Control device and machine tool comprising it

Abstract

A control device (20) that controls operations of a shaft drive unit (15) and a feed drive unit (11) of a machine tool (1) comprising a shaft (2) for supporting and rotating a workpiece (W), a tool holder (4) for supporting a tool (T), the shaft drive unit (15) for rotating the shaft (2), and the feed drive unit (11) for relatively moving the tool holder (4) and the shaft (2) along a Z-axis coincident with an axis of the shaft (2), an X-axis orthogonal to the Z-axis, and a Y-axis orthogonal to the Z-axis and the X-axis, the control device (20) comprising: a control unit (23) for controlling the shaft drive unit (15) and the feed drive unit (11); and an eccentric removal control unit (27) for machining an eccentric body (Wb) provided at a position in the workpiece (W) carried by the shaft (2), the position being radially offset from a center of the shaft (2), where the eccentric removal control unit (27) is configured to rotate the shaft (2) together with the control unit (23) to position a position of the center of the eccentric body (Wb) so that it lies on the X-axis, then to calculate values ​​of the movement in an arc movement in which arc loci are formed using the following formulas (1) and (2) X = R cos θ Y = R sin θ satisfying values ​​for a position at which the position of the center of the eccentric body (Wb) has been positioned so as to lie on the X-axis, and to move the tool holder (4) and the shaft (2) relatively in the direction of the Z-axis, while the tool holder (4) and the shaft (2) are relatively moved in synchronization with the rotation of the shaft (2) so that the calculated values ​​of the movement are achieved in the arc movement, with an eccentricity denoted by R, which is a distance between a center of the shaft (2) and a center of the eccentric body (Wb), and an angle of rotation denoted by θ of the center of the eccentric body (Wb) around the axis of the shaft (2) with the X-axis as a reference; and in a case where the eccentric body (Wb) is a spiral along the direction of the Z-axis, the eccentric removal control unit (27) is configured, together with the control unit (23), to relatively move the tool holder (4) and the shaft (2), with a length of the eccentric body (Wb) denoted by LengZ in the Z-axis direction and a phase increase / decrease value of the eccentricity denoted by Q in the Z-axis direction, and further in synchronization with a feed distance ΔZ in the Z-axis direction per unit time, with a phase change value Δϕ per unit time satisfying the following formula (3): Δ ϕ = Q × Δ Z LengZ

Description

Area

[0001] The present disclosure relates to a control device for a machine tool configured to perform turning machining of a workpiece, and more particularly to a control device for machining an eccentric body of a workpiece having the eccentric body at a position radially offset from the center of a shaft, and a machine tool including the control device. background

[0002] As a method for machining a workpiece including a base portion having a cylindrical shape and an eccentric body projecting outward from an end surface of the base portion along a central axis of the base portion and provided at a position radially offset from the central axis, which is a machining method for machining the eccentric body, for example, a method described in Patent Literature 1 is conventionally known.

[0003] In the machining method described in Patent Literature 1, an eccentric chuck having a clamping portion for clamping a workpiece is mounted on a shaft of a lathe at a position radially offset (displaced) from an axis of the shaft, and the workpiece is clamped by the eccentric chuck such that an axis of the eccentric body is coaxial with the axis of the shaft. In this state, the shaft is then rotated, and an outer peripheral portion of the eccentric body is machined as desired using a tool.

[0004] Patent Literature 2 discloses a method for turning an eccentric shaft of a crankshaft. In the machining method described in Patent Literature 2, the crankshaft is rotated in a state where one end of the crankshaft is clamped by a shaft and the other end is held by a tailstock spindle. A tool is fed in the up-down direction (the Y-axis direction) and the front-back direction (the Z-axis direction) by a distance of 2r in synchronization with a rotation cycle of the crankshaft, where r is a radius of the eccentric shaft. This combined feed of the feed in the Y-axis direction and the feed in the Z-axis direction causes the tool to perform a circular motion with a radius r, thereby turning an outer periphery of the eccentric shaft.

[0005] A similar machining method is also proposed in Patent Literature 3. The machining method described in Patent Literature 3 is a method in which two eccentric shafts are machined, that is, a first eccentric shaft protruding outward from an end surface of a base part along a central axis of the base part, and a second eccentric shaft protruding further outward from the first eccentric shaft.

[0006] JP 2003 - 266 202 A discloses a control device for performing a turning operation on a crankshaft, wherein eccentric connections in the crankshaft are turned by the turning tool moving along with the eccentric connection.

[0007] CN 1 570 396 A discloses a control device for performing a turning operation on components of a screw pump, wherein a drum with cutting tools is rotated around the component. Citation listPatent literature Patent literature 1: JP 2003 - 236 701 A Patent literature 2: JP S54 - 94 185 A Patent literature 3: JP 2017 - 209 779 A Overview of the inventionTechnical problem

[0008] None of the methods disclosed in Patent Literatures 1 to 3 described above consider the position of the eccentric body when the workpiece is held by the shaft, where the position is an angular position (phase) of the eccentric body in the circumferential direction around the axis of the shaft. Accordingly, in this method, it seems necessary to start machining the workpiece in a state where the workpieces are each held by the shaft so that the phases of the eccentric bodies are adjusted to a predetermined reference phase.

[0009] However, there is a case where, when the workpieces are each held by the shaft, the phases of the eccentric bodies vary from workpiece to workpiece due to a relationship with other machined parts that are different from the eccentric bodies. In this case, when the workpieces are each held by the shaft, the phases of the eccentric bodies cannot be set to be the reference phase. Accordingly, in the case of such workpieces, it is convenient to be able to start machining the eccentric bodies with different phases.

[0010] For example, the above-described crankshaft and eccentric journal machined products are exemplified. In addition, various shapes of machined products with eccentric bodies are available, such as eccentric screws used in force converters, which achieve large clamping forces with low tightening torque due to wedge action, and progressive cavity pumps, which are a type of rotary displacement pump that can move various fluids without quantization and pulsation, and can efficiently move fluids from water-like to highly viscous, solids, and powders.Accordingly, it is advantageous in terms of equipment costs if such eccentric bodies with various shapes can be manufactured by using a general-purpose machine tool and a general-purpose clamping device instead of a dedicated machine tool and a dedicated clamping device.

[0011] Since the circular motion in each of the machining methods described above is realized by operating a feed piston at a high speed in synchronization with the rotational speed of the shaft, the load on a feed motor, in particular, increases, which is a problem. Accordingly, if the rotational speed of the shaft motor is controlled so that the load acting on the feed motor does not exceed a permissible load, damage to the feed motor can be prevented.

[0012] The present disclosure has been made in view of the above circumstances. It is an object thereof to provide a control device capable of starting turning machining in a state where an eccentric body is disposed at any phase, and a machine tool having the control device. Another object thereof is to provide a control device capable of machining eccentric bodies having various shapes, and a machine tool having the control device. Still another object thereof is to provide a control device capable of preventing a load acting on a feed motor from exceeding an allowable load when machining an eccentric body, and a machine tool having the control device. Solution to the problem

[0013] To solve the problems described above, a control device is proposed which has the features defined in claim 1 or claim 2. Advantageous embodiments of the control device have the features defined in claims 3 to 6. Furthermore, to solve the problems described above, a machine tool is proposed which has the features defined in claim 7.A control device according to the present disclosure controls operations of a shaft drive unit and a feed drive unit of a machine tool including a shaft for supporting and rotating a workpiece, a tool holder for supporting a tool, the shaft drive unit for rotating the shaft, and the feed drive unit for relatively moving the tool holder and the shaft along a Z-axis coincident with an axis of the shaft, an X-axis orthogonal to the Z-axis, and a Y-axis orthogonal to both the Z-axis and the X-axis. The control device includes: a control unit for controlling the shaft drive unit and the feed drive unit; and an eccentric machining control unit for machining an eccentric body provided at a position in the workpiece supported by the shaft, the position being radially offset from a center of the shaft.The eccentric cutting control unit is configured to rotate the shaft together with the control unit to position a position of the center of the eccentric body so as to be on the X-axis and then relatively move the tool in the Z-axis direction while relatively moving the tool in synchronization with the rotation of the shaft, with an eccentricity denoted by R which is a distance between a center of the shaft and a center of the eccentric body, and an angle of rotation denoted by θ of the center of the eccentric body around the axis of the shaft with the X-axis as a reference, so that an arc motion is generated in which a position X in the X-axis direction and a position Y in the Y-axis direction respectively draw arc loci with values ​​satisfying the following formulas (1) and (2). X=Rcosθ Y=Rsinθ

[0014] According to this control device, the eccentric cutting control unit rotates the shaft together with the control unit to position the center of the eccentric body so that it is located on the X-axis, and the eccentric cutting control unit moves the tool to a turning machining start position in a three-dimensional space formed by the X-axis, the Y-axis, and the Z-axis. Meanwhile, a cutting edge of the tool is in a state where it is not in contact with the workpiece and is in a state where it can come into contact with an outer peripheral surface of the eccentric body at a predetermined cutting depth by moving it in the Z-axis direction as described later.

[0015] Thereafter, the tool is relatively moved in the Z-axis direction while being relatively moved in synchronization with the rotation (phase θ) of the shaft, with an eccentricity denoted by R, which is a distance between a center of the shaft and a center of the eccentric body, and an angle denoted by θ of rotation of the center of the eccentric body around the axis of the shaft with the X-axis as a reference, so that an arc motion is generated in which a position X in the X-axis direction and a position Y in the Y-axis direction draw arc loci with a radius R.

[0016] By moving the tool relatively in synchronization with the rotation (phase θ) of the shaft so that the X position = Rcosθ and the Y position = Rsinθ are satisfied, it is possible to cause the tool to come into contact with the outer peripheral surface of the eccentric body rotating around the shaft axis and also to follow the rotation of the eccentric body. By moving the tool in the Z-axis direction in this state, the outer periphery of the eccentric body can then be machined.

[0017] As described above, according to the control device of the present disclosure, machining can be started after the position of the center of each eccentric body is positioned so that it is located on the X-axis, even if the phases of the eccentric bodies vary from workpiece to workpiece when the workpieces are respectively held by the shaft. Accordingly, unlike the conventional machining methods, there is no need to hold the workpiece by the shaft so that the phase of the eccentric body is set as the predetermined reference phase, and various workpieces can be machined without performing laborious adjustment work when each of the workpieces is held by the shaft.As a result of the above, a machining program in which a machining reference position is set on the X-axis can also be used as an NC (numerical control) machining program for performing machining.

[0018] Additionally, general-purpose products can be used with the machine tool and a fixture that holds the workpiece.

[0019] In the aspect of the present disclosure, the control unit is configured to be able to execute three control modes, including a speed control mode in which the shaft is rotated at a predetermined rotational speed, a position control mode in which the shaft is positioned at a predetermined rotational angular position around the axis of the shaft, and a synchronous control mode in which an operation of the shaft drive unit and an operation of the feed drive unit are synchronized with each other, and the eccentric cutting control unit is configured to synchronize the operation of the shaft drive unit and the operation of the feed drive unit by causing the control unit to enter the synchronous control mode.

[0020] In the aspect of the present disclosure, the eccentric body is a spiral along the Z-axis direction, and the eccentric cutting control unit is configured, together with the control unit, to relatively rotate the tool with a length of the eccentric body denoted by LengZ in the Z-axis direction and a phase increase / decrease value of the eccentricity denoted by Q in the Z-axis direction, and further in synchronization with a feed distance ΔZ in the Z-axis direction per unit time, with a phase change value Δϕ per unit time that satisfies the following formula (3). Formula 1: Δϕ=Q×ΔZLengZ

[0021] According to the control device of this aspect, the outer peripheral surface of the eccentric body can be machined in a case where the longitudinal direction of the eccentric body is in the Z-axis direction. Note that a screw or the like can be given as an example of a body axis.

[0022] Alternatively, in the aspect of the present disclosure, the eccentric body is a spiral along the Z-axis direction, and the eccentric cutting control device is configured, together with the control unit, to relatively move the tool with a length of the eccentric body denoted by LengZ in the Z-axis direction and an eccentricity increase / decrease value denoted by K in the Z-axis direction, and further in synchronization with a feed distance ΔZ in the Z-axis direction per unit time, with the eccentricity R satisfying the following formula (4). Formula 2: R=R+K×ΔZLengZ

[0023] In the case where the longitudinal direction of the eccentric body is in the Z-axis direction, the outer peripheral surface of the eccentric body itself can be machined with the control device of this aspect.

[0024] Additionally, in the aspect of the present disclosure, the control device is configured to perform, via at least the control unit, turning processing without synchronization between the operation of the shaft drive unit and the operation of the feed drive unit.

[0025] In the aspect of the present disclosure, the eccentric cutting control unit is configured to perform feed forward control on the feed drive unit together with the control unit.

[0026] In the aspect of the present disclosure, the eccentric cutting control unit is configured to control, together with the control unit, a combined speed of a feed speed of the feed drive unit and an angular speed in the arc movement to be less than or equal to a predetermined speed limit, and the combined speed is set such that a load of the feed drive unit does not exceed an allowable load.

[0027] According to the control device of this aspect, since the load on the feed drive unit is controlled so as not to exceed the allowable load, damage to the feed drive unit is prevented.

[0028] Furthermore, in the aspect of the present disclosure, the eccentric cutting control unit is configured to control, together with the control unit, an acceleration of a uniform circular motion in the arc motion to be less than or equal to a predetermined acceleration limit, and the acceleration limit is set such that a load of the feed drive unit does not exceed an allowable load.

[0029] Since the feed drive unit according to the control device of this aspect is controlled so that the acceleration is a uniform circular motion in the arc motion less than or equal to the predetermined acceleration limit, in such a way that the acting load does not exceed the allowable load, the feed drive unit can be operated in a stable state and damage to the feed drive unit can be prevented.

[0030] Furthermore, the present disclosure relates to a machine tool comprising: a shaft for supporting and rotating a workpiece, a tool holder for supporting a workpiece, a shaft drive unit for rotating the shaft, and a feed drive unit for relatively moving the tool holder and the shaft along a Z-axis coincident with an axis of the shaft, an X-axis orthogonal to the Z-axis, and a Y-axis orthogonal to the Z-axis and the X-axis; and the control device according to any one of the above-described control devices. Advantageous effects of the invention

[0031] As described above, according to the control device and the machine tool incorporating the same of the present disclosure, even if the phases of the eccentric bodies vary from workpiece to workpiece when the workpieces are respectively held by the shaft, machining can be started after the position of the center of each eccentric body is positioned to be on the X-axis, and accordingly, unlike the conventional ones, there is no need to perform cumbersome adjustment work when each of the workpieces is held by the shaft, and various workpieces can be efficiently machined.

[0032] In addition, since general-purpose products can be used with the machine tool and the fixture supporting the workpiece, fixture costs can be reduced and productivity can be improved because a dedicated setup (adjustment work) is unnecessary.

[0033] Furthermore, it is possible to machine eccentric bodies with different shapes and forms, such as a spiral axis. Short description of the drawings Fig. 1 is an explanatory view for explaining an example of a method for machining an eccentric body using a machine tool according to an embodiment of the present disclosure. Fig. 2 is a block diagram showing an example of a schematic configuration of the machine tool according to the present disclosure. Fig. 3 is an explanatory diagram showing an example of an overview of eccentric cutting according to the present embodiment. Fig. 4 is an explanatory diagram showing an example of an NC program according to the present embodiment. Fig. 5 is a flowchart showing examples of processes performed by an eccentric cutting control unit and a control unit of the present embodiment. Fig. 6 is a perspective view showing an example of machining another workpiece according to the present embodiment. Fig. 7 is an explanatory view showing an example of an overview of eccentric cutting according to a first modification of the present embodiment. Fig. 8 is an explanatory diagram showing an example of an NC program according to the first modification. Fig. 9 is a flowchart showing examples of processes performed by the eccentric cutting control unit and the control unit of the first modification. Fig. 10 is an explanatory view showing an example of an outline of eccentric cutting according to a second modification of the present embodiment. Fig. 11 is an explanatory diagram showing an example of an NC program according to the second modification. Description of embodiments

[0034] Hereinafter, a specific embodiment of the present disclosure will be described with reference to the drawings. Fig. 1 is an explanatory view for explaining an example of a method for machining an eccentric body using a machine tool according to an embodiment of the present disclosure. Fig. Fig. 2 is a block diagram showing an example of a schematic configuration of the machine tool according to the present embodiment. It should be noted that, as shown in Fig. 1, a workpiece W of the present example, which is an object to be machined, comprises a base part Wa having a cylindrical shape and an eccentric body Wb having a cylindrical shape with a radius r and projecting forward from a front end surface of the base part Wa at a position radially offset by a distance R from an axis of the base part Wa.

[0035] As in the Fig. 1 and Fig. 2, a machine tool 1 of the present example includes a shaft 2, a clamping device 3 in which the base part Wa of the workpiece W is clamped when the workpiece W is attached to the shaft 2, a tool holder 4 supporting a tool T, a drive unit 10, a control device 20 controlling the drive unit 10, and an input / output device 30.

[0036] Note that the machine tool 1 of the present example is a horizontal NC general-purpose lathe, but a machine tool to which the present disclosure is applicable is not limited thereto. In addition to a vertical NC lathe, various machine tools may be applied, such as a combination machine tool configured to perform turning and drilling.

[0037] The drive unit 10 includes a shaft drive unit 15 that drives and controls a shaft motor that rotates the shaft 2, and a feed drive unit 11 that drives and controls a motor of a feed device that moves the tool holder 4. The feed drive unit 11 includes an X-axis feed drive unit 12 that drives and controls a motor of an X-axis feed device that moves the tool holder 4 in the X-axis direction, a Y-axis feed drive unit 13 that drives and controls a motor of a Y-axis feed device that moves the tool holder 4 in the Y-axis direction, and a Z-axis feed drive unit 14 that drives and controls a motor of a Z-axis feed device that moves the tool holder 4 in the Z-axis direction.In this example, the Z axis is defined as coaxial with the axis of shaft 2, the X axis is horizontally orthogonal to the Z axis, and the Y axis is orthogonal to both the X axis and the Z axis.

[0038] Accordingly, the tool holder 4 is moved in the X-axis, Y-axis, and Z-axis directions by the operations of the X-axis feed mechanism, the Y-axis feed mechanism, and the Z-axis feed mechanism, which are driven and controlled by the feed drive unit 11. Consequently, the tool T is moved in a three-dimensional space defined by the X-axis, Y-axis, and Z-axis. In addition, the shaft 2 is driven by the shaft motor, which is driven and controlled by the shaft drive unit 15, and rotates around its axis.

[0039] The input / output device 30 includes, for example, a display with an input function, such as a touch panel, and an input / output interface for inputting / outputting data, etc. Of course, the input function displays an image, property information, and the like on the display, and input can be made via the input function.

[0040] The control device 20 comprises an NC program storage unit 21, a program analysis unit 22, a control unit 23, a parameter storage unit 26 and an eccentric removal control unit 27.

[0041] Note that the control device 20 is a numerical control device and includes a computer including a central processing unit (CPU), a random access memory (RAM), and a read-only memory (ROM). The program analysis unit 22, the control unit 23, and the eccentric cutting control unit 27 realize their functions through a computer program and execute processes described later. In addition, the NC program storage unit 21 and the parameter storage unit 26 each suitably include a storage medium such as a RAM.

[0042] The NC program storage unit 21 is a functional unit that stores an NC program (machining program) for an NC controller, and stores, for example, an NC program input from the input / output device 30. The parameter storage unit 26 is a functional unit that stores setting values ​​for an eccentric restriction speed, an eccentric restriction acceleration, and an eccentric feedforward gain, which are parameters in eccentric cutting and the like, and stores, for example, corresponding parameters input from the input / output device 30.

[0043] The program analysis unit 22 sequentially reads each of the NC program blocks included in an NC program to be executed, stored in the NC program storage unit 21, and processes NC codes included in the blocks. When processing an NC code related to feed control, the program analysis unit 22 sends a command in accordance with the NC code to the control unit 23. When processing an NC code related to rotation control, the program analysis unit 22 sends a command in accordance with the NC code to the control unit 23.

[0044] In addition, the program analysis unit 22 distinguishes an eccentric removal command from other commands. In the case of an eccentric removal command, the program analysis unit 22 sends a command required for eccentric removal to the eccentric removal control unit 27 and the control unit 23. In the case of commands that are different from the eccentric removal command, the program analysis unit 22 sends corresponding commands to the control unit 23.

[0045] The control unit 23 includes a feed control unit 24 and a shaft control unit 25. The feed control unit 24 is a functional unit that controls the operations of the X-axis feed mechanism, the Y-axis feed mechanism, and the Z-axis feed mechanism via the X-axis feed drive unit 12, the Y-axis feed drive unit 13, and the Z-axis feed drive unit 14, respectively. The feed control unit 24 receives a feed control command from the program analysis unit 22 and controls the X-axis feed drive unit 12, the Y-axis feed drive unit 13, and the Z-axis feed drive unit 14 so that the X-axis feed mechanism, the Y-axis feed mechanism, and the Z-axis feed mechanism operate at a speed consistent with the received command.

[0046] The shaft control unit 25 is a functional unit that controls the rotation operation of the shaft motor via the shaft drive unit 15. The shaft control unit 25 receives a rotation control command from the program analysis unit 22 and controls the shaft drive unit 15 so that the shaft motor rotates in a rotation direction and at a rotation speed consistent with the received command.

[0047] In accordance with the command from the program analysis unit 22, the control unit 23 can cause the shaft control unit 25 to operate in two processing modes, namely a speed control mode and a position control mode, and can cause the shaft control unit 25 and the feed control unit 24 to operate in a synchronous control mode. The speed control mode is a mode in which the shaft motor is rotated at a predetermined rotational speed. The position control mode is a mode in which the shaft motor is positioned at a predetermined rotational angular position about its axis. The synchronous control mode is a mode in which the operation of the shaft motor is synchronized with the operations of the X-axis feeder, the Y-axis feeder, and the Z-axis feeder.

[0048] In the speed control mode, in accordance with a shaft rotation speed command sent from the program analysis unit 22, the shaft control unit 25 outputs angular position data for rotating the shaft motor at the rotation speed to the shaft drive unit 15. In the position control mode, in accordance with an angular position command sent from the program analysis unit 22, the shaft control unit 25 outputs angular position data for positioning the shaft motor at a commanded angular position about its axis to the shaft drive unit 15. In the synchronous control mode, in accordance with a synchronous command sent from the program analysis unit 22 or the eccentric cutting control unit 27, the shaft control unit 25 synchronizes the operation of the shaft motor with the operations of the X-axis feeder, the Y-axis feeder, and the Z-axis feeder.

[0049] The eccentric cutting control unit 27 receives the eccentric cutting command from the program analysis unit 22, sends a command concerning the eccentric cutting to the control unit 23, and causes the drive unit 10 to execute the eccentric cutting together with the control unit 23.

[0050] Fig. 3 is an explanatory diagram showing an example of an overview of eccentric cutting according to the present embodiment. Fig. 4 is an explanatory diagram showing an example of an NC program according to the present embodiment. As shown in Fig. 3 shown (see also Fig. 1), the axis of the eccentric body Wb is eccentric from the axis of the workpiece W (ie, the axis of the shaft 2) by a distance R (hereinafter referred to as eccentricity R) in the X-axis direction. A clockwise angular position (phase) of the eccentric body Wb around the axis of the shaft when the axis on a positive side of the X-axis is used as the reference axis is denoted by C. The angular position C indicates an angular position of the eccentric body Wb when the workpiece W is attached to the shaft 2, that is, at a directional position of the shaft 2 for determining a machining position of the eccentric body Wb. When the shaft 2 rotates during the machining process, the position of the eccentric body Wb around the axis of the shaft also rotates.The angle of rotation of the eccentric body Wb around the shaft axis, when the axis on the positive side of the X-axis is used as a reference axis, is denoted by θ for any time point with respect to a shaft rotation command. Note that the following primarily describes NC codes unique to eccentric machining.

[0051] In Fig. 4, a code “M45” is a command to switch to the position control mode, wherein the command is sent from the program analysis unit 22 to the control unit 23 in accordance with M45, and upon receipt of this command, the shaft control unit 25 switches to the position control mode.

[0052] A code "G128" is a code for eccentric cutting control, "P" defines its validity and invalidity, "P1" means that the eccentric cutting control is valid, and "P0" means that the eccentric cutting control is invalid. In addition, "R" is the eccentricity and "C" is a phase (eccentric phase) of the eccentric body Wb. When these codes are recognized by the program analysis unit 22, a command concerning the start of eccentric cutting and information concerning the eccentric cutting are sent to the eccentric cutting control unit 27, and the processing described later Fig. The processes shown in Figure 5 are carried out in cooperation with the control unit 23.

[0053] A "G50" code is a command to limit (i.e., restrict) the maximum rotational speed of the shaft motor, and a "G96" code is a code to control a peripheral speed so that it remains constant. Furthermore, "S" is a speed command.

[0054] Next, the eccentric cutting control executed by cooperation between the eccentric cutting control unit 27 and the control unit 23 will be explained in detail with reference to the Fig. 5 described. Fig. 5 is a flowchart showing examples of processes performed by the eccentric cutting control unit and the control unit of the present embodiment.

[0055] Based on the eccentricity R received from the program analysis unit 22, the control unit 23 first calculates an eccentricity offset obtained by adding the eccentricity R (= 10 mm) to an offset of the X-axis and then performs control of the machine coordinates based on the eccentricity offset (step S1).

[0056] Next, the eccentric machining control unit 27 sends a command regarding the eccentric phase C (= 90°) received from the program analysis unit 22 to the control unit 23 and rotates the shaft motor by the eccentric phase C (90°) in the opposite direction by controlling the shaft control unit 25 and the shaft drive unit 15 to position the position of the center of the eccentric body Wb to be on the X-axis (step S2). That is, a position around the axis of a C-axis, in this case, the shaft 2, is positioned at a position of the eccentric phase C. Thus, the machining position of the eccentric body Wb is determined.Note that the control unit 23 has meanwhile received the position control mode command according to the code "M45" from the program analysis unit 22 and has already caused the process mode of the shaft control unit 25 to switch to the position control mode. In the above example, the shaft motor is rotated in the opposite direction by the angle of the eccentric phase C (90°), but can be rotated by the angle C (90°) of the eccentric phase ± 360°×n (where n is 0 or a natural number). In short, it is only assumed that the shaft motor is rotated so that the center of the eccentric body Wb is on the X-axis. However, the smaller n is, the shorter the processing time can be.

[0057] Next, the eccentric cutting control unit 27 sends a synchronous control mode command to the control unit 23 to cause the shaft control unit 25 and the feed control unit 24 to switch to the synchronous control mode (step S3). Thus, an eccentric cutting control state is obtained by executing the above sequence.

[0058] Next, the eccentric cutting control unit 27 calculates the shaft rotation speed based on the speed command S, the shaft override, and the like sent from the program analysis unit 22, and refers to the parameter storage unit 26 to restrict (limit) the shaft rotation speed so that it does not exceed a rotation speed calculated from the eccentric restriction acceleration or the rotation speed in the G50 command (step S4).

[0059] In eccentric cutting control, the tool T is caused to perform an eccentric arc motion of eccentricity R in synchronization with the shaft rotation speed S in an XY-axis plane. Where an angular velocity of the shaft 2 is denoted by ω and time is denoted by t, the command positions X and Y on the X-axis and Y-axis in the eccentric arc motion are expressed by the following formulas (5) and (6), respectively. Note that ωt corresponds to a rotation angle θ of the shaft 2. X=Rcos(ωt) Y=Rsin(ωt)

[0060] If in formulas (5) and (6) the maximum acceleration of a uniform circular motion is denoted by A, the maximum acceleration A is expressed by the following formula (7). A=Rω2=R(2πS)2

[0061] By setting the maximum acceleration A as the eccentric limiting acceleration, a limited shaft rotation speed S clamp can be set by the following formula (8). Sclamp≤(1 / (2π))×(A / R)1 / 2

[0062] Next, the eccentric cutting control unit 27 calculates the values ​​of the eccentric arc movement in the XY-axis plane based on the shaft rotation speed determined by the limited shaft rotation speed S set in step S4. clampis limited (step S5). When a shaft rotation angle per unit control time T is denoted by Δθ, the values ​​of the eccentric arc motion ΔX and ΔY in the X-axis and Y-axis are calculated by the following formulas (9) and (10). Note that the eccentric limitation acceleration is preferably set so that loads in the X-axis feed mechanism and the Y-axis feed mechanism do not exceed an allowable load. Consequently, damage to the X-axis feed mechanism and the Y-axis feed mechanism can be prevented. ΔX=Rcos(Δθ) ΔY=Rsin(Δθ)

[0063] The eccentric cutting control unit 27 calculates the values ​​of the eccentric arc movement ΔX and ΔY at intervals of the control time unit T as described above, and sends the calculated values ​​of the eccentric arc movement ΔX and ΔY sequentially to the control unit 23.

[0064] Through cooperation between the feed control unit 24 and the shaft control unit 25, the control unit 23 rotates the shaft motor at the limited shaft rotation speed S clamp or less, and drives the X-axis feed mechanism and the Y-axis feed mechanism via the X-axis feed drive unit 12 and the Y-axis feed drive unit 13 in synchronization with the rotation angle position so that the tool T moves by the eccentric arc movement values ​​ΔX and ΔY sent from the eccentric cutting control unit 27. Note that the feed control unit 24 adds the eccentric arc movement values ​​ΔX and ΔY to the movement values ​​in the X-axis and Y-axis directions sent from the program analysis unit 22, thereby correcting the movement values.

[0065] In addition, in a case of controlling an arc motion using the X-axis feed mechanism and the Y-axis feed mechanism, a phenomenon occurs in which inward turning machining occurs due to a response delay caused by a position loop gain, and an eccentricity of an actual machining position becomes smaller than the designated eccentricity R. Accordingly, the eccentric cutting control unit 27 applies the eccentric feedforward gain stored in the parameter storage unit 26 to the values ​​of the eccentric arc motion ΔX and ΔY to prevent the inward turning machining. That is, the eccentric cutting control unit 27, in cooperation with the control unit 23, performs feedforward control of the feed drive unit 11.

[0066] The control unit 23 determines whether a normal turning machining command is received from the program analysis unit 22 (step S6). If the control unit 23 has received the normal turning machining command from the program analysis unit 22 (in a case, YES in step S6), the control unit 23 calculates the movement values ​​for each feed device based on this command (step S7). The turning machining command includes not only a fast feed command or a cutting command, but also a turning machining command such as thread cutting.

[0067] Here, the control unit 23 performs a restriction so that the movement value in the normal turning command does not exceed the eccentric restriction speed stored in the parameter storage unit 26. This is because the values ​​of the eccentric arc movement ΔX and ΔY are always corrected separately by the command values ​​of the NC program, so that a speed combined with the normal turning command exceeds a restriction speed of a rapid feedrate or a cutting feedrate. Accordingly, the restriction is performed with the movement value obtained from a speed obtained by subtracting the eccentric restriction speed from the restriction speed of the rapid feedrate or the cutting feedrate (step S8).That is, the eccentric removal control unit 27 is configured, in cooperation with the control unit 23, to control a combined speed of the feed rate of the feed drive unit 11 and the angular velocity in the arc movement so that it is less than or equal to a predetermined speed limit. It should be noted that the combined speed is preferably dimensioned such that a load in the feed drive unit 11 does not exceed the permissible load.

[0068] Next, the control unit 23 adds the eccentricity R, the value of the movement in a normal command obtained taking into account the eccentric restriction speed, and the values ​​of the eccentric arc movement ΔX and ΔY to a program command position, and outputs a result of the addition as a position command to the drive unit 10, thereby realizing the machining of the eccentric body Wb (step S9).

[0069] Assuming that the workpiece W is rotated clockwise at a rotational speed S, as in Fig. 3, the tool T performs an eccentric arc motion in the clockwise direction in synchronization with the rotation, thereby realizing a state in which the tool T is in contact with an outer peripheral surface of the eccentric body Wb.

[0070] Accordingly, after the tool T is positioned at a position where the cutting edge of the tool T is separated from the end surface of the eccentric body Wb by a predetermined distance in the positive direction of the Z-axis and is in a state of cutting an outer circumference of the eccentric body Wb with a predetermined cutting depth in the direction of the X-axis, the tool T is moved in the direction of the Z-axis while performing an arc movement with the radius R in synchronization with the rotation of the workpiece W, and thereby the outer peripheral surface of the eccentric body Wb is turned by the tool T.

[0071] Note that the acceleration / deceleration process is performed by the control unit 23 only for the movement value in the normal command. This is because the eccentric arc movement values ​​ΔX and ΔY are synchronized with the acceleration / deceleration of the shaft rotation speed, and the acceleration / deceleration process is unnecessary in terms of preventing inward turning.

[0072] Next, the eccentric cutting control unit 27 and the control unit 23 determine whether an eccentric cutting end command has been received from the program analysis unit 22 (step S10). If the eccentric cutting control unit 27 and the control unit 23 have received the eccentric cutting end command from the program analysis unit 22 (in a case, YES in step S10), the eccentric cutting control unit 27 stops calculating the eccentric arc movement values ​​ΔX and ΔY (step S11), and the control unit 23 cancels the synchronous control mode (step S12) and then ends the process. If the synchronous control mode is canceled in step S12, the control device 20, via at least the control unit 23, performs turning processing without synchronization between the operation of the shaft drive unit 15 and the operation of the feed drive unit 11.

[0073] On the other hand, when the eccentric cutting control unit 27 and the control unit 23 have not received the eccentric cutting end command from the program analysis unit 22 in step S10 (in a case, NO in step S10), the eccentric cutting control unit 27 and the control unit 23 repeatedly execute the processes of steps S4 to S9.

[0074] Additionally, if it is determined in step S6 that the normal turning machining command has not been received (in a case, NO in step S6), the eccentric cutting control unit 27 and the control unit 23 determine whether an eccentric cutting control command has been received from the program analysis unit 22 (step S13). If the eccentric cutting control command has been received (in a case, YES in step S13), the control unit 23 first changes the eccentric offset based on the eccentricity R newly received from the program analysis unit 22 (step S14), calculates a phase difference between the previous eccentric phase and the current eccentric phase (step S15), and then executes the processes from step S4 onward.Then, in step S4, the acceleration / deceleration process of the shaft motor is performed so that the phase difference becomes zero. This allows a plurality of eccentric bodies Wb to be generated at any position with a single eccentric removal control, and machining of a crankshaft journal and the like can be performed more efficiently. In addition, if it is determined in step S13 that the command concerning the eccentric removal control has not been received (in one case, NO in step S13), the processes from step S4 onward are also executed.

[0075] According to the machine tool 1 of the present example as described above, even in a case where the eccentric phases C of the eccentric bodies Wb vary from workpiece W to workpiece W when the workpieces W are respectively held by the jig 3 (shaft 2), machining can be started after the position of the center of each eccentric body Wb is positioned to be on the X-axis, and accordingly, unlike the conventional machining methods, it is not necessary to hold each workpiece W by the jig 3 (shaft 2) so that the eccentric phase C of the eccentric body Wb is adjusted to a predetermined reference phase, and thus, various workpieces W can be machined without performing troublesome adjustment work when each of the workpieces W is supported by the jig 3 (shaft 2).

[0076] For the drive unit 10 and the clamping device 3 of the machine tool 1, it is additionally possible to use those with conventionally used general-purpose structures.

[0077] It should be noted that in this embodiment, a workpiece W1 can be machined as shown in Fig. 6 is shown. Fig. Fig. 6 is a perspective view showing an example of machining another workpiece according to the present embodiment. In the workpiece W1 of this aspect, the eccentricity R in the Z-axis direction of an eccentric body Wb1 projecting from a base part Wa1 in the Z-axis direction is constant, but its radius r changes in the extending direction. In the workpiece shown in Fig. In the aspect shown in Figure 6, the radius r increases in the extension direction. The radius r is a distance between an X-axis coordinate command specified by a program and the position of the center of the eccentric body Wb1. Accordingly, by specifying the positions in the X-axis and Z-axis with the normal turning machining command, any shape can be formed in which the radius r changes in the extension direction with the eccentricity R as a reference. First variation

[0078] Next, a first modification of the above embodiment will be described. Fig. Fig. 7 is an explanatory view showing an example of an outline of eccentric cutting according to the first modification of the present embodiment. In the first modification, a workpiece W2 is machined as shown in Fig. 7. The workpiece W2 includes a base part Wa2 having a cylindrical shape and an eccentric body Wb2 protruding from a front end surface of the base part Wa2 in the Z-axis direction and formed at a position radially offset by the eccentricity R from an axis of the base part Wa2, and the eccentric body Wb2 has a shape whose axis is inclined (shifted) toward the axis of the base part Wa2.

[0079] Fig. 8 is an explanatory diagram showing an example of an NC program according to the first modification. Fig. Figure 8 shows an example of the NC program for machining the eccentric body Wb2 of the workpiece W2. As shown in Fig. 8, the command in the sequence N08 in this example is “G128 P2 Z-30.K10.F2.”, which is different from the one in the Fig. 4. A code "G128 P2" is an eccentric cutting control phase shift command, "Z" defines the amount of movement of the body axis (in this example, 30 mm in the Z-axis direction), "K" defines the amount of change in eccentricity in the radial direction (in this example, 10 mm), and "F" defines a synchronous feedrate (in this example, 2 mm / revolution). The amount of change in eccentricity in the radial direction, that is, the eccentricity change value "K", is an eccentricity increase / decrease value.

[0080] In this NC program, the Fig. 9 are carried out by cooperation between the eccentric removal control unit 27 and the control unit 23. Fig. Fig. 9 is a flowchart showing examples of processes performed by the eccentric cutting control unit and the control unit of the first modification. It should be noted that in the Fig. 9, the processes of steps S16 and S17 after step S13 of the process shown in Fig. 5 are executed and other processes are the same as those shown in Fig. 5. Accordingly, only the processes of steps S16 and S17 will be described below, and the description of other processes will be omitted.

[0081] If it is determined in step S13 that the eccentric cutting control command has not been received (in a case of NO in step S13), the control unit 23 determines whether an eccentric cutting control phase shift command and information thereon have been received from the program analysis unit 22 (step S16). If it is not determined that the eccentric cutting control phase shift command and information thereon have been received from the program analysis unit 22 (in a case of NO in step S16), the processes from step S4 onwards are executed.

[0082] If it is determined that the eccentric cutting control phase shift command and the information thereon have been received from the program analysis unit 22 (in a case, YES in step S16), the eccentric cutting control unit 27 additionally calculates the eccentric arc movement values ​​in shift control and sends them to the control unit 23 (step S17). Specifically, the eccentric cutting control unit 27 calculates an eccentric arc operation increase / decrease value, calculates the final eccentric arc movement values ​​obtained by adding the eccentric arc operation increase / decrease value to the eccentric arc movement values ​​calculated in step S5, and sends them to the control unit 23.

[0083] The values ​​of the eccentric arc movement ΔX and ΔY are calculated based on the value of the movement Z of the body axis, the value of the eccentricity change K, and the synchronous feed rate F as follows.

[0084] First, ΔR is expressed as the value of the change in eccentricity R per unit time by the following formula (11). Here, ΔZ is the value of the movement of the body axis per unit control time T and is calculated based on the synchronous feed rate F. Formula 3: ΔR=K×ΔZLengZ

[0085] Consequently, the eccentricity R used in formulas (9) and (10) becomes the eccentricity R taking into account the value of the eccentricity change K in the Z-axis direction, as given by the following formula (12). Formula 4: R=R+ΔR =R+K×ΔZLengZ

[0086] Accordingly, the values ​​of the eccentric arc movement ΔX and ΔY can be calculated by formulas (13) and (14) instead of formulas (9) and (10). ΔX=(R+ΔR)cos(Δθ) ΔY=(R+ΔR)sin(Δθ)

[0087] The eccentric cutting control unit 27 cooperates with the control unit 23 to relatively move the tool T using the eccentricity R given by the formula (12). According to the first modification, therefore, the eccentric body Wb2 of the workpiece W2 can be machined as shown in Fig. 7 shown. Second variation

[0088] Next, a second variation is described. In the second variation, a Fig. 10 shown workpiece W3 machined. Fig. 10 is an explanatory view showing an example of an outline of eccentric cutting according to the second modification of the present embodiment. The workpiece W3 includes a base part Wa3 having a cylindrical shape and an eccentric body Wb3 projecting from a front end surface of the base part Wa3 in the Z-axis direction and formed at a position radially offset by the eccentricity R from an axis of the base part Wa3. The eccentric body Wb3 has a shape whose axis is spirally wound along the Z-axis direction, that is, a shape in which an eccentric phase increases and decreases in the Z-axis direction. The workpiece W3 is a component used for a progressive cavity pump as a type of positive displacement rotary displacement pump.

[0089] Fig. 11 is an explanatory diagram showing an example of an NC program according to the second modification. Fig. 11 shows an example of the NC program for machining the eccentric body Wb3 of the workpiece W3 of the Fig. 10. As in Fig. 11, the command in sequence N08 in this example is “G128 P2 Z-90.Q1080.F2.”, which is different from the one in the Fig. 4. The code "G128 P2" is an eccentric cutting control phase shift command, "Z" defines the amount of movement of the body axis (in this example, 90 mm in the Z-axis direction), "Q" defines the amount of eccentric phase change (in this example, 1080° (for three pitches)), and "F" defines a synchronous feedrate (in this example, 2 mm / revolution). The eccentric phase change value "Q" is a phase increase / decrease value of the eccentricity.

[0090] In this NC program, the values ​​of the eccentric arc movement in the displacement control are controlled by the eccentric cutting control unit 27 and the control unit 23 from the eccentric cutting control unit 27 in the process of the Fig. 9 and sent to the control unit 23.

[0091] That is, the values ​​of the eccentric arc movement ΔX and ΔY are calculated from the value of the movement LengZ of the body axis, the value of the eccentric phase change Q and the synchronous feed rate F as follows.

[0092] First, Δϕ is expressed as a value of phase change per unit control time T by the following formula (15). Note that ΔZ is the value of the body axis movement per unit control time T and is calculated from the synchronous feed rate F. Formula 5: Δϕ=Q×ΔZLengZ

[0093] Since the phase of the eccentric body Wb3 in each of the formulas (9) and (10) is the sum of the shaft rotation angle Δθ per unit control time T and the phase change value Δϕ per unit time, as given by the following formula (16), the values ​​of the eccentric arc movement ΔX and ΔY are calculated by the following formulas (16) and (17) and sent to the control unit 23. ΔX=Rcos(Δθ+Δϕ) ΔY=Rsin(Δθ+Δϕ)

[0094] Note that the angle from the X-axis at any time with respect to the shaft rotation speed command S is θ, and the shaft rotation angle per unit control time T with respect to the shaft rotation speed command S is Δθ. The values ​​of the movement of X and Y per unit control time T are expressed by formulas (9) and (10). The phase change value Δϕ per unit time is expressed by formula (15), and the values ​​of the movement obtained by adding the phase change value Δϕ per unit time are expressed by formulas (16) and (17). From the above, the command positions X and Y on the X-axis and the Y-axis in the eccentric arc movement expressed by formulas (1) and (2) are expressed by the following formulas (18) and (19), respectively. Formula 6: X=Rcos θ=Rcos(θ+ϕ)=Rcos(θ+Q×ZLengZ) Formula 7: Y=Rsin θ=Rsin(θ+ϕ)=Rsin(θ+Q×ZLengZ)

[0095] According to the second modification, the eccentric body Wb3 of the workpiece W3 can be machined as shown in the Fig. 10 shown.

[0096] As described above, by not only changing the eccentricity conditions when the eccentric removal control command is given, but also changing the eccentricity conditions in synchronization with the movement in the Z-axis direction, the Fig. 6, Fig. 7 and Fig. 10 can be easily machined. Such changes in the eccentricity conditions can be made by issuing an eccentric cutting control shift command in addition to the eccentric cutting control command.

[0097] Although the specific embodiment of the present disclosure has been described above, aspects that can be implemented by the present disclosure are not limited to the above examples.

[0098] Although some information about the eccentric cutting is given by the NC code in the above examples, there is no limitation in this respect, and an aspect may be additionally implemented in which the information is set as a parameter and stored in the parameter storage unit 26.

[0099] In addition, although the switching to the position control mode is performed by the code “M45” instructed in the NC program in the above examples, the control unit 23 may autonomously perform the switching to the position control mode to perform the positioning.

[0100] It should be noted again that the above description of the embodiment is illustrative and not restrictive in all respects. Modifications and changes can be appropriately made by those skilled in the art. For example, a combination with other known technology may be made, and some configurations may be omitted or changed without departing from the gist thereof. The scope of the present disclosure is not defined by the above-described embodiment, but by the claims. Furthermore, the scope of the present disclosure includes modifications of the embodiment within the scope of the claims. List of reference symbols 1 machine tool; 2nd wave; 3 clamping device; 4 tool holder; 10 drive unit; 11 feed drive unit; 12 X-axis feed drive unit; 13 Y-axis feed drive unit; 14 Z-axis feed drive unit; 15 Shaft drive unit; 20 control device; 21 NC program storage unit; 22 Program analysis unit; 23 control unit; 24 feed control unit; 25 shaft control unit; 26 parameter storage unit; 27 Eccentric removal control unit; 30 Input / output device.

Claims

[1] A control device (20) that controls operations of a shaft drive unit (15) and a feed drive unit (11) of a machine tool (1) comprising a shaft (2) for supporting and rotating a workpiece (W), a tool holder (4) for supporting a tool (T), the shaft drive unit (15) for rotating the shaft (2), and the feed drive unit (11) for relatively moving the tool holder (4) and the shaft (2) along a Z-axis coincident with an axis of the shaft (2), an X-axis orthogonal to the Z-axis, and a Y-axis orthogonal to the Z-axis and the X-axis, the control device (20) comprising: a control unit (23) for controlling the shaft drive unit (15) and the feed drive unit (11); and an eccentric removal control unit (27) for machining an eccentric body (Wb) provided at a position in the workpiece (W) carried by the shaft (2), the position being radially offset from a center of the shaft (2), where the eccentric removal control unit (27) is configured to rotate the shaft (2) together with the control unit (23) to position a position of the center of the eccentric body (Wb) so that it lies on the X-axis, then to calculate values ​​of the movement in an arc movement in which arc loci are formed using the following formulas (1) and (2) X=R cosθ Y=R sinθ satisfying values ​​for a position at which the position of the center of the eccentric body (Wb) has been positioned so as to lie on the X-axis, and to move the tool holder (4) and the shaft (2) relatively in the direction of the Z-axis, while the tool holder (4) and the shaft (2) are relatively moved in synchronization with the rotation of the shaft (2) so that the calculated values ​​of the movement are achieved in the arc movement, with an eccentricity denoted by R, which is a distance between a center of the shaft (2) and a center of the eccentric body (Wb), and an angle of rotation denoted by θ of the center of the eccentric body (Wb) around the axis of the shaft (2) with the X-axis as a reference; and in a case where the eccentric body (Wb) is a spiral along the direction of the Z-axis, the eccentric removal control unit (27) is configured, together with the control unit (23), to relatively move the tool holder (4) and the shaft (2), with a length of the eccentric body (Wb) in the Z-axis direction denoted by LengZ and a phase increase / decrease value of the eccentricity in the Z-axis direction denoted by Q, and further in synchronization with a feed distance ΔZ in the Z-axis direction per unit time, with a phase change value Δϕ per unit time satisfying the following formula (3): Δϕ=Q×ΔZLengZ [2] A control device (20) that controls operations of a shaft drive unit (15) and a feed drive unit (11) of a machine tool (1) comprising a shaft (2) for supporting and rotating a workpiece (W), a tool holder (4) for supporting a tool (T), the shaft drive unit (15) for rotating the shaft (2), and the feed drive unit (11) for relatively moving the tool holder (4) and the shaft (2) along a Z-axis coincident with an axis of the shaft (2), an X-axis orthogonal to the Z-axis, and a Y-axis orthogonal to the Z-axis and the X-axis, the control device (20) comprising: a control unit (23) for controlling the shaft drive unit (15) and the feed drive unit (11); and an eccentric removal control unit (27) for machining an eccentric body (Wb) provided at a position in the workpiece (W) carried by the shaft (2), the position being radially offset from a center of the shaft (2), where the eccentric removal control unit (27) is configured to rotate the shaft (2) together with the control unit (23) to position a position of the center of the eccentric body (Wb) so that it lies on the X-axis, then to calculate values ​​of the movement in an arc movement in which arc loci are formed using the following formulas (1) and (2) X=R cosθ Y=R sinθ satisfying values ​​for a position at which the position of the center of the eccentric body (Wb) has been positioned so as to lie on the X-axis, and to move the tool holder (4) and the shaft (2) relatively in the direction of the Z-axis, while the tool holder (4) and the shaft (2) are relatively moved in synchronization with the rotation of the shaft (2) so that the calculated values ​​of the movement are achieved in the arc movement, with an eccentricity denoted by R, which is a distance between a center of the shaft (2) and a center of the eccentric body (Wb), and an angle of rotation denoted by θ of the center of the eccentric body (Wb) around the axis of the shaft (2) with the X-axis as a reference; and in a case where the eccentric body (Wb) is a spiral along the direction of the Z-axis, the eccentric removal control device (27) is configured, together with the control unit (23), to relatively move the tool holder (4) and the shaft (2), with a length of the eccentric body (Wb) denoted by LengZ in the Z-axis direction and an eccentricity increase / decrease value denoted by K in the Z-axis direction, and further in synchronization with a feed distance ΔZ in the Z-axis direction per unit time, with the eccentricity R satisfying the following formula (4): R=R+K×ΔZLengZ [3] Control device (20) according to claim 1 or 2, wherein the control unit (23) is configured to be able to execute three control modes, which include a speed control mode in which the shaft (2) is rotated at a predetermined rotational speed, a position control mode in which the shaft (2) is positioned at a predetermined rotational angular position about the axis of the shaft (2), and a synchronous control mode in which an operation of the shaft drive unit (15) and an operation of the feed drive unit (11) are synchronized with each other, and wherein the eccentric cutting control unit (27) is configured to synchronize the operation of the shaft drive unit (15) and the operation of the feed drive unit (11) by causing the control unit (23) to switch to the synchronous control mode. [4] Control device (20) according to one of claims 1 to 3, wherein the control device (20) is configured to perform a turning operation via at least the control unit (23) without synchronization between the operation of the shaft drive unit (15) and the operation of the feed drive unit (11), and wherein the eccentric removal control unit (27) is configured to carry out a pre-control on the feed drive unit (11) together with the control unit (23). [5] Control device (20) according to one of claims 1 to 4, wherein the eccentric removal control unit (27) is configured, together with the control unit (23), to control a combined speed of a feed speed of the feed drive unit (11) and an angular speed in the sheet movement so that it is less than or equal to a predetermined speed limit, and wherein the combined speed is set such that a load of the feed drive unit (11) does not exceed a permissible load. [6] Control device (20) according to one of claims 1 to 4, wherein the eccentric removal control unit (27) is configured, together with the control unit (23), to control an acceleration of a uniform circular movement in the arc movement so that it is less than or equal to a predetermined acceleration limit, and wherein the acceleration limitation is set such that a load of the feed drive unit (11) does not exceed a permissible load. [7] Machine tool (1), comprising: a shaft (2) for supporting and rotating a workpiece (W), a tool holder (4) for supporting a tool (T), a shaft drive unit (15) for rotating the shaft (2), and a feed drive unit (11) for relatively moving the tool holder (4) and the shaft (2) along a Z-axis coinciding with an axis of the shaft (2), an X-axis orthogonal to the Z-axis, and a Y-axis orthogonal to the Z-axis and the X-axis; and the control device (20) according to one of claims 1 to 6.

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