Printing platform deviation calibration method and device and 3D printing system

Abstract

The invention provides a printing platform deviation calibration method and device and a 3D printing system. The method comprises the steps that actually-measured laser rays of the 3D printing system during actual measurement are obtained; determining the pixel deviation of the actually measured laser line and a pre-calibrated reference line in a pixel coordinate system; the preset reference line is an actually measured laser line at any specified position, or is obtained through the following processes: fitting based on a laser line segment in a region image corresponding to a scanning reference region in at least one scanning image to obtain the preset reference line; the scanning image is an image acquired by the camera when the laser scans the scanning reference area; the scanning reference area is a preset area with the contact point of a nozzle in the printing head assembly and the printing platform as the center; and carrying out platform deviation calibration based on the pixel deviation and the conversion relation between the XYZ coordinate system and the pixel coordinate system. According to the invention, deviation calibration or compensation of the printing platform can be realized, and the system detection precision is improved.

Description

Technical Field

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

[0002] In existing 3D printing systems, achieving perfect parallelism of the printing platform during assembly is difficult. Tilts inevitably occur during assembly, and these tilt angles and directions are uncertain and random. In addition, the laser and camera may also tilt along the X or Y axis during assembly, producing similar issues, which are even more difficult to address than platform tilt. Therefore, parallelism deviations between the laser / camera and the printing platform surface on the Y or X axis are unavoidable. Given the tilt of the platform and the laser / camera, it is difficult to detect these tilts during assembly in current technologies. This inconsistency in relative parallelism during assembly introduces detection errors into the laser camera inspection system during scanning. In fact, besides the actual height of the model being measured, the parallelism deviation caused by assembly factors is also added to the system's detection data. This leads to errors in the inspection system, preventing it from achieving its high-precision detection capabilities. Even during high-precision inspection, errors caused by assembly may exceed the actual measured value, rendering the inspection function ineffective. Summary of the Invention

[0003] The purpose of this application is to provide a method, apparatus and 3D printing system for calibrating printing platform deviation, which can realize deviation calibration or compensation of printing platform and improve the detection accuracy of system.

[0004] In a first aspect, this application provides a method for calibrating a printing platform deviation, applied to a 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 an XYZ coordinate system and a pixel coordinate system. The method includes: acquiring a measured laser line during actual measurement of the 3D printing system; determining the pixel deviation between the measured laser line and a pre-calibrated reference line in the pixel coordinate system; the pre-set reference line is a measured laser line at any specified position; or, the pre-set reference line is obtained through the following process: fitting a laser line segment in a region image corresponding to a scanned reference region in at least one scanned image to obtain the pre-set reference line; the scanned image is an image acquired by a camera when the laser scans the scanned reference region; the scanned reference region is a preset region centered on the contact point between the nozzle in the print head assembly and the printing platform; and calibrating the platform deviation based on the pixel deviation and the transformation relationship between the XYZ coordinate system and the pixel coordinate system.

[0005] Furthermore, the step of fitting a pre-defined reference line based on laser line segments in the region image corresponding to the scan reference region in at least one scanned image includes: scanning the scan reference region on the printing platform at least once using a laser emitted by a laser, and acquiring at least one scanned image during the laser scanning process using a camera; identifying the region image corresponding to the scan reference region in at least one scanned image, and detecting the corresponding laser sub-line segments in each region image; and fitting the pre-defined reference line based on the detected at least one laser sub-line segment.

[0006] Further, the laser irradiates a laser line at a preset distance on the printing platform; the step of scanning the scanning reference area on the printing platform at least once using the laser emitted by the laser includes: starting from one end of the laser line contacting the edge of the scanning reference area, scanning along the edge of the scanning reference area in a direction parallel to the laser line assembly requirements, and capturing the current scan image using a camera; capturing corresponding images at set scanning reference area distance intervals, and 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 capturing the scan image after the current scan using 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.

[0007] Furthermore, the step of fitting based on at least one detected laser sub-segment to obtain a pre-set reference line includes: if there is only one detected laser sub-segment, fitting based on the laser sub-segment to determine the pre-set reference line; if there are multiple detected laser sub-segments, sequentially splicing the multiple laser sub-segments according to the scanning direction to obtain the pre-set reference line.

[0008] Further, 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 step of determining the pixel deviation between the measured laser line and the pre-set reference line in the pixel coordinate system includes: for any detection point in the measured laser line, determining the target point corresponding to the detection point on the pre-set reference line in the direction of the first coordinate axis; and determining the pixel difference between the detection point and the target point in the direction of the first coordinate axis.

[0009] Furthermore, the steps for platform deviation calibration based on pixel deviation and the transformation relationship between the XYZ coordinate system and the pixel coordinate system include: converting the pixel difference into the Z coordinate difference corresponding to the printing platform according to the transformation relationship; automatically adding the Z coordinate difference to the measured Z coordinate corresponding to the detection point to obtain the calibrated Z coordinate for the detection point; or adjusting the Z coordinate of the printing platform according to the Z coordinate difference.

[0010] Furthermore, the calibration process for the transformation relationship between the XYZ coordinate system and the pixel coordinate system is as follows: The positions where Z equals a specified value in the pixel coordinate system and the XYZ coordinate system are calibrated; a first transformation coefficient in the first coordinate axis direction and a second transformation coefficient in the second coordinate axis direction in the pixel coordinate system are calibrated; wherein, the transformation coefficient is used to characterize the number of pixels corresponding to a unit distance or the distance corresponding to a single pixel; a first offset in the Y-axis direction between the pixel reference point and the nozzle of the printhead assembly in the pixel coordinate system and a second offset in the X-axis direction between the pixel reference point and the nozzle of the printhead assembly are calibrated; based on the calibration position where Z equals a specified value, the first transformation coefficient, the second transformation coefficient, the first offset, and the second offset, the transformation relationship between the XYZ coordinate system and the pixel coordinate system is determined.

[0011] Furthermore, the step of calibrating the position where Z equals the specified value in the pixel coordinate system and the XYZ coordinate system includes: controlling the printing platform to move upward along the Z-axis in the XYZ coordinate system, or controlling the print head assembly to move downward along the Z-axis, until the printing platform is detected to be in contact with the nozzle of the print head assembly, and recording the current coordinate value on the Z-axis in the XYZ coordinate system as the specified value; controlling the printing platform / print head assembly to continue moving downward / upward along the Z-axis in the XYZ coordinate system by a scanning height Hc, and determining the coordinate position of the laser on the first coordinate axis in the pixel coordinate system in the image currently acquired by the camera, corresponding to the position in the XYZ coordinate system where Z equals the specified value + scanning height Hc.

[0012] Secondly, this application also provides a printing platform deviation calibration device, which is applied to a 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 for acquiring the measured laser line during actual measurement of the 3D printing system; a deviation determination module for determining the pixel deviation between the measured laser line and a pre-calibrated reference line in the pixel coordinate system; the pre-set reference line is the measured laser line at any specified position; or, the pre-set reference line is obtained through the following process: fitting the laser line segment in the region image corresponding to the scan reference region in at least one scanned image to obtain the pre-set reference line; the scanned image is the image acquired by the camera when the laser scans the scan reference region; the scan reference region is a preset region centered on the contact point between the nozzle in the print head assembly and the printing platform; and a platform calibration module for performing platform deviation calibration based on the pixel deviation and the transformation relationship between the XYZ coordinate system and the pixel coordinate system.

[0013] 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 an XYZ coordinate system and a pixel coordinate system; the 3D printing system is used to perform the printing platform deviation calibration method as described in the first aspect.

[0014] The printing platform deviation calibration method, apparatus, and 3D printing system provided in this application are applied to a 3D printing system. The 3D printing system includes a print head assembly equipped with a laser and a camera, and a printing platform positioned 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. First, a pre-calibrated reference line is obtained by fitting laser line segments in a region image corresponding to a scanned reference region in at least one scanned image. The scanned image is an image captured by the camera when the laser scans the scanned reference region. The scanned reference region is a preset region centered on the contact point between the nozzle in the print head assembly and the printing platform. Then, the measured laser line during actual measurement of the 3D printing system is acquired. The pixel deviation between the measured laser line and the pre-set reference line in the pixel coordinate system is determined. Finally, platform deviation calibration is performed based on the pixel deviation and the transformation relationship between the XYZ coordinate system and the pixel coordinate system. This method can achieve platform assembly deviation compensation and improve the system's detection accuracy. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0016] Figure 1 A schematic diagram of a 3D printing system provided in an embodiment of this application;

[0017] Figure 2 A flowchart of a printing platform deviation calibration method provided in this application embodiment;

[0018] Figure 3 A comparison diagram of a pre-set reference line and a measured laser line provided for an embodiment of this application;

[0019] Figure 4 This application provides a schematic diagram of laser position in a pixel coordinate system.

[0020] Figure 5 This application provides a schematic diagram of laser position comparison in a pixel coordinate system.

[0021] Figure 6 A schematic diagram of a sticker model provided in an embodiment of this application;

[0022] 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.

[0023] 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;

[0024] Figure 9 This is a schematic diagram illustrating another nozzle-pixel coordinate center offset provided in an embodiment of this application;

[0025] 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;

[0026] Figure 11 A schematic diagram illustrating the deviation between an ideal platform and an actual platform provided in this application embodiment;

[0027] Figure 12 A schematic diagram of a scanning reference area provided in an embodiment of this application;

[0028] Figure 13 This application provides a schematic diagram of the laser line movement direction in an embodiment.

[0029] Figure 14 A schematic diagram of a plurality of first scanned images provided for an embodiment of this application;

[0030] Figure 15 This is a schematic diagram of a region image corresponding to multiple scanning reference regions provided in an embodiment of this application;

[0031] Figure 16 A schematic diagram of a pre-defined reference line provided for an embodiment of this application;

[0032] Figure 17 This is a structural block diagram of a printing platform deviation calibration device provided in an embodiment of this application. Detailed Implementation

[0033] 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.

[0034] In existing 3D printing systems, inaccurate detection or even detection failure can occur due to inconsistencies in the parallelism of the printing platform, camera, and laser during assembly and manufacturing. This application provides a printing platform deviation calibration method, apparatus, and 3D printing system that can calibrate or compensate for printing platform deviations, thereby improving system detection accuracy. To facilitate understanding of this embodiment, a detailed description of the printing platform deviation calibration method disclosed in this application is provided first.

[0035] In 3D printing systems, during system assembly or model removal from the platform, the printing platform may not be perfectly level. This means the Z-coordinates at any point on the platform surface may not be equal, indicating a tilt. Consequently, the nozzle surface may not be horizontal when moved to different positions. To calibrate this platform deviation, this application provides a printing platform deviation calibration method applied to a 3D printing system; see [link to relevant documentation]. Figure 1 As 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.

[0036] See Figure 2 As shown, the printing platform deviation calibration method provided in this application includes:

[0037] Step S202: Obtain the measured laser line of the 3D printing system during actual measurement;

[0038] The measured laser line can be determined by scanning the image after the system illuminates the image at any position on the printing platform. In other words, it is the laser line determined by scanning the actual printing platform.

[0039] Step S204: Determine the pixel deviation between the measured laser line and the preset reference line in the pixel coordinate system; the preset reference line is the measured laser line at any specified position; or, the preset reference line is obtained by the following process: fitting the laser line segment in the region image corresponding to the scan reference region in at least one scanned image to obtain the preset reference line; the scanned image is the image captured by the camera when the laser scans the scan reference region; the scan reference region is a preset region centered on the contact point between the nozzle in the printhead assembly and the print platform;

[0040] Specifically, the pixel deviation between the measured laser line and the pre-defined reference line on the first coordinate axis of the pixel coordinate system can be determined. 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 requiring parallelism.

[0041] The pre-defined reference line can also be obtained by the following method, which has lower requirements for the installation of the measured laser line: the pre-calibrated reference line is obtained by fitting the laser line segment in the region image corresponding to the scanning reference area in at least one scanned image; the scanned image is the image captured by the camera when the laser scans the scanning reference area; the scanning reference area is a pre-defined area centered on the contact point between the nozzle in the printhead assembly and the printing platform.

[0042] The 3D printing system is configured with a transformation relationship between the XYZ coordinate system and the pixel coordinate system (the process of determining this transformation relationship will be described in detail later); that is, the position calibration of the pixel coordinate system and the XYZ coordinate system with Z equal to a specified value has been completed. Based on this, when the nozzle in the print head assembly contacts the printing platform, the contact point can be set as a small area of ​​scanning reference region. The above-mentioned scanning reference region can be a small area region of various shapes. For the convenience of calculation, in this embodiment, the scanning reference region is set as a square with a side length of 2mm.

[0043] The laser scans the reference area using a laser traversal scanning method. Each time, a portion of the laser line is aligned with the reference area, and the laser line segment corresponding to the scanning area is continuously changed until a complete laser line is traversed. Simultaneously, camera images are acquired, resulting in multiple initial scan images.

[0044] The reference line specified above is the ideal laser line under the ideal laser scanning platform. The ideal platform is defined as follows:

[0045] like Figure 1 As shown, when the nozzle "collides" with the printing platform and the system detects the trigger signal generated by the platform's sensor, the system assumes that the height Z of the nozzle's current position equals a specified value, which is 0 for example. If the system keeps the XZ axis position unchanged, the nozzle moves to the right. During this movement, a trajectory line is generated on the surface of the nozzle, as shown... Figure 3 The gray dashed line in the image shows the trajectory line. Since this trajectory line is generated by the nozzle moving along any X and Y axis, if we collect all the trajectory lines generated by the nozzle moving along any X and Y axis on the printing platform, we form a "track line set" generated by the nozzle moving at any X and Y axis position. This set is actually a plane generated by the movement of many nozzles along the X and Y axes. Here, we define it as an "ideal plane". This ideal plane is actually invisible to the naked eye. However, with any movement of the nozzle in the X and Y directions above the platform, the nozzle surface will always completely coincide with and be absolutely parallel to this "ideal plane".

[0046] Since the laser camera detection system is also fixed on the printhead assembly containing the nozzle, the laser camera detection system moves along with the nozzle, and the height difference between the laser camera detection system and the nozzle surface remains constant during this movement. Figure 1 For ease of explanation, let's consider a hypothetical scenario: assuming that during assembly, the printing platform surface can be perfectly parallel and overlapped with an ideal plane (which is practically impossible), while the height difference between the laser camera detection system and the nozzle surface remains constant. When the laser camera detection system and nozzle move, the laser illuminates this ideal plane. Therefore, the laser's position in the pixel coordinate system remains unchanged at any given location. If Z=0, the laser's position in the pixel coordinate system is as follows: Figure 1 As shown on the right, regardless of whether the print head and laser camera move to any position simultaneously, the laser beam will always strike the same spot on the ideal plane.

[0047] The laser beam is irradiated on a platform that is perfectly parallel to and coincident with the nozzle surface at a position in the camera pixel coordinate system (e.g., Figure 1As shown in the right figure, this position is the effect of the interaction of various parallelism deviations on the laser irradiation on the ideal plane after manufacturing and assembly, as well as the relative positions of the laser and the printing platform surface, Y-axis, and the camera and the printing platform surface, Y-axis. At this time, the actual position of the laser in the camera pixel coordinate system is the result of the interaction of various parallelism deviations.

[0048] In this embodiment of the application, the ideal laser line under the ideal laser scanning platform, i.e., the pre-set reference line, can be determined by the above fitting method.

[0049] Step S206: Based on pixel deviation and the transformation relationship between the XYZ coordinate system and the pixel coordinate system, perform platform deviation calibration.

[0050] For any point in the measured laser line, the pixel deviation in the first coordinate axis direction in the pixel coordinate system can be determined by combining the position in the pre-set reference line. Then, according to the transformation relationship between the pixel coordinate system and the XYZ coordinate system, it can be converted into the actual Z coordinate deviation of the platform for platform deviation compensation.

[0051] See Figure 3 As shown, if the system uses the aforementioned pre-set reference line as a reference (hereinafter referred to as the reference laser line) to illuminate the actual plane of the printing platform with a laser, the following situations may occur, see [reference]. Figure 4 As shown in the figure, the gray solid line is the fitted line of the laser irradiating the ideal plane (i.e., the reference line set in advance), and the black dashed line is the laser line irradiating the actual plane of the printing platform (i.e., the measured laser line).

[0052] 1) If the current laser line (i.e., the measured laser line) is above the reference laser line in the pixel coordinate system, then the actual plane of the printing platform is higher than the ideal plane; 2) If the current laser line is below the reference laser line in the pixel coordinate system, then the actual plane of the printing platform is lower than the ideal plane; 3) If the current laser line intersects with the reference laser line in the pixel coordinate system, then the actual plane of the printing platform intersects with the ideal plane; 4) If the current laser line coincides with the reference laser line in the pixel coordinate system, then the actual plane of the printing platform coincides with the ideal plane.

[0053] In the printing platform deviation calibration method provided in this application embodiment, at least one scanned image is obtained in advance for the area corresponding to the contact point between the nozzle and the platform. A pre-set reference line is obtained based on the laser line segment in the at least one scanned image. Furthermore, the pixel difference between any measured laser line and the pre-set reference line in the pixel coordinate system can be determined. Through the transformation relationship between the pre-set XYZ coordinate system and the pixel coordinate system, the platform deviation can be calibrated or compensated. This can solve the problem that the parallelism deviation caused by the assembly and manufacturing factors of the system causes the high-precision detection of the laser detection system to be inaccurate, and enable the high-precision detection function of the laser detection system to be realized.

[0054] 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:

[0055] See Figure 1 As 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.

[0056] 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.

[0057] 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.

[0058] Laser 11 must be installed parallel to the X-axis or Y-axis. Figure 1 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 1When the laser position remains unchanged after a 90° rotation, 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 1 When 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.

[0059] (1) Calibrate the position in the pixel coordinate system and the XYZ coordinate system where Z equals a specified value:

[0060] 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.

[0061] 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.

[0062] 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.

[0063] (2) Calibrate the first transformation coefficient in the first coordinate axis direction of the pixel coordinate system:

[0064] 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.

[0065] 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.

[0066] Taking the first conversion factor as an example with the number of pixels per millimeter, the specific calibration process is as follows: See Figure 5 As shown, keeping the printing platform in the XYZ coordinate system Z = 0 + Hc at the laser camera scanning height, for example, adjust the printing platform downwards by 1 mm and record the pixel difference before and after the movement, i.e., the number of pixels; when the printing platform moves downwards by 1 mm, the pixel difference of the laser image before and after the two operations is 6 pixels. Given that the movement distance is 1 mm, find the number of pixels K per millimeter in the Z-axis direction. Z =6÷1=6; K ZThis means that if the pixel difference between the ordinate position relative to the specified Z value and the current depth position is 6 pixels, then this movement results in a 1mm downward position 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. In other words, a deviation of 6 pixels in each column of the ordinate represents a downward movement of 1mm by the printing platform, resulting in the output mechanical coordinate Z = (0 + Hc) + 1 - Hc = 1. Because scanning is prone to interference with the model, it is necessary to offset the scanning height. The actual output coordinates are obtained by subtracting the scanning height.

[0067] The laser measurement system uses the mechanical coordinate system with Z equal to a specified value plus the scanning height as a reference to detect height in the Z direction. The system outputs the Z-direction coordinates in the XYZ coordinate system. Within the effective measurement range (M... L Depth measurement is performed within the specified area and superimposed on the XYZ coordinate system. The formula for outputting the measurement range of the Z-axis of the XYZ coordinate system is: Z = 0 + Hc ± 0.5 * M L .

[0068] 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.

[0069] (3) Calibrate the second transformation coefficient in the second coordinate axis direction of the pixel coordinate system:

[0070] 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.

[0071] 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.

[0072] 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-to-center distance between any two dots in the image is 5mm. A camera is used to photograph the sticker, obtaining an image. By identifying the dots in the image, the pixel difference between the centers of any two horizontally aligned dots is calculated. For example, if the calculated pixel difference is 30, and the distance between the horizontally aligned center and the actual center is 5mm, then the number of pixels per millimeter in the Y-axis direction is K. Y =30÷5=6; K Y This means that if the measured object has a pixel difference of 6 pixels in the x-axis 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.

[0073] (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:

[0074] 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.

[0075] 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.

[0076] 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:

[0077] 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.

[0078] 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).

[0079] (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.

[0080] 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.

[0081] 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.

[0082] 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.

[0083] (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:

[0084] 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.

[0085] 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.

[0086] 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.

[0087] 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.

[0088] The following describes in detail the fitting process of the pre-calibrated reference line: A prerequisite for the fitting process is to complete the above-mentioned coordinate system transformation standard, combined with... Figure 11As 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.

[0089] (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 the camera during the laser scanning process;

[0090] 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.

[0091] 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.

[0092] 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.

[0093] The Z=0 calibration point is used as the laser scanning reference area, as follows: Figure 12 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.

[0094] 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.

[0095] 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 13 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.

[0096] 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 14As 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.

[0097] (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 part is deleted. The effect is as follows: Figure 15 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.

[0098] (3) Fit the detected laser line segment to obtain a pre-set reference line. If there is only one detected laser line segment, fit the laser line segment to determine the pre-set reference line; if there are multiple detected laser line segments, stitch the multiple laser line segments sequentially according to the scanning direction to obtain the pre-set reference line.

[0099] 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 16 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 16 As shown by the thick dashed line.

[0100] The threshold platform calibration process is detailed below: In this embodiment, the first coordinate axis of the pixel coordinate system corresponds to the Z-axis in the XYZ coordinate system, and the second axis corresponds to the Y-axis or X-axis in the XYZ coordinate system; the steps of determining the pixel deviation between the measured laser line and the pre-set reference line in the scanned image, and calibrating the platform deviation based on the pixel deviation and the transformation relationship between the XYZ coordinate system and the pixel coordinate system, include:

[0101] For any detection point in the measured laser line, a target point corresponding to the detection point is determined on a pre-set reference line along the first coordinate axis. The pixel difference between the detection point and the target point along the first coordinate axis is determined. According to the conversion relationship, the pixel difference is converted into the Z-coordinate difference corresponding to the printing platform (specifically, the pixel difference can be converted into the Z-coordinate difference corresponding to the printing platform according to the first conversion coefficient along the first coordinate axis). Platform deviation compensation is performed based on the Z-coordinate difference. Specifically, for the detection point, the measured Z-coordinate corresponding to the detection point is automatically added to the Z-coordinate difference as the calibrated Z-coordinate; or, the Z-coordinate of the printing platform is adjusted according to the Z-coordinate difference.

[0102] In this embodiment, when performing coordinate calculations, the system calculates the pixel difference between the actual plane and the ideal plane of the printing platform. This pixel difference represents the actual height difference between the actual plane and the ideal plane. Since the laser illumination on the ideal plane is a product of the interaction between the laser, the camera, and the Y-coordinate during the assembly and manufacturing process, subtracting the position of the ideal plane from the position of the actual platform when calculating the relative height pixel difference between the two planes effectively eliminates the influence of the parallel deviation caused by the assembly and manufacturing process. This achieves high-precision measurement by the laser camera. Furthermore, combined with the coordinate system calibration method, if the pixel difference between the ideal plane and the actual plane of the printing platform at any position in the XY direction is transformed into mechanical coordinates, the height difference information of the absolute coordinates of any position of the printing platform in the XY direction in the mechanical coordinate system can be obtained. This information represents the parallelism deviation of the printing platform relative to the ideal plane during the assembly and manufacturing process. This deviation can be used as an automatic leveling compensation parameter for the system.

[0103] In this embodiment, the system can obtain the parallelism deviation values ​​of different positions relative to the ideal plane by laser scanning any position on the printing platform. During the printing process, when the nozzle prints at any position on the actual plane of the printing platform, the system only needs to compensate the Z-axis coordinate value for the parallelism deviation at the corresponding position, thereby realizing the automatic Z-axis compensation function, i.e., the automatic leveling function, for printing on an inclined printing platform.

[0104] Based on the above method embodiments, this application also provides a printing platform deviation calibration device, which is applied to a 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 relevant documentation] Figure 17 As shown, the device includes: a laser line acquisition module 102, used to acquire the measured laser line during actual measurement of the 3D printing system; a deviation determination module 104, used to determine the pixel deviation between the measured laser line and a pre-set reference line in the pixel coordinate system; the pre-set reference line is the measured laser line at any specified position; or, the pre-set reference line is obtained through the following process: fitting the laser line segment in the region image corresponding to the scan reference region in at least one scanned image to obtain the pre-set reference line; the scanned image is the image captured by the camera when the laser scans the scan reference region; the scan reference region is a preset region centered on the contact point between the nozzle in the print head assembly and the printing platform; and a platform calibration module 106, used to perform platform deviation calibration based on the pixel deviation and the transformation relationship between the XYZ coordinate system and the pixel coordinate system.

[0105] Furthermore, the above-mentioned device also includes: a setting module for performing the following preset reference line setting process: scanning a scanning reference area on a printing platform at least once using a laser emitted by a laser, and acquiring at least one scanning image during the laser scanning process using a camera; identifying a region image corresponding to the scanning reference area in at least one scanning image, and detecting the corresponding laser sub-line segment in each region image; and fitting based on the detected at least one laser sub-line segment to obtain a preset reference line.

[0106] Further, the aforementioned laser irradiates a laser line at a preset distance on the printing platform; the setting module is 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 the current scan image is acquired by a camera; corresponding images are captured at preset scanning reference area distance intervals, performing the following laser moving scan and image acquisition steps: controlling the position of the laser line to move at the scanning reference area distance interval, using the moved laser line to scan the scanning reference area, and acquiring the scan image after the current scan by 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.

[0107] Furthermore, the aforementioned setting module is used to: if the detected laser sub-segment is a single line, fit the laser sub-segment to determine a pre-set reference line; if the detected laser sub-segment is multiple lines, sequentially splice the multiple laser sub-segments according to the direction of the laser line to obtain a pre-set reference line.

[0108] 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 deviation determination module 104 is used to determine, for any detection point in the measured laser line, the target point corresponding to the detection point on a pre-set reference line in the direction of the first coordinate axis; and to determine the pixel difference between the detection point and the target point in the direction of the first coordinate axis.

[0109] Furthermore, the aforementioned platform calibration module 106 is used to convert the pixel difference into the Z coordinate difference corresponding to the printing platform according to the conversion relationship; for the detection point, it automatically adds the Z coordinate difference to the measured Z coordinate corresponding to the detection point as the calibrated Z coordinate; or, it adjusts the Z coordinate of the printing platform according to the Z coordinate difference.

[0110] Furthermore, the aforementioned setting module is also used to perform a calibration process for the transformation relationship between the XYZ coordinate system and the pixel coordinate system: calibrating the position in the pixel coordinate system and the XYZ coordinate system where Z equals a specified value; calibrating the first transformation coefficient in the first coordinate axis direction and the second transformation coefficient in the second coordinate axis direction in the pixel coordinate system; wherein, the transformation coefficient is used to characterize the number of pixels corresponding to a unit distance or the distance corresponding to a single pixel; calibrating the first offset of the pixel reference point and the nozzle of the printhead assembly in the Y-axis direction and the second offset of the pixel reference point and the nozzle of the printhead assembly in the X-axis direction in the pixel coordinate system; and determining the transformation relationship between the XYZ coordinate system and the pixel coordinate system based on the calibration position where Z equals a specified value, the first transformation coefficient, the second transformation coefficient, the first offset, and the second offset.

[0111] Furthermore, the aforementioned setting module is also used to: control the printing platform to move upward along the Z-axis in the XYZ coordinate system, or control the printhead assembly to move downward along the Z-axis until the printing platform is detected to be in contact with the nozzle of the printhead assembly, and record the current coordinate value on the Z-axis in the XYZ coordinate system as a specified value; control the printing platform / printhead assembly to continue moving downward / upward along the Z-axis in the XYZ coordinate system by a scanning height Hc, and determine the coordinate position of the laser on the first coordinate axis in the pixel coordinate system in the image currently acquired by the camera, corresponding to the position in the XYZ coordinate system where Z equals the specified value + scanning height Hc.

[0112] 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 printing platform deviation calibration method as described in the foregoing method embodiments.

[0113] The computer program products of the methods, apparatus and systems provided in the embodiments of this application include a computer-readable storage medium storing program code. The instructions included in the program code can be used to execute the methods described in the preceding method embodiments. For specific implementation, please refer to the method embodiments, which will not be repeated here.

[0114] If the aforementioned functions are implemented as software functional units and sold or used as independent products, they can be stored in a processor-executable, non-volatile, computer-readable storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this application.

Claims

1. A method for calibrating a printing platform deviation, characterized in that, The method is applied to a 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; the method includes: Obtain the measured laser line of the 3D printing system during actual measurement; The pixel deviation between the measured laser line and the preset reference line in the pixel coordinate system is determined; the preset reference line is the measured laser line at any specified position; or, the preset reference line is obtained by fitting the laser line segment in the region image corresponding to the scan reference region in at least one scanned image to obtain the preset reference line; the scanned image is the image captured by the camera when the laser scans the scan reference region; the scan reference region is a preset region centered on the contact point between the nozzle in the printhead assembly and the printing platform. Platform deviation calibration is performed based on the pixel deviation and the transformation relationship between the XYZ coordinate system and the pixel coordinate system.

2. The method according to claim 1, characterized in that, The process for setting up a pre-defined reference line is as follows: The laser emitted by the laser is used to scan the scanning reference area on the printing platform at least once, and the camera is used to capture at least one scan image during the laser scanning process; Identify at least one region image corresponding to a scan reference region in the scanned image, and detect the corresponding laser sub-segment in each region image; A pre-defined reference line is obtained by fitting at least one of the detected laser sub-segments.

3. The method according to claim 2, characterized in that, The laser beam is directed onto a laser line at a predetermined distance on the printing platform. The step of scanning a reference area on the printing platform at least once using a laser emitted by the laser includes: Starting from one end of the laser line 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. The current scanned image is captured by the camera. Corresponding images are captured at set intervals between the scanning reference areas. The following laser moving scan and image acquisition steps are performed: the position of the laser line is controlled to move at the interval between the scanning reference areas, and the moved laser line is used to scan the scanning reference area. 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.

4. The method according to claim 2, characterized in that, The step of fitting a pre-defined reference line based on at least one detected laser sub-segment includes: If the detected laser sub-segment is a single line, a fitting is performed based on the laser sub-segment to determine a pre-set reference line; If multiple laser sub-segments are detected, they are sequentially spliced ​​together according to the scanning direction to obtain a pre-set reference line.

5. The method according to claim 1, characterized in that, 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 step of determining the pixel deviation between the measured laser line and the pre-set reference line in the pixel coordinate system includes: For any detection point in the measured laser line, determine the target point corresponding to the detection point on the pre-set reference line in the direction of the first coordinate axis; Determine the pixel difference between the detection point and the target point along the first coordinate axis.

6. The method according to claim 5, characterized in that, The steps for platform deviation calibration based on the pixel deviation and the transformation relationship between the XYZ coordinate system and the pixel coordinate system include: Based on the conversion relationship, the pixel difference is converted into the Z-coordinate difference corresponding to the printing platform; For the detection point, the measured Z-coordinate corresponding to the detection point is automatically added to the Z-coordinate difference to obtain the calibrated Z-coordinate; or, the Z-coordinate of the printing platform is adjusted according to the Z-coordinate difference.

7. The method according to claim 5, characterized in that, The calibration process for the transformation relationship between the XYZ coordinate system and the pixel coordinate system is as follows: Calibrate the position in the pixel coordinate system and the XYZ coordinate system where Z equals a specified value; The first transformation coefficient in the first coordinate axis direction and the second transformation coefficient in the second coordinate axis direction of the pixel coordinate system are calibrated; wherein the transformation coefficient is used to characterize the number of pixels corresponding to a unit distance or the distance corresponding to a single pixel; The pixel reference point in the pixel coordinate system is calibrated by a first offset in the Y-axis direction from the nozzle of the printhead assembly, and a second offset in the X-axis direction from the pixel reference point to the nozzle of the printhead assembly. Based on the calibration position where Z equals a specified value, the first transformation coefficient, the second transformation coefficient, the first offset, and the second offset, the transformation relationship between the XYZ coordinate system and the pixel coordinate system is determined.

8. The method according to claim 7, characterized in that, The step of calibrating the pixel coordinate system and the position in the XYZ coordinate system where Z equals a specified value includes: Control the printing platform to move upward along the Z-axis in the XYZ coordinate system, or control the print head assembly to move downward along the Z-axis, until the printing platform is detected to be in contact with the nozzle of the print head assembly, and record the current coordinate value on the Z-axis in the XYZ coordinate system as a specified value; Control the printing platform / printhead assembly to continue moving down / up along the Z-axis in the XYZ coordinate system by a scanning height Hc, and determine the coordinate position of the laser on the first coordinate axis in the pixel coordinate system in the image currently acquired by the camera, which corresponds to the position in the XYZ coordinate system where Z equals a specified value + scanning height Hc.

9. A printing platform deviation calibration device, characterized in that, The device is applied to a 3D printing system; the 3D printing system 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 device includes: The laser line acquisition module is used to acquire the measured laser line of the 3D printing system during actual measurement. A deviation determination module is used to determine the pixel deviation between the measured laser line and a pre-set reference line in the pixel coordinate system; the pre-set reference line is the measured laser line at any specified position; or, the pre-set reference line is obtained through the following process: fitting the pre-set reference line based on the laser line segment in the region image corresponding to the scan reference region in at least one scanned image; the scanned image is the image captured by the camera when the laser scans the scan reference region; the scan reference region is a preset region centered on the contact point between the nozzle in the printhead assembly and the printing platform; The platform calibration module is used to perform platform deviation calibration based on the pixel deviation and the transformation relationship between the XYZ coordinate system and the pixel coordinate system.

10. A 3D printing system, characterized in that, 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 3D printing system is used to perform the printing platform deviation calibration method as described in any one of claims 1-7.

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