A leveling method for light-curing 3D printer

Abstract

The present invention discloses a leveling method for a light-curing 3D printer, which belongs to the field of 3D printing technology and is designed to solve the leveling problem in micron-precision 3D printing technology. The specific implementation steps of the method are: the control system outputs the projection pattern to the digital micromirror array, the digital micromirror array reflects the pattern after being irradiated with red light, and projects it onto the resin liquid surface through the microscopic projection light path, the image sensor shoots the projection pattern on the liquid surface, and transmits the collected projection pattern to the computer; the collected picture is digitally processed with the projection pattern, the evaluation value at the position is calculated, and the leveling operation is performed according to the evaluation value. The present invention adopts the method of optical projection and digital image processing for the leveling of the light-curing 3D printer, which can effectively avoid the problem of platform tilt, and has high precision and good leveling effect.

Description

Technical Field

[0001] The present invention belongs to the technical field of 3D printing, and more specifically, relates to a leveling method for a light-curing 3D printer based on a digital image processing method. Background Art

[0002] 3D printing is a manufacturing technology that makes objects by stacking materials in layers. Among them, photocuring is one of the earliest 3D printing technologies. Its principle is based on the light-stimulated polymerization reaction of photosensitive resin, so that the resin can be transformed from liquid to solid. Among them, Digital Light Processing (DLP) is a photocuring 3D printing technology with high precision and high molding efficiency. The core component of photocuring 3D printing technology is the DMD chip. The three-dimensional model is sliced ​​and layered by computer, and the screenshots of each layer of photocuring are obtained and projected by the DMD chip, and the structure of the object is completed by printing layer by layer. Photocuring 3D printing technology is fast and accurate, and is suitable for printing small models with high detail requirements.

[0003] The accuracy of a light-curing 3D printer depends largely on the parallelism between the molding base and the projection imaging focal plane. Low parallelism will reduce printing accuracy and lead to problems such as shape errors in the printed model, so parallelism needs to be leveled. The accuracy of leveling will directly lead to a decrease in the success rate of printing. Currently, most of the leveling mechanisms of light-curing 3D printers on the market use universal balls or three-point screws to level the horizontality between the molding platform and the material box. The leveling situation is determined by the user's feeling or the pressure sensor value after the molding platform and the material box are attached to the ground, but there is a lack of a micron-precision leveling method for directly measuring the parallelism of the molding base and the projection imaging focal plane. Summary of the invention

[0004] In view of the above prior art, the purpose of the present invention is to provide a leveling method for a light-curing 3D printer based on a digital image processing method to solve the leveling problem of the light-curing 3D printer. The leveling method can accurately achieve micron-precision leveling of the theoretical projection imaging focal plane and the actual molding base surface.

[0005] The technical solution adopted by the present invention is as follows:

[0006] A leveling method for a photocurable 3D printer comprises a projection optical path, a control system and a molding device, wherein the molding device comprises a molding bracket and a material box, wherein the material box contains material; the projection optical path comprises a red light source, a digital micromirror array, a first lens, a semi-transparent and semi-reflective element, a reflector, an objective lens, a second lens, and an image sensor, wherein the red light source illuminates the digital micromirror array, the control system controls the digital micromirror array and transmits a projection image to the digital micromirror array, the pattern information reflected by the digital micromirror array is collected via the first lens, and the direction is changed by the reflector after passing through the semi-transparent and semi-reflective element, and then the objective lens forms an image and focuses on the material liquid surface in the material box, the projection imaging information enters the image sensor via the objective lens, the reflector, the semi-transparent and semi-reflective element and the second lens, and the image sensor takes a picture to obtain a projection imaging picture; the control system calculates the imaging clarity of the projection imaging picture and obtains an evaluation value, wherein the evaluation value represents the relative distance between the molding surface and the imaging surface at the current position, the molding bracket is leveled until the evaluation value is the extreme value of the current position, and the extreme values ​​of the evaluation values ​​at multiple positions are adjusted to complete the leveling of the entire plane;

[0007] The step of obtaining the evaluation value of the projected imaging picture includes:

[0008] Step 1: Separate the three color channels of R, G, and B of the received photo, and retain the B channel information of the photo;

[0009] Step 2: Import a mask to extract and save the information of the focus position of the image that only retains the B channel information, where the focus position is the edge position of the contour of the projected pattern;

[0010] Step 3: Introduce the edge detection operator to calculate the gradient change size of the above contour edge position;

[0011] Step 4: Continue collecting after the set time and repeat steps 1 to 3.

[0012] Furthermore, the upper end of the forming bracket is connected to the adjustment platform, the lower end of the forming bracket extends downward into the material box, the forming bracket is leveled by the adjustment platform, the adjustment platform is connected to a lifting device, and the forming bracket moves up and down under the drive of the lifting device.

[0013] Furthermore, the adjustment platform is a universal optical adjustment frame with two adjusters.

[0014] Furthermore, in step 3 of obtaining the evaluation value of the projected imaging picture, the sum of the squares of the gradient changes at intervals of 2 pixels in the x direction is used as the image evaluation value.

[0015] Furthermore, the evaluation value is a gradient change of an edge of a contour of a projection imaging pattern of the projection imaging picture.

[0016] Furthermore, the projection pattern uses a binary image of a simple geometric figure when leveling a large-scale forming bracket, and uses a binary image of a periodic structure when leveling a material liquid level within a single exposure range.

[0017] Compared with the prior art, the present invention has the following advantages:

[0018] (1) The present invention provides a leveling determination method with micron precision, which greatly improves the leveling precision and has a good leveling effect.

[0019] (2) The present invention only requires switching the light source in the original projection light path without introducing other devices, thus simplifying the structure of the device.

[0020] (3) The leveling method of the present invention is simple to operate and only requires judging by checking the calculated value of the control system, which can solve the non-parallelism problem of micron-precision light-curing 3D printing.

[0021] (4) The present invention is also applicable to the detection of the flatness of the resin liquid surface before single exposure curing. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The schematic diagram of the device structure on which the light-curing 3D printer leveling method of the present invention relies, wherein 1-red light source, 2-digital micromirror array, 3-lens one, 4-plane reflector, 5-objective lens, 6-semi-transmissive and semi-reflective element, 7-lens two, 8-image sensor, 9-molding bracket, 10-resin material tank.

[0023] Figure 2 This is an example of a projection pattern of an example of the present invention.

[0024] Figure 3 It is a schematic diagram of the image evaluation value curve based on which the leveling of the present invention is based, wherein point P is the maximum value of the evaluation curve. DETAILED DESCRIPTION

[0025] The present invention is described in detail below with reference to examples. It should be understood that the following specific implementations are only used to illustrate the specific implementation of the present invention and are not used to limit the protection scope of the present invention. All technical solutions under the concept of the present invention belong to the protection scope of the present invention.

[0026] refer to Figure 1, the photocuring 3D printing device used in this example includes a projection optical path, a control system and a molding device, wherein the projection optical path includes a red light source 1, a digital micromirror array 2, a lens 1 3, a semi-transparent and semi-reflective element 6, a plane reflector 4, an objective lens 5, a lens 2 7, and an image sensor 8, wherein the control system controls the digital micromirror array 2 and transmits a projection image to it, wherein the molding device includes a material box (i.e., a resin tank 10, in which a resin liquid is contained) and a molding bracket 9. In this embodiment, the structure of the molding device is specifically that the upper end of the molding bracket 9 is connected to the adjustment platform, and the adjustment platform can adopt a universal optical adjustment frame with two adjusters, and the adjustment platform is connected to a lifting device, and the lower end of the molding bracket 9 extends downward into the resin tank 10, and the molding bracket 9 is leveled by the adjustment platform, and the molding bracket 9 can move up and down under the drive of the lifting device. The red light source 1 in the projection light path illuminates the digital micromirror array 2, and the pattern information reflected by the digital micromirror array 2 is collected by lens 1 3, and after passing through the semi-transparent and semi-reflective element 6, the direction is changed by the plane mirror 4, and then the objective lens 5 forms an image and focuses on the resin liquid surface in the material box 10; the projection imaging information enters the image sensor 8 through the objective lens 5, the plane mirror 4, the semi-transparent and semi-reflective element 6 and the lens 2 7, and the image sensor 8 takes pictures to obtain the projection imaging picture.

[0027] During leveling, the focusing state of the projection pattern of the device is photographed in real time by the image sensor 8, and the photographed photos are transmitted back to the control system. The control system uses a digital image processing method to calculate the image clarity of the projection image, and obtains an evaluation value of the photo, which indicates the distance between the theoretical projection image plane and the actual forming base plane at the current position. The evaluation value is a nearby extreme value representing the coincidence of the two planes. According to the value, the leveling nut is rotated to adjust the forming base plane until the evaluation values ​​at multiple positions reach the extreme values, and the leveling of the entire forming base plane and the theoretical image plane is completed.

[0028] The specific implementation steps of the leveling method of the selected example of the present invention are as follows:

[0029] Under the condition that the projection optical path is in good working condition and the projection plane is kept horizontal, the binary image of a simple geometric pattern is transmitted from the computer to the digital micromirror array chip. Figure 2 , the image size is consistent with the maximum resolution of the digital micromirror array.

[0030] The red light source is turned on, and the transmitted binary image is reflected pixel by pixel by pixel through the digital micromirror array, which is used as a projection mask.

[0031] The forming bracket 9 is mounted on the optical adjustment frame, and the forming bracket 9 is driven by the lifting device to adjust the upper and lower positions until the projection is well focused on the surface of the forming bracket 9.

[0032] The image sensor collects imaging photos of the projection pattern and transmits the photos back to the control system.

[0033] The control system calculates the image clarity of the photo by means of digital image processing and obtains the evaluation value of the photo. The specific steps include:

[0034] Step 1: Separate the three color channels of R, G, and B of the received photo, and retain the B channel information of the photo;

[0035] Step 2: Import a mask to extract and save the information of the focus position of the image that only retains the B channel information, where the focus position is the edge position of the contour of the projected pattern;

[0036] Step 3: Introduce an edge detection operator to calculate the gradient change of the above-mentioned contour edge position. As a preferred example, the sum of the squares of the gradient changes of 2 pixels apart in the x direction is used as the image evaluation value for real-time display;

[0037] Step 4: Continue collecting after the set time and repeat steps 1-3.

[0038] Adjust the leveling knob while observing the photo evaluation value calculated by the computer in real time until the evaluation value reaches Figure 3 The leveling stops at the extreme point P shown in FIG.

[0039] This example adopts the above-mentioned leveling method to provide a leveling judgment method with micron accuracy, thereby avoiding the problem of reduced printing accuracy caused by the molding bracket 9 tilting due to the user's feeling of leveling. In addition, the structure is simple, the leveling operation is convenient, and the leveling effect is good.

Claims

1. A leveling method for a light-curing 3D printer, comprising a projection light path, a control system and a molding device, characterized in that: The molding device comprises a molding bracket and a material box, wherein the material box contains material; the projection optical path comprises a red light source, a digital micromirror array, a first lens, a semi-transparent and semi-reflective element, a reflector, an objective lens, a second lens, and an image sensor, wherein the red light source illuminates the digital micromirror array, the control system controls the digital micromirror array and transmits a projection image to the digital micromirror array, the pattern information reflected by the digital micromirror array is collected via the first lens, and is changed in direction by the reflector after passing through the semi-transparent and semi-reflective element, and then is imaged and focused on the material liquid surface in the material box by the objective lens, the projection imaging information enters the image sensor via the objective lens, the reflector, the semi-transparent and semi-reflective element, and the second lens, and the image sensor is used to take pictures to obtain a projection imaging picture; the control system calculates the imaging clarity of the projection imaging picture and obtains an evaluation value, wherein the evaluation value represents the relative distance between the molding surface and the imaging surface at the current position, and the molding bracket is leveled until the evaluation value is the extreme value of the current position, and the extreme values ​​of the evaluation values ​​at multiple positions are adjusted to complete the leveling of the entire plane; The step of obtaining the evaluation value of the projected imaging picture includes: Step 1: Separate the three color channels of R, G, and B of the received photo, and retain the B channel information of the photo; Step 2: Import the mask to extract and save the information of the focus position of the image that only retains the B channel information, where the focus position is the edge position of the contour of the projected pattern; Step 3: Introduce the edge detection operator to calculate the gradient change size of the above contour edge position; Step 4: Continue collecting after the set time and repeat steps 1 to 3.

2. A leveling method for a light-curing 3D printer according to claim 1, characterized in that: The upper end of the forming bracket is connected to the adjustment platform, the lower end of the forming bracket extends downward into the material box, the forming bracket is leveled by the adjustment platform, the adjustment platform is connected to a lifting device, and the forming bracket moves up and down under the drive of the lifting device.

3. A leveling method for a light-curing 3D printer according to claim 2, characterized in that: The adjustment platform is a universal optical adjustment frame with two adjusters.

4. The leveling method of a light-curing 3D printer according to claim 1, characterized in that: In step 3 of obtaining the evaluation value of the projected imaging image, the sum of the squares of the gradient changes at intervals of 2 pixels in the x direction is used as the image evaluation value.

5. The leveling method of a light-curing 3D printer according to claim 1, characterized in that: The evaluation value is the gradient change size of the edge of the projection imaging pattern contour of the projection imaging picture.

6. The leveling method of a light-curing 3D printer according to claim 1, characterized in that: The projection pattern uses a binary image of a simple geometric figure when leveling a large-scale forming bracket, and uses a binary image of a periodic structure when leveling a material liquid level within a single exposure range.

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