Projection light-curing 3D printing system

Abstract

The present application provides a projection type light curing 3D printing system, which sets up a light source array and a collimating lens group to construct multiple groups of deflection angle different quasi parallel light as the incident light of a DMD chip, can simultaneously construct macro resolution and sub-resolution structure, ensures to have higher printing precision while having larger printing area, effectively improves the efficiency of high resolution structure manufacturing; can also adjust the sub-resolution structure size under the condition that other conditions are certain, improves the printing precision under the same printing area. Meanwhile, the printing system of the present application enables the lower precision optical machine to have high precision printing effect to a certain extent, effectively reduces the equipment cost. In addition, the printing system of the present application can adapt to the printing of various materials, including light curing resin, photosensitive resin or light curing hydrogel, etc., has a relatively broad application prospect.

Description

Technical Field

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

[0002] 3D printing, also known as additive manufacturing or rapid prototyping, is characterized by constructing two-dimensional layer structures of specific shapes and stacking them layer by layer to ultimately form a three-dimensional solid. Currently, typical 3D printing processes include: fused deposition modeling (FDM), selective laser sintering (SLS), stereolithography, digital light processing (DLP) printing (projection 3D printing), direct laser sintering (DLS), layered solid manufacturing, polymer jetting, binder jetting, and electron beam fusion.

[0003] Among them, Digital Light Processing (DLP) printing technology uses a high-resolution digital light processor (DLP) projector to project the cross-sectional pattern of a pre-printed 3D model, thereby solidifying a liquid photopolymer and performing photopolymerization layer by layer. It is faster and has higher forming accuracy than similar stereolithography 3D printing technologies. In terms of material properties, details, and surface finish, it can rival injection-molded durable plastic parts. With its superior accuracy and relatively high efficiency, DLP technology is attracting more and more attention and can be seen in applications in industry, medical fields, and other fields.

[0004] A digital light processing (DLP) printing device typically includes a computer control unit, a DLP projector, a printing tank, and a printing platform. The computer control unit manages the entire device, not only slicing the model to be printed and forming a cross-sectional pattern to be transmitted to the DLP projector, but also controlling the height of the printing platform relative to the printing tank and the separation of the printing platform from the printing tank, thus achieving layer-by-layer printing. The DLP projector contains a DMD chip with multiple micromirrors. The DMD chip controls the opening and closing states of all micromirrors based on the cross-sectional image of the model to be printed transmitted from the computer control unit. Open micromirrors reflect light from the light source, while closed micromirrors do not reflect light from the light source. In this combination, the DMD chip can form an exposure image corresponding to the cross-sectional image of the model. The projection lens projects the exposure pattern onto the printing tank and printing platform for photopolymerization printing.

[0005] However, because the size and number of micromirrors (pixels) of the DMD chip, a core component in digital light processor (DLP) projectors, are fixed, even when using objective lenses with different magnifications, ensuring a larger print size results in a larger pixel size, leading to reduced printing accuracy; conversely, ensuring higher printing accuracy results in a smaller pixel size, reducing the print size. Therefore, existing DLP printing devices cannot solve the problem of the trade-off between print size and printing accuracy during the printing process. Summary of the Invention

[0006] To address the problems existing in the prior art, this invention provides a dual-resolution projection-based photopolymerization 3D printing system. Based on Digital Light Processing (DLP) printing technology, it utilizes the micromirror dimensions of the DMD chip in the DLP projector to determine the macroscopic resolution structure (macroscopic structure) to be printed. Simultaneously, by setting up a light source array to control the aberrations of the projection lens itself, it achieves the simultaneous printing of the macroscopic resolution structure and the construction of the sub-resolution structure (microscopic structure), thus enabling dual-resolution printing. This invention's printing system overcomes the limitations of the hardware itself, manufacturing dimensions exceeding the precision of the optical engine, ensuring higher precision printing even with a large printing area.

[0007] Projection-based photopolymerization 3D printing system, including a light source module;

[0008] The light source module includes a light source array and a collimating lens group disposed between the light source array and the DMD chip;

[0009] The center of the light source array and the optical axis of the collimating lens group are on the same straight line;

[0010] The collimating lens group receives the light emitted by the light source array and forms multiple sets of quasi-parallel light with different deflection angles, which then illuminate the DMD chip.

[0011] The dual-resolution projection-type photopolymerization 3D printing system of the present invention has made the above-mentioned improvements to the light source module based on the traditional printing device, realizing the simultaneous printing of macroscopic resolution structures and microscopic resolution structures, while also making the sub-resolution structure size adjustable, thereby improving the printing accuracy under the premise of a certain printing area.

[0012] In addition to the aforementioned light source module, the dual-resolution projection-based photopolymer 3D printing system also includes a base plate, projection device, material tank, printing platform, and computer control components. The light source module, projection device, material tank, and printing platform are all mounted on the base plate. The material tank is used to load the photopolymer material, and the printing platform is used to form and support the printed object. The projection device, material tank, and printing platform are arranged sequentially from bottom to top. The computer control components are used to control the operation of the entire device.

[0013] Preferably, the bottom of the trough is made of a high-transmittance material, which can be one or a combination of high-transmittance glass, FEP, PET, PDMS, and acrylic.

[0014] Preferably, the light source array is composed of real light sources arranged in an array.

[0015] Preferably, the light source array is a virtual light source array constructed by a microlens array after light is emitted from a real light source.

[0016] The real light source is used to generate the light required for photopolymerization printing; the microlens array is used to receive the light generated by the real light source and form multiple virtual light sources arranged in an array.

[0017] The aforementioned real light source can be an active light-emitting unit such as an LED bead or a laser; the emission wavelength of the real light source can be blue light of 400-450nm or ultraviolet light of 200-400nm.

[0018] The arrangement of the microlens array can be in the form of a square, rectangle, parallelogram, circle, etc., and its arrangement is adapted to the shape of the microstructure to be constructed; similarly, the shape of a single microlens in the microlens array can also be in various forms such as a square or rectangle to meet the need for close packing.

[0019] When the parallelism of the light emitted from the real light source is poor, as a further preferred option, an optical element for collimating the optical path is provided between the real light source and the microlens array. The arrangement of this optical element ensures the parallelism of the light incident on the microlens array, thereby enabling the microlens array to form a high-quality virtual light source and improve the accuracy of the sub-resolution structure. This optical element for collimating the optical path can be a lens group or other optical elements such as a Fresnel lens.

[0020] Preferably, the collimating lens group includes a plano-convex lens as a first collimating lens and a biconvex mirror as a second collimating lens, and the optical axes of the two are located on the same straight line.

[0021] The first collimating lens is positioned close to the light source module, with its convex surface facing the light source module; the second collimating lens is positioned between the first collimating lens and the DMD chip.

[0022] In this technical solution, the first collimating lens is used to receive and collimate the light emitted from the light source array; the second collimating lens is used to receive and further collimate the light emitted from the first collimating lens, forming multiple sets of quasi-parallel light with different deflection angles, which illuminate the DMD chip.

[0023] Furthermore, the first collimating lens and the second collimating lens can each be independently made of various forms such as ordinary spherical lenses, aspherical lenses, or Fresnel lenses.

[0024] As a further preferred embodiment, the surfaces of the first collimating lens and the second collimating lens are coated to improve and reduce light energy loss.

[0025] The projection device of the dual-resolution projection-type photopolymerization 3D printing system of the present invention includes a DMD chip, a chip driver, and a projection lens; the DMD chip and its chip driver are connected to a computer control component. The chip driver receives cross-sectional image data of the model from the computer control component (obtained by slicing the model to be printed by the computer control component) and converts it into corresponding drive signals. The DMD chip receives the drive signals and thereby controls the opening and closing states of all micromirrors on it; the open state means that the micromirror can reflect the light received by the DMD chip from the collimating lens group, and the closed state means that the micromirror cannot reflect the light from the collimating lens group, thereby forming an exposure pattern corresponding to the cross-sectional image; the projection lens is used to project the exposure pattern formed by the DMD chip onto the printing plane (the printing plane is the upper surface of the material to be cured).

[0026] The pixels of the exposed pattern are images formed on the printing plane by individual micromirrors on the DMD chip through a projection lens. Since the light illuminating the DMD chip consists of multiple sets of quasi-parallel light with different deflection angles generated by the light source module, the image formed by a single micromirror on the DMD chip will be a bright spot scaled proportionally to the shape of the micromirror itself, along with several slightly darker bright spots (aberrations) around it, which appear to be shifted from the original bright spot. The shift distance of these slightly darker bright spots (aberrations) is determined by the deflection angle of the quasi-parallel light illuminating the DMD chip. The combination of these slightly darker bright spots and bright spots gives the image formed by a single micromirror a more complex and controllable shape, rather than the original simple shape (which was mostly square). These complex shapes are projected onto the photocurable material to form the image, thus enabling the simultaneous construction of macroscopic resolution structures and sub-resolution structures.

[0027] The magnification of the projection lens is not unique and can be adjusted according to the actual structural size and printing area requirements to meet the needs of various applications.

[0028] As a further preferred option, a TIR prism is placed between the projection lens and the DMD chip to accommodate the flip angle of the micromirrors on the DMD chip. This also ensures that the light reflected from the DMD chip can be smoothly incident into the projection lens, without being projected to other positions or returning along the same path.

[0029] As a further optimization, the arrangement of microlenses on the microlens array is adapted to the arrangement of micromirrors on the DMD chip to improve the sensitivity of sub-resolution structure adjustment and achieve a wider range of sub-resolution structure adjustments. Generally, the microlenses are arranged along a vertical plane, while the micromirrors on the DMD chip are arranged along a plane inclined at 45° to the microlens arrangement plane. Of course, the arrangement of both can be adjusted appropriately according to actual needs.

[0030] Preferably, the dual-resolution projection-type photopolymerization 3D printing system further includes an optomechanical motion device for adjusting the spacing of the collimating lens group and the position of the light source array. The collimating lens group and the light source array are respectively mounted on the optomechanical motion device, which is located on the base plate.

[0031] Adjusting the spacing between collimating lens groups changes their equivalent focal length, thus affecting the size of the sub-resolution structure. When the spacing decreases, the equivalent focal length increases, leading to a larger deflection angle of the quasi-parallel light incident on the DMD chip, thereby increasing the sub-resolution structure size. Conversely, increasing the spacing decreases the equivalent focal length, resulting in a smaller deflection angle of the quasi-parallel light incident on the DMD chip, and a smaller sub-resolution structure size. Under otherwise identical conditions, adjusting the equivalent focal length of the collimating lens groups allows for adjustment of the sub-resolution structure size, which in turn allows for adjustment of printing precision as needed.

[0032] As a further preferred embodiment, the optomechanical motion device includes three independently movable axis motion devices, denoted as axis A, B, and C. Each axis is equipped with a corresponding fixture (second collimating lens holder, first collimating lens holder, and light source array holder), used to mount the second collimating lens, the first collimating lens, and the light source array, respectively. The movement of the three axis motion devices can drive the corresponding structures on them to move, thereby adjusting the relative positions of the light source array, the first collimating lens, and the second collimating lens. This adjusts the equivalent focal length produced by the collimating lens group formed by the first and second collimating lenses, and ensures the relative positions of the front focal plane of the collimating lens group formed by the light source array and the first collimating lens, and the rear focal plane of the collimating lens group formed by the projection device and the second collimating lens. This adjusts the deflection angle of the quasi-parallel light illuminating the DMD chip, and thus adjusts the sub-resolution structural dimensions. The three independently movable axis motion devices can be linear modules or other driving devices such as linear motors.

[0033] As a further preferred embodiment, the three independently movable axis motion devices are each equipped with limit switches, which are used to ensure that the light source array, the first collimating lens and the second collimating lens have relatively accurate positions, thereby ensuring the parallelism of the light emitted from the second collimating lens and the uniformity of the light illuminating the DMD chip, ensuring the accuracy of the sub-resolution structure and the optical axis uniformity of the printing area; at the same time, it also makes it easier for operators to zero the equipment, and facilitates use and troubleshooting.

[0034] Preferably, the light source array is equipped with a temperature sensor, a light intensity meter, and a cooling fan.

[0035] The temperature sensor and light intensity meter enable real-time measurement of the operating temperature and light intensity of the light source array. The computer control component adjusts the operating temperature and light intensity based on the measurement results, ensuring stable light intensity and safe system operation during printing. A cooling fan is used to control the temperature of the light source array.

[0036] In addition, a printing motion device is also provided on the base plate. The printing motion device includes a Z-axis motion device and a Y-axis motion device. The Z-axis motion device has an extension perpendicular to its direction of movement. One end of the extension is connected to the Z-axis motion device, and the other end is equipped with a printing platform. The Z-axis motion device is used to adjust the height of the printing platform, thereby changing the height of the cured product, raising the cured part, and realizing the layer-by-layer printing of the product by stacking the cured material. A material tank is installed on the upper end of the Y-axis motion device. One end of the material tank is connected to the upper end of the Y-axis motion device, and the opposite end is installed on the base plate through a support rod. The other end of the material tank is connected to the support rod at a variable angle, so that the Y-axis motion device can drive the other end of the material tank to move up and down, thereby changing the tilt angle of the material tank, so that the cured product can be peeled off from the material tank.

[0037] The Z-axis motion device can be a linear module, or a linear motor or other drive device. The Y-axis motion device can be a linear module, or a linear motor, a through motor or other drive device.

[0038] The computer control component is connected to the printing motion device, the optomechanical motion device, and the light source module, respectively, and is used to control the movement of the corresponding components and adjust the light intensity of the light source array.

[0039] Specifically, the computer control component includes a host computer, an optomechanical control unit, and a printing motion control unit. The host computer is used for human-computer interaction, generating cross-sectional images of the pre-printed 3D model at set intervals along the printing direction, and printing control commands, and coordinating the work of all components. The optomechanical control unit calculates the relative positions of the light source module, the first collimating lens, and the second collimating lens, as well as the light intensity of the light source array in the light source module, based on set sub-resolution structural size (microscopic structural size) parameters. It also controls the optomechanical motion device to drive the light source module, the first collimating lens, and the second collimating lens to the set positions, while simultaneously controlling the light source array to reach the set light intensity. In addition, the optomechanical control unit also transmits the cross-sectional images of the model generated by the host computer to the chip driver, which controls the DMD chip to form an exposure pattern corresponding to the cross-sectional image. The printing motion control unit controls the printing motion device to realize the lifting and lowering of the printing platform and its separation and repositioning from the material tray.

[0040] The host computer can be a personal computer equipped with I / O devices such as a monitor, keyboard, and mouse, a Raspberry Pi with a display screen, an industrial control computer with dedicated I / O devices, or other devices. The host computer has software installed, which is responsible for its various tasks. This software has dual-port communication capabilities, enabling bidirectional communication with both the optomechanical control unit and the printing motion control unit simultaneously. The software can read the STL format file of the pre-printed 3D model and display it in a 3D environment, while providing model control functions including rotation, scaling, and translation, facilitating adjustments to relevant parameters of the pre-printed 3D model by the operator. The software can generate cross-sectional images of the pre-printed 3D model at certain intervals along the printing direction. It obtains the outline of the pre-printed 3D model at different positions along the printing direction based on the triangle vertex information in the STL file, and then obtains the internal and external directions of the pre-printed 3D model and the starting point of the infill based on the triangle normal information in the STL file. Starting from the starting point of the infill, it performs four-connectivity detection to complete the infill of the model, and finally outputs an image based on the infill information. The software can generate print control commands. Based on information such as layer height and exposure time provided by the operator, it can automatically generate a complete set of print control commands according to the syntax and store them in the host computer's memory. The software can monitor the printer's current working status, reflecting the current printed layer height and the current projected exposure pattern, allowing the operator to understand the current work progress.

[0041] The optomechanical control unit can be a microcontroller or other devices. It contains software that supports bidirectional communication with both the host computer and the DMD chip controller, and includes a print control command interpreter to interpret print control commands, drive the corresponding ports, and execute the corresponding commands. In addition, it includes fitting formulas derived from theoretical formulas, simulations, and experimental data to determine the relative positions of the light source module, the first collimating lens, and the second collimating lens, as well as the relationship between the light intensity of the light source in the light source module and the sub-resolution microstructure size parameters. These formulas are used to calculate the positions of the three components and the light intensity of the light source array.

[0042] The printing motion control component can be a microcontroller, a PLC, or other devices. The printing motion control component is equipped with software that supports bidirectional communication with the host computer and carries a printing control instruction interpreter to interpret printing control instructions and drive the corresponding ports (Z-axis motion device and Y-axis motion device) to execute corresponding commands.

[0043] The dual-resolution projection-type photopolymerization 3D printing system of the present invention is applicable to printing a variety of materials, including photopolymerization resin, photosensitive resin, photopolymerization hydrogel, etc.

[0044] The steps of printing using the dual-resolution projection-type photopolymerization 3D printing system of the present invention include:

[0045] S1. The host computer slices the 3D model to be printed according to the set printing layer height to obtain model cross-sectional images arranged in sequence;

[0046] S2. The optomechanical control component drives the optomechanical motion device to control the light source array, the first collimating lens, and the second collimating lens to move to the corresponding positions according to the set microstructure size, and controls the light source array to output the set light intensity; at the same time, the optomechanical control component transmits the cross-sectional image to the projection device in sequence, and the projection device generates the corresponding exposure pattern according to the currently received cross-sectional image and projects it onto the printing platform.

[0047] S3. After the exposure pattern to be generated is exposed to the printing platform for a set time, a curing material of the corresponding thickness is generated on the printing plane (the working surface of the printing platform) to complete the printing of the current layer;

[0048] S4. The printing motion control component drives the printing motion device to control the height of the printing platform to rise, and then controls the material tray to peel off from the printed material; after peeling, the material tray returns to its initial state, and the printing platform descends to a distance of one printing layer height from the bottom of the material tray, ready to print the next layer;

[0049] S5. Repeat steps S2 to S4 until the entire model is printed.

[0050] In step S2 above, light emitted from the light source array passes through a collimating lens group consisting of a first collimating lens and a second collimating lens, forming multiple sets of quasi-parallel light with different deflection angles to illuminate the projection device. The number of sets of quasi-parallel light is the same as the number of light sources in the light source array.

[0051] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0052] The projection-based photopolymerization 3D printing system of this invention utilizes the unavoidable aberrations inherent in projection lenses. By setting up a light source array and collimating lens group, it constructs multiple sets of quasi-parallel light with different deflection angles as the incident light for the DMD chip. This allows for the simultaneous construction of both macroscopic and sub-resolution structures, ensuring high printing accuracy while maintaining a large printing area, effectively improving the efficiency of high-resolution structure manufacturing. Furthermore, under certain conditions, the size of the sub-resolution structure can be adjusted to improve printing accuracy within the same printing area. Simultaneously, this invention enables lower-precision optomechanical systems to achieve high-precision printing results, effectively reducing equipment costs. In addition, this invention's printing system is adaptable to printing on various materials, including photocurable resins, photosensitive resins, and photocurable hydrogels, demonstrating broad application prospects. Attached Figure Description

[0053] Figure 1 This is a schematic diagram of the projection-type photopolymerization 3D printing system according to an embodiment of the present invention;

[0054] In the diagram: 1-Base plate; 2-Support rod; 3-Optical board; 4-Bracket; 5-Stand; 6-Light source; 7-Microlens array; 8-First collimating lens; 9-DMD chip; 10-Projection lens; 11-Mounting frame; 12-Second collimating lens; 13-A-axis motion device; 14-B-axis motion device; 15-C-axis motion device; 16-Light source array frame; 17-First collimating lens frame; 18-Second collimating lens frame; 19-Material trough; 20-Printing platform; 21-Z-axis motion device; 22-Y-axis motion device;

[0055] Figure 2 This is a schematic diagram of the projection result of a conventional projection system;

[0056] Figure 3 This is a schematic diagram of the projection results when the incident light rays are multiple sets of quasi-parallel light rays with different deflection angles;

[0057] Figure 4 A schematic diagram illustrating the principle of dual resolution provided in an embodiment of the present invention;

[0058] Figure 5 A schematic diagram illustrating the principle of adjusting the sub-resolution structure size provided in an embodiment of the present invention;

[0059] Figure 6 This is a schematic diagram of the optical path formation of the dual-resolution printing system provided in an embodiment of the present invention;

[0060] Figure 7 In the figures, (a) shows the surface printed by the dual-resolution projection photopolymerization 3D printing system provided in the embodiment of the present invention; (b) shows the surface printed by the ordinary printing system. As can be seen from the figures, the surface printed by the dual-resolution projection photopolymerization 3D printing system provided in the embodiment of the present invention has longitudinal grooves, while the surface printed by the ordinary printing system is more messy and has no obvious structural features. Detailed Implementation

[0061] To make the objectives, features, and advantages of the present invention more apparent and understandable, the technical solutions of the present invention will be further described in detail below with reference to the accompanying drawings. One embodiment of the present invention is shown in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to make the disclosure of the present invention more thorough and complete.

[0062] Projection-based photopolymerization 3D printing systems, such as Figure 1As shown, the 3D printing system includes a base plate 1 and a light source module, an optomechanical motion device, a projection device, a material tank 19, a printing platform 20, and a printing motion device, as well as a computer control component, all mounted on the base plate 1. Additionally, an optomechanical plate 3 is also mounted on the base plate 1, on which the light source module, the optomechanical motion device, and the projection device are located.

[0063] The light source module includes a light source 6, a microlens array 7, and a collimating lens group consisting of a first collimating lens 8 and a second collimating lens 12. The light source 6 and the microlens array 7 together constitute the light source array. The light source 6, the microlens array 7, the first collimating lens 8, and the second collimating lens 12 are arranged sequentially, and the center of the microlens array 7 is on the same horizontal line as the optical axis of the first collimating lens 8 and the second collimating lens 12.

[0064] Light source 6 generates the light required for printing. In this embodiment, LED beads are used, emitting blue light in the 400-450nm wavelength range. Compared to lasers of the same power, LED beads are less expensive. The LED beads are equipped with temperature sensors and light intensity meters to perform closed-loop control of temperature and light intensity, thereby controlling the heat dissipation and light intensity of light source 6, ensuring stable light intensity and safe system operation during printing. A cooling fan is installed on the outside of light source 6 to control temperature. Microlens array 7 receives the light generated by light source 6 and forms multiple virtual light sources. For the specific optical path formation process, please refer to [reference needed]. Figure 6 The microlens array is arranged in a square pattern, and each microlens is also square in shape to ensure close packing. Since the light source 6 uses LED beads, the parallelism of its emitted light is poor. An optical element (not shown in the figure) is placed between the light source 6 and the microlens array 7 to collimate the incident light of the microlens array 7. The optical element adopts the form of a lens group and is coated on the surface to reduce light loss.

[0065] The first collimating lens 8 is used to receive and collimate the light emitted from the microlens array 7; the second collimating lens 12 is used to receive and further collimate the light emitted from the first collimating lens 8, forming multiple sets of quasi-parallel light with different deflection angles, which illuminate the projection device. For details on the specific light path formation process, please refer to [reference needed]. Figure 6 The first collimating lens 8 is a coated plano-convex lens, and the second collimating lens 12 is a coated biconvex lens.

[0066] The optomechanical motion device includes an A-axis motion device 13, a B-axis motion device 14, a C-axis motion device 15, a light source module frame 16, a first collimating lens frame 17, and a second collimating lens frame 18. The A-axis motion device 13, B-axis motion device 14, and C-axis motion device 15 are respectively mounted on the optomechanical board 3. The light source array (light source 6 and microlens array 7) is mounted on the C-axis motion device 15 via the light source module frame 16; the first collimating lens 8 is mounted on the B-axis motion device 14 via the first collimating lens frame 17; and the second collimating lens 12 is mounted on the A-axis motion device 13 via the second collimating lens frame 18. The A-axis motion device 13, B-axis motion device 14, and C-axis motion device 15 independently control the second collimating lens 12, the first collimating lens frame 17, the light source 6, and the microlens array 7 to move along the direction of the second collimating lens 12, the first collimating lens frame 17, and the light source array (light source 6 and microlens array 7), adjusting their relative positions. This adjusts the equivalent focal length of the collimating lens group composed of the first collimating lens 8 and the second collimating lens 12, and ensures that the center point of the rear prism array of the microlens array 7 and the DMD chip 9 in the projection device are located at the front focal plane and the rear focal plane of the lens group composed of the first collimating lens 8 and the second collimating lens 12, respectively. This adjusts the deflection angle of the quasi-parallel light irradiating the DMD chip 9. When the first collimating lens 8 and the second collimating lens 12 approach each other, the equivalent focal length of the collimating lens group increases, which in turn increases the deflection angle of the quasi-parallel light incident on the DMD chip 9, resulting in an increase in the sub-resolution structure size. When the first collimating lens 8 and the second collimating lens 12 move away from each other, their equivalent focal length decreases, which in turn decreases the deflection angle of the quasi-parallel light incident on the DMD chip 9, resulting in a decrease in the sub-resolution structure size. The A-axis motion device 13, B-axis motion device 14, and C-axis motion device 15 all adopt a lead screw and nut type linear module.

[0067] The A-axis motion device 13, B-axis motion device 14, and C-axis motion device 15 are each equipped with limit switches to ensure that the light source array (light source 6 and microlens array 7), the first collimating lens 8, and the second collimating lens 12 have relatively precise positions. This ensures the parallelism of the light emitted from the second collimating lens 12 and the uniformity of the light illuminating the DMD chip 9, thereby ensuring the accuracy of the sub-resolution structure and the uniformity of the optical axis of the printing area. At the same time, it also facilitates the operator in zeroing the equipment, making it convenient for use and troubleshooting.

[0068] The projection device is mounted on the optical engine board 3 via a mounting bracket 11 on the side of the second collimating lens 12 away from the first collimating lens 8. It includes a DMD chip 9, a chip driver (not shown in the figure), and a projection lens 10. The DMD chip 9, projection lens 10, material tank 19, and printing platform 20 are arranged sequentially from bottom to top.

[0069] In the projection device, the DMD chip 9 and chip driver are connected to a computer control component. The chip driver receives cross-sectional image data of the model from the computer control component and converts it into corresponding drive signals, which are then sent to the DMD chip 9. The DMD chip 9 receives the drive signals and thereby controls the opening and closing states of all micromirrors on the DMD chip 9. The open state means that the micromirror can reflect the light received by the DMD chip 9 from the second collimating lens 12, and the closed state means that the micromirror cannot reflect the light from the second collimating lens 12, thus forming a corresponding exposure pattern. The projection lens 10 is used to project the exposure pattern formed by the DMD chip 9 onto the printing plane (the printing plane is the upper surface of the material to be cured, which is the working surface of the printing platform). The pixels of the exposure pattern are the images formed by the micromirrors on the DMD chip 9 on the printing plane through the projection lens 10. Since the light irradiating the DMD chip 9 is generated by the light source module, it consists of multiple sets of quasi-parallel light with different deflection angles (such as...). Figure 6 As shown), therefore, the image formed by a single micromirror on the actual DMD chip 9 will be a bright spot scaled proportionally to the shape of the micromirror itself, and several surrounding slightly darker bright spots (aberrations) that appear to be produced by a translation of that bright spot, such as... Figure 3 As shown.

[0070] In contrast, the image formed by a single micromirror in a conventional projection printing system is a proportionally scaled bright spot (shown as the image in the figure) and its surrounding continuous rings (shown as aberrations in the figure), such as... Figure 2 As shown. Similar to Figure 3 The translation distance of these slightly darker bright spots (aberrations) is determined by the magnitude of the deflection angle of the quasi-parallel light illuminating the DMD chip 9 (e.g., Figure 5 As shown in the diagram, the combination of slightly darker and brighter spots will give the image formed by a single micromirror a more complex and controllable shape, rather than the original simple shape (which was mostly square). When multiple micromirrors image, the projected exposure pattern will have a more complex shape. These complex shapes are projected onto the photocurable material to form a structure, thus enabling the construction of sub-resolution structures, such as... Figure 4 As shown.

[0071] The projection objective lens 10 uses an objective lens with a magnification of 10.

[0072] The micromirror arrangement surface on the DMD chip 9 is at a 45° angle to the microlens arrangement surface on the microlens array 7. This ensures uniform sub-resolution structure size in all directions while improving the sensitivity of sub-resolution structure adjustment and enabling a wide range of sub-resolution structure size adjustments to meet the high printing accuracy requirements under different printing width requirements.

[0073] A TIR prism is placed between the projection lens 10 and the DMD chip to accommodate the flip angle of the microlenses on the DMD chip in their opening and closing states.

[0074] Material tank 19 is used to load photocurable material, which can be photocurable resin, photosensitive resin, or photocurable hydrogel, etc. The bottom of material tank 19 is made of a high-transmittance material, which can be one or more of high-transmittance glass, FEP, PET, PDMS, and acrylic; printing platform 20 is used to form and support the printed object.

[0075] The printing motion device includes a Z-axis motion device 21 and a Y-axis motion device 22. The moving end of the Z-axis motion device 21 is connected to an extension perpendicular to its moving direction. The end of the extension away from the Z-axis motion device 21 is equipped with a printing platform 20. The Z-axis motion device 21 is used to adjust the height of the printing platform 20, thereby changing the height of the cured product, raising the cured part, and realizing the layering of cured material to complete the product printing. The Z-axis motion device 21 is mounted on the base plate 1 via a bracket 4. One end of the material groove 19 is mounted on the upper end of the Y-axis motion device 22. The other end of the material groove 19 is mounted on the base plate 1 via a support rod 2. The other end of the material groove 19 is variably connected to the support rod 2. The operation of the Y-axis motion device 22 can drive the end of the material groove 19 connected to it to move up and down, thereby changing the tilt angle of the material groove 19, so that the cured product is peeled off from the material groove 19. In this embodiment, the Z-axis motion device 21 adopts a ball screw nut type linear module, and the Y-axis motion device 22 adopts a through motor, which is mounted on the base plate 1 via a stand 5.

[0076] The base plate 1 and the supporting structures of each component are used to construct the structural frame for supporting and fixing the dual-resolution projection-type photopolymerization 3D printing system. The base plate 1 is the foundation of the entire printing system. The support rod 2, the optical engine plate 3, and the bracket 4 are all mounted on the base plate 1. The support rod 2 is used to fix one end of the material trough, the optical engine plate 3 is used to mount the optical engine motion device and the mounting frame 11, the bracket 4 is used to mount the Z-axis motion device, the stand 5 is used to mount the Y-axis motion device, and the mounting frame 11 is used to mount the projection device. The base plate 1, support rod 2, optical engine plate 3, bracket 4, stand 5, and mounting frame 11 together constitute the frame of the printing system.

[0077] The computer control component includes a host computer, an optomechanical control unit, and a printing motion control unit. The host computer is used for human-computer interaction, generating cross-sectional images of the 3D model to be printed at set intervals along the printing direction, and providing control commands, while coordinating the operation of all components. The optomechanical control unit calculates the relative positions of the light source array (light source 6 and microlens array 7), the first collimating lens 8, and the second collimating lens 12, as well as the light intensity of light source 6, based on the set microstructure dimensions. It also controls the light source, microlens array, first collimating lens 8, and second collimating lens 12 to reach the set positions and the light source to reach the set light intensity. In addition, the optomechanical control unit transmits the model cross-sectional images generated by the host computer to the projection device to form the corresponding exposure pattern. The printing motion control unit controls the printing motion device, enabling the lifting and lowering of the printing platform and the peeling and repositioning of the material tray.

[0078] The host computer uses a personal computer equipped with I / O devices such as a monitor, keyboard, and mouse. These are widely available, facilitating system deployment and promotion. The host computer has software installed, which is responsible for its various tasks. The software has dual-port communication capabilities, enabling bidirectional communication with both the optomechanical control unit and the printing motion control unit. The software can read STL format files of pre-printed 3D models and display them in a 3D environment, while providing model control functions such as rotation, scaling, and translation, allowing operators to adjust relevant parameters of the pre-printed 3D model. The software can generate cross-sectional images of the pre-printed 3D model at certain intervals along the printing direction. It obtains the outline of the pre-printed 3D model at different positions along the printing direction based on the triangle vertex information in the STL file, then obtains the internal and external directions of the pre-printed 3D model and the starting point of the infill based on the triangle normal information in the STL file. Finally, it performs four-connectivity detection starting from the infill starting point to complete the infill of the model, and outputs the infill information as an image. The software can generate print control commands. Based on information such as layer height and exposure time provided by the operator, it can automatically generate a complete set of print control commands according to the syntax and store them in the host computer's memory. The software can monitor the printer's current working status, reflecting the current printed layer height and the current projected exposure pattern, allowing the operator to understand the current work progress.

[0079] The optomechanical control unit uses a microcontroller, which is low-cost and small in size, allowing it to be mounted on a frame (base plate 1, support rod 2, optomechanical board 3, bracket 4, stand 5, mounting bracket 11). The optomechanical control unit contains internal software that supports bidirectional communication with the host computer and the DMD chip controller simultaneously. It also carries a print control command interpreter to interpret print control commands and drive the corresponding ports to execute the corresponding commands. In addition, it includes fitting formulas derived from theoretical formulas, simulations, and experimental data, relating the relative positions of the light source array (light source 6, microlens array 7), the first collimating lens 8, and the second collimating lens 12, as well as the light intensity of the light sources in the light source module to the sub-resolution microstructure size parameters. These formulas are used to calculate the position and light intensity of each component.

[0080] The printing motion control component uses a microcontroller, which is low in cost and small in size. It can also be installed on the frame (base plate 1, support rod 2, optical engine base plate 3, bracket 4, stand 5, projection device frame 11). The printing motion control component is equipped with software that supports bidirectional communication with the host computer and carries a printing control instruction interpreter to interpret the printing control instructions and drive the corresponding ports to execute the corresponding commands.

[0081] The printing steps of the dual-resolution projection-type photopolymerization 3D printing system provided in this embodiment include:

[0082] S1. The host computer slices the 3D model to be printed according to the set printing layer height to obtain model cross-sectional images arranged in sequence;

[0083] S2. The optomechanical control component, based on the set microstructure dimensions and positions, drives the optomechanical motion device to control the light source array, the first collimating lens, and the second collimating lens to move to corresponding positions, and controls the light source array to output a set light intensity. The light emitted from the light source array passes through a collimating lens group composed of the first and second collimating lenses, forming multiple sets of quasi-parallel light with different deflection angles to illuminate the projection device. The number of sets of quasi-parallel light is the same as the number of light sources in the light source array.

[0084] Simultaneously, the optomechanical control component transmits the cross-sectional images to the projection device in sequence, and the projection device generates a corresponding exposure pattern based on the currently received cross-sectional images and projects it onto the printing platform;

[0085] S3. After the exposure pattern to be generated is exposed to the printing platform for a set time, a certain thickness of cured material is generated on the printing plane (the working surface of the printing platform) to complete the printing of the current layer;

[0086] S4. The printing motion control component drives the printing motion device to control the height of the printing platform to rise, and then controls the material tray to peel off from the printed material; after peeling, the printing platform rises and falls to a distance of one printing layer height from the bottom of the material tray, and the material tray returns to its initial state, ready to print the next layer;

[0087] S4. Repeat steps S2 and S4 until the entire model is printed.

[0088] application:

[0089] Using the aforementioned printing system and method, a 10x projection lens was employed, with LED beads as the actual light source. A 3x3 microlens array with individual microlenses measuring 1.3mm x 1.3mm was used to form a virtual light source. The focusing method, adjusting the spacing of the collimating lens groups, yielded a front equivalent focal length of 7.84mm and a rear equivalent focal length of 15.03mm for printing, resulting in the following image. Figure 7 The sample shown in (a) has an average microstructure width of 24.09 micrometers. Figure 7 (b) shows the surface printed by a standard DLP printing system, where the projection lens is a 10x lens.

[0090] Depend on Figure 7 As can be seen, the surface printed by the dual-resolution projection photopolymerization 3D printing system provided in this embodiment of the invention has longitudinal grooves and a clear microstructure; while the surface printed by the ordinary printing system is more messy and has no obvious structural features.

[0091] In summary, this embodiment achieves dual-resolution printing by controlling the aberrations of the projection lens itself, simultaneously constructing a sub-resolution structure while printing a macroscopic resolution structure. This ensures higher printing precision while maintaining a large printing area. Furthermore, this embodiment enables lower-precision optomechanics to achieve high-precision printing results to a certain extent, effectively reducing equipment costs. In addition, this embodiment can print on a variety of materials, demonstrating broad application prospects.

[0092] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the appended claims.

Claims

1. A projection-type photopolymerization 3D printing system, including a light source module; Its features are, The light source module includes a light source array and a collimating lens group disposed between the light source array and the DMD chip; The center of the light source array and the optical axis of the collimating lens group are on the same straight line; The collimating lens group receives the light emitted by the light source array and forms multiple sets of quasi-parallel light with different deflection angles, which then illuminate the DMD chip. The collimating lens group includes a plano-convex lens as the first collimating lens and a biconvex mirror as the second collimating lens, and the optical axes of the two are located on the same straight line. The first collimating lens is positioned close to the light source module, with its convex surface facing the light source module; the second collimating lens is positioned between the first collimating lens and the DMD chip.

2. The projection-type photopolymerization 3D printing system according to claim 1, characterized in that, The light source array consists of real light sources arranged in an array.

3. The projection-type photopolymerization 3D printing system according to claim 1, characterized in that, The light source array is a virtual light source array constructed by a microlens array after light is emitted from a real light source.

4. The projection-type photopolymerization 3D printing system according to claim 3, characterized in that, Optical elements for collimating the optical path are placed between the real light source and the microlens array.

5. The projection-type photopolymerization 3D printing system according to claim 1, characterized in that, It also includes an optomechanical motion device for adjusting the spacing of the collimating lens group and the position of the light source array, with the collimating lens group and the light source array respectively mounted on the optomechanical motion device.

6. The projection-type photopolymerization 3D printing system according to claim 1, characterized in that, The light source array is equipped with a temperature sensor, a light intensity meter, and a cooling fan.

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