Numerical control device and numerical control method for machine tool

Abstract

To provide a method for correcting thermal displacement of a rotary table type machine tool having two workpiece supporting parts.SOLUTION: A machine tool comprises a rotary table, a spindle, a linear shaft, and a driving member. The rotary table has first and second supporting parts that support a workpiece and is rotatable about a rotation axis between a first state in which the first supporting part is positioned in a machining region and the second supporting part is positioned in a non-machining region, and a second state in which the first supporting part is positioned in the non-machining region and the second supporting part is positioned in the machining region. The spindle is used for supporting a tool, and the tool machines a workpiece supported by the first and second supporting parts. The linear shaft is used for relatively moving the rotary table and the spindle. The driving member is used for driving the linear shaft. The numerical control device is capable of executing a first measurement process for measuring a measurement point positioned on one of the first and second supporting parts, a first correction process for correcting a drive amount of the driving member on the basis of a measurement result, and a machining process for machining a workpiece on the other of the first and second supporting parts on the basis of a correction result.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a numerical control device and a numerical control method for correcting thermal displacement of a linear axis of a machine tool. [Background technology]

[0002] In the prior art, one method for improving the machining accuracy of a machining machine tool is to calculate the amount of thermal displacement of the ball screw that drives the movable worktable and correct the amount of drive of the movable worktable.

[0003] As an example, Patent Document 1 discloses a method in which a reference part (Invar alloy material) is placed on a workbench or jig, measured using a touch probe, and thermal displacement is corrected based on the measured dimensional error. However, Patent Document 1 does not disclose an effective method for correcting thermal displacement in a rotary table-type machine tool equipped with two workpiece support parts. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-212765 Summary of the Invention

[0005] The present invention provides a numerical control device and a numerical control method for a machine tool that solves the above problems, and provides an effective means for compensating for thermal displacement in a rotary table type machine tool.

[0006] One embodiment of the present invention provides a numerical control device for a machine tool including a rotary table, a spindle, a linear axis, and a drive member. The rotary table has first and second support members that support a workpiece, and is rotatable about a rotation axis between a first state in which the first support member is located in a machining area and the second support member is located in a non-machining area, and a second state in which the first support member is located in the non-machining area and the second support member is located in the machining area. The spindle is used to hold a tool, and the tool machines the workpiece supported by the first and second support members. The linear axis is used to move the rotary table and the spindle relative to each other. The drive member is used to drive the linear axis. The numerical control device is capable of performing a first measurement process that measures a measurement point located on one of the first and second support members, a first correction process that corrects the drive amount of the drive member based on the measurement result obtained in the first measurement process, and a machining process that performs machining of the workpiece on the other of the first and second support members based on the correction result obtained in the first correction process.

[0007] A numerical control device according to one embodiment of the present invention can further execute a second measurement process for measuring a measurement point located on the other of the first support part and the second support part, and a second correction process for correcting the drive amount of the drive member based on the measurement result obtained in the second measurement process, and the machining process performs machining of the workpiece based on the most recent correction result obtained in the first correction process and the second correction process.

[0008] A numerical control device according to one embodiment of the present invention can further execute a measurement time determination process that determines the next measurement time based on the measurement results obtained in the first measurement process and the measurement results obtained in the second measurement process.

[0009] A numerical control device according to one embodiment of the present invention can further execute a determination process for determining whether the elapsed time from the time when the first measurement process or the second measurement process is completed is equal to or greater than a reference time; an execution command transmission process for transmitting an execution command for the first measurement process or the second measurement process when the determination process determines that the elapsed time is equal to or greater than the reference time; an update time determination process for determining an update time based on the measurement results obtained in the first measurement process and the measurement results obtained in the second measurement process; and an update process for updating the reference time based on the update time determined in the update time determination process.

[0010] A numerical control device according to one embodiment of the present invention determines an update time in an update time determination process based on the difference between the positions of the measurement points measured in the first measurement process and the second measurement process and the estimated positions of the measurement points in the first measurement process and the second measurement process estimated from the positions of the measurement points measured in the first measurement process and the second measurement process, relative to the elapsed time.

[0011] In an update time determination process, a numerical control device according to one embodiment of the present invention determines an update time based on the value of the maximum value among multiple differences between the positions of measurement points measured in the first measurement process and the second measurement process and the estimated position, relative to the elapsed time.

[0012] A numerical control device according to one embodiment of the present invention can further execute an execution command deletion process to delete an execution command for the first measurement process or the second measurement process when the judgment process determines that the elapsed time is less than the reference time.

[0013] A numerical control device according to one embodiment of the present invention measures at least two measurement points located on one of the first support part and the second support part in a first measurement process, measures at least two measurement points located on the other of the first support part and the second support part in a second measurement process, and corrects the drive amount of the drive member by linear interpolation based on the measurement results of the at least two measurement points obtained in the first measurement process and the second measurement process.

[0014] A numerical control device according to one embodiment of the present invention displays, on a history confirmation screen that displays the history of measurement results obtained in the first measurement process and the second measurement process, whether the measurement was performed using the first support part or the second support part in a recognizable manner.

[0015] In a numerical control device according to one embodiment of the present invention, the linear axes are a first axis, a second axis, and a third axis that are perpendicular to one another, and the machine tool includes a base, a column, and a pedestal. Here, the column supports the main spindle so that the main spindle can move along the third axis. The pedestal is installed on the base and supports the column so that the column can move along the first axis and the second axis. The rotary table is mounted on the base so that it can rotate around the rotation axis.

[0016] In a numerical control device according to an embodiment of the present invention, the first measurement process measures a measurement point using a measuring tool attached to a spindle.

[0017] One embodiment of the present invention provides a numerical control method for a machine tool including a rotary table, a spindle, a linear axis, and a drive member. The rotary table has first and second support portions for supporting a workpiece, and is rotatable about a rotation axis between a first state in which the first support portion is located in a machining area and the second support portion is located in a non-machining area, and a second state in which the first support portion is located in the non-machining area and the second support portion is located in the machining area. The spindle is used to hold a tool, and the tool machines the workpiece supported by the first and second support portions. The linear axis is used to move the rotary table and the spindle relative to each other. The drive member is used to drive the linear axis. The above-mentioned numerical control method includes performing a first measurement process to measure a measurement point located on one of the first support part and the second support part, performing a first correction process to correct the drive amount of the drive member based on the measurement result obtained in the first measurement process, and performing a processing process to process the workpiece on the other of the first support part and the second support part based on the correction result obtained in the first correction process.

[0018] A numerical control method according to one embodiment of the present invention further includes performing a second measurement process to measure a measurement point located on the other of the first support part and the second support part, and performing a second correction process to correct the drive amount of the drive member based on the measurement result obtained in the second measurement process, and the processing process performs processing of the workpiece based on the most recent correction result among the correction results obtained in the first correction process and the second correction process.

[0019] The numerical control method according to one embodiment of the present invention further includes determining a next measurement time based on the measurement result obtained in the first measurement process and the measurement result obtained in the second measurement process.

[0020] A numerical control method according to one embodiment of the present invention further includes determining whether the elapsed time from the completion of the first measurement process or the second measurement process is equal to or greater than a reference time, issuing a command to execute the first measurement process or the second measurement process when it is determined that the elapsed time is equal to or greater than the reference time, determining an update time based on the measurement results obtained in the first measurement process and the measurement results obtained in the second measurement process, and updating the reference time based on the determined update time.

[0021] In a numerical control method according to one embodiment of the present invention, when determining an update time, the update time is determined based on the difference between the positions of the measurement points measured in the first measurement process and the second measurement process and the estimated positions of the measurement points in the first measurement process and the second measurement process estimated from the positions of the measurement points measured in the first measurement process and the second measurement process, relative to the elapsed time.

[0022] In a numerical control method according to one embodiment of the present invention, when determining an update time, the update time is determined based on the value of the maximum value among multiple differences between the positions of measurement points measured in the first measurement process and the second measurement process and the estimated position, relative to the elapsed time.

[0023] A numerical control method according to an embodiment of the present invention further includes deleting an execution command for the first measurement process or the second measurement process when it is determined that the elapsed time is less than the reference time.

[0024] A numerical control method according to one embodiment of the present invention comprises: a first measurement process for measuring at least two measurement points located on one of the first support part and the second support part; a second measurement process for measuring at least two measurement points located on the other of the first support part and the second support part; and a first correction process and a second correction process for correcting the drive amount of the drive member by linear interpolation based on the measurement results of the at least two measurement points obtained in the first measurement process and the second measurement process.

[0025] A numerical control method according to one embodiment of the present invention further includes displaying the history of the measurement results obtained in the first measurement process and the second measurement process on a history confirmation screen, and displaying in a manner that enables recognition whether the measurements were made at the first support part or the second support part.

[0026] In a numerical control method according to one embodiment of the present invention, the linear axes are a first axis, a second axis, and a third axis that are perpendicular to one another, and the machine tool includes a base, a column, and a pedestal. Here, the column supports the main spindle so that the main spindle can move along the third axis. The pedestal is installed on the base and supports the column so that the column can move along the first axis and the second axis. The rotary table is installed on the base so that it can rotate around the rotation axis.

[0027] In a numerical control method according to an embodiment of the present invention, the first measurement process measures a measurement point using a measuring tool attached to a spindle.

[0028] Based on the above, in a numerical control device and numerical control method for a machine tool according to one embodiment of the present invention, in a rotary table-type machine tool having two support parts, the effects of thermal displacement due to thermal expansion of a linear axis can be eliminated by measuring the measurement point of one of the support parts, performing correction based on the measurement results, and applying the correction results to the machining process of the other support part. Furthermore, by separately correcting the two support parts and performing machining based on the most recent correction results, machining accuracy can be made more stable. Furthermore, by determining the next measurement time based on measurement results obtained from multiple measurement processes, deterioration of cycle time due to actual measurement can be avoided. [Brief explanation of the drawings]

[0029] [Figure 1] FIG. 1 is a three-dimensional view schematically showing a machine tool. [Figure 2] FIG. 2 is a block diagram schematically showing the peripheral configuration of a numerical control device 60. [Figure 3] FIG. 2 is a schematic diagram illustrating thermal displacement of a machine tool. [Figure 4] 1 is a flowchart of a numerical control method for a machine tool according to an embodiment of the present invention. [Figure 5] FIG. 2 is a schematic top view of a rotary table 8 according to one embodiment of the present invention. [Figure 6A] FIG. 2 is a schematic diagram of the execution of a measurement process according to an embodiment of the present invention. [Figure 6B] FIG. 2 is a schematic diagram of the execution of a measurement process according to an embodiment of the present invention. [Figure 6C] FIG. 2 is a schematic diagram of the execution of a measurement process according to an embodiment of the present invention. [Figure 6D] FIG. 2 is a schematic diagram of the execution of a measurement process according to an embodiment of the present invention. [Figure 7A] FIG. 4 is a schematic diagram of the execution of a correction process according to an embodiment of the present invention. [Figure 7B] FIG. 4 is a schematic diagram of the execution of a correction process according to an embodiment of the present invention. [Figure 8] 1 is a flowchart of a numerical control method for a machine tool according to an embodiment of the present invention. [Figure 9] FIG. 9 is a schematic diagram of a history confirmation screen 90 according to an embodiment of the present invention. [Figure 10] 10 is a flowchart of a method for updating a reference time used in performing a measurement process according to an embodiment of the present invention. [Figure 11] FIG. 2 is a schematic diagram of update time determination according to an embodiment of the present invention; [Figure 12A] FIG. 2 is a schematic diagram of issuing / deleting an execution command according to an embodiment of the present invention. [Figure 12B] FIG. 2 is a schematic diagram of issuing / deleting an execution command according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0030] Examples of illustrative embodiments of the invention are illustrated in the accompanying drawings, in which: Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts.

[0031] Specific examples of a numerical control device and a numerical control method for a machine tool according to an embodiment of the present invention will be described below with reference to drawings of the machine tool. In the following description, up, down, front, back, left and right in the drawings will be used. Figure 1 is a three-dimensional diagram showing a schematic diagram of a machine tool. Note that a tool magazine for storing replacement tools is not shown in Figure 1.

[0032] The machine tool includes a base 1 that is rectangular in plan view. A pedestal 10 that supports a column 2 is provided on the base 1. The pedestal 10 supports the column 2 so that the column 2 is movable along an X-axis (first axis) and a Y-axis (second axis). The pedestal 10 moves along the X-axis direction (left-right direction) and the Y-axis direction (front-back direction) (see FIG. 3) by rotation of an X-axis motor 82 and a Y-axis motor 83 (see FIG. 2).

[0033] A vertically movable spindle head 4 is provided on the front of the column 2. The spindle head 4 has a spindle 4a. A tool 4b (see Figure 3) or a measuring tool 4c (see Figure 6A) is attached to the lower end of the spindle 4a. The column 2 supports the spindle 4a so that the spindle 4a can move along the Z-axis (third axis). The spindle head 4 moves in the Z-axis direction (up and down) by rotation of a Z-axis motor 81 (see Figure 2) provided on the column 2. By the vertical movement of the spindle head 4, the spindle 4a moves between an exchange position where the tool 4b or measuring tool 4c attached to the spindle 4a is exchanged and a processing position where the workpiece W is processed.

[0034] A spindle motor 6 for rotating the spindle 4a is provided above the spindle head 4. The spindle 4a and the tool are rotated by the rotation of the spindle motor 6. The spindle 4a and the tool are rotated by the rotation of the spindle motor 6.

[0035] A rotary table 8 is provided on the base 1 below the spindle head 4. The rotary table is provided on the base 1 so as to be rotatable about a rotation axis. The rotary table 8 rotates about the rotation axis by rotation of a table motor 84 (see FIG. 2). The rotary table 8 has a first support portion 11 and a second support portion 12 that hold a workpiece, and is rotatable about the rotation axis between a first state and a second state. Here, in the first state, the first support portion 11 is located in the machining area, and the second support portion 12 is located in the non-machining area. In the second state, the first support portion 11 is located in the non-machining area, and the second support portion 12 is located in the machining area.

[0036] The first support unit 11 includes an A-axis motor 11a, a support unit 11b, a rotary support base 11c, and a clamp unit 11d. The A-axis motor 11a and the support unit 11b are spaced apart from each other in the left-right direction. The rotary support base 11c is shaped like a long plate extending left-right. The A-axis motor 11a and the support unit 11b support the left and right ends of the rotary support base 11c so that the rotary support base 11c can rotate around the A-axis (an axis whose axial direction is in the left-right direction). The rotary support base 11c is rotated by the rotation of the A-axis motor 11a. The clamp unit 11d secures the workpiece using compressed air delivered from a compressor (not shown). The clamp unit 11d is provided on the top surface of the rotary support base 11c. The clamp unit 11d secures and releases the workpiece manually or automatically.

[0037] The second support unit 12 includes an A-axis motor 12a, a support unit 12b, a rotary support base 12c, and a clamp unit 12d. The A-axis motor 12a and the support unit 12b are spaced apart from each other in the left-right direction. The rotary support base 12c is shaped like a long plate extending left and right. The A-axis motor 12a and the support unit 12b are rotatably supported around the left and right ends A of the rotary support base 12c. The rotary support base 12c is rotated by the rotation of the A-axis motor 12a. The clamp unit 12d secures the workpiece using compressed air delivered from a compressor (not shown). The clamp unit 12d is provided on the upper surface of the rotary support base 12c. The clamp unit 12d secures and releases the workpiece manually or automatically.

[0038] A numerical control device 60 is provided on the back of the column 2. FIG. 2 is a block diagram showing a schematic configuration of the numerical control device 60. The numerical control device 60 includes a control unit 61, a random access memory (RAM) 62, a storage unit 63, an input interface 64, an output interface 65, and the like. The control unit 61 includes a central processing unit (CPU), a microprocessor (MPU), a logic circuit, and the like. The storage unit 63 includes a rewritable storage medium, such as an erasable programmable read-only memory (EPROM), an electrically erasable programmable read-only memory (EEPROM), or a hard disk. The storage unit 63 stores various parameters, including a control program, a machining program for machining a workpiece, and a setting parameter for determining the state of the rotary table 8. The setting parameter is, for example, the angle of the table motor 84. An angle of 0 degrees indicates that the first support unit 11 is located within the machining area, and an angle of 180 degrees indicates that the second support unit 12 is located within the machining area.

[0039] The control unit 61 reads out the control program and machining program stored in the storage unit 63 into the RAM 62 and executes them. The RAM 62 temporarily stores the control program and machining program read out from the storage unit 63, as well as various data generated during the processing.

[0040] The input device 71 is connected to the input interface 64. The input device 71 is equipped with a keyboard, a touch panel, or the like, and accepts operations by the operator. The operator operates the input device 71 to set various parameters. The input device 71 outputs signals to the input interface 64. The control unit 61 outputs drive signals or stop signals to the spindle motor 6, A-axis motors 11a and 12a, Z-axis motor 81, X-axis motor 82, Y-axis motor 83, and rotary table motor 84 via the output interface 65.

[0041] The X-axis motor 82 has an encoder 82e. The Y-axis motor 83 has an encoder 83e. The Z-axis motor 81 has an encoder 81e. The spindle motor 6 has an encoder 6e. The rotary table motor 84 has an encoder 84e. The A-axis motor 11a has an encoder 11e. The A-axis motor 12a has an encoder 12e. The encoders 6e, 11e, 12e, 81e, 82e, 83e, and 84e output detection signals to the input interface 64. The control unit 61 controls the processing of the control program and machining program and the driving of each motor based on the signals input to the input interface 64.

[0042] FIG. 3 is a schematic diagram illustrating thermal displacement of a machine tool. The machine tool's spindle 4a is supported by a column 2, which is supported by a base 10. The spindle 4a moves relative to a first support 11 located on a rotary table 8 via a linear axis 7. The spindle 4a holds a tool 4b for machining a workpiece W fixed to a clamp 11d of the first support 11. The linear axis 7 is, for example, a ball screw, and is supported by a bearing 7a fixed to the base 1 and a bearing 7b that is movable in the Y-axis direction. The linear axis 7 rotates around its axis when driven by a Y-axis motor 83, allowing the spindle 4a, supported by the base 10 and the column 2, to move in the Y-axis direction.

[0043] The linear axis 7 undergoes linear expansion due to the influence of heat from the Y-axis motor 83, the heat from the bearings 7a and 7b, and the heat from the ball screw / nut. Therefore, in the case of a machine that uses the rotation angle of the motor for positioning (semi-closed loop method), the position of the base part 10 on the linear axis 7 displaces by the amount of linear expansion (dashed line in the figure), and the machining position of the tool 4b on the workpiece W displaces from position wp1 to position wp2.

[0044] In this embodiment, regarding this thermal displacement, a measurement point located on either the first support part 11 or the second support part 12 is measured, the drive amount of the Y-axis motor 83 is corrected based on the measurement result, and the workpiece W located on the other of the first support part 11 and the second support part 12 is machined based on the correction result.

[0045] In detail, FIG. 4 is a flowchart of a method for numerically controlling a machine tool according to an embodiment of the present invention.

[0046] In step S402, the numerical control device 60, via the control unit 61, executes a first measurement process to measure a measurement point located on one of the first support 11 and the second support 12. In some embodiments, the measurement point is, for example, a measurement pin attached to the clamp 11d or 12d. Alternatively, the measurement point may be, for example, but is not limited to, an edge portion of the side surface of the clamp 11d or 12d. In some embodiments, the number of measurement points is at least two, and these measurement points are, for example, arranged opposite each other on the first support 11 or the second support 12 (e.g., arranged on both sides or diagonally opposite the clamp) and can be used for compensation processing for thermal displacement of a linear axis provided in the X-axis direction (left-right direction) and / or the Y-axis direction (front-back direction). In some embodiments, the at least two measurement points have, for example, different heights, and can perform compensation processing for thermal displacement of a linear axis provided in the Z-axis direction (up-down direction).

[0047] In step S404, the control unit 61 executes a first correction process to correct the drive amount of the drive member based on the measurement results obtained in the first measurement process. As an example, the drive member here refers to a motor that drives a linear axis provided in the X-axis direction (left-right direction), the Y-axis direction (front-back direction), and / or the Z-axis direction (up-down direction) (i.e., the above-mentioned X-axis motor 82, Y-axis motor 83, and / or Z-axis motor 81), but is not limited thereto. In some embodiments, the control unit 61 executes the first measurement process, for example, at a first time point just after the machine tool is started and at a second time point after a predetermined time has elapsed, to obtain measurement results for each measurement point, and can correct the drive amount of the drive member by linear interpolation based on the measurement results for each measurement point obtained in the two first measurement processes.

[0048] In step S406, the control unit 61 executes a processing process for processing the workpiece at the other of the first support unit 11 and the second support unit 12 based on the correction result obtained in the first correction process.

[0049] This eliminates the effects of thermal displacement caused by thermal expansion of the linear axis, and since the linear axis affected by thermal displacement is located on the spindle side rather than the rotary table side, accuracy can be maintained even when the measurement results of each support part are used repeatedly.

[0050] In some embodiments, the control unit 61 performs a measurement process on the other of the first support unit 11 and the second support unit 12 located in the non-machining area, performs a correction process based on the measurement results, corrects the drive amount of the drive member, and then performs machining of the workpiece on one of the first support unit 11 and the second support unit 12 located in the machining area based on the corrected drive amount of the drive member.

[0051] In some embodiments, the control unit 61 rotates the other of the first support unit 11 and the second support unit 12 to the machining area, performs a measurement process on the other of the first support unit 11 and the second support unit 12 located in the machining area, performs a correction process based on the measurement results and corrects the drive amount of the driving part, and then rotates one of the first support unit 11 and the second support unit 12 to the machining area and performs machining of the workpiece on one of the first support unit 11 and the second support unit 12 located in the machining area based on the drive amount of the driving part after the correction.

[0052] For example, Figure 5 is a schematic top view of a turntable 8 according to one embodiment of the present invention. The turntable 8 rotates around a rotation axis 8a. L in Figure 5 is a boundary line extending left and right that passes through the rotation axis 8a when the turntable 8 is stopped. The area behind the boundary line L is a machining area where the workpiece is machined, and the area in front of it is a non-machining area separated from the machining area. In Figure 1, the first support part 11 is located behind the turntable 8 and within the machining area. The second support part 12 is located in front of the turntable 8 and in the non-machining area.

[0053] In this embodiment, by placing measurement points 12f, 12g on diagonal corners around clamp portion 12d (or workpiece W') of second support portion 12, numerical control device 60 can measure measurement points 12f, 12g via a measuring tool provided on spindle 4a, correct the drive amount of the drive member that drives the linear axis based on the measurement result, and process workpiece W on first support portion 11 based on the correction result. The measuring tool is, for example, a touch probe or a non-contact sensor (such as an optical or acoustic wave proximity sensor), but this embodiment is not limited to this type.

[0054] 6A to 6D are schematic diagrams illustrating the execution of a measurement process according to an embodiment of the present invention. In this embodiment, the control unit 61 rotates the second support unit 12 to the machining area and performs measurement on measurement points 12f and 12g on the second support unit 12 located in the machining area using a measuring tool 4c provided below the spindle 4a. In this embodiment, the measurement points 12f and 12g are, for example, measuring pins of different heights, and the measuring tool 4c is, for example, a contact probe, but is not limited thereto. FIGS. 6A and 6B illustrate the measurement process performed on measurement points 12f and 12g at a first time point when the machine tool has just been started, and FIGS. 6C and 6D illustrate the measurement process performed on measurement points 12f and 12g at a second time point after the machine tool has been operating for a predetermined time.

[0055] In FIG. 6A, the control unit 61 controls the Y-axis motor 83 to drive the linear axis 7, thereby moving the spindle 4a, which is supported by the base 10 and the column 2, in the Y-axis direction relative to the second support 12 located on the rotary table 8. When the measuring tool 4c provided below the spindle 4a measures the measurement point 12f, a signal indicating that the measurement point 12f has been detected is output to the control unit 61. When this signal is input, the control unit 61 stores the measurement result of the encoder 83a of the Y-axis motor 83 (the drive amount is −16.3) in the memory unit 63 and outputs a stop signal to the Y-axis motor 83. The measurement result of the encoder 83a indicates the longitudinal position of the spindle 4a. In other words, the longitudinal position of the spindle 4a is measured by the measuring tool 4c, the control unit 61, and the encoder 83a.

[0056] 6B, control unit 61 controls Y-axis motor 83 to drive linear axis 7, and moves main shaft 4a, which is supported by base 10 and column 2, in the Y-axis direction relative to second support unit 12, which is positioned on rotary table 8. When measuring tool 4c, which is provided below main shaft 4a, measures measurement point 12g, a signal indicating that measurement point 12g has been detected is output to control unit 61. When this signal is input, control unit 61 stores the measurement result of encoder 83a of Y-axis motor 83 (drive amount is -93.5) in memory unit 63, and outputs a stop signal to Y-axis motor 83.

[0057] As shown in FIGS. 6C and 6D, when the machine tool operates for a predetermined time, the linear axis 7 undergoes linear expansion due to the influence of heat from the Y-axis motor 83, the bearings 7a and 7b, and the ball screw / nut.

[0058] 6C, the control unit 61 controls the Y-axis motor 83 to drive the linear axis 7' after thermal expansion, and moves the main shaft 4a supported by the base 10 and the column 2 in the Y-axis direction relative to the second support unit 12 positioned on the rotary table 8. When the measuring tool 4c provided below the main shaft 4a detects the measurement point 12f, a signal indicating that the measurement point 12f has been detected is output to the control unit 61. When this signal is input, the control unit 61 stores the measurement result of the encoder 83a of the Y-axis motor 83 (the drive amount is -12.7) in the memory unit 63, and outputs a stop signal to the Y-axis motor 83.

[0059] 6D, control unit 61 controls Y-axis motor 83 to drive linear shaft 7' after thermal expansion and move it in the Y-axis direction relative to second support part 12 positioned on rotary table 8. When measuring tool 4c provided below main shaft 4a detects measurement point 12g, a signal indicating that measurement point 12g has been detected is output to control unit 61. When this signal is input, control unit 61 stores the detection result of encoder 83a of Y-axis motor 83 (drive amount is -79.7) in memory unit 63, and outputs a stop signal to Y-axis motor 83.

[0060] Based on the measurement results obtained by performing a measurement process on measurement points 12f and 12g at the first time point and the measurement results obtained by performing a measurement process on measurement points 12f and 12g at the second time point, the control unit 61 can correct the drive amount of the drive member by linear interpolation.

[0061] In particular, Figures 7A and 7B are schematic illustrations of performing a correction process according to one embodiment of the present invention.

[0062] In this embodiment, the thermal displacement of the linear axis 7 occurs due to the elongation of the ball screw, and the amount of this displacement increases as it moves away from the fixed-end bearing (bearing 7a in Figure 7B).Based on this, the relationship between the thermal displacement of the linear axis 7 and the position of the base part 10 can be corrected by measuring the position changes of any two measurement points and approximating them with a linear function.

[0063] Fig. 7A is a schematic diagram showing the calculation of a correction line based on the measurement results obtained by measuring measurement points 12f and 12g on second support part 12 in Fig. 6A to Fig. 6D. In Fig. 7A, control unit 61 calculates, for example, the difference (position change) between the measurement results obtained by performing measurement processing on measurement point 12f at a first time point and a second time point, calculates the difference (position change) between the measurement results obtained by performing measurement processing on measurement point 12g at the first time point and a second time point, and approximates these two differences with a linear function, thereby determining a correction line in which the correction value changes according to the Y-axis coordinate.

[0064] FIG. 7B is a schematic diagram in which the correction line calculated in FIG. 7A (based on the measurement results of the second support portion 12) is applied to correcting the machining position of the workpiece W at the first support portion 11. In FIG. 7B, when machining position wp3 on the workpiece W with the tool 4b, the drive amount of the Y-axis motor 83 is originally -55. Substituting this drive amount into the correction line (linear function) in FIG. 7B, a corresponding correction value of 8.7 is obtained. Therefore, by correcting the drive amount of the Y-axis motor 83 by 8.7 (the drive amount after correction is -46.3), the machine tool can still machine position wp3 on the workpiece W with the tool 4b even when thermal displacement occurs in the linear axis 7.

[0065] In some embodiments, the control unit 61 may perform measurement processing of measurement points located on the first support part 11 and the second support part 12, respectively, and perform corresponding correction processing, thereby processing the workpiece based on the latest correction results.

[0066] In detail, FIG. 8 is a flowchart of a method for numerically controlling a machine tool according to one embodiment of the present invention.

[0067] In step S802, the numerical control device 60 causes the control unit 61 to execute a first measurement process for measuring a measurement point located on one of the first support 11 and the second support 12.

[0068] In step S804, the control unit 61 executes a first correction process to correct the drive amount of the drive member based on the measurement results obtained in the first measurement process.

[0069] Since the above steps S802 and S804 are the same as or similar to steps S402 and S404 in the previous embodiment, detailed implementation methods thereof will be omitted.

[0070] The difference between this embodiment and the previous embodiment is that in step S806, the control unit 61 further executes a second measurement process to measure a measurement point located on the other of the first support unit 11 and the second support unit 12. In step S808, the control unit 61 further executes a second correction process to correct the drive amount of the drive member based on the measurement result obtained in the second measurement process.

[0071] In some embodiments, the control unit 61 measures at least two measurement points located on one of the first support 11 and the second support 12 in the first measurement process, and measures at least two measurement points located on the other of the first support 11 and the second support 12 in the second measurement process. Based on the measurement results of the at least two measurement points obtained in the first measurement process and the second measurement process, the control unit 61 corrects the drive amount of the drive member by linear interpolation in the first correction process and the second correction process. Specifically, because the thermal displacement of the linear axis differs between the free end side and the fixed end side, the desired accuracy can be achieved by measuring at two positions (the free end side and the fixed end side). Here, when measuring at two positions, correction can be performed by linear interpolation to calculate the estimated position of the measurement point.

[0072] In some embodiments, the control unit 61 outputs a screen to a display (not shown) via the output interface 65, and displays a history confirmation screen on the display showing the history of the measurement results obtained in the first measurement process and the second measurement process, and the history confirmation screen clearly displays whether the measurement was made using the first support unit 11 or the second support unit 12.

[0073] For example, FIG. 9 is a schematic diagram of a history confirmation screen 90 according to an embodiment of the present invention. The history confirmation screen 90 displays measurement results in chronological order (from newest to oldest) based on the correction time. This includes actual measurement results obtained by performing measurement processing on measurement points 1 and 2 on the first support unit 11 and the second support unit 12, estimated results calculated by linear interpolation, and the origin position calculated based on these measurement results. In this embodiment, the control unit 61 may display a "*" next to the actual measurement results. In other embodiments, the control unit 61 may distinguish between actual measurement results and estimated results by changing the text color or background color of the actual measurement results or estimated results. This helps the operator distinguish between the measurement results.

[0074] Finally, in step S810, the control unit 61 executes a processing process for processing the workpiece based on the latest correction result out of the correction results obtained in the first correction process and the second correction process.

[0075] This allows the control unit 61 to arbitrarily select whether to perform measurement processing and correction processing on the measurement points on the first support part 11 or the second support part 12 during the processing step, and by performing processing based on the latest correction results, the processing accuracy can be made more stable.

[0076] In some embodiments, the control unit 61 performs a first measurement process and a first correction process on the second support unit 12 located in the non-machining area, and performs a second measurement process and a second correction process on the first support unit 11 located in the machining area. In some embodiments, the control unit 61 performs a first measurement process and a first correction process on the second support unit 12 located in the machining area, then rotates the first support unit 11 to the machining area, and then performs a second measurement process and a second correction process on the first support unit 11 located in the machining area. This embodiment does not limit the method of performing the first correction process and the second correction process.

[0077] In some embodiments, the control unit 61 may further perform a measurement time determination process and determine the next measurement time based on the measurement results obtained in the first measurement process and the measurement results obtained in the second measurement process.

[0078] In more detail, to avoid deterioration of the cycle time due to actual measurements, if the displacement change is small, the actual measurements are automatically thinned out (reduced), thereby reducing the deterioration of the cycle time. The control unit 61 can know the slope of the displacement change based on the measurement results obtained from the two measurement processes. As a result, if the slope of the displacement change is small, the deterioration of the cycle time can be reduced by lengthening the time for the next measurement (reducing the number of actual measurements). Conversely, if the slope of the displacement change is large, the processing accuracy can be improved by shortening the time for the next measurement.

[0079] In some embodiments, for example, the control unit 61 determines whether or not to issue an execution command at each reference time, and updates this reference time based on the measurement result.

[0080] In particular, FIG. 10 is a flowchart of a method for updating a reference time used in performing a measurement process according to one embodiment of the present invention.

[0081] In step S1002, the numerical control device 60, via the control unit 61, executes a determination process each time the first measurement process or the second measurement process is completed to determine whether the elapsed time from the time the first measurement process or the second measurement process is completed is equal to or greater than a reference time.

[0082] If the control unit 61 determines in the determination process that the elapsed time is equal to or greater than the reference time (S1002: YES), the control unit 61 may determine that position measurement of the measurement point is necessary. Therefore, in step S1004, the control unit 61 executes an execution command transmission process to transmit an execution command for the first measurement process or the second measurement process. Conversely, if the control unit 61 determines in the determination process that the elapsed time does not exceed the reference time (S1002: NO), the control unit 61 may determine that position measurement of the measurement point is unnecessary. Therefore, in step S1006, the control unit 61 executes an execution command deletion process to delete the execution command for the first measurement process or the second measurement process. Note that deleting an execution command is not limited to deleting the command itself, but also includes a method of omitting (skipping) the command itself. That is, if the control unit 61 determines in the determination process that the elapsed time is less than the reference time, the control unit 61 may delete the generated execution command for the first measurement process or the second measurement process, or may omit (skip) the generated execution command for the first measurement process or the second measurement process. In addition, in other embodiments of the present invention not shown, if the judgment process determines that the elapsed time is less than the reference time, the control unit 61 may not generate an execution command for the first measurement process or the second measurement process.

[0083] In step S1008, the control unit 61 executes an update time determination process to determine an update time based on the measurement results obtained in the first measurement process and the measurement results obtained in the second measurement process. Here, the control unit 61 executes the update time determination process, for example, when a predetermined time has elapsed since the first measurement process was executed, or when the number of measurement processes exceeds a predetermined number, but is not limited to this.

[0084] In step S1010, the control unit 61 executes an update process for updating the reference time based on the update time determined in the update time determination process.

[0085] In some embodiments, in the update time determination process, the control unit 61 determines the update time based on the difference between the positions of the measurement points measured in the first measurement process and the second measurement process and the estimated positions of the measurement points in the first measurement process and the second measurement process estimated from the positions of the measurement points measured in the first measurement process and the second measurement process relative to the elapsed time.

[0086] In some embodiments, the control unit 61 determines the update time in the update time determination process based on the value of the maximum value among multiple differences between the position of the measurement point measured in the first measurement process and the second measurement process and the estimated position over the elapsed time.

[0087] By way of example, FIG. 11 is a schematic diagram of update time determination according to one embodiment of the present invention.

[0088] At the i-1th time point, the control unit 61 issues a command to execute the first measurement process, and executes the measurement process for the measurement points p1 and p2 on the first support unit i-1.

[0089] After time point i-1, at time point i when the cumulative time reaches the elapsed time, control unit 61 issues a command to execute the second measurement process and executes the measurement process for measurement points p1 and p2 on second support unit i. Note that in the above-described embodiment, the first time point is immediately after the machine tool is started up, and the second time point is after a predetermined time has elapsed, but in this embodiment, time point i-1 may be any time point after the machine tool is started up and is not limited to immediately after the machine tool is started up, and time point i refers to a time point after a predetermined time has elapsed after time point i-1.

[0090] Here, the control unit 61 determines the positions X of the measurement points p1 and p2 on the first support i-1 measured in the first measurement process. i-1,p1,P1 , X i-1,p2,P1 Based on this, the estimated positions X' of the measurement points p1 and p2 in the second measurement process are calculated. i-1,p1,P2 , X' i-1,p2,P2 Furthermore, the control unit 61 estimates the positions X i,p1,P1 , X i,p2,P1 Based on this, the estimated positions X' of the measurement points p1 and p2 in the second measurement process are calculated. i,p1,P1 , X' i,p2,P1 In this way, the control unit 61 determines the update time based on the difference between the position of the measurement point and the estimated position. Here, the control unit 61 determines the update time based on, for example, the value of the elapsed time K xi The maximum value of the difference between the position at the measurement point and the estimated position (i.e., the slope of the position change amount) is used to calculate the update time t nx The formula is as follows:

number

[0091] 12A and 12B are schematic diagrams of issuing / deleting execution commands according to one embodiment of the present invention. This embodiment describes how the measurement interval is used to set the target accuracy. Here, the dashed line represents the actual displacement at a measurement point on the linear axis, and the solid line represents the correction amount for the drive member. The numerical controller is initially configured to issue an execution command M358 for a measurement process (first measurement process or second measurement process) once every predetermined time interval, for example.

[0092] 12A, the numerical control device sets, for example, a maximum correction interval Tmax, and executes an execution command deletion process at the maximum correction interval Tmax each time a measurement process is completed, thereby deleting the measurement process execution command M358 to be issued. Only after the maximum correction interval Tmax has been exceeded does the numerical control device execute an execution command transmission process and issue the measurement process execution command M358. Here, the smaller the value of the maximum correction interval Tmax set, the more measurements are taken, thereby improving machining accuracy. Conversely, the larger the value of the maximum correction interval Tmax set, the fewer measurements are taken, thereby improving productivity.

[0093] When the operation of the machine tool is stopped, the thermal displacement of the linear axis gradually decreases, so it is necessary to reconsider the time point at which the execution command for measurement processing can be issued. In Fig. 12B, the machine tool stops operation in the section from time t1 to t2. Here, the numerical control device, for example, sets a re-measurement interval Tr at time t1 when the machine tool stops operation, and if the re-measurement interval Tr is continuously exceeded while the operation is stopped, it determines that position measurement must be performed for the measurement point and issues the execution command M358 for measurement processing at the next time when the execution command M358 for measurement processing should be issued.

[0094] In summary, in a machine tool numerical control device and numerical control method according to one embodiment of the present invention, in a rotary table-type machine tool having two support parts, the effects of thermal displacement due to thermal expansion of a linear axis can be eliminated by measuring the measurement point of one of the support parts, performing correction based on the measurement results, and applying the correction results to the machining process of the other support part. Furthermore, by separately correcting the two support parts and performing machining based on the most recent correction results, machining accuracy can be made more stable. Furthermore, by determining the next measurement time based on measurement results obtained from multiple measurement processes, deterioration of cycle time due to actual measurement can be avoided.

[0095] Finally, the above embodiments are only used to describe the technical solutions of the present invention, and are not intended to limit the same. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art will understand that the technical solutions described in the above embodiments can be modified or some or all of the technical features can be replaced with equivalents. Furthermore, such modifications or replacements do not cause the essence of the corresponding technical solutions to depart from the scope of the technical solutions of the embodiments of the present invention. [Explanation of symbols]

[0096] 1: Bass 2: Column 4: Spindle head 4a: Main axis 4b:Tools 4c: Measuring tool 6: Main shaft motor 6e, 11e, 12e, 81e, 82e, 83e, 84e: Encoders 7, 7': Linear axis 7a, 7b: Bearings 8: Rotating table 8a: Rotation axis 10: Base 11, i-1: 1st support part 11a, 12a: A-axis motor 11b, 12b: Support part 11c, 12c: Rotating support base 11d, 12d: Clamp section 12, i: Second support part 12f, 12g, p1, p2: Measurement point 60: Numerical control device 61: Control unit 62:RAM 63: Storage section 64: Input interface 65: Output interface 71: Input device 81: Z-axis motor 82: X-axis motor 83: Y-axis motor 84: Rotary table motor 90: History confirmation screen L: Boundary line wp1, wp2, wp3: Machining position W, W': Work S402-S406, S802-S810, S1002-S1010: Steps t1, t2: time points Tmax: Maximum correction interval Tr: Remeasurement interval X i,p1,P1 , X i,p2,P1 , X i-1,p1,P1 , X i-1,p2,P1 : Measurement point position X' i,p1,P1 , X' i,p2,P1 , X' i-1,p1,P2 , X' i-1,p2,P2 : Estimated position of the measurement point

Claims

1. a rotary table having a first support portion and a second support portion for supporting a workpiece, the rotary table being rotatable about a rotation axis between a first state in which the first support portion is located in a machining area and the second support portion is located in a non-machining area, and a second state in which the first support portion is located in the non-machining area and the second support portion is located in the machining area; a spindle capable of holding a tool and machining a workpiece supported by the first support portion and the second support portion with the tool; a linear axis for relatively moving the rotary table and the main shaft; a driving member that drives the linear shaft; A numerical control device for a machine tool comprising: a first measurement process for measuring a measurement point located on one of the first support portion and the second support portion; a first correction process for correcting a drive amount of the drive member based on the measurement result obtained in the first measurement process; a machining process for machining a workpiece at the other of the first support unit and the second support unit based on a correction result obtained by the first correction process; A numerical control device characterized by being able to execute the above.

2. a second measurement process for measuring a measurement point located on the other of the first support portion and the second support portion; a second correction process for correcting the drive amount of the drive member based on the measurement result obtained in the second measurement process; It is further possible to 2. The numerical control device according to claim 1, wherein the machining process performs machining of the workpiece based on the latest correction result obtained in the first correction process and the second correction process.

3. a measurement time determination process for determining a next measurement time based on the measurement results obtained in the first measurement process and the measurement results obtained in the second measurement process; The numerical control device according to claim 2, further comprising:

4. a determination process of determining whether or not an elapsed time from the time point when the first measurement process or the second measurement process is completed is equal to or longer than a reference time; an execution command issuing process of issuing an execution command for the first measurement process or the second measurement process when it is determined in the determination process that the elapsed time is equal to or longer than the reference time; an update time determination process for determining an update time based on the measurement results obtained in the first measurement process and the measurement results obtained in the second measurement process; an update process for updating the reference time based on the update time determined in the update time determination process; 3. The numerical control device according to claim 2, further comprising:

5. 5. The numerical control device according to claim 4, wherein in the update time determination process, the update time is determined based on a difference between a position of the measurement point measured in the first measurement process and the second measurement process and an estimated position of the measurement point in the first measurement process and the second measurement process that is estimated from the position of the measurement point measured in the first measurement process and the second measurement process, with respect to the elapsed time.

6. 6. The numerical control device according to claim 5, wherein in the update time determination process, the update time is determined based on a value of a maximum value of a plurality of differences between the positions of the measurement points measured in the first measurement process and the second measurement process and the estimated position, with respect to the elapsed time.

7. an execution command deletion process of deleting an execution command for the first measurement process or the second measurement process when it is determined in the determination process that the elapsed time is less than the reference time; 5. The numerical control device according to claim 4, further comprising:

8. the first measurement process measures at least two measurement points located on one of the first support portion and the second support portion, the second measurement process measures at least two measurement points located on the other of the first support portion and the second support portion, 3. The numerical control device according to claim 2, wherein the first correction process and the second correction process correct the drive amount of the drive member by linear interpolation based on the measurement results of each of the at least two measurement points obtained in the first measurement process and the second measurement process.

9. 3. The numerical control device according to claim 2, characterized in that, on a history confirmation screen that displays a history of measurement results obtained in the first measurement process and the second measurement process, it is displayed in a recognizable manner whether the measurement was made at the first support unit or the second support unit.

10. the linear axes are a first axis, a second axis, and a third axis that are perpendicular to each other; The machine tool comprises: With the base, a column supporting the main shaft so that the main shaft is movable along the third axis; a base portion provided on the base and supporting the column so that the column is movable about the first axis and the second axis; Further provided with 2. The numerical control device according to claim 1, wherein the rotary table is provided on the base so as to be rotatable about the rotation axis.

11. The numerical control device according to claim 1 , wherein the first measurement process measures the measurement point using a measuring tool attached to the spindle.

12. a rotary table having a first support portion and a second support portion for supporting a workpiece, the rotary table being rotatable about a rotation axis between a first state in which the first support portion is located in a machining area and the second support portion is located in a non-machining area, and a second state in which the first support portion is located in the non-machining area and the second support portion is located in the machining area; a spindle capable of holding a tool and machining a workpiece supported by the first support portion and the second support portion with the tool; a linear axis for relatively moving the rotary table and the main shaft; a driving member that drives the linear shaft; A numerical control method for a machine tool comprising: executing a first measurement process for measuring a measurement point located on one of the first support portion and the second support portion; executing a first correction process for correcting a drive amount of the drive member based on the measurement result obtained in the first measurement process; performing a machining process for machining a workpiece at the other of the first support unit and the second support unit based on a correction result obtained by the first correction process; A numerical control method comprising:

13. performing a second measurement process for measuring a measurement point located on the other of the first support portion and the second support portion; executing a second correction process for correcting a drive amount of the drive member based on the measurement result obtained in the second measurement process; Further comprising:

13. The numerical control method according to claim 12, wherein the machining process executes machining of the workpiece based on the latest compensation result among the compensation results obtained in the first compensation process and the second compensation process.

14. determining a next measurement time based on the measurement results obtained in the first measurement process and the measurement results obtained in the second measurement process; The numerical control method according to claim 13, further comprising:

15. determining whether or not an elapsed time from the time point when the first measurement process or the second measurement process is completed is equal to or longer than a reference time; issuing a command to execute the first measurement process or the second measurement process when it is determined that the elapsed time is equal to or longer than the reference time; determining an update time based on the measurement results obtained in the first measurement process and the measurement results obtained in the second measurement process; updating the reference time based on the determined update time; The numerical control method according to claim 13, further comprising:

16. 16. The numerical control method according to claim 15, wherein when determining the update time, the update time is determined based on a difference between a position of the measurement point measured in the first measurement process and the second measurement process and an estimated position of the measurement point in the first measurement process and the second measurement process estimated from the position of the measurement point measured in the first measurement process and the second measurement process, with respect to the elapsed time.

17. 17. The numerical control method according to claim 16, wherein when determining the update time, the update time is determined based on a maximum value of a plurality of differences between the positions of the measurement points measured in the first measurement process and the second measurement process and the estimated position, with respect to the elapsed time.

18. When it is determined that the elapsed time is less than the reference time, deleting the execution command of the first measurement process or the second measurement process; The numerical control method according to claim 15, further comprising:

19. the first measurement process measures at least two measurement points located on one of the first support portion and the second support portion, the second measurement process measures at least two measurement points located on the other of the first support portion and the second support portion, 14. The numerical control method according to claim 13, wherein the first correction process and the second correction process correct the drive amount of the drive member by linear interpolation based on the measurement results of the at least two measurement points obtained in the first measurement process and the second measurement process.

20. A history confirmation screen displays a history of the measurement results obtained in the first measurement process and the second measurement process, and displays whether the measurement was made using the first support unit or the second support unit in a recognizable manner. The numerical control method according to claim 13, further comprising:

21. the linear axes are a first axis, a second axis, and a third axis that are perpendicular to each other; The machine tool comprises: With the base, a column supporting the main shaft so that the main shaft is movable along the third axis; a base portion provided on the base and supporting the column so that the column is movable about the first axis and the second axis; Further provided with The rotary table is provided on the base so as to be rotatable about the rotation axis.

13. The numerical control method according to claim 12.

22. 13. The numerical control method according to claim 12, wherein the first measurement process measures the measurement point using a measuring tool attached to the spindle.

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