Method for measuring and compensating zero error and axis error of rotating shaft of CA-type five-axis machine tool based on relative position measurement of laser spots

Abstract

The invention discloses a laser spot relative position measurement-based CA type five-axis machine tool rotating shaft zero error and axis error measurement compensation method. The method comprises the following steps of S1, detection system preparation: clamping or fixing a laser pen to a main shaft; s2, the A-axis zero error is measured and compensated, wherein the A-axis zero error is defined as the angle deviation between the actual posture and the theoretical ideal posture of the execution tail end of the machine tool when the rotating shaft is set to be at the 0-degree reference position; s3, measuring and compensating a C-axis zero error, wherein the C-axis zero error is defined as the angle deviation between the actual posture and the theoretical ideal posture of the execution tail end of the machine tool when the rotating shaft is set to be at the 0-degree reference position; s4, performing measurement compensation on the deviation of the A axis-main axis rotation center line in the Y direction; s5, measuring and compensating the deviation of the C-axis-main axis rotation center line in the Y direction; and S6, performing measurement compensation on the deviation of the C-axis-main axis rotation center line in the X direction.

Description

Technical Field

[0001] This invention belongs to the field of multi-axis CNC machining accuracy detection technology, specifically relating to a method for measuring and compensating for the zero-position error and axis error of a CA-type five-axis machine tool based on the relative position measurement of a laser spot. Background Technology

[0002] Five-axis CNC machine tools are core equipment for machining complex curved surface parts and are widely used in high-end manufacturing fields such as aerospace and automotive molds. Among them, the CA double-swivel head five-axis machine tool (referred to as "CA swivel five-axis machine tool") has become one of the most widely used five-axis machine tool configurations due to its outstanding advantages of flexibility, efficiency, and large working range of rotary axes. Compared with traditional three-axis machine tools, the CA swivel five-axis machine tool adds two rotary axes, which significantly increases the difficulty of detecting and ensuring its machining accuracy. Among these, the detection problems of rotary axis zero-position error and rotary axis axis error are the most typical. Rotary axis zero-position error is a key factor affecting the accuracy of five-axis linkage. Specifically, it refers to the angular deviation between the actual posture of the machine tool's execution end and the theoretical ideal posture when the rotary axis is set to the 0° reference position. Compared with other error sources, the influencing factors of rotary axis zero-position error are more complex, covering multiple aspects such as transmission structure wear, coordinate system parameter settings, and machine tool compensation function configuration. It is particularly important to note that after each machine tool maintenance or debugging, errors such as incorrect operation of compensation parameters or incorrect setting of coordinate system references can easily lead to zero-position misalignment of critical rotary axes such as the A-axis, thus affecting machining accuracy. Therefore, routine monitoring of rotary axis zero-position error is of significant practical importance for ensuring machine tool accuracy and preventing errors in daily operations. Rotary axis axis error refers to the error caused by factors such as manufacturing defects in machine tool components, assembly process deviations, and impact wear during long-term operation, which prevent the rotary axis's rotation center line from maintaining a theoretically perpendicular or coincident state with the spindle's rotation center line, resulting in positional offset and ultimately causing a deviation between the actual position and the ideal position of the machine tool's execution end (some companies classify this type of error into categories such as rotational error and RTCP error in engineering practice, with slight differences in the relevant definitions and coverage; the definition of "rotary axis axis error" in this article is based on the above description). This error is also one of the main factors affecting the accuracy of five-axis linkage machining.

[0003] The conventional method for measuring and compensating for the zero-position error and axis error of a five-axis machine tool's rotary axis is to use a mandrel and a dial indicator. Specifically, a cylindrical mandrel is clamped onto the spindle, and the machine tool is operated to move the rotary axis to multiple specific positions to make contact with the dial indicator. The dial indicator readings under different conditions are used to calculate the error measurement results, and the compensation value is calculated and filled into the corresponding parameters of the CNC system. This method can measure and compensate for the axis error and zero-position error of the rotary axis relatively accurately. However, the operation involves setting up the dial indicator and aligning the mandrel, which is relatively complex. In addition, the contact between the mandrel and the dial indicator during the measurement process may cause interference or impact if the operation is improper or a sudden failure occurs, damaging the machine tool's transmission components and the dial indicator, posing a risk of equipment damage. To address the aforementioned issues, IBS in the Netherlands designed and developed the Rotary Analyzer, a rotary shaft analyzer using eddy current sensors. It employs three non-contact eddy current sensors and a ceramic ball head for measuring the error of the rotary shaft, avoiding direct contact between the ball head and the sensor and offering extremely high measurement accuracy. However, this instrument is expensive. Furthermore, due to the measurement characteristics of eddy current sensors, the ball head must be very close to the sensor during the measurement process, which also carries the risk of accidental damage to machine tools and valuable instruments. Summary of the Invention

[0004] The purpose of this invention is to solve the above-mentioned problems and provide a method for measuring and compensating for the zero-position error and axis error of a CA-type five-axis machine tool based on the relative position measurement of a laser spot, which is simple to operate, low in cost, and eliminates the risk of collision while ensuring measurement accuracy.

[0005] To solve the above-mentioned technical problems, the technical solution of the present invention is: a method for measuring and compensating the zero-position error and axis error of a rotary axis of a CA-type five-axis machine tool based on the relative position measurement of a laser spot, characterized by comprising the following steps:

[0006] S1. Detection system preparation: Clamp or fix the laser pointer to the spindle, ensuring that the laser beam path and the spindle rotation center are on the same straight line, and place the spot position sensor on the worktable;

[0007] S2. Measurement and compensation for A-axis zero position error: A-axis zero position error is defined as the angular deviation between the actual posture of the machine tool execution end and the theoretical ideal posture when the rotary axis is set to 0° reference position.

[0008] S3. Measurement and compensation for C-axis zero position error: C-axis zero position error is defined as the angular deviation between the actual posture of the machine tool execution end and the theoretical ideal posture when the rotary axis is set to 0° reference position.

[0009] S4. Measure and compensate for the deviation of the A-axis-spindle rotation center line in the Y direction;

[0010] S5. Measure and compensate for the deviation of the C-axis-spindle rotation center line in the Y direction;

[0011] S6. Measure and compensate for the deviation of the C-axis-spindle rotation center line in the X direction.

[0012] Furthermore, step S2 includes the following sub-steps:

[0013] S21. Place the light spot position sensor horizontally, with the sensor plane parallel to the XY plane;

[0014] S22. Keep both the A-axis and C-axis at the 0 position, and move the translation axis so that the light spot falls near the center of the position sensor, and the end of the laser pointer is 30-50mm away from the sensor. Record the center position of the light spot read by the sensor at this moment.

[0015] S23. Move the Z-axis down a distance Δz and record the center position of the light spot read by the sensor at this moment;

[0016] S24. Calculate the deviation ΔL1 of the center position of the two light spots in the Y direction, and the zero-position error of the A-axis. It can be calculated using the following equation:

[0017] ;

[0018] S25. Compensate for the zero-position accuracy of the A-axis: Move the A-axis... The compensation can be completed by resetting the zero position of the coordinate system.

[0019] Furthermore, step S3 includes the following sub-steps:

[0020] S31. Place the spot position sensor vertically, with the sensor plane parallel to the XZ plane;

[0021] S32. Move axis A to 90°, keep axis C at 0, and move translation axis so that the light spot falls near the center of the position sensor, and the end of the laser pointer is 30-50mm away from the sensor. Record the center position of the light spot read by the sensor at this moment.

[0022] S33. Move the Y-axis to the right by a distance Δy, and record the center position of the light spot read by the sensor at this moment;

[0023] S34. Calculate the deviation ΔL2 of the center position of the two light spots in the Y direction, and the zero-position error of the C-axis. It can be calculated using the following equation:

[0024] ;

[0025] S35. Compensate for C-axis zero-position accuracy: Move the C-axis. The compensation can be completed by resetting the zero position of the coordinate system.

[0026] Furthermore, step S4 also includes the following sub-steps:

[0027] S41. Place the spot position sensor vertically, with the sensor plane parallel to the XZ plane;

[0028] S42. Keep the C-axis at the 0 position, move the A-axis to the -90° position, and move the translation axis to make the light spot fall near the center of the position sensor. Record the center position of the light spot read by the sensor at this moment.

[0029] S43. Rotate the spot sensor 180° around the Z direction in place, move the A axis to the 90° position, move the translation axis to move the machine tool spindle to the other side of the sensor, and ensure that the Z axis position is the same as in step S22. Record the center position of the spot read by the sensor at this moment.

[0030] S44. Calculate the deviation ΔL3 of the center position of the two light spots in the vertical direction (Z direction), and the deviation of the A-axis-major axis rotation center line in the Y direction. It can be calculated using the following equation:

[0031] ;

[0032] S45, will The numerical value is written into the corresponding compensation parameter in the CNC system, which can complete the compensation for the deviation of the A-axis-spindle rotation center line in the Y direction.

[0033] Furthermore, step S5 includes the following sub-steps:

[0034] S51. Place the light spot position sensor horizontally, with the sensor plane parallel to the XY plane;

[0035] S52. Keep the A-axis at position 0, move the C-axis to position 0, and move the translation axis so that the light spot falls near the center of the position sensor. Record the center position of the light spot read by the sensor at this moment.

[0036] S53. Move the C-axis to the 180° position and record the center position of the light spot read by the sensor at this moment;

[0037] S54. Calculate the deviation ΔL4 between the two spot center positions in the Y direction, and the deviation of the C-axis-major axis rotation center line in the Y direction. It can be calculated using the following equation:

[0038] .

[0039] S55, will The value is written into the corresponding compensation parameter in the CNC system, which completes the compensation for the deviation of the C-axis-spindle rotation center line in the Y direction.

[0040] Furthermore, step S6 includes the following sub-steps:

[0041] S61. Keep the light spot position sensor horizontally positioned, with the sensor plane parallel to the XY plane;

[0042] S62. Keep the A-axis at the 0 position, move the C-axis to the 90° position, and move the translation axis to make the light spot fall near the center of the position sensor. Record the center position of the light spot read by the sensor at this moment.

[0043] S63. Move the C-axis to the 270° position and record the center position of the light spot read by the sensor at this moment;

[0044] S64. Calculate the deviation ΔL5 between the two spot center positions in the X direction, and the deviation of the C-axis-main axis rotation center line in the X direction. It can be calculated using the following equation:

[0045] ;

[0046] S65, will The numerical value is written into the corresponding compensation parameter in the CNC system, which completes the compensation for the deviation of the C-axis-spindle rotation center line in the X direction.

[0047] The beneficial effects of this invention are:

[0048] 1. The method for measuring and compensating the zero-position error and axis error of the rotary axis of a CA-type five-axis machine tool based on the relative position measurement of laser spot provided by the present invention has specific advantages in terms of cost, operation difficulty and accuracy.

[0049] 2. Compared with traditional manual inspection methods based on mandrels and dial indicators, the present invention is simpler to operate, and the optical measurement method has higher accuracy, avoiding measurement errors caused by factors such as mandrel straightness. Furthermore, it does not involve contact between the dial indicator and the mandrel, thus avoiding collision damage caused by improper operation or machine tool failure.

[0050] 3. Compared with specialized equipment such as rotary shaft analyzers and angular pendulum instruments, this invention does not require specialized software, is easy to operate, and does not require the purchase of specialized instruments, thus reducing costs. Attached Figure Description

[0051] Figure 1 This is a comparison diagram of the angular deviation between the actual posture and the theoretical ideal posture of the machine tool execution end of the present invention;

[0052] Figure 2This is a schematic diagram of the center position of the light spot read by the sensor after the Z-axis descends a certain distance Δz according to the present invention;

[0053] Figure 3 This is a schematic diagram comparing the angle deviation between the actual posture and the theoretical ideal posture of the end effector of the bed in this invention;

[0054] Figure 4 This is a schematic diagram of the sensor recording the center position of the light spot after the Y-axis is moved to the right by a distance Δy according to the present invention;

[0055] Figure 5 This is a schematic diagram showing the deviation between the A-axis and the rotation center of the main shaft in the Y direction of the present invention;

[0056] Figure 6 This is a schematic diagram of the center position of the light spot read by the sensor in step S43 of the present invention;

[0057] Figure 7 This is a schematic diagram showing the deviation of the C-axis-spindle rotation center line in the Y direction of the present invention;

[0058] Figure 8 This is a schematic diagram showing the center position of the light spot read by the sensor when the C-axis is moved to a 180° position according to the present invention;

[0059] Figure 9 This is a schematic diagram showing the deviation of the C-axis-spindle rotation center line in the X direction of the present invention;

[0060] Figure 10 This is a schematic diagram of the center position of the light spot read by the sensor when the C-axis of the present invention moves to a position of 270°. Detailed Implementation

[0061] The present invention will be further described below with reference to the accompanying drawings and specific embodiments:

[0062] like Figures 1 to 10 As shown, the present invention provides a method for measuring and compensating for the zero-position error and axis error of a CA-type five-axis machine tool based on the relative position measurement of a laser spot, comprising the following steps:

[0063] S1. Detection system preparation: Clamp or fix the laser pointer to the spindle, ensuring that the laser beam path and the spindle rotation center are on the same straight line, and place the spot position sensor on the worktable.

[0064] S2. Measurement and compensation for A-axis zero-position error: The A-axis zero-position error is defined as the angular deviation between the actual posture of the machine tool's end effector and the theoretical ideal posture when the rotary axis is set to the 0° reference position. Figure 1 As shown.

[0065] In this step, the zero-position error of the A-axis is abbreviated as A0. Step S2 includes the following sub-steps:

[0066] S21. Place the light spot position sensor horizontally, with the sensor plane parallel to the XY plane.

[0067] S22. Keep both the A-axis and C-axis at the 0 position, and move the translation axis so that the light spot falls near the center of the position sensor, and the end of the laser pointer is 30-50mm away from the sensor. Record the center position of the light spot read by the sensor at this moment.

[0068] S23. Lower the Z-axis by a distance Δz, and record the center position of the light spot read by the sensor at this moment. Figure 2 As shown.

[0069] S24. Calculate the deviation ΔL1 of the center position of the two light spots in the Y direction, and the zero-position error of the A-axis. It can be calculated using the following equation:

[0070] .

[0071] S25. Compensate for the zero-position accuracy of the A-axis: Move the A-axis... The compensation can be completed by resetting the zero position of the coordinate system.

[0072] S3. Measurement and compensation for C-axis zero-position error: The C-axis zero-position error is defined as the angular deviation between the actual posture of the machine tool's end effector and the theoretical ideal posture when the rotary axis is set to the 0° reference position. Figure 3 As shown.

[0073] In this step, the C-axis zero-position error is abbreviated as C0. Step S3 includes the following sub-steps:

[0074] S31. Place the spot position sensor vertically, with the sensor plane parallel to the XZ plane.

[0075] S32. Move axis A to 90°, keep axis C at 0, and move the translation axis so that the light spot falls near the center of the position sensor, and the end of the laser pointer is 30-50mm away from the sensor. Record the center position of the light spot read by the sensor at this moment.

[0076] S33. Move the Y-axis to the right by a distance Δy, and record the center position of the light spot read by the sensor at this moment. Figure 4 As shown.

[0077] S34. Calculate the deviation ΔL2 of the center position of the two light spots in the Y direction, and the zero-position error of the C-axis. It can be calculated using the following equation:

[0078] .

[0079] S35. Compensate for C-axis zero-position accuracy: Move the C-axis. The compensation can be completed by resetting the zero position of the coordinate system.

[0080] S4. Measure and compensate for the deviation of the A-axis-spindle rotation center line in the Y direction.

[0081] The deviation of the A-axis from the rotation center of the spindle in the Y direction is as follows: Figure 5 As shown, step S4 also includes the following sub-steps:

[0082] S41. Place the spot position sensor vertically, with the sensor plane parallel to the XZ plane.

[0083] S42. Keep the C-axis at the 0 position, move the A-axis to the -90° position, and move the translation axis so that the light spot falls near the center of the position sensor. Record the center position of the light spot read by the sensor at this moment.

[0084] S43. Rotate the spot sensor 180° around the Z-axis in place, move the A-axis to the 90° position, and move the translation axis to move the machine tool spindle to the other side of the sensor, ensuring that the Z-axis position is the same as in step S22. Record the center position of the spot read by the sensor at this moment. Figure 6 As shown.

[0085] S44. Calculate the deviation ΔL3 of the center position of the two light spots in the vertical direction (Z direction), and the deviation of the A-axis-major axis rotation center line in the Y direction. It can be calculated using the following equation:

[0086] .

[0087] S45, will The value is written into the corresponding compensation parameter in the CNC system. Taking the Siemens 840D series CNC system as an example, the value is directly filled into the 24550[1] parameter to complete the compensation of the deviation of the A-axis-spindle rotation center line in the Y direction.

[0088] S5. Measure and compensate for the deviation of the C-axis-spindle rotation center line in the Y direction.

[0089] The deviation of the C-axis - the spindle rotation center line in the Y direction is as follows: Figure 7 As shown, step S5 includes the following sub-steps:

[0090] S51. Place the light spot position sensor horizontally, with the sensor plane parallel to the XY plane.

[0091] S52. Keep the A-axis at position 0, move the C-axis to position 0, and move the translation axis so that the light spot falls near the center of the position sensor. Record the center position of the light spot read by the sensor at this moment.

[0092] S53. Move the C-axis to the 180° position and record the center position of the light spot read by the sensor at this moment, such as... Figure 8 As shown.

[0093] S54. Calculate the deviation ΔL4 between the two spot center positions in the Y direction, and the deviation of the C-axis-major axis rotation center line in the Y direction. It can be calculated using the following equation:

[0094] .

[0095] S55, will The value is written into the corresponding compensation parameter in the CNC system. Taking the Siemens 840D series CNC system as an example, the value is directly filled into the 24560[1] parameter, which completes the compensation of the deviation of the C-axis-spindle rotation center line in the Y direction.

[0096] S6. Measure and compensate for the deviation of the C-axis-spindle rotation center line in the X direction.

[0097] The deviation of the C-axis - spindle rotation center line in the X direction is as follows: Figure 9 As shown, step S6 includes the following sub-steps:

[0098] S61. Keep the light spot position sensor horizontal, with the sensor plane parallel to the XY plane.

[0099] S62. Keep the A-axis at position 0, move the C-axis to position 90°, and move the translation axis so that the light spot falls near the center of the position sensor. Record the center position of the light spot read by the sensor at this moment.

[0100] S63. Move the C-axis to the 270° position and record the center position of the light spot read by the sensor at this moment, such as... Figure 10 As shown.

[0101] S64. Calculate the deviation ΔL5 between the two spot center positions in the X direction, and the deviation of the C-axis-main axis rotation center line in the X direction. It can be calculated using the following equation:

[0102] .

[0103] S65, will The value is written into the corresponding compensation parameter in the CNC system. Taking the Siemens 840D series CNC system as an example, the value is directly filled into the 24560[0] parameter, which completes the compensation of the deviation of the C-axis-spindle rotation center line in the X direction.

[0104] Those skilled in the art will recognize that the embodiments described herein are intended to help the reader understand the principles of the invention, and should be understood that the scope of protection of the invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific modifications and combinations based on the technical teachings disclosed in this invention without departing from the spirit of the invention, and these modifications and combinations are still within the scope of protection of this invention.

Claims

1. A method for measuring and compensating for the zero-position error and axis error of a rotary axis of a CA-type five-axis machine tool based on the relative position measurement of a laser spot, characterized in that, Includes the following steps: S1. Detection system preparation: Clamp or fix the laser pointer to the spindle, ensuring that the laser beam path and the spindle rotation center are on the same straight line, and place the spot position sensor on the worktable; S2. Measurement and compensation for A-axis zero position error: A-axis zero position error is defined as the angular deviation between the actual posture of the machine tool execution end and the theoretical ideal posture when the rotary axis is set to 0° reference position. S3. Measurement and compensation for C-axis zero position error: C-axis zero position error is defined as the angular deviation between the actual posture of the machine tool execution end and the theoretical ideal posture when the rotary axis is set to 0° reference position. S4. Measure and compensate for the deviation of the A-axis-spindle rotation center line in the Y direction; S5. Measure and compensate for the deviation of the C-axis-spindle rotation center line in the Y direction; S6. Measure and compensate for the deviation of the C-axis-spindle rotation center line in the X direction.

2. The method for measuring and compensating for the zero-position error and axis error of a CA-type five-axis machine tool based on the relative position measurement of a laser spot, as described in claim 1, is characterized in that... S2 includes the following steps: S21. Place the light spot position sensor horizontally, with the sensor plane parallel to the XY plane; S22. Keep both the A-axis and C-axis at the 0 position, and move the translation axis so that the light spot falls near the center of the position sensor, and the end of the laser pointer is 30-50mm away from the sensor. Record the center position of the light spot read by the sensor at this moment. S23. Move the Z-axis down a distance Δz and record the center position of the light spot read by the sensor at this moment; S24. Calculate the deviation ΔL1 of the center position of the two light spots in the Y direction, and the zero-position error of the A-axis. It can be calculated using the following equation: ； S25. Compensate for the zero-position accuracy of the A-axis: Move the A-axis. The compensation can be completed by resetting the zero position of the coordinate system.

3. The method for measuring and compensating for the zero-position error and axis error of a CA-type five-axis machine tool based on the relative position measurement of a laser spot, as described in claim 1, is characterized in that... S3 includes the following steps: S31. Place the spot position sensor vertically, with the sensor plane parallel to the XZ plane; S32. Move axis A to 90°, keep axis C at 0, and move the translation axis so that the light spot falls near the center of the position sensor, and the end of the laser pointer is 30-50mm away from the sensor. Record the center position of the light spot read by the sensor at this moment. S33. Move the Y-axis to the right by a distance Δy, and record the center position of the light spot read by the sensor at this moment; S34. Calculate the deviation ΔL2 of the center position of the two light spots in the Y direction, and the zero-position error of the C-axis. It can be calculated using the following equation: ； S35. Compensate for C-axis zero-position accuracy: Move the C-axis. The compensation can be completed by resetting the zero position of the coordinate system.

4. The method for measuring and compensating for the zero-position error and axis error of a CA-type five-axis machine tool based on the relative position measurement of a laser spot, as described in claim 1, is characterized in that... S4 further includes the following sub-steps: S41. Place the spot position sensor vertically, with the sensor plane parallel to the XZ plane; S42. Keep the C-axis at the 0 position, move the A-axis to the -90° position, and move the translation axis to make the light spot fall near the center of the position sensor. Record the center position of the light spot read by the sensor at this moment. S43. Rotate the spot sensor 180° around the Z direction in place, move the A axis to the 90° position, move the translation axis to move the machine tool spindle to the other side of the sensor, and ensure that the Z axis position is the same as in step S22. Record the center position of the spot read by the sensor at this moment. S44. Calculate the deviation ΔL3 of the center position of the two light spots in the vertical direction (Z direction), and the deviation of the A-axis-major axis rotation center line in the Y direction. It can be calculated using the following equation: ； S45, will The numerical value is written into the corresponding compensation parameter in the CNC system, which can complete the compensation for the deviation of the A-axis-spindle rotation center line in the Y direction.

5. The method for measuring and compensating for the zero-position error and axis error of a CA-type five-axis machine tool based on the relative position measurement of a laser spot, as described in claim 1, is characterized in that... S5 includes the following steps: S51. Place the light spot position sensor horizontally, with the sensor plane parallel to the XY plane; S52. Keep the A-axis at position 0, move the C-axis to position 0, and move the translation axis so that the light spot falls near the center of the position sensor. Record the center position of the light spot read by the sensor at this moment. S53. Move the C-axis to the 180° position and record the center position of the light spot read by the sensor at this moment; S54. Calculate the deviation ΔL4 between the two spot center positions in the Y direction, and the deviation of the C-axis-major axis rotation center line in the Y direction. It can be calculated using the following equation: ； S55, will The value is written into the corresponding compensation parameter in the CNC system, which completes the compensation for the deviation of the C-axis-spindle rotation center line in the Y direction.

6. The method for measuring and compensating for the zero-position error and axis error of a CA-type five-axis machine tool based on the relative position measurement of a laser spot, as described in claim 1, is characterized in that... S6 includes the following sub-steps: S61. Keep the light spot position sensor horizontally positioned, with the sensor plane parallel to the XY plane; S62. Keep the A-axis at the 0 position, move the C-axis to the 90° position, and move the translation axis to make the light spot fall near the center of the position sensor. Record the center position of the light spot read by the sensor at this moment. S63. Move the C-axis to the 270° position and record the center position of the light spot read by the sensor at this moment; S64. Calculate the deviation ΔL5 between the two spot center positions in the X direction, and the deviation of the C-axis-main axis rotation center line in the X direction. It can be calculated using the following equation: ； S65, will The numerical value is written into the corresponding compensation parameter in the CNC system, which completes the compensation for the deviation of the C-axis-spindle rotation center line in the X direction.

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