Machine tool, measurement method, and measurement program

Abstract

To provide a technology for accurately capturing the movement of a table over a wider range of rotation angles. [Solution] The machine tool includes a table driver that drives a table to rotate around a rotation axis, a spindle to which a touch probe can be attached, a spindle driver that feeds the spindle relative to the table, and a control unit. The control unit executes a drive process that drives the table to rotate within a predetermined angular range, a first measurement process that measures the position of a reference object at first and second reference positions when the table is driven to a first rotation angle, a second measurement process that measures the position of the reference object at the first to third reference positions when the table is driven to the second rotation angle, a third measurement process that measures the position of the reference object at the second and third reference positions when the table is driven to the third rotation angle, and an output process that outputs each position measured in the first to third measurement processes. The second rotation angle is an angle between the first and third rotation angles.

Description

Technical Field

[0001] The present disclosure relates to a machine tool, a measurement method, and a measurement program.

Background Art

[0002] Japanese Unexamined Patent Application Publication No. 2016-155185 (Patent Document 1) discloses "an error identification method capable of simultaneously identifying all of the center position errors of the rotary axes, the tilt errors of the rotary axes, and the straightness of the linear axis among the geometric errors of a five-axis control machine tool of a type having one rotary axis on each of the table side and the spindle head side with respect to the linear axis" (see the abstract).

[0003] The machine tool disclosed in Patent Document 1 measures the position of a target ball (reference object) fixed to the table with a touch probe mounted on the spindle head. At this time, the machine tool measures the position of one reference object while rotating the table. Then, the machine tool identifies the geometric error based on the difference between the measured value and the command value.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In order to more accurately identify the geometric error related to the turning axis of the table, it is preferable to arrange a plurality of reference objects on the table. At this time, if the interval between the reference objects on the table is long, the movement of the table can be captured more accurately, and the measurement accuracy of the geometric error is improved. However, in this case, depending on the turning angle of the table, the spindle may interfere with other members, and the machine tool can measure the posture of the table only within a narrow turning angle range.

[0006] On the one hand, when the distance between the reference objects on the table is short, interference between the main shaft and other members can be avoided, and the machine tool can measure the attitude of the table in a wider swing angle range. However, in this case, the machine tool cannot accurately measure the attitude of the table.

[0007] In view of the above points, in order to calculate the geometric error related to the swing axis of the table, a technique for accurately capturing the movement of the table in a wider swing angle range is desired.

Means for Solving the Problem

[0008] In an example of the present disclosure, a machine tool capable of measuring measured values used for error correction processing of a rotation axis of a table on which a workpiece can be placed is provided. The table is configured to be able to mount a reference object. The mounting positions of the reference object on the table belong to a first region on the table and do not belong to a second region on the table, one or more first reference positions, and belong to an overlapping region of the first region and the second region. One or more second reference positions, and one or more third reference positions belonging to the second region and not belonging to the first region. The machine tool further includes a table drive unit for rotationally driving the table about the rotation axis, a spindle on which a touch probe can be mounted, a spindle drive unit for relatively feeding and driving the spindle with respect to the table, and a control unit for controlling the machine tool. The control unit performs a drive process of rotationally driving the table within a predetermined angle range about the rotation axis, and when the table is driven to a first rotation angle within the predetermined angle range, the first reference position and the second reference position. A first measurement process of measuring the position of the reference object at the position with the touch probe, and when the table is driven to a second rotation angle within the predetermined angle range, the first reference position, the second reference position, and the third reference position. A second measurement process of measuring the position of the reference object at the position with the touch probe, and when the table is driven to a third rotation angle within the predetermined angle range, the second reference position and the third reference position. A third measurement process of measuring the position of the reference object at the position with the touch probe, and an output process of outputting each position measured in the first to third measurement processes as the measured value. The second rotation angle is an angle between the first rotation angle and the third rotation angle.

[0009] In an example of the present disclosure, the control unit further performs the error correction process based on the measured value. In the error correction process, the rotation center related to the rotation axis and the geometric error related to the rotation axis are calculated.

[0010] In an example of the present disclosure, the number of the first reference positions is two or more. The number of the third reference positions is two or more.

[0011] In an example of the present disclosure, the number of the second reference positions is two or more.

[0012] In an example of the present disclosure, when the distance from the touch probe to the first reference position in the axial direction of the main shaft is defined as a first distance, the distance from the touch probe to the second reference position in the axial direction of the main shaft is defined as a second distance, and the distance from the touch probe to the third reference position in the axial direction of the main shaft is defined as a third distance, when the table is at the first turning angle, the first distance is shorter than the second distance, and the second distance is shorter than the third distance. When the table is at the third turning angle, the third distance is shorter than the second distance, and the second distance is shorter than the first distance.

[0013] In another example of the present disclosure, a measurement method is provided for measuring actual measurement values used in error correction processing of a rotation axis of a table on which a workpiece can be placed with a machine tool. The table is configured to be able to mount a plurality of reference objects. Mounting positions of the reference objects on the table include one or more first reference positions that belong to a first region on the table and do not belong to a second region on the table, one or more second reference positions that belong to an overlapping region between the first region and the second region, and one or more third reference positions that belong to the second region and do not belong to the first region. The machine tool includes a table drive unit for rotationally driving the table about the rotation axis, a spindle on which a touch probe can be mounted, and a spindle drive unit for relatively feeding and driving the spindle with respect to the table. The measurement method includes a drive step of rotationally driving the table within a predetermined angular range about the rotation axis, a first measurement step of measuring positions of the reference objects at the first reference position and the second reference position with the touch probe when the table is driven to a first rotation angle within the predetermined angular range, a second measurement step of measuring positions of the reference objects at the first reference position, the second reference position, and the third reference position with the touch probe when the table is driven to a second rotation angle within the predetermined angular range, a third measurement step of measuring positions of the reference objects at the second reference position and the third reference position with the touch probe when the table is driven to a third rotation angle within the predetermined angular range, and an output step of outputting each position measured in the first to third measurement steps as the actual measurement value. The second rotation angle is an angle between the first rotation angle and the third rotation angle.

[0014] In another example of the present disclosure, a measurement program is provided for measuring actual measurement values used in error correction processing of the rotation axis of a table on which a workpiece can be placed with a machine tool. The table is configured to be able to mount a plurality of reference objects. The mounting positions of the reference objects on the table include one or more first reference positions that belong to a first region on the table and do not belong to a second region on the table, one or more second reference positions that belong to an overlapping region between the first region and the second region, and one or more third reference positions that belong to the second region and do not belong to the first region. The machine tool includes a table drive unit for rotationally driving the table about the rotation axis, a spindle to which a touch probe can be attached, and a spindle drive unit for relatively feeding and driving the spindle with respect to the table. The measurement program causes a computer to perform a drive process of rotationally driving the table within a predetermined angle range about the rotation axis, a first measurement process of measuring the positions of the reference objects at the first reference position and the second reference position with the touch probe when the table is driven to a first rotation angle within the predetermined angle range, a second measurement process of measuring the positions of the reference objects at the first reference position, the second reference position, and the third reference position with the touch probe when the table is driven to a second rotation angle within the predetermined angle range, a third measurement process of measuring the positions of the reference objects at the second reference position and the third reference position with the touch probe when the table is driven to a third rotation angle within the predetermined angle range, and an output process of outputting each position measured in the first to third measurement processes as the actual measurement value. The second rotation angle is an angle between the first rotation angle and the third rotation angle.

[0015] The above and other objects, features, aspects and advantages of the present invention will become apparent from the following detailed description of the present invention, which is to be understood in conjunction with the accompanying drawings.

Brief Description of the Drawings

[0016]

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Embodiments for Carrying Out the Invention

[0017] Hereinafter, each embodiment according to the present invention will be described with reference to the drawings. In the following description, the same parts and components are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed descriptions thereof will not be repeated. In addition, each embodiment and each modification described below may be selectively combined as appropriate.

[0018] <A. Appearance of Machine Tool 100> First, referring to FIG. 1, the machine tool 100 according to the embodiment will be described. FIG. 1 is a diagram showing an example of the appearance of the machine tool 100.

[0019] As used in this specification, the "machine tool" is a concept encompassing various devices having a function of machining a workpiece. The machine tool 100 may be a horizontal machining center, or may be a vertical machining center. Alternatively, the machine tool 100 may be a lathe, or other cutting machines, grinding machines, multi-tasking machines, 5-axis machining machines, etc. Further, the machine tool 100 is not limited to performing only removal machining, and may perform additional machining in addition to removal machining.

[0020] The machine tool 100 includes, for example, a cover body 130 and an operation panel 200.

[0021] The cover body 130 is a mechanism for protecting the components provided inside the machine tool 100. A door DR is provided on the cover body 130. The door DR is, for example, a slide-type door. The door DR may be configured to be openable and closable by a drive source such as a motor, or may be configured to be openable and closable manually.

[0022] The operation panel 200 is a general-purpose computer and has a display for displaying various information related to machining. The display is, for example, a liquid crystal display, an organic EL (Electro Luminescence) display, or other display devices. Further, the display is provided with a touch panel and accepts various operations on the machine tool 100 by touch operation.

[0023] <B. Device Configuration of Machine Tool 100> The machine tool 100 according to the embodiment is, for example, a 5-axis machining machine. A 5-axis machining machine is a machine capable of machining a workpiece by combining the drive of three axes in the linear direction, the drive related to the rotation axis, and the drive related to the tilt axis.

[0024] Hereinafter, with reference to FIG. 2, the device configuration of the machine tool 100 as a five-axis machine tool will be described. FIG. 2 is a diagram showing an example of a device configuration for realizing five-axis machining.

[0025] In the example of FIG. 2, the machine tool 100 includes a spindle head 140 and a table mechanism 150. The spindle head 140 includes a spindle 142 and a housing 143.

[0026] The spindle 142 is provided inside the housing 143. A tool TL for machining a workpiece W, which is the object to be machined, can be mounted on the spindle 142. In the example of FIG. 2, a tool TL for performing milling is mounted on the spindle 142.

[0027] Hereinafter, for convenience of explanation, a coordinate system with the spindle 142 as a reference is represented by the X-axis, Y-axis, and Z-axis. The Z-axis is an axis parallel to the axial direction of the spindle 142. The X-axis is an axis on a plane orthogonal to the Z-axis. The Y-axis is an axis orthogonal to both the X-axis and the Z-axis. In the example of FIG. 2, the Y-axis is shown as an axis parallel to the vertical direction.

[0028] Also, an axis that rotates about the X-axis as a rotation center is also referred to as the A-axis. An axis that rotates about the Y-axis as a rotation center is also referred to as the B-axis. An axis that rotates about the Z-axis as a rotation center is also referred to as the C-axis.

[0029] The spindle head 140 is configured to be movable relative to the workpiece W. As an example, the spindle head 140 is configured to be feed-driven in the X-axis direction and the Y-axis direction.

[0030] More specifically, inside the machine tool 100, a bed (not shown) serving as a base is provided. On the bed, a column (not shown) extending in the XY plane is provided. Further, a first saddle (not shown) is provided on the side surface of the column. The first saddle is configured to be drivable in the X-axis direction with respect to the column via a drive mechanism such as a ball screw and a servo motor. Further, a spindle head 140 is provided on the side surface of the first saddle. The spindle head 140 is configured to be drivable in the Y-axis direction with respect to the first saddle via a drive mechanism such as a ball screw and a servo motor. Thus, the spindle head 140 can be driven to any position in the X-axis direction and the Y-axis direction.

[0031] The table mechanism 150 includes drive mechanisms 152A and 152B, a swivel table 154, and a table 156.

[0032] The table mechanism 150 is configured to be feed drivable in the Z-axis direction. More specifically, a second saddle (not shown) is provided on the bed. The second saddle is configured to be feed drivable in the Z-axis direction via a drive mechanism such as a ball screw and a servo motor. Further, the table mechanism 150 is provided on the second saddle. Thus, the spindle head 140 can be driven to any position in the Z-axis direction.

[0033] Further, the table mechanism 150 is configured to be swivellable about a swivel axis AXA parallel to the X-axis. More specifically, the drive mechanisms 152A and 152B are fixed to the second saddle so as to face each other in the X-axis direction. A swivel table 154 is provided between the drive mechanisms 152A and 152B. Further, motors are provided inside the drive mechanisms 152A and 152B, respectively. Each motor is connected to the swivel table 154 and is synchronously controlled. Thus, the drive mechanisms 152A and 152B are configured to swivel-drive the swivel table 154 about the swivel axis AXA.

[0034] Note that various motors can be adopted for the drive mechanisms 152A and 152B. As an example, the motor may be a servo motor or a direct drive motor. The direct drive motor directly rotationally drives the turntable 154 without using a speed reduction mechanism. By using the direct drive motor, the driving force of the motor is directly transmitted to the turntable 154, improving the force transmission efficiency.

[0035] A table 156 for placing the workpiece W is provided on the turntable 154. The table 156 is configured to be rotatable about the rotation axis AXB. The rotation axis AXB is an axis orthogonal to the grounding surface of the workpiece W on the table 156 and is an axis that rotates together with the turntable 154. A motor is provided inside the turntable 154, and the table 156 is connected to the motor. The motor rotationally drives the table 156 about the rotation axis AXB.

[0036] <C. Measurement Process> The machine tool 100 controls the driving of the spindle 142 and the table 156 by outputting command values for each of the X-axis, Y-axis, Z-axis, A-axis, and B-axis according to a pre-designed machining program. Thereby, the machine tool 100 can machine the workpiece W into an arbitrary shape.

[0037] At this time, the actual positions of the spindle 142 and the table 156 may deviate from the positions recognized by the machine tool 100. The reasons for such geometric errors are various, such as the device configuration of the machine tool 100 and the shape of the workpiece. Therefore, some machine tools 100 are equipped with a function to correct such geometric errors. In the correction function, the internal parameters of the machine tool 100 are corrected so that the recognized position approaches the actual measurement position of the reference object.

[0038] In order to accurately identify the geometric error related to the rotation axis of the table 156, it is necessary to measure the position of the reference object at a plurality of reference positions. FIG. 3 is a diagram showing an example of the arrangement pattern of the reference object on the table 156.

[0039] In the example of FIG. 3, the reference object T is arranged at the reference positions PX1 to PX4 on the table 156. The reference object T is, for example, a steel ball. The reference object T may be manually arranged on the table 156 or automatically arranged on the table 156. Also, one reference object T may be sequentially arranged at the reference positions PX1 to PX4, or four reference objects T may be arranged at the reference positions PX1 to PX4.

[0040] The machine tool 100 rotates the table 156 at predetermined rotation angles and measures the position of the reference object T at each rotation angle at the reference positions PX1 to PX4. The position of the reference object T is measured by the touch probe TP. The touch probe TP is a contact type position measurement sensor.

[0041]

[0041] The touch probe TP is configured to be detachable from the spindle 142. The attachment and detachment of the touch probe TP to and from the spindle 142 are realized, for example, by an automatic tool changer (ATC). The machine tool 100 attaches the touch probe TP to the spindle 142 when performing the correction process of the geometric error.

[0042] As shown in the arrangement pattern (A) of FIG. 3, when the intervals between the reference positions PX1 to PX4 are long, the machine tool 100 can more accurately capture the movement of the table 156. As a result, the correction accuracy of the geometric error is improved. However, in this case, depending on the rotation angle of the table 156, the spindle 142 may interfere with other members.

[0043] FIG. 4 is a diagram showing an example in which the main shaft 142 interferes with the table 156. In state (B) of FIG. 4, compared with state (A) of FIG. 4, the table 156 has rotated 180° about the rotation axis AXA. In state (A) of FIG. 4, the machine tool 100 can measure the position of the reference object T at the reference position PX1 without causing the main shaft 142 to interfere with the table 156. On the other hand, in state (B) of FIG. 4, since the main shaft 142 interferes with the table 156, the machine tool 100 cannot measure the position of the reference object T at the reference position PX1. Therefore, in the arrangement pattern (A) of FIG. 3, the machine tool 100 can measure the posture of the table 156 only within a narrow rotation angle range.

[0044] On the other hand, as shown in the arrangement pattern (B) of FIG. 3, when the intervals between the reference positions PX1' to PX4' on the table 156 are short, the machine tool 100 can avoid interference between the main shaft 142 and other members. As a result, the machine tool 100 can measure the posture of the table 156 within a wider rotation angle range. However, when the intervals between the reference positions PX1' to PX4' are short, the machine tool 100 cannot accurately capture the movement of the table 156 at each rotation angle.

[0045] Therefore, in the machine tool 100 according to the embodiment, the position of the reference object T is measured at more reference positions than in the example of FIG. 3. FIG. 5 is a diagram showing another example of the arrangement pattern of the reference object on the table 156.

[0046] The mounting area of the reference object T on the table 156 includes a mounting area R1 (first area) and a mounting area R2 (second area). The mounting areas R1 and R2 are areas on the table 156. The mounting area R1 and the mounting area R2 overlap partially.

[0047] The mounting positions of the reference object T on the table 156 include reference positions P1, P2 (first reference positions) that belong to the mounting area R1 and do not belong to the mounting area R2, reference positions P3, P4 (second reference positions) that belong to the overlapping area of the mounting area R1 and the mounting area R2, and reference positions P5, P6 (third reference positions) that belong to the mounting area R2 and do not belong to the mounting area R1. The reference positions P1 to P6 on the table 156 are predetermined.

[0048] The machine tool 100 changes the reference positions P1 to P6 to be measured according to the turning angle of the table 156. Hereinafter, the measurement mode of the reference object T will be described.

[0049] Note that hereinafter, when the placement surface of the workpiece W on the table 156 is parallel to the horizontal plane and the workpiece W is located above the table 156, the turning angle of the table 156 is set to 0°. Also, when the placement surface of the workpiece W on the table 156 is parallel to the horizontal plane and the workpiece W is located below the table 156, the turning angle of the table 156 is set to -180°.

[0050] FIG. 6 is a diagram showing in tabular form the reference positions to be measured and the reference positions not to be measured according to the turning angle of the table 156. FIG. 7 is a diagram for explaining the measurement process when the reference object T is mounted at the reference positions P1, P2.

[0051] When measuring the position of the reference object T, the machine tool 100 drives the table 156 to turn within a predetermined angle range Δθ centered on the turning axis AXA.

[0052] More specifically, first, the operator mounts the reference object T at the reference position P1 within the mounting area R1. Thereafter, the machine tool 100 starts the turning process of the reference object T.

[0053] In step S1, assume that the turning angle of the table 156 reaches the turning angle θ1 (first turning angle). When the machine tool 100 is driven to the turning angle θ1 within a predetermined angle range Δθ of the table 156, the machine tool 100 measures the position of the reference object T in the mounting area R1 with the touch probe TP. That is, in step S1, the machine tool 100 does not measure the position of the reference object T that does not belong to the mounting area R1.

[0054] The turning angle θ1 is, for example, "0°" and "-30°". More specifically, the machine tool 100 first maintains the turning angle of the table 156 at "0°". Then, the machine tool 100 measures the position of the reference object T in the mounting area R1 with the touch probe TP. Next, the machine tool 100 maintains the turning angle of the table 156 at "-30°". Then, the machine tool 100 measures the position of the reference object T in the mounting area R1 with the touch probe TP.

[0055] Thus, when the turning angle of the table 156 is the turning angle θ1, the machine tool 100 measures the mounting area R1 that is closer to the spindle 142.

[0056] Next, in step S2, assume that the turning angle of the table 156 reaches the turning angle θ2 (second turning angle). The turning angle θ2 is an angle between the above-described turning angle θ1 and a turning angle θ3 described later. When the machine tool 100 is driven to the turning angle θ2 within a predetermined angle range Δθ of the table 156, the machine tool 100 measures the positions of the reference objects T in the mounting areas R1 and R2 with the touch probe TP. That is, in step S2, the machine tool 100 measures the entire area.

[0057] The turning angle θ2 is, for example, "-60°", "-90°", "-120°". As a more specific measurement process in step S2, the machine tool 100 first maintains the turning angle of the table 156 at "-60°". Then, the machine tool 100 measures the position of the reference object T with the touch probe TP. Next, the machine tool 100 maintains the turning angle of the table 156 at "-90°". Then, the machine tool 100 measures the position of the reference object T with the touch probe TP. Next, the machine tool 100 maintains the turning angle of the table 156 at "-120°". Then, the machine tool 100 measures the position of the reference object T with the touch probe TP.

[0058] In this way, when the turning angle of the table 156 is the turning angle θ2, the machine tool 100 measures the entire area of the mounting areas R1 and R2.

[0059] Next, in step S3, it is assumed that the turning angle of the table 156 has reached the turning angle θ3 (third turning angle). When the table 156 is driven to the turning angle θ3 within the predetermined angle range Δθ, the machine tool 100 measures the reference object T belonging to the mounting area R2. In the example of FIG. 7, since there is no reference object T belonging to the mounting area R2, the machine tool 100 does not measure the position of the reference object T in step S3.

[0060] Note that the turning drive of the table 156 between step S2 and step S3 may or may not be executed.

[0061] Based on the completion of the measurement processes in steps S1 to S3, the operator changes the mounting position of the reference object T from the reference position P1 to the reference position P2. Then, the machine tool 100 executes the measurement processes in steps S1 to S3 again.

[0062] Next, the operator changes the mounting position of the reference object T from the reference position P2 to the reference position P3. Thereafter, the machine tool 100 starts the measurement process shown in FIG. 8. FIG. 8 is a diagram for explaining the measurement process when the reference object T is mounted at the reference positions P3 and P4.

[0063] In step S4, it is assumed that the turning angle of the table 156 has reached the turning angle θ1 (first turning angle). When the machine tool 100 is driven to the turning angle θ1 within a predetermined angle range Δθ of the table 156, the machine tool 100 measures the position of the reference object T in the mounting area R1 with the touch probe TP. That is, in step S4, the machine tool 100 does not measure the position of the reference object T that does not belong to the mounting area R1.

[0064] The turning angle θ1 is, for example, "0°" and "-30°". More specifically, the machine tool 100 first maintains the turning angle of the table 156 at "0°". Then, the machine tool 100 measures the position of the reference object T in the mounting area R1 with the touch probe TP. Next, the machine tool 100 maintains the turning angle of the table 156 at "-30°". Then, the machine tool 100 measures the position of the reference object T in the mounting area R1 with the touch probe TP.

[0065] Next, in step S5, it is assumed that the turning angle of the table 156 has reached the turning angle θ2 (second turning angle). When the machine tool 100 is driven to the turning angle θ2 within a predetermined angle range Δθ of the table 156, the machine tool 100 measures the positions of the reference objects T in the mounting areas R1 and R2 with the touch probe TP. That is, in step S5, the machine tool 100 measures the entire area.

[0066] The turning angle θ2 is, for example, "-60°", "-90°", "-120°". As a more specific measurement process in step S5, the machine tool 100 first maintains the turning angle of the table 156 at "-60°". Then, the machine tool 100 measures the position of the reference object T with the touch probe TP. Next, the machine tool 100 maintains the turning angle of the table 156 at "-90°". Then, the machine tool 100 measures the position of the reference object T with the touch probe TP. Next, the machine tool 100 maintains the turning angle of the table 156 at "-120°". Then, the machine tool 100 measures the position of the reference object T with the touch probe TP.

[0067] Next, in step S6, it is assumed that the turning angle of the table 156 has reached the turning angle θ3 (third turning angle). When the table 156 is driven to the turning angle θ3 within the predetermined angle range Δθ, the machine tool 100 measures the reference object T belonging to the mounting area R2. That is, in step S6, the machine tool 100 does not measure the position of the reference object T that does not belong to the mounting area R2.

[0068] The turning angle θ3 is, for example, "-150°", "-180°". More specifically, the machine tool 100 first maintains the turning angle of the table 156 at "-150°". Then, the machine tool 100 measures the position of the reference object T with the touch probe TP. Next, the machine tool 100 maintains the turning angle of the table 156 at "-180°". Then, the machine tool 100 measures the position of the reference object T with the touch probe TP.

[0069] In this way, when the turning angle of the table 156 is the turning angle θ3, the machine tool 100 measures the mounting area R2 that is closer to the spindle 142.

[0070] Based on the completion of the measurement processes in steps S4 to S6, the operator changes the mounting position of the reference object T from the reference position P3 to the reference position P4. Then, the machine tool 100 executes the measurement processes in steps S4 to S6 again.

[0071] Next, the operator changes the mounting position of the reference object T from the reference position P4 to the reference position P5. Thereafter, the machine tool 100 starts the measurement process shown in FIG. 9. FIG. 9 is a diagram for explaining the measurement process when the reference object T is mounted at the reference positions P5 and P6.

[0072] Assume that in step S7, the turning angle of the table 156 reaches the turning angle θ1 (first turning angle). When the table 156 is driven to the turning angle θ1 within the predetermined angle range Δθ, the machine tool 100 measures the position of the reference object T in the mounting area R1 with the touch probe TP. That is, in step S7, the machine tool 100 does not measure the position of the reference object T.

[0073] Next, assume that in step S8, the turning angle of the table 156 reaches the turning angle θ2 (second turning angle). When the table 156 is driven to the turning angle θ2 within the predetermined angle range Δθ, the machine tool 100 measures the positions of the reference object T in the mounting areas R1 and R2 with the touch probe TP. That is, in step S8, the machine tool 100 measures the entire area.

[0074] The turning angle θ2 is, for example, "-60°", "-90°", "-120°". As a more specific measurement process in step S8, the machine tool 100 first maintains the turning angle of the table 156 at "-60°". Then, the machine tool 100 measures the position of the reference object T with the touch probe TP. Next, the machine tool 100 maintains the turning angle of the table 156 at "-90°". Then, the machine tool 100 measures the position of the reference object T with the touch probe TP. Next, the machine tool 100 maintains the turning angle of the table 156 at "-120°". Then, the machine tool 100 measures the position of the reference object T with the touch probe TP.

[0075] Next, assuming that in step S9, the turning angle of the table 156 has reached the turning angle θ3 (the third turning angle). When the machine tool 100 is driven to the turning angle θ3 within a predetermined angle range Δθ of the table 156, the reference object T belonging to the mounting area R2 is set as the measurement target. That is, in step S9, the machine tool 100 does not measure the position of the reference object T that does not belong to the mounting area R2.

[0076] The turning angle θ3 is, for example, "-150°" or "-180°". More specifically, the machine tool 100 first maintains the turning angle of the table 156 at "-150°". Then, the machine tool 100 measures the position of the reference object T with the touch probe TP. Next, the machine tool 100 maintains the turning angle of the table 156 at "-180°". Then, the machine tool 100 measures the position of the reference object T with the touch probe TP.

[0077] In this way, when the turning angle of the table 156 is the turning angle θ3, the machine tool 100 measures the mounting area R2 that is closer to the spindle 142.

[0078] Based on the completion of the measurement processes in steps S7 to S9, the operator changes the mounting position of the reference object T from the reference position P5 to the reference position P6. Then, the machine tool 100 executes the measurement processes in steps S7 to S9 again.

[0079] As described above, the machine tool 100 changes the measurement range of the reference object T according to the turning angle of the table 156. Thereby, the machine tool 100 can avoid interference between the spindle 142 and other members, and can measure the posture of the table 156 in a wider turning angle range. Also, the machine tool 100 can measure the positions of the set of reference objects T arranged in a wider range at each turning angle, and can measure the posture of the table 156 more accurately. As a result, the geometric error related to the turning axis of the table 156 can be corrected more accurately.

[0080] In the above description, two reference positions P1 and P2 are given as examples of the first reference position belonging to the mounting area R1 excluding the mounting area R2. However, the first reference position may be one or three or more.

[0081] Also, in the above description, two reference positions P3 and P4 are given as examples of the second reference position belonging to the overlapping area of the mounting areas R1 and R2. However, the second reference position may be one or three or more.

[0082] Furthermore, in the above description, two reference positions P5 and P6 are given as examples of the third reference position belonging to the mounting area R2 excluding the mounting area R1. However, the third reference position may be one or three or more.

[0083] Also, the above first to third reference positions with respect to the turning angle of the table 156 can be determined based on any reference. As an example, the distance from the touch probe TP in the axial direction (Z-axis direction) of the main shaft 142 to the above first reference position is defined as the "first distance", the distance from the touch probe TP in the axial direction of the main shaft 142 to the above second reference position is defined as the "second distance", and the distance from the touch probe TP in the axial direction of the main shaft 142 to the above third reference position is defined as the "third distance". When the table 156 is at the turning angle θ1, the above first distance is shorter than the above second distance, and the above second distance is shorter than the above third distance. Also, when the table 156 is at the turning angle θ3, the above third distance is shorter than the above second distance, and the above second distance is shorter than the above first distance.

[0084] Also, in the above description, an example of performing the measurement process while sequentially changing the mounting positions of one reference object T at the reference positions P1 to P6 has been described. However, the measurement process may be performed with a plurality of reference objects T mounted at the reference positions. In this case, the machine tool 100 measures the positions of the plurality of reference objects T at each turning angle of the table 156.

[0085] In the above description, an example in which the reference positions P1 to P6 are divided into two mounting regions R1 and G2 has been described. However, the reference positions may be divided into three or more mounting regions. In this case, the overlapping region between the first and second mounting regions is different from the overlapping region between the second and third mounting regions.

[0086] <D. Drive mechanism of machine tool 100> Next, with reference to FIG. 10, the drive mechanism in the machine tool 100 will be described. FIG. 10 is a diagram showing an example of the drive mechanism of the machine tool 100.

[0087] As shown in FIG. 10, the machine tool 100 includes a control unit 50, a spindle drive unit 230, and a table drive unit 240.

[0088] The control unit 50 controls various devices within the machine tool 100. The device configuration of the control unit 50 is arbitrary. The control unit 50 may be composed of a single control unit or a plurality of control units. As an example, the control unit 50 includes at least one of a CNC (Computer Numerical Control) and a PLC (Programmable Logic Controller).

[0089] The spindle drive unit 230 is a drive mechanism for directly or indirectly driving the spindle 142. The spindle drive unit 230 may be composed of a single drive unit or a plurality of drive units. In the example of FIG. 10, the spindle drive unit 230 is composed of motor drivers 231C, 231X, 231Z and motors 232C, 232X, 232Y.

[0090] The motor driver 231C sequentially receives from the control unit 50 an input of a target rotation angle or a target rotation speed of the main shaft 142 about the axial direction of the main shaft 142, and outputs a current corresponding to the target rotation angle or the target rotation speed to the motor 232C. The motor 232C rotationally drives the main shaft 142 about the axial direction of the main shaft 142. The motor 232C may be an AC motor, a stepping motor, a servo motor, or any other type of motor.

[0091] The motor driver 231X sequentially receives from the control unit 50 an input of a target position of the main shaft 142 in the X-axis direction, and outputs a current corresponding to the target position to the motor 232X. Thereby, the motor 232X drives the main shaft 142 to an arbitrary position in the X-axis direction. The motor 232X may be an AC motor, a stepping motor, a servo motor, or any other type of motor.

[0092] The motor driver 231Y sequentially receives from the control unit 50 an input of a target position of the main shaft 142 in the Y-axis direction, and outputs a current corresponding to the target position to the motor 232Y. Thereby, the motor 232Y drives the main shaft 142 to an arbitrary position in the Y-axis direction. The motor 232Y may be an AC motor, a stepping motor, a servo motor, or any other type of motor.

[0093] The table drive unit 240 is a drive mechanism for directly or indirectly driving the table 156. The table drive unit 240 may be composed of a single drive unit or a plurality of drive units. In the example of FIG. 10, the table drive unit 240 is composed of motor drivers 241A, 241B, 241Z and motors 242A, 242B, 242Z.

[0094] The motor driver 241A receives an input of a target value regarding the turning angle of the table 156 around the turning axis AXA (see FIG. 2) described above, and outputs a current corresponding to the target value to the motor 242A. Thereby, the motor driver 241A controls the turning angle of the table 156 around the turning axis AXA. The motor 242C may be an AC motor, a stepping motor, a servo motor, or any other type of motor.

[0095] The motor driver 241B receives an input of a target value regarding the rotation angle of the table 156 around the rotation axis AXB (see FIG. 2) described above, and outputs a current corresponding to the target value to the motor 242B. Thereby, the motor driver 241B controls the rotation angle of the table 156 around the rotation axis AXB. The motor 242C may be an AC motor, a stepping motor, a servo motor, or any other type of motor.

[0096] The motor driver 241Z sequentially receives from the control unit 50 an input of the target position of the table 156 in the Z-axis direction, and outputs a current corresponding to the target position to the motor 242Z. Thereby, the motor 242Z moves the table 156 to an arbitrary position in the Z-axis direction. The motor 242Z may be an AC motor, a stepping motor, a servo motor, or any other type of motor.

[0097] <E. Hardware Configuration of Control Unit 50> Next, with reference to FIG. 11, the hardware configuration of the control unit 50 shown in FIG. 10 will be described. FIG. 11 is a diagram showing an example of the hardware configuration of the control unit 50.

[0098] As described above, the control unit 50 may be a CNC or a PLC. FIG. 11 shows the hardware configuration of the control unit 50 as a CNC.

[0099] The control unit 50 includes, for example, a control circuit 101, a ROM (Read Only Memory) 102, a RAM (Random Access Memory) 103, a communication interface 104, and an auxiliary storage device 120. These components are connected to an internal bus 109.

[0100] The control circuit 101 is constituted by, for example, at least one integrated circuit. The integrated circuit can be constituted by, for example, at least one CPU (Central Processing Unit), at least one GPU (Graphics Processing Unit), at least one ASIC (Application Specific Integrated Circuit), at least one FPGA (Field Programmable Gate Array), or a combination thereof.

[0101] The control circuit 101 controls the operation of the control unit 50 by executing various programs such as a measurement program 122 and a correction program 124. The measurement program 122 is a program for realizing the measurement process shown in FIG. 7 described above. The correction program 124 is a program for correcting the geometric error related to the swivel axis of the table 156 based on the actually measured value measured by the measurement process shown in FIG. 7 described above.

[0102] Based on receiving an execution instruction of a program, the control circuit 101 reads the program from the ROM 102 into the RAM 103. The RAM 103 functions as a working memory and temporarily stores various data necessary for the execution of the program.

[0103] The communication interface 104 is an interface for realizing communication with various devices. The machine tool 100 communicates with various drive units (for example, the main shaft drive unit 230 and the table drive unit 240 described above) for realizing additional processing of the workpiece via the communication interface 104, for example.

[0104] The auxiliary storage device 120 is a storage medium such as a hard disk or a flash memory, for example. The auxiliary storage device 120 stores a measurement program 122, a correction program 124, and the like. The storage locations of the measurement program 122 and the correction program 124 are not limited to the auxiliary storage device 120, and may be stored in the storage area of the control circuit 101 (for example, cache memory), ROM 102, RAM 103, an external device (for example, a server), or the like.

[0105] Also, the measurement program 122 may be provided incorporated into a part of an arbitrary program instead of as a single program. In this case, various processes according to the present embodiment are realized in cooperation with an arbitrary program. Even a program that does not include such a part of the module does not deviate from the gist of the measurement program 122 according to the present embodiment. Furthermore, part or all of the functions provided by the measurement program 122 may be realized by dedicated hardware. Furthermore, the control unit 50 may be configured in a form such as a so-called cloud service in which at least one server executes a part of the processing of the measurement program 122.

[0106] <F. Control Flow> Next, with reference to FIG. 12, the control flow of the measurement process described in FIG. 7 above will be described. FIG. 12 is a flowchart showing the flow of the measurement process.

[0107] The process shown in FIG. 12 is realized, for example, when the control unit 50 of the machine tool 100 executes the above-described measurement program 122. In other aspects, part or all of the process may be executed by circuit elements or other hardware.

[0108] In step S110, the control unit 50 determines whether it has received a measurement instruction for the measured value used for the geometric error related to the turning axis of the table 156. The measurement instruction is issued, for example, in response to an operation on the operation panel 200 described above. When the control unit 50 determines that it has received the measurement instruction (YES in step S110), it switches the control to step S112. Otherwise (NO in step S110), the control unit 50 executes the process of step S110 again.

[0109] In step S112, the control unit 50 starts a process of turning and driving the table 156 within a predetermined angle range Δθ around the turning axis AXA.

[0110] Assume that in step S114, the turning angle of the table 156 reaches a predetermined turning angle θ1. Based on this, the control unit 50 maintains the turning angle of the table 156 at the turning angle θ1 and measures the position of the reference object T belonging to the mounting area R1. Then, the control unit 50 resumes the turning drive of the table 156.

[0111] Assume that in step S116, the turning angle of the table 156 reaches a predetermined turning angle θ2. Based on this, the control unit 50 maintains the turning angle of the table 156 at the turning angle θ2 and measures the reference objects T belonging to the mounting areas R1 and R2. Then, the control unit 50 resumes the turning drive of the table 156.

[0112] Assume that in step S118, the turning angle of the table 156 reaches a predetermined turning angle θ3. Based on this, the control unit 50 maintains the turning angle of the table 156 at the turning angle θ3 and measures the position of the reference object T belonging to the mounting area R2.

[0113] In step S119, the control unit 50 determines whether the measurement process has been completed at all the positions of the above-mentioned reference positions P1 to P6. When the control unit 50 determines that the measurement process at all the positions of the reference positions P1 to P6 has been completed (YES in step S119), the control is switched to step S120. Otherwise (NO in step S119), the control unit 50 prompts the operator to replace the reference object with a different reference position. Based on the completion of the replacement operation of the reference object, the control unit 50 returns the control to step S112.

[0114] In step S120, the control unit 50 outputs the measurement results in the processes of steps S114, S116, and S118. As an example, the control unit 50 outputs each position of the reference object T in association with each turning angle of the table 156 and the reference positions P1 to P6 in steps S114, S116, and S118. Each position of the reference object T is indicated by, for example, three-dimensional coordinate values.

[0115] Each position of the reference object T output in step S120 is used for the correction process of the turning axis of the table 156. Various correction algorithms are used for the correction process. Depending on the CNC, the correction process is installed as a standard function. When such a CNC receives the input of the position of the reference object T at each turning angle, it automatically corrects the drive parameters of the machine tool 100 in internal processing. That is, the user only needs to input the measured position of the reference object T at each turning angle with respect to the correction algorithm implemented as a standard function.

[0116] <G. Error correction process> Next, an example of the error correction process using the measurement position output in the above step S120 (see FIG. 12) will be described.

[0117] As described above, the machine tool 100 measures the center of the reference object T on the machine coordinates using the touch probe TP. The measurement is performed at a plurality of turning angles around the A axis. The reference object T is arranged at a plurality of positions on the table 156. FIG. 13 is a diagram showing the change in the position of the reference object T due to turning around the A axis. Note that the rotation angle of the table 156 around the B axis is fixed. When the turning angle of the A axis is determined to be a [deg], the reference object T in the coordinate system of the machine tool 100 i The i-th position of is represented by the following formula (1).

[0118]

Equation

[0119] When the A axis rotates ideally and the turning angle of the A axis is determined to be a, the position of the reference object T i is represented by the following formula (2).

[0120]

Equation

[0121]

Equation

[0122]

Equation

[0123] The position of the reference object T including geometric errors i is represented by the following formula (5) derived from the above formulas (3) and (4).

[0124]

Equation

[0125] [Number] Here, "ΔP i (a)" shown in Equation (6) is the error between the estimated position and the measured position, and is represented by the following Equation (7).

[0126] [Number] The machine tool 100 substitutes the measured position output in the above-described step S120 (see FIG. 12) into the above Equation (7), and calculates the geometric error and the rotation center related to the A axis so that the sum of the errors shown in the above Equation (6) becomes minimum. The geometric error and the rotation center are calculated, for example, by the least squares method. As described above, the machine tool 100 can simultaneously calculate the geometric error related to the A axis and the rotation center of the A axis.

[0127] The embodiments disclosed this time should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is shown not by the above description but by the scope of claims, and it is intended that all modifications within the meaning and scope equivalent to the scope of claims be included. [Explanation of Signs]

[0128] 50 Control unit, 100 Machine tool, 101 Control circuit, 102 ROM, 103 RAM, 104 Communication interface, 109 Internal bus, 120 Auxiliary storage device, 122 Measurement program, 124 Correction program, 130 Cover body, 140 Spindle head, 142 Spindle, 143 Housing, 150 Table mechanism, 152A Drive mechanism, 152B Drive mechanism, 154 Swivel table, 156 Table, 200 Operator panel, 230 Spindle drive unit, 231C Motor driver, 231X Motor driver, 231Y Motor driver, 231Z Motor driver, 232C Motor, 232X Motor, 232Y Motor, 240 Table drive unit, 241A Motor driver, 241B Motor driver, 241Z Motor driver, 242A Motor, 242B Motor, 242C Motor, 242Z Motor, AXA Swivel axis, AXB Rotation axis, DR Door, P1 Reference position, P2 Reference position, P3 Reference position, P4 Reference position, P5 Reference position, P6 Reference position, R1 Mounting area, R2 Mounting area, T Reference object, TL Tool, TP Touch probe, W Workpiece, Δθ Angle range, θ1 Swivel angle, θ2 Swivel angle, θ3 Swivel angle.

Claims

1. A machine tool capable of measuring measured values used for error correction processing of a rotation axis of a table on which a workpiece can be placed, wherein the table is configured to be able to mount a reference object, the mounting position of the reference object on the table, one or more first reference positions belonging to a first region on the table and not belonging to a second region on the table, one or more second reference positions belonging to an overlapping region between the first region and the second region, including one or more third reference positions belonging to the second region and not belonging to the first region, a table drive unit for driving the table to rotate about the rotation axis set to be parallel to the mounting surface of the table, a spindle having a rotation center set in a direction different from that of the rotation axis and capable of mounting a touch probe, a spindle drive unit for driving the spindle to feed relatively with respect to the table, and a control unit for controlling the machine tool, wherein the control unit, performs a drive process of driving the table to rotate within a predetermined angle range about the rotation axis, a first measurement process of measuring the position of the reference object at the first reference position and the second reference position with the touch probe when the table is driven to a first rotation angle within the predetermined angle range, a second measurement process of measuring the position of the reference object at the first reference position, the second reference position, and the third reference position with the touch probe when the table is driven to a second rotation angle within the predetermined angle range, a third measurement process of measuring the position of the reference object at the second reference position and the third reference position with the touch probe when the table is driven to a third rotation angle within the predetermined angle range, and an output process of outputting each position measured in the first to third measurement processes as the measured value, wherein the second rotation angle is an angle between the first rotation angle and the third rotation angle. A machine tool.

2. The control unit further performs the error correction process based on the measured value, and in the error correction process, the rotation center related to the rotation axis and the geometric error related to the rotation axis are calculated. The machine tool according to claim 1.

3. The number of the first reference positions is two or more, and the number of the third reference positions is two or more. The machine tool according to claim 1 or 2.

4. The number of the second reference positions is two or more, the machine tool according to claim 1 or 2.

5. When the distance from the touch probe to the first reference position in the axial direction of the spindle is defined as a first distance, the distance from the touch probe to the second reference position in the axial direction of the spindle is defined as a second distance, and the distance from the touch probe to the third reference position in the axial direction of the spindle is defined as a third distance, when the table is at the first turning angle, the first distance is shorter than the second distance, and the second distance is shorter than the third distance, when the table is at the third turning angle, the third distance is shorter than the second distance, and the second distance is shorter than the first distance, the machine tool according to claim 1 or 2.

6. A measuring method for measuring, by a machine tool, measured values used for error correction processing of a turning axis of a table on which a workpiece can be placed, the table is configured to be capable of mounting a plurality of reference objects, the mounting positions of the reference objects on the table include one or more first reference positions that belong to a first area on the table and do not belong to a second area on the table, one or more second reference positions that belong to an overlapping area between the first area and the second area, and one or more third reference positions that belong to the second area and do not belong to the first area, the machine tool includes a table drive unit for driving the table to turn about the turning axis set to be parallel to the mounting surface of the table, a spindle having a rotation center set in a direction different from that of the turning axis and capable of mounting a touch probe, and a spindle drive unit for driving the spindle to feed relatively with respect to the table, the measuring method includes a driving step of driving the table to turn within a predetermined angular range about the turning axis, a first measuring step of measuring the positions of the reference objects at the first reference position and the second reference position with the touch probe when the table is driven to a first turning angle within the predetermined angular range, and a second measuring step of measuring the positions of the reference objects at the first reference position, the second reference position, and the third reference position with the touch probe when the table is driven to a second turning angle within the predetermined angular range. A third measurement step of measuring the position of the reference object at the second reference position and the third reference position with the touch probe when the table is driven to a third turning angle within the predetermined angle range; An output step of outputting each position measured in the first to third measurement steps as the measured value; The second turning angle is an angle between the first turning angle and the third turning angle, the measuring method.

7. A measurement program for measuring with a machine tool the measured values used for error correction processing of the turning axis of a table on which a workpiece can be placed, The table is configured to be able to mount a plurality of reference objects, The mounting positions of the reference objects on the table are One or more first reference positions belonging to a first region on the table and not belonging to a second region on the table, One or more second reference positions belonging to an overlapping region between the first region and the second region, Including one or more third reference positions belonging to the second region and not belonging to the first region, The machine tool is A table drive unit for driving the table to turn about the turning axis set to be parallel to the mounting surface of the table, A spindle having a rotation center set in a direction different from the turning axis and capable of mounting a touch probe, And a spindle drive unit for relatively feeding and driving the spindle with respect to the table, The measurement program causes a computer to A drive process of driving the table to turn within a predetermined angle range about the turning axis, A first measurement process of measuring the position of the reference object at the first reference position and the second reference position with the touch probe when the table is driven to a first turning angle within the predetermined angle range, A second measurement process of measuring the position of the reference object at the first reference position, the second reference position, and the third reference position with the touch probe when the table is driven to a second turning angle within the predetermined angle range, A third measurement process of measuring the position of the reference object at the second reference position and the third reference position with the touch probe when the table is driven to a third turning angle within the predetermined angle range, And an output process of outputting each position measured in the first to third measurement processes as the measured value. The measurement program in which the second turning angle is an angle between the first turning angle and the third turning angle.

Images