Machine tool control device and machine tool control method

Abstract

The present invention provides a control device and a control method for a machine tool capable of performing oscillating cutting that makes the cut lines less noticeable. The control device of the machine tool controls the machine tool that uses a cutting tool to cut a workpiece by coordinating the actions of a main shaft and a feed shaft, and comprises: a feed instruction calculation unit that calculates a feed instruction for moving the feed shaft relative to the workpiece; an oscillation phase calculation unit that calculates the phase of the oscillation that causes the feed shaft to reciprocate based on the rotation speed of the main shaft, that is, the oscillation phase; an oscillation phase correction unit that corrects the oscillation phase; an oscillation amplitude calculation unit that calculates the amplitude of the oscillation that causes the feed shaft to reciprocate based on the feed instruction; an oscillation instruction calculation unit that calculates the oscillation instruction that causes the feed shaft to reciprocate based on the oscillation phase and the oscillation amplitude corrected by the oscillation phase correction unit; and an instruction synthesis unit that overlaps the feed instruction and the oscillation instruction and calculates a synthesis instruction for driving the feed shaft.

Description

Technical Field

[0001] The invention relates to a control device of a machine tool and a control method of a machine tool. Background Art

[0002] Conventionally, a machine tool such as a lathe has been used that has a spindle and a feed axis that rotate the cutting tool and the workpiece relative to each other and that moves the cutting tool and the workpiece relative to each other in a predetermined feed direction, thereby performing cutting processing on a workpiece using a cutting tool in coordination with the spindle and the feed axis.

[0003] In such lathes and other machine tools, the cutting tool tip usually continuously removes material from the surface of the workpiece. Therefore, depending on the material of the workpiece, there is a possibility that the removed material becomes long and thin chips (chips) that are entangled with the cutting tool and hinder the processing of the workpiece. In contrast, as described in, for example, Patent Document 1, it is known to use a numerical control device to perform swing cutting with a predetermined number of vibrations to make the cutting tool reciprocate relative to the workpiece. In swing cutting, the cutting tool is reciprocated in such a way that the trajectory of the cutting tool at the i-th rotation of the spindle intersects with the trajectory of the cutting tool at the (i+1)-th rotation. As a result, since the cutting tool is periodically separated from the workpiece, the chips can be cut into pieces of a constant length.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2019-40252

[0007] Problems to be solved by the invention

[0008] In the swing cutting described in Patent Document 1, the instruction for relatively feeding the cutting tool and the workpiece is calculated by superimposing a sinusoidal swing instruction on a linear feed instruction. When a sinusoidal swing instruction is superimposed on a constant speed feed instruction, the spindle phase of the top of the peak (the maximum point of the coordinate value) and the lowest point of the trough (the minimum point of the coordinate value) relative to the trajectory of the position of the cutting tool with the feed direction as the up and down direction is the spindle phase of the swing instruction. That is, the point where the position of the cutting tool becomes the peak is slightly behind the point of the peak of the swing instruction in the spindle rotation direction, and the point where the position of the cutting tool becomes the trough is slightly ahead of the point of the trough of the swing instruction in the spindle rotation direction.

[0009] In cutting processing, a pattern called cut marks caused by the movement of the cutting tool can be formed on the cutting surface. In the swing cutting described in Patent Document 1, the spindle angle at which the cutting tool position becomes the top of the wave crest in the i-th rotation of the spindle is staggered from the spindle angle at which the cutting tool position becomes the lowest point of the wave trough in the (i+1)-th rotation of the spindle, thereby increasing the time for the cutting tool to be separated from the workpiece and increasing the idle rotation, so that the cut marks are sometimes easily noticeable. Therefore, a control device for a machine tool capable of swing cutting in which the cut marks are difficult to be noticeable is desired. Summary of the invention

[0010] Means for Solving the Problems A control device for a machine tool according to one embodiment of the present invention is a control device for controlling a machine tool, the machine tool having a spindle for rotating a cutting tool and a workpiece relative to each other and a feed shaft for moving the cutting tool and the workpiece relative to each other, and causing the spindle and the feed shaft to cooperate with each other to perform cutting processing on the workpiece using the cutting tool, the control device for the machine tool comprising: a feed command calculation unit for calculating a feed command for moving the feed shaft relative to the workpiece; a swing phase calculation unit for calculating a swing phase, which is a phase of swing for causing the feed shaft to reciprocate, based on a rotation speed of the spindle; a swing phase correction unit for correcting the swing phase; a swing amplitude calculation unit for calculating an amplitude of swing for causing the feed shaft to reciprocate, that is, a swing amplitude, based on the feed command; a swing command calculation unit for calculating a swing command for causing the feed shaft to reciprocate, based on the swing phase and the swing amplitude corrected by the swing phase correction unit; and a command synthesis unit for superimposing the feed command and the swing command to calculate a synthesized command for driving the feed shaft.

[0011] Effects of the Invention

[0012] According to the present invention, oscillating cutting in which the cut lines are hardly noticeable can be performed. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a schematic diagram showing the structure of a machine tool including the numerical controller according to the first embodiment of the present disclosure.

[0014] Figure 2 Yes means Figure 1 A block diagram showing the detailed structure and signal flow involved in the control of the feed axis motor of a numerical control device.

[0015] Figure 3 Yes means Figure 1 Flowchart of the control sequence in the numerical control device.

[0016] Figure 4 is an example Figure 1A graph showing the time variation of tool position instructions generated by a numerical control device.

[0017] Figure 5 This is a block diagram showing the configuration and signal flow of a numerical control device according to the second embodiment of the present disclosure.

[0018] Description of reference numerals:

[0019] 1, 1A numerical control device, 11 program storage unit, 12 feed instruction calculation unit, 13 swing phase calculation unit, 14 swing amplitude calculation unit, 15 swing instruction calculation unit, 16 swing phase correction unit, 17 instruction synthesis unit, 18 position speed control unit, 19 current control unit, 20 position deviation calculation unit, 21 integration unit, 22 learning controller, 23 learning correction value addition unit, 24 swing amplitude correction unit, 100 machine tool, Ac spindle, Az feed axis, T cutting tool, W workpiece DETAILED DESCRIPTION

[0020] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Figure 1 1 is a schematic diagram showing a configuration of a machine tool 100 including a numerical controller 1 according to a first embodiment of a machine tool control device of the present disclosure.

[0021] The machine tool 100 is an NC lathe that performs cutting processing on a workpiece W as a processing object using a cutting tool T. The machine tool 100 has three drive axes, namely, a spindle Ac that rotates the cutting tool T or the workpiece W (rotates the workpiece W in this embodiment), a feed axis Az that moves the cutting tool T relative to the workpiece W in a direction parallel to the rotation axis of the spindle Ac (moves the cutting tool T in this embodiment), and a cutting axis Ax that moves the cutting tool T relative to the workpiece W in the radial direction of the spindle Ac (moves the cutting tool T in this embodiment). Therefore, the machine tool 100 has drive motors (spindle motor Mc, feed axis motor Mz, and cutting axis motor Mx) that drive these drive axes Ac, Az, and Ax.

[0022] The numerical controller 1 controls the machine tool 100 so that the main axis Ac, the feed axis Az, and the cutting axis Ax operate in coordination and cut the workpiece W using the cutting tool T. The numerical controller 1 can be implemented by causing a computer device including a CPU, a memory, and the like to execute an appropriate program.

[0023] like Figure 2As shown in FIG. 1 , the numerical control device 1 includes a program storage unit 11 for storing a machining program, a feed command calculation unit 12 for calculating a feed command for moving the feed axis Az, a swing phase calculation unit 13 for calculating a swing phase, which is a phase of the swing of the feed axis Az, based on the rotation speed of the spindle Ac, a swing amplitude calculation unit 14 for calculating an amplitude of the swing for reciprocating the feed axis based on the feed command, a swing command calculation unit 15 for calculating a swing command for periodically reciprocating the feed axis Az based on the swing phase and the swing amplitude, a swing phase correction unit 16 for correcting the swing phase calculated by the swing phase calculation unit 13, and a command synthesis unit 17 for superimposing the feed command and the swing command and calculating a synthesis command for driving the feed axis Az. Furthermore, the numerical control device 1 includes a position speed control unit 18, a current control unit 19, a position deviation calculation unit 20, an integration unit 21, a learning controller 22, and a learning correction value addition unit 23. These components are functionally distinct elements, and may not be clearly distinguishable in terms of physical structure or program structure.

[0024] The program storage unit 11 stores a machining program. For example, the machining program can be described by G code or the like.

[0025] The feed instruction calculation unit 12 calculates a feed instruction for moving the feed axis Az according to the machining program. The feed instruction can be used as an instruction for specifying the Z-direction position of the cutting tool T at each time and causing the Z-direction position of the cutting tool T to increase linearly over time. Specifically, if the feed amount of the feed axis Az (cutting tool T) per rotation of the spindle Ac is set to F [mm], the rotation speed of the spindle Ac is set to S [rpm], and the time is set to t [sec], then when the feed speed of the feed axis Az is constant, the feed instruction calculation unit 12 can calculate the feed instruction Ps (t) by the following formula (1).

[0026] Ps(t)=(FS / 60)·t…(1)

[0027] The swing phase calculation unit 13 calculates the phase (swing phase) θ(t) [rad] of the swing that causes the feed axis Az to reciprocate at a period corresponding to the rotation speed of the spindle Ac. The swing phase calculation unit 13 can calculate the swing phase θ(t) as a value proportional to time. Specifically, the swing phase θ(t) can be calculated by the following formula (2) using a constant (frequency multiplier) I that specifies the number of reciprocating motions of the feed axis per rotation of the spindle Ac. When I is 0.5+m (a non-negative integer), the chips can be efficiently crushed.

[0028] θ(t)=(2πSI / 60)·t…(2)

[0029] The swing amplitude calculation unit 14 calculates the swing amplitude A of the feed axis Az reciprocating at a period corresponding to the rotation speed of the spindle Ac. Specifically, the swing amplitude A can be calculated by the following formula (3) by setting the feed amount of the feed axis Az (cutting tool T) per rotation of the spindle Ac to F [mm] and using a constant (swing amplitude magnification) K (a real number greater than 1).

[0030] A=KF / 2…(3)

[0031] The swing command calculation unit 15 calculates the swing command Po(t) for causing the feed axis Az to reciprocate based on the swing phase θ(t) (the swing phase θ(t) corrected by the swing phase correction unit 16 described later). The swing command Po(t) can be expressed as the swing component of the position of the feed axis Az at each time (the displacement from the position when there is no swing). The swing command calculation unit 15 can set the swing command Po(t) to a value obtained by multiplying the sine (sinθ) or cosine (cosθ) of the swing phase θ(t) by a constant (swing amplitude) A[mm]. In addition, in order to prevent cutting caused by swinging, the swing command calculation unit 15 can also offset the swing command Po(t) so that the maximum value of the swing component is "0". Specifically, the swing command calculation unit 15 can also set the feed amount of the feed axis Az (cutting tool T) per rotation of the spindle Ac to F[mm] and use the amplitude magnification K to calculate the swing command Po(t) by the following formula (4).

[0032] Po(t)=(KF / 2)cos(θ(t))-(KF / 2)…(4)

[0033] The swing phase correction unit 16 corrects the swing phase θ(t) calculated by the swing phase calculation unit 13. For example, if the swing phase is advanced when the trajectory of the position of the feed axis Az in the synthetic command is on the side of the upward convex peak (in the range of 0 to 90 degrees and 270 to 360 degrees in the swing phase), and the swing phase is delayed when the position of the feed axis Az in the synthetic command is on the side of the downward convex trough (in the range of 90 to 270 degrees in the swing phase), the phase of the spindle Ac where the position of Az in the synthetic command is the top of the peak (the coordinate is the maximum) can be made close to the phase of the spindle Ac where the position of Az in the synthetic command is the lowest point of the trough (the coordinate is the minimum). In this way, by making the rotational position of the spindle Ac corresponding to the top of the peak and the lowest point of the trough of the position of the feed axis Az coincide, the cut line formed on the cutting surface of the workpiece W is not noticeable. In addition, as for the judgment of whether to advance or retard the swing phase, an assumed command that is assumed to be a synthetic command when no correction is performed may be calculated, the acceleration of the feed axis Az in the case of the assumed command may be calculated, and the judgment of whether to advance or retard the swing phase may be made based on the acceleration. If the swing phase is advanced when the acceleration is negative and the swing phase is retarded when the acceleration is positive, the phase of the main axis Ac where the position of Az in the synthetic command is the top of the peak (the coordinate is the maximum) can be made close to the phase of the main axis Ac where the position of Az in the synthetic command is the lowest point of the trough (the coordinate is the minimum).

[0034] The correction may be performed by adding a correction amount Δθ(t) that changes sinusoidally with respect to time t to the swing phase θ(t) calculated by the swing phase calculation unit 13. This prevents the swing command from changing discontinuously, and prevents the formation of unnatural cuts and mechanical vibrations due to the correction. In this case, the swing phase correction unit 16 may make the phase of the correction amount Δθ(t) equal to the swing phase θ(t) calculated by the swing phase calculation unit 13. This makes it relatively easy to calculate the correction amount that makes the rotational position of the spindle corresponding to the top of the peak and the lowest point of the trough of the position of the feed axis Az consistent.

[0035] Specifically, the swing phase correction unit 16 can set the amplitude of the sinusoidal correction amount Δθ(t) to a value (1 / πKI) obtained by dividing 1 by the amplitude magnification K, the frequency magnification I, and the circumference π. That is, the correction amount Δθ(t) of the swing phase θ(t) can be calculated by the following formula (5). By using such a calculation formula, the rotation position of the spindle Ac corresponding to the top of the peak and the lowest point of the trough of the position of the feed axis Az can be made to match more accurately.

[0036] Δθ(t)=1 / πKI·cos(2πSI / 60·t)…(5)

[0037] The command synthesis unit 17 calculates the synthesis command Pc(t)[mm] for driving the feed axis Az by overlapping the feed command calculated by the feed command calculation unit 12 and the swing command calculated by the swing command calculation unit 15. If the above-mentioned calculation formulas are used, the following formula (6) can be used for calculation. As shown in formula (6), the feed command calculation unit 12, the swing phase calculation unit 13, the swing command calculation unit 15, and the swing phase correction unit 16 can also exist as part of the calculation formula of the command synthesis unit 17.

[0038] Pc(t)=Ps(t)+Po(t)=FS / 60·t+(KF / 2)cos(θ+Δθ)-(KF / 2)=FS / 60·t+(KF / 2)cos(2πSI / 60·t+1 / πKI·cos(2πSI / 60·t))-(KF / 2)…(6)

[0039] Here, the correction of the swing phase by the swing phase correction unit 16 is described in detail. When the position of the feed axis Az is the top of the peak or the lowest point of the trough, the differential value (the slope of the graph) of the synthesis command Pc (t) is "0". According to the above calculation formula, the synthesis command Pc (t) without correction by the swing phase correction unit 16 is the following formula (7).

[0040] Pc(t)=FS / 60·t+(KF / 2)cos(2πSI / 60·t)-(KF / 2)…(7)

[0041] When the synthesis instruction Pc(t) of equation (7) is differentiated, the following equation (8) is obtained.

[0042] Pc(t)·t / dt=FS / 60·(1-πKIsin(2πSI / 60·t))…(8)

[0043] If the differential value Pc(t)·t / dt is set to "0", it can be derived that 2πSI / 60·t=nπ+1 / πKI·(-1) n This is the relationship of the following formula (9) (n is an integer). Therefore, by advancing the swing phase when the position of the feed axis Az is at the top of the peak by only 1 / πKI·2nπ, and delaying the swing phase when the position of the feed axis Az is at the lowest point of the trough by only 1 / πKI·(2n+1)π, the phase of the main axis Ac at the top of the peak and the lowest point of the trough of the feed axis Az can be made consistent. Therefore, when the position of the feed axis Az is at the top of the peak, that is, when the corrected swing phase Δθ(t) is 0, the correction amount Δθ(t) of the swing phase θ(t) is +1 / πKI, and when the corrected swing phase Δθ(t) is π and the position of the feed axis Az is at the lowest point of the trough, the correction amount Δθ(t) of the swing phase θ(t) is -1 / πKI.

[0044] 2πSI / 60·t=nπ+1 / πKI·(-1) n …(9)

[0045] Based on the above, the swing command calculation unit 15 may set the swing command Po(t) to the following equation (10). As shown in equation (10), the swing phase correction unit 16 may exist as a part of the calculation equation of the swing command calculation unit 15.

[0046] Po(t)=(KF / 2)cos((2πS / 60)·I·t+cos(2πS / 60·I·t) / πKI)-(KF / 2)…(10)

[0047] The position and speed control unit 18 converts the command position into the rotation speed of the feed axis motor Mz. The configuration of the position and speed control unit 18 is well-known, and therefore detailed description thereof will be omitted.

[0048] The current control unit 19 controls the current applied to the feed axis motor Mz so that the feed axis motor Mz rotates at the rotation speed calculated by the position speed control unit 18. The current control unit 19 may be, for example, a known servo amplifier that performs vector control.

[0049] The position deviation calculation unit 20 calculates a deviation between the position of the feed axis motor Mz indicated by the current feed command and the actual position fed back from the feed axis motor Mz.

[0050] The integrating unit 21 integrates the position deviation calculated by the position deviation calculating unit 20 .

[0051] The learning controller 22 calculates a command correction value to be given to the position-speed control unit 18 based on past position deviations.

[0052] The learned correction value adding unit 23 adds the correction value calculated by the learning controller 22 to the movement command for the position and speed control unit 18 .

[0053] The wobble amplitude correction unit can change the value of the constant K in order to prevent a decrease in the wobble amplitude caused by a change in the wobble phase resulting from adding the correction calculated by the wobble phase correction unit 16 to the wobble phase.

[0054] and, Figure 3 , the control sequence of the feed axis Az by the numerical control device 1 is shown. This control sequence is one embodiment of the machine tool control method of the present invention. The numerical control device 1 controls the main axis Ac and the cutting axis Ax synchronously with the control of the feed axis Az, but the control of the drive axis other than the feed axis Az is the same as before, so the detailed description is omitted.

[0055] The control of the feed axis Az performed by the numerical control device 1 includes: a process of calculating the feed instruction of the feed axis Az (step S1: feed instruction calculation process), a process of calculating the swing phase (step S2: swing phase calculation process), a process of correcting the swing phase (step S3: swing phase correction process), a process of generating a swing instruction based on the corrected swing phase (step S4: swing instruction calculation process), a process of calculating a composite instruction by overlapping the feed instruction and the swing instruction (step S5: composite instruction calculation process) and a process of controlling the feed axis motor Mz according to the composite instruction (step S6: motor control process).

[0056] In the feed command calculation step of step S1 , the feed command calculation unit 12 calculates a feed command Ps(t) for the feed axis Az based on the feed amount of the feed axis Az and the rotation speed of the spindle Ac specified in the machining program.

[0057] In the swing phase calculation step of step S2, the swing phase calculation unit 13 calculates a swing phase θ(t) serving as a reference for the reciprocating motion component of the feed axis Az.

[0058] In the wobble phase correction process of step S3 , the wobble phase correction unit 16 calculates a wobble phase correction amount Δθ(t), and adds the wobble phase θ(t) calculated by the wobble phase calculation unit 13 .

[0059] In the swing command calculation step of step S4 , the swing command calculation unit 15 calculates the swing command Po(t).

[0060] In the combined command calculation step of step S5 , the command combining unit 17 adds Ps(t) to the swing command Po(t) to calculate the combined command Pc(t).

[0061] In the motor control process of step S6 , the position and speed control unit 18 and the current control unit 19 control the feed axis motor Mz in consideration of the correction of the learning controller 22 .

[0062] Figure 4 , the feed command, the synthetic command calculated based on the swing phase before correction, and the change in the rotation angle of the feed axis Az relative to the spindle Ac in the synthetic command calculated based on the swing phase after correction, that is, the trajectory of the cutting tool T in the machined surface of the workpiece W. In the drawings, the feed command is represented by a single-dot chain line, the synthetic command before the swing phase correction is represented by a dotted line, and the synthetic command after the swing phase correction is represented by a solid line.

[0063] As shown in the figure, when the swing phase is not corrected, the rotation angle from the angular position of the spindle Ac where the position of the feed axis Az is the lowest point of the trough to the angular position of the spindle Ac where the position of the feed axis Az is the apex of the peak is greater than the rotation angle from the angular position of the spindle Ac where the position of the feed axis Az is the apex of the peak to the angular position of the spindle Ac where the position of the feed axis Az is the lowest point of the trough. On the other hand, the synthetic command calculated based on the corrected swing phase makes the angular position of the spindle Ac where the position of the feed axis Az is the apex of the peak in the first rotation and the angular position of the spindle Ac where the position of the feed axis Az is the lowest point of the trough in the second rotation more accurately match.

[0064] Thus, the numerical control device 1 relatively accurately matches the angular position of the spindle Ac where the feed axis Az is at the top of the peak with the angular position of the spindle Ac where the feed axis Az is at the lowest point of the trough, thereby enabling oscillating cutting with less noticeable cut lines.

[0065] In addition, when the numerical control device 1 of the present embodiment including the swing phase correction unit 16 is used, the swing phase correction unit 16 operates as follows. Figure 4 As shown, the time during which the cutting tool T is separated from the workpiece W is shorter than in the case of conventional oscillating cutting. Therefore, it is preferable to set the oscillation amplitude magnification K to a slightly larger value in the numerical control device 1 of the present embodiment.

[0066] then, Figure 5 It is shown in Figure 1 100 of the machine tools can replace Figure 2 A numerical control device 1A is used as the numerical control device 1 of the present invention. Figure 5 The numerical control device 1A is a second embodiment of the numerical control device of the present invention. Figure 5 The numerical control device 1A may sometimes be used for Figure 1 The same reference numerals are used to denote the common components of the numerical control device 1 and duplicate descriptions thereof will be omitted.

[0067] The numerical controller 1A includes a program storage unit 11 storing a machining program, a feed command calculation unit 12 calculating a feed command for moving a feed axis Az, a swing phase calculation unit 13 calculating a swing phase, which is a phase of swing of the feed axis Az, based on the rotation speed of the spindle Ac, a swing amplitude calculation unit 14 calculating an amplitude of swing for reciprocating the feed axis based on the feed command, a swing command calculation unit 15 calculating a swing command for periodically reciprocating the feed axis Az based on the swing phase, a swing phase correction unit 16 correcting the swing phase calculated by the swing phase calculation unit 13, and a swing amplitude correction unit 24 correcting the swing amplitude calculated by the swing amplitude calculation unit. The numerical controller 1A also includes a position speed control unit 18, a current control unit 19, a position deviation calculation unit 20, an integration unit 21, a learning controller 22, and a learning correction value addition unit 23.

[0068] In the numerical control device 1A, the swing command calculation unit 15 calculates the swing command based on the swing phase corrected by the swing phase correction unit 16 and the swing amplitude corrected by the swing amplitude correction unit 24. When the swing phase is corrected by the swing phase correction unit 16, the cut line can be made less noticeable than when the swing phase is not corrected, but the time of overlap with the trajectory of the position of the feed axis Az, that is, the time of separation of the cutting tool T from the workpiece W becomes shorter, so the cutting of the chips may become unreliable. However, the numerical control device 1A includes the swing amplitude correction unit 24, which can correct the swing amplitude in such a way that the time of separation of the cutting tool T from the workpiece W does not become shorter even if the swing phase is corrected by the swing phase correction unit 16, so the chips can be reliably cut.

[0069] The embodiments of the present disclosure are described above, but the present invention is not limited to the above embodiments. In addition, the effects described in the embodiments are merely the most preferred effects produced by the present invention, and the effects of the present invention are not limited to the effects described in the embodiments.

[0070] In the numerical control device disclosed in the present invention, the correction amount of the state swing phase is not limited to a sinusoidal amount, and any amount that changes periodically and continuously may be used. For example, it may be a linearly changing value that alternately connects an upward convex arc and a downward convex arc. In addition, the amplitude of the correction amount of the swing phase may be specified by the user based on experience, for example.

[0071] In addition, the numerical control device of the present disclosure is not limited to lathes, and can also be applied to the control of other types of machine tools such as drilling machines.

Claims

1. A control device for a machine tool, the control device controlling the machine tool having a main shaft for rotating a cutting tool and a workpiece relative to each other and a feed shaft for moving the cutting tool and the workpiece relative to each other, and making the main shaft and the feed shaft work in coordination to perform cutting processing on the workpiece using the cutting tool, It is characterized in that The control device of the machine tool comprises: a feed command calculation unit that calculates a feed command for moving the feed axis relative to the workpiece; a swing phase calculation unit that calculates a swing phase, which is a phase of swing that causes the feed shaft to reciprocate, based on the rotation speed of the spindle; a swing phase correction unit, which corrects the swing phase; a swing amplitude calculation unit that calculates the swing amplitude, which is the amplitude of the swing that causes the feed shaft to reciprocate, based on the feed command; a swing command calculation unit that calculates a swing command for causing the feed shaft to reciprocate based on the swing amplitude and the swing phase corrected by the swing phase correction unit; as well as a command synthesis unit that superimposes the feed command and the swing command to calculate a synthesis command for driving the feed axis, The swing phase correction unit advances the swing phase when the trajectory of the position of the feed axis in the synthesized instruction is on the side of an upward convex peak, and delays the swing phase when the trajectory of the position of the feed axis in the synthesized instruction is on the side of a downward convex trough.

2. The control device for a machine tool according to claim 1, characterized in that: The wobble phase correction section corrects the wobble phase based on the wobble amplitude and the wobble phase before correction.

3. The control device for a machine tool according to claim 1 or 2, characterized in that: The swing phase correction unit calculates an assumed command that is the synthesized command assumed to be the case when the swing phase correction unit does not perform correction based on the swing amplitude, the swing phase before correction, and the feed command. The swing phase correction unit calculates the acceleration of the feed axis in accordance with the assumed command. The wobble phase correction unit determines whether to advance or retard the wobble phase based on the acceleration.

4. The control device for a machine tool according to claim 1 or 2, characterized in that: The swing phase calculation unit calculates the swing phase as a value proportional to time. The wobble phase correcting section adds a correction amount that changes in a sine wave shape with respect to time to the wobble phase calculated by the wobble phase calculating section.

5. The control device for a machine tool according to claim 4, characterized in that: The wobble phase correcting section makes the phase of the correction amount equal to the wobble phase calculated by the wobble phase calculating section.

6. The control device for a machine tool according to any one of claims 1, 2 or 5, characterized in that: The control device of the machine tool further includes a swing amplitude correction unit for correcting the swing amplitude. The swing command calculation section calculates the swing command based on the swing phase corrected by the swing phase correction section and the swing amplitude corrected by the swing amplitude correction section.

7. A method for controlling a machine tool, the method comprising controlling a machine tool having a spindle for rotating a cutting tool and a workpiece relative to each other and a feed axis for moving the cutting tool and the workpiece relative to each other, and controlling the spindle and the feed axis to coordinate operations so as to perform cutting processing on the workpiece using the cutting tool, It is characterized in that The machine tool control method comprises the following steps: a step of calculating a feed command for moving the feed axis relative to the workpiece; a step of calculating a swing phase, which is a phase of swinging that causes the feed shaft to reciprocate, based on the rotation speed of the main shaft; A step of correcting the swing phase; a step of calculating a swing command for causing the feed shaft to reciprocate based on the swing phase corrected in the step of correcting the swing phase; The step of superimposing the feed command and the swing command to calculate a composite command for driving the feed axis; as well as The swing phase is advanced on the side of a crest that is convex upward in the trajectory of the position of the feed axis in the synthesized command, and is delayed on the side of a trough that is convex downward in the trajectory of the position of the feed axis in the synthesized command.

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