopolymerization 3D printing system according to claim 1, characterized in that: The projection module is also equipped with a molding interface height sensor and a Z-axis focusing actuator. The detection point of the molding interface height sensor is located in front of the projection area in the current scanning direction, and is used to acquire the molding interface height data of the transparent release film facing the liquid photosensitive resin in real time during the scanning process. The control unit associates the height data of the molding interface with the corresponding target position based on the height data of the molding interface, the real-time position coordinates, and the distance between the detection point and the projection area along the current scanning direction. When the projection area moves to the target position, the control unit drives the Z-axis focusing actuator to adjust the projection lens group in the Z direction, so that the focal plane of the projection module follows the height change of the molding interface in real time.

10. The photopolymerization 3D printing system according to claim 1, characterized in that: The scanning path of the projection module includes, in sequence, an initial acceleration section, a constant speed exposure section, and an end deceleration section along the current scanning direction. The constant speed exposure section corresponds to the effective exposure section of the current layer model cross section, and the initial acceleration section and the end deceleration section are located outside the effective exposure section. The control unit is used to control the projection module to move according to an S-shaped acceleration / deceleration curve in the initial acceleration section and the final deceleration section and to prohibit curing exposure; to start curing exposure when the projection module reaches a preset uniform scanning speed and enters the uniform exposure section; and to stop curing exposure before the projection module leaves the uniform exposure section and enters the final deceleration section. The prohibition of curing exposure is achieved by turning off the light source or loading a non-exposure pattern onto the digital micromirror device, so that the light energy received by the exposure surface is lower than the curing threshold of the liquid photosensitive resin.

11. The photopolymerization 3D printing system according to claim 1, characterized in that: The scanning stroke of the projection module along the mechanical X-axis is greater than the single projection width of the projection module in the mechanical X-axis direction. The control unit is used to continuously map the model cross section of the current layer to the exposure window that moves with the projection module according to the real-time position coordinates, so as to form a solidified area that extends continuously along the mechanical X-axis without performing partitioned pause exposure.

12. The photopolymerization 3D printing system according to claim 1, characterized in that: When the projection module is positioned above the transparent release film, the composite coating release mechanism and the construction platform are positioned below the transparent release film, and the Z-axis lifting mechanism for driving the construction platform to rise and fall is positioned below the transparent release film. The projection module is used to project an exposure image from top to bottom through the transparent release film onto the exposure area located below the transparent release film. The composite coating release mechanism is used to move along the lower side of the transparent release film to apply liquid photosensitive resin between the transparent release film and the molded entity, recover uncured liquid photosensitive resin, and separate the transparent release film from the newly cured layer along a local linear region. The Z-axis lifting mechanism is used to drive the construction platform to move downward by one layer thickness in a direction away from the transparent release film after the current layer has cured.

13. A photopolymerization 3D printing method using the photopolymerization 3D printing system according to any one of claims 1 to 12, characterized in that, include: S1: Move the build platform located above the transparent release film upward along the Z-axis by one layer thickness to form a forming gap of the current layer between the formed entity and the transparent release film; S2: driving the composite coating and demolding mechanism and the projection module located below the transparent release film to move synchronously in the same direction along the mechanical X-axis from one side of the current layer to the other side; S3: coating liquid photosensitive resin into the forming gap through the working unit located on the front side in the current scanning direction in the composite coating and demolding mechanism; S4: after the liquid photosensitive resin has undergone a preset leveling time, causing the projection module to sweep over the corresponding area, and dynamically refreshing the slice data of the digital micromirror device according to the real-time position coordinates of the projection module, wherein the projection dimension of a single projection pixel projected by the digital micromirror device onto the exposure surface in the direction of the mechanical X-axis is p_x, the displacement of the projection module along the mechanical X-axis between two adjacent refresh exposures of the digital micromirror device is d, and 0<d<p_x, the displacement d is taken as the sub-pixel step in the direction of the mechanical X-axis, so as to solidify the current layer by utilizing the sub-pixel level misalignment superposition exposure track formed along the mechanical X-axis and the time integral superposition of light energy generated by continuous sliding; S5: recovering the uncured liquid photosensitive resin through the working unit located on the rear side in the current scanning direction in the composite coating and demolding mechanism, and continuously separating the transparent release film from the newly solidified layer of the current layer along a local linear region; S6: and after the scanning of the current layer is completed, causing the build platform to move upward by one layer thickness again, and printing the next layer along the scanning direction opposite to that of the current layer, until the three-dimensional model is completed.

14. The photopolymerization 3D printing method according to claim 13, characterized in that: Adopting opposite scanning directions for two adjacent layers, and causing the first working unit and the second working unit of the composite coating and demolding mechanism to exchange the resin coating function and the resin recovery and demolding function when the scanning direction is changed, so that the composite coating and demolding mechanism and the projection module directly start the scanning of the next layer from the position where the scanning of the current layer ends.

Images