Centering method for four-axis ball polishing device

Abstract

The centering method of the four-axis sphere polishing device of the present invention includes the following steps: Step 1: Select one grinding axis as the reference axis, denoted as axis IV, and the other three grinding axes as the axes to be calibrated, denoted as axis I, axis II, and axis III; Step 2: Select any point on the axis of the reference axis as the centering position; Step 3: Calibrate axis I: S3.1: Determine the positions of the two cameras; S3.2: Using axis IV as a reference, calibrate the x-direction position of axis I and extract the error value x1; then, calibrate the angle of axis I, align the axis of axis I with the spatial intersection point O, and extract the error value y1; calculate the centering error between axis I and axis IV. If the centering error is less than or equal to a threshold, axis I calibration is complete; Step 4: Calibrate axis II in the same way as calibrating axis I in step 3; Step 5: Calibrate axis III in the same way as calibrating axis I in step 3. This comparative method has the advantages of being easy to implement and having high centering accuracy.

Description

Technical Field

[0001] This invention relates to the field of precision machining technology for spheres, and specifically to a centering method for a four-axis sphere polishing device. Background Technology

[0002] Precision spheres are key components in high-end mechanical basic parts such as high-performance bearings, high-precision ball screws, and high-precision linear guides. Their shape accuracy, surface quality, and dimensional consistency directly affect the performance and lifespan of basic mechanical functional parts, and thus the performance of high-end equipment. Precision machining technology occupies an indispensable position in many fields. After the sphere blank is formed, polishing is the key process for the final sphere.

[0003] In the current field of spherical machining technology, the four-axis spherical polishing device possesses the characteristics of high machining accuracy and high material removal rate. The core component of this polishing device is the four-axis grinding tool, which consists of four grinding axes arranged symmetrically in three-dimensional space. Driven by servo motors, the grinding axes can rotate forward and backward. Based on the positional relationship between the vertical grinding axis and the other three axes, the device can be divided into two configurations: an upright regular tetrahedron and an inverted regular tetrahedron. Of the four grinding axes, one is arranged in a plumb position, while the other three are arranged at an angle of β = 19.47° to the horizontal plane, with an included angle ψ = 120° projected onto the horizontal plane. From a spatial perspective, these four grinding axes form a regular tetrahedron, with the included angle between any two axes being φ = 109.47°. The body center of this regular tetrahedron, the intersection of all the axes, is precisely the location of the center of the spherical blank being processed.

[0004] To ensure uniformity in four-axis machining, centering is essential before machining spheres. Centering essentially involves aligning the four grinding axes to their ideal positions during installation. However, the centering process in existing four-axis grinding machines is difficult, and there is currently no publicly available centering method for four-axis sphere polishing devices. Technicians typically rely on visual inspection, resulting in poor centering accuracy and an inability to quantify the error. Inaccurate centering directly leads to poor sphere grinding precision. Therefore, providing a method to effectively improve the centering accuracy of four-axis grinding machines is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] To overcome the shortcomings of the prior art, this invention provides a centering method for a four-axis sphere polishing device. This comparative method has the advantages of being easy to implement and having high centering accuracy. At the same time, the centering method of this invention can quantify error values, providing a reference for process research.

[0006] The technical solution of this application is as follows:

[0007] The centering method of the four-axis sphere polishing device includes the following steps:

[0008] Step 1: Select one grinding axis as the reference axis, denoted as axis IV, and the other three grinding axes as the axes to be calibrated, denoted as axis I, axis II, and axis III; define the plane formed by the reference axis and the axes to be calibrated as coplanar, with axis I, axis II, and axis III corresponding to coplanar I, coplanar II, and coplanar III, respectively; define the plane containing the reference axis and perpendicular to the coplanar as the vertical plane, with coplanar I, coplanar II, and coplanar III corresponding to vertical plane I, vertical plane II, and vertical plane III, respectively.

[0009] Step 2: Select any point on the reference axis as the centering position, and denot it as the spatial intersection point O;

[0010] Step 3: Calibrate Axis I:

[0011] S3.1 Determine the positions of the two cameras: Adjust the position of the first camera until the axes I and IV in the image are parallel. At this time, the plane in which the first camera is located is coplanar I. Set the second camera at a 90° angle to the first camera. The plane in which the second camera is located is perpendicular to plane I. Set the coordinate system, where the x-axis is perpendicular to coplanar I and the y-axis is located on the axis of the reference axis.

[0012] S3.2. Using axis IV as a reference, align the axis of axis I with the axis of axis IV to calibrate the x-direction position of axis I, and extract the deviation between the two axes as the error value x1. Then, align the axis of axis I with the axis of axis IV to calibrate the angle of axis I, ensuring the angle error is within the allowable range. Next, calibrate the y-direction position of axis I, align the axis of axis I with the spatial intersection point O, and extract the deviation between the axis of axis I and point O as the error value y1. Calculate the alignment error between axis I and axis IV. If the alignment error is less than or equal to the threshold, axis I calibration is complete. If the alignment error is greater than the threshold, recalibrate the x-direction and y-direction until the alignment error is less than or equal to the threshold.

[0013] Step 4: Calibrate axis II in the same way as calibrating axis I in step 3;

[0014] Step 5: Calibrate axis III in the same way as calibrating axis I in step 3.

[0015] Compared with the prior art, the centering method of the present invention can improve the centering accuracy of the four-axis ball polishing device by adopting specific method steps, thereby improving the processing accuracy of the four-axis polishing device. During centering, a reference axis is first selected, a coordinate system is set, and the camera is set according to specific rules. Then, the axis to be calibrated is calibrated. The centering error and angle error can be controlled within the set range. Moreover, the whole process is easy to operate and can be applied in industry. At the same time, the centering method of the present invention can quantify the error value, providing a reference for process research.

[0016] Furthermore, as a preferred embodiment, in step one of the centering method of the aforementioned four-axis spherical polishing device, the grinding axis in the direction of the plumb bob is selected as the reference axis, denoted as axis IV, and adjusted to be perpendicular to the worktable and aligned with the center of the feeding device. Selecting the grinding axis in the direction of the plumb bob as the reference axis when implementing the method of this invention makes subsequent operations more convenient.

[0017] Furthermore, as a preferred option, in step two of the centering method of the aforementioned four-axis spherical polishing device, the intersection point of the reference axis and the end face of the polishing tool is preferentially selected as the spatial intersection point O.

[0018] Furthermore, as a preferred embodiment, in the centering method of the aforementioned four-axis spherical polishing device, the centering error threshold is 10 micrometers. From the perspective of processing accuracy, the smaller the centering error threshold, the better. However, the smaller the centering error threshold, the more difficult it is to center, and it may even lead to repeated calibrations failing to meet the requirements. Setting the centering error threshold to 10 micrometers can ensure the processing accuracy of four-axis grinding while facilitating centering.

[0019] Furthermore, as a preferred embodiment, in the centering method of the aforementioned four-axis spherical polishing device, the allowable range of the angular error is ±10 arcseconds. Similarly to the centering error, from the perspective of machining accuracy, the smaller the angular error, the better. However, if the allowable range of the angular error is too narrow, it will increase the difficulty of centering and may even lead to repeated calibrations failing to meet the requirements. Controlling the angular error within 10 arcseconds can ensure the machining accuracy of four-axis grinding while facilitating centering.

[0020] Furthermore, as a preferred embodiment, the centering method of the aforementioned four-axis sphere polishing device includes a first camera, a second camera, and a computer connected to the first and second cameras via signal transmission. During operation, the first and second cameras transmit the captured images to the computer, and the operator adjusts the axis to be calibrated based on the images displayed on the computer to achieve the calibration purpose. Using a computer to process the images improves efficiency and reliability.

[0021] Furthermore, as a preferred embodiment, in the centering method of the aforementioned four-axis sphere polishing device, during centering, a computer analyzes the image to calculate the centering error and angle error. Using a computer to analyze the image and calculate the centering error and angle error not only ensures high accuracy but also high efficiency.

[0022] Furthermore, as a preferred embodiment, the centering method of the aforementioned four-axis spherical polishing device further includes a light source; the first camera and the second camera are each equipped with a set of light sources. The placement of the light sources can reduce image noise or distortion caused by ambient light fluctuations or reflections from the object's surface.

[0023] Furthermore, as a preferred embodiment, in the centering method of the aforementioned four-axis sphere polishing device, both the first camera and the second camera are equipped with magnifying lenses.

[0024] Furthermore, as a preferred embodiment, in the centering method of the aforementioned four-axis spherical polishing device, during centering, the grinding shaft drive device is activated to make the grinding shaft rotate; the computer performs image fusion on the video recorded by the camera to obtain the contour of the grinding shaft during rotation. This avoids the radial runout of the grinding shaft affecting the centering accuracy. Attached Figure Description

[0025] Figure 1 This is a schematic diagram illustrating the principle of the method for centering the object according to the present invention;

[0026] Figure 2 This is a schematic diagram of the calibration based on the image captured by the first camera in the coplanar position in the centering method of the present invention (calibrating the I-axis);

[0027] Figure 3 This is a schematic diagram of the calibration based on the image captured by the second camera in the vertical plane in the centering method of the present invention (calibration of axis I).

[0028] Figure 4 This is a schematic diagram (top view) of the state when calibrating the I-axis using the method of this invention;

[0029] Figure 5 This is a schematic diagram (top view) of the state when calibrating the I-axis using the method of this invention;

[0030] Figure 6 This is a schematic diagram (top view) of the state when calibrating the III axis using the method of the present invention;

[0031] Figure 7 It is the actual magnified image of the first camera in the coplanar position;

[0032] Figure 8 It is an actual magnified image of the second camera in the vertical plane.

[0033] Figure label:

[0034] 1-Axis IV; 2-Axis I; 3-Axis II; 4-Axis III; 5-First camera; 6-Second camera. Detailed Implementation

[0035] The present application will be further described below with reference to the accompanying drawings and embodiments, but this should not be construed as limiting the present application.

[0036] Example (see) Figure 1-8 ):

[0037] See Figure 1In this embodiment, the hardware for achieving calibration includes a first camera 5, a second camera 6, and a computer connected to the first camera 5 and the second camera 6 via signals. During operation, the first camera 5 and the second camera 6 transmit the captured images to the computer, and the operator adjusts the axis to be calibrated based on the images displayed on the computer to achieve the calibration purpose.

[0038] In this embodiment, during alignment, the computer analyzes the image and calculates the alignment error and angle error.

[0039] In this embodiment, the hardware for implementing the alignment method also includes a light source; the first camera and the second camera are each equipped with a set of light sources.

[0040] In this embodiment, both the first camera and the second camera are equipped with magnifying lenses.

[0041] In this embodiment, during alignment, the grinding shaft drive device is activated to make the grinding shaft rotate; the computer performs image fusion on the video recorded by the camera to obtain the contour of the grinding shaft during the rotation process.

[0042] In this embodiment, the centering method of the four-axis sphere polishing device includes the following steps:

[0043] Step 1: Select the grinding axis in the direction of the plumb bob as the reference axis, denoted as axis IV1. The other three grinding axes are the axes to be calibrated, denoted as axis I2, axis II3, and axis III4. Set the plane formed by the reference axis and the axes to be calibrated as coplanar. Axis I2, axis II3, and axis III4 correspond to coplanar I, coplanar II, and coplanar III, respectively. Set the plane containing the reference axis and perpendicular to the coplanar plane as the vertical plane. Coplanar I, coplanar II, and coplanar III correspond to vertical plane I, vertical plane II, and vertical plane III, respectively.

[0044] Step 2: Select the intersection of the reference axis and the end face of the grinding tool as the centering position, and record it as the spatial intersection point O.

[0045] Step 3: Calibrate Axis I:

[0046] S3.1 Determine the positions of the two cameras: Adjust the position of the first camera until the axes I and IV in the image are parallel. At this time, the plane in which the first camera is located is coplanar I. Set the second camera at a 90° angle to the first camera. The plane in which the second camera is located is perpendicular to plane I. Set the coordinate system, where the x-axis is perpendicular to coplanar I and the y-axis is located on the axis of the reference axis.

[0047] S3.2. Using axis IV as a reference, align the axis of axis I with the axis of axis IV to calibrate the x-direction position of axis I, and extract the deviation between the two axes as the error value. Then, align the axis of axis I with the axis of axis IV to calibrate the angle of axis I. The computer outputs an angle error of 6 arcseconds, which is within the allowable range (10 arcseconds). The angle calibration of axis I is then complete. Next, calibrate the y-direction position of axis I by aligning the axis of axis I with the spatial intersection point O and extracting the deviation between the axis of axis I and point O as the error value. The computer calculates the alignment error between axis I and axis IV. If the alignment error exceeds the set threshold (10 micrometers), after recalibrating in the x and y directions, the x-direction error value is... y-direction error value , centering error If the value is less than 10 micrometers, the I-axis calibration is complete;

[0048] Step 4: Calibrate Axis II:

[0049] S4.1 Determine the positions of the two cameras: Adjust the position of the first camera until the axes II and IV in the image are parallel. At this time, the plane in which the first camera is located is coplanar I. Set the second camera at a 90° angle to the first camera. The plane in which the second camera is located is perpendicular to plane I. Set the coordinate system, where the x-axis is perpendicular to coplanar I and the y-axis is located on the axis of the reference axis.

[0050] S4.2. Using axis IV as a reference, align the axis of axis II with the axis of axis IV to calibrate the x-direction position of axis II, and extract the deviation between the two axes as the error value. Then, align the axis of axis II with the axis of axis IV to calibrate the angle of axis II. The computer outputs an angle error of 8 arcseconds, which is within the allowable range (10 arcseconds). The angle calibration is then complete. Next, calibrate the y-direction position of axis II by aligning the axis of axis II with the spatial intersection point O and extracting the deviation between the axis of axis II and point O as the error value. ; Calculate the alignment error between axis II and axis IV. If the alignment error exceeds the set threshold (10 micrometers), after recalibrating in the x and y directions, the x-direction error value is... y-direction error value , centering error If the value is less than 10 micrometers, the II-axis calibration is complete.

[0051] Step 5: Calibrate Axis III:

[0052] S4.1 Determine the positions of the two cameras: Adjust the position of the first camera until the axes III and IV in the image are parallel. At this time, the plane in which the first camera is located is coplanar I. Set the second camera at a 90° angle to the first camera. The plane in which the second camera is located is perpendicular to plane I. Set the coordinate system, where the x-axis is perpendicular to coplanar I and the y-axis is located on the axis of the reference axis.

[0053] S4.2. Using axis IV as a reference, align the axis of axis III with the axis of axis IV to calibrate the x-direction position of axis III, and extract the deviation between the two axes as the error value. Then, align the axis of axis III with the axis of axis IV to calibrate the angle of axis III. The computer outputs an angle error of 8 arcseconds, which is within the allowable range (10 arcseconds). The angle calibration is then complete. Next, calibrate the y-direction position of axis III by aligning the axis of axis III with the spatial intersection point O, and extract the deviation between the axis of axis III and point O as the error value. Calculate the alignment error between axis III and axis IV. If the centering error is less than the set threshold (10 micrometers), the III-axis calibration is complete;

[0054] Step 6: Calculate the final alignment error In this embodiment, take , , The maximum value in .

[0055] In this embodiment, 50 single-crystal silicon microspheres with a diameter of 2.5 mm were prepared. Before processing, their initial roundness error distribution was measured to be 0.9–1.5 μm, and their initial surface roughness Ra was 130–190 nm. They were divided into two groups, one centered by ordinary visual inspection and the other centered by the method of this invention. One group was randomly selected from each group after processing. Table 1 shows the partial processing results of centeredness by ordinary visual inspection, and Table 2 shows the partial processing results of centeredness by the method of this invention.

[0056] Based on a comprehensive analysis of the experimental results, the following conclusions can be drawn: the surface roughness of both groups of small balls was significantly improved, but the roundness change was not significant when aligned with the naked eye, with a roundness error distribution of 0.9–2.0 μm, and some small balls even showed a deterioration in roundness. However, when aligned with the method of this invention, the roundness of the processed balls was significantly improved, with a roundness error distribution of 0.4–1.1 μm, achieving a higher roundness accuracy.

[0057] Table 1:

[0058]

[0059] Table 2:

[0060]

[0061] The centering process of existing four-axis grinding machines is quite difficult, and there is currently no publicly available centering method for four-axis ball polishing devices. Technicians typically rely on visual inspection, resulting in poor centering accuracy and an inability to quantify the error value. Inaccurate centering directly leads to poor ball polishing accuracy, especially roundness error. The method of this invention provides a new method and means for centering in four-axis ball polishing devices, which has the advantages of being easy to implement and having high centering accuracy, and has good practical benefits.

[0062] The foregoing general description of the invention and its specific embodiments should not be construed as a limitation on the technical solution of the invention. Those skilled in the art, based on the disclosure of this application, can add, reduce, or combine the disclosed technical features in the foregoing general description and / or specific embodiments (including examples) without departing from the constituent elements of the invention, to form other technical solutions within the scope of protection of this application.

Claims

1. A centering method for a four-axis sphere polishing device, characterized in that, Includes the following steps: Step 1: Select one grinding axis as the reference axis, denoted as axis IV, and the other three grinding axes as the axes to be calibrated, denoted as axis I, axis II, and axis III; define the plane formed by the reference axis and the axes to be calibrated as coplanar, with axis I, axis II, and axis III corresponding to coplanar I, coplanar II, and coplanar III, respectively; define the plane containing the reference axis and perpendicular to the coplanar as the vertical plane, with coplanar I, coplanar II, and coplanar III corresponding to vertical plane I, vertical plane II, and vertical plane III, respectively. Step 2: Select any point on the reference axis as the centering position, and denot it as the spatial intersection point O; Step 3: Calibrate Axis I: S3.1 Determine the positions of the two cameras: Adjust the position of the first camera until the axes I and IV in the image are parallel. At this time, the plane in which the first camera is located is coplanar I. Set the second camera at a 90° angle to the first camera. The plane in which the second camera is located is perpendicular to plane I. Set the coordinate system, where the x-axis is perpendicular to coplanar I and the y-axis is located on the axis of the reference axis. S3.

2. Using axis IV as a reference, align the axis of axis I with the axis of axis IV to calibrate the x-direction position of axis I, and extract the deviation between the two axes as the error value x1; then, align the axis of axis I with the axis of axis IV to calibrate the angle of axis I, ensuring the angle error is within the allowable range; next, calibrate the y-direction position of axis I, align the axis of axis I with the spatial intersection point O, and extract the deviation between the axis of axis I and point O as the error value y1; calculate the alignment error between axis I and axis IV. If the alignment error is less than or equal to the threshold, the I-axis calibration is complete. If the alignment error is greater than the threshold, the x-direction and y-direction calibrations are repeated until the alignment error is less than or equal to the threshold. Step 4: Calibrate axis II in the same way as calibrating axis I in step 3; Step 5: Calibrate axis III in the same way as calibrating axis I in step 3.

2. The centering method of the four-axis sphere polishing device according to claim 1, characterized in that: In step one, the grinding shaft in the direction of the plumb bob is selected as the reference shaft.

3. The centering method of the four-axis sphere polishing device according to claim 1, characterized in that: In step two, the intersection of the reference axis and the end face of the grinding tool is selected as spatial intersection point O.

4. The centering method of the four-axis sphere polishing device according to any one of claims 1-3, characterized in that: The threshold for the alignment error is 10 micrometers.

5. The centering method of the four-axis sphere polishing device according to any one of claims 1-3, characterized in that: The allowable range for the angle error is ±10 arcseconds.

6. The centering method of the four-axis sphere polishing apparatus according to any one of claims 1-3, characterized in that, The hardware for implementing this alignment method includes a first camera, a second camera, and a computer connected to the first camera and the second camera via signals. During operation, the first camera and the second camera transmit the captured images to the computer, and the operator adjusts the axis to be calibrated based on the images displayed on the computer to achieve the calibration purpose.

7. The centering method of the four-axis sphere polishing device according to claim 6, characterized in that, During alignment, the computer analyzes the image and calculates the alignment error and angle error.

8. The centering method of the four-axis sphere polishing device according to claim 6, characterized in that, The hardware for implementing this alignment method also includes a light source; the first camera and the second camera are each equipped with a set of light sources.

9. The centering method of the four-axis sphere polishing device according to claim 6, characterized in that, Both the first and second cameras are equipped with magnifying lenses.

10. The centering method of the four-axis sphere polishing device according to claim 6, characterized in that: When aligned, the grinding shaft drive device is activated to make the grinding shaft rotate; the computer performs image fusion on the video recorded by the camera to obtain the contour of the grinding shaft during the rotation process.

Images