A galvanometer control correction method

Abstract

The invention discloses a galvanometer control correction method, which belongs to the technical field of 3D printers. The method comprises constructing a target point matrix and a projection point matrix corresponding thereto, selecting four target points to form a unit calibration rectangle, setting a base point of the unit calibration rectangle, performing translation correction according to an offset of the base point after performing a pincushion correction, setting an error threshold to filter out points with excessively large errors in the unit calibration rectangle, leaving points within the error range to form a calibration matrix, and dividing a processing plane according to the calibration matrix to form a plurality of processing areas to process parts in batches, thereby solving the technical problem of the cumulative error of the galvanometer and improving the processing accuracy of the same batch of parts. The invention can reduce the cumulative error of the galvanometer caused by the unit step distance, so that the final error range is smaller, is easy to operate, has a simple software design, and the size of the calibration matrix can be changed according to the user's setting, has high flexibility and strong applicability.

Description

Technical Field

[0001] The invention belongs to the technical field of 3D printers and relates to a galvanometer control correction method. Background Art

[0002] The SLM printer is a device for printing precision parts. The printed parts have the characteristics of small size, high precision and low surface roughness.

[0003] At present, the laser of SLM printer mainly uses galvanometer to control the moving trajectory. The causes of its error include two factors:

[0004] 1. When the laser is projected onto the processing plane, a pillow-shaped deformation will occur;

[0005] 2. The galvanometer is driven by a stepper motor, and the stepper motor will produce a certain cumulative error when the laser moves due to the error in the step distance, which will eventually affect the overall processing error. Summary of the invention

[0006] The purpose of the present invention is to provide a galvanometer control correction method, which solves the technical problem of cumulative error of the galvanometer and improves the processing accuracy of parts in the same batch.

[0007] To achieve the above object, the present invention adopts the following technical solution:

[0008] A galvanometer control correction method comprises the following steps:

[0009] Step 1: Establish a correction server, which is connected to the SLM printer via a data cable. The SLM printer at least includes a high-definition camera and a galvanometer control system. The high-definition camera is used to take pictures of the processing plane of the SLM printer, and the galvanometer control system is used to control the laser path of the SLM printer.

[0010] The correction server reads the image of the processing plane from the SLM printer, presets several ideal positions in the image, marks a target point at each ideal position, and calculates the actual position data of each target point on the processing plane according to the ratio between the pixel size of the image of the processing plane and the actual size of the processing plane, which is recorded as the conversion ratio;

[0011] All targets are formed into a target matrix, which contains the number and actual position data of each target;

[0012] Step 2: The correction server inputs the target matrix to the SLM printer. The SLM printer controls the test laser to project on the processing plane in sequence according to the target number based on the position data of each target in the target matrix through the galvanometer control system to obtain the projection point corresponding to each target.

[0013] The SLM printer uses a high-definition camera to take pictures of each projection point to form a collection of projection point pictures;

[0014] Step 3: The correction server obtains a set of projection point images, calculates the actual position data of each projection point according to the conversion ratio, and constructs a projection point matrix; the projection point matrix contains the number and actual position data of each projection point; and establishes a mapping list between the projection point number and the target point number;

[0015] The correction server selects 4 target points in the target point matrix to form a unit calibration rectangle, takes the vertex of the upper left corner of the unit calibration rectangle as the base point, searches for the projection point corresponding to the base point in the projection point matrix according to the mapping list, i.e., the base point projection point, compares the actual position data of the base point with the actual position data of the base point projection point, and obtains the deviation value between the two, i.e., the base point error value;

[0016] The target points contained in the unit calibration rectangle are set as the unit calibration target points, and pincushion correction is performed on the projection points corresponding to all the unit calibration target points in the unit calibration rectangle;

[0017] Step 4: After the pincushion correction, perform a translation correction on the unit calibration rectangle according to the base point error value, record the deviation value between the unit calibration target point and its corresponding projection point after the translation correction, that is, the galvanometer error value, and form a galvanometer error matrix;

[0018] Step 5: The correction server presets an error threshold, and screens the galvanometer error matrix according to the error threshold to obtain all unit calibration targets whose galvanometer error values ​​are within the error threshold range, and form a calibration matrix;

[0019] Step 6: The processing plane is divided by the calibration matrix to obtain multiple processing areas. A safe processing area is set in each processing area. The distance between the safe processing area and the surrounding areas of the processing area is m times the error threshold, and the value of m is between 1.5 and 3;

[0020] Process parts of the same batch or lot number in each safe processing area.

[0021] Preferably, the conversion ratio is N:1, where N represents the pixel size ratio, 1 represents the actual size ratio of the processing plane, and the value of N is between 0.1 and 1;

[0022] The actual position data is the position of the target point in the world coordinate system on the processing plane.

[0023] Preferably, when calculating the position data, the specific steps are as follows:

[0024] Step 2-1: Obtain the actual size of the processing plane and establish the world coordinate system model of the processing plane;

[0025] Get the image of the processing plane and calculate the conversion ratio between the image pixel size and the world coordinate system;

[0026] Step 2-2: According to the conversion ratio, N:1, restore the world coordinate system information of the processing plane in the image of the processing plane; the value of N is between 0.1 and 1;

[0027] Step 2-3: Preset the target matrix in the image of the processing plane, calculate the position of each target in the target matrix in the world coordinate system according to the conversion ratio, that is, the actual position data, and store it.

[0028] Preferably, when executing step 3, the actual position data of each projection point is calculated according to the conversion ratio, specifically including calculating the position of the projection point in the world coordinate system corresponding to the pixel position of the projection point in the image according to the conversion ratio.

[0029] Preferably, when executing step 6, the following steps are specifically included:

[0030] Step 6-1: In the row direction, for two adjacent calibration matrices, the unit calibration target point at the upper right corner of the calibration matrix on the left and the base point of the calibration matrix on the right share the same target point;

[0031] Step 6-2: In the column direction, for two adjacent calibration matrices, the unit calibration target point at the lower left corner of the upper calibration matrix and the base point of the lower calibration matrix share the same target point;

[0032] Step 6-3: When the shape of the calibration matrix needs to be cropped, cropping is performed preferentially in the row direction.

[0033] The galvanometer control correction method described in the present invention solves the technical problem of the cumulative error of the galvanometer and improves the processing accuracy of parts in the same batch. The present invention can reduce the cumulative error of the galvanometer caused by the unit step size, so that its final error range is smaller and easy to operate. Without changing the basic control elements of the galvanometer, the overall processing error of the parts in the same batch is further reduced. The software design is simple, the size of the calibration matrix can be changed according to the user's settings, and it is highly flexible and applicable. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 is a flow chart of the present invention;

[0035] Figure 2 Schematic diagram of the mathematical model of the target matrix of the present invention;

[0036] Figure 3 It is a schematic diagram of a mathematical model of the projection point matrix of the present invention;

[0037] Figure 4 It is a schematic diagram of a mathematical model of the projection point matrix corrected according to the method of step 4 to step 6 of the present invention;

[0038] Figure 5 Schematic diagram of the mathematical model of two adjacent calibration matrices of the present invention. DETAILED DESCRIPTION

[0039] like Figure 1-Figure 5 A galvanometer control correction method shown includes the following steps:

[0040] Step 1: Establish a correction server, which is connected to the SLM printer via a data cable. The SLM printer at least includes a high-definition camera and a galvanometer control system. The high-definition camera is used to take pictures of the processing plane of the SLM printer, and the galvanometer control system is used to control the laser path of the SLM printer.

[0041] In this embodiment, the correction server realizes data exchange with the SLM printer through a network cable.

[0042] The correction server reads the image of the processing plane from the SLM printer, presets several ideal positions in the image, marks a target point at each ideal position, and calculates the actual position data of each target point on the processing plane according to the ratio between the pixel size of the image of the processing plane and the actual size of the processing plane, which is recorded as the conversion ratio;

[0043] All targets are formed into a target matrix, which contains the number and actual position data of each target;

[0044] The conversion ratio is N:1, where N represents the pixel size ratio, 1 represents the actual size ratio of the processing plane, and the value of N is between 0.1 and 1;

[0045] The actual position data is the position of the target point in the world coordinate system on the processing plane.

[0046] like Figure 2 As shown, in the schematic diagram of the mathematical model of the target matrix, plane abcd is represented as the processing plane, and the target matrix Z' is represented as:

[0047]

[0048] Among them, J′ represents the target, J′ 11 represents the first target, R represents the row number of the target, and L represents the column number of the target.

[0049] The target is a point matrix set by the user according to the actual size of the processing plane. The values ​​of R and L can be adjusted according to the user's requirements for the density of the point matrix.

[0050] Step 2: The correction server inputs the target matrix to the SLM printer. The SLM printer controls the test laser to project on the processing plane in sequence according to the target number based on the position data of each target in the target matrix through the galvanometer control system to obtain the projection point corresponding to each target.

[0051] The SLM printer uses a high-definition camera to take pictures of each projection point to form a collection of projection point pictures;

[0052] When calculating position data, the specific steps are as follows:

[0053] Step 2-1: Obtain the actual size of the processing plane and establish the world coordinate system model of the processing plane;

[0054] Get the image of the processing plane and calculate the conversion ratio between the image pixel size and the world coordinate system;

[0055] Step 2-2: According to the conversion ratio, N:1, restore the world coordinate system information of the processing plane in the image of the processing plane; the value of N is between 0.1 and 1;

[0056] Step 2-3: Preset the target matrix in the image of the processing plane, calculate the position of each target in the target matrix in the world coordinate system according to the conversion ratio, that is, the actual position data, and store it.

[0057] like Figure 3 As shown in the figure, after inputting the target matrix Z', due to the pillow deformation of the laser and the error of the galvanometer system, the actual projection point J on the plane abcd is as follows: Figure 3 As shown, there is a certain error between it and the target point, and pillow correction and error correction are required. Figure 4 In the above example, the matrix Z formed by the projection points is expressed as:

[0058]

[0059] Where, J represents the projection point of the laser, J 11 Indicates the first target J′ 11 The corresponding projection point.

[0060] Step 3: The correction server obtains a set of projection point images, calculates the actual position data of each projection point according to the conversion ratio, and constructs a projection point matrix; the projection point matrix contains the number and actual position data of each projection point; and establishes a mapping list between the projection point number and the target point number;

[0061] The actual position data of each projection point is calculated according to the conversion ratio, specifically including calculating the position of the projection point in the world coordinate system corresponding to the pixel position of the projection point in the image according to the conversion ratio.

[0062] The correction server selects 4 target points in the target point matrix to form a unit calibration rectangle, takes the vertex of the upper left corner of the unit calibration rectangle as the base point, searches for the projection point corresponding to the base point in the projection point matrix according to the mapping list, i.e., the base point projection point, compares the actual position data of the base point with the actual position data of the base point projection point, and obtains the deviation value between the two, i.e., the base point error value;

[0063] The target points contained in the unit calibration rectangle are set as the unit calibration target points, and pincushion correction is performed on the projection points corresponding to all the unit calibration target points in the unit calibration rectangle;

[0064] Step 4: After the pincushion correction, perform a translation correction on the unit calibration rectangle according to the base point error value, record the deviation value between the unit calibration target point and its corresponding projection point after the translation correction, that is, the galvanometer error value, and form a galvanometer error matrix;

[0065] like Figure 4 The figure shows the projection point diagram after pincushion correction, where [J 11 , J 1Y , P X1 , P XY ] The target point corresponding to the four vertices constitutes a unit calibration rectangle ( Figure 5 J is not shown 11 , J 1Y , P X1 , P XY The corresponding target points), for the unit calibration rectangle [J′ 11 , J′ 1Y , P′ X1 , P′ XY ], the present invention projects point J 11 The corresponding target J′ 11 As the base point, calculate the projection point J 11 With target J′ 11 After obtaining the base point error, the base point error is loaded into the unit calibration rectangle [J′ 11 , J′ 1Y , P′ X1 , P′ XY ], for the unit calibration rectangle [J′ 11 , J′ 1Y , P′ X1 , P′ XY ] for translation correction, X ranges from 1 to L, Y ranges from 1 to R, and P represents a projection point selected on the plane abcd, that is, P′ X1 and P′ XY Indicates that the unit calibration rectangle is located at the two vertices on the right.

[0066] Since the stepper motor in the galvanometer control system has a certain cumulative error, the present invention records the unit calibration rectangle [J′] after translation correction. 11 , J′ 1Y , P′ X1 , P′ XY ] and their corresponding target points, thereby obtaining the galvanometer error matrix.

[0067] Step 5: The correction server presets an error threshold, and screens the galvanometer error matrix according to the error threshold to obtain all unit calibration targets whose galvanometer error values ​​are within the error threshold range, and form a calibration matrix;

[0068] Since the accumulated error is proportional to the length of the laser path, the present invention presets an error threshold and calculates the unit calibration rectangle [J′] according to the error threshold. 11 , J′ 1Y , P′ X1 , P′ XY ] All projection points are screened, such as Figure 4 As shown, in this embodiment, the unit calibration rectangle [J′ 11 , J′ 1Y , P′ X1 , P′ XY ], the rectangle formed by the projected points [J X1 , J XY , P X1 , P XY ], the deviation values ​​of all the projection points within the rectangle [J X1 , J XY , P X1 , P XY ] After filtering out the projection points within the rectangle [J 11 , J X1 , J XY , J 1Y The target points corresponding to all the projection points in ] constitute the calibration matrix

[0069] Step 6: Divide the processing plane by the calibration matrix to obtain multiple processing areas. Set a safe processing area in each processing area. The distance between the safe processing area and the surrounding areas of the processing area is m times the error threshold. The value of m is between 1.5 and 3. The specific steps include the following:

[0070] Step 6-1: In the row direction, for two adjacent calibration matrices, the unit calibration target point at the upper right corner of the calibration matrix on the left and the base point of the calibration matrix on the right share the same target point;

[0071] like Figure 5 As shown, the calibration matrix With adjacent calibration matrix Ideally, the target J′ is shared X1 , in actual processing, the target point J′ X1 The corresponding projection point J X1 There is a position deviation between the two points. In this embodiment, only the deviation value dx in the horizontal direction is shown, so the target point J′ cannot be directly used. X1 The position data is used as the calibration matrix The base point position data needs to be projected according to the deviation value dx. X1 After correction, the corrected data can be used as the calibration matrix The base point position data can be obtained to eliminate the accumulated error of the galvanometer control system.

[0072] Step 6-2: In the column direction, for two adjacent calibration matrices, the unit calibration target point at the lower left corner of the upper calibration matrix and the base point of the lower calibration matrix share the same target point;

[0073] Step 6-3: When the shape of the calibration matrix needs to be cropped, cropping is performed preferentially in the row direction.

[0074] Since the size of the processing plane is limited, the present invention is to calibrate the matrix After correcting the base point position, the calibration matrix With the calibration matrix There may be a common area between the two calibration matrices, which will affect the normal processing of the workpieces in the two calibration matrices. The present invention sets up a safe processing area in each calibration matrix to eliminate the influence of the common area, thereby ensuring sufficient space for the processing plane and preventing repeated processing.

[0075] Process parts of the same batch or lot number in each safe processing area.

[0076] The galvanometer control correction method described in the present invention solves the technical problem of the cumulative error of the galvanometer and improves the processing accuracy of parts in the same batch. The present invention can reduce the cumulative error of the galvanometer caused by the unit step size, so that its final error range is smaller and easy to operate. Without changing the basic control elements of the galvanometer, the overall processing error of the parts in the same batch is further reduced. The software design is simple, the size of the calibration matrix can be changed according to the user's settings, and it is highly flexible and applicable.

Claims

1. A galvanometer control correction method, characterized in that: The steps include: Step 1: Establish a correction server, which is connected to the SLM printer via a data cable. The SLM printer at least includes a high-definition camera and a galvanometer control system. The high-definition camera is used to take pictures of the processing plane of the SLM printer, and the galvanometer control system is used to control the laser path of the SLM printer. The correction server reads the image of the processing plane from the SLM printer, presets several ideal positions in the image, marks a target point at each ideal position, and calculates the actual position data of each target point on the processing plane according to the ratio between the pixel size of the image of the processing plane and the actual size of the processing plane, which is recorded as the conversion ratio; All targets are formed into a target matrix, which contains the number and actual position data of each target; Step 2: The correction server inputs the target matrix to the SLM printer. The SLM printer controls the test laser to project on the processing plane in sequence according to the target number based on the position data of each target in the target matrix through the galvanometer control system to obtain the projection point corresponding to each target. The SLM printer uses a high-definition camera to take pictures of each projection point to form a collection of projection point pictures; Step 3: The correction server obtains a set of projection point images, calculates the actual position data of each projection point according to the conversion ratio, and constructs a projection point matrix; The projection point matrix contains the number and actual position data of each projection point; a mapping list between the projection point number and the target point number is established; The correction server selects 4 target points in the target point matrix to form a unit calibration rectangle, takes the vertex of the upper left corner of the unit calibration rectangle as the base point, searches for the projection point corresponding to the base point in the projection point matrix according to the mapping list, i.e., the base point projection point, compares the actual position data of the base point with the actual position data of the base point projection point, and obtains the deviation value between the two, i.e., the base point error value; The target points contained in the unit calibration rectangle are set as the unit calibration target points, and pincushion correction is performed on the projection points corresponding to all the unit calibration target points in the unit calibration rectangle; Step 4: After the pincushion correction, perform a translation correction on the unit calibration rectangle according to the base point error value, record the deviation value between the unit calibration target point and its corresponding projection point after the translation correction, that is, the galvanometer error value, and form a galvanometer error matrix; Step 5: The correction server presets an error threshold, and screens the galvanometer error matrix according to the error threshold to obtain all unit calibration targets whose galvanometer error values ​​are within the error threshold range, and form a calibration matrix; Step 6: The processing plane is divided by the calibration matrix to obtain multiple processing areas. A safe processing area is set in each processing area. The distance between the safe processing area and the surrounding areas of the processing area is m times the error threshold, and the value of m is between 1.5 and 3; Process parts of the same batch or lot number in each safe processing area.

2. A galvanometer control correction method as claimed in claim 1, characterized in that: The conversion ratio is N:1, where N represents the pixel size ratio, 1 represents the actual size ratio of the processing plane, and the value of N is between 0.1 and 1; The actual position data is the position of the target point in the world coordinate system on the processing plane.

3. A galvanometer control correction method as claimed in claim 2, characterized in that: When calculating position data, the specific steps are as follows: Step 2-1: Obtain the actual size of the processing plane and establish the world coordinate system model of the processing plane; Get the image of the processing plane and calculate the conversion ratio between the image pixel size and the world coordinate system; Step 2-2: According to the conversion ratio, N:1, restore the world coordinate system information of the processing plane in the image of the processing plane; the value of N is between 0.1 and 1; Step 2-3: Preset the target matrix in the image of the processing plane, calculate the position of each target in the target matrix in the world coordinate system according to the conversion ratio, that is, the actual position data, and store it.

4. A galvanometer control correction method as claimed in claim 3, characterized in that: When executing step 3, the actual position data of each projection point is calculated according to the conversion ratio, specifically including calculating the position of the projection point in the world coordinate system corresponding to the pixel position in the image according to the conversion ratio.

5. A galvanometer control correction method as claimed in claim 3, characterized in that: When executing step 6, the specific steps include: Step 6-1: In the row direction, for two adjacent calibration matrices, the unit calibration target point at the upper right corner of the calibration matrix on the left and the base point of the calibration matrix on the right share the same target point; Step 6-2: In the column direction, for two adjacent calibration matrices, the unit calibration target point at the lower left corner of the upper calibration matrix and the base point of the lower calibration matrix share the same target point; Step 6-3: When the shape of the calibration matrix needs to be cropped, cropping is performed preferentially in the row direction.

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