A scanning 3D printing method

Abstract

This invention discloses a scanning 3D printing method, relating to the field of 3D printer technology, comprising: converting a sliced ​​image into a vector image, and then rasterizing it into a finer bitmap image according to a specified precision; achieving a smaller grid precision by tilting the DMD; exposing sliced ​​images with a vertical dimension far exceeding the DMD's width by scrolling image flipping; obtaining the energy conversion rate curve of the laser corresponding to each exposure lens through laser energy calibration, and ensuring that the light output power of each lens remains consistent based on this curve; adjusting the angle magnification of the exposure lenses to ensure that the angle and magnification of the lenses to be stitched meet the precision requirements; observing the stitching status by projecting a pre-designed stitching image, and fine-tuning the lens position if the requirements are not met; this invention can perform large-format 3D printing, improve printing precision and the smoothness of the printed object's edges, and solve printing defects caused by distortion and uneven light field of large-format projection lenses.

Description

Technical Field

[0001] This invention relates to the field of 3D printer technology, specifically a scanning 3D printing method. Background Technology

[0002] Using 3D laser scanning technology, multi-dimensional data information of the object under test can be quickly acquired, and the 3D solid model of the object can be quickly reproduced. At the same time, the 3D point cloud data acquired by laser scanning can be used for subsequent processing such as finite element analysis, simulation analysis, and task simulation. It can also be used as a symmetrical application tool for 3D modeling software such as UG, CAD, and SolidWorks.

[0003] Currently, all DLP 3D printing technologies on the market operate using a static projection method, which has the following drawbacks: (1) the working range is severely limited, making it impossible to print large-format objects; (2) distortion and uneven light field cause the size of the printed object to shrink from the periphery to the center. Compared with other 3D printing equipment, DLP 3D printing equipment can achieve a projection pixel size of about 50μm, thus enabling the printing of products with higher detail precision requirements. At the same time, the surface projection feature makes it more efficient in processing cross-sections of the same area. The high degree of integration of the projection optical engine mechanism of the equipment makes the layer solidification molding function module more compact. Therefore, this invention proposes a scanning 3D printing method. Summary of the Invention

[0004] This invention aims to at least solve one of the technical problems existing in the prior art. To this end, this invention proposes a scanning 3D printing method that uses a DLP scanning exposure scheme and a multi-head stitching method to expose a large 3D printing slice image, thereby increasing the printing area based on DLP technology, improving printing resolution and the smoothness of the printed object's edges, and thus solving the problems existing in the current static projection-based DLP 3D printing technology.

[0005] To achieve the above objectives, an embodiment of the first aspect of the present invention provides a scanning 3D printing method, comprising the following steps:

[0006] Step 1: Expose the slice image using an oblique scan exposure scheme; specifically including:

[0007] The sliced ​​image is converted into a vector image, and then rasterized into a finer bitmap image according to the specified precision; smaller grid precision is achieved by tilting the DMD; and sliced ​​images with a vertical dimension far exceeding the DMD area are exposed by scrolling image flipping.

[0008] Step Two: Expand the horizontal exposure area using multi-lens stitching, specifically including:

[0009] The energy conversion rate curve of the laser corresponding to each exposure lens is obtained by laser energy calibration, and the output power of each lens is kept consistent based on this curve.

[0010] The angle and magnification of the exposure lens are adjusted to ensure that the angle and magnification of the lenses to be stitched meet the accuracy requirements; the stitching status is observed by projecting a pre-designed stitching diagram, and the lens position is finely adjusted if the requirements are not met.

[0011] Further, in step one, the sliced ​​image is converted into a vector graphic. The specific steps are as follows:

[0012] Use a contour extraction scheme to extract the contours of all connected regions in the sliced ​​image;

[0013] The extracted contours are processed and transformed into the actual physical contours of the graphic.

[0014] The physical contour is optimized to obtain the final vector image.

[0015] Furthermore, in step one, a smaller mesh precision is achieved by tilting the DMD, specifically including:

[0016] The DMD scanning direction is from top to bottom, the tilt angle is θ, the spacing between DMD pixels is d, the vertical black lines are the scan lines, and the spacing between the scan lines is c = dsinθ. In this way, the spacing between the scan lines can be reduced from d in the case of straight scan to c in the case of oblique scan.

[0017] Furthermore, the method to maintain consistent light output power for each lens in step two is to use a power meter to measure the energy of the laser produced by the laser under different input currents, thereby completing the plotting of the energy conversion curve.

[0018] Furthermore, the method for adjusting the angle magnification of the exposure lens in step two requires the assistance of a high-precision motion platform and a high-precision industrial camera, specifically including:

[0019] A static bitmap image is projected using a DMD. The number of pixels between the centers of the two circles, P1 and P2, is N, meaning the center distance is N*10.8 (each pixel is 10.8µm in size). The moving platform positions the centers of the circles P1 and P2 in the DMD at the same CCD center of the suction cup. The stage coordinates are recorded as (x1, y1) and (x2, y2) respectively. Then:

[0020] θ=arctan[(y2-y1) / (x2-x1)] (1)

[0021] M x =(x2-x1) / [10.8*N*cos(θ)] (2)

[0022] M x - Lens x-direction magnification, θ-DMD angle with stage x-direction.

[0023] Furthermore, in step two, the splicing status is observed by projecting a pre-designed splicing diagram. First, the positional relationship between each DMD needs to be marked. The specific marking method is as follows:

[0024] Coarse calibration: For each DMD, project a static bitmap image centered at the center of the DMD's usage area. Move the stage so that the center of mark P3 in DMD1, DMD2, and DMD3 is located at the center of the suction cup CCD4, respectively. Record the stage coordinates as (x1, y1), (x2, y2), and (x3, y3) respectively. Then, the distance between DMD1 and DMD2 is (x2-x1, y2-y1), and the distance between DMD2 and DMD3 is (x3-x2, y3-y2).

[0025] Move the stage so that the center of markP3 in dmd3 and dmd4 is located at the center of ccc5 of the suction cup. Record the stage coordinates as (x4, y4) and (x5, y5) respectively. Then the distance between dmd3 and dmd4 is (x5-x4, y5-y4).

[0026] Fine calibration: For densely exposed lines, the misalignment in the x and y directions at the line splicing points is observed under a microscope to calculate the relative positions of the dmd lines in order to perform strip segmentation and blackening.

[0027] Furthermore, strip segmentation is characterized by the fact that the three-angle regions on both sides are different during DMD scanning, and there must be an overlapping area in the X direction, while the position in the Y direction cannot be guaranteed to be completely consistent.

[0028] Furthermore, during the exposure process, a black image is used to synchronize each DMD; DMD1 and DMD2 overlap in the X direction and are misaligned in the Y direction; a black image is added to the right side of DMD1 where it overlaps with DMD2, and a black image is added at the beginning or end of the strip.

[0029] Compared with the prior art, the beneficial effects of the present invention are:

[0030] This invention first exposes slice images using a tilted scanning exposure scheme, converting the slice images into vector graphics. Then, it rasterizes them into finer bitmap images according to a specified precision. By tilting the DMD (Digital Modulator-Distributed Mask), a smaller grid precision is achieved, improving the resolution and graphic quality of the exposed images. A scrolling, flip-through method is used to expose slice images with a vertical dimension far exceeding the DMD's width. Next, a multi-lens stitching method is used to expand the horizontal exposure area. The energy conversion rate curve of the laser corresponding to each exposure lens is obtained through laser energy calibration. Based on this curve, the output power of each lens is kept consistent. By adjusting the angle magnification of the exposure lenses, the angle and magnification of the lenses to be stitched meet the precision requirements. The stitching status is observed by projecting a pre-designed stitching image; if the requirements are not met, the lens positions are fine-tuned. This invention enables large-format 3D printing, improving printing precision and the smoothness of printed object edges, and solving printing defects caused by distortion and uneven light field in large-format projection lenses. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 This is a schematic diagram illustrating the principle of a scanning 3D printing method according to the present invention.

[0033] Figure 2 This is a schematic diagram of DMD tilt scanning in this invention.

[0034] Figure 3 This is a schematic diagram of DMD angle calibration in this invention.

[0035] Figure 4 This is a static diagram showing the DMD positional relationship calibration in this invention.

[0036] Figure 5 These are the scanning strips corresponding to DMD1 and DMD2 in this invention.

[0037] Figure 6 This is the DMD for black image synchronization in this invention. Detailed Implementation

[0038] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0039] The first objective of this invention is to expose slice images using an oblique scanning exposure scheme, thereby overcoming the limitations of image size and projection accuracy in projection schemes; the second objective of this invention is to expand the horizontal exposure area using a multi-lens stitching method.

[0040] like Figure 1 As shown, a scanning 3D printing method includes the following steps:

[0041] Step 1: Expose the slice image using an oblique scan exposure scheme; specifically including:

[0042] S1: Convert the sliced ​​image into a vector image, and then rasterize it into a more refined bitmap image according to the specified precision;

[0043] S2: By tilting the DMD, a smaller grid precision (smaller than the DMD pitch) is achieved, improving the resolution and image quality of the exposed image;

[0044] S3: Expose slices that extend far beyond the DMD area in the vertical direction (scanning direction) by scrolling through the images;

[0045] In S1, the sliced ​​image (bitmap) is converted into a vector image, and the specific scheme is as follows:

[0046] Use a contour extraction scheme to extract the contours of all connected regions in the sliced ​​image;

[0047] The extracted contours are processed and transformed into the actual physical contours of the graphic.

[0048] The physical contour is optimized to obtain the final vector graphic.

[0049] In S2, a smaller mesh precision (smaller than the DMD pitch) is achieved by tilting the DMD. The principle is as follows: Figure 2 As shown;

[0050] The DMD scanning direction is from top to bottom, the tilt angle is θ, the spacing between DMD pixels is d, the vertical black lines are the scan lines, and the spacing between the scan lines is c = dsinθ. In this way, the spacing between the scan lines can be reduced from d in the case of straight scan to c in the case of oblique scan.

[0051] Step Two: Expand the horizontal exposure area using multi-lens stitching, specifically including:

[0052] V1: Obtain the energy conversion rate curve of the laser corresponding to each exposure lens through laser energy calibration, and ensure that the output power of each lens remains consistent based on this curve;

[0053] V2: By adjusting the angle and magnification of the exposure lens, the angle and magnification of the lenses to be stitched are made to meet the accuracy requirements;

[0054] V3: Observe the splicing status by projecting a pre-designed splicing pattern, and fine-tune the lens position if the requirements are not met.

[0055] In V1, the method to keep the output power of each lens consistent is to use a power meter to measure the energy of the laser produced by the laser under different input currents, thereby completing the plotting of the energy conversion curve.

[0056] The method for adjusting the angle magnification of the exposure lens in V2 requires the assistance of a high-precision motion platform and a high-precision industrial camera, specifically as follows: Figure 3 As shown, it includes:

[0057] A static bitmap image is projected using a DMD. The number of pixels between the centers of the two circles, marks P1 and P2, is N, meaning the center distance is N*10.8 (each pixel is 10.8µm in size). The moving platform positions the centers of marks P1 and P2 in the DMD at the same CCD center of the suction cup. The stage coordinates are recorded as (x1, y1) and (x2, y2) respectively. Then:

[0058] θ=arctan[(y2-y1) / (x2-x1)] (1)

[0059] M x =(x2-x1) / [10.8*N*cos(θ)] (2)

[0060] M x - Lens x-direction magnification, θ-DMD angle with stage x-direction;

[0061] In V3, the stitching status is observed by projecting a pre-designed stitching image. First, the positional relationship between each DMD needs to be calibrated, which requires a high-precision industrial camera. The calibration method is as follows:

[0062] V31: Coarse calibration:

[0063] Each DMD projects a static bitmap image centered at the center of the DMD's usage area, such as... Figure 4 As shown, the stage is moved so that the center of mark P3 in dmd1, dmd2, and dmd3 is located at the center of the suction cup cCD4, and the stage coordinates are recorded as (x1, y1), (x2, y2), and (x3, y3), respectively; then the distance between dmd1 and dmd2 is (x2-x1, y2-y1), and the distance between dmd2 and dmd3 is (x3-x2, y3-y2).

[0064] Move the stage so that the center of markP3 in dmd3 and dmd4 is located at the center of ccc5 of the suction cup, and record the stage coordinates as (x4, y4) and (x5, y5) respectively. Then the distance between dmd3 and dmd4 is (x5-x4, y5-y4).

[0065] V32: Fine calibration:

[0066] Exposing densely packed lines, examining the misalignment in the x and y directions at the line splicing points under a microscope, calculating the relative positions of the dmd lines; then performing strip segmentation and blackening.

[0067] To ensure energy uniformity, the three angular regions on both sides are different during DMD scanning, and there must be an overlapping area in the X direction, while the position in the Y direction cannot be guaranteed to be completely consistent; in order to ensure that the correct pattern is exposed, a black patch is needed to synchronize each DMD during the exposure process.

[0068] like Figure 5 As shown, DMD1 and DMD2 overlap in the X direction and are misaligned in the Y direction. To ensure energy uniformity in the exposure area, a black image needs to be added to the right side of DMD1 where it overlaps with DMD2. To synchronize each DMD (all DMDs start flipping images simultaneously and end flipping images simultaneously), a black image needs to be added at the beginning or end of the strip (e.g., ...). Figure 6 (As shown).

[0069] The above formulas are all numerical calculations after removing dimensions. The formulas are obtained by software simulation based on a large amount of data and are closest to the real situation. The preset parameters and preset thresholds in the formulas are set by those skilled in the art according to the actual situation or obtained by simulation based on a large amount of data.

[0070] Working principle of the invention:

[0071] A scanning 3D printing method first exposes a slice image using a tilted scanning exposure scheme, converting the slice image into a vector image. Then, it is rasterized into a finer bitmap image according to a specified precision. By tilting the DMD (Digital Modular Mask), a smaller grid precision (smaller than the DMD pitch) is achieved, improving the resolution and image quality of the exposed image. A scrolling image flipping method exposes slices with a vertical (scanning direction) area far exceeding the DMD's width. Next, a multi-lens stitching method expands the horizontal exposure area. Laser energy calibration obtains the energy conversion rate curve of the laser corresponding to each exposure lens, ensuring consistent light output power for each lens. The angle and magnification of the exposure lenses are adjusted to ensure the angle and magnification of the lenses to be stitched meet precision requirements. The stitching status is observed by projecting a pre-designed stitching image; if requirements are not met, the lens positions are fine-tuned. This invention enables large-format 3D printing, improves printing precision and the smoothness of printed object edges, and solves printing defects caused by distortion and uneven light field in large-format projection lenses.

[0072] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0073] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to any specific implementation. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method of scanning 3D printing, characterized by, The method comprises the following steps: Step one: exposing slice images with an inclined scanning exposure scheme; specifically comprising: Converting the slice images into vector images, and rasterizing them into more fine bitmap images according to the specified accuracy; achieving smaller grid accuracy through an inclined DMD; exposing slice images whose longitudinal length exceeds the DMD width by rolling the bitmap; Step two: achieving the expansion of the horizontal exposure width by means of multi-lens splicing, specifically comprising: Obtaining the energy conversion rate curve of each exposure lens corresponding to the laser by laser energy calibration, and ensuring the light output power of each lens to be consistent according to the curve; Adjusting the angle magnification of the exposure lens to make the angle and magnification of the lens to be spliced meet the accuracy requirements; observing the splicing condition by projecting a pre-designed splicing bitmap, and fine-tuning the lens position if the condition does not meet the requirements.

2. The method of claim 1, wherein, In step one, the slice images are converted into vector images, and the specific steps are as follows: Extracting the contours of all connected regions in the slice images by using a contour extraction scheme; Processing the extracted contours to convert them into the actual physical contours of the graphics; Optimizing the physical contours to obtain the final vector images. In step one, the inclined DMD is used to achieve smaller grid accuracy, and the specific steps are as follows:

3. A scanning 3D printing method according to claim 2, characterized in that, The scanning direction of the DMD is from top to bottom, the inclination angle is θ, the distance between the DMD pixels is d, the vertical black line is the scanning line, and the distance between the scanning lines is c=dsinθ, so the distance between the scanning lines is reduced from d in the straight scanning case to c in the inclined scanning case. In step two, the method for keeping the light output power of each lens consistent is as follows: measuring the energy of the laser generated by the laser under different input currents by using a power meter, thereby completing the drawing of the energy conversion curve. In step two, the method for adjusting the angle magnification of the exposure lens needs a high-precision motion platform and a high-precision industrial camera, and the specific steps are as follows:

4. The method of claim 1, wherein, Moving the platform to make the centers of marks P1 and P2 in the DMD at the same ccd center of the suction cup, and recording the stage coordinates as (x1, y1) and (x2, y2), respectively, then: In step two, the splicing condition is observed by projecting a pre-designed splicing bitmap, and first, the positional relationship between each DMD needs to be calibrated, and the specific calibration method is as follows:

5. The method of claim 4, wherein, Coarse calibration: each DMD projects a static bitmap with the center of the circle at the center of the DMD usage area, and the stage is moved to make the centers of marks P3 in DMD1, DMD2 and DMD3 at the centers of the suction cup ccd4, and the stage coordinates are recorded as (x1, y1), (x2, y2) and (x3, y3), respectively; then the distance between DMD1 and DMD2 is (x2-x1, y2-y1), and the distance between DMD2 and DMD3 is (x3-x2, y3-y2); Moving the stage to make the centers of marks P3 in DMD3 and DMD4 at the centers of the suction cup ccd5, and recording the stage coordinates as (x4, y4) and (x5, y5), respectively; then the distance between DMD3 and DMD4 is (x5-x4, y5-y4). By DMD throw a static bitmap, mark P1 and P2 two circle center between the pixels for N, that is, the center distance is N 10.8um, the size of a single pixel is 10.8um; ​ M x Lens x direction magnification, θ - DMD and stage x direction angle.

6. A scanning 3D printing method according to claim 5, characterized in that, ​ ​ ​ ​ Fine calibration: exposure to dense lines, through the microscope to see the line stitching x and y direction of the misalignment, calculate the mutual position between the DMD, to carry on the strip segmentation and black map.

7. The method of claim 6, wherein the method is a scanning 3D printing method. Strip segmentation performance: in the process of DMD scanning, the triangular area on both sides is different, and the X direction must have an overlapping area, and the Y direction position can not be guaranteed to be completely consistent.

8. The method of claim 7, wherein, In the process of exposure, the black map is used to synchronize each DMD; DMD1 and DMD2 have overlapping in X direction and misalignment in Y direction; black map is filled in the overlapping place of DMD1 and DMD2 on the right side, and in the beginning or end position of the strip.

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