Numerical controller, control method, and storage medium

Abstract

The invention provides a numerical controller, a control method, and a storage medium. A numerical controller that controls a machine tool having a tool shaft and a workpiece shaft includes: a synchronization control unit that synchronously rotates the tool shaft and the workpiece shaft; and a phase control unit that performs phase matching of the rotation phase angles of the tool shaft and the workpiece shaft on the basis of the rotation phase angles of the tool shaft and the workpiece shaft during the synchronous rotation of the tool shaft and the workpiece shaft. The phase control unit includes: a tool axis phase angle setting unit that sets a set tool angle, which is a rotation phase angle of the tool axis at the end of phase matching; and a workpiece shaft phase angle setting unit that sets a set workpiece angle, which is a rotation phase angle of the workpiece shaft at the end of phase matching. Phase matching is performed by relatively controlling the rotation speeds of the tool shaft and the workpiece shaft so that the rotation phase angle of the tool shaft becomes a set tool angle and the rotation phase angle of the workpiece shaft becomes a set workpiece angle when the phase matching of the tool shaft and the workpiece shaft is completed.

Description

Technical Field

[0001] The present invention relates to a numerical control device, a control method, and a storage medium. Background Art

[0002] The numerical control device described in Patent Document 1 performs machining by controlling the synchronous rotation of a workpiece axis on which a workpiece having a gear to be machined is mounted and a tool axis on which a cutting tool is mounted. The numerical control device adds or subtracts the amount of movement of the phase difference between the workpiece axis and the tool axis to the amount of movement of the workpiece axis to perform a phase matching operation for matching the phase of the workpiece axis with the phase of the tool axis. Thereby, the numerical control device opposes the teeth of the workpiece to the blade grooves of the tool to machine the gear.

[0003] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2005-115433 Summary of the Invention

[0004] In Patent Document 1, although the relative phase difference between the tool axis and the workpiece axis is corrected, the rotation phase angles of the tool axis and the workpiece axis at the start of machining cannot be set. Therefore, there is a problem that it is difficult to manage the wear of the tool blade.

[0005] An object of the present invention is to provide a numerical control device, a control method, a program, and a storage medium capable of setting the rotation phase angles of a tool axis and a workpiece axis in machining performed by the synchronous rotation of the tool axis and the workpiece axis.

[0006] A first aspect of the present invention provides a numerical control device for controlling a machine tool having a tool axis on which a tool is mounted and a workpiece axis for rotating a table on which a workpiece is fixed to machine the workpiece, including: a synchronization control unit configured to perform control for synchronously rotating the tool axis and the workpiece axis; and a phase control unit configured to perform phase matching of the rotation phase angles of the tool axis and the workpiece axis based on the rotation phase angle of the tool axis and the rotation phase angle of the workpiece axis during the synchronous rotation of the tool axis and the workpiece axis performed by the synchronization control unit, the phase control unit including: a tool axis phase angle setting unit configured to set a set tool angle, which is the rotation phase angle of the tool axis at the end of the phase matching; and a workpiece axis phase angle setting unit configured to set a set workpiece angle, which is the rotation phase angle of the workpiece axis at the end of the phase matching, and perform the phase matching by relatively controlling the rotation speed of the tool axis and the rotation speed of the workpiece axis, so that the rotation phase angle of the tool axis at the end of the phase matching between the tool axis and the workpiece axis becomes the set tool angle and the rotation phase angle of the workpiece axis becomes the set workpiece angle.

[0007] The numerical control device controls the synchronous rotation of the tool axis and the workpiece axis to machine the workpiece. When the phases of the tool axis and the workpiece axis are matched, the numerical control device can set the respective rotation phase angles of the tool axis and the workpiece axis at the end of the phase matching, that is, the set tool angle and the set workpiece angle. Therefore, when starting to machine the workpiece with the tool, the numerical control device can control the cutting edge of the tool in contact with the workpiece and can suppress the wear of the cutting edge of the tool.

[0008] In the numerical control device of the present invention, the machine tool includes a feed axis for relatively moving the tool axis and the workpiece axis, and the phase control unit includes a feed control unit for controlling the drive of the feed axis. When the rotation phase angle of the tool axis becomes the set tool angle and the rotation phase angle of the workpiece axis becomes the set workpiece angle, the feed control unit drives the feed axis to start the relative movement of the tool axis and the workpiece axis to the position where the tool machines the workpiece. Since the numerical control device starts the drive of the feed axis at the end of the phase matching, the timing of the contact between the tool and the workpiece can be kept constant for each machining.

[0009] In the numerical control device of the present invention, the numerical control device starts the operation of the phase matching according to a phase command, which is a command for instructing the operation of the phase matching between the tool axis and the workpiece axis. The tool axis phase angle setting unit sets the set tool angle based on a tool setting angle designation variable in the phase command for designating the set tool angle, and the workpiece axis phase angle setting unit sets the set workpiece angle based on a workpiece setting angle designation variable in the phase command for designating the set workpiece angle. Since the numerical control device designates the set tool angle and the set workpiece angle as variables in the phase command, the user does not need to perform the operation of setting the set tool angle and the set workpiece angle in advance before executing the phase matching operation.

[0010] The numerical control device of the present invention, wherein the phase control unit includes: a start workpiece angle calculation unit for calculating a start workpiece angle based on the set workpiece angle, the workpiece axis synchronization speed, and the phase matching time, where the workpiece axis synchronization speed is the rotational speed during machining of the workpiece axis controlled by the synchronization control unit, the phase matching time is the preset time required for phase matching, and the start workpiece angle is the rotational phase angle of the workpiece axis at the start of phase matching; a start tool angle calculation unit for calculating a start tool angle, where the start tool angle is the rotational phase angle of the tool axis when the workpiece axis reaches the start workpiece angle; an end tool angle calculation unit for calculating an end tool angle based on the start tool angle, the tool axis synchronization speed, and the phase matching time, where the tool axis synchronization speed is the rotational speed during machining of the tool axis controlled by the synchronization control unit, and the end tool angle is the rotational phase angle reached by the tool axis after passing through the phase matching time from the start tool angle; a correction amount calculation unit for calculating the difference between the set tool angle and the end tool angle as the correction amount; and a tool speed control unit for controlling the rotational speed of the tool axis based on the correction amount, so that the tool axis reaches the set tool angle after passing through the phase matching time from the start tool angle. The torque required for the rotation of the tool axis is smaller than the torque required for the rotation of the workpiece axis. Therefore, by correcting the end tool angle of the tool axis to the set tool angle, the numerical control device can smoothly perform the phase matching between the tool axis and the workpiece axis.

[0011] The numerical control device of the present invention, wherein the machine tool includes a display device for displaying information, and the synchronization control unit includes a notification unit for displaying a notification screen on the display device, and the notification screen is used to notify that the tool axis and the workpiece axis are in synchronous rotation. The numerical control device can notify the user that the tool axis and the workpiece axis are in synchronous rotation through the notification screen displayed on the display device.

[0012] The numerical control device of the present invention, wherein the phase control unit includes a tool angle shift unit for changing the set tool angle based on the number of cutting edges of the tool, and each time the tool performs one or more machining operations on the workpiece, the tool angle shift unit changes the set tool angle. By changing the set tool angle each time the tool performs one or more machining operations on the workpiece, the numerical control device can stagger the cutting edges that first contact the workpiece during machining in sequence, and can suppress tool wear.

[0013] The workpiece of the numerical control device of the present invention is a machined gear. The numerical control device can perform machining on the machined gear through the synchronous rotation of the tool axis and the workpiece axis.

[0014] A second aspect of the present invention provides a control method for a numerical control device, the numerical control device being used to control a machine tool having a tool axis for mounting a tool and a workpiece axis for rotating a table for fixing a workpiece, so as to perform machining of the workpiece. The control method includes: a synchronization control step for performing control to synchronously rotate the tool axis and the workpiece axis; and a phase control step for performing phase matching of the rotation phase angles of the tool axis and the workpiece axis based on the rotation phase angle of the tool axis and the rotation phase angle of the workpiece axis during the synchronous rotation of the tool axis and the workpiece axis performed in the synchronization control step. The phase control step includes: a tool axis phase angle setting step for setting a set tool angle, the set tool angle being the rotation phase angle of the tool axis when the phase matching ends; and a workpiece axis phase angle setting step for setting a set workpiece angle, the set workpiece angle being the rotation phase angle of the workpiece axis when the phase matching ends. The phase matching is performed by relatively controlling the rotation speed of the tool axis and the rotation speed of the workpiece axis, so that the rotation phase angle of the tool axis when the phase matching of the tool axis and the workpiece axis ends becomes the set tool angle and the rotation phase angle of the workpiece axis becomes the set workpiece angle. Therefore, the same effects as those of the first aspect of the present invention can be achieved.

[0015] A third aspect of the present invention provides a program for controlling a numerical control device, the numerical control device being used to control a machine tool having a tool axis for mounting a tool and a workpiece axis for rotating a table for fixing a workpiece, so as to perform machining of the workpiece. The program is executed on a computer: a synchronization control step for performing control to synchronously rotate the tool axis and the workpiece axis; and a phase control step for performing phase matching of the rotation phase angles of the tool axis and the workpiece axis based on the rotation phase angle of the tool axis and the rotation phase angle of the workpiece axis during the synchronous rotation of the tool axis and the workpiece axis performed in the synchronization control step. In the phase control step, a tool axis phase angle setting step for setting a set tool angle, the set tool angle being the rotation phase angle of the tool axis when the phase matching ends; and a workpiece axis phase angle setting step for setting a set workpiece angle, the set workpiece angle being the rotation phase angle of the workpiece axis when the phase matching ends are executed. The phase matching is performed by relatively controlling the rotation speed of the tool axis and the rotation speed of the workpiece axis, so that the rotation phase angle of the tool axis when the phase matching of the tool axis and the workpiece axis ends becomes the set tool angle and the rotation phase angle of the workpiece axis becomes the set workpiece angle. Therefore, the same effects as those of the first aspect of the present invention can be achieved.

[0016] A fourth aspect of the present invention provides a storage medium storing a program for controlling a numerical control device that controls a machine tool having a tool axis on which a tool is mounted and a workpiece axis that rotates a table for fixing a workpiece, thereby machining the workpiece. The program is executed on a computer: a synchronization control step for performing control to synchronously rotate the tool axis and the workpiece axis; and a phase control step for performing phase matching of the rotation phase angles of the tool axis and the workpiece axis based on the rotation phase angle of the tool axis and the rotation phase angle of the workpiece axis during the synchronous rotation of the tool axis and the workpiece axis performed in the synchronization control step. In the phase control step, the following steps are executed: a tool axis phase angle setting step for setting a set tool angle, which is the rotation phase angle of the tool axis at the end of the phase matching; and a workpiece axis phase angle setting step for setting a set workpiece angle, which is the rotation phase angle of the workpiece axis at the end of the phase matching. The phase matching is performed by relatively controlling the rotation speed of the tool axis and the rotation speed of the workpiece axis, so that the rotation phase angle of the tool axis at the end of the phase matching between the tool axis and the workpiece axis becomes the set tool angle and the rotation phase angle of the workpiece axis becomes the set workpiece angle. Therefore, the same effect as the first aspect of the present invention can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a perspective view of the machine tool 1.

[0018] Figure 2 is a front view of the machine tool 1.

[0019] Figure 3 is a block diagram showing the electrical structure of the machine tool 1.

[0020] Figure 4 is a view showing the cutting edge contact position of the cutting edge B1 of the tool D with respect to the workpiece W.

[0021] Figure 5 is a view showing a state in which the cutting edge contact position with the workpiece W is sequentially shifted to P1 to P4.

[0022] Figure 6 is a timing chart showing an example of phase matching control.

[0023] Figure 7 is a timing chart comparing the phase and rotation speed of the tool axis 8.

[0024] Figure 8 is a timing chart for explaining the phase correction of the tool axis 8.

[0025] Figure 9It is a timing chart for explaining a method of generating a correction speed of a tool axis 8.

[0026] Figure 10 It is a diagram showing a part of an NC program 100.

[0027] Figure 11 It is a flowchart of a phase matching control process.

[0028] Figure 12 It is a diagram showing a display example of a display unit 29.

[0029] Figure 13 It is a diagram showing a modified example. Detailed implementation mode

[0030] An embodiment of the present invention will be described. In the following description, left and right, front and back, and up and down as indicated by the arrows in the figures are used. The left - right direction, front - back direction, and up - down direction of the machine tool 1 are the X - axis direction, Y - axis direction, and Z - axis direction, respectively.

[0031] Figure 1 The shown machine tool 1 is a composite machining machine. In addition to being able to perform rotational machining and turning machining on a workpiece W (workpiece), the machine tool 1 can also perform two - axis synchronous machining. Rotational machining is a machining method in which a tool D rotates and contacts the workpiece W to cut the workpiece W. Turning machining is a machining method in which the workpiece W rotates and contacts the stationary tool D to axially symmetrically cut the workpiece W. Two - axis synchronous machining is a machining method in which the tool D and the workpiece W are rotated simultaneously by driving two axes, namely, the tool axis 8 and the workpiece axis 82 described later, to cut the workpiece W. The processed product of the workpiece W in this embodiment is, for example, a gear, and the tool D is, for example, a gear cutting tool.

[0032] Refer to Figure 1 、 Figure 2 to describe the structure of the machine tool 1. The machine tool 1 has a base portion 2, a transfer body 12, a column 5, a spindle head 7, a tool axis 8 (refer to Figure 2 ), a workpiece holding device 80, an automatic tool changer 30 (hereinafter referred to as ATC 30), etc.

[0033] The base portion 2 is a rectangular box - shaped iron member with its long side in the Y - axis direction. The base portion 2 has a pedestal portion 4 on the rear side of its upper surface, a left front pedestal portion 18 on the left front side of its upper surface, and a right front pedestal portion 19 on the right front side of its upper surface. The pedestal portion 4 has a pair of Y - axis guide rails 61, 62, a Y - axis ball screw 63 (refer to Figure 2 ), a Y - axis motor 52 (refer to Figure 3 ) etc. on its upper surface. The Y - axis guide rails 61, 62 and the Y - axis ball screw 63 extend in the Y - axis direction. The Y - axis ball screw 63 is disposed between the Y - axis guide rails 61, 62.

[0034] The transfer body 12 is arranged on the pedestal portion 4 and can move along the Y-axis guide rails 61 and 62. The transfer body 12 has a nut (not shown) on its lower surface. This nut is screwed onto the Y-axis ball screw 63. The Y-axis motor 52 rotates the Y-axis ball screw 63. The transfer body 12 moves in the Y-axis direction together with the nut. The transfer body 12 has a pair of X-axis guide rails 71 and 72, an X-axis ball screw 73, an X-axis motor 51, etc. on its upper surface. The X-axis guide rails 71 and 72 and the X-axis ball screw 73 extend in the X-axis direction. The X-axis ball screw 73 is arranged between the X-axis guide rails 71 and 72.

[0035] The column 5 is arranged on the transfer body 12 and can move along the X-axis guide rails 71 and 72. The column 5 has a nut (not shown) on its lower surface. This nut is screwed onto the X-axis ball screw 73. The X-axis motor 51 rotates the X-axis ball screw 73. The column 5 moves in the X-axis direction together with the nut and can move in the Y-axis direction via the transfer body 12. The column 5 has a pair of Z-axis guide rails (not shown), a Z-axis ball screw (not shown), a Z-axis motor 53 (refer to Figure 3 ) etc. on its front surface. The Z-axis guide rails and the Z-axis ball screw extend in the Z-axis direction. The Z-axis ball screw is arranged between a pair of Z-axis guide rails.

[0036] The spindle head 7 can move along the Z-axis guide rail. The spindle head 7 has a nut (not shown) on its back surface. This nut is screwed onto the Z-axis ball screw. The Z-axis motor 53 rotates the Z-axis ball screw. The spindle head 7 moves in the Z-axis direction together with the nut and can move in the X-axis direction and the Y-axis direction via the column 5 and the transfer body 12. The tool axis 8 is arranged on the spindle head 7. The tool axis 8 has a tool mounting hole (not shown) at its lower end. The tool mounting hole is located at the lower part of the tool axis 8. The tool D is mounted in the tool mounting hole. The tool axis motor 54 rotates the tool axis 8. The tool axis motor 54 is arranged at the upper part of the spindle head 7.

[0037] The workpiece holding device 80 has a left fixing portion 88, a right fixing portion 89, a workbench 81, a workpiece axis 82, a workpiece axis motor 56, a tilt motor 57, etc. The left fixing portion 88 is fixed on the upper surface of the left front pedestal portion 18. The right fixing portion 89 is fixed on the upper surface of the right front pedestal portion 19. The workbench 81 has a horizontal portion 81A, a left connecting portion 81C, and a right connecting portion 81B. The workpiece axis 82 is rotatably arranged approximately at the center of the workbench 81. The workpiece axis motor 56 is arranged on the lower surface side of the horizontal portion 81A. The workpiece axis 82 is connected to the rotating shaft of the workpiece axis motor 56. The rotating shaft of the workpiece axis motor 56 is orthogonal to the horizontal portion 81A. The workpiece axis 82 can hold the workpiece W at its upper part using a fixture (not shown).

[0038] The left connecting portion 81C extends obliquely upward to the left from the horizontal portion 81A and is connected to the left fixing portion 88. The left fixing portion 88 supports the left connecting portion 81C so as to be rotatable about an axis extending in the left-right direction. The right connecting portion 81B extends obliquely upward to the right from the horizontal portion 81A and is connected to the right fixing portion 89. The right fixing portion 89 supports the right connecting portion 81B so as to be rotatable about an axis extending in the left-right direction. The tilting motor 57 is fixed to the right fixing portion 89. The rotation axis of the tilting motor 57 is connected to the right connecting portion 81B. The tilting motor 57 rotates the worktable 81 about an axis extending in the left-right direction. The workpiece W held on the workpiece axis 82 rotates about the axis of the workpiece axis 82 by the drive of the workpiece axis motor 56. The workpiece W rotates about an axis perpendicular to the horizontal portion 81A by the drive of the workpiece axis motor 56, regardless of the rotation of the worktable 81 caused by the tilting motor 57.

[0039] The ATC 30 includes a tool magazine 31, a tool magazine support member 32, a tool magazine motor 55, a drive gear 35, etc. The tool magazine support member 32 is in an elliptical ring shape and is mounted on the column 5 with the spindle head 7 and the column 5 disposed inside. The tool magazine 31 is mounted along the outer side of the tool magazine support member 32. The tool magazine 31 has a chain 34 and a plurality of tool holders 37. The chain 34 is mounted so as to be movable along the outer circumference of the tool magazine support member 32. The plurality of tool holders 37 are respectively mounted on the chain 34. The tool holder 37 can hold the tool D. The tool holder 37 is formed in an arm shape and is mounted so as to be swingable in the front-rear direction.

[0040] The tool magazine motor 55 is mounted on the upper part of the tool magazine support member 32. The drive shaft of the tool magazine motor 55 is orthogonal to the upper surface of the tool magazine support member 32. The drive shaft of the tool magazine motor 55 can rotate in the forward and reverse directions respectively. The drive gear 35 is mounted on the drive shaft of the tool magazine motor 55. The drive gear 35 rotates together with the drive shaft of the tool magazine motor 55. The drive gear 35 meshes with the chain 34 of the tool magazine 31. The chain 34 moves along the outer circumference of the tool magazine support member 32 in the forward or reverse direction by the drive of the drive gear 35. Therefore, the tool holder 37 moves along the outer circumference of the tool magazine support member 32 together with the chain 34. The position of the tool holder 37 at the lowermost part of the tool magazine 31 is the tool change position. The tool change position is the position closest to the tool axis 8. The ATC 30 exchanges the next tool with the current tool. The next tool refers to the tool used in the next machining and is the tool held by the tool holder 37 at the tool change position. The current tool is the tool mounted on the tool axis 8 and represents the tool currently being machined.

[0041] Refer to Figure 3, the electrical structure of the machine tool 1 will be described. The machine tool 1 has a numerical control device 20. The numerical control device 20 has a CPU 21, a ROM 22, a RAM 23, a storage device 24, a bus 25, an input / output interface 26, etc. The CPU 21 uniformly controls the operation of the machine tool 1. The ROM 22 stores various programs such as a main program, a two-axis synchronization control program, and a phase matching control program described later. The main program is a program for executing the main processing of the numerical control device 20. The two-axis synchronization control program is a program for controlling the two-axis synchronous machining described later. The phase matching control program is a program for executing the phase matching control process described later (refer to Figure 11 ). The RAM 23 stores various data. The storage device 24 is a non-volatile memory and stores various data in addition to the NC program. The NC program consists of multiple program blocks. Each program block contains various commands. In addition to the NC program input by the operator through the input unit 28 of the operation panel 27, the CPU 21 can also store the NC program read in through external input, etc. in the storage device 24.

[0042] The machine tool 1 also has an operation panel 27. The operation panel 27 is provided, for example, on a cover (not shown) covering the machine tool 1. The operation panel 27 has an input unit 28 and a display unit 29. The input unit 28 receives various inputs related to the operation and setting of the machine tool 1. The display unit 29 displays various screens such as a setting screen and an operation screen of the machine tool 1. The input unit 28 and the display unit 29 are electrically connected to the input / output interface 26.

[0043] The drive circuit 41 drives the X-axis motor 51. The encoder 51A is connected to the X-axis motor 51 and the input / output interface 26. The encoder 51A detects the rotation amount of the X-axis motor 51 and inputs a detection signal to the CPU 21 via the input / output interface 26. The drive circuit 42 drives the Y-axis motor 52. The encoder 52A is connected to the Y-axis motor 52 and the input / output interface 26. The encoder 52A detects the rotation amount of the Y-axis motor 52 and inputs a detection signal to the CPU 21 via the input / output interface 26. The drive circuit 43 drives the Z-axis motor 53. The encoder 53A is connected to the Z-axis motor 53 and the input / output interface 26. The encoder 53A detects the rotation amount of the Z-axis motor 53 and inputs a detection signal to the CPU 21 via the input / output interface 26.

[0044] The drive circuit 44 drives the tool spindle motor 54. The encoder 54A is connected to the tool spindle motor 54 and the input / output interface 26. The encoder 54A detects the rotation amount of the tool spindle motor 54 and inputs a detection signal to the CPU 21 via the input / output interface 26. The drive circuit 45 drives the tool magazine motor 55. The encoder 55A is connected to the tool magazine motor 55 and the input / output interface 26. The encoder 55A detects the rotation amount of the tool magazine motor 55 and inputs a detection signal to the CPU 21 via the input / output interface 26. The drive circuit 46 drives the workpiece spindle motor 56. The encoder 56A is connected to the workpiece spindle motor 56 and the input / output interface 26. The encoder 56A detects the rotation amount of the workpiece spindle motor 56 and inputs a detection signal to the CPU 21 via the input / output interface 26.

[0045] The drive circuit 47 drives the tilt motor 57. The encoder 57A is connected to the tilt motor 57 and the input / output interface 26. The encoder 57A detects the rotation amount of the tilt motor 57 and inputs a detection signal to the CPU 21 via the input / output interface 26. The X-axis motor 51, Y-axis motor 52, Z-axis motor 53, tool spindle motor 54, tool magazine motor 55, workpiece spindle motor 56, and tilt motor 57 are servo motors. The drive circuit 48 drives the clamping device 58. The clamping device 58 is provided on the back side of the worktable 81. The clamping device 58 is used to fix and hold the workpiece spindle 82.

[0046] Refer to Figures 4 to 5 , the two-axis synchronous machining will be described. The two-axis synchronous machining is, for example, scraping machining, hobbing machining, turning and milling, etc., and is a method of performing free-form machining on the machining surface (the surface to be machined) of the workpiece W while synchronously rotating the tool spindle 8 and the workpiece spindle 82. As Figure 4 shown, for the sake of easy explanation, the axis direction D1 of the tool spindle 8 and the axis direction W1 of the workpiece spindle 82 are parallel to each other. The axis direction D1 and the axis direction W1 may also be intersecting directions. The workpiece spindle 82 holds the workpiece W with a fixture on the upper holding surface, and the tool spindle 8 mounts the tool D in the tool mounting hole. The tool D faces downward. The tool D has a plurality of cutting edges (for example, 8 cutting edges B1 to B8) on the side surface. For the sake of easy explanation, the machine tool 1 sets the direction of the imaginary straight line A connecting the axis position of the workpiece spindle 82 and the axis position of the tool spindle 8 as the X-axis direction. The numerical control device 20 controls so that the tool spindle 8 can move in the X-axis direction relative to the workpiece spindle 82. The numerical control device 20 may also control so that the workpiece spindle 82 can move in the X-axis direction relative to the tool spindle 8.

[0047] In the following description, for simplicity, focusing on the cutting edge B1 of the cutting tool D, the operation when machining the workpiece W with the cutting edge B1 will be mainly described. The tip of the cutting edge B1 contacts the machining surface of the workpiece W from the side. The initial cutting edge contact position of the cutting edge B1 is P1. The numerical control device 20 rotates the workpiece axis 82 and the tool axis 8 in opposite directions. The numerical control device 20 synchronously rotates the workpiece axis 82 and the tool axis 8 respectively in such a manner that the following formula (1) holds.

[0048] Sw / R + E = St / Q... (1)

[0049] Wherein, Sw is the rotational speed of the workpiece axis 82, St is the rotational speed of the tool axis 8, R is the number of cutting edges of the cutting tool D, E is the rotational speed difference, and Q is the shape number. The so-called shape number refers to the number of divisions of the workpiece W on the circumference of an imaginary circle, which is the number of each shape part obtained by division. Each of the divided shapes is a facing shape. The so-called imaginary circle refers to the circular locus along which the cutting edge contact position of the cutting edge B1 moves relative to the machining surface of the workpiece W during the synchronous rotation of the workpiece axis 82 and the tool axis 8. The rotational speed difference E is a value sufficiently smaller than (Sw / R) and (St / Q). Due to the rotational speed difference E, a time difference occurs in the contact between the cutting edge B of the cutting tool D and the machining surface of the workpiece W. When the rotational speed difference E is 0, the workpiece W is machined into a polygonal shape by ordinary polygon machining. The time difference generates a phase difference Δθ. Due to the phase difference Δθ, the cutting edge contact position of the cutting edge B1 shifts from P1 to P2. When the workpiece axis 82 and the tool axis 8 continue to rotate synchronously, the cutting edge contact position of the cutting edge B1 moves on the circumference of the imaginary circle centered on the rotation center of the workpiece W. The numerical control device 20 forms a minute free form on the circumference of the imaginary circle of the workpiece W by controlling the position of the cutting tool D in the X-axis direction during each period when the cutting edge B1 passes through the imaginary straight line A.

[0050] When the workpiece axis 82 and the tool axis 8 are synchronously rotated respectively, for example, as Figure 5 shown, the cutting edge contact position of the cutting tool D sequentially moves to P1, P2, P3, P4... during each cycle when the cutting edge B1 passes through the imaginary straight line A. The numerical control device 20 moves the cutting tool D in the X-axis direction during each cycle when the cutting edge B1 passes through the imaginary straight line A to reach the target position. The cutting edge contact positions P1, P2, P3, P4... change positions in the radial direction of the imaginary circle. Therefore, the numerical control device 20 can accurately form a free form on the machining surface of the workpiece W. The free form formed by the cutting edge B1 is, for example, a broken line shape bent at the cutting edge contact positions P1 to P4.

[0051] The same applies to the cutting edge B2 of the tool D. During each period when the cutting edge B2 passes through the imaginary straight line A, the contact positions of the cutting edge of the tool D sequentially move to P5, P6, P7, P8,.... Therefore, in the circumferential direction of the workpiece W, a shape identical to that formed by the cutting edge B1 is formed by the cutting edge B2 in a part different from the part where the shape formed by the cutting edge B1 is located. Figure 5 For the sake of convenience of explanation, the number of shapes formed on the workpiece W is shown as being relatively small. The same applies to the cutting edges B3 to B8 of the tool D. Therefore, the numerical control device 20 can form a number of free-form shapes corresponding to the number of shapes in the circumferential direction of the workpiece W through two-axis synchronous machining.

[0052] Refer to Figures 6 to 9 to explain the phase matching control. The phase matching control is a control for performing phase matching of the absolute phases of the tool axis 8 and the workpiece axis 82. In two-axis synchronous machining, in a state where the workpiece axis 82 and the tool axis 8 rotate synchronously, the tool D is moved in the cutting direction relative to the workpiece W by the feed axes (X-axis, Y-axis, Z-axis), thereby machining the workpiece W. Among the cutting edges B1 to B8 of the tool D, the cutting edge that first comes into contact with the workpiece W varies in each machining depending on various factors such as the rotation start timing and the phase at the start of rotation of the tool axis 8, the rotation start timing and the phase at the start of rotation of the workpiece axis 82, and the movement start timing of the tool axis 8 caused by the feed axes. The numerical control device 20 can set the cutting edge that first comes into contact with the workpiece W among the cutting edges B1 to B8 of the tool D as a specific cutting edge by performing the phase matching control.

[0053] For example, as Figure 6 shown, at T0, the workpiece axis 82 and the tool axis 8 are in a state of synchronous rotation at a specified rotation ratio. In the phase matching control process described later, the numerical control device 20 designates the phase of the workpiece axis 82 at T2 as α1 and the phase of the tool axis 8 as β1. The phase matching control is a control for correcting the phase β2 of the tool axis 8 in the uncorrected case to the designated β1 when the phase of the workpiece axis 82 is α1 at T2. The reason for correcting the phase of the tool axis 8 instead of the phase of the workpiece axis 82 is that in normal machining, the workpiece W is heavier than the tool D, so correcting the phase of the tool axis 8 can reduce the torque required for correction compared to correcting the phase of the workpiece axis 82.

[0054] During the phase matching time F, the numerical control device 20 corrects the phase of the tool axis 8 by controlling to temporarily slow down the rotational speed of the tool axis 8. The phase matching time F is the time taken for the process of temporarily decelerating the rotational speed of the tool axis 8 to correct the phase of the tool axis 8 from β2 at T2 to β1 and then returning to the original speed. Correcting the phase of the tool axis 8 by decelerating the rotational speed of the tool axis 8 is because if correction is performed by acceleration, the rotational speed of the tool axis 8 may reach the maximum speed. Therefore, the numerical control device 20 corrects the phase of the tool axis 8 by decelerating the rotational speed to prevent exceeding the rotational speed upper limit in terms of the performance of the tool axis motor 54. The numerical control device 20 sets the timing to start correction based on the phase of the workpiece axis 82 in order to perform correction so that the phase of the tool axis 8 at T2 becomes β1. The numerical control device 20 sets T1, which is the phase matching time F earlier than T2, as the timing to start correction.

[0055] As Figure 7 shown, the phase matching time F is obtained by multiplying the phase matching time constant Fx by two. The phase matching time constant is the total time of the time constant t1 and the time constant t2 described later. The time constant t1 is the time required from T1 when the rotational speed of the tool axis 8 starts to decelerate from V2 until T1A when a certain deceleration is reached. The time constant t2 is the time required from T1A until the deceleration becomes 0 and the rotational speed of the tool axis 8 becomes a certain V1 at a speed lower than V2 at T1B. The process of accelerating the rotational speed of the tool axis 8 from V1 to V2 from T1B to T1C to T2 is also performed with the same phase matching time constant Fx. That is, the numerical control device 20 decelerates the rotational speed of the tool axis 8 by using the phase matching time constant Fx from T1 to T1A to T1B, and then accelerates the rotational speed of the tool axis 8 by using the phase matching time constant Fx from T1B to T1C to T2, thereby correcting the phase of the tool axis 8 at T2 from β2 to β1. In the timing diagram of the phase of the tool axis 8 and time, the area Sa of the part surrounded by β0, β1, and β2 corresponds to the correction amount of the phase of the tool axis 8. In addition, in the timing diagram of the rotational speed of the tool axis 8 and time, the area Sb of the part surrounded by V2 and the rotational speed in the interval from T1 to T2 corresponds to the correction amount of the phase of the tool axis 8.

[0056] As Figure 6As shown, the numerical control device 20 obtains the phase difference by which the workpiece axis 82 advances during the phase matching time F required for the rotational speed of the workpiece axis 82. The numerical control device 20 obtains the phase α0 of the workpiece axis 82 at time T1 by subtracting the obtained phase difference from the phase α1 of the workpiece axis 82 at time T2. The phase of the workpiece axis 82 at α0 is referred to as the phase matching start phase α0. The numerical control device 20 starts the correction of the phase of the tool axis 8 when the phase of the workpiece axis 82 is α0 as T1.

[0057] On the basis of determining T1, the numerical control device 20 detects the timing when the phase of the workpiece axis 82 becomes the phase matching start phase α0 through the encoder 56A. Since the encoder 56A detects the phase of the workpiece axis 82 based on a pulse period that is decomposed into multiple parts in the circumferential direction, it is difficult to detect the exact timing when the phase of the workpiece axis 82 exactly becomes the phase matching start phase α0. Therefore, when the numerical control device 20 obtains outputs of values larger and smaller than the phase matching start phase α0 for the phase of the workpiece axis 82 in two consecutive pulse periods, it is considered that the phase of the workpiece axis 82 has reached the phase matching start phase α0. The numerical control device 20 calculates based on the phase of the workpiece axis 82 and the phase of the tool axis 8 in the pulse periods straddling before and after the phase matching start phase α0, and performs linear interpolation to calculate the phase of the tool axis 8 when the workpiece axis 82 reaches the phase matching start phase α0, that is, the phase matching start phase β0, according to the following formula (2).

[0058] β0 = S1 + {(r b - r a ) / r b}(S2 - S1)……(2)

[0059] Where, β0 is the phase matching start phase of the tool axis 8, S1 is the phase of the tool axis 8 detected in the pulse period immediately before straddling the phase matching start phase α0, S2 is the phase of the tool axis 8 detected in the pulse period immediately after straddling the phase matching start phase α0, r a is the phase difference between α0 and S1, and r b is the phase difference between S2 and S1.

[0060] The numerical control device 20 calculates the phase of the tool axis 8 at T2 without phase correction, that is, the non-corrected phase β2, according to the phase matching start phase β0 of the tool axis 8 obtained from formula (2) through formula (3).

[0061] β2 = β0 + V2 × F……(3)

[0062] Where, β2 is the non-corrected phase of the tool axis 8, V2 is the rotational speed of the tool axis 8, and F is the phase matching time.

[0063] The numerical control device 20 calculates a correction amount Δω for correcting the phase of the tool axis 8 from the uncorrected phase β2 to the specified phase β1 by Equation (4) based on the uncorrected phase β2 of the tool axis 8 obtained from Equation (3).

[0064] Δω = β1 - β2 ……(4)

[0065] Equation (4) is represented by the following four equations according to the conditions.

[0066] (A) When the rotation direction of the tool axis 8 is positive and (β1 - β2) ≥ 0:

[0067] Δω = (β1 - β2) - 360 ……(4 - 1)

[0068] The case where the rotation direction of the tool axis 8 is positive means the case where the phase of the tool axis 8 corresponding to the detection result obtained from the encoder 56A increases by 0° to 360°. In this case, as shown in (A) of Figure 8 , the inclination of the phase of the tool axis 8 between β0 - β1 is greater than the inclination of the phase of the tool axis 8 between β0 - β2. That is, the rotational speed from the phase matching start phase β0 to the specified phase β1 is faster than the rotational speed from the phase matching start phase β0 to the uncorrected phase β2. In this case, the phase matching start phase β0 is set to the phase matching start phase β0A in T0A that makes the rotational phase of the tool axis 8 one cycle amount (-360°) ahead of T1. Thus, the inclination of the phase of the tool axis 8 between β0A - β1 is smaller than the inclination of the phase of the tool axis 8 between β0 - β2. That is, the rotational speed from the phase matching start phase β0A to the specified phase β1 is slower than the rotational speed from the phase matching start phase β0 to the uncorrected phase β2. The numerical control device 20 can correct the phase of the tool axis 8 without the rotational speed of the tool axis 8 reaching the maximum speed. In the case of (A), the phase matching time F is the time obtained by adding the rotational time of one cycle amount of the tool axis 8.

[0069] (B) When the rotation direction of the tool axis 8 is positive and (β1 - β2) < 0:

[0070] Δω = (β1 - β2) ……(4 - 2)

[0071] As Figure 8 shown in (B) of , the inclination of the phase of the tool axis 8 between β0 - β1 is smaller than the inclination of the phase of the tool axis 8 between β0 - β2. That is, the rotational speed from the phase matching start phase β0 to the specified phase β1 is slower than the rotational speed from the phase matching start phase β0 to the uncorrected phase β2. The numerical control device 20 can correct the phase of the tool axis 8 without the rotational speed of the tool axis 8 reaching the maximum speed.

[0072] (C) When the rotation direction of the tool axis 8 is reverse and (β1 - β2) ≥ 0:

[0073] Δω = (β1 - β2)……(4 - 3)

[0074] The case where the rotation direction of the tool axis 8 is reverse means the case where the phase of the tool axis 8 corresponding to the detection result obtained from the encoder 56A decreases by 360° to 0°. In this case, as shown in (C) of Figure 8 , the inclination of the phase of the tool axis 8 between β0 - β1 is smaller than the inclination of the phase of the tool axis 8 between β0 - β2. That is, the rotational speed from the phase matching start phase β0 to the specified phase β1 is decelerated compared with the rotational speed from the phase matching start phase β0 to the uncorrected phase β2. Therefore, the numerical control device 20 can correct the phase of the tool axis 8 without the rotational speed of the tool axis 8 reaching the maximum speed.

[0075] (D) When the rotation direction of the tool axis 8 is reverse and (β1 - β2) < 0:

[0076] Δω = (β1 - β2) + 360……(4 - 4)

[0077] As shown in (D) of Figure 8 , the inclination of the phase of the tool axis 8 between β0 - β1 is larger than the inclination of the phase of the tool axis 8 between β0 - β2. The rotational speed from the phase matching start phase β0 to the specified phase β1 is accelerated compared with the rotational speed from the phase matching start phase β0 to the uncorrected phase β2. Therefore, as the phase matching start phase β0, the phase matching start phase β0B in T0A which is one cycle amount (+360°) ahead of the rotational phase T1 of the tool axis 8 is set. Thus, the inclination of the phase of the tool axis 8 between β0B - β1 is smaller than the inclination of the phase of the tool axis 8 between β0 - β2. That is, the rotational speed from the phase matching start phase β0B to the specified phase β1 is decelerated compared with the rotational speed from the phase matching start phase β0 to the uncorrected phase β2. Therefore, the numerical control device 20 can correct the phase of the tool axis 8 without the rotational speed of the tool axis 8 reaching the maximum speed. In the case of (D), the phase matching time F is the time added with the rotational time of one cycle amount of the tool axis 8.

[0078] The numerical control device 20 controls the acceleration and deceleration of the rotational speed of the tool axis 8 in the phase matching time F based on the correction amount Δω obtained from the formula (4) as described below. As shown in Figure 9As shown in (A) of [the figure], the corrected speed of the tool axis 8 before applying the filter, i.e., {Δω / (t1 + t2)}, is multiplied by (t1 + t2) and distributed so that the correction amount Δω of the tool axis 8 becomes the area Sb of the part surrounded by V2 and the rotational speed in the interval from T1 to T2. Then, as Figure 9 shown in (B) of [the figure], in the corrected speed of the tool axis 8 before applying the filter, a moving average filter with the time constant t1 during deceleration between T1 and T1A is used. Furthermore, as Figure 9 shown in (C) of [the figure], in the corrected speed of the tool axis 8, a moving average filter with the time constant t2 during deceleration between T1A and T1B is used. Thus, the numerical control device 20 can generate the corrected speed of the tool axis 8 such that during the phase matching time F, the rotational speed of the tool axis 8 smoothly decreases from V2 to V1 and then smoothly increases from V1 to V2.

[0079] At T2 when the correction ends, when the phase of the workpiece axis 82 becomes α1, the phase of the tool axis 8 becomes β1. The numerical control device 20 drives the feed axis at T2. The moving speed of the feed axis accelerates and reaches Va at T3. After T3, the numerical control device 20 maintains the moving speed of the feed axis at Va and moves the tool D toward the workpiece W in the cutting direction. At T4, the tool D contacts the workpiece W. At this time, the phase of the tool axis 8 is β3. The numerical control device 20 controls so that the phases of the workpiece axis 82 and the tool axis 8 at T2 are α1 and β1 as the absolute phases respectively, so that the phase of the tool axis 8 at T4 is located at β3. Therefore, when the numerical control device 20 repeatedly performs machining under the same conditions, it can control the phase of the tool axis 8 so that the cutting edge that first contacts the workpiece W among the cutting edges B1 to B8 of the tool D is always a specific cutting edge.

[0080] Refer to Figures 10 to 12 to describe the operation of the phase matching control. The CPU 21 of the numerical control device 20 uses the NC program 100 (refer to Figure 10 ) during the machining of the workpiece W. The NC program 100 is stored in the storage device 24.

[0081] Figure 10 is a part of the NC program 100 and is a phase matching program for executing the phase matching control process. The "M142" instruction of the phase matching program is an instruction for specifying the ratio of the rotational speed of the tool axis 8 to the workpiece axis 82. The ratio is input in the "U_", "V_" parts. For example, in the case of "M142 U3V2", it is specified that "rotational speed of tool axis 8:rotational speed of workpiece axis 82 = 3:2". Specifically, for example, when the rotational speed of the workpiece axis 82 is S100 min -1 , the rotational speed of the tool axis 8 is specified as S150 min -1 .

[0082] The "M303" instruction of the phase matching program is an instruction that causes the workpiece axis 82 to rotate forward at a specified rotational speed and causes the tool axis 8 to rotate synchronously with the workpiece axis 82 at the ratio specified by the "M142" instruction. Input the rotational speed in the part of "S_". For example, in the case of "M303S100", it indicates "causing the workpiece axis 82 to start rotating forward at S100 min -1 in the forward direction". The forward direction in the rotational direction of the workpiece axis 82 is, for example, the clockwise direction in the top view of the machine tool 1 (refer to Figure 4 ). The tool axis 8 rotates synchronously with the workpiece axis 82 in the direction opposite to the rotational direction of the workpiece axis 82 (for example, the counterclockwise direction in the top view of the machine tool 1).

[0083] The "M304" instruction is an instruction that causes the workpiece axis 82 to rotate backward at a specified rotational speed and causes the tool axis 8 to rotate synchronously with the workpiece axis 82 at the ratio specified by the "M142" instruction. Therefore, in the phase matching program, either the "M303" instruction or the "M304" instruction is issued. Input the rotational speed in the part of "S_". For example, in the case of "M304 S100", it indicates "causing the workpiece axis 82 to start rotating backward at S100 min -1 in the reverse direction". The reverse direction of the rotational direction of the workpiece axis 82 is, for example, the counterclockwise direction in the top view of the machine tool 1. The tool axis 8 rotates synchronously with the workpiece axis 82 in the direction opposite to the rotational direction of the workpiece axis 82 (for example, the clockwise direction in the top view of the machine tool 1). The definitions of the forward and reverse directions in the rotational direction of the workpiece axis 82 can also be the directions opposite to the above descriptions.

[0084] The "G333" instruction of the phase matching program is an instruction that performs a feed axis operation after phase-matching the phases of the synchronously rotating workpiece axis 82 and tool axis 8 at respectively specified phases. "X_", "Y_", and "Z_" are parameters that specify the coordinates for ending the movement operations of the X-axis, Y-axis, and Z-axis respectively. "Q_" is a parameter that specifies the specified phase α1 of the workpiece axis 82. "R_" is a parameter that indicates whether to perform phase matching. "E_" is a parameter that specifies the specified phase β1 of the tool axis 8. "F_" is a parameter that specifies the moving speed Va of the feed axis.

[0085] Refer to Figure 11, the phase matching control process executed by the CPU 21 will be described. When the operator starts the machine tool 1 and selects the NC program 100 for machining the workpiece W in the input unit 28, the CPU 21 reads the NC program 100 from the storage device 24. When the operator presses the execution button (not shown) of the input unit 28, the CPU 21 starts the main program from the ROM 22 and executes the main process on the NC program 100. In the main process, the CPU 21 interprets the instructions of the NC program 100 block by block to machine the workpiece W. As Figure 12 shown, various information during the machining of the workpiece W is displayed on the display screen 120 of the display unit 29. The rotational speed (main spindle speed) of the tool axis 8 is displayed in the main spindle speed display area 125 within the display screen 120. In the case of a mode where two-axis synchronous machining is not performed, the information on the rotational speed of the workpiece axis 82 is not displayed.

[0086] During the execution of the main program, the phase matching control program and the two-axis synchronous control program are executed. As Figure 10 shown, when the instruction interpreted by the CPU 21 is the "M142" instruction, the CPU 21 stores the ratio of the rotational speeds of the workpiece axis 82 and the tool axis 8 described in the "M142" instruction in the storage device 24. The CPU 21 switches to the mode for two-axis synchronous machining ( Figure 12 , S1), and in the main spindle speed display area 125 within the display screen 120, in addition to the part for displaying the rotational speed (main spindle speed) of the tool axis 8, there is also a part for displaying the rotational speed (lathe spindle speed) of the workpiece axis 82 (refer to Figure 12 ). Thus, the CPU 21 notifies that it is the mode for two-axis synchronous machining.

[0087] When the instruction interpreted by the CPU 21 is the "M303" instruction, the CPU 21 starts the forward rotation of the workpiece axis 82 at the rotational speed described in the "M303" instruction. When the instruction interpreted by the CPU 21 is the "M304" instruction, the CPU 21 starts the reverse rotation of the workpiece axis 82 at the rotational speed described in the "M304" instruction. The CPU 21 multiplies the rotational speed of the workpiece axis 82 described in the "M303" or "M304" instruction by the ratio stored in the storage device 24 to calculate the rotational speed of the tool axis 8. When the instruction is "M303", the CPU 21 starts the reverse synchronous rotation of the tool axis 8 at the calculated rotational speed, and when the instruction is "M304", the CPU 21 starts the forward synchronous rotation of the tool axis 8 at the calculated rotational speed. The CPU 21 displays the rotational speed of the tool axis 8 based on the detection result of the encoder 54A in the part of the main spindle speed display area 125 for displaying the rotational speed (main spindle speed) of the tool axis 8 ( Figure 12, S2). The CPU 21 displays the rotational speed of the workpiece axis 82 (lathe spindle speed) in the part of the spindle speed display area 125 that displays the rotational speed of the workpiece axis 82, and displays the rotational speed of the workpiece axis 82 based on the detection result of the encoder 56A ( Figure 12 , S2).

[0088] When the instruction interpreted by the CPU 21 is the "G333" instruction, the CPU 21 performs phase matching processing. As Figure 11 shown, the CPU 21 calculates the phase matching start phase α0 of the workpiece axis 82 based on the rotational speed of the workpiece axis 82 and the phase matching time F (S11).

[0089] The CPU 21 determines whether the phase of the workpiece axis 82 has reached the phase matching start phase α0 based on the detection result of the encoder 56A (S13). If it has not reached, it stands by (S13: No). When the CPU 21 obtains the detection result that the phase of the workpiece axis 82 crosses values larger and smaller than the phase matching start phase α0 from the encoder 56A, the CPU 21 determines that the phase of the workpiece axis 82 has reached the phase matching start phase α0 (S13: Yes). The CPU 21 calculates the phase of the tool axis 8 when the workpiece axis 82 reaches the phase matching start phase α0, that is, the phase matching start phase β0, according to Equation (2) (S15).

[0090] The CPU 21 calculates the phase of the tool axis 8 at the completion of phase matching without correcting the phase of the tool axis 8, that is, the non-corrected phase β2, according to Equation (3). The CPU 21 calculates the correction amount Δω of the phase of the tool axis 8 according to Equation (4) (S19). The CPU 21 calculates the correction speed before applying the filter based on the correction amount Δω of the phase of the tool axis 8, and generates the correction speed of the tool axis 8 by using a moving average filter with time constant t1 and time constant t2. The CPU 21 corrects the rotational speed of the tool axis 8 according to the generated correction speed (S21).

[0091] The CPU 21 determines whether the phase of the tool axis 8 has reached the specified phase β1 based on the detection result of the encoder 54A (S23). When the phase of the tool axis 8 has not reached the specified phase β1 (S23: No), the CPU 21 returns the process to S21 and corrects the rotational speed of the tool axis 8 according to the correction speed generated in S19. When the phase of the tool axis 8 has reached the specified phase β1 (S23: Yes), the CPU 21 starts the operation of the feed axis (S25). The tool axis 8 starts to move in the cutting direction. The CPU 21 ends the phase matching control process, returns to the main process, and starts machining the workpiece W with the tool D.

[0092] When the two-axis synchronous machining mode ends, the CPU 21 notifies that it is not the two-axis synchronous machining mode by displaying only the rotational speed (main spindle speed) of the tool axis 8 in the main spindle speed display area 125. Figure 12 (S 3).

[0093] As described above, the numerical control device 20 controls the synchronous rotation of the tool axis 8 and the work axis 82 to machine the workpiece W. When the phases of the tool axis 8 and the work axis 82 match, the numerical control device 20 can set the rotational phase angles of the tool axis 8 and the work axis 82 at the end of phase matching, namely the specified phase β1 and the specified phase α1. Therefore, when starting to machine the workpiece W with the tool D, the numerical control device 20 can control the cutting edge B of the tool D in contact with the workpiece W, and can suppress the wear of the cutting edge B of the tool D.

[0094] The numerical control device 20 starts driving the X-axis, Y-axis, and Z-axis at the end of phase matching, so that the timing of contact between the tool D and the workpiece W can be kept constant for each machining.

[0095] The numerical control device 20 designates the specified phase β1 and the specified phase α1 as variables in the "G333" command, so that the user does not need to perform the operation of presetting the specified phase β1 and the specified phase α1 before executing the phase matching operation.

[0096] The torque required for the rotation of the tool axis 8 is smaller than the torque required for the rotation of the work axis 82. Therefore, the numerical control device 20 can smoothly perform the phase matching between the tool axis 8 and the work axis 82 by correcting the phase of the tool axis 8 to the specified phase β1.

[0097] The numerical control device 20 can notify the user that the tool axis 8 and the work axis 82 are in synchronous rotation through the main spindle speed display area 125 of the display screen 120 displayed on the display unit 29.

[0098] Since the workpiece W is a machined gear, the numerical control device 20 can machine the machined gear through the synchronous rotation of the tool axis 8 and the work axis 82 as a gear cutting tool.

[0099] In the above description, the jig is an example of the "stage" of the present invention. The CPU 21 that performs two-axis synchronous control is an example of the "synchronous control unit" of the present invention. The CPU 21 that performs phase matching control is an example of the "phase control unit" of the present invention. The specified phase β1 is an example of the "set tool angle" of the present invention. The CPU 21 that executes the "G333 E_" instruction is an example of the "tool axis phase angle setting unit" of the present invention. The specified phase α1 is an example of the "set workpiece angle" of the present invention. The CPU 21 that executes the "G333 Q_" instruction is an example of the "workpiece axis phase angle setting unit" of the present invention. The X-axis, Y-axis, and Z-axis are examples of the "feed axes" of the present invention. The CPU 21 that executes the process of S25 is an example of the "feed control unit" of the present invention. The NC program 100 is an example of the "processing program" of the present invention. The "G333" instruction is an example of the "phase instruction" of the present invention. The parameter "E_" of the "G333" instruction is an example of the "tool setting angle specification variable" of the present invention. The parameter "Q_" of the "G333" instruction is an example of the "workpiece setting angle specification variable" of the present invention.

[0100] The phase matching start phase α0 is an example of the "start workpiece angle" of the present invention. The CPU 21 that executes the process of S11 is an example of the "start workpiece angle calculation unit" of the present invention. The phase matching start phase β0 is an example of the "start tool angle" of the present invention. The CPU 21 that executes the process of S15 is an example of the "start tool angle calculation unit" of the present invention. The uncorrected phase β2 is an example of the "end tool angle" of the present invention. The CPU 21 that executes the process of S17 is an example of the "end tool angle calculation unit" of the present invention. The CPU 21 that executes the process of S19 is an example of the "correction amount calculation unit" of the present invention. The CPU 21 that executes the process of S21 is an example of the "tool speed control unit" of the present invention. The display unit 29 is an example of the "display device" of the present invention. The spindle speed display area 125 is an example of the "notification screen" of the present invention. The CPU 21 that executes the process of S1 is an example of the "notification unit" of the present invention.

[0101] The present invention is not limited to the above-described embodiments and can be variously modified. The numerical control device 20 executes the phase matching control process according to the instructions described in the NC program 100, but may also execute the phase matching control process according to an instruction input by the operator from the input unit 28. The numerical control device 20 performs phase matching control by correcting the rotational speed of the tool axis 8 while maintaining the rotational speed of the workpiece axis 82, but may also correct the rotational speed of the workpiece axis 82 while maintaining the rotational speed of the tool axis 8. Alternatively, the numerical control device 20 may also correct the rotational speeds of the tool axis 8 and the workpiece axis 82 respectively to perform phase matching control.

[0102] In the "M142" instruction, the ratio of the rotational speed of the tool axis 8 to the rotational speed of the workpiece axis 82 is specified, but the magnification of the rotational speed of the tool axis 8 to the rotational speed of the workpiece axis 82 may also be specified. Alternatively, instead of the "M142" instruction, in the "M303" or "M304" instruction, not only the rotational speed of the workpiece axis 82 but also the rotational speed of the tool axis 8 may be specified. Thus, the rotational speeds of the tool axis 8 and the workpiece axis 82 are directly specified by numerical values instead of by a ratio. An instruction summarizing the "M142" instruction, the "M303" or "M304" instruction, and the "G333" instruction may also be generated and executed as a single instruction.

[0103] The numerical control device 20 sets the cutting direction in which the tool axis 8 moves relative to the workpiece axis 82 as the X-axis direction, but any direction of the X-axis, Y-axis, and Z-axis may be set as the cutting direction as long as it is a direction in which the tool D can machine the workpiece W. In addition, the workpiece axis 82 may be moved relative to the tool axis 8 in the X-axis direction.

[0104] The numerical control device 20 may also have a function of appropriately shifting the cutting edge B of the tool D that first contacts the workpiece W. For example, append "I_" to the parameters of the "G333" instruction. "I_" is a parameter for specifying the number of cutting edges of the cutting edge B of the tool D. When the instruction interpreted by the CPU 21 is the "G333" instruction, as Figure 13 shown, before executing S11 of the phase matching process, the CPU 21 executes the processes of S31 to S47. In the processes of S31 to S47, the retention count is the number of times of retaining the shift of the cutting edge B of the tool D, and the initial value is 0. The shifted phase H is the phase obtained by shifting the specified phase β1. In the processes of S11 to S25, instead of the specified phase β1, the shifted phase H is used for calculation. Hst is the phase of the tool axis 8 in the reference machining (for example, the first machining in repeated machining under the same conditions), that is, the specified phase β1. N is the number of shifted cutting edges, and the initial value is 0. The retention count and N are stored in the storage device.

[0105] The CPU 21 increments the retention count by 1 and stores it in the storage device 24 (S31). The CPU 21 calculates the shifted phase H after shifting the specified phase β1 according to the following formula (5) (S33).

[0106] H = Hst + N × (360 / I) …… (5)

[0107] That is, the shifted phase H of the tool axis 8 is obtained by adding the value obtained by multiplying the setting angle interval (360 / I) of the cutting edge B by the number of shifted cutting edges N to the reference Hst. Since the initial value of N is 0, the cutting edge B that first contacts the workpiece W does not shift.

[0108] When the retention count is less than 5 (S35: No), the CPU 21 transfers the process to S11. Therefore, in the first to fourth machining operations, the same cutting edge B is set as the cutting edge B that first contacts the workpiece W. When the retention count is 5 or more (S35: Yes), the CPU 21 resets the retention count to 0 (S37), increments N by 1 and stores it in the storage device 24 (S39). From the next time on, the shifted phase H becomes the phase that shifts the cutting edge B by one cutting edge. When N is less than I (S41: No), the CPU 21 transfers the process to S11. When N is I or more (S41: Yes), the CPU 21 sets N to 0 and stores it in the storage device 24 (S43). Thus, when all the cutting edges B are used as the cutting edge B that first contacts the workpiece W, the cutting edge B that was used first is set as the cutting edge B that first contacts the workpiece W. The process is transferred to S11.

[0109] The numerical control device 20 can stagger the cutting edges B that first contact the workpiece W in sequence during each of multiple machining operations of the workpiece W using the tool D by changing the shifted phase H, and can suppress the wear of the tool D. The cutting edge B is an example of the "cutting edge" of the present invention. The CPU 21 that executes the process of S33 is an example of the "tool angle shifting unit" of the present invention. In this modification example, the retention count determined in S35 is not limited to 5 or more, and the number of times can be set appropriately. Alternatively, the setting of the retention count may not be provided. In addition, in S39, the number by which N is incremented is not limited to +1, and it can also be set to +2 or the like to shift by skipping one cutting edge.

Claims

1. A numerical control device for controlling a machine tool having a tool axis on which a tool is mounted and a workpiece axis for rotating a table on which a workpiece is fixed, so as to machine the workpiece, comprising: A synchronization control unit configured to perform control for synchronously rotating the tool axis and the workpiece axis; And A phase control unit configured to perform phase matching of the rotation phase angles of the tool axis and the workpiece axis based on the rotation phase angle of the tool axis and the rotation phase angle of the workpiece axis during the synchronous rotation of the tool axis and the workpiece axis performed by the synchronization control unit, The phase control unit includes: A tool axis phase angle setting unit configured to set a set tool angle, which is the rotation phase angle of the tool axis at the end of the phase matching; And A workpiece axis phase angle setting unit configured to set a set workpiece angle, which is the rotation phase angle of the workpiece axis at the end of the phase matching, The phase matching is performed by relatively controlling the rotation speeds of the tool axis and the workpiece axis, so that the rotation phase angle of the tool axis at the end of the phase matching between the tool axis and the workpiece axis becomes the set tool angle and the rotation phase angle of the workpiece axis becomes the set workpiece angle.

2. The numerical control device according to claim 1, characterized in that, The machine tool includes a feed axis for relatively moving the tool axis and the workpiece axis, The phase control unit includes a feed control unit for controlling the drive of the feed axis, When the rotation phase angle of the tool axis becomes the set tool angle and the rotation phase angle of the workpiece axis becomes the set workpiece angle, the feed control unit drives the feed axis to start the relative movement of the tool axis and the workpiece axis to the position where the tool machines the workpiece.

3. The numerical control device according to claim 1, characterized in that, The numerical control device starts the operation of the phase matching according to a phase command, which is a command for instructing the operation of the phase matching between the tool axis and the workpiece axis, The tool axis phase angle setting unit sets the set tool angle based on a tool setting angle designation variable in the phase command for designating the set tool angle, The workpiece axis phase angle setting unit sets the set workpiece angle based on a workpiece setting angle designation variable in the phase command for designating the set workpiece angle.

4. The numerical control device according to claim 1, characterized in that, The phase control unit includes: A start workpiece angle calculation unit configured to calculate a start workpiece angle based on the set workpiece angle, the workpiece axis synchronization speed, and the phase matching time, where the workpiece axis synchronization speed is the rotation speed of the workpiece axis during machining controlled by the synchronization control unit, the phase matching time is the preset time required for the phase matching, and the start workpiece angle is the rotation phase angle of the workpiece axis at the start of the phase matching; A start tool angle calculation unit configured to calculate a start tool angle, which is the rotation phase angle of the tool axis when the workpiece axis reaches the start workpiece angle; An end tool angle calculation unit configured to calculate an end tool angle based on the start tool angle, the tool axis synchronization speed, and the phase matching time, where the tool axis synchronization speed is the rotational speed during machining of the tool axis controlled by the synchronization control unit, and the end tool angle is the rotational phase angle reached by the tool axis after the phase matching time from the start tool angle; A correction amount calculation unit configured to calculate the difference between the set tool angle and the end tool angle as the correction amount; and A tool speed control unit configured to control the rotational speed of the tool axis based on the correction amount, so that the tool axis reaches the set tool angle after the phase matching time from the start tool angle.

5. The numerical control device according to claim 1, characterized in that, The machine tool includes a display device for displaying information, The synchronization control unit includes a notification unit configured to display a notification screen on the display device, and the notification screen is used to notify that the tool axis and the workpiece axis are rotating synchronously.

6. The numerical control device according to claim 1, wherein, The phase control unit includes a tool angle shift unit configured to change the set tool angle based on the number of cutting edges of the tool, Each time the tool processes the workpiece once or multiple times, the tool angle shift unit changes the set tool angle.

7. The numerical control device according to claim 1, characterized in that, The workpiece is a machined gear.

8. A control method for a numerical control device, the numerical control device being configured to control a machine tool having a tool axis on which a tool is mounted and a workpiece axis that rotates a table for fixing a workpiece, so as to machine the workpiece, the control method including: A synchronization control step for performing control to synchronously rotate the tool axis and the workpiece axis; And A phase control step for performing phase matching of the rotational phase angles of the tool axis and the workpiece axis based on the rotational phase angle of the tool axis and the rotational phase angle of the workpiece axis during the synchronous rotation of the tool axis and the workpiece axis performed in the synchronization control step, The phase control step includes: A tool axis phase angle setting step for setting a set tool angle, where the set tool angle is the rotational phase angle of the tool axis at the end of the phase matching; And A workpiece axis phase angle setting step for setting a set workpiece angle, where the set workpiece angle is the rotational phase angle of the workpiece axis at the end of the phase matching, The phase matching is performed by relatively controlling the rotational speed of the tool axis and the rotational speed of the workpiece axis, so that the rotational phase angle of the tool axis at the end of the phase matching between the tool axis and the workpiece axis becomes the set tool angle and the rotational phase angle of the workpiece axis becomes the set workpiece angle.

9. A storage medium storing a program for controlling a numerical control device, the numerical control device being configured to control a machine tool having a tool axis on which a tool is mounted and a workpiece axis that rotates a table for fixing a workpiece, so as to machine the workpiece, the program being executed on a computer: A synchronization control step for performing control to synchronously rotate the tool axis and the workpiece axis; and A phase control step for performing phase matching of the rotational phase angles of the tool axis and the workpiece axis during the synchronous rotation of the tool axis and the workpiece axis carried out in the synchronous control step, based on the rotational phase angle of the tool axis and the rotational phase angle of the workpiece axis. Performed in the phase control step: A tool axis phase angle setting step for setting a set tool angle, which is the rotational phase angle of the tool axis at the end of the phase matching; and A workpiece axis phase angle setting step for setting a set workpiece angle, which is the rotational phase angle of the workpiece axis at the end of the phase matching, The phase matching is carried out by relatively controlling the rotational speed of the tool axis and the rotational speed of the workpiece axis, so that the rotational phase angle of the tool axis at the end of the phase matching between the tool axis and the workpiece axis becomes the set tool angle and the rotational phase angle of the workpiece axis becomes the set workpiece angle.

Images