Machine tool, control method, and control program

Abstract

To provide a technique for improving the accuracy of gear cutting. [Solution] The machine tool includes a work spindle, a tool holder configured to hold a pinion cutter, a first rotation drive unit that rotates and drives the work spindle about a first axis along the axial direction of the work spindle, a feed drive unit that moves the tool holder, a second rotation drive unit that rotates and drives the tool holder about a second axis along the axial direction of the pinion cutter, a first brake mechanism that brakes the rotation of the work spindle, a second brake mechanism that brakes the rotation of the tool holder, and a control unit. The control unit executes a reciprocating drive process that drives the tool holder back and forth in the direction of the first axis, and an adjustment process that rotates the work spindle a predetermined angle about the first axis and the tool holder a predetermined angle about the second axis. The reciprocating drive process is executed with the first and second brake mechanisms applied. The adjustment process is executed with the brakes not applied.

Description

[Technical Field]

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

[0002] Conventionally, gear machining has been performed using a dedicated machine that uses a pinion cutter. In this regard, Japanese Patent Laid-Open Publication No. 2000-190127 (Patent Document 1) discloses a technique for adding a gear shaping function using a pinion cutter to the machining function of a machining center (paragraph

[0007] ).

[0003] The machining center disclosed in Patent Document 1 includes a table that can be driven in the X-axis and Y-axis directions, and a tool spindle that can be driven in the Z-axis direction. A workpiece is fixed to the table. The machining center performs gear cutting by reciprocating the tool spindle in the Z-axis direction while synchronizing the relative circular interpolation motion between the workpiece and a pinion cutter attached to the tool spindle. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-190127 Summary of the Invention [Problem to be solved by the invention]

[0005] The machining center disclosed in Patent Document 1 rotates the pinion cutter around the C axis at a rotation speed of n, while controlling the drive of the table in the X-axis and Y-axis directions so that the tool spindle revolves relatively around the workpiece on a circumference of a radius of (m·z1+m·z2) / 2 (paragraph

[0018] ). In other words, the machining center achieves gear cutting by constantly driving the tool spindle around the C axis at a constant speed.

[0006] However, because the pinion cutter experiences cutting resistance while cutting the workpiece, it is difficult to perform gear cutting while maintaining a constant rotation speed of the tool spindle. As a result, the machining center disclosed in Patent Document 1 is unable to sufficiently improve the accuracy of gear cutting.

[0007] Therefore, there is a demand for a technique for improving the accuracy of gear cutting in a machine tool having a tool holder capable of feed driving. [Means for solving the problem]

[0008] One example of the present disclosure provides a machine tool including a work spindle configured to hold a workpiece, a tool holder configured to hold a pinion cutter, a first rotation drive unit for driving the work spindle to rotate about a first axis along the axial direction of the work spindle, a feed drive unit for moving the tool holder, a second rotation drive unit for driving the tool holder to rotate about a second axis along the axial direction of the pinion cutter, a first brake mechanism for braking the rotation of the work spindle, a second brake mechanism for braking the rotation of the tool holder, and a control unit for controlling the feed drive unit, the first and second rotation drive units, and the first and second brake mechanisms. The control unit executes a reciprocating drive process for cutting gears on the inner peripheral surface or the outer peripheral surface of the workpiece by driving the tool holder back and forth in the direction of the first axis, and an adjustment process for adjusting the rotation angle between the workpiece spindle and the tool holder by rotating the workpiece spindle by a predetermined angle about the first axis and rotating the tool holder by a predetermined angle about the second axis. The reciprocating drive process is executed with the brake applied by the first brake mechanism and the brake applied by the second brake mechanism. The adjustment process is executed with the brake applied by the first brake mechanism and the brake applied by the second brake mechanism not being applied.

[0009] In one example of the present disclosure, the control unit monitors the temperature of a drive system related to the feed drive unit, and executes an abnormality handling process when the temperature exceeds a second threshold value.

[0010] In one example of the present disclosure, the abnormality handling process includes at least one of a process of stopping gear cutting of the workpiece and a process of outputting a warning.

[0011] In one example of the present disclosure, the control unit executes a process of stopping the execution of the abnormality handling process based on the temperature falling below a first threshold value.

[0012] In one example of the present disclosure, the control unit further executes the reciprocating drive process and the adjustment process based on preset parameters. The parameters include a parameter for specifying whether to enable braking by the first brake mechanism. If the parameter is set to enable braking by the first brake mechanism, the control unit executes the reciprocating drive process while enabling the brake. If the parameter is set to disable braking by the first brake mechanism, the control unit executes the reciprocating drive process while disabling the brake and maintaining the rotation angle of the workpiece spindle at a target rotation angle corresponding to a command value.

[0013] In one example of the present disclosure, in the reciprocating drive process, the tool holder is reciprocally driven between a first position in the direction of the first axis and a second position in the direction of the first axis. The first position is a position that is a first distance away from a surface on one side of the workpiece in the direction of the first axis. The second position is a position that is a second distance away from a surface on the other side of the workpiece in the direction of the first axis.

[0014] In one example of the present disclosure, the control unit further executes the reciprocating drive process based on preset parameters, the parameters including the first distance and the second distance.

[0015] In one example of the present disclosure, the control unit further performs the adjustment process based on preset parameters, the parameters including a correction value related to a rotation center of the tool holder during the adjustment process.

[0016] In one example of the present disclosure, the control unit further executes the reciprocating drive process based on preset parameters, including a parameter for specifying whether or not to tilt a feed drive direction of the tool holder when cutting the gear of the workpiece in a cutting direction of the workpiece.

[0017] In another example of the present disclosure, a method for controlling a machine tool includes the machine tool comprising: a work spindle configured to hold a workpiece; a tool holding unit configured to hold a pinion cutter; a first rotation drive unit for rotationally driving the work spindle about a first axis along the axial direction of the work spindle; a feed drive unit for moving the tool holding unit; a second rotation drive unit for rotationally driving the tool holding unit about a second axis along the axial direction of the pinion cutter; a first brake mechanism for braking the rotation of the work spindle; a second brake mechanism for braking the rotation of the tool holding unit; and a control unit for controlling the feed drive unit, the first and second rotation drive units, and the first and second brake mechanisms. The control method causes the control unit to execute a reciprocating driving step of reciprocatingly driving the tool holder in the direction of the first axis to perform gear cutting on the inner surface or the outer surface of the workpiece, and an adjustment step of adjusting the rotation angle between the workpiece spindle and the tool holder by rotating the workpiece spindle by a predetermined angle about the first axis and rotating the tool holder by a predetermined angle about the second axis. The reciprocating driving step is executed with the brake by the first brake mechanism and the brake by the second brake mechanism applied. The adjustment step is executed with the brake by the first brake mechanism and the brake by the second brake mechanism not applied.

[0018] In another example of the present disclosure, a control program for a machine tool includes a work spindle configured to hold a workpiece, a tool holding unit configured to hold a pinion cutter, a first rotation drive unit for rotationally driving the work spindle about a first axis along the axial direction of the work spindle, a feed drive unit for moving the tool holding unit, a second rotation drive unit for rotationally driving the tool holding unit about a second axis along the axial direction of the pinion cutter, a first brake mechanism for braking the rotation of the work spindle, a second brake mechanism for braking the rotation of the tool holding unit, and a control unit for controlling the feed drive unit, the first and second rotation drive units, and the first and second brake mechanisms. The control program causes the control unit to execute a reciprocating drive process for performing gear cutting on the inner peripheral surface or the outer peripheral surface of the workpiece by driving the tool holder reciprocally in the direction of the first axis, and an adjustment process for adjusting the rotation angle between the workpiece spindle and the tool holder by rotating the workpiece spindle by a predetermined angle about the first axis and rotating the tool holder by a predetermined angle about the second axis. The reciprocating drive process is executed with the brake by the first brake mechanism and the brake by the second brake mechanism applied. The adjustment process is executed with the brake by the first brake mechanism and the brake by the second brake mechanism not applied.

[0019] The above and other objects, features, aspects and advantages of the present invention will become apparent from the following detailed description of the invention taken in conjunction with the accompanying drawings. [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 1 is a diagram showing the appearance of a machine tool. [Figure 2] FIG. 1 is a diagram illustrating an example of a device configuration of a machine tool. [Figure 3] FIG. 2 is a diagram illustrating an example of a drive mechanism of a machine tool. [Figure 4] FIG. 2 illustrates an example of a hardware configuration of a control unit. [Figure 5] It is a diagram showing a state where a pinion cutter is performing tooth cutting on a workpiece. [Figure 6] It is a diagram showing the machining mode in the C-XY mode from the Z-axis direction. [Figure 7] It is a diagram showing the machining mode in the C-XY mode from the X-axis direction. [Figure 8] It is a diagram showing the machining mode in the C-CE mode from the Z-axis direction. [Figure 9] It is a diagram for explaining the reciprocating drive process of the tool spindle during tooth cutting. [Figure 10] It is a diagram showing a state where the pinion cutter is being driven obliquely. [Figure 11] It is a flowchart showing the flow of the machining process in the C-XY mode. [Figure 12] It is a diagram schematically showing the flow of the machining mode in the C-XY mode. [Figure 13] It is a flowchart showing the flow of the machining process in the C-CE mode. [Figure 14] It is a diagram schematically showing the flow of the machining mode in the C-CE mode. [Figure 15] It is a diagram showing the machining mode in the C-XY mode according to a modification from the Z-axis direction.

Embodiments for Carrying out the Invention

[0021] Hereinafter, each embodiment according to the present invention will be described while referring to the drawings. In the following description, the same parts and components are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed descriptions thereof will not be repeated. In addition, each embodiment and each modification described below may be selectively combined as appropriate.

[0022] <A. Machine Tool 100> First, referring to FIG. 1, the machine tool 100 according to the first embodiment will be described. FIG. 1 is a diagram showing the external appearance of the machine tool 100.

[0023] The term "machine tool" as used in this specification is a concept that encompasses various devices that have the function of machining a workpiece. The machine tool 100 may be a horizontal machining center or a vertical machining center. Alternatively, the machine tool 100 may be a cutting machine, a grinding machine, a multi-tasking machine, a five-axis machine, or the like. Furthermore, the machine tool 100 is not limited to one that performs only subtractive machining. The machine tool 100 may also perform additive machining in addition to subtractive machining.

[0024] The machine tool 100 has a tool storage area AR1 and a processing area AR2. The tool storage area AR1 and the processing area AR2 are partitioned by a cover 130.

[0025] The tool storage area AR1 is provided with a magazine 5 and an ATC (Automatic Tool Changer) 6. The machining area AR2 is provided with a tool spindle 30 as an example of a tool holding section 20.

[0026] The tool spindle 30 machines a workpiece using at least one of a plurality of tools held in the magazine 5. More specifically, the machine tool 100 drives the magazine 5 to move a tool corresponding to the machining process (hereinafter also referred to as the "next tool to be used") to a first tool change position. The machine tool 100 also drives the tool spindle 30 to move a tool attached to the tool spindle 30 (hereinafter also referred to as the "used tool") to a second tool change position. The ATC 6 then replaces the next tool to be used, which is waiting at the first tool change position, with the used tool, which is waiting at the second tool change position. The tool change is performed via a door D provided as a partition between the machining area AR2 and the tool storage area AR1. The door D is a sliding door that is opened and closed by a drive source such as a motor. The tool spindle 30 then machines the workpiece using the attached next tool to be used.

[0027] Further, the machine tool 100 is provided with an operation panel 400. The operation panel 400 includes a display 405 for displaying various information related to machining, and operation keys 406 for receiving various operations on the machine tool 100.

[0028] <B. Device Configuration of Machine Tool 100> Next, referring to FIG. 2, the device configuration of the machine tool 100 will be described. FIG. 2 is a diagram showing an example of the device configuration of the machine tool 100.

[0029] The machine tool 100 includes a bed 11, a workpiece spindle 22, an opposing workpiece spindle 27, and a tool spindle 30.

[0030] For the sake of convenience of explanation, hereinafter, the direction parallel to the rotational axis direction of the workpiece spindle 22 is also referred to as the "Z-axis direction". Also, one direction on the horizontal plane orthogonal to the Z-axis direction is also referred to as the "Y-axis direction". The direction orthogonal to both the Y-axis direction and the Z-axis direction is referred to as the "X-axis direction". In the example of FIG. 2, the X-axis direction corresponds to the direction of gravity.

[0031] Furthermore, the direction along the rotational axis direction of the workpiece spindle 22 is referred to as the "rotational axis C" (first axis). The rotational axis C is parallel to the Z-axis direction and is also the rotational axis of the opposing workpiece spindle 27. Also, the direction along the rotational axis direction of the tool spindle 30 is referred to as the "rotational axis CE" (second axis). The rotational axis CE of the tool spindle 30 is also the rotational axis of the tool T attached to the tool spindle 30. The direction of the rotational axis CE changes with the swing drive of the tool spindle 30.

[0032] The bed 11 is a base member for supporting various devices provided inside the machine tool 100. In the example of FIG. 2, the bed 11 supports the workpiece spindle 22, the opposing workpiece spindle 27, and the tool spindle 30. The bed 11 is installed on the floor surface of a factory or the like. The bed 11 is formed of a metal such as cast iron.

[0033] The work spindle 22 is configured to be rotatable while holding the workpiece W. More specifically, the work spindle 22 is provided with a first chuck mechanism 23. The first chuck mechanism 23 is a mechanism for fixing the workpiece W to the work spindle 22. The work spindle 22 is also configured to be rotatable about a rotation axis C.

[0034] The counter work spindle 27 rotates the workpiece W while supporting it from the side opposite to the workpiece spindle 22. More specifically, the counter work spindle 27 is configured to be movable in the Z-axis direction by various drive mechanisms such as a motor, and can support the workpiece W from the side opposite to the workpiece spindle 22. In addition, the counter work spindle 27 is provided with a second chuck mechanism 28. The second chuck mechanism 28 is a mechanism for fixing the workpiece W to the counter work spindle 27. Furthermore, the counter work spindle 27 is configured to be rotatable about a rotation axis C.

[0035] The tool spindle 30 is located at a higher position than the workpiece spindle 22 and the counter workpiece spindle 27. The tool spindle 30 is configured to be able to hold a tool T, and rotatably holds the tool spindle 30 about a rotation axis CE. The tool spindle 30 is configured to be able to move in the X-axis, Y-axis, and Z-axis directions by various drive mechanisms such as a motor. The tool spindle 30 is also configured to be able to turn by various drive mechanisms such as a motor. As an example, the tool spindle 30 is configured to be able to rotate around the B-axis, which is centered about the Y-axis.

[0036] Various types of tools T can be mounted on the tool spindle 30 according to the machining mode. The tool T is mounted on the tool spindle 30 by the above-described ATC6. The tool spindle 30 performs cutting machining by bringing the tool T into contact with the workpiece W fixed to the workpiece spindle 22. As an example, the tool T is a pinion cutter TC described later. The tool T as a pinion cutter performs tooth cutting on the outer peripheral surface or the inner peripheral surface of the workpiece W to form a gear. The pinion cutter TC is, for example, stored in the magazine 5. When the machine tool 100 performs tooth cutting on the workpiece W, the machine tool 100 calls the pinion cutter TC stored in the magazine 5 and mounts the pinion cutter TC on the tool spindle 30 via the ATC6.

[0037] <C. Drive mechanism of the machine tool 100> Next, referring to FIG. 3, the drive mechanism in the machine tool 100 will be described. FIG. 3 is a diagram showing an example of the drive mechanism of the machine tool 100.

[0038] As shown in FIG. 3, the machine tool 100 includes the above-described workpiece spindle 22, the above-described opposed workpiece spindle θ27, the above-described tool spindle 30, a control unit 50, a rotational drive unit 210 (first rotational drive unit), a feed drive unit 220, a feed drive unit 230A, a rotational drive unit 230B (third rotational drive unit), and a rotational drive unit 230C (second rotational drive unit).

[0039] The control unit 50 controls various devices constituting the machine tool 100. As an example, the control unit 50 controls the rotational drive unit 210, the feed drive unit 220, the feed drive unit 230A, the rotational drive unit 230B, and the rotational drive unit 230C. Further, the control unit 50 controls a brake mechanism (for example, the brake mechanisms BC and BCE described later) for various drive mechanisms of the machine tool 100.

[0040] The control unit 50 may have any configuration. The control unit 50 may be configured with a single control unit or multiple control units. As an example, the control unit 50 includes at least one of a CNC (Computer Numerical Control) and a PLC (Programmable Logic Controller).

[0041] The rotation drive unit 210 is a drive mechanism for driving the work spindle 22 to rotate about a rotation axis C (see FIG. 2). In the example of FIG. 3, the rotation drive unit 210 is made up of a motor driver 211C, a motor 212C, and a brake mechanism BC.

[0042] The motor driver 211C sequentially receives input of the target rotation angle or target rotation speed of the work spindle 22 from the control unit 50, and outputs a current corresponding to the target rotation angle or target rotation speed to the motor 212C. This causes the work held by the work spindle 22 to rotate about the rotation axis C. The motor 212C may be an AC motor, a stepping motor, a servo motor, or any other type of motor.

[0043] The motor 212C is provided with a brake mechanism BC for braking the rotation of the workpiece spindle 22 around the rotation axis C. The brake mechanism BC is, for example, an electromagnetic brake, an electromagnetic clutch, or other hardware mechanism capable of preventing the rotational drive of the motor 212C. The control unit 50 outputs a control command to the brake mechanism BC to control clamping / unclamping of the rotation shaft of the motor 212C. As an example, the control unit 50 clamps the rotation shaft of the motor 212C by outputting an ON command to the brake mechanism BC, and unclamps the rotation shaft of the motor 212C by outputting an OFF command to the brake mechanism BC.

[0044] The feed drive unit 220 is a drive mechanism for driving the opposing workpiece spindle 27 to feed. The feed drive unit 220 may be composed of a single drive unit or multiple drive units. In the example of Fig. 3, the feed drive unit 220 is composed of a motor driver 221Z and a motor 222Z.

[0045] The motor driver 221Z sequentially receives input of target positions for the counter work spindle 27 from the control unit 50 and outputs a current corresponding to the target positions to the motor 222Z. This causes the motor 222Z to move the counter work spindle 27 to any position in the Z-axis direction. The motor 222Z may be an AC motor, a stepping motor, a servo motor, or any other type of motor.

[0046] The feed drive unit 230A is a drive mechanism for moving the tool spindle 30. The feed drive unit 230A may be composed of a single drive unit or multiple drive units. In the example of Fig. 3, the feed drive unit 230A is composed of motor drivers 231X to 231Z and motors 232X to 232Z.

[0047] The motor driver 231X sequentially receives input of target positions of the tool spindle 30 in the X-axis direction from the control unit 50, and outputs a current corresponding to the target positions to the motor 232X. As a result, the motor 232X drives the tool spindle 30 to any position in the X-axis direction. The motor 232X may be an AC motor, a stepping motor, a servo motor, or any other type of motor.

[0048] The motor driver 231Y sequentially receives input of target positions of the tool spindle 30 in the Y-axis direction from the control unit 50, and outputs a current corresponding to the target positions to the motor 232Y. In this way, the motor 232Y drives the tool spindle 30 to any position in the Y-axis direction. The motor 232Y may be an AC motor, a stepping motor, a servo motor, or any other type of motor.

[0049] The motor driver 231Z sequentially receives input of target positions of the tool spindle 30 in the Z-axis direction from the control unit 50, and outputs a current corresponding to the target positions to the motor 232Z. This causes the motor 232Z to move the tool spindle 30 to any position in the Z-axis direction. The motor 232Z may be an AC motor, a stepping motor, a servo motor, or any other type of motor.

[0050] The rotation drive unit 230B is a drive mechanism for driving the tool spindle 30 to rotate around an axis perpendicular to the rotation axis CE. The rotation drive unit 230B may be composed of a single drive unit or multiple drive units. In the example of Fig. 3, the rotation drive unit 230B is composed of a motor driver 231B and a motor 232B.

[0051] The motor driver 231B sequentially receives input of a target rotation angle or a target rotation speed of the tool spindle 30 centered around the Y-axis direction from the control unit 50, and outputs a current corresponding to the target rotation angle or the target rotation speed to the motor 232B. The motor 232B drives the tool spindle 30 to rotate around the B-axis centered around the Y-axis direction. The motor 232B may be an AC motor, a stepping motor, a servo motor, or any other type of motor.

[0052] The rotation drive unit 230C is a drive mechanism for driving the tool spindle 30 to rotate about a rotation axis CE (see FIG. 2). In the example of FIG. 3, the rotation drive unit 230C is made up of a motor driver 231C, a motor 232C, and a brake mechanism BCE.

[0053] The motor driver 231C sequentially receives from the control unit 50 an input of the target rotation angle or the target rotation speed of the tool spindle 30, and outputs a current corresponding to the target rotation angle or the target rotation speed to the motor 232C. The motor 232C rotationally drives the tool spindle 30 with the rotation axis CE as the rotation center. The motor 232C may be an AC motor, a stepping motor, a servo motor, or other types of motors.

[0054] The motor 232C is provided with a brake mechanism BCE for braking the rotation of the tool spindle 30 around the rotation axis CE. The brake mechanism BCE is, for example, an electromagnetic brake, an electromagnetic clutch, or other hardware mechanisms capable of preventing the rotational drive of the motor 232C. The control unit 50 outputs a control command to the brake mechanism BCE to control the clamping / unclamping of the rotation axis of the motor 232C. As an example, the control unit 50 clamps the rotation axis of the motor 232C by outputting an on command to the brake mechanism BCE, and unclamps the rotation axis of the motor 232C by outputting an off command to the brake mechanism BCE.

[0055] <D. Hardware Configuration of Control Unit 50> Next, referring to FIG. 4, the hardware configuration of the control unit shown in FIG. 3 described above will be described. FIG. 4 is a diagram showing an example of the hardware configuration of the control unit 50.

[0056] The control unit 50 includes a control circuit 101, a ROM (Read Only Memory) 102, a RAM (Random Access Memory) 103, a communication interface 104, and an auxiliary storage device 120. These components are connected to an internal bus 109.

[0057] The control circuit 101 is configured, for example, by at least one integrated circuit. The integrated circuit may be configured, for example, by at least one CPU, at least one GPU (Graphics Processing Unit), at least one ASIC (Application Specific Integrated Circuit), at least one FPGA (Field Programmable Gate Array), or a combination thereof.

[0058] The control circuit 101 controls the operation of the control unit 50 by executing various programs such as a control program 122. Upon receiving an execution command for the control program 122, the control circuit 101 reads the control program 122 from the auxiliary storage device 120 or the ROM 102 to the RAM 103. The RAM 103 functions as a working memory and temporarily stores various data required for the execution of the control program 122.

[0059] The communication interface 104 is an interface for periodic communication with external devices using a field network, such as EtherCAT (registered trademark), EtherNet / IP (registered trademark), CC-Link (registered trademark), or CompoNet (registered trademark).

[0060] The auxiliary storage device 120 is a storage medium such as a hard disk or flash memory. The auxiliary storage device 120 stores a control program 122 and setting parameters 124. The setting parameters 124 are parameters referenced by the control program 122. Details of the setting parameters 124 will be described later.

[0061] The storage location of the control program 122 and the setting parameters 124 is not limited to the auxiliary storage device 120, but may be stored in a memory area (e.g., cache memory) of the control circuit 101, ROM 102, RAM 103, an external device (e.g., a server), etc.

[0062] Further, the control program 122 may be provided not as a single program but incorporated into a part of any program. In this case, various processes according to this embodiment are realized in cooperation with any program. Even a program that does not include such a part of the module does not deviate from the gist of the control program 122 according to this embodiment. Further, part or all of the functions provided by the control program 122 may be realized by dedicated hardware. Further, the control unit 50 may be configured in a form such as a so-called cloud service in which at least one server executes a part of the processing of the control program 122.

[0063] <E. Gear Cutting> In addition to milling in which the rotating tool T is brought into contact with the workpiece W fixed to the workpiece spindle 22, the machine tool 100 has a function of performing gear cutting on the workpiece W. A pinion cutter, which is a type of tool T, is used for gear cutting.

[0064] FIG. 5 is a diagram showing a state in which the pinion cutter TC is performing gear cutting on the workpiece W. In the example of FIG. 5, a cross section in the YZ plane of the cylindrical workpiece W is shown, and the pinion cutter TC is performing gear cutting on the inner peripheral surface of the workpiece W.

[0065] As described above, when the machine tool 100 performs gear cutting on the workpiece W, it calls the pinion cutter TC housed in the magazine 5 and mounts the pinion cutter TC on the tool spindle 30 via the ATC 6. Then, the machine tool 100 reciprocates the tool spindle 30 in the direction of the rotation axis CE with the rotation axis CE of the tool spindle 30 parallel to the rotation axis CE of the workpiece spindle 22, thereby performing gear cutting on the inner peripheral surface or the outer peripheral surface of the workpiece W. The gear cutting may be performed only on the forward stroke when the tool spindle 30 is reciprocated, or may be performed on both the forward stroke and the return stroke when the tool spindle 30 is reciprocated. [[ID=十七]]

[0066] The pinion cutter TC is composed of a main body TC1 and a plurality of tooth portions TC2. The plurality of tooth portions TC2 are formed at equal intervals on the outer peripheral surface of the main body TC1. Each of the plurality of tooth portions TC2 has a tooth tip TE, a rake face RF, and a flank FF.

[0067] The tooth tip TE is the portion that is pressed against the workpiece W. In other words, the tooth tip TE corresponds to the ridge portion where the rake face RF and the flank FF intersect.

[0068] 5 shows an acute-angled tooth tip TE, but the angle of the tooth tip TE does not necessarily have to be an acute angle. Also, the tooth tip TE does not necessarily have to be sharp, and may be rounded.

[0069] The rake face RF is one of the two faces extending from the tooth tip TE, and is the face that comes into contact with the workpiece W in the feed drive direction of the tool spindle 30. In other words, the rake face RF is the face along which chips from the workpiece W flow when the workpiece W is gear-cut.

[0070] The flank FF is the other of the two surfaces extending from the tooth tip TE. In other words, the flank FF is the surface extending from the tooth tip TE in a direction different from that of the rake face RF. The flank FF is a surface provided to reduce unnecessary wear with the workpiece surface.

[0071] Machine tool 100 according to the embodiment has a C-XY mode and a C-CE mode as machining modes related to gear cutting. Gear cutting in the C-XY mode and gear cutting in the C-CE mode will be described below in order.

[0072] Furthermore, the term "rotation" will be used hereinafter, and in this specification, "rotation" means rotation of the tool spindle 30 about the rotation axis C on a plane perpendicular to the rotation axis C (i.e., on the XY plane), or rotation of the tool spindle 30 about the rotation axis CE on a plane perpendicular to the rotation axis CE (i.e., on the XY plane). Note that, since the workpiece spindle 22 moves in conjunction with the workpiece W, the rotation of the workpiece spindle 22 is synonymous with the rotation of the workpiece W. Furthermore, since the tool spindle 30 moves in conjunction with the pinion cutter TC, the rotation of the tool spindle 30 is synonymous with the rotation of the pinion cutter TC.

[0073] Furthermore, the term "revolution" will be used below, but in this specification, "revolution" means the rotational movement of the tool spindle 30 about the rotational axis C on a plane perpendicular to the rotational axis C (i.e., on the XY plane). Since the tool spindle 30 is linked to the pinion cutter TC, the revolution of the tool spindle 30 is synonymous with the revolution of the pinion cutter TC. Furthermore, when the term "revolution" is used below, it does not necessarily mean a rotational movement of the entire circumference (one revolution) on the plane, but may also include a partial circular arc movement on the plane.

[0074] (E1.C-XY mode) First, gear cutting in the C-XY mode will be described with reference to Figures 6 and 7. Figure 6 is a diagram showing the cutting mode in the C-XY mode from the Z-axis direction. Figure 7 is a diagram showing the cutting mode in the C-XY mode from the X-axis direction.

[0075] First, the machine tool 100 controls the rotation drive unit 230B so that the rotation axis CE of the tool spindle 30 and the rotation axis C of the workpiece spindle 22 are parallel to each other. Next, the machine tool 100 moves the tool spindle 30 to a predetermined machining start position. The machining start position is defined in advance in the machining program, for example.

[0076] Next, the machine tool 100 performs gear cutting on the inner or outer surface of the workpiece W by driving the tool spindle 30 back and forth in the direction of the rotation axis C while the rotation axis C and the rotation axis CE are parallel. Hereinafter, this process will also be referred to as a "reciprocating drive process." In the reciprocating drive process, the tool spindle 30 is driven on the positive side of the Z axis direction and on the negative side of the Z axis direction. When the tool spindle 30 is driven on the positive side of the Z axis direction, the surface of the workpiece W is cut. Thereafter, the machine tool 100 drives the tool spindle 30 on the negative side of the Z axis direction while keeping a predetermined distance from the surface of the workpiece W.

[0077] Next, the machine tool 100 adjusts the position angle between the workpiece spindle 22 and the tool spindle 30. In the C-XY mode, the machine tool 100 rotates the workpiece spindle 22 by a predetermined angle about the rotation axis C, and moves the tool spindle 30 in an arc by a predetermined angle about the rotation axis C. The attitude of the tool spindle 30 does not change during the arc movement in the C-XY mode. In other words, the attitude of the tool spindle 30 is maintained during the arc movement in the C-XY mode. Hereinafter, the process of adjusting the position angle between the workpiece spindle 22 and the tool spindle 30 is also referred to as the "angle adjustment process."

[0078] The machine tool 100 repeatedly executes a reciprocating drive process and an angle adjustment process in sequence. As a result, the workpiece spindle 22 rotates about the rotation axis C, and the tool spindle 30 revolves about the rotation axis C. The reciprocating drive process and the angle adjustment process are repeatedly executed with the brake applied by the brake mechanism BCE described above. That is, in the C-XY mode, gear cutting is performed with the tool spindle 30 prevented from rotating about the rotation axis CE. As a result, gear cutting is continuously performed on the outer or inner peripheral surface of the workpiece W, and the machine tool 100 can form a gear from the workpiece W.

[0079] As described above, in the C-XY mode, gear cutting of the workpiece W is achieved without rotating the tool spindle 30. This has the following advantages. In cutting the workpiece W, the rotation speed of the tool spindle 30 is important, so the accuracy of reading the rotation angle of the tool spindle 30 is often not required. Therefore, depending on the machine tool, the accuracy of the encoder used to read the rotation angle of the tool spindle 30 may be low. In contrast, in the C-XY mode, the machine tool 100 does not rotate the tool spindle 30, so it is not affected by the accuracy of the encoder. As a result, the accuracy of the gear cutting is improved.

[0080] In addition, in C-XY mode, gear cutting is performed with the brake mechanism BCE always on, which reduces the number of times the brake mechanism BCE is turned on and off, shortening the processing time.

[0081] Furthermore, machine tool 100 performs gear cutting on workpiece W with the rotation axis CE of tool spindle 30 physically fixed by brake mechanism BCE. This prevents tool spindle 30 from rotating due to cutting resistance. Therefore, machine tool 100 can move tool spindle 30 at high speed in the direction of rotation axis CE, allowing workpiece W to be cut smoothly.

[0082] Although Figures 6 and 7 show an example in which machine tool 100 performs gear cutting on the inner surface of workpiece W, machine tool 100 may also be configured to perform gear cutting on the outer surface of workpiece W.

[0083] Preferably, machine tool 100 appropriately switches on and off brake mechanism BC associated with rotation axis C of workpiece spindle 22. More specifically, machine tool 100 turns on brake mechanism BC between the completion of the angle adjustment process and the start of the reciprocating drive process, thereby disabling workpiece spindle 22 from rotating on its own axis. Thereafter, machine tool 100 executes the reciprocating drive process.

[0084] Next, machine tool 100 turns off brake mechanism BC between the completion of the reciprocating drive process and the start of the angle adjustment process, thereby enabling workpiece spindle 22 to rotate on its own axis. Thereafter, machine tool 100 executes angle adjustment process to rotate workpiece spindle 22 by a predetermined angle on its own axis.

[0085] (E2.C-CE mode) Next, gear cutting in the C-CE mode will be described with reference to Fig. 8. Fig. 8 is a diagram showing the cutting mode in the C-CE mode from the Z-axis direction.

[0086] In the above-described C-XY mode, during the angle adjustment process, the machine tool 100 rotates the workpiece spindle 22 while revolving the tool spindle 30. In contrast, in the C-CE mode, during the angle adjustment process, the machine tool 100 rotates both the tool spindle 30 and the workpiece spindle 22 without revolving the tool spindle 30.

[0087] Furthermore, in the above-described C-XY mode, machine tool 100 performs gear cutting with brake mechanism BCE always turned on. In contrast, in C-CE mode, machine tool 100 turns brake mechanism BCE off during angle adjustment processing, allowing tool spindle 30 to rotate. Then, machine tool 100 performs reciprocating drive processing with brake mechanism BCE turned on. In this way, in C-CE mode, machine tool 100 repeatedly turns brake mechanism BCE on and off.

[0088] As a more specific process, machine tool 100 first controls the above-mentioned rotation drive unit 230B so that the rotation axis CE of tool spindle 30 and the rotation axis C of workpiece spindle 22 are parallel to each other. Next, machine tool 100 moves tool spindle 30 to a machining start position on the XY plane. This machining start position is defined in advance in a machining program or the like.

[0089] Next, the machine tool 100 turns on the brake mechanism BCE to prevent the tool spindle 30 from rotating on its axis. Thereafter, the machine tool 100 executes a process (i.e., a reciprocating drive process) in which the tool spindle 30 is driven reciprocally in the direction of the rotation axis C while maintaining the rotation axes C and CE parallel to each other. In the reciprocating drive process, the tool spindle 30 is driven on the positive side of the Z axis direction and on the negative side of the Z axis direction. When the tool spindle 30 is driven on the positive side of the Z axis direction, the surface of the workpiece W is ground. Thereafter, the machine tool 100 drives the tool spindle 30 on the negative side of the Z axis direction while keeping a predetermined distance from the surface of the workpiece W.

[0090] Next, machine tool 100 turns off brake mechanism BCE to enable the tool spindle 30 to rotate on its own axis. Thereafter, machine tool 100 executes a process to rotate tool spindle 30 by a predetermined angle about rotation axis CE (i.e., an angle adjustment process).

[0091] The machine tool 100 sequentially and repeatedly executes the reciprocating drive process and the angle adjustment process. In this way, in the C-CE mode, the machine tool 100 performs gear cutting on the workpiece W by rotating both the workpiece spindle 22 and the tool spindle 30 on their axes without revolving the tool spindle 30. That is, in the C-CE mode, the position of the tool spindle 30 on the XY plane when performing gear cutting is the same or approximately the same. Therefore, the machine tool 100 can perform gear cutting on the workpiece W even when the drive range of the tool spindle 30 on the XY plane is limited. This type of processing is particularly advantageous when performing gear cutting on the outer peripheral surface of the workpiece W.

[0092] Furthermore, the machine tool 100 performs gear cutting on the workpiece W with the rotation axis CE of the tool spindle 30 physically fixed by the brake mechanism BCE. This prevents the tool spindle 30 from rotating due to cutting resistance. Therefore, the machine tool 100 can move the tool spindle 30 at high speed in the direction of the rotation axis CE, allowing the workpiece W to be cut smoothly.

[0093] Note that although FIG. 8 shows an example in which the machine tool 100 performs tooth cutting on the inner peripheral surface of the workpiece W, the machine tool 100 may be configured to perform tooth cutting on the outer peripheral surface of the workpiece W.

[0094] Preferably, the machine tool 100 not only turns on and off the brake mechanism BCE related to the tool spindle 30, but also appropriately switches the on and off of the brake mechanism BC related to the rotation axis C of the workpiece spindle 22. More specifically, the machine tool 100 turns on the brake mechanisms BC and BCE between the completion of the execution of the angle adjustment process and the start of the execution of the reciprocating drive process, and makes the workpiece spindle 22 and the tool spindle 30 non-rotatable. Thereafter, the machine tool 100 executes a reciprocating drive process.

[0095] Next, the machine tool 100 turns off the brake mechanisms BC and BCE between the completion of the execution of the reciprocating drive process and the start of the execution of the angle adjustment process, and makes the workpiece spindle 22 and the tool spindle 30 rotatable. Thereafter, the machine tool 100 executes an angle adjustment process in which the tool spindle 30 is rotated by a predetermined angle while the workpiece spindle 22 is rotated by a predetermined angle.

[0096] <F. Temperature Monitoring Process> Next, the temperature monitoring process of the machine tool 100 will be described.

[0097] As described above, the machine tool 100 realizes the tooth cutting of the workpiece W by repeating the reciprocating drive process and the angle adjustment process in order. When the tool spindle 30 is repeatedly reciprocally driven in the direction of the rotation axis CE in the reciprocating drive process, the temperature of the drive system related to the tool spindle 30 rises. Therefore, the machine tool 100 monitors the temperature of the drive system related to the tool spindle 30, and executes an abnormality handling process based on the fact that the temperature has reached a predetermined temperature or higher.

[0098] The drive system to be temperature-monitored may be, for example, the above-described motor 232Z (see FIG. 3) for driving the tool spindle 30 in the direction of the rotation axis CE, or a ball screw (not shown) driven by the motor 232Z.

[0099] Various methods can be used to detect the temperature of the drive system associated with the tool spindle 30.

[0100] As an example, the temperature of the drive system for the tool spindle 30 is detected using a temperature sensor (not shown). The temperature sensor is provided in the drive system whose temperature is to be monitored. The machine tool 100 periodically acquires the temperature detected by the temperature sensor, and executes an abnormality handling process when the temperature exceeds a predetermined value.

[0101] As another example, the temperature of the drive system associated with the tool spindle 30 is estimated using a trained model that has learned the correlation between the machining conditions of the workpiece W and the temperature of the drive system associated with the tool spindle 30. The trained model is generated by a predetermined machine learning process using a training dataset. Various machine learning algorithms can be used as the learning method for generating the trained model. Examples of machine learning algorithms include deep learning and support vector machines.

[0102] Each piece of learning data included in the learning dataset corresponds to the machining conditions of the workpiece W as explanatory variables and the temperature of the drive system for the tool spindle 30 as a response variable. Examples of the machining conditions that are explanatory variables include the feed rate of the tool spindle 30 at each time in the direction of the rotation axis CE and the number of reciprocating movements of the tool spindle 30 per unit time.

[0103] The machine tool 100 acquires the current machining conditions and inputs them into the trained model. As a result, the machine tool 100 acquires the temperature of the drive system related to the tool spindle 30 from the trained model. The machine tool 100 executes an abnormality handling process when the estimated temperature reaches or exceeds a predetermined value.

[0104] The abnormality handling process may include various processes, such as stopping the machining of the workpiece W.

[0105] As another example, the abnormality handling process includes a process of notifying that the temperature of the drive system of the tool spindle 30 has reached or exceeded a predetermined value. This notification process is realized, for example, by displaying a message indicating the occurrence of an abnormality on the above-described display 405 (see FIG. 1). Alternatively, this notification process is realized by lighting an abnormality lamp (not shown) provided on the machine tool 100.

[0106] Based on the fact that the temperature of the drive system related to the tool spindle 30 has fallen below a predetermined value, the machine tool 100 stops the execution of the abnormality handling process. Thereby, the machine tool 100 resumes the machining of the workpiece W or cancels the warning notification.

[0107] <G. Setting Parameter 124> Next, referring to FIGS. 9 and 10, the above-described setting parameter 124 (see FIG. 4) will be described.

[0108] The machine tool 100 executes gear cutting in the C-XY mode or the C-CE mode according to the setting parameter 124. The setting parameter 124 may be set in advance by the user or may be set in advance at the time of designing the machining program.

[0109] There are various setting parameters 124 that can be set. Hereinafter, examples of the setting parameter 124 that can be set will be described.

[0110] (G1. Specific Example 1 of Setting Parameter 124) The setting parameter 124 includes a parameter for specifying whether to enable the brake by the brake mechanism BCE in the C-XY mode. As described above, the brake mechanism BCE applies a brake to the rotation of the tool spindle 30 centered on the rotation axis CE.

[0111] When the brake mechanism BCE is set to be enabled in the setting parameters 124, the machine tool 100 executes the reciprocating drive process and the angle adjustment process while enabling the brake. That is, in this case, as described in Fig. 6, the brake mechanism BCE prohibits the tool spindle 30 from rotating on its own axis.

[0112] On the other hand, if braking by brake mechanism BCE is set to disabled in setting parameters 124, machine tool 100 always keeps brake mechanism BCE off. In this case, machine tool 100 maintains the rotation angle of tool spindle 30 by utilizing the holding force of motor 232C (see FIG. 3) serving as a servo motor.

[0113] More specifically, during reciprocating drive processing, machine tool 100 inputs a target rotation angle of tool spindle 30 to motor driver 231C (see FIG. 3). Motor driver 231C calculates the actual rotation angle of motor 232C from a feedback signal of an encoder (not shown) that detects the rotation angle of motor 232C. Then, motor driver 231C controls the rotation angle of motor 232C so that the calculated actual rotation angle approaches the target rotation angle. In this way, motor driver 231C sequentially receives feedback of the rotation angle of motor 232C, and causes the rotation angle of motor 232C to approach the target rotation angle. As a result, the rotation angle of motor 232C is maintained constant during reciprocating drive processing.

[0114] As another example, the setting parameters 124 include a parameter for specifying whether or not to enable braking by the brake mechanism BC in the C-XY mode. As described above, the brake mechanism BC applies a brake to the rotation of the workpiece spindle 22 about the rotation axis C.

[0115] When braking by brake mechanism BC is set to be enabled in setting parameters 124, machine tool 100 sequentially switches on and off brake mechanism BC. That is, in this case, as described above, the reciprocating drive process is executed with brake mechanism BC in an on state, and the angle adjustment process is executed with brake mechanism BC in an off state.

[0116] On the other hand, if the braking by brake mechanism BC is set to be disabled in setting parameter 124, machine tool 100 keeps brake mechanism BC off at all times. In this case, machine tool 100 uses the holding force of motor 212C (see FIG. 3) serving as a servo motor to suppress the rotation of workpiece spindle 22.

[0117] The holding force of motor 212C may be set for general machining. When performing machining in C-XY mode with the brake provided by brake mechanism BC disabled, machine tool 100 may perform machining in C-XY mode with a holding force different from that used for general machining. The holding force is optimized, for example, by adjusting gain parameters related to control of workpiece spindle 22. This minimizes angle changes when workpiece spindle 22 receives a cutting load.

[0118] More specifically, during reciprocating drive processing, machine tool 100 inputs the target rotation angle of workpiece spindle 22 to motor driver 211C (see FIG. 3). Motor driver 211C calculates the actual rotation angle of motor 212C from a feedback signal of an encoder (not shown) that detects the rotation angle of motor 212C. Then, motor driver 211C controls the rotation angle of motor 212C so that the calculated actual rotation angle approaches the target rotation angle. In this way, motor driver 211C sequentially receives feedback of the rotation angle of motor 212C and brings the rotation angle of motor 212C closer to the target rotation angle. As a result, the rotation angle of motor 212C is maintained constant during reciprocating drive processing.

[0119] (G2. Example 2 of setting parameter 124) Next, another example of the setting parameters 124 will be described.

[0120] In this example, the setting parameters 124 include a parameter for specifying whether or not to enable braking by the brake mechanism BCE in the C-CE mode. As described above, the brake mechanism BCE applies a brake to the rotation of the tool spindle 30 about the rotation axis CE.

[0121] When braking by brake mechanism BCE is set to be enabled in setting parameter 124, machine tool 100 sequentially switches on and off brake mechanism BCE. That is, in this case, as explained above, the reciprocating drive process is executed with brake mechanism BCE in an on state, and the angle adjustment process is executed with brake mechanism BCE in an off state.

[0122] On the other hand, if braking by brake mechanism BCE is set to disabled in setting parameter 124, machine tool 100 always keeps brake mechanism BCE off. In this case, machine tool 100 suppresses the rotation of tool spindle 30 by utilizing the holding force of motor 232C (see FIG. 3) serving as a servo motor.

[0123] More specifically, during reciprocating drive processing, machine tool 100 inputs a target rotation angle of tool spindle 30 to motor driver 231C (see FIG. 3). Motor driver 231C calculates the actual rotation angle of motor 232C from a feedback signal of an encoder (not shown) that detects the rotation angle of motor 232C. Then, motor driver 231C controls the rotation angle of motor 232C so that the calculated actual rotation angle approaches the target rotation angle. In this way, motor driver 231C sequentially receives feedback of the rotation angle of motor 232C, and causes the rotation angle of motor 232C to approach the target rotation angle. As a result, the rotation angle of motor 232C is maintained constant during reciprocating drive processing.

[0124] As another example, the setting parameters 124 include a parameter for specifying whether or not to enable braking by the brake mechanism BC in the C-CE mode. As described above, the brake mechanism BC applies a brake to the rotation of the workpiece spindle 22 about the rotation axis C.

[0125] When braking by brake mechanism BC is set to be enabled in setting parameters 124, machine tool 100 sequentially switches on and off brake mechanism BC. That is, in this case, as described above, the reciprocating drive process is executed with brake mechanism BC in an on state, and the angle adjustment process is executed with brake mechanism BC in an off state.

[0126] On the other hand, if the braking by brake mechanism BC is set to be disabled in setting parameter 124, machine tool 100 keeps brake mechanism BC off at all times. In this case, machine tool 100 uses the holding force of motor 212C (see FIG. 3) serving as a servo motor to suppress the rotation of workpiece spindle 22.

[0127] More specifically, during reciprocating drive processing, machine tool 100 inputs the target rotation angle of workpiece spindle 22 to motor driver 211C (see FIG. 3). Motor driver 211C calculates the actual rotation angle of motor 212C from a feedback signal of an encoder (not shown) that detects the rotation angle of motor 212C. Then, motor driver 211C controls the rotation angle of motor 212C so that the calculated actual rotation angle approaches the target rotation angle. In this way, motor driver 211C sequentially receives feedback of the rotation angle of motor 212C and brings the rotation angle of motor 212C closer to the target rotation angle. As a result, the rotation angle of motor 212C is maintained constant during reciprocating drive processing.

[0128] (G3. Example 3 of setting parameter 124) Next, another example of the setting parameters 124 will be described with reference to Fig. 9. Fig. 9 is a diagram for explaining the reciprocating drive process of the tool spindle 30 during gear cutting. Note that in Fig. 9, the tool spindle 30 is omitted from the illustration, and only the pinion cutter TC is shown.

[0129] During the reciprocating drive process, the tool spindle 30 is driven to reciprocate between a position "z1" (first position) in the direction of the rotation axis C and a position "z2" (second position) in the direction of the rotation axis C. The position "z1" is a position that is a predetermined distance ΔD1 (first distance) away from a surface SF1 on one side of the workpiece W in the direction of the rotation axis C. The position "z2" is a position that is a predetermined distance ΔD2 (second distance) away from a surface SF2 on the other side of the workpiece W in the direction of the rotation axis C.

[0130] To stabilize gear cutting, the machine tool 100 needs to maintain the feed rate of the pinion cutter TC constant at a target rate while the pinion cutter TC is cutting the workpiece W. Meanwhile, the feed rate of the tool spindle 30 gradually changes toward the target rate.

[0131] Therefore, the machine tool 100 sets the start point of the reciprocating drive process to a position "z1" that is a predetermined distance ΔD1 away from one surface SF1 of the workpiece W in the direction of the rotation axis C. The predetermined distance ΔD1 indicates the distance in the Z-axis direction between the workpiece surface SF1 and the tooth tip of the pinion cutter TC. The setting parameters 124 described above include this predetermined distance ΔD1. The predetermined distance ΔD1 is, for example, several mm to several cm.

[0132] Furthermore, the machine tool 100 sets the end point of the reciprocating drive process to a position "z2" that is a predetermined distance ΔD2 away from the surface SF2 on the other side of the workpiece W in the direction of the rotation axis C. The predetermined distance ΔD2 indicates the distance in the Z-axis direction between the surface SF2 of the workpiece and the tooth tip of the pinion cutter TC. The setting parameters 124 described above include the predetermined distance ΔD2. The predetermined distance ΔD2 is, for example, several mm to several cm. The predetermined distance ΔD2 may be the same as the predetermined distance ΔD1, or may be different from the predetermined distance ΔD1.

[0133] By providing the predetermined distance ΔD1 as the run-up distance, the machine tool 100 can set the feed rate of the tool spindle 30 to the target rate before contact with the workpiece W. On the other hand, by providing the predetermined distance ΔD2, the machine tool 100 can prevent the feed rate of the tool spindle 30 from being reduced before the pinion cutter TC has left the workpiece W.

[0134] The distances ΔD1 and ΔD2 may be the setting parameters 124 referenced in the above-mentioned C-XY mode, or may be the setting parameters 124 referenced in the above-mentioned C-CE mode.

[0135] Furthermore, in the above description, the distances ΔD1 and ΔD2 have been described as an example of the setting parameters 124, but the positions "z1" and "z2" may also be set as the setting parameters 124.

[0136] (G4. Example 4 of setting parameter 124) Next, another example of the setting parameters 124 will be described.

[0137] As explained in Fig. 6, in the C-XY mode, the tool spindle 30 is driven to revolve around the rotation axis C. At this time, the central coordinates of the workpiece W may be shifted due to thermal displacement or the like. Therefore, the setting parameters 124 include a correction value related to the center of revolution of the tool spindle 30 during the angle adjustment process.

[0138] Machine tool 100 corrects the center of rotation on the XY plane based on the correction value, and controls the above-mentioned feed drive unit 230A (see FIG. 3) so that tool spindle 30 revolves around the corrected center.

[0139] As an example, the correction value includes an offset value "ΔX" in the X-axis direction and an offset value "ΔY" in the Y-axis direction. In this case, the rotation center in the X-axis direction is shifted by "ΔX" from a preset value, and the rotation center in the Y-axis direction is shifted by "ΔY" from a preset value.

[0140] (G5. Example 5 of setting parameter 124) Next, still another example of the setting parameters 124 will be described with reference to Fig. 10. Fig. 10 is a diagram showing a state in which the pinion cutter TC is driven to feed obliquely.

[0141] As described above, in the reciprocating drive process in the C-XY mode and C-CE mode, the machine tool 100 reciprocates the tool spindle 30 with the rotation axis C and the rotation axis CE parallel to each other. At this time, the pinion cutter TC receives cutting resistance from the surface of the workpiece W. The cutting resistance is a force that the pinion cutter TC receives when cutting the workpiece W. If the pinion cutter TC is driven in a feed state while receiving cutting resistance, the trajectory of the pinion cutter TC may deviate from the original trajectory.

[0142] In this case, the trajectory of the pinion cutter TC deviates in the opposite direction to the cutting direction into the workpiece W. The cutting direction is the direction from the rotation axis C, CE toward the contact point between the workpiece W and the pinion cutter TC on a plane perpendicular to the rotation axes C, CE (i.e., on the XY plane). In other words, the cutting direction is the direction from the rotation axis C toward the rotation axis CE on a plane perpendicular to the rotation axes C, CE (i.e., on the XY plane).

[0143] The trajectory of the pinion cutter TC may deviate in the direction opposite to the cutting direction during reciprocating drive processing. Therefore, the setting parameters 124 include a parameter for specifying whether or not the feed drive direction of the tool spindle 30 when cutting the workpiece W should be tilted in the cutting direction of the workpiece W.

[0144] Preferably, the parameter specifies the degree of tilting the workpiece W in the cutting direction. The degree is specified by, for example, the tilt angle Δθ or the distance ΔD3 shown in FIG.

[0145] The tilt angle Δθ is the tilt angle with respect to the rotation axes C and CE. When driving the tool spindle 30 during the reciprocating drive process, the machine tool 100 tilts the feed drive direction by the specified tilt angle Δθ. When the tilt angle Δθ is set to zero, the machine tool 100 drives the tool spindle 30 in the directions of the rotation axes C and CE.

[0146] The distance ΔD3 corresponds to the width by which the tool spindle 30 is displaced in the cutting direction when feeding and driving the tool spindle 30 from the above-mentioned position "z1" (see FIG. 9) to the above-mentioned position "z2" (see FIG. 9). When the distance ΔD3 is set to zero, the machine tool 100 drives the tool spindle 30 in the directions of the rotation axes C and CE.

[0147] <Control Flow in H.C-XY Mode> Next, referring to FIGS. 11 and 12, the control flow in C-XY mode will be described. FIG. 11 is a flowchart showing the flow of the machining process in the above-mentioned C-XY mode. FIG. 12 is a diagram schematically showing the flow of the machining mode in C-XY mode.

[0148] The processes shown in FIGS. 11 and 12 are realized, for example, when the control unit 50 of the machine tool 100 executes the above-mentioned control program 122. In other aspects, part or all of the processes may be executed by circuit elements or other hardware.

[0149] In step S112, the control unit 50 controls the above-mentioned rotational drive unit 230B so that the rotation axis C of the work spindle 22 and the rotation axis CE of the tool spindle 30 are parallel.

[0150] In step S114, the control unit 50 controls the feed drive unit 230A so as to drive the tool spindle 30 to a predetermined machining start position SP on the XY plane. The machining start position SP is defined in advance in a program such as the control program 122. The machining start position SP is defined, for example, so that the tip of the pinion cutter TC overlaps the machining surface of the work W when viewed from the direction of the rotation axis C or the rotation axis CE.

[0151] In step S116, the control unit 50 turns on the brake mechanism BCE (see FIG. 3) described above to lock the rotation axis CE of the tool spindle 30. This makes the tool spindle 30 unable to rotate on its own axis.

[0152] In step S118, the control unit 50 turns on the brake mechanism BC (see FIG. 3) described above to lock the rotation axis C of the work spindle 22. This puts the work spindle 22 in a state where it cannot rotate on its own axis.

[0153] In step S120, the control unit 50 controls the feed drive unit 230A to reciprocate the tool spindle 30 in the direction of the rotation axis C while the rotation axis C and the rotation axis CE are parallel to each other. More specifically, the control unit 50 first drives the tool spindle 30 in the positive direction of the Z axis to perform gear cutting on the surface of the workpiece W. Then, the control unit 50 moves the tool spindle 30 in the direction opposite to the cutting direction of the workpiece W. This causes the control unit 50 to retract the pinion cutter TC from the surface of the workpiece W. Then, the control unit 50 drives the tool spindle 30 in the negative direction of the Z axis while leaving a predetermined distance from the surface of the workpiece W. Then, the control unit 50 drives the tool spindle 30 in the cutting direction of the workpiece W by the distance corresponding to the retracted distance. This causes the control unit 50 to return the tool spindle 30 to the start position of the reciprocating drive process.

[0154] In step S122, the control unit 50 turns off the brake mechanism BC (see FIG. 3) described above, and unlocks the work spindle 22 from the rotation axis C. This allows the work spindle 22 to rotate on its own axis.

[0155] In step S124, the control unit 50 rotates the workpiece spindle 22 by a predetermined angle "Δθ1" around the rotation axis C, and rotates the tool spindle 30 by a predetermined angle "Δθ2" around the rotation axis C. At this time, the rotation direction of the workpiece spindle 22 is the same as the rotation direction of the tool spindle 30.

[0156] In the process of forming a gear on the inner peripheral surface of the workpiece W, the rotation angle "Δθ1" of the workpiece spindle 22 and the revolution angle "Δθ2" of the tool spindle 30 are synchronized based on the following formula (1).

[0157] Δθ1 = Δθ2·(1 - Nc / Nw) ··· (1) "Nc" shown in the above formula (1) indicates the number of teeth of the pinion cutter TC. "Nw" shown in the above formula (1) indicates the number of teeth formed on the inner peripheral surface of the workpiece W. "Nc" and "Nw" are fixed values, for example, defined in the above-mentioned setting parameter 124.

[0158] Also, in the process of forming a gear on the outer peripheral surface of the workpiece W, the rotation angle "Δθ1" of the workpiece spindle 22 and the revolution angle "Δθ2" of the tool spindle 30 are synchronized based on the following formula (2).

[0159] Δθ1 = Δθ2·(1 + Nc / Nw) ··· (2) "Nc" shown in the above formula (2) indicates the number of teeth of the pinion cutter TC. "Nw" shown in the above formula (2) indicates the number of teeth formed on the outer peripheral surface of the workpiece W. "Nc" and "Nw" are fixed values, for example, defined in the above-mentioned setting parameter 124.

[0160] In step S130, the control unit 50 determines whether to end the gear cutting process in the C-CX mode. As an example, based on the fact that the tool spindle 30 has revolved once around the rotation axis C, the control unit 5 determines to end the gear cutting process in the C-CX mode. Alternatively, based on the fact that the workpiece spindle 22 has rotated once, the control unit 50 determines to end the gear cutting process in the C-CX mode. If the control unit 50 determines to end the gear cutting process in the C-CX mode (YES in step S130), it ends the process shown in FIG. 11. Otherwise (NO in step S130), the control unit 50 returns the control to step S118.

[0161] <I.C-CE mode control flow> Next, the control flow in C-CE mode will be described with reference to Figures 13 and 14. Figure 13 is a flowchart showing the flow of processing in the above-mentioned C-CE mode. Figure 14 is a diagram showing a schematic flow of processing modes in C-CE mode.

[0162] 13 and 14 is realized, for example, by control unit 50 of machine tool 100 executing the above-described control program 122. In another aspect, some or all of the processes may be performed by circuit elements or other hardware.

[0163] In step S212, the control unit 50 controls the above-mentioned rotation drive unit 230B so that the rotation axis C of the workpiece spindle 22 and the rotation axis CE of the tool spindle 30 are parallel to each other.

[0164] In step S214, the control unit 50 controls the feed drive unit 230A to drive the tool spindle 30 to a predetermined machining start position SP on the XY plane. The machining start position SP is defined in advance in a program such as the control program 122. The machining start position SP is defined, for example, so that the tip of the pinion cutter TC overlaps with the machining surface of the workpiece W when viewed from the direction of the rotation axis C or the rotation axis CE.

[0165] In step S218, the control unit 50 turns on the brake mechanism BC (see FIG. 3) described above to lock the rotation axis C of the workpiece spindle 22. This prevents the workpiece spindle 22 from rotating on its own axis. The control unit 50 also turns on the brake mechanism BCE (see FIG. 3) described above to lock the rotation axis CE of the tool spindle 30. This prevents the tool spindle 30 from rotating on its own axis.

[0166] In step S220, the control unit 50 controls the feed drive unit 230A to reciprocate the tool spindle 30 in the direction of the rotation axis C while the rotation axis C and the rotation axis CE are parallel to each other. More specifically, the control unit 50 first drives the tool spindle 30 in the positive direction of the Z axis to perform gear cutting on the surface of the workpiece W. Then, the control unit 50 moves the tool spindle 30 in the direction opposite to the cutting direction of the workpiece W. This causes the control unit 50 to retract the pinion cutter TC from the surface of the workpiece W. Then, the control unit 50 drives the tool spindle 30 in the negative direction of the Z axis while leaving a predetermined distance from the surface of the workpiece W. Then, the control unit 50 drives the tool spindle 30 in the cutting direction of the workpiece W by the distance corresponding to the retracted distance. This causes the control unit 50 to return the tool spindle 30 to the start position of the reciprocating drive process.

[0167] In step S222, the control unit 50 turns off the brake mechanism BC (see FIG. 3) described above, and releases the lock on the rotation axis C of the workpiece spindle 22. This allows the workpiece spindle 22 to rotate on its own axis. The control unit 50 also turns off the brake mechanism BCE (see FIG. 3) described above, and releases the lock on the rotation axis CE of the tool spindle 30. This allows the tool spindle 30 to rotate on its own axis.

[0168] In step S224, the control unit 50 rotates the workpiece spindle 22 by a predetermined angle "Δθ3" around the rotation axis C, and rotates the tool spindle 30 by a predetermined angle "Δθ4" around the rotation axis C. The rotation direction of the workpiece spindle 22 is the same as the rotation direction of the tool spindle 30.

[0169] The rotation angle "Δθ3" of the work spindle 22 and the rotation angle "Δθ4" of the tool spindle 30 are synchronized based on the following equation (3).

[0170] Δθ3=Δθ4·Nc / Nw···(3) "Nc" shown in the above formula (3) represents the number of teeth of the pinion cutter TC. "Nw" represents the number of teeth formed on the surface of the workpiece W. "Nc" and "Nw" are fixed values, for example, as defined in the above setting parameter 124. Note that the above (3) can be applied to both the case of cutting teeth on the inner peripheral surface of the workpiece W and the case of cutting teeth on the outer peripheral surface of the workpiece W.

[0171] In step S230, the control unit 50 determines whether to end the tooth cutting process in the C-CE mode. As an example, based on the fact that the workpiece spindle 22 has rotated one full turn, the control unit 50 determines to end the tooth cutting process in the C-CE mode. If the control unit 50 determines to end the tooth cutting process in the C-CE mode (YES in step S230), the control unit 50 ends the process shown in FIG. 13. Otherwise (NO in step S230), the control returns to step S218.

[0172] <J. Modified Example> Next, referring to FIG. 15, a modified example of the machining mode in the above C-XY mode will be described. FIG. 15 is a view showing the machining mode in the C-XY mode according to the modified example from the Z-axis direction.

[0173] In the above C-XY mode, the machine tool hundred rotates the tool spindle 30 one full revolution while rotating the workpiece spindle 22 in the angle adjustment process. In contrast, in the C-XY mode according to this modified example, the machine tool 100 repeatedly performs an arc motion of the tool spindle 30 while rotating the workpiece spindle 22 in the angle adjustment process.

[0174] More specifically, the machine tool 100 changes the rotation angle of the tool spindle 30 centered on the rotation axis C by a predetermined angle from the rotation angle θS (first rotation angle). Then, based on the fact that the rotation angle has reached the rotation angle θE (second rotation angle), the machine tool 100 returns the rotation angle to the rotation angle θS. In this way, the machine tool 100 repeatedly performs an arc motion of the tool spindle 30 between the rotation angle θS and the rotation angle θE.

[0175] The rotation angles θS and θE may be arbitrarily set by the user, or may be defined at the time of design, etc. The rotation angles θS and θE are defined in the setting parameters 124, for example.

[0176] Although FIG. 15 shows an example of gear cutting on the inner peripheral surface of the workpiece W, the angle adjustment process of this modified example can also be applied to the case where gear cutting is performed on the outer peripheral surface of the workpiece W.

[0177] The machine tool 100 performs gear cutting while repeating the arc motion of the tool spindle 30 between the rotation angles θS and θE, thereby narrowing the driving range of the tool spindle 30. Therefore, even when the driving range of the tool spindle 30 is limited, gear cutting of the workpiece W can be performed. This type of processing is particularly advantageous when performing gear cutting on the outer peripheral surface of the workpiece W.

[0178] Hereinafter, the rotation angle between the rotation angle θS and the rotation angle θE is referred to as "Δθ5." In the process of forming a gear on the inner peripheral surface of the workpiece W, the rotation angle "Δθ5" is determined in advance based on the following formula (4).

[0179] Δθ5=(360 / Nw)·(1+Nc / Nw)··(4) "Nc" in the above formula (4) indicates the number of teeth of the pinion cutter TC. "Nw" in the above formula (4) indicates the number of teeth formed on the inner peripheral surface of the workpiece W. "Nc" and "Nw" are fixed values, and are defined, for example, in the setting parameter 124 described above.

[0180] In addition, in the process of forming a gear on the outer peripheral surface of the workpiece W, the rotation angle "Δθ5" is set in advance based on the following equation (5).

[0181] Δθ5=(360 / Nw)·(1-Nc / Nw)··(5) "Nc" in the above formula (5) indicates the number of teeth of the pinion cutter TC. "Nw" in the above formula (5) indicates the number of teeth formed on the outer peripheral surface of the workpiece W. "Nc" and "Nw" are fixed values, and are defined, for example, in the setting parameter 124 described above.

[0182] When returning the tool spindle 30 from the rotation angle θE to the rotation angle θS, the machine tool 100 may keep the rotation of the tool spindle 30 inhibited, or may rotate the tool spindle 30 by a predetermined angle. Preferably, when returning the tool spindle 30 from the rotation angle θE to the rotation angle θS, the machine tool 100 rotates the tool spindle 30 by a predetermined angle. This makes it possible to prevent wear of the pinion cutter TC from concentrating on one part.

[0183] More specifically, each time the angle adjustment process is performed, the machine tool 100 changes the rotation angle of the tool spindle 30 about the rotation axis C from the rotation angle θS by a predetermined angle. Then, when the rotation angle reaches the rotation angle θE, the machine tool 100 turns off the brake mechanism BCE (see FIG. 3) described above and unlocks the tool spindle 30 from the rotation axis CE. Next, the machine tool 100 returns the rotation angle of the tool spindle 30 to the rotation angle θS and rotates the tool spindle 30 about the rotation axis CE by a predetermined angle. Thereafter, the machine tool 100 turns on the brake mechanism BCE and locks the rotation axis CE of the tool spindle 30.

[0184] Hereinafter, the rotation angle of the tool spindle 30 when returning from the rotation angle θE to the rotation angle θS is defined as "Δθ6." In the processing for forming a gear on the inner peripheral surface of the workpiece W, the rotation angle "Δθ6" is determined in advance based on the following equation (6).

[0185] Δθ6=360 / Nc (6) In addition, when the tool spindle 30 is rotated by an angle "Δθ6" after one loop, the resolution of the encoder of the rotary axis CE is affected. Therefore, preferably, the machine tool 100 calculates the rotation angle "Δθ7" so as to be a multiple of the minimum resolution of the encoder. Then, the machine tool 100 reflects the difference between the calculated rotation angle "Δθ7" and the above rotation angle "Δθ6" in the circular motion of the tool spindle 30 or the rotation motion of the work spindle 22.

[0186] Also, depending on the brake mechanism BCE, the tool spindle 30 can only be clamped at predetermined angles (for example, 7.5°). In this case, the machine tool 100 calculates the rotation angle "Δθ8" so as to be a multiple of the predetermined angle. Then, the machine tool 100 reflects the difference between the calculated rotation angle "Δθ8" and the above rotation angle "Δθ6" in the circular motion of the tool spindle 30 or the rotation motion of the work spindle 22.

[0187] <K. Others> Note that the machining mode implemented in the machine tool 100 may be either the C-XY mode or the C-CE mode, or both the C-XY mode and the C-CE mode.

[0188] When both the C-XY mode and the C-CE mode machining modes are implemented in the machine tool 100, the machining mode can be arbitrarily switched by user operation.

[0189] In addition, the machine tool 100 may switch between the machining mode in the above C-XY mode and the machining mode in the above C-CE mode based on predetermined conditions.

[0190] As an example, the machine tool 100 switches the operation mode according to the diameter of the work W in the direction orthogonal to the rotation axis C of the work spindle 22. In this case, when the diameter of the work W is larger than a predetermined value, the machine tool 100 performs machining of the work W in the machining mode in the C-CE mode. On the other hand, when the diameter of the work W is smaller than a predetermined value, the machine tool 100 performs machining of the work W in the machining mode in the C-CX mode.

[0191] Furthermore, in the above description, the tool holding unit 20 is described as being the tool spindle 30, but the tool holding unit 20 is not limited to the tool spindle 30. As another example, the tool holding unit 20 may be a turret. The turret is configured to be rotatable about a rotation axis (hereinafter also referred to as the "rotation axis CE'") parallel to the rotation axis C. The turret holds multiple tools spaced apart in the circumferential direction around the rotation axis CE'. Typically, the turret performs turning by bringing a fixed tool held by the turret into contact with the workpiece W, which is rotated by the workpiece spindle 22.

[0192] The tools held by the turret include the pinion cutter TC. The turret can perform not only turning but also gear cutting using the pinion cutter TC.

[0193] More specifically, the turret is configured to be capable of being driven to feed in each of the X-, Z-axis directions by various drive mechanisms such as motors. The turret achieves the gear cutting process by being driven to feed in the direction of the rotation axis CE' with the pinion cutter TC facing the rotation axis CE'. Even a machine tool equipped with such a turret can achieve the above-mentioned C-XY mode machining and C-CE mode machining.

[0194] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0195] 5 magazine, 11 bed, 20 tool holding unit, 22 workpiece spindle, 23 first chuck mechanism, 27 opposing workpiece spindle, 28 second chuck mechanism, 30 tool spindle, 50 control unit, 100 machine tool, 101 control circuit, 102 ROM, 103 RAM, 104 communication interface, 109 internal bus, 120 auxiliary storage device, 122 control program, 124 setting parameters, 130 cover, 210 rotation drive unit, 211C motor driver, 212C motor, 220 feed drive unit, 221Z motor driver, 222Z motor, 230A feed drive unit, 230B rotation drive unit, 230C rotation drive unit, 231B motor driver, 231C motor driver, 231X motor driver, 231Y motor driver, 231Z motor driver, 232B Motor, 232C motor, 232X motor, 232Y motor, 232Z motor, 400 operation panel, 405 display, 406 operation key, AR1 tool storage area, AR2 machining area, BC brake mechanism, BCE brake mechanism, C rotary axis, CE rotary axis, D door, FF flank face, RF rake face, SF1 surface, SF2 surface, SP machining start position, T tool, TC pinion cutter, TC1 main body, TC2 tooth part, TE tooth tip, W workpiece, θE rotation angle, θS rotation angle.

Claims

1. a work spindle configured to be able to hold a workpiece; a tool holding portion configured to be able to hold a pinion cutter; a first rotation drive unit for driving the work spindle to rotate around a first axis along the axial direction of the work spindle; a feed drive unit for moving the tool holding unit; a second rotation drive unit for rotationally driving the tool holding unit around a second axis along the axial direction of the pinion cutter; a first brake mechanism for braking the rotation of the work spindle; a second brake mechanism for braking the rotation of the tool holding unit; a control unit for controlling the feed drive unit, the first and second rotation drive units, and the first and second brake mechanisms, The control unit a reciprocating drive process for performing gear cutting on an inner peripheral surface or an outer peripheral surface of the workpiece by reciprocatingly driving the tool holding unit in a direction of the first axis; an adjustment process for adjusting a rotation angle between the work spindle and the tool holder by rotating the work spindle by a predetermined angle around the first axis and rotating the tool holder by a predetermined angle around the second axis; the reciprocating drive process is performed in a state in which the first brake mechanism and the second brake mechanism are applied, The adjustment process is performed in a state where neither the first brake mechanism nor the second brake mechanism is applied.

2. The machine tool according to claim 1 , wherein the control unit monitors a temperature of a drive system related to the feed drive unit, and executes an abnormality handling process when the temperature exceeds a second threshold value.

3. The machine tool according to claim 2 , wherein the abnormality handling process includes at least one of a process of stopping gear cutting of the workpiece and a process of outputting a warning.

4. The machine tool according to claim 2 or 3, wherein the control unit executes a process of stopping the execution of the abnormality handling process when the temperature falls below a first threshold value.

5. the control unit further executes the reciprocating drive process and the adjustment process based on preset parameters; the parameters include a parameter for specifying whether or not braking by the first brake mechanism is enabled, The control unit When the parameter is set to enable braking by the first brake mechanism, the reciprocating drive process is executed while enabling the braking; The machine tool according to any one of claims 1 to 3, wherein, when the parameter is set to disable braking by the first brake mechanism, the reciprocating drive process is executed while maintaining the rotation angle of the work spindle at a target rotation angle corresponding to a command value with the brake disabled.

6. In the reciprocating drive process, the tool holding unit is driven to reciprocate between a first position in the direction of the first axis and a second position in the direction of the first axis, the first position is a position that is a first distance away from one side surface of the workpiece in the direction of the first axis, 4. The machine tool according to claim 1, wherein the second position is a position that is a second distance away from the other surface of the workpiece in the direction of the first axis.

7. The control unit further executes the reciprocating drive process based on preset parameters, The machine tool according to claim 6 , wherein the parameters include the first distance and the second distance.

8. The control unit further executes the adjustment process based on preset parameters, 4. The machine tool according to claim 1, wherein the parameters include a correction value relating to the center of rotation of the tool holder during the adjustment process.

9. The control unit further executes the reciprocating drive process based on preset parameters, The machine tool according to any one of claims 1 to 3, wherein the parameters include a parameter for specifying whether or not a feed drive direction of the tool holding unit when gear cutting the workpiece is to be inclined in a direction in which the workpiece is cut.

10. A method for controlling a machine tool, comprising: The machine tool comprises: a work spindle configured to be able to hold a workpiece; a tool holding portion configured to be able to hold a pinion cutter; a first rotation drive unit for driving the work spindle to rotate around a first axis along the axial direction of the work spindle; a feed drive unit for moving the tool holding unit; a second rotation drive unit for rotationally driving the tool holding unit around a second axis along the axial direction of the pinion cutter; a first brake mechanism for braking the rotation of the work spindle; a second brake mechanism for braking the rotation of the tool holding unit; a control unit for controlling the feed drive unit, the first and second rotation drive units, and the first and second brake mechanisms, The control method includes: a reciprocating driving step of reciprocating the tool holding unit in the direction of the first axis to perform gear cutting on the inner peripheral surface or the outer peripheral surface of the workpiece; an adjusting step of adjusting a rotation angle between the work spindle and the tool holder by rotating the work spindle by a predetermined angle about the first axis and rotating the tool holder by a predetermined angle about the second axis; the reciprocating driving step is performed in a state in which braking by the first brake mechanism and braking by the second brake mechanism are applied, A control method, wherein the adjusting step is performed in a state where neither the first brake mechanism nor the second brake mechanism is being applied.

11. A machine tool control program, The machine tool comprises: a work spindle configured to be able to hold a workpiece; a tool holding portion configured to be able to hold a pinion cutter; a first rotation drive unit for driving the work spindle to rotate around a first axis along the axial direction of the work spindle; a feed drive unit for moving the tool holding unit; a second rotation drive unit for rotationally driving the tool holding unit around a second axis along the axial direction of the pinion cutter; a first brake mechanism for braking the rotation of the work spindle; a second brake mechanism for braking the rotation of the tool holding unit; a control unit for controlling the feed drive unit, the first and second rotation drive units, and the first and second brake mechanisms, The control program causes the control unit to a reciprocating drive process for performing gear cutting on an inner peripheral surface or an outer peripheral surface of the workpiece by reciprocatingly driving the tool holding unit in a direction of the first axis; an adjustment process for adjusting a rotation angle between the work spindle and the tool holder by rotating the work spindle by a predetermined angle around the first axis and rotating the tool holder by a predetermined angle around the second axis; the reciprocating drive process is performed in a state in which the first brake mechanism and the second brake mechanism are applied, The adjustment process is executed in a state where neither the first brake mechanism nor the second brake mechanism is applied.

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