A dual-resolution projection photopolymerization 3D printing method

Abstract

The application provides a double-resolution projection light-curing 3D printing method, which utilizes a traditional projection light-curing 3D printing technology to construct a macrostructure pattern through a DMD chip; meanwhile, the like aberration is dispersed by constructing a plurality of groups of parallel light with different incident angles to irradiate the DMD chip, so that the real image and the like aberration which is similar to the real image and directional deviation can be projected. The exposure pattern edge formed by the superposition of the projected real image and the like aberration will form an ordered geometric shape, so as to form a microstructure which is much smaller than the real image size of a single micro-mirror in the DMD chip. When the projection pattern makes the material solidify, the macrostructure (macro-resolution structure) and the microstructure (sub-resolution structure) can be formed at the same time, so that the double-resolution printing is realized.

Description

Technical Field

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

[0002] Surface microstructures are a crucial structural foundation for the functionality of many components, such as the superhydrophobic structure of lotus leaves, the high-absorption structure of geckos, and the ultra-high adsorption inner surface structure of the small intestine. These functional microstructures endow components with special functions such as drag reduction, superhydrophobicity, and light trapping. Their efficient manufacturing has always been a research hotspot. Precise and efficient manufacturing of components with functional surface microstructures will greatly promote the development of fields such as bionics, military, and biomedicine.

[0003] Current methods for manufacturing functional microstructures on surfaces primarily employ a step-by-step process: first, the external shape of the part is machined using conventional methods, and then microstructures are further refined on the surface using techniques such as imprinting, etching, and laser sintering. This approach is suitable for relatively regular external surfaces. However, for parts with complex curved surfaces, especially internal surfaces that are inaccessible to cutting tools and laser beams, step-by-step processes are difficult to implement. Furthermore, in the field of biomanufacturing, bioscaffolds are mainly made of soft and delicate natural or artificial biomaterials, and typically have internal surfaces with cavity structures, making it even more challenging to manufacture functional microstructures on these internal surfaces using step-by-step processes.

[0004] Additive manufacturing (commonly known as 3D printing) provides a powerful tool for manufacturing complex parts. Several high-precision printing methods have been developed that can manufacture surface functional microstructures. Examples include two-photon printing with nanometer-level resolution, and projection-based photopolymerization 3D printing, when combined with microlenses, can also achieve a resolution of 1-2 micrometers, enabling the manufacture of surface functional microstructures.

[0005] Projection-based photopolymer 3D printing technology utilizes a high-resolution digital light processor (DLP) projector to project a cross-sectional pattern of a pre-printed 3D model, thereby curing a liquid photopolymer. This curing process is repeated layer by layer to create a three-dimensional solid. The projection and printing principle involves a DMD chip in the projector receiving the cross-sectional pattern of the model and controlling the opening and closing of micromirrors based on this pattern. In the open state, the micromirror reflects light from the light source; in the closed state, it does not reflect light, thus forming an exposure pattern corresponding to the model's cross-sectional pattern. The projection lens projects this exposure pattern onto a material tank and a printing plane, achieving photopolymerization of the printing material. The material tank contains the photopolymer material, and the height of the printing plane is adjusted to match the layer height. However, since the size and number (number of pixels) of the micro-mirrors of the DMD chip, the core component of a digital light processor projector, are fixed, even when using objective lenses with different magnifications, the pixel size printed is also large when printing on a larger format (high printing efficiency), resulting in reduced printing accuracy. If printing accuracy is to be guaranteed, the printing area will be limited, reducing printing efficiency.

[0006] The fundamental principles of existing additive manufacturing dictate that the size of the basic printing unit is inversely proportional to the processing efficiency. Therefore, exploring integrated additive manufacturing methods that combine printing accuracy and efficiency for the efficient fabrication of three-dimensional surface functional microstructures can not only significantly expand the application scenarios of existing additive manufacturing, but is also key to pushing complex three-dimensional surface functional microstructures to a deeper level of application. Summary of the Invention

[0007] To address the problems existing in the prior art, this invention provides a dual-resolution projection-based photopolymerization 3D printing method. By discretizing aberrations, it enables the simultaneous printing of macroscopic and microscopic structures, breaking through the bottleneck of mutual constraints between printing efficiency and printing accuracy, and realizing the synchronous and integrated precision manufacturing of macroscopic parts and microscopic morphology.

[0008] A dual-resolution projection-based photopolymerization 3D printing method utilizes a DMD chip to construct macroscopic structures, while simultaneously employing multiple sets of quasi-parallel light with different incident angles to irradiate the DMD chip and form discrete aberrations on the imaging surface to construct microscopic structures.

[0009] In the above method, multiple sets of quasi-parallel lights with different incident angles are quasi-parallel lights with discrete deflection angles. Since the light illuminating the DMD chip consists of multiple sets of quasi-parallel lights with different deflection angles (or incident angles), the image formed by a single micromirror on the actual 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 that appear to be translated from the bright spot. The translation distance of these slightly darker bright spots (aberrations) is determined by the deflection angle of the quasi-parallel lights illuminating the DMD chip. The combination of these slightly darker bright spots and bright 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). These complex shapes are projected onto a photocurable material to form a structure with sub-resolution.

[0010] The printing method of this invention utilizes traditional projection-based photopolymerization 3D printing technology to construct a macroscopic structural pattern using a DMD chip. Simultaneously, by constructing multiple sets of quasi-parallel light beams with different incident angles to irradiate the DMD chip, aberrations are discretized, allowing the projection of aberrations in which the real image and the approximate real image are directionally offset. The edges of the exposure pattern formed by the superposition of the projected real image and aberrations will form an ordered geometric shape, thus creating a microstructure much smaller than the size of a single galvanometer image in the DMD chip. When the exposure pattern solidifies the material, both the macroscopic structure (macroscopic resolution structure) and the microstructure (sub-resolution structure) can be formed simultaneously, achieving dual-resolution printing.

[0011] Preferably, multiple sets of quasi-parallel light with different incident angles are obtained by emitting light from a light source array and then collimating it through a collimating lens group.

[0012] In the light source array, the light emitted from each light source is collimated by the collimating lens group to form a set of quasi-parallel beams. Because the distance or position between each light source and the optical axis of the collimating lens group is different, the deflection angle of the light emitted from each light source after collimation is different in space, resulting in multiple sets of non-overlapping beams in angular space. These multiple sets of quasi-parallel beams with different incident angles converge and illuminate the DMD chip. For each micromirror on the DMD chip, the internal distribution of the spatial angle of the reflected light is exactly the same as the spatial angle of the received light. Therefore, the reflected light from each micromirror also has discrete deflection angles. These reflected beams are the incident light of the projection lens. Due to the spherical aberration and coma of the projection lens, beams with different deflection angles cannot converge at the same point in space. These discrete deflection angles will form discrete ghosting on the imaging surface, i.e., discrete aberrations.

[0013] As a further preferred option, the light source array can be an array of any shape (such as square, rectangular, circular, etc.), and its array shape is adapted to the shape of the microstructure to be constructed.

[0014] As a further preferred option, the microstructure can be adjusted by changing the number of light sources in the light source array and / or the size of the light incident angle. This adjustment of the microstructure typically refers to adjusting its size. With other conditions remaining constant, smaller microstructure sizes result in higher printing accuracy, and vice versa.

[0015] Since the formation of microstructures originates from the combined action of light emitted from multiple light sources (light source arrays) and the collimating lens group for refraction (collimation), resulting in quasi-parallel incident light with discrete deflection angles, changing the number of light sources alters the number of discrete deflection angles, thereby changing the number of discrete aberrations and ultimately the size of the microstructure. With other conditions remaining constant, a greater number of light sources results in a smaller microstructure; conversely, a smaller number of light sources results in a larger microstructure.

[0016] Furthermore, by changing the deflection angle of the incident light, the amount of translation of discrete aberrations relative to the real image can be altered, thereby changing the microstructure size.

[0017] As a further optimization, the incident angle of the incident light from the DMD is adjusted by changing the equivalent focal length of the collimating lens group. Since the light emitted from the light source array is collimated by the collimating lens group, forming a certain deflection angle, and the refractive power of the collimating lens group depends on its equivalent focal length, changing the equivalent focal length changes the deflection angle of the incident light. With other conditions remaining constant, increasing the equivalent focal length increases the incident angle of the parallel light illuminating the DMD chip, thereby increasing the size of the microstructure and reducing printing accuracy; conversely, decreasing the equivalent focal length decreases the incident angle of the parallel light, reducing the size of the microstructure and improving printing accuracy.

[0018] The equivalent focal length of a collimating lens group can be adjusted by changing the spacing between the collimating lens groups, or by using liquid lens zoom or other methods. The smaller the spacing between the collimating lens groups, the larger the equivalent focal length; conversely, the larger the spacing, the smaller the equivalent focal length.

[0019] Preferably, the light source array is a virtual light source array or a real light source array.

[0020] As a further preferred option, when the light source array is a real light source array, the microstructure can be adjusted directly by adjusting the number of real light sources.

[0021] As a further preferred embodiment, when the light source array is a virtual light source array, it is constructed by the light emitted from a real light source passing through a microlens array. After the light emitted from the real light source passes through the microlens array, each microlens on the rear surface of the microlens array (the side away from the point light source) forms an equivalent virtual light source (point light source), and the number of microlenses in the microlens array is the number of virtual light sources formed.

[0022] Furthermore, the number of virtual light sources can be adjusted by changing the number of microlenses on the microlens array. Since the virtual light source array is constructed from the microlens array, changing the number of microlenses on the microlens array can change the number of light sources (virtual light sources) in the light source array, thereby adjusting the microstructure.

[0023] As a further optimization, the light emitted from the real light source is first collimated and then passed through a microlens array to construct a virtual light source array. After collimation, the light emitted from the real light source forms quasi-parallel light incident on the microlens array, enabling the microlens array to form a high-quality virtual light source array and improving the precision of the microstructure.

[0024] In a typical microlens array, the microlenses are arranged along a vertical plane, while the micromirrors on the DMD chip are arranged along a plane at a 45° angle to the microlens arrangement plane. Of course, the arrangement of both can be adjusted appropriately according to actual needs.

[0025] Furthermore, the aforementioned real light source can be an active light-emitting unit such as an LED bead or a laser.

[0026] As a preferred embodiment, a dual-resolution projection-based photopolymerization 3D printing method includes the following steps:

[0027] (1) Slice the 3D model to be printed to obtain cross-sectional images of the model arranged in order;

[0028] (2) The light source array emits light, which is collimated by the collimating lens group to obtain multiple sets of parallel light with different incident angles and irradiates the DMD chip to form discrete aberrations and construct the microstructure;

[0029] (3) While constructing the microstructure, take the untraversed layers of the model as the current layer in sequence, transmit the cross-sectional image of the current layer to the DMD chip to construct the macrostructure, and generate an exposure pattern with both micro and macro resolutions.

[0030] (4) The projection lens projects the generated exposure pattern onto the printing plane to complete the photocuring printing of the current layer;

[0031] (5) Repeat steps (3) and (4) until all the cross-sectional images of all layers have been traversed, and complete the dual-resolution photopolymerization 3D printing of the model.

[0032] A dual-resolution projection-based photopolymerization 3D printing system, implementing the aforementioned printing method, is 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) for printing. 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 printing system overcomes the limitations of the hardware itself, producing dimensions with a precision exceeding that of the optical engine, ensuring higher-precision printing even with a large printing area.

[0033] Projection-based photopolymerization 3D printing system, including a light source module;

[0034] The light source module includes a light source array and a collimating lens group disposed between the light source array and the DMD chip;

[0035] The center of the light source array and the optical axis of the collimating lens group are on the same straight line;

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] Preferably, the light source array is composed of real light sources arranged in an array.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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).

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] Preferably, the light source array is equipped with a temperature sensor, a light intensity meter, and a cooling fan.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0071] The dual-resolution projection-based photopolymerization 3D printing method of the present invention adopts the traditional projection-based photopolymerization 3D printing technology. It constructs the macroscopic structure through a DMD chip, and simultaneously constructs multiple sets of parallel light with different incident angles to irradiate the DMD chip to form discrete aberrations and then construct the microstructure, thereby realizing dual-resolution printing and solving the problem of mutual constraint between printing area and printing accuracy. It can also adjust the sub-resolution structure size under certain conditions to improve the printing accuracy under the same printing area. Attached Figure Description

[0072] Figure 1 This is a schematic diagram of an apparatus for implementing the printing method in an embodiment of the present invention;

[0073] 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;

[0074] Figure 2 This is a schematic diagram of the projection result of a conventional projection system.

[0075] 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;

[0076] Figure 4 A schematic diagram illustrating the principle of dual resolution provided in an embodiment of the present invention;

[0077] Figure 5 A schematic diagram illustrating the principle of adjusting the sub-resolution structure size provided in an embodiment of the present invention;

[0078] 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;

[0079] 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 DLP 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.

[0080] Figure 8This is a white light interference image of the sample surface obtained using Example 1;

[0081] Figure 9 This is a white light interference image of the sample surface obtained using Example 2;

[0082] Figure 10 This is a white light interference image of the sample surface obtained using Example 3;

[0083] Figure 11 This is a white light interference image of the sample surface obtained using Example 4. Detailed Implementation

[0084] The technical solution of the present invention will be described in detail below. The following embodiments are implemented based on the technical solution of the present invention, and detailed implementation methods and specific operation processes are given. However, the protection scope of the present invention is not limited to the following embodiments.

[0085] Example

[0086] A dual-resolution projection-based photopolymerization 3D printing method is proposed. It adopts the traditional shadow-based photopolymerization 3D printing method, uses DMD chips to construct macroscopic structures, and simultaneously constructs multiple sets of quasi-parallel light with different incident angles to irradiate the DMD chips and form discrete aberrations on the imaging surface to construct microscopic structures.

[0087] In this process, multiple sets of quasi-parallel light beams with different incident angles are constructed by collimating the light emitted from the light source array and then through the collimating lens group.

[0088] A light source array can be a real light source array arranged in an array, or it can be a virtual light source array constructed by collimating light emitted from a real light source array and then passing it through a microlens array.

[0089] The actual light source is an active light-emitting unit such as an LED bead or a laser.

[0090] The microstructure dimensions can be adjusted by changing the number of light sources in the light source array, or by adjusting the spacing between the collimating lens groups to adjust the equivalent focal length. Alternatively, both methods can be used simultaneously.

[0091] The equivalent focal length of the collimating lens group can be adjusted by adjusting the spacing between the collimating lens groups, or zoom can be achieved by using liquid lens zoom or other methods.

[0092] The arrangement of the microlens array, as well as the number and size of the microlenses, can be adjusted according to actual needs.

[0093] The above-mentioned 3D printing method can be implemented using the following device:

[0094] 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.

[0095] 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.

[0096] 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.

[0097] 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.

[0098] 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.

[0099] 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.

[0100] 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.

[0101] 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.

[0102] 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.

[0103] The projection objective lens 10 uses an objective lens with a magnification of 10.

[0104] 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.

[0105] 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.

[0106] 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.

[0107] 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.

[0108] 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.

[0109] 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.

[0110] 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.

[0111] 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.

[0112] 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.

[0113] The printing method of the above-mentioned projection-based photopolymerization 3D printing system includes:

[0114] 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;

[0115] 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.

[0116] 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;

[0117] 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;

[0118] 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;

[0119] S4. Repeat steps S2 and S4 until the entire model is printed.

[0120] application:

[0121] 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 a 10x projection lens is used. 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.

[0122] Application Example 1

[0123] Using the aforementioned projection-based photopolymerization 3D printing system and method, a 10x projection lens was employed, and a 3x3 microlens array with individual microlenses measuring 1.3mm x 1.3mm was used to form a virtual light source. The actual light source was LED beads. A focusing method was employed to adjust the spacing of the collimating lens group to obtain a front equivalent focal length of 4.64mm and a rear equivalent focal length of 14.22mm for printing, resulting in the following... Figure 8 The sample shown has an average microstructure width of 21.24 micrometers.

[0124] Application Example 2

[0125] Using the aforementioned projection-based photopolymerization 3D 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, achieved by adjusting the spacing of the collimating lens groups, yielded a front equivalent focal length of 10.39mm and a rear equivalent focal length of 15.87mm for printing, resulting in the following image. Figure 9 The sample shown has an average microstructure width of 26.44 micrometers.

[0126] Application Example 3

[0127] Using the aforementioned projection-based photopolymerization 3D printing system and method, a 10x projection lens was employed, with LED beads as the actual light source. A 3x3 microlens array with individual lenses measuring 1.3mm x 1.3mm was used to form a virtual light source. The focusing method, adjusting the spacing of the collimating lens group, yielded a front equivalent focal length of 12.79mm and a rear equivalent focal length of 16.72mm for printing, resulting in the following image. Figure 10 The sample shown has an average microstructure width of 31.66 micrometers.

[0128] Application Example 4

[0129] Using the aforementioned projection-based photopolymerization 3D printing system and method, a 10x projection lens was employed, with LED beads as the actual light source. A 3x3 microlens array with individual lenses measuring 1.3mm x 1.3mm was used to form a virtual light source. The focusing method, adjusting the spacing of the collimating lens group, yielded a front equivalent focal length of 15.16mm and a rear equivalent focal length of 17.60mm for printing, resulting in the following image. Figure 11 The sample shown has an average microstructure width of 36.90 micrometers.

Claims

1. A dual-resolution projection-based photopolymerization 3D printing method, characterized in that, include: A macroscopic structure is constructed using a DMD chip, while a microscopic structure is constructed by illuminating the DMD chip with multiple sets of quasi-parallel light with different incident angles and forming discrete aberrations on the imaging surface. Multiple sets of quasi-parallel beams with different incident angles are obtained by emitting light from a light source array and then collimating them through a collimating lens group; The microstructure can be adjusted by changing the number of light sources in the light source array and / or the size of the incident angle of the light.

2. The dual-resolution projection-based photopolymerization 3D printing method according to claim 1, characterized in that, The incident angle of the incident light rays on the DMD chip is adjusted by adjusting the equivalent focal length of the collimating lens group.

3. The dual-resolution projection-based photopolymerization 3D printing method according to claim 1, characterized in that, The light source array can be a virtual light source array or a real light source array.

4. The dual-resolution projection-based photopolymerization 3D printing method according to claim 3, characterized in that, When the light source array is a virtual light source array, it is constructed by emitting light from a real light source and passing it through a microlens array.

5. The dual-resolution projection-based photopolymerization 3D printing method according to claim 4, characterized in that, After the light from the real light source is emitted, it is first collimated and then passed through a microlens array to construct a virtual light source array.

6. The dual-resolution projection-based photopolymerization 3D printing method according to any one of claims 1 to 5, characterized in that, Includes the following steps: (1) Slice the 3D model to be printed to obtain images of the model cross sections arranged in order; (2) The light source array emits light, which is collimated by the collimating lens group to obtain multiple sets of parallel light with different incident angles and irradiates the DMD chip to form discrete aberrations and construct the microstructure; (3) While constructing the microstructure, take the untraversed layers of the model as the current layer in sequence, transmit the cross-sectional image of the current layer to the DMD chip to construct the macrostructure, and generate an exposure pattern with both micro and macro resolutions. (4) The projection lens projects the generated exposure pattern onto the printing plane to complete the photocuring printing of the current layer; (5) Repeat steps (3) and (4) until all the cross-sectional images of all layers have been traversed, and complete the dual-resolution photopolymerization 3D printing of the model.

Images