3D printing system and platform leveling method and device thereof

Abstract

The invention provides a 3D printing system and a platform leveling method and device thereof, and the method comprises the steps: irradiating one or more positions of a printing platform through laser generated by a laser device, and collecting an image of an actually measured laser ray at each corresponding position through a camera; aiming at the image of each actually measured laser line, determining pixel difference values respectively corresponding to one or more points on the actually measured laser line according to the actually measured laser line and a preset reference line; performing XYZ absolute coordinate conversion on the basis of pixel difference values corresponding to one or more points on each actually measured laser line and a conversion relation between an XYZ coordinate system and a pixel coordinate system to form printing platform deviation data; and based on the printing platform deviation data, the Z-axis position of the printing platform is compensated. Platform leveling is carried out in a laser scanning mode, the problem that the random repeated positioning difference is large when a contact sensor is used for printing platform leveling is solved, and the platform leveling accuracy and efficiency are improved.

Description

Technical Field

[0001] This application relates to the field of 3D printing technology, and in particular to a 3D printing system and its platform leveling method and apparatus. Background Technology

[0002] In existing 3D printing systems, when leveling and testing the printing platform, the printing platform needs to make physical contact with the contact sensor. During this process, due to the deformation caused by the contact sensor and the printing platform, as well as random repetitive positioning errors caused by factors such as temperature, zero drift of the detection circuit, and gap, the signal triggering timing of the contact sensor is prone to fluctuate within a certain range, resulting in random and unpredictable deviations when the system repeatedly tests the printing platform.

[0003] Currently, the leveling method for printing platforms is as follows: height is detected at different positions on the printing platform using contact sensors, and then a platform curve is fitted based on the height detection results at different positions to level the printing platform. In this method, because the random repetitive positioning error of the existing contact sensors is inconsistent and random, the error generated by each detection in multiple detections is different. The slope curve of the printing platform fitted based on the results of multiple detections is randomly changing, which does not match the actual height of the actual printing platform and has the problem of distortion. Summary of the Invention

[0004] The purpose of this application is to provide a 3D printing system and its platform leveling method and apparatus, which uses laser scanning to level the platform, thereby alleviating the problem of large random repetitive positioning errors when using contact sensors for printing platform leveling, and improving the accuracy and efficiency of platform leveling.

[0005] In a first aspect, this application provides a platform leveling method for a 3D printing system. The method is applied to the 3D printing system, which includes a print head assembly equipped with a laser and a camera, and a printing platform disposed below the print head assembly. The 3D printing system is configured with a transformation relationship between the XYZ coordinate system and the pixel coordinate system. The method includes: irradiating one or more positions on the printing platform with a laser generated by the laser, and acquiring images of measured laser lines at each corresponding position using a camera; for each measured laser line image, determining the pixel difference corresponding to one or more points on the measured laser line based on the measured laser line and a pre-set reference line; performing an XYZ absolute coordinate transformation based on the pixel difference corresponding to one or more points on each measured laser line and the transformation relationship between the XYZ coordinate system and the pixel coordinate system to form printing platform deviation data; and compensating for the Z-axis position of the printing platform based on the printing platform deviation data.

[0006] Secondly, this application also provides a platform leveling device for a 3D printing system. The device is applied to the 3D printing system. The 3D printing system includes: a print head assembly equipped with a laser and a camera, and a printing platform disposed below the print head assembly. The 3D printing system is configured with a transformation relationship between the XYZ coordinate system and the pixel coordinate system. The device includes: a laser line acquisition module, used to irradiate one or more positions of the printing platform with laser generated by the laser, and to acquire images of the measured laser line at each corresponding position through the camera; a pixel difference determination module, used to determine the pixel difference value corresponding to one or more points on the measured laser line based on the measured laser line and a pre-set reference line for each measured laser line image; a deviation data formation module, used to perform XYZ absolute coordinate transformation based on the pixel difference value corresponding to one or more points on each measured laser line and the transformation relationship between the XYZ coordinate system and the pixel coordinate system to form printing platform deviation data; and a deviation compensation module, used to compensate for the Z-axis position of the printing platform based on the printing platform deviation data.

[0007] Thirdly, this application also provides a 3D printing system, which includes: a print head assembly configured with a laser and a camera, and a printing platform disposed below the print head assembly; the 3D printing system is configured with a transformation relationship between the XYZ coordinate system and the pixel coordinate system; the 3D printing system is used to perform the platform leveling method of the 3D printing system as described in the first aspect.

[0008] The 3D printing system and its platform leveling method and apparatus provided in this application are applied to the 3D printing system. The 3D printing system includes a print head assembly equipped with a laser and a camera, and a printing platform disposed below the print head assembly. The 3D printing system is configured with a transformation relationship between the XYZ coordinate system and the pixel coordinate system. In this method, the measured laser line at each irradiation position is first acquired through laser and camera acquisition. Then, combined with a pre-set reference line, the pixel difference value corresponding to one or more points on the measured laser line is determined. Further, absolute coordinate transformation is performed through the transformation relationship between the XYZ coordinate system and the pixel coordinate system to form printing platform deviation data. This data includes the absolute coordinates of multiple points on the measured laser line and the pixel difference value. The Z-axis position of the printing platform is then compensated using the above-mentioned printing platform deviation data, which alleviates the problem of large random repetitive positioning errors when using contact sensors for printing platform leveling, and improves the accuracy and efficiency of platform leveling. Attached Figure Description

[0009] Figure 1 This is a schematic diagram of a platform leveling and testing method in the prior art;

[0010] Figure 2 A schematic diagram of a 3D printing system provided in an embodiment of this application;

[0011] Figure 3 A flowchart of a platform leveling method for a 3D printing system provided in this application embodiment;

[0012] Figure 4 This application provides a schematic diagram of laser position in a pixel coordinate system.

[0013] Figure 5 This application provides a schematic diagram of laser position comparison in a pixel coordinate system.

[0014] Figure 6 A schematic diagram of a sticker model provided in an embodiment of this application;

[0015] Figure 7 This application provides a schematic diagram of the offset between the nozzle and the pixel coordinate center in an embodiment of the present application.

[0016] Figure 8 A schematic diagram of a nozzle-pixel coordinate center offset detection and a first rule model provided in an embodiment of this application;

[0017] Figure 9 This is a schematic diagram illustrating another nozzle-pixel coordinate center offset provided in an embodiment of this application;

[0018] Figure 10 A schematic diagram of a nozzle-pixel coordinate center offset detection and a second rule model provided in an embodiment of this application;

[0019] Figure 11 This is a schematic diagram of a laser irradiation movement process provided in an embodiment of this application;

[0020] Figure 12 This application provides a schematic diagram for calculating the pixel difference of a detection point in an embodiment.

[0021] Figure 13 A schematic diagram illustrating the deviation between an ideal platform and an actual platform provided in this application embodiment;

[0022] Figure 14 A schematic diagram of a scanning reference area provided in an embodiment of this application;

[0023] Figure 15 This application provides a schematic diagram of the laser line movement direction in an embodiment.

[0024] Figure 16 A schematic diagram of a plurality of first scanned images provided for an embodiment of this application;

[0025] Figure 17 This is a schematic diagram of a region image corresponding to multiple scanning reference regions provided in an embodiment of this application;

[0026] Figure 18 A schematic diagram of a pre-defined reference line provided for an embodiment of this application;

[0027] Figure 19 This is a schematic diagram of an interpolation processing area provided in an embodiment of this application;

[0028] Figure 20 A schematic diagram of a pixel coordinate system matrix provided in an embodiment of this application;

[0029] Figure 21 This is a schematic diagram of a platform leveling effect provided in an embodiment of this application;

[0030] Figure 22 This is a structural block diagram of a platform leveling device for a 3D printing system provided in an embodiment of this application. Detailed Implementation

[0031] The technical solutions of this application will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0032] See Figure 1 As shown, in existing printing platform leveling methods, height is detected at multiple points on the printing platform (four are shown in the figure). The height detection result consists of two parts: the actual height value of the printing platform along the Z-axis, plus random repeatability errors caused by factors such as deformation of the contact sensor in contact with the printing platform, temperature, zero drift of the detection circuit, and gaps. Since the random repeatability errors of the contact sensor are different at different detection points on the printing platform, this can lead to a large repeatability error. Consequently, during the leveling process based on the height detection results from different points, the random repeatability errors of the contact sensor are introduced, thus affecting the accuracy of automatic leveling.

[0033] Based on this, embodiments of this application provide a 3D printing system and its platform leveling method and apparatus. Platform leveling is performed via laser scanning, which avoids the distortion of platform fitting results caused by multiple measurements and improves the accuracy of platform leveling. To facilitate understanding of this embodiment, a detailed description of the platform leveling method for a 3D printing system disclosed in this application embodiment will be provided first.

[0034] This application provides a platform leveling method for a 3D printing system, which is applied to a 3D printing system; see also Figure 2As shown, the 3D printing system includes: a print head assembly 13 with a laser 11 and a camera 12 fixedly configured, and a printing platform 14 disposed below the print head assembly 13; the 3D printing system is also configured with a transformation relationship between the XYZ coordinate system and the pixel coordinate system; the specific determination process of the transformation relationship will be described in detail later.

[0035] See Figure 3 The platform leveling method for a 3D printing system provided in the embodiment of this application includes the following steps:

[0036] Step S302: Irradiate one or more positions on the printing platform with the laser generated by the laser, and capture the image of the measured laser line at each corresponding position with a camera;

[0037] Step S304: For the image of each measured laser line, determine the pixel difference value corresponding to one or more points (hereinafter referred to as detection points) on the measured laser line according to the measured laser line and the pre-set reference line;

[0038] In one embodiment, the first coordinate axis of the pixel coordinate system corresponds to the Z-axis in the XYZ coordinate system, and the second coordinate axis corresponds to the Y-axis or X-axis in the XYZ coordinate system; the pixel difference here includes the pixel difference on the Z-axis and the pixel difference on the Y-axis or X-axis, and the specific determination process will be described in detail later.

[0039] Step S306: Based on the pixel difference corresponding to one or more points on each measured laser line and the transformation relationship between the XYZ coordinate system and the pixel coordinate system, perform XYZ absolute coordinate transformation to form printing platform deviation data;

[0040] The printing platform deviation data includes the absolute XYZ coordinates of each detection point and the Z-axis deviation value of the printing platform. This deviation value can be either the pixel deviation in the Z-axis direction or the absolute coordinate deviation in the Z-axis direction. The specific data formation process will be detailed later.

[0041] Step S308: Based on the printing platform deviation data, compensate for the Z-axis position of the printing platform.

[0042] The specific implementation includes the following steps:

[0043] (1) Obtain the first target point on the printing platform to which the nozzle in the printhead assembly is to be moved; the first target point is the target position to which the nozzle will be moved, which has XYZ coordinates; if the platform is not leveled, the distance between the printing platform and the nozzle at the target position may be large or negative, which means that the nozzle will touch the platform and damage the nozzle, seriously affecting the printing effect and quality.

[0044] (2) Based on the platform deviation data, determine the target platform deviation value corresponding to the first target point.

[0045] Based on the XYZ absolute coordinates of the detection points in the platform deviation data, the system searches for the existence of a first target point in the platform deviation data. If so, the Z-direction deviation value of the printing platform corresponding to the first target point in the platform deviation data is determined as the target platform deviation value. If not, the system searches for a specified number of points that are adjacent to the first target point in the platform deviation data. The system then searches for the Z-direction deviation values ​​of the printing platform corresponding to each of the specified number of points, and performs interpolation processing based on these values ​​to determine the target platform deviation value corresponding to the first target point. In this embodiment, the specified number of points includes two points or four points. For the case of four points, bilinear interpolation processing is performed.

[0046] (3) If the Z-axis deviation value of the printing platform is a pixel difference on the Z-axis, then the absolute Z-axis deviation value of the printing platform is determined according to the Z-axis transformation coefficient in the transformation relationship between the XYZ coordinate system and the pixel coordinate system. The Z-axis height of the printing platform is compensated in the system according to the absolute Z-axis deviation value to realize the automatic leveling function of the platform. If the Z-axis deviation value of the printing platform is already a transformed absolute coordinate deviation value, then the platform leveling operation is performed directly.

[0047] The platform leveling method for a 3D printing system provided in this application uses a laser measurement system consisting of a laser and a camera to scan the printing platform. It pre-determines platform deviation data, including the absolute XYZ coordinates and Z-direction deviation values ​​corresponding to one or more detection points on each measured laser line. During actual leveling, this platform deviation data is used to determine the target platform deviation value corresponding to the target point of the nozzle on the platform, thereby performing the platform leveling operation. Because a laser scanning method is used for detection, it alleviates the problem of large random repetitive positioning errors when using ordinary sensors for printing platform leveling, thus improving the accuracy of platform leveling.

[0048] In another embodiment, the calibration process for the transformation relationship between the XYZ coordinate system and the pixel coordinate system is first described in detail:

[0049] See Figure 2As shown, the 3D printing system is configured with an XYZ coordinate system; the print head assembly and the printing platform work together to complete printing in the three XYZ directions. This includes various implementation methods, such as the print head assembly moving on one of the X, Y, and Z coordinate axes, and the printing platform moving on the other two coordinate axes; or the print head assembly moving on two coordinate axes, and the platform moving on another coordinate axis; or both the print head assembly and the printing platform can move on all three coordinate axes; or the print head assembly filling the X or Y axis so that the axis does not move, and the print head assembly and the printing platform moving on the other two coordinate axes, etc.

[0050] The printhead assembly 13 includes a printing material 131 composed of filaments or powder / granules, an extruder 132, a nozzle 133, and an XY-axis assembly (not shown in the figure) for controlling the movement of the printhead assembly. A sensor 15 (such as a strain gauge) is also provided on the printing platform 14. A laser 11 and a camera 12 are fixedly connected to the printhead assembly 13. As the nozzle 133 of the printhead assembly 13 moves, the laser 11 and camera 12 also move accordingly. In this embodiment, the printhead assembly 13 can reciprocate along the XY-axis of the system; the printing platform 14 can reciprocate along the Z-axis of the system. Therefore, the free movement along the XYZ axes constitutes the XYZ coordinate system of the system. In fact, the XY coordinate values ​​of the system refer to the XY coordinate values ​​of the nozzle 133 on the printhead assembly 13.

[0051] The aforementioned laser 11, camera 12, or additional lighting, constitute a laser measurement system. Laser 11 emits a laser beam onto the printing platform 14; camera 12 captures an image of the printing platform 14 under laser illumination, thereby determining the position of the laser line in the image; during camera 12 calibration, if the lighting is insufficient, supplementary lighting can be provided using an additional lighting lamp. The image captured by camera 12 is composed of a matrix of pixel coordinates, corresponding to a pixel coordinate system; the first coordinate axis of the pixel coordinate system corresponds to the Z-axis in the XYZ coordinate system, and the second coordinate axis corresponds to either the Y-axis or X-axis in the XYZ coordinate system; the first and second coordinate axes can be the horizontal and vertical axes of the pixel coordinate system, or they can be the vertical and horizontal axes, respectively.

[0052] Laser 11 must be installed parallel to the X-axis or Y-axis. Figure 2 The image shows the case where laser 11 is parallel to the Y-axis, and the camera 12 is mounted at a different angle. Figure 1 When the laser is rotated 90° while its position remains unchanged, the horizontal and vertical axes of the pixel coordinate system are interchanged. At this point, the horizontal axis corresponds to the Z-axis of the XYZ coordinate system, and the vertical axis corresponds to the Y-axis. When laser 11 is compared to... Figure 1When the installation position is rotated 90° while the camera position remains unchanged, the laser line is parallel to the X-axis, the horizontal axis still corresponds to the Z-axis of the XYZ coordinate system, and the vertical axis corresponds to the X-axis of the XYZ coordinate system. Combined with... Figure 1 The dark gray vertical bars represent the effective travel of the printing platform in the Z direction of the XYZ coordinate system. The light gray vertical bars represent the effective range of the laser measurement system in the XYZ coordinate system. The system can calibrate the camera's pixel coordinate system with the Y-axis (or X-axis) and Z-axis of the XYZ coordinate system and establish a transformation relationship between the two coordinate systems. The specific process is as follows.

[0053] (1) Calibrate the position in the pixel coordinate system and the XYZ coordinate system where Z equals a specified value:

[0054] Specifically, taking a specified value of 0 as an example, the printing platform is controlled to move upward along the Z-axis in the XYZ coordinate system, or the printhead assembly is controlled to move downward along the Z-axis, until the printing platform and the nozzle of the printhead assembly are detected to be in contact, and the current coordinate value on the Z-axis in the XYZ coordinate system is recorded as 0. The printing platform / printhead assembly is then controlled to continue moving downward / upward along the Z-axis in the XYZ coordinate system by a scan height Hc, determining the coordinate position of the laser on the first coordinate axis (i.e., the Z-axis) in the pixel coordinate system of the image currently captured by the camera, corresponding to the position in the XYZ coordinate system where Z equals 0 + Hc. The specified value can also be any position such as ±1, ±2, etc.

[0055] For specific implementation, please refer to Figure 4 As shown, the system selects a point at any location on the printing platform and controls the printhead assembly to move to that point via the XY axis assembly. The mechanical XY coordinates of this point are determined. Then, the printing platform is moved until the Z-coordinate of the XYZ coordinate system reaches a position where Z equals 0. During this movement, when the nozzle surface impacts the printing platform surface, the two surfaces make physical contact. At this point, a sensor fixed to the printing platform can detect this "impact" trigger signal. Upon detecting this "impact" trigger signal, the system immediately stops the Z-axis movement and records the current Z-axis coordinate value. The system considers this value to be the coordinate value where Z equals 0 (in fact, the system redefines the position where Z equals 0; that is, the position where the nozzle surface and the printing platform surface make physical contact is the position where Z equals 0). Based on the current position where Z equals 0, upward movement of the printing platform's Z-coordinate is considered a negative value in the Z-coordinate system, and downward movement is considered a positive value.

[0056] In practical applications, the Z-coordinate of the printing platform needs to be adjusted downwards again to the specific scanning height Hc for laser camera scanning (to avoid interference between the nozzle surface and the platform surface when the nozzle moves in the XY direction, the nozzle surface needs to be a certain distance Hc higher than the printing platform surface when the laser camera scans). After this adjustment, the laser will appear at the center of the pixel coordinates. At this point, it is necessary to read and record the position of the laser line in the pixel coordinate system as it illuminates the printing platform (e.g., ...). Figure 4 The gray "laser" indicates the location. At this point, each pixel containing the laser line represents the XYZ coordinate system Z = 0 + Hc. This completes the location calibration process.

[0057] (2) Calibrate the first transformation coefficient in the first coordinate axis direction of the pixel coordinate system:

[0058] Increase the distance between the printing platform and the printhead assembly by one unit (e.g., 1 mm), and acquire a first image captured by the camera before the distance increase and a second image captured by the camera after the distance increase; detect the pixel change value corresponding to the position of the laser line on the first coordinate axis in the first and second images; determine the pixel change value as the first transformation coefficient in the direction of the first coordinate axis in the pixel coordinate system.

[0059] In practice, if the printing platform is positioned in the XYZ coordinate system where Z equals the specified value plus the scan height, and the pixel coordinate system has already been calibrated to the position where Z equals the specified value plus the scan height, then adjusting the printing platform to increase or decrease the Z coordinate value will cause the laser's position in the pixel coordinate system to move up or down. This upward or downward movement is the deviation from the calibrated position where "Z equals the specified value plus the scan height". By adding this deviation value to the specified Z value in the XYZ coordinate system, the absolute coordinate value of each pixel corresponding to the laser in the XYZ coordinate system can be obtained.

[0060] Taking the first conversion factor as an example with the number of pixels per millimeter, the specific calibration process is as follows: See Figure 5As shown, keeping the printing platform at the laser camera scanning height in the XYZ coordinate system Z = 0 + Hc, for example, adjusting the printing platform downwards by 1mm and recording the pixel difference before and after the movement, i.e., the number of pixels; after the printing platform moves downwards by 1mm, the pixel difference of the laser image before and after the two operations is 6 pixels. Given that the movement distance is 1mm, the number of pixels per millimeter in the Z-axis direction is KZ = 6 ÷ 1 = 6; KZ means that if the pixel difference between the vertical coordinate position relative to the specified Z value and the current depth position after the movement is 6 pixels, then this movement produces a downward position of 1mm in the XYZ coordinate system. At this time, the position of the XYZ coordinate system output by the laser measurement system is Z = (0 + Hc) + 1 - Hc = 1. That is to say, as long as there is a deviation of 6 pixels in each column of the vertical coordinate, it means that the current printing platform has moved downwards by 1mm, i.e., the output mechanical coordinate Z = (0 + Hc) + 1 - Hc = 1. Because it is easy to interfere with the model during scanning, it is necessary to offset by a scanning height. The actual output coordinate is obtained by subtracting the scanning height.

[0061] The laser measurement system uses the mechanical coordinate Z as a reference, which equals a specified value plus the scanning height, to detect the height in the Z direction. The system outputs the coordinates of the Z direction in the XYZ coordinate system. Within the effective measurement range (ML), the depth measurement is performed and superimposed on the XYZ coordinate system. The formula for the measurement range of the Z axis of the output XYZ coordinate system is: Z = 0 + Hc ± 0.5 * ML.

[0062] It should be noted that the calibration process described above, besides moving the printing platform to induce one or more displacements, can also be achieved by illuminating a contour block with a laser or by taking a picture of the calibration label. When the printing platform moves to a certain height along the Z-axis, the laser measurement system can maintain the same height for imaging, or it can lower the printing platform to take a picture. This section mainly explains the method of taking pictures at the same height. In practical applications, it is necessary to lower the printing platform to take pictures. That is to say, the Z-axis height for laser imaging must be higher than the surface of the printing platform. The purpose of this is to prevent the nozzle from interfering with the measured object on the surface of the printing platform during laser camera positioning. Therefore, the nozzle surface must be higher than the surface of the measured object during imaging.

[0063] (3) Calibrate the second transformation coefficient in the second coordinate axis direction of the pixel coordinate system:

[0064] The camera captures images of a specified model on the printing platform; the specified model includes at least two points along the second coordinate axis; the captured images are identified to determine the pixel values ​​between the centers of the two points; the pixel values ​​are divided by the distance between the centers of the two points to obtain the second transformation coefficient along the second coordinate axis in the pixel coordinate system.

[0065] The following explanation uses the calibration of the number of pixels per millimeter along the Y-axis in the pixel coordinate system as an example: In practice, the horizontal coordinate of the laser measurement system's pixel coordinate system is calibrated, that is, the correspondence between the length of the laser's horizontal coordinate in the pixel coordinate system and its actual length in the Y-direction of the XYZ coordinate system is determined. Based on this correspondence, the pixel reference point position, and the offset on the horizontal coordinate in the pixel coordinate system, the pixel coordinate system can be converted into the XYZ coordinate system, thereby enabling the system to output absolute coordinates.

[0066] The specific calibration process is as follows: The system uses a camera to capture images, either photographing or scanning the outer contour of a target at a known fixed distance at a scanning height, such as... Figure 6 The sticker shown is affixed to a printing platform. For example, the horizontal or vertical center distance between any two dots in the image is 5mm. A camera photographs the sticker to obtain an image. By identifying the dots in the image, the pixel difference between the centers of any two horizontally arranged dots is calculated. For example, if the calculated pixel difference is 30, and the distance between the horizontally arranged center difference and the actual center is 5mm, then the number of pixels per millimeter in the Y-axis direction is KY = 30 ÷ 5 = 6. KY means that if the measured object has a pixel difference of 6 pixels in the horizontal direction of the pixel coordinate system, then the measured object has a length of 1mm in the Y-direction of the XYZ coordinate system. This achieves the function of converting pixel difference into actual length.

[0067] (4) Calibrate the first offset of the pixel reference point in the pixel coordinate system from the nozzle of the printhead assembly in the Y-axis direction:

[0068] A first regular model is printed on the printing platform through the nozzle of the printhead assembly. The first regular model can be a model of various shapes such as rectangle, trapezoid, and rhombus. The Y coordinate of the nozzle center is adjusted so that the Y coordinate of the nozzle center corresponds to the center position of the first regular model, and the first Y coordinate corresponding to the nozzle center is obtained. The X coordinate of the nozzle center is adjusted so that the X coordinate of the laser line position in the image captured by the camera is aligned with the horizontal center point of the first regular model, and the second Y coordinate corresponding to the laser center is recorded. The difference between the first Y coordinate and the second Y coordinate is calculated to obtain the first offset of the pixel reference point in the pixel coordinate system and the nozzle of the printhead assembly in the Y-axis direction.

[0069] In practice, since the laser measurement system is mounted and fixed on the printhead assembly, it is inevitable that the nozzle and pixel coordinate center positions on the printhead assembly will deviate in the Y direction. This deviation is called manufacturing deviation. Figure 7As shown, the gray line on the left of the image represents the laser line, and the black dot at the center of the line corresponds to the black dot on the right, representing the pixel center position. The left side of the image shows the offset ΔY of the nozzle center and the pixel coordinate center in the Y direction of the XYZ coordinate system.

[0070] In this embodiment, the pixel coordinate center is used as the pixel reference point. Taking a rectangular model as an example, the specific calibration process is as follows:

[0071] ① The system prints a rectangular model of a specified height using a nozzle; ② Then, it adjusts the Y-coordinate of the nozzle center so that the nozzle's Y-coordinate is exactly at half the length L of the rectangular model; ③ Then, it adjusts the X-axis coordinate so that the X-coordinate of the laser line position in the image captured by the camera is aligned with the horizontal center point of the rectangular model, such as... Figure 8 As shown, the laser line divides the model into two symmetrical halves. The right side of the figure shows the effect of the laser illuminating the rectangular model. ④ Calculate half the distance L between the centers of the two contours of the laser illuminating the model, and subtract half the total laser length L1. The difference between these two values ​​gives the offset ΔY between the nozzle center and the pixel coordinate center.

[0072] By calculating ΔY using calibration methods, the nozzle center in the XYZ coordinate system can be aligned with the pixel coordinate center. This allows for direct coordinate system transformation. If the nozzle center is slightly above the pixel coordinate center in the horizontal direction, it indicates a positive offset in the Y direction (ΔY). Conversely, it indicates a negative offset in the Y direction (ΔY).

[0073] (5) Calibrate the second offset of the pixel reference point in the pixel coordinate system and the nozzle of the printhead assembly in the X-axis direction: Print a second regular model on the printing platform using the printhead assembly; the second regular model can be a centrally symmetrical pattern with the largest diameter at its center point along the scanning direction, such as a rhombus, ellipse, or circle. Adjust the Y-axis coordinate of the printhead assembly to offset the current Y-axis by a first offset; adjust the X-axis coordinate of the printhead assembly according to a preset distance, and capture images of the laser scanning second regular model after each adjustment using a camera; find the target image from multiple images where the laser line passes through the center point of the second regular model; determine the first X-axis coordinate corresponding to the laser line and the second X-axis coordinate corresponding to the nozzle center from the target image; calculate the difference between the first X-axis coordinate and the second X-axis coordinate to obtain the second offset of the pixel reference point in the pixel coordinate system and the nozzle of the printhead assembly in the X-axis direction.

[0074] The following explanation uses the pixel coordinate center as the pixel reference point and a circular model with a known diameter as an example: In practice, since the laser measurement system is mounted and fixed on the printhead assembly, it is inevitable that the nozzle on the printhead assembly will deviate from the pixel coordinate center in the X direction. This deviation is the manufacturing deviation. Figure 9 As shown in the figure, the distance indicated by the double arrows is the offset ΔX between the nozzle and the center position of the pixel coordinates; for example, in engineering, this deviation will produce a deviation of 10mm±2mm under assembly deviation, and fluctuate within this range.

[0075] like Figure 10 As shown, the calibration process is as follows: ① The system prints a circular model of known diameter with a height using a nozzle, for example, a diameter of 15mm; ② Adjust the XY coordinate values ​​of the print head and offset the Y coordinate by a calibration value of ΔY (as in step (4) above, so that the horizontal coordinate of the camera pixel coincides with the center of the circle), so that the nozzle moves to the center coordinate of the model and records the current coordinate; ③ Then start the camera and laser and move the print head assembly in the X direction by a fixed distance D, combined with the above ΔX fluctuating within the range of 10mm±2mm, for example, each movement D=0.1mm, then a total of 10 / 0.1=100 movements are required. The laser and camera scan the printed circular model. A laser image is taken once for each movement, for a total of 100 images, and the images are numbered; ④ Calculate the diameter value of the model illuminated by the laser in each image. When the model diameter is detected to be 15mm-14.6mm, the system considers the coordinates corresponding to the current image number to coincide with the center of the pixel coordinates. The offset of the pixel coordinate center from the center of the nozzle ΔX=current image number*0.1mm.

[0076] It should be noted that the pixel coordinate center mentioned above is the same as the pixel center point corresponding to the laser line in the image. Figure 10 In the diagram, black circles represent the printed circular model, dashed circles represent the trajectory of the nozzle moving to the left at a certain distance, such as 0.1mm, and vertical lines represent the trajectory of the laser line. The trajectories are numbered from right to left in ascending order. Due to space limitations, not all trajectories can be drawn; they are only used here to more clearly illustrate the specific movement process.

[0077] (6) Based on the calibration position where Z equals the specified value, the first transformation coefficient, the second transformation coefficient, the first offset, and the second offset, determine the transformation relationship between the XYZ coordinate system and the pixel coordinate system:

[0078] In practice, the transformation relationship between the nozzle's XY coordinates and the pixel reference point's XY coordinates can be determined based on the first offset and the second offset. For example, in the XYZ coordinate system, the coordinates corresponding to the nozzle are X1 and Y1, and the coordinates corresponding to the printing platform are Z1. Based on the first offset ΔY1 between the pixel reference point and the nozzle of the printhead assembly in the Y-axis direction, and the second offset ΔX1 between the pixel reference point and the nozzle of the printhead assembly in the X-axis direction, the X and Y coordinates of the pixel reference point (X2, Y2, Z2) can be determined as: X2 = X1 + ΔX1; Y2 = Y1 + ΔY1.

[0079] Furthermore, based on the calibration position where Z equals a specified value, the first conversion coefficient, and the second conversion coefficient, the conversion relationship between the YZ / XZ coordinates of any laser point in the camera image and the YZ / XZ coordinates of the pixel reference point can be determined.

[0080] After pre-calibrating the position where Z equals a specified value, the Z coordinate corresponding to the pixel reference point is the Z coordinate corresponding to the printing platform, i.e., Z2 = Z1. In other words, the mechanical coordinates corresponding to the pixel reference point are: X2, Y2, Z2. Based on this, and according to the first and second conversion coefficients, the conversion relationship between the YZ coordinates of any laser point in the camera image and the YZ coordinates of the pixel reference point can be determined. Taking the ZY coordinates corresponding to the pixel coordinate system as an example, if the distance between the target laser point and the pixel reference point is 12 pixels in the Y direction and 12 pixels in the Z direction, the first unit millimeter in the Z-axis direction has 4 pixels, and the second unit millimeter in the Y-axis direction has 6 pixels; this is equivalent to the target laser point being offset by 12 / 6 = 2 millimeters in the Y direction and 12 / 4 = 3 millimeters in the Z direction from the pixel reference point. Since the X coordinate is consistent with the pixel reference point coordinate, the coordinates corresponding to the target laser point are: X3 = X2; Y3 = Y2 + 2; Z3 = Z3 + 3.

[0081] Therefore, based on the transformation relationship between the nozzle XY coordinates and the pixel reference point XY coordinates, and the transformation relationship between the YZ / XZ coordinates of any laser point and the pixel reference point YZ / XZ coordinates in the camera image, the transformation relationship between the XYZ coordinate system and the pixel coordinate system can be determined.

[0082] After establishing the transformation relationship between the XYZ coordinate system and the pixel coordinate system, the platform deviation data is further determined through laser scanning for subsequent platform leveling reference. In this embodiment, the platform deviation data is illustrated using a platform deviation netlist as an example, and its specific determination process is as follows:

[0083] (1) The laser generated by the laser is used to illuminate one or more positions of the printing platform, and the image of the measured laser line at each corresponding position is captured by the camera.

[0084] In practice, a movable printhead assembly, equipped with a camera and laser, illuminates the printing platform with a laser. In this embodiment, a laser line parallel to the Y-axis is used, following the... Figure 11 The path shown in the right figure is used for moving illumination, targeting the moving process ( Figure 11 Each laser line in the left figure can be identified by capturing images from a camera, thus determining the corresponding measured laser line in the image, which is the measured laser line in the pixel coordinate system.

[0085] Figure 11 The gray lines represent the laser lines illuminating the printing platform. The black dots within the gray lines represent the center positions in the corresponding pixel coordinate system. The dashed lines in the right image represent the movement path of the laser lines. It can be seen that this movement path starts from the "start" position and scans from left to right and from bottom to top (but is not limited to this movement method), ending at the "end" position. The pixel coordinate center (black dot) positions on each row or column of the laser in the image correspond to the same Y-axis or X-axis coordinates. Therefore, based on the parallel or perpendicular relationship between the laser and the X and Y axes, the X and Y coordinate data of these laser lines based on the pixel coordinate center positions are stored in the system.

[0086] (2) For each measured laser line image, determine the pixel difference corresponding to one or more detection points on the measured laser line according to the measured laser line and the pre-set reference line;

[0087] For any detection point on the measured laser line, determine the second target point corresponding to the detection point on a pre-set reference line in the direction of the first coordinate axis; determine the pixel difference between the detection point and the second target point in the direction of the first coordinate axis (Z axis), and the pixel difference between the detection point and the pixel reference point on the pre-set reference line in the direction of the second coordinate axis (X axis or Y axis).

[0088] The distribution of the selected detection points on the printing platform corresponding to each laser line in the movement path is as follows: Figure 12 As shown in the left figure. Figure 12 As shown in the right-middle figure, the upper laser line is a pre-defined reference line (corresponding to an ideal planar curve); the lower laser line is a measured laser line in the moving path (corresponding to the actual platform plane); the XY coordinates of the pixel center positions (shown as black dots in the figure) in the reference line and the measured laser line are consistent. The XY coordinates of other positions in the measured laser line can be calculated using the transformation relationship between the XYZ coordinate system and the pixel coordinate system. By comparing the two lines on the first coordinate axis (Z-axis) of the pixel coordinate system, the pixel difference in the Z direction corresponding to any detection point in each laser line can be determined.

[0089] The pre-defined reference line can be any measured laser line at a specified location, with known XYZ coordinates. However, this method places high demands on the installation of the measured laser line, requiring it to be as parallel as possible to the axis to which parallelism is required.

[0090] The pre-defined reference line can also be obtained using the following method, which has lower requirements for the installation of the measured laser line: A prerequisite for the fitting process is to complete the transformation between the XYZ coordinate system and the pixel coordinate system, combined with... Figure 13 As shown, the "ideal plane" is formed by the set of trajectory lines generated by the nozzle surface moving in any direction along the XY axis. Any position on this "ideal plane" is absolutely parallel and completely coincident with the nozzle surface. If, during calibration, this "ideal plane" is positioned at the same height along the Z-axis in the XYZ coordinate system as the position Z=0 in the pixel coordinate system, then the height coordinate of the "ideal plane" in the Z-direction is equivalent to Z=0. To avoid interference between the nozzle surface and the platform surface when the nozzle moves in the XY direction, the nozzle surface needs to be a distance Hc above the printing platform surface when the laser camera captures the scan. Therefore, the Z-coordinate of the printing platform needs to be adjusted downwards to the specific height Hc required for laser camera scanning. Thus, the laser at each pixel represents the XYZ coordinate system Z=0+Hc. This completes the position calibration process.

[0091] 1) The laser emitted by the laser is used to scan the scanning reference area on the printing platform at least once, and at least one scanning image is captured by a camera during the laser scanning process;

[0092] In practice, the laser irradiates a laser line segment at a preset distance on the printing platform. Starting from one end of the laser line segment contacting the edge of the scanning reference area, the laser line is aligned with the edge of the scanning reference area and scanned in the direction parallel to the laser line assembly requirements, which is the Y-axis in this embodiment. The current scanned image is captured by the camera. Corresponding images are captured at set intervals between the laser lines, such as 0.5mm. The laser moving scan and image acquisition steps are as follows: the position of the laser line is controlled to move at the interval between the laser lines and the scanning reference area. The moved laser line is used to scan the scanning reference area, and the scanned image after the current scan is captured by the camera. The laser moving scan and image acquisition steps are continued until the other end of the laser line leaves the scanning reference area.

[0093] In practice, since Z=0 is the point where the nozzle physically contacts the printing platform (for ease of calculation, this point is set as a small scanning reference area), the calibration point Z=0 is the only point where the ideal plane and the printing plane coincide (because the height coordinate of the "ideal plane" in the Z direction of the XYZ coordinate system is Z=0). The laser can be moved to this calibration point, and different laser positions can be used to scan this calibration point in the Y direction. The laser positions scanned at these positions are then recorded.

[0094] In practical applications, depending on the detection capability, when using a laser line to scan the reference region at Z=0 for fitting, one point or multiple points can be scanned; that is, one scan image or multiple scan images can be acquired. This embodiment describes the method of scanning multiple points with a laser line.

[0095] The Z=0 calibration point is used as the laser scanning reference area, as follows: Figure 14 As shown, a small local area is set on the printing plane as a laser scanning reference area, using the center of this calibration point as a reference. For example, a square area with a side length of 2mm is drawn with this calibration point as the center, serving as the reference area for laser line scanning. Here, a square is used as an example. In practice, scanning is performed on a small local area on the printing platform, rather than a large scanning reference area. The main purpose is to minimize the influence of the inclined surface of the scanning reference area on the laser line. If a small point (a small local area) is selected on the printing platform, the system considers this point not to be a plane. Since it is a point, its height is a constant value, and there is no tilt in the Z-axis direction. This point has only one unique height Z=0 on the Z-axis, and this scanning reference area coincides with the ideal plane. This point is both a point on the actual plane of the printing platform (Z=0) and a point on the ideal plane (Z=0). Scanning this scanning reference area with a laser in the Y-axis direction is equivalent to scanning with a laser on the ideal plane.

[0096] This laser scanning reference area can be defined as any shape, such as a circle, for ease of calculation; here it is defined as a square for ease of description.

[0097] When scanning the reference area with a laser, the system begins by aligning the rightmost point of the laser in the camera's pixel coordinate system with the right edge of the reference area. The X-coordinate of the center of the reference area is then aligned with the center of the pixel coordinate system in the X-direction. While maintaining the X-axis coordinate, the Y-axis coordinate is moved a certain distance, and the laser is used to scan the reference area along the Y-axis until the leftmost point of the laser coincides with the left edge of the reference area (this is not the only method; other methods can also be used from left to right). Figure 15 As shown; the reference area scanning operation is now complete. In the figure, the box represents the camera image, the black line is the laser line, the gray square is the laser scanning reference area, and the gray dashed line is the movement trajectory of the center point of the pixel coordinate system.

[0098] The smaller the distance the coordinates move along the Y-axis, the smaller the scanning reference area, and the higher the detection accuracy. For ease of explanation, let's illustrate with an example: define a square with a laser scanning point side length of 2mm. Align the X-coordinate of the center of the scanning reference area with the center of the pixel coordinates in the X direction. Use the laser to scan the reference area, moving it along the Y-axis at 0.5mm intervals until the scanning reference area is at the rightmost end of the laser beam in the pixel coordinate system. The entire scanning process is as follows: Figure 16 As shown in the figure; the box represents the camera image, the black line is the laser line, the gray square is the laser scanning reference area, and the gray dashed line is the movement trajectory of the center point of the pixel coordinate system. The numbers in the figure indicate the sequential numbering of the images captured by the laser scanning the reference area from the rightmost to the leftmost side at intervals of 2mm in the Y direction. Image number 1 represents the rightmost side of the laser, and image number 10 represents the leftmost side. At this point, the laser scanning operation of the reference area is complete, and the images are saved in the system.

[0099] 2) Identify at least one region image corresponding to the scanning reference region in the first scan image, and detect the corresponding laser line segment in each region image; after completing the above operations, the image generated by the operation can be cropped according to the number of the overlapping part of the laser and the scanning reference region, and the redundant parts are deleted. The effect is as follows: Figure 17 As shown in the figure, the part of the laser local area that overlaps with the scanning reference area at each different position in the figure is the position of the laser on the ideal plane; it can also be understood that the part of the laser local area that overlaps with the scanning reference area at each different position in the figure is the position of the laser on the actual plane of the printing platform Z=0; the calibration point of the laser scanning reference area on the ideal plane and the actual plane of the printing platform Z=0 are absolutely and completely coincident.

[0100] 3) Fit the data based on at least one detected laser line segment to obtain a pre-defined reference line. If only one laser line segment is detected, fit the data based on the laser line segment to determine the pre-defined reference line; if multiple laser line segments are detected, stitch the multiple laser line segments sequentially according to the scanning direction to obtain the pre-defined reference line.

[0101] Based on the results of the previous step, if we fit the local images of lasers illuminating the ideal plane at different positions to a pre-defined reference line, i.e., the ideal plane curve, then this ideal plane curve represents the actual position of the laser in the camera's pixel coordinate system when the laser scans at any position on the ideal plane. The tilt angle of the laser is the same at any position on the ideal plane, therefore only one ideal plane curve is needed as a reference line. Simultaneously, this curve also represents the position of the laser in the pixel coordinate system after scanning the ideal plane, considering the interaction of parallelism deviations generated during the assembly and manufacturing process between the laser, camera, and Y-coordinate. Figure 18 As shown by the medium-thick dashed line; the system fits this curve and saves its pixel coordinates. At this point, the ideal planar curve fitting is complete, which means the pre-defined reference line is obtained. Figure 18 As shown by the thick dashed line.

[0102] (3) Based on the pixel difference corresponding to one or more detection points on each measured laser line and the transformation relationship between the XYZ coordinate system and the pixel coordinate system, the XYZ absolute coordinate transformation of the detection points is performed to form the printing platform deviation data.

[0103] For example, when collecting the current measured laser line, the position coordinates of the nozzle on the platform are (X1, Y1, Z1). Further, based on the first offset △Y1 and the second offset △X1 in the coordinate system transformation relationship, the coordinates of the pixel reference point (generally the center of the laser pixel) on the pre-set reference line can be determined as (X2 = X1 + △X1, Y2 = Y1 + △Y1, Z1). Further, based on the pixel difference between the detection point and the pixel reference point on the pre-set reference line on the second coordinate axis (taking the Y axis as an example, it can also be the X axis), and the second transformation coefficient of the second coordinate axis in the coordinate system transformation relationship, the absolute coordinates (X2, Y3, Z1) corresponding to the detection point can be determined. In addition to storing the XYZ coordinates corresponding to the detection point, the platform deviation data also stores the Z-direction deviation value of the printing platform corresponding to that point. The Z-direction deviation value of the printing platform can be either the Z-axis pixel deviation or the Z-axis absolute coordinate deviation. The Z-axis absolute coordinate deviation can be obtained by converting the Z-axis pixel deviation and the coordinate system. In this way, the platform deviation value corresponding to each current point can be determined by data lookup or interpolation fitting.

[0104] For points that can be directly located, the printing platform can be leveled directly based on the Z-direction deviation value of the corresponding point. For points that cannot be directly located, the deviation data of nearby points can be fitted to obtain the corresponding Z-direction deviation value of the printing platform, and then the platform can be leveled using the method described above. The specific process is as follows:

[0105] In the previous step, the Z-axis pixel difference values ​​corresponding to multiple detection points on each measured laser line were determined. Since the matrix scanning has a certain spacing D, such as... Figure 19 As shown, it's impossible to calculate and store all pixel differences on the same scan line, as this would consume a lot of memory. Therefore, in this embodiment, for points not stored in the netlist, their corresponding pixel differences are determined by linear interpolation using the pixel differences of multiple nearby points, such as... Figure 19 As shown, for a point in the blank area in the X and Y directions, the coordinates and pixel difference of its four nearest neighbors can be obtained. Then, the pixel difference corresponding to the point in the blank area can be determined by linear interpolation.

[0106] In another implementation, the pixel differences corresponding to multiple detection points in the blank area can be determined in advance by linear interpolation, and these values ​​can also be saved in the platform deviation netlist. This can reduce the number of calculation steps when determining the target platform deviation of the first target point, thereby improving efficiency.

[0107] During the printing process of the printhead assembly, the system can compensate for the platform deviation at any position on the platform based on the platform deviation netlist, achieving the function of "automatic leveling".

[0108] Here is a specific example:

[0109] See Figure 20 As shown, the camera's pixel coordinate system has 1280 pixels on the horizontal axis and 1080 pixels on the vertical axis. Therefore, when detecting the height of the printing platform, 1280 height values ​​can be obtained at once. If multiple heights need to be detected at different locations on the printing platform, the process can be summarized as: one-point multi-point, meaning that scanning a single point on the printing platform with a laser can generate multiple height values, such as... Figure 20 The example shown can generate 1280 height coordinates per scan at one location. Therefore, in the platform leveling detection process provided in this application embodiment, the Z-axis height generated by one XY positioning is 1280 times that of the prior art. This results in a denser number of Z-axis height positions for the printing platform height detection points, leading to higher accuracy in printing platform leveling detection. If more sampling points for the printing platform's Z-axis height are needed, simply increase the resolution of the camera's pixel coordinate system.

[0110] Because there is no physical contact between the laser and the printing platform when scanning, there is no random repetitive positioning error caused by factors such as deformation. Figure 21The leveling test results shown demonstrate that the system uses a laser to detect the leveling at four different points on the actual printing platform. The image below shows the platform tilt detected by the laser; the curve is almost a straight line and parallel to the printing platform. Therefore, the tilt of the printing platform detected by the system is very close to the actual situation, with minimal distortion.

[0111] The platform leveling method for a 3D printing system provided in this application embodiment uses a laser measurement system composed of a laser and a camera to scan the printing platform. Based on multiple measured laser lines after scanning and a pre-set reference line, a platform deviation netlist is determined, including platform deviation values ​​corresponding to one or more detection points on each laser line. During specific leveling, the target platform deviation value corresponding to the first target point on the platform corresponding to the nozzle is found through this platform deviation netlist. If it cannot be found, the target platform deviation value corresponding to the first target point is determined by fitting based on the coordinates and pixel differences of neighboring points using linear interpolation, and then the platform is leveled. Since a laser scanning method is used for detection, the problem of large random repetitive positioning errors when using ordinary sensors for printing platform leveling is alleviated, and the platform leveling accuracy is improved.

[0112] Based on the above method embodiments, this application also provides a platform leveling device for a 3D printing system. The device is applied to the 3D printing system; the 3D printing system includes: a print head assembly with a laser and a camera fixedly configured, and a printing platform disposed below the print head assembly; the 3D printing system is configured with a transformation relationship between the XYZ coordinate system and the pixel coordinate system; see [link to previous document]. Figure 22 As shown, the device includes: a laser line acquisition module 202, used to illuminate one or more positions of the printing platform with laser generated by the laser, and to acquire images of the measured laser line at each corresponding position using the camera; a pixel difference determination module 204, used to determine the pixel difference corresponding to one or more detection points on the measured laser line based on the measured laser line and a pre-set reference line for each measured laser line image; a deviation data formation module 206, used to perform XYZ absolute coordinate transformation based on the pixel difference corresponding to one or more points on each measured laser line and the transformation relationship between the XYZ coordinate system and the pixel coordinate system, to form printing platform deviation data; and a deviation compensation module 208, used to compensate the Z-axis position of the printing platform based on the printing platform deviation data.

[0113] Furthermore, the aforementioned device also includes a setting module, used to perform the aforementioned setting process of the pre-set reference line. Furthermore, the setting module is also used to perform the aforementioned calibration process of the transformation relationship between the XYZ coordinate system and the pixel coordinate system.

[0114] Furthermore, the aforementioned deviation compensation module 208 is also used to obtain the first target point to be moved to on the printing platform corresponding to the nozzle in the printhead assembly; based on the printing platform deviation data, determine the target platform deviation value corresponding to the first target point; if the target platform deviation value is the Z-axis pixel difference, then based on the target platform deviation value corresponding to the first target point and the transformation relationship between the XYZ coordinate system and the pixel coordinate system, determine the Z-axis absolute coordinate deviation value corresponding to the printing platform, and compensate the Z-axis height of the printing platform in the system according to the Z-axis absolute coordinate deviation value to realize the automatic leveling function of the platform.

[0115] Furthermore, the printing platform deviation data includes: the absolute XYZ coordinates of multiple points on the measured laser line and the Z-direction deviation value of the printing platform; the aforementioned deviation compensation module 208 is also used to search for the existence of a first target point in the platform deviation data based on the absolute XYZ coordinates of multiple points on the measured laser line; if yes, the Z-direction deviation value of the printing platform corresponding to the first target point in the platform deviation data is determined as the target platform deviation value; if no, a specified number of points adjacent to the first target point are searched in the platform deviation data; and the Z-direction deviation values ​​of the printing platform corresponding to the specified number of points are searched, and linear interpolation is performed based on the Z-direction deviation values ​​of the printing platform corresponding to the specified number of points to determine the target platform deviation value corresponding to the first target point.

[0116] Furthermore, the first coordinate axis of the aforementioned pixel coordinate system corresponds to the Z-axis in the XYZ coordinate system, and the second coordinate axis corresponds to the Y-axis or X-axis in the XYZ coordinate system; the pixel difference determination module 204 is used to determine, for any point on the measured laser line, a second target point corresponding to the point on the measured laser line on a pre-set reference line in the direction of the first coordinate axis; determine the pixel difference between the point on the measured laser line and the second target point in the direction of the first coordinate axis, and the pixel difference between the point on the measured laser line and the pixel reference point on the pre-set reference line in the direction of the second coordinate axis.

[0117] Furthermore, the aforementioned setting module is also used to scan the edge of the scanning reference area, starting from one end of the laser line contacting the edge of the scanning reference area, with the scanning direction being parallel to the laser line assembly requirements, and to acquire the current scanned image through a camera; to capture corresponding images at set scanning reference area distance intervals, performing the following laser moving scan and image acquisition steps: controlling the position of the laser line to move the scanning reference area distance interval, using the moved laser line to scan the scanning reference area, and acquiring the scanned image after the current scan through a camera; continuing to execute the laser moving scan and image acquisition steps until the other end of the laser line leaves the scanning reference area.

[0118] Furthermore, the aforementioned setting module is also used to determine a pre-set reference line based on the laser sub-segment if the detected laser sub-segment is a single segment; and to stitch the multiple laser sub-segments together sequentially according to the scanning direction to obtain the pre-set reference line if the detected laser sub-segment is multiple segments.

[0119] Based on the above method embodiments, this application also provides a 3D printing system, which includes: a print head assembly with a laser and a camera fixedly configured, and a printing platform disposed below the print head assembly; the 3D printing system is configured with a transformation relationship between the XYZ coordinate system and the pixel coordinate system; the 3D printing system is used to perform the platform leveling method of the 3D printing system as described in the previous embodiments.

[0120] Finally, it should be noted that the above-described embodiments are merely specific implementations of this application, used to illustrate the technical solutions of this application, and not to limit them. The scope of protection of this application is not limited thereto. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any person skilled in the art can still make equivalent substitutions to the technical solutions described in the foregoing embodiments within the scope of the technology disclosed in this application; and these modifications, changes, or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be covered within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method of platform leveling for a 3D printing system, the method comprising: The method is applied to a 3D printing system; the 3D printing system comprises a printing head assembly configured with a laser and a camera, and a printing platform arranged below the printing head assembly; the 3D printing system is configured with a conversion relationship between an XYZ coordinate system and a pixel coordinate system; the method comprises: a laser generated by the laser irradiates one or more positions of the printing platform, and an image of each corresponding position of a measured laser line is collected by the camera; for each image of the measured laser line, a pixel difference value corresponding to one or more points on the measured laser line is determined according to the measured laser line and a preset reference line; based on the pixel difference value corresponding to one or more points on each measured laser line and the conversion relationship between the XYZ coordinate system and the pixel coordinate system, XYZ absolute coordinate conversion is performed to form printing platform deviation data; based on the printing platform deviation data, the Z-axis position of the printing platform is compensated.

2. The method of claim 1, wherein, The preset reference line is a measured laser line at any specified position; or, the preset reference line is obtained through the following process: the laser emitted by the laser at least once scans a scanning reference area on the printing platform, and at least one scanning image in the laser scanning process is collected by the camera; wherein the scanning reference area is a preset area with the contact point between the nozzle in the printing head assembly and the printing platform as the center; identify the area image corresponding to the scanning reference area in at least one of the scanning images, and detect the corresponding laser sub-segment in each area image; based on the at least one detected laser sub-segment, a preset reference line is obtained by fitting.

3. The method of claim 1, wherein, The calibration process of the conversion relationship between the XYZ coordinate system and the pixel coordinate system is as follows: calibrate the positions in the pixel coordinate system and the XYZ coordinate system where Z is equal to a specified value; calibrate the first conversion coefficient of the first coordinate axis direction and the second conversion coefficient of the second coordinate axis direction in the pixel coordinate system; wherein the conversion coefficient is used to represent the number of pixels corresponding to a unit distance or the distance corresponding to a single pixel; calibrate the first offset of the pixel reference point in the Y-axis direction of the nozzle of the printing head assembly and the second offset of the pixel reference point in the X-axis direction of the nozzle of the printing head assembly in the pixel coordinate system; based on the calibration position where Z is equal to a specified value, the first conversion coefficient, the second conversion coefficient, the first offset and the second offset, the conversion relationship between the XYZ coordinate system and the pixel coordinate system is determined.

4. The method of claim 1, wherein, The step of compensating the Z-axis position of the printing platform based on the printing platform deviation data comprises: acquire the nozzle in the printing head assembly corresponding to the first target point on the printing platform to be moved to; based on the printing platform deviation data, determine the target platform deviation value corresponding to the first target point; If the target platform deviation value is a Z-axis pixel difference value, according to the target platform deviation value corresponding to the first target point and the conversion relationship between the XYZ coordinate system and the pixel coordinate system, a Z-axis absolute coordinate deviation value corresponding to the printing platform is determined, and the Z-axis height of the printing platform is compensated in the system according to the Z-axis absolute coordinate deviation value, so as to realize the platform automatic leveling function.

5. The method of claim 4, wherein, The printing platform deviation data includes: XYZ absolute coordinates corresponding to a plurality of points on the measured laser line and a printing platform Z-direction deviation value; based on the printing platform deviation data, the step of determining the target platform deviation value corresponding to the first target point includes: According to the XYZ absolute coordinates corresponding to a plurality of points on the measured laser line, it is determined from the platform deviation data whether the first target point exists; If yes, the printing platform Z-direction deviation value corresponding to the first target point in the platform deviation data is determined as the target platform deviation value; If no, a specified number of points adjacent to the first target point are found from the platform deviation data, and the printing platform Z-direction deviation values corresponding to the specified number of points are found, and the printing platform Z-direction deviation values corresponding to the specified number of points are linearly interpolated to determine the target platform deviation value corresponding to the first target point.

6. The method of claim 1, wherein, The first coordinate axis of the pixel coordinate system corresponds to the Z-axis in the XYZ coordinate system, and the second coordinate axis corresponds to the Y-axis or the X-axis in the XYZ coordinate system; the step of determining the pixel difference value corresponding to one or more points on the measured laser line according to the measured laser line and the pre-set reference line includes: For any point on the measured laser line, a second target point corresponding to the point of the measured laser line on the pre-set reference line in the first coordinate axis direction is determined; The pixel difference value of the point of the measured laser line and the second target point in the first coordinate axis direction, and the pixel difference value of the point of the measured laser line and the pixel reference point on the pre-set reference line in the second coordinate axis direction are determined.

7. The method of claim 2, wherein, The step of performing at least one scanning on the scanning reference area on the printing platform by the laser emitted by the laser includes: Starting from the edge of the scanning reference area contacted by one end of the laser line, scanning the edge of the scanning reference area, the scanning direction is parallel to the direction required by the laser line assembly, and the current scanning image is collected by the camera; the corresponding image is captured at a set scanning reference area distance interval, and the following laser moving scanning and image collection steps are performed: the position of the laser line is controlled to move the scanning reference area distance interval, the scanning reference area is scanned by the moved laser line, and the current scanning image after scanning is collected by the camera; the laser moving scanning and image collection steps are continuously executed until the other end of the laser line leaves the scanning reference area.

8. The method of claim 2, wherein, The step of fitting the at least one detected laser sub-segment to obtain the pre-set reference line includes: If the detected laser sub-line is one, fitting is performed based on the laser sub-line to determine a preset reference line; If the detected laser sub-line is multiple, the multiple laser sub-lines are sequentially spliced according to the scanning direction to obtain the preset reference line.

9. A platform leveling device for a 3D printing system, the device comprising: The device is applied to a 3D printing system; the 3D printing system comprises a printing head assembly configured with a laser and a camera, and a printing platform arranged below the printing head assembly; the 3D printing system is configured with a conversion relationship between an XYZ coordinate system and a pixel coordinate system; the device comprises: A laser line acquisition module for irradiating one or more positions of the printing platform by laser generated by the laser, and acquiring an image of an actual measured laser line of each corresponding position by the camera; A pixel difference determination module for determining, for each actual measured laser line image, a pixel difference corresponding to one or more points on the actual measured laser line according to the actual measured laser line and a preset reference line; A deviation data forming module for performing XYZ absolute coordinate conversion based on the pixel difference corresponding to one or more points on each actual measured laser line and the conversion relationship between the XYZ coordinate system and the pixel coordinate system to form printing platform deviation data; A deviation compensation module for compensating the Z-axis position of the printing platform based on the printing platform deviation data.

10. A 3D printing system, characterized by The 3D printing system comprises a printing head assembly configured with a laser and a camera, and a printing platform arranged below the printing head assembly; the 3D printing system is configured with a conversion relationship between an XYZ coordinate system and a pixel coordinate system; the 3D printing system is used to execute the platform leveling method of the 3D printing system according to any one of claims 1-8.

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