Machine tool having eccentric pin measuring device measuring circularity on machine

Abstract

To provide an eccentric pin measuring device measuring circularity while supporting a workpiece sandwiched between a spindle center and a tailstock center.SOLUTION: A workpiece w having an eccentric pin w1 is ground by a grindstone 9 of a grinder. On a grindstone table 7, an eccentric pin measuring device supporting a measuring head 15 so as to be movable in a vertical y-axis direction orthogonal to an x-axis is mounted. A position control part rotates a main spindle, maintains a distance in an x-axis direction from a pin center in an initial state where the measuring head 15 is brought into contact with the eccentric pin w1, controls a position in a y-axis direction so that the measuring head 15 exists at a position in a y-axis direction the same as the pin center, and determines positioning data in the x-axis direction, positioning data in the y-axis direction, a measured value from the measuring head 15, and a rotation phase angle during rotation of the workpiece w while rotating the workpiece w over one circumference of the eccentric pin w1 and creates measurement shape data.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a machine tool for machining cylindrical parts with large eccentricity, such as crank pins, having an eccentric pin measuring device that measures the roundness of an eccentric cylinder while rotatably supporting a workpiece. [Background technology]

[0002] Generally, crankshafts have low torsional rigidity and the rigidity varies depending on the phase angle, so when the crankpin is ground, it tends to become elliptical and high-precision roundness cannot be obtained. Therefore, after grinding, the workpiece is removed and attached to another device that measures shape errors, and then the workpiece is attached to the machine tool again and finished based on the obtained error information.

[0003] However, workpieces such as eccentric pins and cams used in press machines are heavy, making this task difficult. In particular, when the workpiece is large, the transportation task itself is time-consuming, and there are cases where the workpiece cannot be installed on the measuring device due to its size and weight restrictions. In such cases, the worker must measure the diameter of the machined cylindrical part at fixed angles and roughly estimate the roundness.

[0004] As a machine tool that can measure the surface of a workpiece with an eccentric pin without removing the workpiece from the spindle during machining and perform machining with accuracy within the allowable error range, for example, Patent Document 1 discloses a technology in which a contact body and a linear scale are placed on the grindstone head and the linear scale is turned to bring the contact body in a pendulum-like manner to contact the eccentric pin. Patent Document 2 discloses a technology in which a first arm, a second upper arm, and a second lower arm are placed in succession on the grindstone head and a riding gauge of a three-point contact type measuring device is attached to the second lower arm to contact the eccentric pin. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2014-168837 A [Patent Document 2] JP 2007-206086 A Summary of the Invention [Problem to be solved by the invention]

[0006] In the technology shown in Patent Document 1, in which a contact body is advanced in a pendulum manner by rotating a linear scale, if the eccentricity of the eccentric pin is large, the contact body does not reach the eccentric pin. In addition, the technology in Patent Document 2 uses a horseback riding gauge, but the length of the upper arm of the second arm and the lower arm of the second arm are lengthened on the first arm, so that the center of the eccentric pin and the center of the perfect circle are considered to be the same. However, the horseback riding gauge method is not suitable for measuring roundness for shape correction because it measures based on the outer diameter, which results in large measurement errors in the case of an elliptical shape, and it is difficult to identify the phase angle required for roundness correction.

[0007] SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to provide an eccentric pin measuring device which measures the roundness of an eccentric pin while a workpiece is supported by being sandwiched between a spindle center and a tailstock center. [Means for solving the problem]

[0008] In order to achieve the above object, the present invention provides a spindle that supports a workpiece having an eccentric pin with a pin center at an eccentric position and rotates the workpiece; a tool table that supports a tool for machining the workpiece and moves the tool in an x-axis direction perpendicular to the spindle; a position control unit that creates machining data for machining the workpiece and controls the rotation of the spindle and the movement of the machining tool; an eccentric pin measurement device attached to the tool table and supporting the measurement head so as to be movable in a y-axis direction perpendicular to the x-axis, The position control unit rotates the spindle while maintaining the distance in the x-axis direction (y-axis direction) from the center of the pin when the measuring head is in the initial state in contact with the eccentric pin, and controls the positions in the x-axis direction and the y-axis direction so that the measuring head is at the same position in the y-axis direction (x-axis direction) as the pin center, and while the workpiece is rotating, obtains position data in the x-axis direction, position data in the y-axis direction, measurement values ​​from the measuring head, and the rotational phase angle at that time over one revolution of the eccentric pin to create measured shape data. Effect of the Invention

[0009] According to the present invention, by synchronously controlling three axes (x-axis, C-axis, y-axis) including the x-axis motor that moves the grinding wheel head, the y-axis motor provided in the eccentric pin measuring device that moves together with the grinding wheel head, and the main shaft (C-axis motor) in addition to these two axes, it is possible to measure the shape (roundness, outer diameter, eccentricity) of the eccentric pin using a measuring head mounted on the y-axis. This measurement can be performed while the workpiece is supported by being sandwiched between the main shaft center and the tailstock center. This eliminates the need to transport the workpiece to a measuring device separate from the grinding machine, and prevents errors from occurring when the workpiece is reattached to the grinding machine for correction processing. Furthermore, it is possible to automatically create and input shape correction data from the measurement results, which allows for rapid correction processing and prevents input errors in shape correction data. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram illustrating a grinding machine according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a side view of the eccentric pin measuring device. [Diagram 3] FIG. 2 is a control block diagram of the grinding machine. [Figure 4] FIG. 13 is a diagram showing a flow when a measurement start signal is output from the control program. [Diagram 5] FIG. 2 is a diagram showing an overall flow of processing in grinding. [Figure 6] FIG. 13 is a diagram for explaining another embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The following description will be given taking a grinding machine as an example of a machine tool to which the present invention is applied. [Example 1] First, the mechanical configuration of the grinding machine 100 will be described with reference to the drawings. In Fig. 1A, the grinding machine 100 is equipped with a machine table 1, a work table 2, a z-axis motor 3, a headstock 4, a C-axis motor 5, a tailstock 6, a grinding wheel head 7, an x-axis motor 8, a grinding wheel 9 as a processing tool, and a drive motor 10 for the grinding wheel. In the grinding machine 100, the left-right direction is the z-axis direction, and the front-back direction is the x-axis direction. The direction perpendicular to the x-axis direction and the z-axis direction is the y-axis direction.

[0012] The machine table 1 is mounted on the floor. A work table 2 is supported on the front side of the upper surface of the machine table 1 (lower in Fig. 1A) so as to be movable in the z-axis direction. The work table 2 is moved by driving a z-axis motor 3 attached to the machine table 1. A z-axis encoder 3a is attached to the z-axis motor 3. The headstock 4 is placed on the left side of Fig. 1A on the work table 2, and is equipped with a C-axis that can rotate around the central axis of the spindle 4a. The spindle 4a is rotated by driving a C-axis motor 5 attached to the headstock 4.

[0013] The tailstock 6 is placed on the right side of FIG. 1A on the work table 2 so as to face the headstock 4. The spindle center 4c and the tailstock center 6a clamp and support the workpiece w. The grindstone head 7 is provided at the rear (upper part of FIG. 1A) of the upper surface of the machine table 1. The grindstone head 7 is supported on an x-track 11 by an x-axis motor 8 attached to the machine table 1 so as to be movable in the x-axis direction. An x-axis encoder 8a is attached to the x-axis motor 8. A grindstone 9 is supported on the left side of the grindstone head 7 so as to be rotatable around a grindstone shaft 9a. Here, the rotation center c1 of the grindstone shaft 9a is parallel to the spindle center e1. The grindstone 9 is disk-shaped. The grindstone 9 is rotated by a drive motor 10 for the grindstone 9 via a belt.

[0014] An eccentric pin measuring device 12 is attached on the tool stage (wheel stage 7), and the wheel stage 7 and the eccentric pin measuring device 12 are moved together in the x-axis direction by an x-axis motor. In Fig. 1B, the eccentric pin measuring device 12 includes a pair of measuring heads 15, a y-track 13 that supports the pair of measuring heads 15 movably in the y-axis direction perpendicular to the x-axis, a y-axis motor 14, and a y-axis encoder 14a.

[0015] Each of the pair of measuring heads 15 is a displacement gauge, and detects the amount of displacement by rotating the eccentric pin w1. In this embodiment, the pair of measuring heads 15 face each other in the x-axis direction, and the distance between them is initially calibrated to the ideal eccentric pin dimensions using a master gauge or the like, and is set so as to sandwich the eccentric pin w1 while in contact with the eccentric pin w1. The position of the measuring head 15 is controlled so that the distance from the pin center e2 of the eccentric pin w1 in the x-axis direction is always constant and the y-axis direction is the same as the pin center e2 while the main shaft (C-axis) 4a is rotating, so that each of the measuring heads 15 contacts the eccentric pin w1 and measures the displacement (shape error from the ideal shape of the eccentric pin w1) at the rotation phase angle of the workpiece. The measuring heads 15 are arranged in a pair in order to shorten the moving distance in the y-axis direction by the y orbit 13. In other words, the amount of displacement during the 180-degree rotation of the eccentric pin w1 can be converted into a shape error (for one revolution) by measuring the amount of displacement with the pair of measuring heads 15. When using one measuring head on one side, the measuring head on one side is controlled so that it is located at the same position in the y-axis direction, away from the pin center e2 of the eccentric pin w1 in the x-axis direction by the radius of the eccentric pin w1, during one rotation of the main shaft (C-axis) 4a.

[0016] FIG. 2 is a diagram showing a method for measuring the shape of the eccentric pin w1. In the figure, the position of the spindle center e1 in the x-axis direction is used as the origin. The same applies below. When the rotation center c1 of the grinding wheel 9, the spindle center e1, and the pin center e2 of the eccentric pin w1 are on the same line, the position in the x-axis direction when the measuring head on the opposite side of the grinding wheel contacts the eccentric pin is -Rr (FIG. 2A). The position in the x-axis direction when the workpiece rotates by the rotation angle θ is -Rcosθ-r (FIG. 2B). When the workpiece rotates 180 degrees, it becomes Rr (FIG. 2C). The position in the x-axis direction when the measuring head on the grinding wheel side contacts the eccentric pin is -R+r (FIG. 2A). The position in the x-axis direction when the workpiece rotates by the rotation angle θ is -Rcosθ+r (FIG. 2B). When the workpiece rotates 180 degrees, it becomes R+r (FIG. 2C).

[0017] 3 is a diagram showing a control block configuration of the grinding machine 100. The grinding machine 100 is a computer numerically controlled device (CNC), and has a CPU 16 and a storage unit 17 as a position control unit 200.

[0018] The storage unit 17 stores ideal shape data, measured shape data, corrected shape data, data for corrective machining, and a control program 17a executed by the CPU 16. The ideal shape data is target shape data of the eccentric pin w1. The measured shape data is data for each rotation phase angle of the spindle (C-axis) 4a obtained by measuring the ground work surface, the corrected shape data is data obtained by comparing the ideal shape data with the measured shape data and taking into account a shape error, and the data for corrective machining is data for machining created from the corrected shape data.

[0019] In actual machining of an eccentric cylinder by synchronous control of the x-axis and C-axis, the machining point moves up and down along the outer peripheral surface of the grinding wheel 9 as the workpiece rotates, so machining is performed by a control program for machining that is created by taking into account this movement of the machining point. On the other hand, in the measurement method according to the present invention, the control program 17a uses synchronous control of three axes, the x-axis, C-axis, and y-axis, so that the diameter of the eccentric pin is always measured, so the shape error obtained from the measured shape data cannot be directly read as data for correction machining. For this reason, a procedure is required in which corrected shape data is created by adding the shape error obtained by comparing the ideal shape data with the measured shape data, and then corrected shape data is created from this.

[0020] By executing the control program 17a by the CPU 16, the position control unit 200 creates machining data based on, for example, ideal shape data, and controls the motor driving unit 18 by this machining data. At this time, in the first grinding process, the motor driving unit 18 is controlled by the machining data based on the ideal shape data. The position detection unit 19 feeds back the position data to the position control unit 200. The position control unit 200 also controls the position of the measuring head 15 by the x-axis motor 8 and the y-axis motor 14 using the motor driving unit 18.

[0021] The motor drive unit 18 is connected to the x-axis motor 8 and the x-axis encoder 8a, the z-axis motor 3 and the z-axis encoder 3a, the y-axis motor 14 and the y-axis encoder 14a, and the C-axis motor 5 and the C-axis encoder 5a. The motor drive unit 18 drives the z-axis motor 3, the C-axis motor 5, and the x-axis motor 8. When position control is being performed by machining data to grind the workpiece w in the control program 17a, the motor drive unit 18 controls the z-axis position of the work table 2, the rotation angle of the spindle (C-axis) 4a, and the relative position between the spindle (C-axis) 4a and the grinding wheel head 7. When measurement of the grinding result is being performed in the control program 17a, the motor drive unit 18 controls the C-axis motor 5, the x-axis motor 8, and the y-axis motor 14 so that the measuring head 15 maintains the x-axis distance from the pin center e2 in the initial state in which the measuring head 15 contacts the eccentric pin w1, and the measuring head 15 is located at the same y-axis position as the pin center e2. In the case of this embodiment having a pair of measuring heads 15, the pair of measuring heads 15 are controlled so as to sandwich the eccentric pin w1.

[0022] The position detector 19 detects the z-axis position of the work table 2 from the z-axis encoder 3a, detects the x-axis position of the grinding wheel head 7 from the x-axis encoder 8a, detects the rotation angle of the main spindle (C-axis) 4a from the C-axis encoder 5a, and detects the y-axis position of the measuring head 15 from the y-axis encoder 14a. This position data is sent to the control program 17a as measurement shape data.

[0023] FIG. 4 shows a flow when a measurement start signal is output from the control program 17a. The eccentric pin w1 is placed in contact with and sandwiched between a pair of measuring heads 15 of the eccentric pin measuring device 12 by the x-axis motor 8 and the y-axis motor 14. The main shaft (C-axis) 4a is moved to the origin position (in this example, the rotation phase angle at which the eccentric pin w1 is farthest from the grinding wheel 9 is set to 0). The measurement value of the measuring head 15 measured at that point in time, the position in the x-axis direction, the position in the y-axis direction, and the rotation phase angle of the main shaft (C-axis) 4a are associated with each other and stored in the memory unit 17 (s1).

[0024] While rotating the main shaft (C-axis) 4a, the position in the x-axis direction, the position in the y-axis direction, and the rotation phase angle of the main shaft (C-axis) 4a are controlled so as to always sandwich the pin center e2 of the eccentric pin w1. Each of the measuring heads 15 contacts the eccentric pin w1 and measures the eccentric pin w1 at the rotation phase angle of the workpiece (s2). It is determined whether the main shaft (C-axis) 4a has rotated 180 degrees, and step s2 is continued until it has rotated 180 degrees (s3). The displacement amount obtained by the pair of measuring heads 15 gives the displacement amount of one revolution of the eccentric pin w1.

[0025] The measured shape data includes the position in the x-axis direction, the position in the y-axis direction, the rotation phase angle of the main shaft (C-axis) 4a, and the measurement value of the measuring head 15. The control program 17a compares the measured shape data with the ideal shape data to obtain the shape error of the machined surface location corresponding to each rotation phase angle of the main shaft (C-axis) 4a, creates corrected shape data consisting of each rotation phase angle of the main shaft (C-axis) 4a and the corresponding shape error, and stores it in the memory unit 17.

[0026] The control program 17a creates corrective machining data for controlling the z-axis motor 3, the C-axis motor 5, and the x-axis motor 8 from the corrective shape data, and stores the data in the storage unit 17.

[0027] FIG. 5 is a diagram showing an overall flow of the grinding process. The workpiece w is held between a spindle center 4c of a spindle (C-axis) 4a and a tailstock center 6a of a tailstock 6, and is made rotatable around the spindle (C-axis) 4a on a grinding machine 100.

[0028] Workpiece shape data, data on machine conditions, and the like are input from the input unit 20 and stored in the storage unit 17 (s21). Data on machine conditions include the cutting depth k1 for the workpiece w and the diameter of the grinding wheel 9 (grinding wheel diameter).

[0029] In response to a processing start operation from the input unit 20, the control program 17a starts data processing required for the first grinding step. The first grinding step is a step of performing processing until the workpiece w has a finish dimension close to that defined by the ideal shape data (s22).

[0030] When the planned finishing dimension of the workpiece w is reached, the position control unit 200 interrupts the first grinding process. Then, the wheel head 7 is moved to the side (rear side) away from the workpiece w (s23). When the first grinding process is interrupted, the diameter of the outer circumferential surface of the eccentric pin w1 is larger by the necessary finishing allowance.

[0031] The control program 17a starts the measurement process. This process is the process described with reference to FIG. 4. When the measurement process is completed, the position control unit 200 reads the data for correction processing and executes the correction processing (s26). After this correction processing, a spark out is performed to check whether the processing error is within the allowable value, and if the processing error is not within the allowable value, correction processing is performed again, etc., as necessary.

[0032] We have already described the machining of a workpiece w having an eccentric pin w1 with a circular cross section as the grinding point, but even if the grinding point has other polygonal shapes other than a perfect circle, such as a distorted circle with a continuously changing curvature, a distorted circle with straight or curved parts that produce parts where the curvature is discontinuous, or a polygon such as a triangle or a rectangle, it is possible to measure them, create corrected shape data, and perform the corrective machining, as long as the shape of the surface to be machined is defined as ideal shape data.

[0033] According to the present embodiment described above, the measuring head 15 is brought into contact with the eccentric pin w1 in the horizontal direction. If the contact surface of the measuring head 15 is a surface having a length in the y-axis direction, the influence of positioning error by the y-axis motor 14 can be minimized. Therefore, the positioning control by the y-axis motor 14 can be lower in accuracy than the highly accurate positioning control provided to the C-axis motor 5 and x-axis motor 8 of the grinding machine 100, and the roundness and eccentricity for each phase angle of the eccentric pin w1 can be measured at low cost.

[0034] According to the embodiment described above, the x-axis motor 8 for moving the grinding wheel head 7, the y-axis motor 14 provided on the eccentric pin measuring device 12 that moves together with the grinding wheel head 7, and the C-axis motor 5 are synchronously controlled to obtain three axes (x-axis, C-axis, and y-axis), which are the x-axis motor 8 for moving the grinding wheel head 7, the y-axis motor 14 provided on the eccentric pin measuring device 12 that moves together with the grinding wheel head 7, and the C-axis motor 5. This allows the measurement of the roundness, outer diameter, and eccentricity of the eccentric pin by the measuring head 15 mounted on the y-axis. This makes it possible to measure the shape of the eccentric pin while the workpiece w is supported by being sandwiched between the spindle center 4c and the tailstock center 6a. This eliminates the need to transport the workpiece w to a measuring device separate from the grinding machine 100, and prevents errors from occurring when the workpiece w is reattached to the grinding machine 100 to perform correction processing. Furthermore, the process from creating and inputting shape correction data from the measurement results can be performed automatically, which allows for rapid correction processing and prevents input errors in the shape correction data.

[0035] In the above embodiment, a pair of measuring heads 15 are used, but since two measuring heads 15 are used, the space occupied by the eccentric pin measuring device 12 becomes large. Therefore, measurement may be performed using only one measuring head 15. In this case, in order to obtain shape data of the eccentric pin, it is necessary to rotate the workpiece w by 360 degrees and move the measuring head 15 by 2R in the y-axis direction, but the space occupied by the measuring head can be reduced. As with the previous example, it is possible to measure even if the eccentric pin has a polygonal shape.

[0036] [Example 2] Fig. 6 shows another embodiment 2. These embodiments are realized by partially modifying the eccentric pin measuring device 12 and partially modifying the control program 17a. The other configurations are the same as those of the first embodiment, so a description thereof will be omitted. Furthermore, since a laser sensor 15a is used, it is possible to perform measurements at a greater distance from the eccentric pin than in the case of the general displacement measuring device used in the first embodiment.

[0037] 6, in the first embodiment, the pair of measuring heads 15 are provided opposite each other in the x-axis direction and are sensors that perform measurement by contact, but in this embodiment, as shown in Fig. 6A, the pair of measuring heads 15 are laser sensors 15a provided opposite each other in the y-axis direction, and the position control unit 200 drives the x-axis motor 8 to sandwich the eccentric pin w1 between the light sources of the laser sensor 15a. The laser sensor 15a measures the outer diameter and roundness by irradiating a laser onto the upper and lower outer surfaces.

[0038] The motor drive unit 18 controls the C-axis motor 5, the x-axis motor 8, and the y-axis motor 14 so that the distance in the y-axis direction from the pin center e2 to the laser sensor 15a in the initial state is maintained and the laser sensor 15a is located at the same position in the x-axis direction as the pin center e2. When a pair of laser sensors 15a is provided, the pair of laser sensors 15a is controlled to sandwich the eccentric pin w1.

[0039] In this example, the y-axis motor and y-axis encoder used have higher accuracy than those in Example 1. On the other hand, since the measurement range of the laser sensor 15a is wide and measurement is possible even when it is away from the eccentric pin, it is not necessary to strictly align the centers of the upper and lower laser sensors 15a with the center of the pin w1 in the initial state.

[0040] The specifications of the laser sensor 15a are shown in Figure 6B. Two types of displacement sensors with different measurement ranges are shown. For example, with displacement sensor No. 1, if the sensor face is installed at a position 190 mm away from the center, it can measure the outer peripheral surface of an eccentric pin with a radius of 85 mm to 125 mm. Therefore, even if the eccentric pin diameter changes, there is no need to change the setup as long as it is within the allowable diameter difference range.

[0041] The linearity is 40 x 0.00015 = 0.006 mm in a measurement range of 40 mm, but the error is canceled if calibrated with a master gauge, so there is no problem in terms of accuracy. The positioning accuracy of the y-axis is expected to be about ±1 μm. Therefore, the output of the upper laser sensor and the lower laser sensor are processed to determine the outer diameter of the eccentric pin, and the roundness is evaluated based on this.

[0042] In Example 1, the position control unit 200 rotates the main axis (C axis) 4a and controls the positions in the x-axis direction and the y-axis direction so that the distance from the pin center e2 to the measurement head 15 in the x-axis direction when the measurement head 15 is in the initial state and the measurement head 15 is located at the same position in the y-axis direction as the pin center e2. That is, the distance is maintained at "0" in the y-axis direction. Meanwhile, in Example 2, the position control unit 200 rotates the main axis (C axis) 4a and controls the positions in the x-axis direction and the y-axis direction so that the distance from the pin center e2 to the measurement head 15 in the y-axis direction when the measurement head 15 is in the initial state and the measurement head 15 is located at the same position in the x-axis direction as the pin center e2. That is, the distance is maintained at "0" in the x-axis direction.

[0043] In this way, in all the embodiments, the positions of the measuring head 15 in the x-axis direction and the y-axis direction are controlled so that the distance from the pin center in the initial state and the same distance in the y-axis direction as the pin center in the initial state are maintained while the main shaft (C-axis) 4a is rotating. For example, if the measuring head 15 is in a position at an arbitrary angle with respect to the pin center e2 in the initial state in which the measuring head 15 is in contact with the eccentric pin w1, this can be generalized by maintaining the initial distance in the x-axis direction and the initial distance in the y-axis direction from the pin center even while the main shaft (C-axis) 4a is rotating. [Explanation of symbols]

[0044] 1 Machine stand 2 Work Table 3 Z-axis motor 3a z-axis encoder 4 Headstock 4a Main axis (C axis) 4c Spindle center 5 C-axis motor 5a C-axis encoder 6 Tailstock 6a Tailstock center 7. Grindstone Head 8 x-axis motor 8a x-axis encoder 9. Grindstone 9a Grindstone spindle 10 Drive motor 11x orbit 12 Eccentric pin measuring device 13 y orbit 14 y-axis motor 14a y-axis encoder 15 Measuring Head 15a Laser sensor 16 CPU 17 Memory section 17a Control Program 18 Motor drive unit 19 Position detection unit 20 Input section 100 Grinding Machine 200 Position control section c1 Rotation center e1 Spindle center e2 pin center k1 Cutting depth w work w1 Eccentric pin θ Rotation angle

Claims

1. a spindle that supports a workpiece having an eccentric pin with a pin center at an eccentric position and rotates the workpiece; a tool table that supports a tool for machining the workpiece and moves the tool in an x-axis direction perpendicular to the spindle; a position control unit that creates machining data for machining the workpiece and controls the rotation of the spindle and the movement of the machining tool; an eccentric pin measuring device attached to the tool table and supporting the measuring head so as to be movable in a y-axis direction perpendicular to the x-axis, the position control unit rotates the spindle and controls the position of the measuring head to a position where the distance in the x-axis direction from the pin center of the eccentric pin is always constant and the distance in the y-axis direction from the pin center is always constant while the spindle is rotating, and while the workpiece is rotating, obtains position data in the x-axis direction, position data in the y-axis direction, measurement values ​​from the measuring head, and rotational phase angles at that time over one revolution of the eccentric pin to create measured shape data.

2. 2. The machine tool according to claim 1, wherein the measuring head is a measuring head that makes contact with the eccentric pin to measure the eccentric pin, The machine tool, wherein the measuring head is a pair of measuring heads that measure the eccentric pin by sandwiching it therebetween.

3. 2. The machine tool according to claim 1, wherein the position control unit performs machining of the workpiece to a finish dimension close to that of the ideal shape data, Create measurement shape data that defines the workpiece together with the rotation angle of the workpiece; A machine tool characterized in that corrected shape data is created by taking into account the shape error obtained by comparing the ideal shape data with the measured shape data, and corrective machining data is created from the corrected shape data to perform correction machining.

4. 2. The machine tool of claim 1, A machine tool characterized in that the distance that the position control unit keeps constant while the spindle rotates is either the distance in the x-axis direction being "0" or the distance in the y-axis direction being "0."

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