CN116811233A - Dual-resolution projection type photo-curing 3D printing method - Google Patents

Abstract

The invention provides a dual-resolution projection type photocuring 3D printing method, which utilizes the traditional projection type photocuring 3D printing technology to construct a macrostructure pattern through a DMD chip; meanwhile, by constructing a plurality of groups of parallel light irradiation DMD chips with different incident angles to discretize the aberration, the aberration of the real image and the aberration which is similar to the directional deviation of the real image can be projected. The edge of the exposure pattern formed by overlapping the projected real image and the aberration can form an ordered geometric shape, so that a microstructure which is far smaller than the size of a single micro-vibration mirror real image in the DMD chip is formed, and when the projection pattern solidifies the material, a macroscopic structure (macroscopic resolution structure) and a microstructure (sub-resolution structure) can be formed at the same time, thereby realizing dual-resolution printing.

Description

Dual-resolution projection type photo-curing 3D printing method

Technical Field

The invention belongs to the technical field of additive manufacturing, and particularly relates to a dual-resolution projection type photo-curing 3D printing method.

Background

The surface microstructure is an important structural foundation for the functions of a plurality of components, such as a super-hydrophobic structure on the surface of lotus leaf, a high-suction structure of gecko, an ultrahigh-adsorption inner surface structure of small intestine and the like, and the functional microstructure can enable the components to have special functions of drag reduction, super-hydrophobic, light trapping and the like. The efficient manufacturing of the micro-structural component is a research hot spot all the time, and the accurate and efficient manufacturing of the micro-structural component with the surface function can greatly promote the development of fields such as bionics, military, biomedicine and the like.

The current surface function microstructure is manufactured by a step-by-step process: firstly, processing the appearance of the part by adopting a conventional method, and then further modifying the microstructure on the surface of the component by technologies such as stamping, etching, laser sintering and the like. This approach is suitable for more regular outer surfaces. However, for parts with complex curved surfaces, especially some tools and inner surfaces which cannot be reached by light beams, the step-by-step process is difficult to realize. In addition, in the field of biological manufacturing, biological scaffolds are mainly manufactured from soft and delicate natural or artificial biological materials, and generally have an inner surface with a cavity structure, and it is more difficult to manufacture a functional microstructure of the inner surface using a stepwise process.

Additive manufacturing (commonly known as 3D printing) provides a powerful tool for manufacturing complex parts, and some high-precision printing methods have been developed at present to realize the manufacturing of surface function microstructures. For example, the resolution can reach the resolution of 1-2 microns after the projection type photo-curing 3D printing with nanometer precision is overlaid on the micro lens, and the manufacturing of the surface function microstructure can be realized.

The projection type photocuring 3D printing technology is to utilize a high-resolution digital light processor DLP projector to project a cross-section pattern of a preprinted 3D model, so that a liquid photopolymer is cured, photocuring is carried out layer by layer, and a three-dimensional entity is formed by stacking. The projection and printing principle is that the DMD chip in the projector receives the section pattern of the model and controls the opening and closing of the micro-vibrating mirror on the DMD chip according to the section pattern, wherein the opening state means that the micro-vibrating mirror can reflect the light emitted by the light source, and the closing state means that the micro-vibrating mirror cannot reflect the light emitted by the light source, so that an exposure pattern corresponding to the section pattern of the model is formed. The projection objective projects the exposure pattern to the trough and the printing plane to realize photo-curing printing of the printing material, wherein the trough is filled with the photo-curing material, and the height of the printing plane is adjusted to be the height of the printing layer. However, since the size and the number (the number of pixels) of the micro-oscillating mirrors of the DMD chip, which is a core component in the digital light processor projector, are fixed, even if the objective lens with different multiplying power is used, the size of the printed pixels is larger when the large-format printing (high printing efficiency) is performed, and the printing precision is reduced; if the printing accuracy is to be ensured, the printing format is limited, and the printing efficiency is reduced.

The existing additive manufacturing philosophy dictates that the basic print unit size is inversely proportional to the process efficiency exponentially. Therefore, the method for manufacturing the integrated additive material with printing precision and efficiency is researched around the efficient manufacturing of the three-dimensional surface functional microstructure, so that the application scene of the existing additive material manufacturing can be greatly expanded, and the key of pushing the complex three-dimensional surface functional microstructure to deeper one-step application is also provided.

Disclosure of Invention

In order to solve the problems in the prior art, the invention provides the dual-resolution projection type photocuring 3D printing method, which adopts an aberration discretization mode to realize simultaneous printing of a macroscopic structure and a microscopic structure, breaks through the bottleneck of mutual restriction between printing efficiency and printing precision, and realizes synchronous and integrated accurate manufacturing of macroscopic parts and microscopic morphology.

A dual-resolution projection type photo-curing 3D printing method utilizes a DMD chip to construct a macroscopic structure, and simultaneously adopts multiple groups of quasi-parallel light with different incident angles to irradiate the DMD chip and form discrete aberration on an imaging surface to construct a microscopic structure.

In the above method, the plurality of groups of quasi-parallel light with different incident angles are quasi-parallel light with discrete deflection angles. Because the light irradiated onto the DMD chip is a plurality of groups of quasi-parallel light with different deflection angles (or incidence angles), the image formed by a single micro-vibrating mirror on the actual DMD chip is a bright spot with the shape scaled in equal proportion and a plurality of slightly dark bright spots (aberration) which are formed by the surrounding light spot in a manner of translating, the translation distance of the slightly dark bright spots (aberration) is determined by the size of the deflection angle of the quasi-parallel light irradiated onto the DMD chip, the combination of the slightly dark bright spots and the bright spots can enable the image formed by the single micro-vibrating mirror to have a more complex controllable appearance instead of the original simple shape (the original shape is a square), and the complex shape is projected onto a photo-curing material to form the image, so that a sub-resolution structure can be constructed.

The printing method utilizes the traditional projection type photo-curing 3D printing technology to construct a macroscopic structure pattern through the DMD chip; meanwhile, by constructing a plurality of groups of quasi-parallel light irradiation DMD chips with different incident angles to discretize the aberration, the aberration of the real image and the aberration which is similar to the directional offset of the real image can be projected. The edge of the exposure pattern formed by overlapping the projected real image and the aberration can form an ordered geometric shape, so that a microstructure which is far smaller than the size of a single real image of the vibrating mirror in the DMD chip is formed, and when the exposure pattern solidifies the material, a macroscopic structure (macroscopic resolution structure) and a microstructure (sub-resolution structure) can be formed at the same time, thereby realizing dual-resolution printing.

Preferably, the quasi-parallel light with different incident angles is obtained by collimating the light from the light source array by the collimating lens group.

Each light source in the light source array emits light which can form a group of quasi-parallel light after being collimated by the collimating lens group; because the distance or the position between each light source in the light source array and the optical axis of the collimating lens group is different, the deflection angles generated after the light emitted by each light source in the light source array is collimated by the collimating lens group are different in space, and a plurality of groups of mutually non-overlapping results are formed in the angular space. The method comprises the steps that multiple groups of quasi-parallel light with different incidence angles are converged and irradiated on a DMD chip, for each micro-vibrating mirror on the DMD chip, the internal distribution of the reflected light space angle is identical to the received light space angle, so that the reflected light of each micro-vibrating mirror also has discrete deflection angles, the reflected light is the incident light of a projection objective, due to the existence of spherical aberration and coma aberration of the projection objective, the light with different deflection angles cannot be converged on the same point in space, and the discrete deflection angles can form discrete ghosts, namely discrete aberration, on an imaging surface.

As a further preference, the array of light sources may be any shape (e.g., square, rectangular, circular, etc.) of an array shape that is compatible with the shape of the microstructure to be built.

As a further preference, the microstructure is adjusted by varying the number of light sources in the array of light sources and/or the magnitude of the angle of incidence of the light. Where the adjustment of the microstructure generally refers to the adjustment of the microstructure size, the smaller the microstructure size, the higher the printing accuracy, and vice versa, the lower the printing accuracy, with other conditions unchanged.

Since the microstructure is generated by the refraction (collimation) of the light emitted by the light sources (light source arrays) and the collimating lens group to form quasi-parallel incident light with discrete deflection angles, the number of the discrete deflection angles can be changed by changing the number of the light sources, so that the number of the generated discrete aberrations can be changed, and the size of the microstructure can be changed. Under the condition that other conditions are not changed, the larger the number of the light sources is, the smaller the size of the microstructure is; conversely, the larger the size of the microstructure.

In addition, the amount of translation of the discrete aberrations relative to the real image can be varied by varying the deflection angle of the incident light rays to vary the microstructure size.

As a further preferable aspect, the magnitude of the incident angle of the DMD incident light is adjusted by adjusting the equivalent focal length of the collimator lens group. The light source array generates refraction (collimation) by the collimating lens group to form a certain deflection angle, and the refraction capability of the collimating lens group depends on the equivalent focal length, so that the deflection angle of incident light can be changed by changing the equivalent focal length. Under the condition that other conditions are unchanged, the equivalent focal length is increased, so that the incident angle of parallel light irradiated on the DMD chip is correspondingly increased, the size of the microstructure is further increased, and the printing precision is reduced; and otherwise, the equivalent focal length is reduced, the parallel light incidence angle is reduced, the microstructure size is reduced, and the printing precision is improved.

The equivalent focal length of the collimating lens group can be adjusted by adjusting the interval of the collimating lens group, and zooming can be realized by adopting liquid lens zooming and other modes. Wherein, the smaller the interval of the collimating lens group is, the larger the equivalent focal length is; otherwise, the smaller the equivalent focal length.

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

As a further preferred aspect, when the light source array is a real light source array, the number of real light sources can be directly adjusted to adjust the microstructure.

As a further preferred aspect, when the light source array is a virtual light source array, the virtual light source array is constructed by passing the light emitted by a real light source through a microlens array. After the light emitted by the real light source passes through the micro lens array, each micro lens can form an equivalent virtual light source (point light source) at the back surface (the side far away from the point light source) of the micro lens array, and the number of the micro lenses in the micro lens array is the number of the virtual light sources formed.

Further, the number of virtual light sources is adjusted by changing the number of microlenses on the microlens array. Because the virtual light source array is constructed by the micro lens array, changing the number of micro lenses on the micro lens array can change the number of light sources (virtual light sources) in the light source array, thereby adjusting the microstructure.

As a further preferred aspect, the real light source emits light, and then is collimated and then passes through the micro lens array to construct the virtual light source array. The light emitted by the real light source is collimated to form quasi-parallel light to enter the micro lens array, so that the micro lens array can form a virtual light source array with higher quality, and the precision of a microstructure is improved.

In general, the microlenses in the microlens array are arranged along a vertical plane, and the micro-galvanometers on the DMD chip are arranged along a plane inclined by 45 ° to the microlens arrangement plane. Of course, the arrangement of the two can be properly adjusted according to actual needs.

Furthermore, the real light source may be an active light emitting unit such as an LED lamp bead, a laser, etc.

As a specific preferred aspect, a dual resolution projection type photo-curing 3D printing method includes the steps of:

(1) Slicing the 3D model to be printed to obtain model section pictures which are arranged in sequence;

(2) The light source array emits light, a plurality of groups of parallel light with different incident angles are obtained after the light is collimated by the collimating lens group and irradiated on the DMD chip to form discrete aberration, and a microstructure is constructed;

(3) Taking an un-traversed layer of the model as a current layer in sequence while constructing a microstructure, transmitting a section picture of the current layer to a DMD chip to construct a macroscopic structure, and generating an exposure pattern with microscopic and macroscopic double resolutions;

(4) The projection objective projects the generated exposure pattern onto a printing plane to finish photo-curing printing of the current layer;

(5) Repeating the steps (3) and (4) until the section pictures of all layers are traversed, and completing dual-resolution photo-curing 3D printing of the model.

The dual-resolution projection type photocuring 3D printing system for realizing the printing method is based on a digital light processing DLP printing technology, a macroscopic resolution structure (macroscopic structure) of printing is determined by utilizing the micro-vibrating mirror size of a DMD chip in a DLP projector, meanwhile, the aberration of a projection objective is controlled by setting a light source array to realize printing of the macroscopic resolution structure and simultaneously construct a sub-resolution structure (microscopic structure), so that dual-resolution printing is performed. The printing system breaks through the limitation of hardware, makes the size higher than the precision of the optical machine, and ensures that printing with higher precision is realized on the premise of having a larger printing breadth.

The projection type photo-curing 3D printing system comprises a light source module;

the light source module comprises a light source array and a collimating lens group arranged 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 positioned on the same straight line;

the collimating lens group receives the light emitted by the light source array and forms a plurality of groups of quasi-parallel light with different deflection angles to irradiate the DMD chip.

The dual-resolution projection type photo-curing 3D printing system improves the light source module on the basis of a traditional printing device, realizes simultaneous printing of a macroscopic resolution structure and a microscopic resolution structure, enables the size of a sub-resolution structure to be adjustable, and improves printing precision on the premise of a certain printing breadth.

Besides the light source module, the dual-resolution projection type photo-curing 3D printing system further comprises a bottom plate, a projection device, a trough, a printing platform and a computer control assembly. Wherein, light source module, projection arrangement, silo, print platform all install on the bottom plate. The silo is used for loading light curing material, and print platform is used for forming and bearing the printing and accomplishing the object, and projection arrangement, silo and print platform set gradually from bottom to top. The computer control assembly is used for controlling the whole equipment to run.

Preferably, the bottom of the trough is made of a high light-transmitting material, and the high light-projecting material can be one or a combination of a plurality of high-transmitting glass, FEP, PET, PDMS and acrylic.

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

Preferably, the light source array is a virtual light source array constructed by a microlens array after a real light source emits light.

Wherein the real light source is used for generating light required by photo-curing printing; the micro lens array is used for receiving light generated by the real light source and forming a plurality of virtual light sources arranged in an array.

The real light source can be an active light-emitting unit such as an LED lamp bead and a laser; the emission band of the real light source can be blue light of 400-450 nm or ultraviolet light of 200-400 nm.

The arrangement of the micro-lens array can be in the forms of square, rectangle, parallelogram, circle and the like, and the arrangement form is adapted to the shape of the microstructure to be constructed; likewise, the shapes of the individual microlenses in the microlens array can also be square, rectangular and the like, so as to meet the closely-spaced requirement.

When the parallelism of the light emitted from the real light source is not good, it is further preferable that an optical element for collimating the optical path is provided between the real light source and the microlens array. The arrangement of the optical element can ensure the parallelism of light entering the micro lens array, so that the micro lens array can form a virtual light source with higher quality, and the accuracy of the sub-resolution structure is improved. The optical element for collimating the optical path may be a lens group, or may be another optical element such as a fresnel lens.

Preferably, the collimating lens group includes a plano-convex lens as a first collimating lens and a biconvex lens as a second collimating lens, and the optical axes of the plano-convex lens and the biconvex lens are positioned on the same straight line;

the first collimating lens is arranged close to the light source module, and the convex surface of the first collimating lens faces the light source module; the second collimating lens is arranged between the first collimating lens and the DMD chip.

In the technical scheme, the first collimating lens is used for receiving and collimating the light emitted from the light source array; the second collimating lens is used for receiving and further collimating the light emitted from the first collimating lens to form a plurality of groups of quasi-parallel light with different deflection angles, and the quasi-parallel light irradiates the DMD chip.

Further, the first collimating lens and the second collimating lens may each independently take various forms such as a common spherical mirror, an aspherical mirror, or a fresnel lens.

As a further preferable aspect, the surfaces of the first collimating lens and the second collimating lens are provided with a plating film, so as to improve and reduce the light energy loss.

The projection device of the dual-resolution projection type photo-curing 3D printing system comprises a DMD chip, a chip driver and a projection objective; the DMD chip and its chip driver are connected with computer control component. The chip driver can receive section picture data of a model from the computer control assembly (obtained by slicing the model to be printed by the computer control assembly) and convert the section picture data into corresponding driving signals, and the DMD chip receives the driving signals and controls the opening and closing states of all micro-vibrating mirrors on the DMD chip; wherein, the on state means that the micro-vibrating mirror can reflect the light from the collimating lens group received by the DMD chip, and the off state means that the micro-vibrating mirror can not reflect the light from the collimating lens group, thereby forming an exposure pattern corresponding to the section picture; the projection objective is used for projecting the exposure pattern formed by the DMD chip onto a printing plane (the printing plane is the upper surface of the material to be cured for current printing).

The pixel points of the exposure pattern are images formed on the printing plane by the micro-galvanometers on the DMD chip through the projection objective. Because the light irradiated onto the DMD chip is a plurality of groups of quasi-parallel light with different deflection angles generated by the light source module, the image formed by the single micro-vibrating mirror on the actual DMD chip is a bright spot with the shape scaled in equal proportion and a plurality of slightly dark bright spots (aberration) which are formed by surrounding the bright spot in a manner of translating, the translation distance of the slightly dark bright spots (aberration) is determined by the deflection angle of the quasi-parallel light irradiated onto the DMD chip, the combination of the slightly dark bright spots and the bright spots enables the image formed by the single micro-vibrating mirror to have a more complex controllable appearance instead of the original simple shape (the original shape is a square), and the complex shape is projected onto a photo-curing material to form the image, so that a macroscopic resolution structure and a sub-resolution structure can be constructed simultaneously.

The multiplying power selection of the projection objective is not unique, and can be adjusted according to the actual structural size and the requirements of printing breadth so as to meet the requirements of various application occasions.

As a further preferred option, a TIR prism is arranged between the projection objective and the DMD chip to accommodate the flip angle of the micro-mirrors on the DMD chip in the on-off state. Meanwhile, the light energy reflected by the DMD chip can be ensured to be smoothly incident into the projection objective and not to be projected to other positions or returned in the original path.

As a further preference, the arrangement of the microlenses on the microlens array is adapted to the arrangement of the micro-mirrors on the DMD chip to increase the sensitivity to sub-resolution structure adjustment and to achieve a greater range of sub-resolution structure adjustment. The micro lenses are generally arranged along a vertical plane, and the micro vibrating mirrors on the DMD chip are arranged along a plane inclined by 45 degrees with the arrangement plane of the micro lenses. Of course, the arrangement of the two can be properly adjusted according to actual needs.

Preferably, the dual-resolution projection type photo-curing 3D printing system further comprises an optical machine moving device for adjusting the distance between the collimating lens groups and the position of the light source array, wherein the collimating lens groups and the light source array are respectively arranged on the optical machine moving device, and the optical machine moving device is arranged on the bottom plate.

The equivalent focal length of the collimating lens group can be changed by adjusting the distance between the collimating lens groups, so that the size of the sub-resolution structure size is affected. When the distance between the collimating lens groups is reduced, the equivalent focal length is increased, so that the deflection angle of quasi-parallel light irradiated on the DMD chip is increased, and the sub-resolution structure size is further increased; when the distance between the collimating lens groups is increased, the equivalent focal length is reduced, so that the deflection angle of quasi-parallel light irradiated on the DMD chip is reduced, and the sub-resolution size structure is reduced. Under the condition that other conditions are the same, the adjustment of the sub-resolution structure size can be realized by adjusting the equivalent focal length of the collimating lens group, and then the printing precision can be adjusted according to the requirement.

As a further preferred option, the opto-mechanical movement means comprise three independently movable shaft movement means, denoted A, B and C-axis movement means, respectively. Each shaft is provided with a corresponding fixture (second collimating lens holder, first collimating lens holder, light source array holder) for mounting the second collimating lens, first collimating lens and light source array, respectively. The three axis movement devices respectively move to drive corresponding structures on the three axis movement devices to move so as to adjust the relative positions of the light source array, the first collimating lens and the second collimating lens, thereby adjusting the equivalent focal length generated by the collimating lens group formed by the first collimating lens and the second collimating lens, ensuring the relative positions of the light source array and the front focal plane of the collimating lens group formed by the first collimating lens and the rear focal plane of the collimating lens group formed by the projection device and the second collimating lens, and further adjusting the deflection angle of quasi-parallel light irradiated on the DMD chip. The three shaft movement devices capable of independently moving can be linear modules or other driving devices such as linear motors.

As a further preferred option, limit switches are respectively arranged on the three independently movable shaft movement devices and are respectively used for ensuring that the light source array, the first collimating lens and the second collimating lens have more accurate positions, so that the parallelism of the emergent light of the second collimating lens and the uniformity of the light irradiated on the DMD chip are ensured, and the precision of the sub-resolution structure and the uniformity of the optical axis of the printing breadth are ensured; meanwhile, the equipment is convenient for operators to return to zero, and the equipment is convenient to use and remove faults.

Preferably, the light source array is respectively provided with a temperature sensor, a light intensity meter and a cooling fan.

The temperature sensor and the light intensity meter can be used for measuring the working temperature and the light intensity of the light source array in real time, and the computer control component can be used for adjusting the working temperature and the light intensity according to the measurement result, so that the stability of the illumination intensity and the safety of the system operation in the printing process are ensured. The heat radiation fan is used for controlling the temperature of the light source array.

In addition, a printing movement device is arranged on the bottom plate. The printing motion device comprises a Z-axis motion device and a Y-axis motion device, an extension part perpendicular to the moving direction of the Z-axis motion device is arranged on the Z-axis motion device, one end of the extension part is connected with the Z-axis motion device, and a printing platform is arranged on the other end of the extension part; the Z-axis movement device is used for adjusting the height of the printing platform, so that the height of the cured product is changed, the cured part is lifted, and the layer-by-layer printing of the product is completed by layer superposition of the cured materials. The upper end of the Y-axis movement device is provided with a trough, one end of the trough is connected with the upper end of the Y-axis movement device, the opposite end of the trough is arranged on the bottom plate through a supporting rod, and the other end of the trough is connected with the supporting rod in a variable angle manner, so that the condition that the Y-axis movement device drives the other end of the trough to move up and down, and the inclination angle of the trough is changed, and the solidified product is stripped from the trough.

The Z-axis movement device can be a linear module or other driving devices such as a linear motor. The Y-axis movement device can be a linear module, a linear motor, a penetrating motor and other driving devices.

The computer control component is respectively connected with the printing motion device, the optical machine motion device and the light source module and is used for controlling the movement of corresponding components and adjusting the light intensity of the light source array.

Specifically, the computer control assembly comprises an upper computer, an optical machine control component and a printing motion control component. The upper computer is used for man-machine interaction, generating cross-section pictures with preset intervals along the printing direction of the pre-printing 3D model and printing control instructions, and coordinating the work of all the components. The optical machine control component is used for calculating the relative positions of the light source module, the first collimating lens and the second collimating lens and the light intensity of the light source array in the light source module according to the set parameters of the sub-resolution structure size (microstructure size), and controlling the optical machine movement device to drive the light source module, the first collimating lens and the second collimating lens to move to the set positions and simultaneously controlling the light source array to reach the set light intensity. In addition, the optical machine control component is also used for transmitting the section picture of the model generated by the upper computer to the chip driver, and the chip driver controls the DMD chip to form an exposure pattern corresponding to the section picture. The printing motion control component is used for controlling the printing motion device to realize lifting of the printing platform and stripping and recovery of the printing platform and the trough.

The upper computer can be a personal computer with IO devices such as a display, a keyboard and a mouse, can be a raspberry pie with a display screen, and can also be an industrial personal computer or other devices carrying special IO devices. The upper computer is provided with software, and the software is particularly responsible for various tasks of the upper computer. The software has a double-port communication function and can simultaneously perform bidirectional communication with the optical machine control component and the printing motion control component. The software can read in the STL format file of the pre-printed 3D model and display the STL format file in a three-dimensional environment, and simultaneously provides model control functions including rotation, scaling, translation and the like, so that an operator can conveniently adjust relevant parameters of the pre-printed 3D model. The software can generate cross-section pictures with certain intervals of the pre-printed 3D model along the printing direction, the outline of the pre-printed 3D model at different positions along the printing direction is obtained according to triangle vertex information in the STL file, the filling starting point of the inside and outside directions of the pre-printed 3D model and the inside of the model is obtained according to triangle normal vector information in the STL file, four-communication detection is carried out according to the filling starting point of the inside of the model, filling of the inside of the model is completed, and finally the pictures are output according to the filling information. The software can generate a printing control instruction, and based on the related information such as the layer height, the exposure time and the like given by an operator, a whole set of printing control instruction can be automatically generated according to grammar and stored in the memory of the upper computer. The software can monitor the current working condition of the printer, reflect the currently printed layer height and the currently projected exposure pattern, and facilitate operators to know the current working progress.

The optical machine control component can be a single chip microcomputer or other equipment, is internally provided with software, supports bidirectional communication with the upper computer and the DMD chip controller at the same time, is provided with a printing control instruction interpreter, interprets printing control instructions, drives corresponding ports and executes corresponding commands. Besides, a fitting formula between the relative positions of the light source module, the first collimating lens and the second collimating lens and the light intensity of the light source in the light source module and the sub-resolution microstructure size parameter, which are obtained by a theoretical formula, simulation and experimental data, is provided for calculating the positions of the three and the light intensity of the light source array.

The printing motion control component can be a singlechip or a PLC or other equipment, is internally provided with software, supports two-way communication with the upper computer, is provided with a printing control instruction interpreter, interprets printing control instructions and drives corresponding ports (a Z-axis motion device and a Y-axis motion device) to execute corresponding commands.

The dual-resolution projection type photo-curing 3D printing system can be suitable for printing of various materials, including photo-curing resin, photosensitive resin, photo-curing hydrogel and the like.

Compared with the prior art, the invention has the beneficial effects that:

according to the dual-resolution projection type photo-curing 3D printing method, a traditional projection type photo-curing 3D printing technology is adopted, a macroscopic structure is built through the DMD chip, meanwhile, a plurality of groups of parallel light irradiation DMD chips with different incident angles are built to form discrete aberration, and then a microstructure is built, so that dual-resolution printing is realized, and the problem of mutual elbow pulling between a printing breadth and printing precision is solved; the sub-resolution structure size can be adjusted under the condition of certain other conditions, and the printing precision under the same printing breadth is improved.

Drawings

FIG. 1 is a schematic diagram of a device for implementing a printing method according to an embodiment of the present invention;

in the figure: 1-a bottom plate; 2-a support rod; 3-an optical board; 4-a bracket; 5-standing seats; 6-a light source; 7-a microlens array; 8-a first collimating lens; 9-a DMD chip; 10-projection objective; 11-mounting rack; 12-a second collimating lens; 13-A axis movement means; a 14-B axis motion device; 15-C axis movement device; 16-a light source array frame; 17-a first collimating lens holder; 18-a second collimating lens holder; 19-a trough; 20-a printing platform; 21-Z axis movement device; 22-Y axis movement device;

FIG. 2 is a schematic view of a projection result of a conventional projection system;

FIG. 3 is a schematic view of the projection results in the case that the incident light is a plurality of sets of quasi-parallel light with different deflection angles;

FIG. 4 is a schematic diagram of a dual resolution principle provided by an embodiment of the present invention;

FIG. 5 is a schematic diagram of adjusting the size of a sub-resolution structure according to an embodiment of the present invention;

FIG. 6 is a schematic diagram illustrating the formation of a dual resolution printing system optical path according to an embodiment of the present invention;

in fig. 7, (a) is a surface printed by a dual resolution projection type photo-curing 3D printing system according to an embodiment of the present invention; (b) drawing is a surface printed by a general DLP printing system; as can be seen from the figure, the surface printed by the dual-resolution projection type photo-curing 3D printing system provided by the embodiment of the invention has longitudinal grooves, while the surface printed by the common printing system is disordered and has no obvious structural characteristics;

FIG. 8 is a white light interference image of the sample surface obtained in application example 1;

FIG. 9 is a white light interference image of the surface of the sample obtained in application example 2;

FIG. 10 is a white light interference image of the surface of the sample obtained in application example 3;

FIG. 11 is a white light interference image of the surface of the sample obtained in application example 4.

Detailed Description

The following examples are given to illustrate the technical scheme of the present invention, and the following detailed embodiments and specific operation procedures are given on the premise of the technical scheme of the present invention, but the scope of the present invention is not limited to the following examples.

Examples

A dual-resolution projection type photo-curing 3D printing method is adopted, a traditional shadow type photo-curing 3D printing method is adopted, a macroscopic structure is built by utilizing a DMD chip, multiple groups of quasi-parallel light with different incidence angles are built at the same time to irradiate the DMD chip, and discrete aberration is formed on an imaging surface to build a microstructure.

The quasi-parallel light with different incident angles is obtained by collimating light from the light source array through the collimating lens group.

The light source array can be a real light source array arranged in an array manner, or can be a virtual light source array which is formed by collimating light listed by one real light source array and then constructing the light source array by a micro lens array.

The real light source is an active light-emitting unit such as an LED lamp bead or a laser.

The microstructure size can be adjusted by adjusting the number of light sources in the light source array, and the microstructure size can also be adjusted by adjusting the equivalent focal length by adjusting the distance between the collimating lens groups. Of course, the two modes can be simultaneously adjusted together.

The equivalent focal length of the collimating lens group can be adjusted by adjusting the interval of the collimating lens group, and zooming can be realized by adopting liquid lens zooming and other modes.

The arrangement mode of the micro lens array and the number and the size of the micro lenses can be adjusted according to actual needs.

The 3D printing method can be implemented by the following devices:

as shown in fig. 1, the projection type photo-curing 3D printing system comprises a base plate 1, a light source module, a light machine movement device, a projection device, a trough 19, a printing platform 20, a printing movement device and a computer control component, wherein the light source module, the light machine movement device, the projection device, the trough 19, the printing platform 20 and the printing movement device are arranged on the base plate 1. In addition, the bottom plate 1 is further provided with an optical machine board 3, wherein the light source module, the optical machine movement device and the projection device are arranged on the optical machine board 3.

The light source module includes a light source 6, a microlens array 7, and a collimator lens group composed of a first collimator lens 8 and a second collimator lens 12. The light source 6 and the microlens array 7 together constitute a light source array. The light source 6, the micro lens array 7, the first collimating lens 8 and the second collimating lens 12 are sequentially arranged, and the center of the micro lens array 7 and the optical axes of the first collimating lens 8 and the second collimating lens 12 are positioned on the same horizontal line.

The light source 6 is used to generate light required for printing, and in this embodiment, LED beads are used, which emit blue light with a wavelength band of 400-450 nm. Compared with the same-power laser and the like, the LED lamp bead has lower cost, is provided with a temperature sensor and a light intensity meter, and performs closed-loop control on the temperature and the light intensity so as to realize the control on the heat dissipation of the light source 6 and the light intensity emitted by the light source 6 and ensure the stability of illumination intensity and the safety of system operation in the printing process. A cooling fan is arranged outside the light source 6 for controlling the temperature. The microlens array 7 is used for receiving the light generated by the light source 6 and forming a plurality of virtual light sources, and the specific light path forming process can be seen in fig. 6. The arrangement of the micro lens array adopts square arrangement, and meanwhile, each micro lens is square in shape, so that close arrangement is ensured. Since the light source 6 adopts LED beads, the light-emitting parallelism is poor, and an optical element (not shown in the figure) is arranged between the light source 6 and the microlens array 7, and is used for collimating the incident light of the microlens array 7, the optical element adopts a lens group form, and the surface of the optical element is coated with a film to reduce the light loss.

A first collimating lens 8 for receiving and collimating light exiting the microlens array 7; the second collimating lens 12 is configured to receive and further collimate the light emitted from the first collimating lens 8 to form a plurality of groups of quasi-parallel light beams with different deflection angles, and irradiate the projection device, and a specific optical path forming process can be seen in fig. 6, where the first collimating lens 8 uses a coated plano-convex lens, and the second collimating lens 12 uses a coated biconvex lens.

The optical machine moving device comprises an A-axis moving device 13, a B-axis moving device 14, a C-axis moving device 15, a light source module frame 16, a first collimating lens frame 17 and a second collimating lens frame 18, and the A-axis moving device 13, the B-axis moving device 14 and the C-axis moving device 15 are respectively arranged on the optical machine board 3. The light source arrays (the light source 6 and the microlens array 7) are mounted on the C-axis movement device 15 through the light source module frame 16; the first collimating lens 8 is mounted on the B-axis moving device 14 through a first collimating lens holder 17; the second collimator lens 12 is mounted to the a-axis moving device 13 through a second collimator lens holder 18. The a-axis moving device 13, the B-axis moving device 14 and the C-axis moving device 15 respectively and independently control the second collimating lens 12, the first collimating lens holder 17, the light source 6 and the micro lens array 7 to move along the arrangement direction of the second collimating lens 12, the first collimating lens holder 17 and the light source array (the light source 6 and the micro lens array 7), and adjust the relative positions of the two to adjust the equivalent focal length of the collimating lens group formed by the first collimating lens 8 and the second collimating lens 12, and ensure that the center point of the rear prism array of the micro lens array 7 and the DMD chip 9 in the projection device are respectively positioned at the front focal plane and the rear focal plane of the lens group formed by the first collimating lens 8 and the second collimating lens 12, thereby adjusting the deflection angle of the quasi-parallel light irradiated on the DMD chip 9. When the first collimating lens 8 and the second collimating lens 12 are close to each other, the equivalent focal length of the collimating lens group is increased, so that the deflection angle of quasi-parallel light irradiated on the DMD chip 9 is correspondingly increased, and the sub-resolution structure size is increased; when the first collimating lens 8 and the second collimating lens 12 are far away from each other, the equivalent focal length thereof will decrease, so that the deflection angle of the quasi-parallel light irradiated onto the DMD chip 9 will also decrease accordingly, and the sub-resolution structure size will decrease. The A-axis movement device 13, the B-axis movement device 14 and the C-axis movement device 15 are all screw-nut type linear modules.

The A-axis movement device 13, the B-axis movement device 14 and the C-axis movement device 15 are respectively provided with limit switches, and are used for ensuring that a light source array (a light source 6 and a micro lens array 7), a first collimating lens 8 and a second collimating lens 12 have more accurate positions, so that the parallelism of emergent light rays of the second collimating lens 12 and the uniformity of the light rays irradiated on the DMD chip 9 are ensured, and the precision of a sub-resolution structure and the uniformity of an optical axis of a printing breadth are ensured; meanwhile, the equipment is convenient for operators to return to zero, and the equipment is convenient to use and remove faults.

The projection device is arranged on the side of the light board 3 remote from the first collimating lens 8 by means of a mounting frame 11, which comprises a DMD chip 9, a chip driver (not shown in the figure) and a projection objective 10. The DMD chip 9, the projection objective 10, the trough 19 and the printing platform 20 are sequentially arranged from bottom to top.

The DMD chip 9 and the chip driver in the projection device are connected with the computer control component, wherein the chip driver can receive the section picture data of the model from the computer control component and convert the section picture data into corresponding driving signals to be sent to the DMD chip 9; the driving signal received by the DMD chip 9 and thereby controlling the on-off state of all the micro-mirrors on the DMD chip 9, wherein the on-state means that the micro-mirrors can reflect the light received by the DMD chip 9 from the second collimating lens 12, and the off-state means that the micro-mirrors cannot reflect the light received by the second collimating lens 12, thereby forming a corresponding exposure pattern; the projection objective 10 is used to project the exposure pattern formed by the DMD chip 9 onto a printing plane (the printing plane is the upper surface of the material to be cured for current printing, which is the working surface of the printing platform). The pixels of the exposure pattern are images of the DMD chip 9 formed by the micro-mirrors through the projection objective 10 on the printing plane, and since the light irradiated onto the DMD chip 9 is a plurality of groups of quasi-parallel light (as shown in fig. 6) with different deflection angles generated by the light source module, the image formed by the single micro-mirrors on the DMD chip 9 will be a bright spot with a shape scaled in equal proportion and a plurality of dark bright spots (aberration) generated by the surrounding translation of the bright spot, as shown in fig. 3.

In contrast, a single micro-mirror image obtained by a conventional projection printing system is an equally scaled bright spot (shown as an image) and a continuous ring around it (shown as an aberration), as shown in fig. 2. Similar to the translation distance of these slightly darker bright spots (aberrations) in fig. 3, which are determined by the magnitude of the quasi-parallel light deflection angle impinging on the DMD chip 9 (as shown in fig. 5), the combination of these slightly darker bright spots and bright spots will give the image formed by a single micro-mirror a more complex controllable appearance, rather than the original simple shape (the original shape is mostly square), when multiple micro-mirrors are imaged, the projected exposure pattern will have a more complex shape, which is projected onto the photo-curable material to shape it, so that a sub-resolution structure can be constructed, as shown in fig. 4.

The projection objective 10 employs an objective with a magnification of 10.

The micro-vibration mirror arrangement surface on the DMD chip 9 forms an angle of 45 degrees with the micro-lens arrangement surface on the micro-lens array 7, so that the sensitivity of the sub-resolution structure adjustment is improved while the sub-resolution structure size in each direction is ensured to be uniform, the adjustment of the sub-resolution structure size in a larger range is realized, and the requirement of high printing precision under different printing breadth requirements is met.

A TIR prism is arranged between the projection objective 10 and the DMD chip to adapt to the turning angle of the micro lens on the DMD chip in the on-off state.

The hopper 19 is used for loading a photo-curing material, and the photo-curing material can be photo-curing resin, photosensitive resin, photo-curing hydrogel or the like. The bottom of the trough 19 is made of high light transmission material, and can be one or a combination of a plurality of high light transmission glass, FEP, PET, PDMS and acrylic; a print platform 20 for forming and carrying a print object.

The printing movement device comprises a Z-axis movement device 21 and a Y-axis movement device 22, the moving end of the Z-axis movement device 21 is connected with an extension part perpendicular to the moving direction of the Z-axis movement device, and one end of the extension part far away from the Z-axis movement device 21 is provided with a printing platform 20; the Z-axis movement device 21 is used for adjusting the height of the printing platform 20 so as to change the height of the cured product, and lifting the cured part to realize the layer-by-layer superposition of the cured materials to finish the printing of the product; the Z-axis moving device 21 is mounted on the base plate 1 through the bracket 4. One end of a trough 19 is arranged at the upper end of the Y-axis movement device 22, the other end corresponding to the end of the trough 19 is arranged on the bottom plate 1 through a supporting rod 2, and the other end of the trough 19 is connected with the supporting rod 2 in a variable angle manner; the Y-axis movement device 22 is operative to drive the end of the chute 19 connected thereto to move up and down for changing the angle of inclination of the chute 19 so as to cause the cured product to be peeled from the chute 19. In this embodiment, the Z-axis moving device 21 is a ball screw nut type linear module, and the Y-axis moving device 22 is a through motor mounted on the base plate 1 through the stand 5.

The base plate 1 and the supporting structure of each part are used for building a structural frame for supporting and fixing the dual-resolution projection type photo-curing 3D printing system. Wherein, bottom plate 1 is the base of whole printing system, and backing bar 2, ray apparatus board 3, support 4 all install on bottom plate 1, and wherein backing bar 2 is used for the one end of fixed silo, and ray apparatus board 3 is used for installing ray apparatus motion device and mounting bracket 11, and support 4 is used for installing Z axle motion device, and upright 5 is used for installing Y axle motion device, and mounting bracket 11 is used for installing projection arrangement. The bottom plate 1, the support rod 2, the optical machine board 3, the bracket 4, the stand 5 and the mounting frame 11 jointly form a frame of the printing system.

The computer control assembly comprises an upper computer, an optical machine control component and a printing motion control component. The upper computer is used for man-machine interaction, generating cross-section pictures and control instructions of the 3D model to be printed with set intervals along the printing direction, and coordinating the work of all the components; the optical machine control component is used for calculating the relative positions of the light source array (the light source 6 and the micro lens array 7), the first collimating lens 8 and the second collimating lens 12 and the light intensity of the light source 6 according to the set micro structure size, and controlling the light source and the micro lens array, the first collimating lens 8 and the second collimating lens 12 to reach the set positions and the light source to reach the set light intensity. Besides, the optical machine control component is also used for transmitting the model section picture generated by the upper computer to the projection device to form a corresponding exposure pattern. The printing motion control part is used for controlling the printing motion device to realize lifting of the printing platform and stripping and recovery of the trough.

The upper computer is a personal computer with IO devices such as a display, a keyboard and a mouse, is popular, is convenient for system deployment, and is beneficial to system popularization. The upper computer is provided with software, and the software is particularly responsible for various tasks of the upper computer. The software has a double-port communication function and can simultaneously perform two-way communication with the optical machine control part and the printing motion control part. The software can read in the STL format file of the pre-printed 3D model and display the STL format file in a three-dimensional environment, and simultaneously provides model control functions including rotation, scaling, translation and the like, so that an operator can conveniently adjust relevant parameters of the pre-printed 3D model. The software can generate cross-section pictures with certain intervals of the pre-printed 3D model along the printing direction, the outline of the pre-printed 3D model at different positions along the printing direction is obtained according to triangle vertex information in the STL file, the internal and external directions of the pre-printed 3D model and the filling starting point of the model are obtained according to triangle normal vector information in the STL file, four-communication detection is carried out according to the internal filling starting point of the model, filling of the model is completed, and finally pictures are output according to filling information. The software can generate a printing control instruction, and based on the related information such as the layer height, the exposure time and the like given by an operator, a whole set of printing control instruction can be automatically generated according to grammar and stored in the memory of the upper computer. The software can monitor the current working condition of the printer, reflect the layer height printed currently and the exposure pattern projected currently, and facilitate operators to know the current working progress.

The optical machine control component adopts a singlechip, has lower cost and smaller volume, can be installed on a rack (a bottom plate 1, a supporting rod 2, an optical machine board 3, a bracket 4, a stand 5 and a mounting bracket 11), is internally provided with software, supports bidirectional communication with an upper computer and a DMD chip controller at the same time, is provided with a printing control instruction interpreter, interprets printing control instructions and drives corresponding ports, and executes corresponding commands. Besides, a fitting formula between the light intensity and the sub-resolution microstructure size parameter of the light source in the light source module and the relative positions of the light source array (the light source 6, the micro lens array 7), the first collimating lens 8 and the second collimating lens 12, which are obtained by theoretical formula, simulation and experimental data, is provided for calculating the position and the light intensity of each part.

The printing motion control part adopts a singlechip, has lower cost and smaller volume, can be also arranged on a frame (a bottom plate 1, a supporting rod 2, an optical machine bottom plate 3, a bracket 4, a stand 5 and a projection device frame 11), is internally provided with software, supports two-way communication with an upper computer, is provided with a printing control instruction interpreter, interprets printing control instructions and drives corresponding ports to execute corresponding commands.

The printing method of the projection type photo-curing 3D printing system comprises the following steps:

s1, slicing the 3D model to be printed according to a set printing layer height by the upper computer to obtain model section pictures which are arranged in sequence;

s2, driving an optical machine movement device to control the light source array, the first collimating lens and the second collimating lens to move to corresponding positions by the optical machine control component according to the set microstructure size and the set position, and controlling the light source array to output set light intensity; the light source array emits light, and a plurality of groups of quasi-parallel light with different deflection angles are formed after passing through a collimating lens group consisting of a first collimating lens and a second collimating lens to irradiate the projection device. The number of groups of quasi-parallel light is the same as the number of light sources in the light source array;

simultaneously, the optical machine control component sequentially transmits the section pictures to the projection device, and the projection device generates corresponding exposure patterns according to the currently received section pictures and projects the exposure patterns to the printing platform;

s3, after the exposure pattern to be generated exposes the printing platform for a set time, generating a curing material with a certain thickness on a printing plane (working surface of the printing platform) to finish printing of the current layer;

S4, the printing motion control part drives the printing motion device to control the height of the printing platform to rise, and then the trough is controlled to be stripped from the printed material; lifting the printing platform to a printing layer height with the bottom of the trough after stripping, and restoring the trough to an initial state to prepare for printing of the next layer;

s4, repeating the steps S2 and S4 until printing of the whole model is completed.

Application:

by using the printing system and the printing method thereof, a 10-time projection objective is adopted, and the real light source is an LED lamp bead; a virtual light source is formed by using a 3*3 microlens array with single microlens size of 1.3mm x 1.3mm, and a method of adjusting the distance focusing of the collimating lens group is adopted to obtain a front equivalent focal length of 7.84mm and a rear equivalent focal length of 15.03mm for printing, so that a sample with a microstructure average width of 24.09 micrometers is obtained as shown in (a) of fig. 7. Fig. 7 (b) shows a surface printed by a conventional DLP printing system, in which a projection objective lens is a 10-magnification objective lens. As can be seen from fig. 7, the surface printed by the dual-resolution projection type photo-curing 3D printing system provided by the embodiment of the invention has longitudinal grooves, and the microstructure is clear; the surface printed by the common printing system is messy, and no obvious structural characteristics exist.

Application example 1

By utilizing the projection type photo-curing 3D printing system and the printing method thereof, a 10-time projection objective lens is adopted, a 3*3 micro lens array with single micro lens size of 1.3mm and 1.3mm is used for forming a virtual light source, and the real light source is an LED lamp bead; and (3) obtaining the front equivalent focal length of 4.64mm and the back equivalent focal length of 14.22mm by adopting a method for adjusting the spacing focusing of the collimating lens group, and printing to obtain a sample with the average width of 21.24 microns of the microstructure shown in FIG. 8.

Application example 2

By utilizing the projection type photo-curing 3D printing system and the printing method thereof, a 10-time projection objective lens is adopted, and a real light source is an LED lamp bead; a 3*3 microlens array with single microlens size of 1.3mm x 1.3mm is used for forming a virtual light source, and a method of adjusting the distance focusing of a collimating lens group is adopted for obtaining a front equivalent focal length of 10.39mm and a rear equivalent focal length of 15.87mm for printing, so that a sample with a microstructure average width of 26.44 microns as shown in fig. 9 is obtained.

Application example 3

By utilizing the projection type photo-curing 3D printing system and the printing method thereof, a 10-time projection objective lens is adopted, and a real light source is an LED lamp bead; a 3*3 micro-lens array with a single lens size of 1.3mm x 1.3mm is used for forming a virtual light source, a method of adjusting the interval focusing of a collimating lens group is adopted for obtaining a front equivalent focal length of 12.79mm and a back equivalent focal length of 16.72mm for printing, and a sample with a microstructure average width of 31.66 microns as shown in fig. 10 is obtained.

Application example 4

By utilizing the projection type photo-curing 3D printing system and the printing method thereof, a 10-time projection objective lens is adopted, and a real light source is an LED lamp bead; a 3*3 micro-lens array with a single lens size of 1.3mm x 1.3mm is used for forming a virtual light source, a method of adjusting the interval focusing of a collimating lens group is adopted for obtaining a front equivalent focal length of 15.16mm and a rear equivalent focal length of 17.60mm for printing, and a sample with a microstructure average width of 36.90 microns is obtained as shown in fig. 11.

Claims (8)

1. A dual resolution projection-type photo-curing 3D printing method, comprising: and constructing a macroscopic structure by utilizing the DMD chip, and simultaneously adopting a plurality of groups of quasi-parallel light with different incident angles to irradiate the DMD chip and form a discrete aberration construction microstructure on an imaging surface.

2. The dual resolution projection type photo-curing 3D printing method according to claim 1, wherein the plurality of groups of quasi-parallel light beams with different incident angles are obtained by collimating light from the light source array through the collimating lens group.

3. The dual resolution projection photo-curing 3D printing method according to claim 2, wherein the microstructure is adjusted by changing the number of light sources in the array of light sources and/or the magnitude of the incident angle of the light.

4. The dual resolution projection type photo-curing 3D printing method according to claim 3, wherein the angle of incidence of the light rays incident on the DMD chip is adjusted by adjusting the equivalent focal length of the collimating lens group.

5. The dual resolution projection light curable 3D printing method of claim 2, wherein the light source array is a virtual light source array or a real light source array.

6. The dual resolution projection type photo-curing 3D printing method according to claim 5, wherein when the light source array is a virtual light source array, the light source array is constructed by passing a real light source through a micro lens array.

7. The dual resolution projection type photo-curing 3D printing method according to claim 6, wherein the virtual light source array is constructed by collimating the real light source and then passing through the micro lens array.

8. The dual resolution projection photo-curing 3D printing method according to any one of claims 1 to 7, comprising the steps of:

(1) Slicing the 3D model to be printed to obtain model section pictures which are arranged in sequence;

(2) The light source array emits light, a plurality of groups of parallel light with different incident angles are obtained after the light is collimated by the collimating lens group and irradiated on the DMD chip to form discrete aberration, and a microstructure is constructed;

(3) Taking an un-traversed layer of the model as a current layer in sequence while constructing a microstructure, transmitting a section picture of the current layer to a DMD chip to construct a macroscopic structure, and generating an exposure pattern with microscopic and macroscopic double resolutions;

(4) The projection objective projects the generated exposure pattern onto a printing plane to finish photo-curing printing of the current layer;

(5) Repeating the steps (3) and (4) until the section pictures of all layers are traversed, and completing dual-resolution photo-curing 3D printing of the model.