WO2021114602A1

WO2021114602A1 - 3d printing method and 3d printing system

Info

Publication number: WO2021114602A1
Application number: PCT/CN2020/097098
Authority: WO
Inventors: 夏春光; 亚历山大斯洛克; 约翰科瓦拉; 杰森巴希
Original assignee: 深圳摩方新材科技有限公司
Priority date: 2020-06-19
Filing date: 2020-06-19
Publication date: 2021-06-17

Abstract

A 3D printing method and system, comprising: generating a 3D digital model of a sample to be printed and cutting the 3D digital model into an image sequence; sending the images to a micro-display device, the micro-display device provided with a light source projecting the images by means of a projection lens onto an interface of an oxygen-permeable film or hard window and resin at one end of a print head; an image acquisition unit collects the images reflected back by a spectroscope and detects the quality of the projection images, and printing is controlled on the basis of the detected quality; performing exposure printing; after one layer is printed, adjusting back to position and adjusting the up-down distance between the print head and the sample to print the thickness of the next layer, the gap between the sample and the transparent window of the print head being filled with the resin required to print the next layer; and repeating exposure and printing in turn until printing is complete and the model is replicated in the resin tank; the present 3D printing method and system use the hard edge of the lower end of the print head as a coating scraper, and simultaneously implement the splicing movement and coating steps, saving time and increasing efficiency.

Description

3D printing method and 3D printing system

Technical field

The invention relates to 3D printing technology, in particular to a 3D printing method and a 3D printing system.

Background technique

Stereo lithography was initially considered a rapid prototyping technology. Rapid prototyping includes a series of technologies that can be used to create real scale models of production components directly from computer aided design (computer aided design CAD) in a fast (faster than before) way. Since its disclosure in US Patent 4,575,330, stereolithography technology has greatly helped engineers visualize complex 3D part geometries, detect errors in prototype schematics, test key components, and verify with relatively low cost and faster timeframes than before. Theoretical design.

In the past few decades, continuous investment in the field of micro-electro-mechanical systems (MEMS) led to the emergence of micro-stereolithography (μSL), which inherited the basic principles of traditional stereolithography. But it has a higher spatial resolution. For example, K Ikuta and K. Hirowatari, "True three-dimensional micro-manufacturing using stereolithography and metal molding", the 6th IEEE Symposium on Microelectronics and Mechanical Systems in 1993, with the aid of single-photon polymerization and two-photon polymerization technology , The resolution of micro-stereolithography has been further enhanced to less than 200nm; for example, S.Maruo and K.Ikuta, "Three-dimensional micromachining by polymerization using single photon absorption", Appl.Phys.Lett.,vol.76,2000; S.Maruo and S.Kawata, "Two-photon absorption near-infrared photopolymerization for three-dimensional microfabrication", J.MEMS, vol. 7, pp.411, 1998; S. Kawata, HBSun, T. Tanaka and K.Takada, "Refined Features of Functional Microdevices", "Nature", Volume 412, Page 697, 2001.

The invention of projection micro-stereolithography (PμSL) by Bertsch et al. has greatly increased the speed. "Micro-stereolithography technology using liquid crystal display as a dynamic mask generator", Microsystem Technologies, p42-47, 1997; Beluze et al., "Micro-stereolithography technology: a new process for constructing complex 3D objects, MEM/MOEM Symposium on the design, testing and micromachining of ", SPIE Conference Proceedings, v3680, n2, p808-817, 1999. The core of this technology is a high-resolution spatial light modulator, which can be a liquid crystal display (LCD) panel or a digital light processing (DLP) panel, both of which can be obtained from the microdisplay industry.

Although projection micro-stereolithography technology has successfully achieved rapid manufacturing speed with good resolution, further improvements are still needed.

The display size of the DLP chip is currently limited to about 13mm. Therefore, when the projected pixel size is the same as the physical pixel size (5 to 8 microns), a single exposure area will be limited to half an inch. In order to print on a larger area with a single projection, the size of the projected pixels needs to be increased, thereby reducing the printing resolution (that is, the size of the projected pixels).

In projection micro-stereolithography (PμSL), there are three types of resin layer definition methods: the first uses a free surface, and the layer thickness is defined by the distance between the resin free surface and the sample stage. Due to the slow viscous movement of the resin, it takes more than half an hour to define a 10um thick resin layer with a viscosity of 50cPs when the printing area is larger than 1cm x 1cm. The second and third methods use transparent films or hard windows. Similarly, for these two cases, there is currently no good way to define a resin layer of 10um or less on an area of 5cm X 5cm or larger, especially for the film case, even if it is faster than the free surface case , It is still unimaginable slow. In the case of a hard window, the fluid force generated when the two surfaces of the sample and the hard window approach and separate before or after exposure is large enough to damage the sample.

In all 3D printing technologies, the accuracy and efficiency of size reproduction are very important. For example, in the immersion projection micro-stereolithography (PμSL) system (Figure 1), it is very important to have high precision and high efficiency in the size control of all layers. Only in this way can the actual CAD model be accurate in a short time. Copy it out.

Summary of the invention

Based on this, it is necessary to provide a 3D printing method that can improve printing efficiency.

At the same time, a 3D printing system that can improve printing efficiency is provided.

A 3D printing method, including:

Slicing: generating a 3D digital model of the sample to be printed, cutting the 3D digital model into an image sequence, each image in the image sequence represents a layer of the 3D digital model, and controlling the printing direction of the print head according to the slicing direction of the model;

Projection: The image is sent to the micro display device, and the micro display device with a light source projects the image on the interface between the transparent window at one end of the print head and the resin through the projection lens;

Image detection: The image acquisition unit collects the image reflected by the spectroscope and detects the quality of the projected image, and prints according to the quality control of the detection;

Exposure printing: The micro display device with a light source irradiates the projected image with light, and the exposure produces a cured layer, which represents the corresponding layer of the projected image in the 3D digital model. When an exposure is over, the print head moves to a new area, the cone of the print head The hard edge of the end is used as a resin layer scraper. The coating thickness is determined by the gap between the end of the print head and the top layer of the sample. Since the print head is located 1 to 5 mm below the free surface of the resin, the resin behind it flows and covers the previous Bare area

Continue to expose and print: After one layer is printed, control the print head to move away from the print area, move the print head away from the sample, adjust the print head or sample stage to return, move the print head outside the boundary of the sample, adjust the print head and sample The upper and lower distance is the thickness of the next layer to be printed. The gap between the sample and the transparent window of the print head is filled with the resin needed to print the next layer. The exposure and printing are repeated in sequence, and the print head is scratched and coated to gradually expose a new layer. Print the next layer until the printing is completed and the model is copied in the resin tank.

In a preferred embodiment, in resin meniscus printing, after one layer of printing is completed, the sample and the substrate are immersed in the resin and immersed 2mm to 8mm so that the new resin covers the top surface of the sample, and then the substrate drives the sample Return to position and adjust the distance between the print head and the sample to the thickness of the next layer. The print head moves in from the outside of the sample, scrapes, coats and gradually exposes the new image. The print head pushes the excess resin back into the resin tank.

In a preferred embodiment, the print head has a hollow trapezoidal cylindrical structure, and a lock ring is provided at the tapered end of the print head. The tapered end of the print head covers the non-stick film and forms a transparent window, and the lock ring is placed on the transparent The upper part of the window.

In a preferred embodiment, the print head is located at the lower part of the substrate for printing, the transparent window of the print head is located 0.5-2mm below the free surface of the resin, and the print head and the substrate move relative to each other in the X/Y/Z direction to define the layer And the splicing layer is faceted.

In a preferred embodiment, the substrate is set on a printing platform, and the printing platform drives the substrate to move in the X, Y, and Z directions according to printing. When exposure printing or continuing exposure printing, the printing is controlled according to P=P ₀ +P ₁ The head pressure is to compensate for the deformation of the transparent window caused by contact with the printing resin. P ₀ is the pressure of the atmospheric pressure of the non-adhesive film of the print head, P ₁ =ρ ₁ gh, ρ ₁ is the resin density, g acceleration of gravity, and h The depth of the non-stick film of the print head under the resin; during printing, the pressure in the print head is controlled by the flow of gas. If the pressure sensor detects the difference between the pressure of the print head and the set pressure, the mass flow controller is controlled according to the PID setting Adjust the flow rate until the pressure in the print head reaches the set value.

In a preferred embodiment, it further includes a restrictor arranged at the downstream outlet of the print head, the restrictor is in a flow-blocking state, and the flow rate of the restrictor is proportional to the pressure of the print head.

In a preferred embodiment, if the printed image is larger than a single exposure size, stitch printing is performed, the image is divided into layer parts, the layer parts are printed step by step, and the edges are stitched together into a whole layer, and each layer part overlaps on the stitching edge. -20 microns.

In a preferred embodiment, when printing, error compensation is performed on the X/Y direction movement coordinates of the printing platform (X ₀ +XError(X ₀ ,Y ₀ ),Y ₀ +YError(X ₀ ,Y ₀ )), (X ₀ ,Y ₀ ) are theoretical coordinates,

XError(X ₀ ,Y ₀ )=C ₁ +C ₂ +C ₃ Y ₀ +C ₄ X ₀ Y ₀ +C ₅ X ₀ ² +C ₆ Y ₀ ²

YError(X ₀ ,Y ₀ )=D ₁ +D ₂ +D ₃ Y ₀ +D ₄ X ₀ Y ₀ +D ₅ X ₀ ² +D ₆ Y ₀ ²

C ₁ -C ₆ polynomial coefficients, based on the stitching and printing, the measurement error of the stitching point in the X direction is calculated by the quadratic least squares method.

The D ₁ -D ₆ polynomial coefficients are calculated based on the measurement error of the splicing point in the Y direction by the quadratic least squares fitting calculation during splicing printing.

In a preferred embodiment, when the print head is moved and stopped for exposure, the micro display device is controlled to project a picture on the center of the non-stick film of the print head, and the image acquisition unit captures and analyzes the imaging quality, and compares the imaging with the set theoretical value Compare, if the non-stick mold of the print head is deformed, according to the deformation formula

Adjust the flow to adjust the pressure in the print head. The deformation of the non-stick film set at the cone end of the print head is proportional to the pressure difference, υ Poisson coefficient, a is the radius of the non-stick mold of the print head, E Young's modulus, h is The thickness of the non-stick mold of the print head, p is the pressure difference between the two sides of the non-stick mold of the print head.

A 3D printing system, including: an image system that establishes a 3D digital model and cuts the 3D digital model into an image sequence, a control system, and a micro-display of the interface between the non-stick mold and the resin that is controlled to receive the series of pictures and project them to the print head A device, a projection lens set corresponding to the micro display device and controlled to perform projection, an image acquisition unit that collects and detects the quality of the projected image, and is set corresponding to the image acquisition unit and reflects the projected image to the image acquisition The unit receives and collects the spectroscope, the printing platform, the resin tank provided on the printing platform and loaded with resin, the lifting device provided on the printing platform, the substrate provided in the resin tank and connected with the lifting device, and the A print head with a hollow trapezoidal structure corresponding to the substrate, the hard edge of the print head is used as a squeegee to scrape the resin during printing, and the print head includes: an inner cavity of a hollow trapezoidal cylinder, and a lower end A transparent window formed by a non-stick film, a lock ring arranged at the lower end and placed on the upper part of the transparent window, a mass flow controller arranged at the upper end and controlled control of the pressure of the input gas flow on the non-stick film, and arranged at the downstream outlet of the print head juxtaposed The restrictor on the upper part of the lock ring.

The above-mentioned 3D printing method and 3D printing system use the hard edge of the lower end of the print head as a coating scraper, and the splicing movement and the coating step are performed at the same time, which saves time and improves efficiency.

In addition, the non-stick membrane is used to make the membrane and the sample stagger and separate, which reduces the force on the sample during separation by an order of magnitude.

In addition, a unique method of stitching multiple exposure printing is used to solve the problem, which can move the image (lens) or the sample. Save time and improve efficiency.

On the other hand, for resins with high viscosity (>500cPs), it is almost impossible to apply a very thin (~10 microns) resin layer every time when a film covering the entire print width (>50mmX50mm) is used. In large format, the resin driving pressure gradient provided by the tension of the film is very small, making the resin flow extremely slow. The invention adopts a film much smaller than the printing width, so that under the same film deformation, the driving pressure gradient of the resin is increased by an order of magnitude to increase the printing speed and accuracy.

Description of the drawings

FIG. 1 is a schematic diagram of a part of the structure of a 3D printing system according to an embodiment of the present invention;

2 is a cross-sectional view of a partial structure of a print head according to an embodiment of the present invention;

FIG. 3 is a schematic diagram of trajectory errors in the x and y directions of the 3D printing system during splicing printing according to an embodiment of the present invention;

4 is a schematic diagram of three exposure modes according to an embodiment of the present invention;

5 is a schematic diagram of a printing process with a print head located above a substrate according to an embodiment of the present invention;

6 is a schematic diagram of a printing process in which the substrate is located above the print head according to an embodiment of the present invention;

FIG. 7 is a schematic diagram of a meniscus printing process according to an embodiment of the present invention.

Detailed ways

The 3D printing method according to an embodiment of the present invention includes:

Exposure printing: The micro display device with a light source irradiates the projected image with light, and the exposure produces a cured layer, which represents the corresponding layer of the projected image in the 3D digital model. When an exposure is over, the print head moves to a new area, the cone of the print head The hard edge of the end is used as a resin layer scraper. The thickness of the coating is determined by the gap between the end of the print head and the top layer of the sample. The resin behind the print head flows and covers the previously exposed area;

Further, preferably, the micro display device of the present invention is a DLP with a 405 nm light source.

The printing of the present invention starts from the establishment of a geometric model by a computer or an image system, and the 3D digital model is cut into a two-dimensional picture in one direction, which is generally black and white, and may have grayscale. Each picture represents a thin layer in the 3D digital model. The slicing direction of the model will be the printing direction of the printer. The resulting series of pictures will be read by the printer in turn and projected on the interface between the non-stick film and resin at the end of the print head through DLP with a 405-nanometer light source. At the same time, a graphic image acquisition unit such as a CCD camera will be removed from the spectroscope. The reflected image judges the quality of the projected image. Within a certain exposure time, a certain thickness of cured layer will be produced where there is light, which represents the corresponding layer in the model represented by the projected picture. When the upper layer is exposed and printed, the print head will move away from the sample.

The sample stage will return according to different printing forms. After returning, the distance between the print head and the sample is the thickness of the next layer to be printed, and the gap between the sample and the print head film will be filled with the resin needed to print the next layer Floor. The exposure is repeated in sequence, and the model is copied in the resin tank as the sample stage descends layer by layer.

Since micro display devices such as LCD or DLP chips have a certain size, such as 1920X1080 pixel DLP, with an optical precision of ten microns, the printing area covered by a chip is only 19.2mmX10.8mm. Therefore, when the size of the sample is smaller than a chip When covering an area, we call it single projection mode. When the sample size exceeds the range covered by a chip, the present invention adopts the splicing printing mode. In the stitching printing mode, the picture representing the first layer of the model will be further cut into multiple pictures that are not larger than a single DLP resolution, that is, the layer part. For example, a 3800X2000 pixel picture can be cut into four 1900X1000 sub-pictures, and each sub-picture will represent a quarter of the area in a layer. For each layer in the model, it will be completed through multiple exposures, and all the sub-pictures of the current layer are projected in turn. In order to improve the mechanical properties at the junction of adjacent areas/pictures, a certain amount of overlap is usually given, usually 5-20 microns. The position and overlap of the exposure of each area are precisely controlled by the XY axis combination. There are two coordinate systems in the system, one is a DLP/LCD vertical coordinate system, and the other is a motion coordinate system composed of XY axes. If the two coordinate systems are not completely parallel due to mechanical assembly errors, there will be misalignment errors in adjacent areas during stitching and printing. For this reason, the measured error is compensated in the stitching printing mode. Due to the existence of the X and Y axes of the printing platform, for samples smaller than the printer's print format, multiple identical samples can be printed repeatedly in the entire format, which can increase the speed of mass production. This is the matrix printing mode.

When the print head is located on the lower part of the substrate for printing, the transparent window of the print head is 0.5-2mm below the free surface of the resin, and the print head and the substrate move relative to each other in the X/Y/Z direction to define the layer and splicing layer facets.

In meniscus printing, when one layer of printing is completed, the sample and substrate are immersed in resin and immersed 2mm to 8mm so that the new resin covers the top surface of the sample, and then the substrate drives the sample back to position, adjust the print head and sample The distance between is the thickness of the next layer to be printed. The print head moves in from the outside of the sample, scrapes, coats and gradually exposes the new layer, while the print head pushes the excess resin back into the resin tank.

Furthermore, the print head 30 of this embodiment has a hollow trapezoidal cylindrical structure, and a lock ring 36 is provided at the tapered end. The tapered end of the print head 30 covers the non-stick film and forms a transparent window 34. The lock ring 36 is placed on the upper part of the transparent window 34.

Further, the substrate of this embodiment is set on a printing platform, and the printing platform drives the substrate to move in the X, Y, and Z directions according to printing. When exposure printing or continuing exposure printing, the pressure of the print head is controlled _{according to P=P 0} +P ₁ It compensates for the deformation of the transparent window of the film caused by its contact with the printing resin. P ₀ is the pressure of the air atmosphere where the non-stick film of the print head is located, P ₁ = ρ ₁ gh, ρ ₁ is the resin density, g acceleration of gravity, h is the depth of the non-stick film of the print head under the resin; when printing, air is passed through The flow rate controls the pressure in the print head. If the pressure sensor detects that the pressure of the print head is different from the set pressure, the mass flow controller is controlled to adjust the flow according to the PID setting until the pressure in the print head reaches the set value.

Furthermore, the print head 30 of this embodiment further includes a flow restrictor 312 provided at the downstream outlet of the print head 30. The orifice of the orifice at the downstream outlet of the restrictor 312 is small enough (<50 microns) to be in a flow-blocking state, and its flow rate is only proportional to the upstream pressure in the print head.

When the actual pressure measured by the pressure sensor of the print head 30 is lower than the set pressure, the upstream mass flow controller (MFC mass flow controller) will increase the flow appropriately according to the PID (Proportion Integration Differentiation) setting , Until the pressure in the print head reaches the set value. vice versa.

Further, in this embodiment, if the printed image is larger than a single exposure size, stitch printing is performed, the image is divided into multiple layer parts, the layer parts are printed step by step, and the overlapping edges are stitched into a whole layer, and each layer part overlaps on the stitching edge 5-20 microns.

The printing process first generates a 3D model in a computer or image system, and then cuts the digital model into a series of images, where each image represents a layer of the model (such as 5 to 20 microns). The control computer or imaging system sends the image to the micro display device (such as DLP (digital light processing) or LCD (liquid crystal display)), and the image is projected onto the bottom surface of the print head (wet surface) through the projection lens )on. The bright areas converge, while the dark areas remain liquid. Due to the size limitation of LCD or DLP chips, such as a DLP chip with 1920X1080 pixels at 10um printing optical resolution, a single exposure only covers an area of 19.2mmX10.8mm. Therefore, if the cross section of the sample is larger than 19.2mmX10.8mm, it cannot be printed using a single exposure method. The invention provides a multi-exposure splicing printing method. In this way, the image representing the layer of the 3D model is further divided into multiple smaller images or layer parts, each of which is not larger than the DLP pixel resolution. For example, an image with a pixel resolution of 3800X2000 can be divided into four 1900X1000 sub-images, and each sub-image represents a quarter of the layer. As a result, the entire layer of the model will be printed section by section based on the sub-image. In order to improve the mechanical strength of the shared edge of adjacent parts, there is usually an overlap of about 5-20 microns on the edge.

XY printing platform components can precisely control the precise position and overlap amount. There are two coordinate systems: one is the vertical coordinate system with the DLP/LCD panel, and the other is the movement coordinate system composed of the XY axis of the printing platform. When the two coordinate systems are not parallel due to assembly tolerances, there will be offset errors on the common edges of adjacent sections. As shown in Figure 3, A is the size of a single exposure; B is the result of accurate alignment in the x direction; C is the result of an error offset in the x direction; B'is the result of accurate alignment in the y direction; C' It is the result of the error offset in the y direction. In precision printing, the error requirement is less than 10um, and the assembly tolerance of the stage is usually within the allowable range; and the offset is not linear with the moving distance of the printing platform. Therefore, in the present invention, the offset is measured at 5 or more uniformly distributed points in the x and y directions of the square sample printed in the full range. The offset error curve of at least second-order polynomial interpolation will be introduced into the translation in the XY direction to compensate for the offset, so as to ensure that the accuracy of the spliced printed samples is within the specification range.

_{When printing, perform error compensation (X 0} +XError(X ₀ ,Y ₀ ),Y ₀ +YError(X ₀ ,Y ₀ )) on the X/Y direction movement coordinates of the printing platform, (X ₀ ,Y ₀ ) is Theoretical coordinates,

Specifically, for precise stitching and printing (<10 microns error), first stitch and print 20X10 pieces of connected rectangles with a thickness of 19.2X10.8X0.1 mm on the full-frame sample table. If there are theoretically 100 squares on the front, back, left, and right of these squares. With a micron overlap, these squares will provide 19X9 splicing point data and their coordinates. Measure the actual overlap amount in the X direction and Y direction before the printed sample is removed from the sample stage. For example, the actual splicing overlap in the X direction is 80, and the error in the X direction at this coordinate point is XError(x,y) =100-80=20 microns, repeated measurement will get 19X9=171 points of error in the X direction, and also get the same 171 points of error in the Y direction.

Assume that the quadratic error function of the XY telecontrol system on the entire printing platform is:

XError(x,y)=C ₁ +C ₂ x+C ₃ y+C ₄ xy+C ₅ x^2+C ₆ y^2,

YError(x,y)=D ₁ +D ₂ x+D ₃ y+D ₄ xy+D ₅ x^2+D ₆ y^2,

Here x, y are coordinates, and C and D are polynomial coefficients. C _1～6 and D _1～6 can be calculated by the quadratic least squares fitting calculation based on the measurement errors in the X direction and the Y direction at 171 points. In this way, the axis movement error distribution in the entire printing area is obtained. These two error formulas will be used to correct the movement error of the axis. For example, the axis will go to the theoretical value (X ₀ , Y ₀ ). According to the error formula, the control command of the axis requires the axis to go to (X ₀ +XError (X ₀ ,Y ₀ ),Y ₀ +YError(X ₀ ,Y ₀ )).

When the print head stops and prepares for exposure after moving, control the micro display device to project a picture on the center of the non-stick film of the print head. The image acquisition unit captures and analyzes the imaging quality, and compares the imaging with the set theoretical value. If the print head is not sticky Mold deformation, according to the deformation formula

Adjust the flow rate to adjust the pressure in the print head, the deformation of the non-stick film set at the cone end of the print head is proportional to the pressure difference, υ Poisson coefficient, a is the radius of the non-stick mold of the print head or half of the diagonal length, E Yang The modulus, h is the thickness of the non-stick mold of the print head, and p is the pressure difference between the two sides of the non-stick mold of the print head.

As shown in Figures 1 and 2, the 3D printing system 100 of an embodiment of the present invention includes: an image system that establishes a 3D digital model and cuts the 3D digital model into an image sequence, a control system, and a controlled receiving image and projecting it to the print head The micro display device 50 of the interface between the non-stick mold and the resin, the projection lens 40 that is set corresponding to the micro display device and controlled to perform projection, the image acquisition unit 55 that collects and detects the quality of the projected image, and the image acquisition unit 55 corresponds to Set and reflect the projected image to the image acquisition unit 55 to receive and collect the spectroscope 60, the printing platform 80, the resin tank 70 arranged on the printing platform 80 and loaded with resin, the lifting device 85 arranged on the printing platform 80, and the setting A substrate 90 in the resin tank 70 and connected to the lifting device 85, and a print head 30 with a hollow trapezoidal structure provided corresponding to the substrate 90.

The print head 30 includes: a hollow trapezoidal inner cavity 32, a transparent window 34 formed by a non-stick film covering the lower end, a lock ring 36 arranged at the lower end and placed on the upper part of the transparent window, and arranged at the upper end to control the input gas A mass flow controller 38 for the pressure of the flow to the non-stick film, and a restrictor 39 provided at the downstream outlet of the print head 30 and placed on the upper part of the lock ring 36.

The image system and control system of this embodiment can be implemented by using the computer 20, or can be implemented by using a graphics processing chip and a control chip, respectively.

Further, the micro display device of this embodiment is a DLP or LCD chip. Of course, other chips can also be used as needed.

Preferably, the image acquisition unit of this embodiment can be implemented by using a CCD. Of course, other devices with image acquisition and processing functions, such as CMOS, can also be used.

Furthermore, the substrate 90 of this embodiment is connected by a substrate arm 92 lifting device 85. The lifting device 85 is provided on the printing platform 80.

The 3D printing method of the present invention provides a method to control the layer thickness in a larger printing area more accurately and faster at a greater speed, for example, a 10cm×10cm printing area with a layer thickness of 10um.

In an embodiment of the present invention, the print head is immersed several millimeters in the photosensitive resin. In another embodiment, the print head is a few hundred microns above the resin surface where the resin meniscus is formed.

The print head of this embodiment can be as large as one exposure of the entire DLP chip, or it can cover only a part of the DLP chip. The 3D printing method of the present invention not only greatly improves the dimensional accuracy of samples printed using, for example, a projection micro-stereolithography system, but also greatly improves the printing speed by eliminating the need to close or separate two contact surfaces in resin.

The tapered end (small end of the trapezoid) of the print head of this embodiment is covered and sealed by covering a non-stick transparent film to form a transparent window. The transparent window of this embodiment can be made of a gas-permeable material, especially an oxygen-permeable material, such as polydimethylsiloxane (PDMS) or Teflon AF (DuPont).

The print head of this embodiment may be provided with an ultrasonic source with a frequency exceeding 10 kHz to increase the flow rate of the resin during its movement when it is in contact with the resin.

The print head of this embodiment can be controlled by pressure to compensate for the deformation of the transparent window caused by contact with the printing resin. The pressure control gas can prevent the sample from sticking to the transparent window during the polymerization process, and the gas can be oxygen or a mixture thereof.

In an embodiment of the present invention, the printing platform is used to move in the XY direction to provide three printing modes. When only a sample smaller than the size of a single exposure is needed, it is called a single exposure mode. If multiple samples are needed, the printing platform will gradually move and print the same samples in the array, which is called the array exposure mode. When the sample size increases to exceed the size of a single exposure, the system will further divide a layer into multiple parts by overlapping 5μm to 20μm on the common or adjacent edges, and stitch adjacent parts into a whole layer. Stitching exposure mode. It is also possible to combine stitching mode and array mode.

In the present invention, the interpolation offset error curve based on the measurement data from the actual sample will be used to perform mechanical tolerance compensation during the translation of the printing platform in the XY direction to ensure that the accuracy of the spliced printed sample is within the specification range.

In an embodiment of the present invention, the print head 30 is immersed in the resin for 1 to 10 mm. When an exposure is over and the print head moves to a new area, the hard edge of the cone end of the print head will act as a resin coating blade. The coating thickness is determined by the gap between the flat end of the print head and the top layer of the sample. When the print head moves to an adjacent area, the resin behind the print head flows under the action of gravity and surface tension and covers the previously exposed area. After printing a complete layer, the print head will move beyond the boundary of the sample before the sample stage moves down to a thickness to define the next layer of fresh resin. After defining the new layer, the print head will move in and begin to scan and print the next layer step by step.

The sample stage of the present invention can drive the sample to move in the X, Y, and Z directions. You can also move the print heads to move each other by keeping the sample still.

In a preferred embodiment of the invention, the print head is 100 to 500 microns above the resin level together with the top layer of the sample. In this print head configuration, after one layer is printed, the sample and substrate will be immersed 2mm to 8mm into the free surface of the resin so that the fresh resin covers the top surface of the sample. Then, the sample will return with a gap equal to the thickness of the next layer from the print head. Likewise, the print head will move in from the outside of the sample, scratch, coat, and gradually expose a new layer.

The size of the transparent window of the print head of the present invention should cover the projection of a single DLP/LCD chip. For example, if the projection of a 17mm chip is 20mm and the pixel resolution is 10μm, the diameter of the window can be about 22mm. Furthermore, the transparent window at the tapered end of the print head 30 of this embodiment may be a DuPont Teflon AF2400 film with a thickness of 130 μm, which is breathable and has good light transmittance. Gas permeability, especially oxygen permeability, makes the film non-sticky during photopolymerization, because oxygen is a photocrosslinking inhibitor. The transparent window of the print head can also be made of polydimethylsiloxane (PDMS) film, or surface-coated with polydimethylsiloxane (PDMS).

Since the print head can be immersed in resin, the tapered end of the print head is tightly sealed in the liquid by a lock ring. Assuming that the non-stick film has linear elasticity, the deflection or deformation of the center of the non-stick film in the resin caused by hydraulic pressure is expressed by the following formula:

Where υ is the Poisson's ratio of the membrane, ɑ is the radius of the cone of the circular membrane, E is the Young's modulus, h is the thickness, and p is the pressure difference between the two sides of the membrane. It shows that the deformation of the transparent window at the cone end of the print head is proportional to the pressure difference; therefore, the deformation of the film can be eliminated by controlling the pressure in the print head and the pressure difference on both sides.

The liquid pressure of the transparent window of the print head 30 on the wet surface can be calculated by p=ρgh, where ρ is the density of the resin, g is the acceleration of gravity, and h is the depth of the resin from the free surface. Therefore, the pressure inside the print head should be controlled to compensate for the liquid pressure. This eliminates the deformation of the transparent window of the film. The combination of a mass flow controller (MFC), a restrictor located downstream and a pressure sensor on the print head will control the pressure P in the print head. The thickness of the non-stick oxygen suppression layer can be improved by increasing the oxygen concentration in the print head; therefore, MFC can use the flow rate of various oxygen concentration mixtures to control the pressure.

The printing process of an embodiment of the present invention starts with generating a 3D model in a computer, and then cutting the digital model into a series of images, each of which represents a layer (5 to 20 microns) of the model, and the control computer sends the image to the micro display The device is such as LCD or DLP chip, and then the image is projected onto the bottom surface (wet surface) of the print head through a projection lens. The bright areas converge, while the dark areas remain liquid. Due to the size limitation of the LCD or DLP chip, for example, a DLP chip with 1920X1080 pixels at 10um printing optical resolution, a single exposure only covers an area of 19.2mmX10.8mm. Therefore, if the cross-section of the sample is larger than 19.2mmX10.8mm, the single exposure method cannot be used for printing.

The present invention proposes a multi-exposure splicing printing method. In this way, the image representing a layer of the 3D model is further divided into a plurality of smaller images or layer parts, each image is not larger than the DLP pixel resolution. For example, an image with a pixel resolution of 3800X2000 can be divided into four 1900X1000 sub-images, each of which represents a quarter of the layer. As a result, the entire layer of the model will be printed step by step based on the sub-images. In order to improve the mechanical strength of the shared edges of adjacent parts, the edges usually overlap by about 5-20 microns.

The printing platform can precisely control the precise position and overlap amount. The invention is provided with two coordinate systems: one is the vertical coordinate system with the DLP/LCD, and the other is the movement coordinate system of the printing platform along the XY direction. When the two coordinate systems are not parallel due to assembly tolerances, there will be offset errors on the common edges of adjacent sections. As shown in Figure 3, A is the size of a single exposure; B is the result of accurate alignment in the x direction; C is the result of an error offset in the x direction; B'is the result of accurate alignment in the y direction; C 'Is the result of the error offset in the y direction.

In precision printing with an error requirement of less than 10 μm, it is difficult for the assembly tolerance of the printing platform to be within the allowable range; and the offset of the axis positioning and the movement distance of the printing platform are not linear. In the present invention, the offset is measured on at least 5 uniformly distributed points in the x and y directions of the square sample printed in the full range. The at least second-order polynomial error curve obtained by the least square fitting method will be used in the translation of the printing platform in the XY direction to compensate for the offset, so as to ensure that the accuracy of the spliced printed samples is within the specification range.

The present invention provides three printing modes (Figure 4). When only a sample smaller than a single exposure size needs to be printed, the printing platform will not move during the printing process, which is called single exposure mode. If multiple identical samples are required, the printing platform will gradually move in the XY direction and print the same samples in an array, which is called the array exposure mode. For small batch production, this mode is much faster than the repeated single exposure mode. When the sample size increases beyond the size of a single exposure, the system will further divide a layer into multiple parts by overlapping 5μm to 20μm on the common edge, and stitch adjacent parts into a whole layer. This is the stitching exposure mode. When a sample requires multiple identical samples but splicing exposure is required because the sample is larger than a single exposure, the splicing mode can be used in combination with the array mode.

In an embodiment of the present invention, the print head 30 is located on the top of the substrate and is immersed in the resin by 1 to 10 mm (Figure 5). The depth of immersion depends on the viscosity of the resin, and thinner resins perform shallower immersion. The projection lens projects the image from the LCD or DLP chip to the lower surface (wet surface) of the transparent print head. After one exposure is completed, the print platform in the stitching and array exposure printing mode moves along the X and Y directions or controls the print head along X Move in the /Y direction to move the print head to an adjacent area for the next exposure, but there is an overlap of about 5-20 microns on the common side, thereby fusing the adjacent parts together. When the print head is moved to a new area, the hard edge of the cone end of the print head will act as a resin coating blade. The coating thickness is determined by the gap between the flat end of the print head and the top layer of the sample. When the print head moves to an adjacent area, the resin behind the print head flows under the action of gravity and surface tension and covers the previously exposed area. After printing a complete layer, the print head will move beyond the boundary of the sample before the sample stage moves down the thickness of one layer to define the next layer of fresh resin.

By moving the print head outside the boundary of the sample, the interaction force between the print head and the sample is only the fluid shear force. This force is much smaller than the vertical or normal separation of the two surfaces in the resin that is typical in existing projection micro-stereolithography. As shown in the following formula:

σ=-pI+2με

Here σ is the fluid stress tensor, p is the pressure, I is the definite tensor, μ is the fluid viscosity, and ε is the velocity gradient tensor (or fluid strain tensor). For two surfaces that are almost in contact, when they are normally separated in a resin with a viscosity of 50cPs at a speed of 10mm/s, the vacuum effect is about 1e5Pas. However, if the two surfaces are sliced from each other with a gap of 20 μm, the force is about 1e2Pas. Therefore, this method greatly reduces the possibility of damage to the sample. After defining the new layer, the print head will move in and begin to scan and print the next layer step by step.

In the present invention, the configuration of the sample can be moved in the XYZ direction, or the print head can be moved while the sample remains stationary to achieve relative movement between the print head and the sample.

As shown in Fig. 6, in another embodiment, the positions of the print head and the sample substrate can be reversed. The transparent window of the print head is 0.5mm to 2mm below the free surface of the resin. The substrate is on the top and moves in the XYZ direction to define the layer and splicing layer sides. In this configuration, the printed part can be guaranteed to last tens of hours without being soaked in resin during the printing process. This may be required for some hydrogel resins, because prolonged soaking in the resin will cause the printed parts to swell, which can lead to dimensional errors.

As the viscosity of the resin increases, it will take longer and longer for the resin to flow and cover the printed area.

Further, in a preferred embodiment, an ultrasonic source with a frequency greater than 10 kHz is introduced into the print head, for example, a piezoelectric ceramic is closely attached to the print head housing to increase the flow speed of the resin.

As shown in FIG. 7, in another embodiment of the present invention, the print head and the top layer of the sample are raised to 100 to 500 microns above the free surface of the resin; the height depends on the viscosity of the resin. In this meniscus print head configuration, the steps for printing the entire layer are the same as the above steps, but after one layer is printed, the sample and the substrate will be immersed in resin 2mm to 8mm together so that fresh resin covers the upper surface of the sample. Then, the sample will move back to the height of the print head but one small step less, which is equivalent to the thickness of the next layer. Likewise, the print head will move in from the outside of the sample, scratch, coat, and gradually expose a new layer. In this way, the print head pushes the excess resin back into the resin tank.

The invention prints on a larger area at a faster speed than the current one.

The 3D printing method of this embodiment: generate a 3D digital model of the sample or object to be printed in a computer, and then cut the digital model into a series of image sequences, each image in the image sequence represents a layer of the 3D digital model, In this way, after each layer is formed, the sample or object is already formed.

The transparent print head includes a tapered end with a smooth surface. The print head is located next to a resin tank containing photosensitive resin and a substrate (such as a sample holder) used to fix the sample during printing. The smooth tapered end of the print head is in contact with the photosensitive resin. Move the transparent print head to a predetermined position, so that the position of the photosensitive resin can be selectively moved. During this movement, the edge of the smooth cone end of the print head can scrape the resin away. The coating thickness is defined by the gap between the smooth tapered end of the print head and the top layer of the sample. Or if there is no print layer before, the coating thickness is the gap between the smooth tapered end of the print head and the substrate used to fix the sample.

After the print head is placed, the images in the image sequence will be sent to the LCD or DLP chip. The chip and the light source project the image onto the smooth cone end of the transparent print head through the projection lens together with the light source, and begin to cure in the photosensitive resin area where the projected image allows the light source to reach.

When the image is larger than the size of a single exposure or subsequent coating is to be performed, the sample substrate and/or print head will be moved to continue printing.

The substrate and/or the print head are moved along the X, Y, Z direction or the X, Y direction by a high-precision positioning device, and the substrate and/or the print head can be positioned in a new area or depth.

The interpolation offset error curve of the sample measurement data can be input into the printing platform to compensate for errors caused by mechanical tolerances.

In many embodiments, the smooth tapered end of the print head is covered by a non-stick transparent and breathable film to form a transparent window and sealed, thereby preventing deformation due to the adhesion of the print head to the layer or premature curing of the resin. Accumulation at the tapered end of the print head. For example, oxygen can inhibit free radical chain reactions and can deform the print head due to the pressure of the introduced air/gas. Therefore, the pressure in the print head is usually controlled by introducing a controllable amount of gas, such as oxygen, to compensate for the deformation of the transparent window caused by the contact between the transparent window of the print head and the printing resin.

The digital image of the computer is projected on the transparent window of the transparent print head by the LCD or DLP microdisplay chip together with the light source through the projection lens, where the projection lens has an optical axis that intersects the sample or substrate. The projection lens is located above the sample or substrate, and between the surface of the substrate and the CCD (Charge Coupled Device). CCD (Charge Coupled Device) can monitor the projection on the print head, and can be focused along the optical axis through the projection lens. The movement and position of the sample or substrate along the X, Y and Z directions are controlled by the printing platform.

Compared with the currently available methods, the 3D printing method of the present invention enables the coating to be printed on a larger area and at a faster speed. The method includes:

Generate a 3D digital model of the sample to be printed in the computer, and then slice the 3D digital model into an image sequence, where each image in the image sequence represents a layer of the 3D digital model.

Place the transparent print head near the resin tank. The resin tank is equipped with photosensitive resin and a substrate for fixing the sample during the printing process. Wherein, the end of the transparent print head is provided with a smooth tapered end in contact with the photosensitive resin.

Move the transparent print head to a position for selective exposure of photosensitive resin. Among them, the edge of the smooth cone end of the print head will act as a squeegee by moving the excess resin, so that the thickness of the coating is equal to the gap between the smooth cone end of the print head and the top layer of the sample. Or, when the coating previously used for the sample has not been printed, the thickness of the coating will be equal to the gap between the smooth tapered end of the print head and the substrate used to fix the sample.

Send an image in the image sequence to the LCD or DLP chip, and project the image on the smooth cone end of the transparent print head through the projection lens together with the light source, so that the projected image allows the light from the light source to reach the photosensitive resin area Start curing the photosensitive resin.

When the image is larger than the size of a single exposure or a subsequent coating application is to be performed, the sample substrate and/or print head will be moved to continue printing the image.

The printing platform can drive the substrate or sample to move in the X/Y direction, and the lifting device can drive the substrate or sample to move up and down.

The flat tapered end of the print head of this embodiment is covered and sealed by a transparent window formed of a non-sticky, transparent, and air-permeable film. The material of the transparent window is an oxygen permeable material. The material of the transparent window is polydimethylsiloxane or fluororesin Teflon AF.

When one exposure is completed, in the stitching and array exposure printing mode, the print head is controlled to move to an adjacent area for the next exposure. Among them, when the print head moves to a new area, the hard edge of the cone end of the print head will be used as a resin coating scraper, and the thickness of the subsequent coating is determined by the gap between the smooth cone end of the print head and the top layer of the sample. Or when no sample-forming coating is printed, the thickness of the coating will be equal to the gap between the smooth tapered end of the print head and the substrate for fixing the sample.

When stitching and printing, an overlap of 5-20 microns is used on the common edge between the exposed area and the adjacent area to fuse the areas together.

The interpolation offset error curve based on the sample measurement data enters the printing platform and moves in the X/Y direction for compensation to compensate for mechanical tolerances to ensure that the accuracy of the spliced printed samples is within the specifications.

In a preferred embodiment of the present invention, an ultrasonic source with a frequency greater than 10 kHz is incorporated into the print head to increase the resin flow speed.

In addition, the deformation of the transparent window of the print head caused by contact with the printing resin is compensated by controlling the pressure in the print head.

In a preferred embodiment of the present invention, the print head is immersed in the photosensitive resin by 1 to 10 mm. If the coating has not been applied, raise the print head together with the top layer or substrate of the sample to 100 to 500 microns above the photosensitive resin. At this time, the print head forms a photosensitive resin meniscus by contacting the photosensitive resin.

The pressure inside the print head is achieved by controlling the pressure of the gas introduced into the print head. The gas introduced into the print head includes oxygen or a mixed gas of oxygen.

The digital image from the computer is projected by the LCD or DLP microdisplay chip together with the light source through the projection lens to the print head with a sealed, optically transparent and smooth cone end that is breathable. The projection lens has an optical axis that intersects the sample or the substrate, and the projection lens is located above the substrate and between the substrate and the charge coupled device. The charge-coupled device can monitor the projection on the print head, and can focus along the optical axis through the projection lens. The movement and position of the sample substrate in the X, Y and Z directions are controlled by three precision workbenches. In one embodiment, the print head is located above the substrate. In another embodiment, the substrate is located above the print head.

Taking the above-mentioned ideal embodiment based on this application as inspiration, and through the above description, relevant staff can make various changes and modifications without departing from the scope of the technical idea of this application. The technical scope of this application is not limited to the content in the specification, and its technical scope must be determined according to the scope of the claims.

Those skilled in the art should understand that the embodiments of the present application can be provided as methods, systems, or computer program products. Therefore, this application may adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, this application may adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program codes.

This application is described with reference to flowcharts and/or block diagrams of methods, devices (systems), and computer program products according to embodiments of this application. It should be understood that each process and/or block in the flowchart and/or block diagram, and the combination of processes and/or blocks in the flowchart and/or block diagram can be realized by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing equipment to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing equipment are generated It is a device that realizes the functions specified in one process or multiple processes in the flowchart and/or one block or multiple blocks in the block diagram.

These computer program instructions can also be stored in a computer-readable memory that can guide a computer or other programmable data processing equipment to work in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture including the instruction device. The device implements the functions specified in one process or multiple processes in the flowchart and/or one block or multiple blocks in the block diagram.

These computer program instructions can also be loaded on a computer or other programmable data processing equipment, so that a series of operation steps are executed on the computer or other programmable equipment to produce computer-implemented processing, so as to execute on the computer or other programmable equipment. The instructions provide steps for implementing the functions specified in one process or multiple processes in the flowchart and/or one block or multiple blocks in the block diagram.

Claims

A 3D printing method is characterized in that it comprises:

Slicing: generating a 3D digital model of the sample to be printed, cutting the 3D digital model into an image sequence, each image in the image sequence represents a layer of the 3D digital model, and controlling the printing direction of the print head according to the slicing direction of the model;

Projection: The image is sent to the micro display device, and the micro display device with a light source projects the image on the interface between the transparent window at one end of the print head and the resin through the projection lens;

Image detection: The image acquisition unit collects the image reflected by the spectroscope and detects the quality of the projected image, and prints according to the quality control of the detection;

Exposure printing: The micro display device with a light source irradiates the projected image with light, and the exposure produces a cured layer, which represents the corresponding layer of the projected image in the 3D digital model. When an exposure is over, the print head moves to a new area, the cone of the print head The hard edge of the end is used as a resin layer scraper. The coating thickness is determined by the gap between the end of the print head and the top layer of the sample. Since the print head is located 1 to 5 mm below the free surface of the resin, the resin behind it flows and covers the previous Bare area

Continue to expose and print: After one layer is printed, control the print head to move away from the print area, move the print head away from the sample, adjust the print head or sample stage to return, move the print head outside the boundary of the sample, adjust the print head and sample The upper and lower distance is the thickness of the next layer to be printed. The gap between the sample and the transparent window of the print head is filled with the resin needed to print the next layer. The exposure and printing are repeated in sequence, and the print head is scratched and coated to gradually expose a new layer. Print the next layer until the printing is completed and the model is copied in the resin tank.
The 3D printing method according to claim 1, wherein in resin meniscus printing, after one layer of printing is completed, the sample and the substrate are immersed in the resin by 2mm to 8mm, so that the new resin covers the top of the sample. Then the substrate drives the sample back to the free surface of the resin from 500 microns to 1000 microns. Adjust the distance between the print head and the sample to the thickness of the next layer. The print head moves in from the outside of the sample, scratches, coats, and gradually exposes. New layer, while the print head pushes the excess resin back into the resin tank.
The 3D printing method according to claim 1, wherein the print head has a hollow trapezoidal cylindrical structure, and a lock ring is provided at the tapered end of the print head, and the tapered end of the print head covers the non-stick film and forms a transparent window , The lock ring is placed on the upper part of the transparent window.
The 3D printing method according to claim 1, wherein the print head is located at the lower part of the substrate for printing, the transparent window of the print head is located 0.5-2mm below the free surface of the resin, and the gap between the print head and the substrate /Y/Z direction relative movement to define the layer and splicing layer facet.
The 3D printing method according to any one of claims 1 to 4, wherein the substrate is arranged on a printing platform, and the printing platform drives the substrate to move in the X, Y, and Z directions according to the printing, and exposes printing or continues to expose During printing, the pressure of the print head is controlled according to P=P 0 +P 1 to compensate for the deformation of the transparent window of the film caused by its contact with the printing resin. P 0 is the atmospheric pressure of the air in contact with the non-stick film of the print head, P 1 =ρ 1 gh, ρ 1 is the resin density, g acceleration of gravity, h is the depth of the non-stick film of the print head in the resin; during printing, the pressure in the print head is controlled by the flow of gas, if the pressure sensor detects the pressure of the print head and the set pressure When there is a difference, control the mass flow controller to adjust the flow according to the PID setting until the pressure in the print head reaches the set value.
The 3D printing method according to claim 5, further comprising a restrictor arranged at the downstream outlet of the print head, the restrictor is in a flow blocking state, and the flow of the restrictor is proportional to the pressure of the print head.
The 3D printing method according to any one of claims 1 to 4, wherein if the printed image is larger than a single exposure size, stitch printing is performed, the image is divided into multiple layers, and each layer is gradually exposed and stacked The edges are stitched into a whole layer, and each layer part overlaps the adjacent image by 5-20 microns on the stitching edge.
The 3D printing method according to claim 6, characterized in that, during printing, error compensation is performed on the X/Y direction movement coordinates of the printing platform (X 0 +XError(X 0 ,Y 0 ),Y 0 +YError(X 0 ,Y 0 )), (X 0 ,Y 0 ) are theoretical coordinates,

XError(X 0 ,Y 0 )=C 1 +C 2 +C 3 Y 0 +C 4 X 0 Y 0 +C 5 X 0 2 +C 6 Y 0 2

YError(X 0 ,Y 0 )=D 1 +D 2 +D 3 Y 0 +D 4 X 0 Y 0 +D 5 X 0 2 +D 6 Y 0 2

C 1 -C 6 polynomial coefficients, based on the stitching and printing, the measurement error of the stitching point in the X direction is calculated by the quadratic least squares method.

The D 1 -D 6 polynomial coefficients are calculated based on the measurement error of the splicing point in the Y direction by the quadratic least squares fitting calculation during splicing printing.
The 3D printing method according to any one of claims 1 to 4, characterized in that, when the print head is moved and stopped to prepare for exposure, the micro display device is controlled to first project a picture on the center of the non-stick film of the print head, and the image acquisition unit captures And analyze the imaging quality, compare the imaging with the set theoretical value, if the non-stick mold of the print head is deformed, according to the deformation formula

Adjust the flow to adjust the pressure in the print head. The deformation of the non-stick film set at the cone end of the print head is proportional to the pressure difference, υ Poisson coefficient, a is the radius of the non-stick mold of the print head, E Young's modulus, h is The thickness of the non-stick mold of the print head, p is the pressure difference between the two sides of the non-stick mold of the print head.
A 3D printing system, including: an image system that establishes a 3D digital model and cuts the 3D digital model into an image sequence, a control system, and a micro-display of the interface between the non-stick mold and the resin that is controlled to receive the series of pictures and project them to the print head A device, a projection lens that is set corresponding to the micro display device and controlled to perform projection, an image acquisition unit that collects and detects the quality of the projected image, and is set corresponding to the image acquisition unit and reflects the projected image to the image acquisition The unit receives and collects the spectroscope, the printing platform, the resin tank provided on the printing platform and loaded with resin, the lifting device provided on the printing platform, the substrate provided in the resin tank and connected with the lifting device, and the The print head with a hollow trapezoidal column structure corresponding to the substrate is characterized in that the hard edge at the lower end of the print head is used as a squeegee to scrape resin during printing, and the print head includes: an inner cavity of a hollow trapezoidal column , The transparent window formed by the non-stick film covering the lower end, the lock ring arranged on the lower end and placed on the upper part of the transparent window, the mass flow controller that is set on the upper end and controls the input gas flow to adjust the pressure of the print head in real time, A flow restrictor located at the downstream outlet of the print head and placed on top of the lock ring.