A printing method for optimizing 3D printing surface quality

Abstract

The present invention provides a printing method for optimizing the surface quality of 3D printing. By graying the edge contour of a 3D printed model and utilizing the characteristic that photosensitive resin is insensitive to changes in several grayscale values ​​of the image grayscale in the printed model, the calculation of the grayscale value and / or correction of the edge contour of the printed model are simplified, thereby effectively improving the efficiency and print quality of 3D printing.

Description

Technical Field

[0001] The present invention belongs to the technical field of 3D printing, and in particular relates to a printing method for optimizing the surface quality of 3D printing. Background Art

[0002] 3D printing technology is booming, particularly DLP (Dysplastic Light-Emitting Diode) 3D printing, which has attracted widespread attention due to its high printing efficiency and surface shaping. However, DLP 3D printing accuracy is limited by the resolution of the DMD (Direct Motion Detector), resulting in rough surfaces and severe pixelation.

[0003] Currently, people on the market generally improve printing accuracy by zooming in and out of the lens, which will reduce the size of the print. If the resolution of the DMD does not change, then when converting the layer contour into an image format, the pixels at the edge of the contour are printed in grayscale, which will improve the surface quality of the print. The current existing technologies all perform image grayscale conversion by the area duty ratio of the layer contour at the pixel point, but this is computationally intensive and the conversion is difficult. Alternatively, the surface of the printed model can be smoothed by filtering the image after the layer contour conversion, such as by using a mean filter. However, in this method, if a 3*3 filter template is selected, the layer contour image will generally expand the print surface by one pixel. If a 5*5 filter template is selected, the layer contour image will generally expand the print surface by even two pixels, and the size of the printed model will be distorted.

[0004] In addition, if the printed model has a small hole structure, the scattered light of the DLP pixels or the residual light transmitted through the interlayer printing will distort the small hole structure of the model or even cause it to be blocked by curing.

[0005] Therefore, how to optimize conventional printing models to improve product surface printing quality has become a technical problem that needs to be solved urgently. Summary of the Invention

[0006] In order to solve the above technical problems, the present invention first provides a printing method for optimizing the 3D printing surface quality. First, the edge contour of the 3D printed model is grayscaled, and then the calculation of the grayscale value and / or the correction of the edge contour of the printed model are simplified to improve the printing efficiency and 3D surface printing quality.

[0007] The printing method comprises the following steps:

[0008] S1: Set the pixel size of the 3D printing projector to M*N, set the total projection format printable on the printer to a*b centimeters, obtain the dimensional accuracy of each pixel of the projector to (a / M) and (b / N) centimeters, (a / M) and (b / N) are equal, and allocate xM*xN size in advance in the memory space to store the digital image of xM*xN pixels;

[0009] S2: Use 3D printing software to edit a printing model. The physical size of the printing model is no larger than a*b centimeters. Map the projection area of ​​a*b centimeters in S1 to the digital image of xM*xN pixels in S1, and binarize the layer contours of the printing model according to the mapping relationship.

[0010] S3: filling the inner part of the binarized layer model contour according to the grayscale value of the bright pixel;

[0011] S4: Reduce the rows and columns of the binary image filled in S3 by x times, so that the pixel size of the entire format is M*N. Each pixel of the reduced image contains x of the original binary image. 2 pixels, the x 2 Each bright pixel value is 256 / x 2 The data is accumulated;

[0012] S5: Determine the x 2 Are all pixels bright pixels? If yes, the grayscale value is 255; if x 2 If not all pixels are bright pixels, the grayscale value of the reduced pixel is the accumulated value of the original pixel data;

[0013] S6: Convert the layer model of the printed model into a grayscale pixel image according to the steps S2-S5. If mean filtering is required for the grayscale pixel image, filter it according to a 3*3 or 5*5 filtering template after the conversion is completed. Otherwise, skip S6 directly.

[0014] S7: Starting the projector to perform light curing on the photosensitive resin according to the image data of the current printing layer, and turning off the projector after curing is completed according to the preset curing time, thereby completing the printing of the current printing layer;

[0015] S8: Repeat steps S2-S7 to perform the same operation on the next layer of contour of the printed model until the last layer of contour of the printed model is printed, and the printing of the printed model is completed.

[0016] According to one embodiment of the present invention, the value of x in step S2 can be 4, 6, or 8, preferably 4.

[0017] According to one embodiment of the present invention, the printing method also includes a correction step for correcting the contour expansion caused by image mean filtering. The correction step is located in S6, and the correction step is as follows: when performing image mean filtering, if the grayscale value of the pixel position is 0, mean filtering is not performed; if the grayscale value of the pixel position is not 0, mean filtering is performed, and the filtered image grayscale value is placed at this position.

[0018] According to one embodiment of the present invention, the correction step may also be based on the scaling amount that may be caused by mean filtering and resin curing shrinkage. For example, in step S2, the layer profile is scaled before binarization to eliminate the final printing error.

[0019] According to one embodiment of the present invention, step S7 in the printing method further includes: after a certain layer of resin is light-cured, in preparation for printing the next layer, turning on the ultrasonic device to vibrate the resin inside the resin tank. If the printed model has a pinhole structure, then during the printing process, the light boundary of each pixel will have scattered light, which will semi-cured part of the resin at the edge of the pinhole; in the printing of the next layer, the light of its pixel will also be partially transmitted, and the semi-cured resin will be secondary cured, which will cause the pinhole structure to be distorted or the pinhole to be completely blocked by curing. Then, during the printing process with a pinhole structure, the semi-cured resin attached to the edge of the printed model is caused to fall off by vibration, so that the resin around the pinhole will not be secondary cured or semi-cured, causing the pinhole to be distorted.

[0020] According to one embodiment of the present invention, the ultrasonic device in step S7 is arranged on the carrier substrate and / or the resin tank support plate of the printer, and the ultrasonic energy can be transmitted to the resin tank through the carrier substrate and / or the resin tank support plate to vibrate the resin inside the resin tank.

[0021] Beneficial effects of the present invention:

[0022] 1. Since photosensitive resin is not sensitive to changes in several grayscale values ​​of the image in the printed model, the present invention can effectively improve the efficiency and printing quality of 3D printing through a simple and convenient image grayscale method and a method of performing mean filtering on the image with a mask.

[0023] 2. The printing method of the present invention can also reduce the adhesion of semi-cured resin on the surface of the printed model through ultrasonic vibration, making the printing of models with microporous structures more engineering-friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A schematic diagram of the three-dimensional structure of a 3D printer used in the printing method of the present invention.

[0025] Figure markings: 1-projector, 2-carrying substrate, 3-oblique stripping device, 4-resin tank, 5-molding tray, 6-lifting adjustment mechanism, 7-cantilever beam, 8-device bracket, 9-control system, 10-stud bolt, 11-oblique stripping device bracket, 12-moving part, 13-support column, 14-resin tank support plate.

[0026] Figure 2 Schematic diagram comparing the binarization and grayscale of the model layer contour.

[0027] Figure 3 Schematic diagram of the model layer contour binarization transformation image.

[0028] Figure 4 for Figure 3 A partial enlargement of the upper left corner of the schematic.

[0029] Figure 5 Schematic diagram of the image after the internal filling of the model layer contour map.

[0030] Figure 6 for Figure 5 A partial enlargement of the upper left corner of the schematic.

[0031] Figure 7 For Figure 6 Schematic diagram of the image after grayscale conversion.

[0032] Figure 8 For Figure 7 Schematic diagram of the image after 3*3 mean filtering.

[0033] Figure 9 For Figure 7 Schematic diagram of the image after 5*5 mean filtering.

[0034] Figure 10 Schematic diagram of the operation of reducing rows and columns by 4 times.

[0035] Figure 11 The figure compares the time consumption of grayscale conversion using duty cycle calculation and 4x scaling.

[0036] Figure 12 This is a comparison chart of the physical model printed using duty cycle calculation and grayscale conversion calculated using 4x scaling.

[0037] Figure 13 Comparison diagram of the physical model with a small hole structure when ultrasonic printing is turned on and when it is not turned on during the printing process. DETAILED DESCRIPTION

[0038] The technical solutions of the present invention will be described in further detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanations of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are encompassed within the scope of protection that the present invention is intended to protect.

[0039] Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available or can be prepared by known methods.

[0040] Example 1

[0041] Combined with Figure 1-7 , 10, the projection format is 96*54mm, and the projection resolution is 1920*1080. Then the method of graying the model contour image specifically includes the following steps:

[0042] S1: Prepare a memory space with a resolution of (4*1920)*(4*1080) to store digital images. Map the 96*54mm format to this resolution, and the size of each pixel is 12.5um.

[0043] S2: Digitize the contour model into the memory space of (4*1920)*(4*1080) according to the pixel size of 12.5um set in S1. The pixels where the contour passes are set to 1, and the pixels where the contour does not pass are set to 0. Figure 3 As shown, Figure 3 The upper left corner of the partial enlargement is as follows Figure 4 shown.

[0044] S3: Fill the inner part of the binarized layer model contour, and fill the inner part according to the gray value of the pixel 1. Figure 5 As shown, Figure 5 The upper left corner of the partial enlargement is as follows Figure 6 As shown;

[0045] S4: Reduce the rows and columns of the filled (4*1920)*(4*1080) memory space by 4 times. Figure 10 As shown, each pixel of the image after reduction contains 16 pixels of the original binary image. These 16 pixels are accumulated according to the data of each bright pixel value of 16. If all 16 pixels are bright pixels, then the pixel after reduction is also a bright pixel with a grayscale value of 255. If not all 16 pixels are bright pixels, then the grayscale value of the pixel after reduction is the accumulated value of the original bright pixel data. If all 16 pixels are not bright, then the grayscale value of the pixel after reduction is zero, thus realizing the grayscale of the edge contour of the model. Figure 6, after grayscale conversion Figure 7 shown.

[0046] S5: Determine whether all the 16 pixels are bright pixels. If so, the grayscale value is calculated as 255; if not all the 16 pixels are bright pixels, the grayscale value of the reduced pixel is the accumulated value of the original bright pixel data;

[0047] S6: Convert the grayscale pixel image of the layer model of the printed model according to the steps of S2-S5. If the grayscale image needs to be filtered by mean, it will be filtered according to the 3*3 or 5*5 filtering template after the conversion is completed. Otherwise, skip S6 directly.

[0048] S7: Starting the projector to perform light curing on the photosensitive resin according to the image data of the current printing layer, and turning off the projector after curing is completed according to the preset curing time, thereby completing the printing of the current printing layer;

[0049] S8: Printer Figure 1 As shown, after the printer completes other related auxiliary operations, steps S2-S7 are repeated to perform the same operations on the next layer of contour of the printed model until the last layer of contour of the printed model is printed, and then the printing of the printed model is completed.

[0050] Example 2:

[0051] Combined with Figure 1-7 , 10, the projection format is 96*54mm, and the projection resolution is 1920*1080. Then the method of graying the model contour image specifically includes the following steps:

[0052] S1: Prepare a memory space with a resolution of (8*1920)*(8*1080) to store digital images. Map the 96*54mm format to this resolution, and the size of each pixel is 6.25um.

[0053] S2: Digitize the contour model into a memory space of (8*1920)*(8*1080) according to the pixel size of 6.25um set in S1. Pixels that the contour passes through are set to 1, and pixels that the contour does not pass through are set to 0.

[0054] S3: Filling the interior of the binarized layer model contour, wherein the interior filling is performed according to a grayscale value of 1 for each pixel.

[0055] S4: Reduce the padded (8*1920)*(8*1080) memory space by a factor of 8 in rows and columns. Each pixel of the reduced image contains 64 pixels of the original binary image. These 64 pixels are accumulated with a value of 4 for each bright pixel. If all 64 pixels are bright, the reduced pixel is also a bright pixel with a grayscale value of 255. If not all 64 pixels are bright, the grayscale value of the reduced pixel is the accumulated value of the original bright pixel data. If none of the 64 pixels are bright, the grayscale value of the reduced pixel is zero, thus achieving the grayscale of the model edge contour.

[0056] S5: Determine whether all the 64 pixels are bright pixels. If so, the grayscale value is calculated as 255; if not all the 64 pixels are bright pixels, the grayscale value of the reduced pixel is the accumulated value of the original bright pixel data;

[0057] S6: Convert the grayscale pixel image of the layer model of the printed model according to the steps of S2-S5. If mean filtering is required for the grayscale image, filter it according to a 3*3 or 5*5 filtering template after the conversion is completed. Otherwise, skip S6 directly.

[0058] S7: Start the projector to light-cure the photosensitive resin according to the image data of the current printing layer. After the curing is completed according to the preset curing time, turn off the projector, and the printing of the current printing layer is completed;

[0059] S8: Printer Figure 1 As shown, after the printer completes other related auxiliary operations, steps S2-S7 are repeated to perform the same operations on the next layer of contour of the printed model until the last layer of contour of the printed model is printed, and then the printing of the printed model is completed.

[0060] Example 3: Effect of ultrasonic vibration on printing of microporous model products

[0061] S1: grayscale the image using the method of Example 1, and then perform layer printing;

[0062] S2: After the current printing layer is printed, the ultrasonic vibration device is immediately turned on for 1 second and then turned off;

[0063] S3: grayscale the image using the method of Example 1, and then print the next layer; repeat this process until the model printing is completed. Figure 13 The left part is a model printed with the ultrasonic vibration device of Example 3 turned on. Figure 13 The right part is the model printed without the ultrasonic vibration device. Figure 13 As can be seen in the right part, the micropores of the model without ultrasonic printing have signs of being semi-cured.

[0064] Comparative Example 1:

[0065] The difference between this comparative example and embodiment 1 is that in step S6 of embodiment 1, the image processing is a 3*3 template with mask mean filtering. Figure 7 8 is the image comparison of whether the contour of the comparative printed model is processed by 3*3 mean filter, where Figure 7 For images that have not been processed with 3*3 mean filtering, Figure 8 For an image that has been processed with a 3*3 mean filter, the image processing is a 5*5 template with a mask mean filter. Figure 7 9 is the image comparison of whether the contour of the comparative printing model is processed by 5*5 mean filter, wherein Figure 7 For images that have not been processed with 5*5 mean filtering, Figure 9 The image is processed with 5*5 mean filtering.

[0066] Comparative Example 2: Comparison of printing effects under the printing model with accurate duty cycle calculation

[0067] The method of Example 1 obtains the grayscale of the image, and the calculation time of a certain layer is 96 milliseconds. Figure 11 The right half shows the complete printed product. Figure 12 As shown in the upper part;

[0068] The image grayscale is obtained by accurately calculating the duty cycle. The calculation time for the same layer is 140 milliseconds. Figure 11 The left half is shown; the complete product is printed as Figure 12 Shown in the lower half.

[0069] The above describes the embodiments of the present invention. However, the present invention is not limited to the above embodiments. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the scope of protection of the present invention.

Claims

1. A printing method for optimizing 3D printing surface quality, characterized in that: The printing method comprises the following steps: S1: Set the pixel size of the 3D printing projector to M*N, the total printable area on the printer to a*b centimeters, obtain the dimensional accuracy corresponding to each pixel of the projector to be (a / M) and (b / N) centimeters, (a / M) and (b / N) are equal, and allocate xM*xN size in advance in the memory space to store the digital image of xM*xN pixels; S2: Using 3D printing software to edit a printing model, the physical size of the printing model is no larger than a*b centimeters, and the physical size of a*b centimeters is mapped to a digital image of xM*xN pixels. The layer contours of the printing model are binarized according to the mapping relationship; S3: Filling the inner part of the binarized layer model contour according to the grayscale value of the bright pixel; S4: Reduce the rows and columns of the binary image filled in S3 by x times, so that the pixel size of the entire format is M*N. Each pixel of the reduced image contains x of the original binary image. 2 pixels, the x 2 Each bright pixel value is 256 / x 2 The data is accumulated; S5: Determine the x 2 Are all pixels bright pixels? If yes, the grayscale value is 255; if x 2 If not all pixels are bright pixels, the grayscale value of the reduced pixel is the accumulated value of the original pixel data; S6: Convert the layer model of the printed model into a grayscale pixel image according to the steps S2-S5; if mean filtering is required for the grayscale pixel image, filter it according to a 3*3 or 5*5 filtering template after the conversion is completed; otherwise, skip S6 directly; S7: Start the projector to perform light curing on the photosensitive resin according to the image data of the current printing layer, and turn off the projector after the curing is completed according to the set curing time, and the printing of the current printing layer is completed; S8: Repeat steps S2-S7 to operate on the next layer of the model contour until the last layer of the model, and then the printing of the printed model is completed.

2. The printing method according to claim 1, wherein: The value of x in step S2 is 4, 6, or 8.

3. The printing method according to claim 1, wherein: The printing method also includes a correction step for correcting the contour expansion caused by image mean filtering. The correction step is located in S6 and is as follows: when performing image mean filtering, if the grayscale value of the pixel position is 0, mean filtering is not performed; if the grayscale value of the pixel position is not 0, mean filtering is performed and the filtered image grayscale value is placed at the position.

4. The printing method according to claim 3, wherein: The correction step is to eliminate the final printing error by scaling the layer profile before binarization in step S2 according to the scaling amount that may be caused by mean filtering and resin curing shrinkage.

5. The printing method according to claim 1, wherein: Step S7 in the printing method further includes: after a certain layer of resin is photocured and in preparation for printing the next layer, turning on an ultrasonic device to vibrate the resin inside the resin tank.

6. The printing method according to claim 5, wherein: The ultrasonic device in step S7 is disposed on the carrier substrate and / or the resin tank support plate of the printer, and ultrasonic energy can be transmitted to the resin tank through the carrier substrate and / or the resin tank support plate to vibrate the resin inside the resin tank.

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