A 3D printing device and its laser positioning accuracy calibration method

Abstract

A 3D printing device and its laser positioning accuracy calibration method are disclosed. The calibration method includes: placing a standard plate with several graphics on a working plane; setting an imaging system at the laser incident end of a galvanometer; keeping the laser off and controlling the galvanometer deflection to scan any position A of each graphic; acquiring an image of the standard plate observed under the reflection of the galvanometer at position A through the imaging system; performing image processing on the standard image; extracting the coordinate values ​​of the positioning patterns at position A of the corresponding graphics using a graphic recognition algorithm; forming an actual matrix with the coordinate values ​​of the positioning patterns corresponding to all graphics in the array; calculating the deviation between the coordinate values ​​of each positioning pattern in the actual matrix and the corresponding target coordinate values ​​in the target matrix; and generating a galvanometer accuracy calibration table using a calibration algorithm. This invention's laser positioning accuracy calibration method for the 3D printing device improves accuracy and is simple to implement.

Description

Technical Field

[0001] This application relates to the field of additive manufacturing technology, and in particular to a 3D printing device and a laser positioning accuracy calibration method thereof. Background Technology

[0002] Laser positioning accuracy calibration is a common problem faced in industrial additive manufacturing applications. Due to the non-linear relationship between the galvanometer angle deflection and the printing plane coordinates, coupled with manufacturing errors in optical components and errors during assembly, galvanometer scanning accuracy calibration is essential to ensure forming accuracy. Solving the calibration problem for laser scanning positioning accuracy is key to improving 3D printing quality and expanding the application range of 3D printing.

[0003] Currently, the laser precision calibration methods used in the industry can be broadly divided into two categories.

[0004] One type of method involves printed image recognition. This method marks the corresponding identification graphics for each laser galvanometer unit onto the surface of an optical printing medium according to a preset array. The optical printing medium panel is pre-placed within the processing area of ​​the printing platform. After printing, an external image acquisition module acquires the printed image on the optical printing medium panel, marking the preset array identification graphics corresponding to each laser galvanometer unit in the image. Then, a software algorithm identifies the actual coordinate information of the array points of the identification graphics corresponding to each laser galvanometer unit in a preset reference coordinate system; the deviation between the theoretical and actual coordinate information of each identification point in the preset reference coordinate system is obtained; and a corresponding calibration file is generated according to a calibration algorithm to correct the galvanometer parameters of each laser galvanometer unit. This method requires a high-cost image acquisition system and more repetitive operations for large-format calibration. The calibration accuracy depends on the medium's surface flatness, uniformity, and other medium quality factors, and it also incurs medium loss, increasing calibration costs.

[0005] Another approach involves placing a precision calibration board composed of photoelectric sensors in the processing area of ​​the printing platform. This calibration board receives low-power laser light emitted from a preset output array via the photoelectric sensor array, converts the laser signal into an electrical signal, and amplifies the different signals generated when the laser position deviates from the ideal position through the design of the photoelectric sensors. Based on this signal, the offset of the actual output position relative to the ideal output position is calculated. Then, according to the calibration algorithm, a corresponding calibration file is generated to correct the galvanometer parameters of each laser galvanometer unit. The cost of this method increases rapidly with the number of lasers and the density of the calibration array, and it also places very high demands on the design of the photoelectric sensors.

[0006] This invention proposes a method for laser position accuracy detection and calibration in 3D printing equipment. A small-field-of-view coaxial CCD image acquisition system is added to a multi-axis galvanometer. The calibration pattern, marked with a high-precision pattern array, is observed on a calibration plate placed on the working plane of the printing platform. After correcting for field distortion and galvanometer nonlinearity errors, the deviation between the calibration pattern information and the theoretical pattern position information is identified. Based on a calibration algorithm, a corresponding calibration file is generated to correct the galvanometer parameters of each laser galvanometer unit. This method uses lower-performance imaging equipment and a more flexible detection optical path, increasing the adaptability of the calibration method to different printing sizes. It eliminates the need for laser output, enabling in-device fine calibration, reducing fine calibration hardware costs, minimizing detection errors, and significantly improving laser accuracy calibration efficiency. It is highly accurate, low-cost, harmless, and widely applicable. Summary of the Invention

[0007] To address the aforementioned technical problems in existing technologies, this invention provides a laser position accuracy calibration method for 3D printing equipment. This calibration method only requires photographing a small area to achieve calibration, reducing the requirements for components and lowering costs. Moreover, this calibration method has high accuracy.

[0008] To achieve the above objectives, the present invention provides a laser positioning accuracy calibration method for 3D printing equipment, comprising the following steps:

[0009] Step S1: Place a standard plate with several patterns arranged in an array on the working plane, deflect the galvanometer to the center position, and move the standard plate so that the central pattern of the standard plate is located at the center of the field of view of the imaging system. The imaging system is set at the laser incident end of the galvanometer.

[0010] Step S2: Keep the laser off, control the galvanometer to deflect to scan any position A of each pattern, and obtain the standard plate image of position A under the reflection of the galvanometer through the imaging system.

[0011] Step S3: Perform image processing on the standard image obtained in step S2 at position A of each graphic, and extract the coordinate values ​​of the positioning pattern by the position A of the corresponding graphic through the graphic recognition algorithm. The coordinate values ​​of the positioning patterns corresponding to all graphics in the array form an actual matrix.

[0012] Step S4: Calculate the deviation between the coordinate value of each positioning pattern in the actual matrix and the corresponding target coordinate value in the target matrix, and generate a galvanometer accuracy calibration table through a calibration algorithm to calibrate the galvanometer.

[0013] As a further preferred embodiment of the present invention, the standard plate is designed with an array of patterns by engraving or coating.

[0014] As a further preferred embodiment of the present invention, the shape of the graphic is a solid circle, a cross, a square, or various patterns composed of them.

[0015] As a further preferred embodiment of the present invention, the imaging system is a CMOS or CCD image acquisition system.

[0016] As a further preferred embodiment of the present invention, the image processing includes image calibration and pixel registration.

[0017] As a further preferred embodiment of the present invention, position A is the center position of the graphic.

[0018] As a further preferred embodiment of the present invention, the target matrix is ​​obtained through the following steps:

[0019] Step A1: Using the optical model composed of the optical system and imaging system of step S1, calculate the required deflection angle of the X and Y galvanometers in the system based on the coordinates of the position A of each graphic in the working plane, and obtain the scanning angle of the beam focused on position A.

[0020] Step A2: Calculate the scanning angle of the boundary beam of the imaging system's field of view based on the above optical model, obtain the coordinates of the edge rays focused on the working plane, and determine the field of view range of the observation image captured by the imaging system at position A.

[0021] Step A3: Based on the positional relationship between the coordinates of position A on the working plane and the coordinates of the boundary beam of the imaging system's field of view, as well as the optical model, calculate the image coordinates of position A on the observed image. Use these coordinates as the target coordinates, and form a target matrix with all target coordinate values ​​in the array.

[0022] As a further preferred embodiment of the present invention, the target matrix is ​​obtained through the following steps:

[0023] Step B1: Place a planar marking plate on the working plane, deflect the galvanometer to the center position, and move the planar marking plate to cover the working area of ​​the galvanometer. The imaging system is set at the laser incident end of the galvanometer.

[0024] Step B2: Use a low-power laser to emit light and control the deflection of the galvanometer to scan the position A of each pattern, and record the observation image generated by the emitted light position through the imaging system;

[0025] Step B3: Perform image processing on the observation images recorded at position A of each graphic obtained in step B2, and extract the center position of the laser emission point in the corresponding image using a graphic recognition algorithm to obtain the target coordinate value. All target coordinate values ​​in the array form a target matrix.

[0026] As a further preferred embodiment of the present invention, the low-power laser is a laser capable of exciting a planar marking plate material and producing a brightness saturation value lower than that of the imaging system, and emitting clear light.

[0027] The present invention also provides a 3D printing device, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the steps of the laser positioning accuracy calibration method of the 3D printing device described in any of the above claims.

[0028] The 3D printing equipment and its laser position accuracy calibration method of the present invention, by adopting the above technical solution, have the following beneficial effects:

[0029] 1. The calibration method of the present invention installs an imaging system at the laser incident end of the galvanometer, so that the standard plate image obtained by the galvanometer under the reflection of the galvanometer can be observed sequentially through the imaging system in real time and coaxially while the galvanometer is deflecting and scanning. Here, only the imaging system needs to have the function of shooting a small area. Therefore, the present invention reduces the requirements for the device and has low cost.

[0030] 2. The calibration method of the present invention includes: placing a standard plate with several patterns on a working plane, setting an imaging system at the laser incident end of a galvanometer; keeping the laser off, controlling the galvanometer to deflect to scan any position A of each pattern, and acquiring an image of the standard plate observed under the reflection of the galvanometer at position A through the imaging system; performing image processing on the standard image, and extracting the coordinate values ​​of the positioning patterns at position A of the corresponding patterns through a pattern recognition algorithm, forming an actual matrix with the coordinate values ​​of the positioning patterns corresponding to all patterns in the array; calculating the deviation between the coordinate values ​​of each positioning pattern in the actual matrix and the corresponding target coordinate values ​​in the target matrix, and generating a galvanometer accuracy calibration table through a calibration algorithm. This calibration method greatly improves the accuracy, and the calibration process is simple. Attached Figure Description

[0031] Figure 1 A flowchart of Embodiment 1 of the laser positioning accuracy calibration method for the 3D printing equipment of the present invention;

[0032] Figure 2 A flowchart of Embodiment 2 of the laser positioning accuracy calibration method for the 3D printing equipment of the present invention;

[0033] Figure 3 The flowchart is for Embodiment 3 of the laser positioning accuracy calibration method for the 3D printing equipment of the present invention. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0035] Example 1

[0036] like Figure 1 As shown, the laser positioning accuracy calibration method for the 3D printing equipment in this embodiment includes the following steps:

[0037] Step 11: Place a standard plate with several patterns arranged in an array on the working plane, and deflect the galvanometer to the center position so that the coordinate position of the galvanometer is zeroed; move the standard plate so that the central pattern of the standard plate is located at the center of the field of view of the imaging system, and the imaging system is set at the laser incident end of the galvanometer; the function of the imaging system is to meet the requirements of high-precision imaging and to be a coaxial imaging system utilizing the reflection characteristics of the galvanometer. In specific implementation, the X-axis and Y-axis of the standard plate are aligned with the coordinate axes of the substrate, and the standard plate is fixed after it is set up; preferably, the imaging system is a CMOS or CCD image acquisition system, wherein the CCD image acquisition system has a lower cost because it only needs to capture a small field of view;

[0038] Specifically, the standard plate is designed with an array of patterns engraved or coated, the patterns being solid circles, crosses, squares, or various patterns composed of them. Of course, other arbitrary shapes are also possible and are not limited here. The size of the array (e.g., (M*N, where M and N are any positive integers) can be determined by the working plane area required for calibration and the spacing between the patterns.

[0039] Step 12: Keep the laser off, control the galvanometer to deflect to scan any position A of each pattern, and obtain the standard plate image observed at position A under the reflection of the galvanometer through the imaging system; position A of each pattern in the array is the coordinate position aimed at during the galvanometer precision calibration scan; the preferred position A is the center position, but in specific implementation, it can also be any part of the pattern, such as the upper left part or the lower left part, etc., which is not limited here;

[0040] Step 13: Perform image processing on the standard images observed at position A of each graphic obtained in Step 12, and extract the coordinate values ​​of the positioning patterns at position A of the corresponding graphic using a graphic recognition algorithm. The coordinate values ​​of the positioning patterns corresponding to all graphics in the array M*N form an actual matrix. This image processing step includes image calibration and pixel registration, which correct graphic distortion and magnification changes generated during imaging. In specific implementations, other existing graphic processing techniques may also be used, which will not be described in detail here. Moreover, the above-mentioned image calibration and pixel registration are conventional techniques in this field, therefore, they will not be described in detail in this application.

[0041] Step 14: Calculate the deviation between the coordinate values ​​of each positioning pattern in the actual matrix and the corresponding target coordinate values ​​in the target matrix, and generate a galvanometer accuracy calibration table using a calibration algorithm to calibrate the galvanometer. The calibration algorithm used in this step is conventional technology in the field; therefore, it will not be described in detail in this application. The function of the calibration algorithm here is to calculate the compensation amount required for galvanometer deflection based on the aforementioned deviation and the galvanometer system parameters.

[0042] Example 2

[0043] like Figure 2 As shown, the laser positioning accuracy calibration method for the 3D printing equipment in this embodiment includes the following steps:

[0044] Step 21: Place a standard plate with several patterns arranged in an array on the working plane, and deflect the galvanometer to the center position so that the coordinate position of the galvanometer is zeroed; move the standard plate so that the center pattern of the standard plate is located at the center of the field of view of the imaging system. The imaging system is set at the laser incident end of the galvanometer; the imaging system is a CCD image acquisition system. Since the CCD image acquisition system only needs to capture a small field of view, the cost is low.

[0045] Step 22: Keep the laser off, control the galvanometer to deflect to scan the center position of each pattern, and obtain the standard plate image of the center position observed by the galvanometer through the imaging system; the center position of each pattern in the array is the coordinate position aimed at during the galvanometer precision calibration scan.

[0046] Step 23: Perform image calibration and pixel registration on the standard image obtained in step 22 by observing the center position of each graphic, and extract the coordinate values ​​of the positioning pattern by the position A of the corresponding graphic through the graphic recognition algorithm. The coordinate values ​​of the positioning patterns corresponding to all graphics in the array form an actual matrix, denoted as Matrix_real.

[0047] Step 24: Using the optical model composed of the optical system and imaging system from Step 21, calculate the required deflection angles of the X and Y galvanometers in the system based on the coordinates of position A of each graphic on the working plane, and obtain the scanning angle of the beam focused on position A.

[0048] Step 25: Calculate the scanning angle of the boundary beam of the imaging system's field of view based on the above optical model, obtain the coordinates of the edge rays focused on the working plane, and determine the field of view range of the observation image captured by the imaging system at position A.

[0049] Step 26: Based on the positional relationship between the coordinates of position A on the working plane and the coordinates of the boundary beam of the imaging system's field of view, and the optical model, calculate the image coordinates of position A on the observed image, and use these coordinates as the target coordinates; all target coordinate values ​​in the array form a target matrix, denoted as Matrix_st;

[0050] Step 27: Calculate the deviation between the coordinate value of each positioning pattern in the actual matrix and the corresponding target coordinate value in the target matrix. The deviation is Matrix_bias = Matrix_real - Matrix_st. Then, generate a galvanometer accuracy calibration table through a calibration algorithm to calibrate the galvanometer.

[0051] Example 3

[0052] like Figure 3 As shown, the laser positioning accuracy calibration method for the 3D printing equipment in this embodiment includes the following steps:

[0053] Step 31: Place a standard plate with several patterns arranged in an array on the working plane, and deflect the galvanometer to the center position so that the coordinate position of the galvanometer is zeroed; move the standard plate so that the center pattern of the standard plate is located at the center of the field of view of the imaging system, and the imaging system is set at the laser incident end of the galvanometer.

[0054] Step 32: Keep the laser off, control the galvanometer to deflect to scan the center position of each pattern, and obtain the standard plate image of the center position observed by the galvanometer through the imaging system; the center position of each pattern in the array is the coordinate position aimed at during the galvanometer precision calibration scan.

[0055] Step 33: Perform image calibration and pixel registration on the standard image obtained in step 32 by observing the center position of each graphic, and extract the coordinate values ​​of the positioning pattern by the position A of the corresponding graphic through the graphic recognition algorithm. The coordinate values ​​of the positioning patterns corresponding to all graphics in the array form the actual matrix, denoted as Matrix_real.

[0056] Step 34: Place a planar marking plate on the working plane, deflect the galvanometer to the center position, and move the planar marking plate to cover the working area of ​​the galvanometer. The imaging system is set at the laser incident end of the galvanometer. This step is actually the same as step 31 above, except that the standard plate in the working plane is replaced with a planar marking plate.

[0057] Step 35: Use a low-power laser to emit light, and control the galvanometer deflection according to the center position of each pattern on the standard plate to scan the planar marking plate (the scanning control program for this step is the same as the scanning control program in step 32 above), and record the observation image generated by the light emission position through the imaging system.

[0058] Step 36: Perform image processing on the observation images recorded at the center position of each graphic obtained in Step 35, and extract the target coordinate values ​​by extracting the center position of the laser emission point in the corresponding image through the graphic recognition algorithm. All target coordinate values ​​in the array form a target matrix, denoted as Matrix_st.

[0059] Step 37: Calculate the deviation between the coordinate value of each positioning pattern in the actual matrix and the corresponding target coordinate value in the target matrix. The deviation is Matrix_bias = Matrix_real - Matrix_st. Then, generate a galvanometer accuracy calibration table using a calibration algorithm to calibrate the galvanometer.

[0060] The calibration steps used in Example 3 and Example 2 are basically the same, and both can achieve accurate calibration of the galvanometer. The difference lies in the method of obtaining the target matrix. The method of obtaining the target matrix in Example 3 is superior to that in Example 2, as it can directly obtain the true position of the target point without calculation error, thus further improving the accuracy of calibration.

[0061] Example 4

[0062] The 3D printing device of this embodiment includes a memory and a processor. The memory stores a computer program, wherein the processor executes the computer program to implement the steps of the laser positioning accuracy calibration method for the 3D printing device described in any of the above embodiments.

[0063] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as the combination of these technical features does not contradict each other, it should be considered within the scope of this specification. The above embodiments only illustrate several implementation methods of this application, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be noted that for those skilled in the art, several modifications and improvements can be made without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A laser positioning accuracy calibration method for a 3D printing device, characterized in that, Includes the following steps: Step S1: Place a standard plate with several patterns arranged in an array on the working plane, deflect the galvanometer to the center position, and move the standard plate so that the central pattern of the standard plate is located at the center of the field of view of the imaging system. The imaging system is set at the laser incident end of the galvanometer. Step S2: Keep the laser off, control the galvanometer to deflect to scan any position A of each pattern, and obtain the standard plate image of position A under the reflection of the galvanometer through the imaging system. Step S3: Perform image processing on the standard image obtained in step S2 at position A of each graphic, and extract the coordinate values ​​of the positioning pattern by the position A of the corresponding graphic through the graphic recognition algorithm. The coordinate values ​​of the positioning patterns corresponding to all graphics in the array form an actual matrix. Step S4: Calculate the deviation between the coordinate values ​​of each positioning pattern in the actual matrix and the corresponding target coordinate values ​​in the target matrix, and generate a galvanometer accuracy calibration table using a calibration algorithm to calibrate the galvanometer; wherein, The target matrix is ​​obtained through the following steps: Step A1: Using the optical model composed of the optical system and imaging system of step S1, calculate the required deflection angle of the X and Y galvanometers in the system based on the coordinates of the position A of each graphic in the working plane, and obtain the scanning angle of the beam focused on position A. Step A2: Calculate the scanning angle of the boundary beam of the imaging system's field of view based on the above optical model, obtain the coordinates of the edge rays focused on the working plane, and determine the field of view range of the observation image captured by the imaging system at position A. Step A3: Based on the positional relationship between the coordinates of position A on the working plane and the coordinates of the boundary beam of the imaging system's field of view, and the optical model, calculate the image coordinates of position A on the observed image. Use these coordinates as the target coordinates, and form a target matrix with all target coordinate values ​​in the array; or The target matrix is ​​obtained through the following steps: Step B1: Place a planar marking plate on the working plane, deflect the galvanometer to the center position, and move the planar marking plate to cover the working area of ​​the galvanometer. The imaging system is set at the laser incident end of the galvanometer. Step B2: Use a low-power laser to emit light, and control the galvanometer deflection according to the position A of each pattern on the standard plate to scan the planar scale plate, and record the observation image generated by the light emission position through the imaging system; Step B3: Perform image processing on the observation images recorded at position A of each graphic obtained in step B2, and extract the center position of the laser emission point in the corresponding image using a graphic recognition algorithm to obtain the target coordinate value. All target coordinate values ​​in the array form a target matrix.

2. The laser positioning accuracy calibration method for 3D printing equipment according to claim 1, characterized in that, The standard plate is designed with an array of patterns by engraving or coating.

3. The laser positioning accuracy calibration method for 3D printing equipment according to claim 1, characterized in that, The shape of the graphic is a solid circle, a cross, a square, or a pattern composed of them.

4. The laser positioning accuracy calibration method for 3D printing equipment according to claim 1, characterized in that, The imaging system is a CMOS or CCD image acquisition system.

5. The laser positioning accuracy calibration method for 3D printing equipment according to claim 1, characterized in that, The image processing includes image calibration and pixel registration.

6. The laser positioning accuracy calibration method for 3D printing equipment according to claim 1, characterized in that, Position A is the center of the graphic.

7. The laser positioning accuracy calibration method for 3D printing equipment according to claim 6, characterized in that, The low-power laser is a laser capable of exciting planar marking materials and producing a brightness saturation value lower than that of the imaging system, while maintaining clear light emission.

8. A 3D printing device, characterized in that, The device includes a memory and a processor, the memory storing a computer program, characterized in that the processor executes the computer program to implement the steps of the laser positioning accuracy calibration method for the 3D printing equipment according to any one of claims 1 to 7.

Images