A probe-based method for measuring geometric errors of CNC machine tool spindles

Abstract

The present invention discloses a probe-based method for measuring the geometric error of a CNC machine tool spindle, belonging to the technical field of CNC machining precision detection. The method is characterized in that it comprises the following steps: a. setting the center of a ceramic standard ball as the origin of a measurement coordinate system; b. calculating the spindle axial runout T1; c. calculating the spindle radial runout T2; d. automatically measuring the machine tool precision by invoking the machine tool's probe, and automatically compensating the spindle axial runout T1 and the spindle radial runout T2 in the CNC system based on the measurement results. The present invention can automatically calibrate and compensate for the spindle radial runout precision and the spindle axial runout precision of the machine tool spindle, reducing manual intervention in the measurement process, improving detection efficiency, and effectively avoiding product quality problems caused by reduced geometric precision of the machine tool spindle.

Description

Technical Field

[0001] The present invention relates to the technical field of numerical control machining precision detection, and in particular to a probe-based method for measuring the geometric error of a spindle of a numerical control machine tool. Background Art

[0002] As CNC machine tools become increasingly mature, they are widely used in various industries. AC-type five-axis CNC machine tools, characterized by flexibility, speed, and a wide machining range, are widely used to machine various complex structural parts. However, in actual production, the accuracy of CNC machine tools is affected by many factors, resulting in machine tool errors. These factors include geometric errors in the machine tool structure and components, thermal deformation errors, errors caused by cutting forces, errors caused by tool wear, control errors, and other errors such as those caused by chatter. Geometric and thermal errors account for 45%-65% of the total error, and for large CNC machine tools, the impact can reach 55%-80%. As a crucial component of the machine tool structure, the motion accuracy of the machine tool spindle is a key factor in determining machining quality and cutting efficiency. Therefore, reducing the impact of CNC machine tool spindle geometric errors and accurately and rapidly measuring the geometric accuracy of the machine tool spindle are key to improving machine tool accuracy.

[0003] Common faults of machine tool spindles include axial runout and radial runout. Radial runout is used to detect shaft deviation, and axial runout is the slight movement of the shaft along its axis during operation. These will affect the rotational accuracy of the machine tool spindle, and at the same time cause the spindle to produce uneven weight during one rotation, and even cause the spindle mechanism to heat up. Existing inspection and adjustment of spindle geometric error accuracy are usually carried out using tools such as inspection rods and micrometers. This process is prone to large measurement errors, low measurement efficiency, and poor monitoring timeliness, resulting in operators being unable to promptly detect equipment accuracy degradation and prone to product quality problems.

[0004] A Chinese patent document with publication number CN106990756 B and publication date March 5, 2019, discloses a method for online monitoring of the geometric accuracy of CNC machine tools. The method is characterized in that, in this method, strain gauges are first attached to the surface of the CNC machine tool bed; a wireless strain monitoring system is established to collect and remotely transmit strain data of each discrete measuring point; the discrete strain data is used as boundary conditions to solve stress equations that satisfy the biharmonic function, predict the strain field distribution on the surface of the machine tool base part, and obtain the deformation state of the machine tool base part by integration; and then the straightness of the machine tool base part is calculated by the end point connection method.

[0005] The patent document discloses an online monitoring method for the geometric accuracy of CNC machine tools. This method involves attaching strain gauges to the surface of the machine tool base and collecting strain field data at corresponding points through a data acquisition system. Although this method can detect the deterioration of machine tool accuracy to a certain extent, it is unable to separate errors in the measurement data and guide operators to compensate for machine tool accuracy, which can easily lead to product quality problems caused by the decline in the geometric accuracy of the machine tool spindle. Summary of the Invention

[0006] In order to overcome the defects of the above-mentioned prior art, the present invention provides a method for measuring the geometric error of a CNC machine tool spindle based on a probe. The present invention can automatically calibrate and compensate for the radial runout accuracy and axial runout accuracy of the machine tool spindle, reduce manual intervention in the measurement process, improve detection efficiency, and effectively avoid product quality problems caused by the decline in the geometric accuracy of the machine tool spindle.

[0007] The present invention is achieved through the following technical solutions:

[0008] A method for measuring the geometric error of a CNC machine tool spindle based on a probe, characterized by comprising the following steps:

[0009] a. Fix the ceramic standard ball on the machine tool workbench, call and activate the probe, move the probe to the ceramic standard ball, execute the ball center automatic measurement program, obtain the center of the ceramic standard ball, and set the center of the ceramic standard ball as the origin of the measurement coordinate system Q (X, Y, Z);

[0010] b. Lift the probe along the Z+ direction of the machine tool to 100 mm from the highest point of the ceramic standard ball in the Z direction. Move the probe downward along the Z- direction at a speed of 300 mm / min to touch the highest point of the ceramic standard ball in the Z direction. Record the Z coordinate value P1 of the probe. Then lift the probe upward to 100 mm from the highest point of the ceramic standard ball in the Z direction. Touch the highest point of the ceramic standard ball in the Z direction every time the spindle rotates 10°. Record the Z coordinate value of the probe at each spindle angle. Obtain 36 coordinate values ​​through cyclic measurement and calculate the spindle axial runout T1.

[0011] c. Move the probe to a position 100 mm from the highest point of the ceramic standard ball in the X direction. Touch the highest point of the ceramic standard ball in the X direction along the machine tool at a speed of 300 mm / min. Record the probe's X coordinate value M1. Then move the spindle to a position 100 mm from the highest point of the ceramic standard ball in the X direction. Touch the highest point of the ceramic standard ball in the X direction every time the spindle rotates 10°. Record the probe's X coordinate value at each spindle angle. Obtain 36 coordinate values ​​through cyclic measurement and calculate the spindle radial runout T2.

[0012] d. By calling the machine tool's probe, the machine tool's accuracy is automatically measured. Based on the measurement results, the spindle's axial runout T1 and spindle's radial runout T2 are automatically compensated to the CNC system.

[0013] In step a, calling and activating the probe means inputting a tool change command on the machine tool side, calling the probe in the tool magazine, and loading it onto the spindle of the machine tool.

[0014] In step b, the spindle axial movement T1 is calculated by formula 1;

[0015] T1=P max -P min Formula 1;

[0016] Among them, P max is the maximum value of the Z coordinate value of the probe, P min The maximum Z coordinate value of the probe.

[0017] The maximum value of the Z coordinate value of the probe is determined by formula 2;

[0018] P max =MAX(P1, P2, P 3… P 36 ) Formula 2.

[0019] The minimum Z coordinate value of the probe is determined by formula 3;

[0020] P min =MIN(P1, P2, P 3… P 36 ) Formula 3.

[0021] In step b, the spindle radial runout T2 is calculated by formula 4;

[0022] T2=L max -L min Formula 4;

[0023] Among them, L max is the maximum value of the X coordinate value of the probe, L min The minimum X coordinate value of the probe.

[0024] The maximum value of the X coordinate value of the probe is determined by formula 5;

[0025] L max =MAX(M1,M2,M 3… M 36 ) Formula 5.

[0026] The minimum value of the X coordinate value of the probe is determined by formula 6;

[0027] L min =MIN(M1, M2, M 3… M 36 ) Equation 6.

[0028] The beneficial effects of the present invention are mainly manifested in the following aspects:

[0029] 1. Compared with the existing technology, the present invention can automatically calibrate and compensate for the radial runout accuracy and axial runout accuracy of the machine tool spindle, reduce manual intervention in the measurement process, improve detection efficiency, and effectively avoid product quality problems caused by the decline in the geometric accuracy of the machine tool spindle.

[0030] 2. In the present invention, the precision measurement process is automatically executed by calling the measurement program, which replaces the traditional manual measurement, reduces the influence of human measurement errors, and improves the measurement efficiency.

[0031] 3. The present invention no longer requires measuring tools such as a check rod and a micrometer for precision measurement. Instead, it can be completed with the probe provided by the machine tool. Measurement can be conveniently performed at any time, greatly improving the measurement frequency.

[0032] 4. Compared with the early manual accuracy inspection method which is highly dependent on the operator's experience, the present invention automates the measurement process and only needs to start the measurement program to complete the accuracy measurement, making the measurement more efficient and convenient.

[0033] 5. The present invention uses the probe that comes with the machine tool for measurement. There is no need to install additional measuring instruments. Only the measurement program needs to be run to complete the automatic measurement of the relevant precision of the machine tool. No manual operation is required in the intermediate process, and the measurement result does not need to be separated by errors. The measurement result is directly the result of the measured precision item, which is easy to operate and convenient for large-scale promotion and application in production sites. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments:

[0035] Figure 1 It is a flowchart of the present invention. DETAILED DESCRIPTION

[0036] Example 1

[0037] See also Figure 1 A method for measuring the geometric error of a CNC machine tool spindle based on a probe comprises the following steps:

[0038] a. Fix the ceramic standard ball on the machine tool workbench, call and activate the probe, move the probe to the ceramic standard ball, execute the ball center automatic measurement program, obtain the center of the ceramic standard ball, and set the center of the ceramic standard ball as the origin of the measurement coordinate system Q (X, Y, Z);

[0039] b. Lift the probe along the Z+ direction of the machine tool to 100 mm from the highest point of the ceramic standard ball in the Z direction. Move the probe downward along the Z- direction at a speed of 300 mm / min to touch the highest point of the ceramic standard ball in the Z direction. Record the Z coordinate value P1 of the probe. Then lift the probe upward to 100 mm from the highest point of the ceramic standard ball in the Z direction. Touch the highest point of the ceramic standard ball in the Z direction every time the spindle rotates 10°. Record the Z coordinate value of the probe at each spindle angle. Obtain 36 coordinate values ​​through cyclic measurement and calculate the spindle axial runout T1.

[0040] c. Move the probe to a position 100 mm from the highest point of the ceramic standard ball in the X direction. Touch the highest point of the ceramic standard ball in the X direction along the machine tool at a speed of 300 mm / min. Record the probe's X coordinate value M1. Then move the spindle to a position 100 mm from the highest point of the ceramic standard ball in the X direction. Touch the highest point of the ceramic standard ball in the X direction every time the spindle rotates 10°. Record the probe's X coordinate value at each spindle angle. Obtain 36 coordinate values ​​through cyclic measurement and calculate the spindle radial runout T2.

[0041] d. By calling the machine tool's probe, the machine tool's accuracy is automatically measured. Based on the measurement results, the spindle's axial runout T1 and spindle's radial runout T2 are automatically compensated to the CNC system.

[0042] This embodiment is the most basic implementation method. Compared with the existing technology, it can complete the automatic calibration and compensation of the radial runout accuracy and axial runout accuracy of the machine tool spindle, reduce manual intervention in the measurement process, improve detection efficiency, and effectively avoid product quality problems caused by the decline in the geometric accuracy of the machine tool spindle.

[0043] Example 2

[0044] See also Figure 1 A method for measuring the geometric error of a CNC machine tool spindle based on a probe comprises the following steps:

[0045] a. Fix the ceramic standard ball on the machine tool workbench, call and activate the probe, move the probe to the ceramic standard ball, execute the ball center automatic measurement program, obtain the center of the ceramic standard ball, and set the center of the ceramic standard ball as the origin of the measurement coordinate system Q (X, Y, Z);

[0046] b. Lift the probe along the Z+ direction of the machine tool to 100 mm from the highest point of the ceramic standard ball in the Z direction. Move the probe downward along the Z- direction at a speed of 300 mm / min to touch the highest point of the ceramic standard ball in the Z direction. Record the Z coordinate value P1 of the probe. Then lift the probe upward to 100 mm from the highest point of the ceramic standard ball in the Z direction. Touch the highest point of the ceramic standard ball in the Z direction every time the spindle rotates 10°. Record the Z coordinate value of the probe at each spindle angle. Obtain 36 coordinate values ​​through cyclic measurement and calculate the spindle axial runout T1.

[0047] c. Move the probe to a position 100 mm from the highest point of the ceramic standard ball in the X direction. Touch the highest point of the ceramic standard ball in the X direction along the machine tool at a speed of 300 mm / min. Record the probe's X coordinate value M1. Then move the spindle to a position 100 mm from the highest point of the ceramic standard ball in the X direction. Touch the highest point of the ceramic standard ball in the X direction every time the spindle rotates 10°. Record the probe's X coordinate value at each spindle angle. Obtain 36 coordinate values ​​through cyclic measurement and calculate the spindle radial runout T2.

[0048] d. By calling the machine tool's probe, the machine tool's accuracy is automatically measured. Based on the measurement results, the spindle's axial runout T1 and spindle's radial runout T2 are automatically compensated to the CNC system.

[0049] In step a, calling and activating the probe means inputting a tool change command on the machine tool side, calling the probe in the tool magazine, and loading it onto the spindle of the machine tool.

[0050] This embodiment is a preferred implementation method. The precision measurement process is automatically executed by calling the measurement program, replacing traditional manual measurement, reducing the impact of human measurement errors, and improving measurement efficiency.

[0051] Example 3

[0052] See also Figure 1 A method for measuring the geometric error of a CNC machine tool spindle based on a probe comprises the following steps:

[0053] a. Fix the ceramic standard ball on the machine tool workbench, call and activate the probe, move the probe to the ceramic standard ball, execute the ball center automatic measurement program, obtain the center of the ceramic standard ball, and set the center of the ceramic standard ball as the origin of the measurement coordinate system Q (X, Y, Z);

[0054] b. Lift the probe along the Z+ direction of the machine tool to 100 mm from the highest point of the ceramic standard ball in the Z direction. Move the probe downward along the Z- direction at a speed of 300 mm / min to touch the highest point of the ceramic standard ball in the Z direction. Record the Z coordinate value P1 of the probe. Then lift the probe upward to 100 mm from the highest point of the ceramic standard ball in the Z direction. Touch the highest point of the ceramic standard ball in the Z direction every time the spindle rotates 10°. Record the Z coordinate value of the probe at each spindle angle. Obtain 36 coordinate values ​​through cyclic measurement and calculate the spindle axial runout T1.

[0055] c. Move the probe to a position 100 mm from the highest point of the ceramic standard ball in the X direction. Touch the highest point of the ceramic standard ball in the X direction along the machine tool at a speed of 300 mm / min. Record the probe's X coordinate value M1. Then move the spindle to a position 100 mm from the highest point of the ceramic standard ball in the X direction. Touch the highest point of the ceramic standard ball in the X direction every time the spindle rotates 10°. Record the probe's X coordinate value at each spindle angle. Obtain 36 coordinate values ​​through cyclic measurement and calculate the spindle radial runout T2.

[0056] d. By calling the machine tool's probe, the machine tool's accuracy is automatically measured. Based on the measurement results, the spindle's axial runout T1 and spindle's radial runout T2 are automatically compensated to the CNC system.

[0057] Preferably, in step a, calling and activating the probe means inputting a tool change command at the machine tool end, calling the probe in the tool magazine, and loading it onto the spindle of the machine tool.

[0058] In step b, the spindle axial movement T1 is calculated by formula 1;

[0059] T1=P max -P min Formula 1;

[0060] Among them, P max is the maximum value of the Z coordinate value of the probe, P min The maximum Z coordinate value of the probe.

[0061] The maximum value of the Z coordinate value of the probe is determined by formula 2;

[0062] P max =MAX(P1, P2, P 3… P 36 ) Formula 2.

[0063] The minimum Z coordinate value of the probe is determined by formula 3;

[0064] P min =MIN(P1, P2, P 3… P 36 ) Formula 3.

[0065] This embodiment is another preferred implementation method. Precision measurement no longer requires measuring tools such as a check rod and a micrometer. It can be completed with the probe provided by the machine tool. Measurement can be conveniently performed at any time, which greatly improves the measurement frequency.

[0066] Example 4

[0067] See also Figure 1 A method for measuring the geometric error of a CNC machine tool spindle based on a probe comprises the following steps:

[0068] a. Fix the ceramic standard ball on the machine tool workbench, call and activate the probe, move the probe to the ceramic standard ball, execute the ball center automatic measurement program, obtain the center of the ceramic standard ball, and set the center of the ceramic standard ball as the origin of the measurement coordinate system Q (X, Y, Z);

[0069] b. Lift the probe along the Z+ direction of the machine tool to 100 mm from the highest point of the ceramic standard ball in the Z direction. Move the probe downward along the Z- direction at a speed of 300 mm / min to touch the highest point of the ceramic standard ball in the Z direction. Record the Z coordinate value P1 of the probe. Then lift the probe upward to 100 mm from the highest point of the ceramic standard ball in the Z direction. Touch the highest point of the ceramic standard ball in the Z direction every time the spindle rotates 10°. Record the Z coordinate value of the probe at each spindle angle. Obtain 36 coordinate values ​​through cyclic measurement and calculate the spindle axial runout T1.

[0070] c. Move the probe to a position 100 mm from the highest point of the ceramic standard ball in the X direction. Touch the highest point of the ceramic standard ball in the X direction along the machine tool at a speed of 300 mm / min. Record the probe's X coordinate value M1. Then move the spindle to a position 100 mm from the highest point of the ceramic standard ball in the X direction. Touch the highest point of the ceramic standard ball in the X direction every time the spindle rotates 10°. Record the probe's X coordinate value at each spindle angle. Obtain 36 coordinate values ​​through cyclic measurement and calculate the spindle radial runout T2.

[0071] d. By calling the machine tool's probe, the machine tool's accuracy is automatically measured. Based on the measurement results, the spindle's axial runout T1 and spindle's radial runout T2 are automatically compensated to the CNC system.

[0072] In step a, calling and activating the probe means inputting a tool change command on the machine tool side, calling the probe in the tool magazine, and loading it onto the spindle of the machine tool.

[0073] In step b, the spindle axial movement T1 is calculated by formula 1;

[0074] T1=P max -P min Formula 1;

[0075] Among them, P max is the maximum value of the Z coordinate value of the probe, P min The maximum Z coordinate value of the probe.

[0076] The maximum value of the Z coordinate value of the probe is determined by formula 2;

[0077] P max =MAX(P1, P2, P 3… P 36 ) Formula 2.

[0078] The minimum Z coordinate value of the probe is determined by formula 3;

[0079] P min =MIN(P1, P2, P 3… P 36 ) Formula 3.

[0080] In step b, the spindle radial runout T2 is calculated by formula 4;

[0081] T2=L max -L min Formula 4;

[0082] Among them, L max is the maximum value of the X coordinate of the probe, L min The minimum X coordinate value of the probe.

[0083] The maximum value of the X coordinate value of the probe is determined by formula 5;

[0084] L max =MAX(M1,M2,M 3… M 36 ) Formula 5.

[0085] The minimum value of the X coordinate value of the probe is determined by formula 6;

[0086] L min =MIN(M1, M2, M 3… M 36 ) Equation 6.

[0087] This embodiment is the best implementation method. Compared with the early manual accuracy inspection method which is highly dependent on the operator's experience, by automating the measurement process, the accuracy measurement can be completed by just starting the measurement program, making the measurement more efficient and convenient.

[0088] The machine tool's built-in probe is used for measurement. There is no need to install additional measuring instruments. Just run the measurement program to complete the automatic measurement of the machine tool's related accuracy. No manual operation is required in the intermediate process, and the measurement results do not need to be separated by errors. The measurement results are directly the results of the measured accuracy items. The operation is convenient and it is easy to promote and apply on a large scale in the production site.

[0089] The principles of the present invention are as follows:

[0090] Common faults of machine tool spindles include axial runout and radial runout. Spindle radial runout is used to detect shaft deviation, and spindle axial runout is a small movement of the shaft along the axis during operation. Both will affect the rotation accuracy of the machine tool spindle, and at the same time cause the spindle to produce uneven weight during one rotation, and even cause the spindle mechanism to heat up. Existing inspection and adjustment of spindle geometric error accuracy are usually carried out with tools such as inspection rods and micrometers. This process is prone to large measurement errors, low measurement efficiency, and poor monitoring timeliness, resulting in operators being unable to promptly detect equipment accuracy degradation and prone to product quality problems.

[0091] Before measurement, the present invention fixes an 18mm diameter ceramic standard ball on the machine tool workbench, calls up and activates the probe, moves the probe to the ceramic standard ball, executes the automatic sphere center measurement program, obtains the sphere center, and sets the sphere center as the origin of the measurement coordinate system. Then, the automatic measurement program for the axial runout accuracy of the machine tool spindle and the automatic measurement program for the radial runout accuracy of the machine tool spindle are executed. After the measurement is completed, the measured accuracy value is compensated to the corresponding accuracy parameter to verify whether the machine tool accuracy is qualified, thus completing the entire machine tool accuracy work. This reduces manual intervention in the measurement process and improves detection efficiency.

Claims

1. A method for measuring the geometric error of a CNC machine tool spindle based on a probe, characterized in that: The following steps are involved: a. Fix the ceramic standard ball on the machine tool workbench, call and activate the probe, move the probe to the ceramic standard ball, execute the ball center automatic measurement program, obtain the center of the ceramic standard ball, and set the center of the ceramic standard ball as the origin of the measurement coordinate system Q (X, Y, Z); b. Lift the probe along the Z+ direction of the machine tool to 100 mm from the highest point of the ceramic standard ball in the Z direction. Move the probe downward along the Z- direction at a speed of 300 mm / min to touch the highest point of the ceramic standard ball in the Z direction. Record the Z coordinate value P1 of the probe. Then lift the probe upward to 100 mm from the highest point of the ceramic standard ball in the Z direction. Touch the highest point of the ceramic standard ball in the Z direction every time the spindle rotates 10°. Record the Z coordinate value of the probe at each spindle angle. Obtain 36 coordinate values ​​through cyclic measurement and calculate the spindle axial runout T1. c. Move the probe to a position 100 mm from the highest point of the ceramic standard ball in the X direction. Touch the highest point of the ceramic standard ball in the X direction along the machine tool at a speed of 300 mm / min. Record the probe's X coordinate value M1. Then move the spindle to a position 100 mm from the highest point of the ceramic standard ball in the X direction. Touch the highest point of the ceramic standard ball in the X direction every time the spindle rotates 10°. Record the probe's X coordinate value at each spindle angle. Obtain 36 coordinate values ​​through cyclic measurement and calculate the spindle radial runout T2. d. By calling the machine tool's probe, the machine tool's accuracy is automatically measured. Based on the measurement results, the spindle's axial runout T1 and spindle's radial runout T2 are automatically compensated to the CNC system.

2. The method for measuring the geometric error of a CNC machine tool spindle based on a probe according to claim 1, characterized in that: In step a, calling and activating the probe means inputting a tool change command on the machine tool side, calling the probe in the tool magazine, and loading it onto the spindle of the machine tool.

3. The method for measuring geometric errors of a CNC machine tool spindle based on a probe according to claim 1, characterized in that: In step b, the spindle axial movement T1 is calculated by formula 1; T1=P max -P min Formula 1; Among them, P max is the maximum value of the Z coordinate value of the probe, P min The maximum Z coordinate value of the probe.

4. The method for measuring the geometric error of a CNC machine tool spindle based on a probe according to claim 3, characterized in that: The maximum value of the Z coordinate value of the probe is determined by formula 2; P max =MAX(P1,P2,P 3… P 36 ) Formula 2.

5. The method for measuring geometric errors of a CNC machine tool spindle based on a probe according to claim 3, characterized in that: The minimum Z coordinate value of the probe is determined by formula 3; P min =MIN(P1, P2, P 3… P 36 ) Formula 3.

6. The method for measuring geometric errors of a CNC machine tool spindle based on a probe according to claim 1, characterized in that: In step b, the spindle radial runout T2 is calculated by formula 4; T2=L max -L min Formula 4; Among them, L max is the maximum value of the X coordinate of the probe, L min The minimum X coordinate value of the probe.

7. The probe-based method for measuring geometric errors of a CNC machine tool spindle according to claim 6, wherein: The maximum value of the X coordinate value of the probe is determined by formula 5; L max =MAX(M1,M2,M 3… M 36 ) Formula 5.

8. The probe-based method for measuring geometric errors of a CNC machine tool spindle according to claim 6, wherein: The minimum value of the X coordinate value of the probe is determined by formula 6; L min =MIN(M1, M2, M 3… M 36 ) Equation 6.

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