Probe installation error compensation method for composite grinding center workpiece coordinate system calibration and application

Abstract

The application belongs to the technical field of grinding, and particularly discloses a probe installation error compensation method for workpiece coordinate system calibration of a composite grinding center and application, which comprises the following steps: S1: collecting calibration data of probe installation error, wherein the calibration data comprises machine tool coordinate values when the probe contacts a standard part; S2: calibrating the probe installation error by using the calibration data collected in S1 to obtain the probe installation error; and S3: compensating machine tool coordinate values used for workpiece coordinate system calibration based on the probe installation error obtained in S2. The method provided by the application has high compensation precision, can effectively improve the calibration precision of the workpiece coordinate system of the composite grinding center, and meets the demand of the high-precision composite grinding center for grinding size precision.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of grinding, and particularly relates to a probe installation error compensation method for workpiece coordinate system calibration of a composite grinding center and application thereof. BACKGROUND

[0002] The composite grinding center is a composite machine tool meeting the precise and efficient machining requirements of rotary body parts, has the automatic exchange capability of grinding tools, can realize the composite application of various grinding technologies, and completes the precise and efficient machining of various features of the parts in one clamping and positioning, including the grinding machining of features such as the external cylindrical surface, the internal cylindrical surface, the end surface, the external conical surface and the internal conical surface.

[0003] When the external conical surface and the internal conical surface are ground, the grinding wheel is dressed at the reference position, then is rotated by a corresponding angle, the surface of the grinding wheel is parallel to the surface of the conical surface, and then the grinding machining is performed. In order to ensure the accuracy of the workpiece coordinate system calibration, especially the precision of the workpiece coordinate system transformation after the rotation, the position relationship between the grinding reference point and the rotation center of the turret grinding wheel frame needs to be calibrated.

[0004] In the conventional calibration process of the position relationship between the grinding reference point and the rotation center of the turret grinding wheel frame, the relative position relationship between the probe reference point and the rotation center of the turret grinding wheel frame needs to be determined first, then the position relationship between the grinding reference point and the rotation center of the turret grinding wheel frame is indirectly calculated by contacting the same position of the workpiece through the probe reference point and the grinding reference point. In this process, the probe installation error directly affects the calculation result, and is of great significance to the machining precision of the size of the workpiece.

[0005] Patent CN107953216A discloses a workpiece coordinate system transformation method of a turret composite grinding machine, and the specific steps are as follows: (1) determining the relative position relationship between the probe reference position and the rotation center of the turret grinding wheel frame; (2) indirectly determining the relative position relationship between the reference point reference position of the external cylindrical grinding wheel or the end surface external cylindrical grinding wheel and the rotation center of the turret grinding wheel frame by using the relative position relationship between the grinding wheel reference point and the probe; (3) indirectly determining the relative position relationship between the reference point reference position of the internal cylindrical grinding wheel and the rotation center of the turret grinding wheel frame by using the relative relationship between the reference point reference position of the internal cylindrical grinding wheel and the reference point reference position of the external cylindrical grinding wheel or the end surface external cylindrical grinding wheel; and (4) obtaining the workpiece coordinate system transformation value when any grinding wheel is rotated by a specified angle from the reference angle. The patent ignores the installation error of components such as the probe and the grinding wheel in the workpiece coordinate system calibration process, so that the calibration result of the workpiece coordinate system is affected by the machine tool assembly error, and the precision cannot be guaranteed.

[0006] The mounting error of the conventional probe can meet the demand of the workpiece coordinate system calibration accuracy of the high-precision composite grinding center in the Z direction, but cannot meet the demand in the X direction. The method provided by the application can effectively improve the workpiece coordinate system calibration accuracy of the composite grinding center and meet the actual machining demand. SUMMARY

[0007] In view of the problems and deficiencies in the prior art, the application aims to provide a probe mounting error compensation method for workpiece coordinate system calibration of a composite grinding center.

[0008] To achieve the application purpose, the application adopts the following technical scheme:

[0009] The application provides a probe mounting error compensation method for workpiece coordinate system calibration of a composite grinding center, comprising the following steps:

[0010] S1: collecting calibration data of the probe mounting error, wherein the calibration data comprises machine tool coordinate values when the probe contacts a standard part;

[0011] S2: calibrating the probe mounting error by using the calibration data collected in S1 to obtain the probe mounting error;

[0012] S3: compensating machine tool coordinate values used for workpiece coordinate system calibration based on the probe mounting error obtained in S2.

[0013] According to the probe mounting error compensation method for workpiece coordinate system calibration of a composite grinding center, further, the specific process of step S1 is as follows:

[0014] S101: setting the ball center of the probe as a probe reference point, setting a plane parallel to the XZ plane of the machine tool coordinate system and passing through the axis center of the standard part as P, and setting the distance from the probe reference point to the plane P as the mounting error of the probe;

[0015] S102: mounting the standard part on the center of the headstock and tailstock of the machine tool, adjusting the posture of the standard part, and making the axis center of the standard part coincide with the rotation center of the headstock of the machine tool;

[0016] S103: rotating the rotation shaft of the turret type grinding wheel frame to make the probe at a reference angle position, and making the probe contact the cylindrical surface A and the cylindrical surface B of the standard part respectively, and recording the machine tool coordinate values when the signals are triggered, and recording them as (X A1 ,Z A1 ) and (X B1 ,Z B1 ) respectively.

[0017] According to the probe mounting error compensation method for workpiece coordinate system calibration of a composite grinding center, further, the specific process of step S2 is as follows:

[0018] S201: Let the diameter of the cylindrical surface A of the standard part be D. A The diameter of cylindrical surface B is D. B The probe tip diameter is D T Let E be the straight line passing through the probe reference point and perpendicular to the axis of the standard part. Then, when the probe contacts the cylindrical surface B of the standard part, the angle α between the straight line E and the plane P is:

[0019]

[0020] S202: Using the angle α between line E and plane P, the distance from the probe reference point to plane P is obtained, i.e., the probe installation error σ is:

[0021]

[0022] Based on the probe installation error compensation method calibrated by the workpiece coordinate system of the composite grinding center, the specific process of step S3 is as follows:

[0023] S301: Select the sample to be processed, install the sample on the center between the headstock and tailstock of the machine tool, and adjust the posture of the sample so that the axis of the sample coincides with the rotation center of the headstock of the machine tool.

[0024] S302: The rotary turret grinding wheel head's rotation axis positions the probe at a reference angle, bringing the probe into contact with the cylindrical surface C of the sample. The machine tool coordinates at the signal trigger point are recorded, denoted as (X...). C1 Z C1 );

[0025] S303: Measure the diameter of the cylindrical surface C of the sample, denoted as D. C ;

[0026] S304: The machine tool coordinate value of the cylindrical surface C of the sample contacted by the probe is denoted as (X). C2 Z C2 Based on the installation error σ of the probe, then:

[0027]

[0028] Z C2 =Z C1 .

[0029] According to the probe installation error compensation method for the workpiece coordinate system calibration of the composite grinding center, in step S1, the standard part has a stepped shaft structure for measuring the reference part standard, including two high-precision cylindrical surfaces A and B. The probe can contact the two cylindrical surfaces to transmit signals. The center lines of cylindrical surfaces A and B coincide with the axis of the standard part, and the diameter of cylindrical surface A is smaller than the diameter of cylindrical surface B.

[0030] The second aspect of the present application also provides an application of the probe installation error compensation method in the first aspect in composite grinding center workpiece coordinate system calibration.

[0031] Compared with the prior art, the present application has the following beneficial effects:

[0032] 1. The probe installation error compensation method for composite grinding center workpiece coordinate system calibration provided by the present application has clear implementation ideas, and the probe installation error required to be determined in the method is mainly calculated through machine tool motion coordinate values and size measurement values, so that the acquisition approach is convenient and can be realized by machine tool operators.

[0033] 2. The probe installation error compensation method for composite grinding center workpiece coordinate system calibration provided by the present application has high compensation precision, can effectively improve the calibration precision of the composite grinding center workpiece coordinate system, and meets the demand of high-precision composite grinding center workpieces for grinding size precision. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 is a schematic view of the composite grinding center of the present application, wherein 1 is an outer circle grinding wheel, 2 is an end face outer circle grinding wheel, 3 is a turret type grinding wheel frame, 4 is an inner circle grinding wheel, 5 is a probe, 6 is a workbench, 7 is a head frame, 8 is a standard part, 9 is a tail frame;

[0035] Figure 2 is a schematic view of a standard part used for collecting calibration data of the probe installation error of the present application;

[0036] Figure 3 is a geometric relationship diagram for calibrating the probe installation error of the present application;

[0037] Figure 4 is a schematic view of the position relationship of the probe contacting the standard part when collecting calibration data of the probe installation error of the present application, wherein (a) is the probe adhering to the outer circle A of the standard part, and (b) is the probe adhering to the outer circle B of the standard part;

[0038] Figure 5 is a schematic view of the probe 5 contacting the sample part 10 in the present application;

[0039] Figure 6 is a schematic view of the position relationship for verifying the improvement effect of the workpiece coordinate system calibration precision of the present application. DETAILED DESCRIPTION

[0040] In order for those skilled in the art to more clearly understand the technical solutions of the present application, the technical solutions of the present application will be described in detail below with specific embodiments. It should be emphasized that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0041] The structural schematic view of the composite grinding center of the present application is as followsFigure 1 As shown, the turret grinding head 3 is directly driven by the rotary shaft, the outer cylindrical grinding wheel 1, the inner cylindrical grinding wheel 4, the end face outer cylindrical grinding wheel 2 and the probe 5 are arranged on the grinding head, the machine head 7 and the tailstock 9 are installed on the workbench 6, and the standard part 8 is installed on the center between the machine head 7 and the tailstock 9.

[0042] Embodiment 1

[0043] A probe installation error compensation method for improving the workpiece coordinate system calibration accuracy of a composite grinding center as shown in the figure, the method comprising the following steps: Figure 1

[0044] S1: Collecting calibration data of the probe installation error σ, the calibration data including the machine coordinate values when the probe contacts the standard part;

[0045] S101: Let the ball center of the probe 5 be the probe reference point T, the plane parallel to the XZ plane of the machine coordinate system and passing through the axis of the standard part 8 (see Figure 2 ) be P, and the distance from the probe reference point T to the plane P be the installation error σ (see Figure 3 ) of the probe 5;

[0046] S102: Installing the standard part 8 on the center between the machine head 7 and the tailstock 9, and adjusting the posture of the standard part 8 so that the axis of the standard part 8 coincides with the rotary center of the machine head 7;

[0047] S103: Rotating the rotary shaft of the turret grinding head 3 of the composite grinding center so that the probe 5 is at the reference angle position, and the probe 5 contacts the cylindrical surface A and the cylindrical surface B of the standard part 8 respectively, as shown in Figure 4 (a) and Figure 4 (b) respectively, and recording the machine coordinate values when the signals are triggered, which are denoted as (X A1 , Z A1 ) and (X B1 , Z B1 ) respectively.

[0048] S2: Calibrating the probe installation error using the data collected in S1 to obtain the probe installation error σ;

[0049] S201: Let the diameter of the cylindrical surface A of the standard part 8 be D A , the diameter of the cylindrical surface B be D B , the diameter of the probe 5 be D T , and the straight line passing through the probe 5 reference point T and perpendicular to the axis of the standard part 8 be E, then when the probe 5 contacts the cylindrical surface B of the standard part 8, the line-plane angle α between the straight line E and the plane P is as formula (1) (see Figure 3 ):

[0050] ​

[0051] S202: Determine the distance from the reference point T of the probe 5 to the plane P, i.e. the installation error σ of the probe 5, by using the linear plane angle α of the straight line E and the plane P, as shown in formula (2):

[0052]

[0053] S3: Compensate the machine tool coordinate values used for workpiece coordinate system calibration based on the obtained probe installation error σ, so as to improve the calibration accuracy of the workpiece coordinate system of the compound grinding center;

[0054] S301: Select a sample piece 10 to be machined, install the sample piece 10 on the center between the headstock 7 and the tailstock 9 of the machine tool, and adjust the posture of the sample piece 10 so that the axis of the sample piece 10 coincides with the rotation center of the headstock 7;

[0055] S302: Rotate the rotation shaft of the turret wheel head 3 so that the probe 5 is at a reference angle position, and contact the cylindrical surface C of the sample piece 10 (see Figure 5 ), record the machine tool coordinate values when the signal is triggered, denoted as (X C1 ,Z C1 );

[0056] S303: Measure the diameter of the cylindrical surface C of the sample piece 10 by using an outside diameter micrometer, denoted as D C ;

[0057] S304: Record the machine tool coordinate values when the probe 5 contacts the cylindrical surface C of the sample piece 10 as (X C2 ,Z C2 ), and based on the installation error σ of the probe, (X C2 ,Z C2 ) is shown in formula (3):

[0058]

[0059] Z C2 =Z C1 (3)。

[0060] Example 2

[0061] This embodiment mainly verifies the improvement effect of the probe installation error compensation method described in Example 1 on the workpiece coordinate system calibration accuracy.

[0062] Suppose the installation error σ of the probe 5 is 5 mm, the diameter D C of the cylindrical surface C of the sample piece 10 is 50 mm, and the probe tip diameter D T is 2 mm. Suppose the distance from the reference point T of the probe 5 to the rotation shaft of the turret wheel head 3 in the X direction of the machine tool coordinate system is d a= 600mm, the distance between the reference point of the outer circle grinding wheel and the rotary shaft of the turret grinding wheel frame 3 in the X direction of the machine tool coordinate system is d b = 500mm. The origin of the workpiece coordinate system is established on the cylindrical surface C of the sample 10, and the workpiece coordinate system is offset in the negative X direction relative to the machine tool coordinate system by d c = 300mm (see Figure 6 ).

[0063] The X direction machine tool coordinate value when the probe 5 contacts the cylindrical surface C of the sample 10 is X c :

[0064]

[0065] Suppose that before and after the probe installation error compensation, the X direction error when using the probe to calibrate the workpiece coordinate system is ε o and ε c , respectively:

[0066] ε o = |X c -D T -(d a -d b )*2+d c *2| = |-398.9706-2-200+300*2| ≈ 0.9706mm

[0067]

[0068] ε o ≈ 0.9706mm > ε c ≈ 0.0000mm

[0069] Since the workpiece coordinate system calibration error ε o before the probe installation error compensation is much larger than the workpiece coordinate system calibration error ε c after the compensation, it is proved that the method provided by the present application can effectively improve the workpiece coordinate system calibration accuracy of the compound grinding center.

[0070] The above embodiments are specific embodiments of the present application, but the embodiments of the present application are not limited by the above embodiments, and any other combinations, changes, modifications, substitutions, simplifications that do not exceed the design idea of the present application fall within the protection scope of the present application.

Claims

1. A method for compensating for probe installation errors in the calibration of the workpiece coordinate system of a composite grinding center, characterized in that, Includes the following steps: S1: Collect calibration data of probe installation error, the calibration data including machine tool coordinate values ​​when the probe contacts the standard part; S2: The probe installation error is calibrated using the calibration data collected in S1 to obtain the probe installation error; S3: Based on the probe installation error obtained from S2, compensate for the machine tool coordinate values ​​used for workpiece coordinate system calibration; The specific process of step S1 is as follows: S101: Let the center of the probe be the probe reference point, and let P be the plane that is parallel to the XZ plane of the machine tool coordinate system and passes through the axis of the standard part. The distance from the probe reference point to the plane P is the probe installation error. S102: Install the standard part on the center between the headstock and tailstock of the machine tool, and adjust the posture of the standard part so that the axis of the standard part coincides with the rotation center of the headstock of the machine tool. S103: The rotary turret grinding wheel head's rotation axis positions the probe at a reference angle. The probe contacts cylindrical surfaces A and B of the standard part respectively, recording the machine tool coordinate values ​​at the time of signal triggering, denoted as follows: and ; The specific process of step S2 is as follows: S201: Let the diameter of the cylindrical surface A of the standard part be D. A The diameter of cylindrical surface B is D. B The probe tip diameter is D T Let E be the straight line passing through the probe reference point and perpendicular to the axis of the standard part. Then, when the probe contacts the cylindrical surface B of the standard part, what is the angle between the straight line E and the plane P? for: S202: Utilizing the angle between line E and plane P The distance from the probe reference point to plane P is obtained, i.e., the probe installation error σ is: ； The specific process of step S3 is as follows: S301: Select the sample to be processed, install the sample on the center between the headstock and tailstock of the machine tool, and adjust the posture of the sample so that the axis of the sample coincides with the rotation center of the headstock of the machine tool. S302: The rotary turret grinding wheel head's rotation axis positions the probe at a reference angle, bringing the probe into contact with the cylindrical surface C of the sample. The machine tool coordinates at the signal trigger point are recorded, denoted as... ; S303: Measure the diameter of the cylindrical surface C of the sample, denoted as D. C ; S304: The compensated machine coordinate values ​​of the cylindrical surface C of the probe contacting the sample are denoted as... Based on the installation error σ of the probe, then: ； The standard component described in step S1 has a stepped shaft structure, including two high-precision cylindrical surfaces A and B. The probe can contact the two cylindrical surfaces to transmit signals. The center lines of cylindrical surfaces A and B coincide with the axis of the standard component, and the diameter of cylindrical surface A is smaller than the diameter of cylindrical surface B.

2. The application of the probe installation error compensation method for workpiece coordinate system calibration of the composite grinding center as described in claim 1 in the calibration of the workpiece coordinate system of the composite grinding center.

Images