Machine tool control device, machining system, program, and machining method

Abstract

A control device (2) for a machine tool (3) controls the machine tool (3), which is provided with: a feed drive unit that causes a tool having three or more cutting edges and a workpiece to move relative to each other; and a main spindle drive unit (21) that rotates the tool. The control device (2) for the machine tool (3) comprises: a command generating unit (11) that generates rotation commands for the main spindle drive unit (21) and movement commands for the feed drive unit; and a command correcting unit (12) that suppresses tool vibrations that occur during machining of the workpiece, by subjecting the movement commands to correction for superimposing, on the movement of the tool relative to the workpiece, vibration movements having an amplitude, frequency, and phase that cause the thickness of a cut-off part to be non-uniform within the cut-off part per cutting edge.

Description

Control device for machine tool, machining system, program, and machining method

[0001] The present disclosure relates to a control device for a machine tool, a machining system, a program, and a machining method.

[0002] In a machine tool that cuts a workpiece by rotating a tool and relatively moving the tool and the workpiece relative to each other, machining accuracy may deteriorate due to the occurrence of chatter vibration. Here, chatter vibration is a general term for vibrations that occur intermittently during cutting.

[0003] Patent Document 1 discloses a machining vibration suppression device that suppresses chatter vibration by applying micro-vibration to the feed operation of a feed drive unit during machining. The machining vibration suppression device of Patent Document 1 receives each piece of information on vibration radius and angular velocity, and superimposes micro-vibration based on a trajectory set based on the vibration radius and angular velocity on the machining trajectory representing the feed operation.

[0004] Japanese Unexamined Patent Publication No. 2013-240837

[0005] The technology disclosed in Patent Document 1 does not consider the phase lag caused by the control of the feed drive unit or the dynamic stiffness of the machine tool. For this reason, there has been a problem that it may be difficult to suppress chatter vibration during machining of a workpiece.

[0006] The present disclosure has been made in view of the above, and an object of the present disclosure is to obtain a control device for a machine tool that can suppress chatter vibration during machining of a workpiece.

[0007] To solve the above-mentioned problems and achieve the objective, the machine tool control device according to the present disclosure is a machine tool control device that controls a machine tool comprising a feed drive unit that moves a tool having three or more cutting edges and a workpiece relative to each other, and a spindle drive unit that rotates the tool. The machine tool control device according to the present disclosure comprises a command generation unit that generates rotation commands for the spindle drive unit and operation commands for the feed drive unit, and a command correction unit that suppresses tool vibrations generated during workpiece machining by superimposing vibrations of amplitude, frequency, and phase that cause uneven thickness of the cut portion within the cut portion by each cutting edge onto the operation of the tool relative to the workpiece.

[0008] The control device for machine tools described herein has the effect of suppressing chatter vibrations during workpiece machining.

[0009] A diagram showing an example configuration of the machining system according to Embodiment 1. A diagram showing an example configuration of the machine tool included in the machining system according to Embodiment 1. A diagram explaining the tools used for machining in the machining system according to Embodiment 1. A first diagram showing the cutting of a workpiece by a machine tool in the machining system according to Embodiment 1. A second diagram showing the cutting of a workpiece by a machine tool in the machining system according to Embodiment 1. A third diagram showing the cutting of a workpiece by a machine tool in the machining system according to Embodiment 1. A first diagram explaining an example of correction by the command correction unit included in the control device of the machining system according to Embodiment 1. A second diagram explaining an example of correction by the command correction unit included in the control device of the machining system according to Embodiment 1. A flowchart showing an example of the operation procedure of the machining system according to Embodiment 1. A diagram showing an example configuration of the machining system according to Embodiment 2. A diagram showing an example configuration of the machining system according to Embodiment 3. A diagram showing an example configuration of the machining system according to Embodiment 4. A diagram showing an example configuration of the control circuit according to Embodiments 1 to 4. A diagram showing an example configuration of the dedicated hardware circuit according to Embodiments 1 to 4.

[0010] The control device, machining system, program, and machining method of the machine tool according to the embodiment will be described in detail below with reference to the drawings.

[0011] Embodiment 1. Figure 1 is a diagram showing an example of the configuration of a machining system 1 according to Embodiment 1. The machining system 1 is a system that performs machining using a machine tool 3. The machining system 1 comprises a control device 2 and a machine tool 3. The control device 2 controls the machine tool 3.

[0012] Figure 2 shows an example of the configuration of a machine tool 3 in the machining system 1 according to Embodiment 1. In Embodiment 1, the machine tool 3 is assumed to be a vertical, orthogonal three-axis cutting machine. The X, Y, and Z axes are three mutually orthogonal axes. In Figure 2, the direction of the arrow representing the X axis is the positive X direction, and the opposite direction of the positive X direction is the negative X direction. The direction of the arrow representing the Y axis is the positive Y direction, and the opposite direction of the positive Y direction is the negative Y direction. The direction of the arrow representing the Z axis is the positive Z direction, and the opposite direction of the positive Z direction is the negative Z direction.

[0013] The machine tool 3 comprises a bed 30 which is the base of the machine tool 3, a column 31 fixed to the bed 30, a table 32 on which the workpiece 35 is fixed, a head 33 supported by the column 31, and a spindle 34 attached to the head 33. The tool 36 is attached to the spindle 34. The tool 36 is used to machine the workpiece 35.

[0014] The machine tool 3 comprises a spindle drive unit 21, an X-axis drive unit 22 which is a first feed drive unit, a Y-axis drive unit 23 which is a second feed drive unit, and a Z-axis drive unit 24 which is a third feed drive unit. The spindle drive unit 21 rotates a tool 36 attached to the spindle 34. The tool 36 has three or more cutting edges. The tool 36 rotates due to the driving force of the motor of the spindle drive unit 21. The direction of the axis of rotation, which is the centerline of the rotational motion of the tool 36, is the Z-axis direction. Note that the spindle drive unit 21 is not shown in Figure 2.

[0015] The X-axis drive unit 22, the Y-axis drive unit 23, and the Z-axis drive unit 24 are feed drive units that impart linear motion to the tool 36 or workpiece 35. The machine tool 3 moves the tool 36 and the workpiece 35 relative to each other using the X-axis drive unit 22, the Y-axis drive unit 23, and the Z-axis drive unit 24. Figure 1 shows the spindle drive unit 21, the X-axis drive unit 22, the Y-axis drive unit 23, and the Z-axis drive unit 24, which are components of the machine tool 3. The machine tool 3 moves the head 33 using the X-axis drive unit 22 and the Z-axis drive unit 24, and moves the table 32 using the Y-axis drive unit 23, thereby moving the workpiece 35 and the tool 36 relative to each other.

[0016] The X-axis drive unit 22 includes a ball screw, a motor that rotates the ball screw, and a mechanism that converts the rotational motion of the ball screw into linear motion in the X-axis direction. The X-axis drive unit 22 moves the head 33 in the X-axis direction. The X-axis drive unit 22 is a feed drive unit that moves the tool 36 and the workpiece 35 relative to each other in the X-axis direction, which is a first direction perpendicular to the rotation axis of the tool 36.

[0017] The Y-axis drive unit 23 includes a ball screw, a motor that rotates the ball screw, and a mechanism that converts the rotational motion of the ball screw into linear motion in the Y-axis direction. The Y-axis drive unit 23 moves the table 32 in the Y-axis direction. The Y-axis drive unit 23 is a feed drive unit that moves the tool 36 and the workpiece 35 relative to each other in the Y-axis direction, which is a second direction that is orthogonal to the rotation axis of the tool 36 and the first direction.

[0018] The Z-axis drive unit 24 includes a ball screw, a motor that rotates the ball screw, and a mechanism that converts the rotational motion of the ball screw into linear motion in the Z-axis direction. The Z-axis drive unit 24 moves the head 33 in the Z-axis direction. The Z-axis drive unit 24 is a feed drive unit that moves the tool 36 and the workpiece 35 relative to each other in the Z-axis direction, which is the direction of the rotation axis of the tool 36.

[0019] The control device 2 shown in Figure 1 comprises a command generation unit 11 and a command correction unit 12. The command generation unit 11 generates rotation commands for the spindle drive unit 21 and operation commands for each of the feed drive units, namely the X-axis drive unit 22, the Y-axis drive unit 23, and the Z-axis drive unit 24. The command generation unit 11 generates rotation commands for the spindle drive unit 21 and operation commands for each of the X-axis drive unit 22, the Y-axis drive unit 23, and the Z-axis drive unit 24 according to the machining program, which is an NC (Numerical Control) program.

[0020] The control device 2 outputs the rotation command generated by the command generation unit 11 to the spindle drive unit 21. The control device 2 outputs the motion command for linear motion in the Z-axis direction, generated by the command generation unit 11, to the Z-axis drive unit 24. The spindle drive unit 21 rotates the tool 36 according to the rotation command input to the spindle drive unit 21. The Z-axis drive unit 24 moves the head 33 in the Z-axis direction according to the motion command input to the Z-axis drive unit 24.

[0021] The command generation unit 11 outputs an operation command for linear motion in the X-axis direction and an operation command for linear motion in the Y-axis direction to the command correction unit 12. The command correction unit 12 corrects the operation command for linear motion in the X-axis direction, which is the operation command for the X-axis drive unit 22, and the operation command for linear motion in the Y-axis direction, which is the operation command for the Y-axis drive unit 23. The command correction unit 12 corrects the operation command by superimposing vibrational motion of amplitude, frequency, and phase that causes uneven thickness in the cut portion within the cut portion per cutting edge of the tool 36 onto the operation of the tool 36 on the workpiece 35, thereby suppressing vibration of the tool 36 that occurs during the machining of the workpiece 35.

[0022] The control device 2 outputs an operation command for linear motion in the X-axis direction, corrected by the command correction unit 12, to the X-axis drive unit 22. The control device 2 outputs an operation command for linear motion in the Y-axis direction, corrected by the command correction unit 12, to the Y-axis drive unit 23. The X-axis drive unit 22 moves the head 33 in the X-axis direction according to the operation command input to the X-axis drive unit 22. The Y-axis drive unit 23 moves the table 32 in the Y-axis direction according to the operation command input to the Y-axis drive unit 23.

[0023] In the above configuration, the command correction unit 12 corrects the operation command for the X-axis drive unit 22 and the operation command for the Y-axis drive unit 23. The command correction unit 12 may also correct only one of the operation commands from the command generation unit 11, either the operation command for the X-axis drive unit 22 or the operation command for the Y-axis drive unit 23. The control device 2 may also output only one of the operation commands for the X-axis drive unit 22 corrected by the command correction unit 12, or the operation command for the Y-axis drive unit 23 corrected by the command correction unit 12.

[0024] In the above description, machine tool 3 is assumed to have a three-axis feed drive unit. However, machine tool 3 is not limited to having a three-axis feed drive unit. Machine tool 3 may also be a lathe or other machine tool having a two-axis feed drive unit.

[0025] Next, the cutting of the workpiece 35 using the tool 36 will be described. Figure 3 is a diagram illustrating the tool 36 used for machining in the machining system 1 according to Embodiment 1. Figure 3 shows the XY cross-section of the tool 36, that is, the cross-section perpendicular to the central axis of the tool 36. Figure 3 also schematically shows the XY cross-section of the workpiece 35 when it is being cut by the tool 36.

[0026] Here, the machine tool 3 processes the workpiece 35 using a tool 36 having four cutting edges. The tool 36 has a first cutting edge G1, a second cutting edge G2, a third cutting edge G3, and a fourth cutting edge G4. The geometric center Oa represents the position of the central axis of the tool 36 in the above cross-section. The rotational direction K1 is the direction in which the tool 36 rotates when processing the workpiece 35.

[0027] The machine tool 3 can perform cutting operations with the rotation center of the tool 36 coinciding with the geometric center Oa, and cutting operations with the rotation center of the tool 36 offset from the geometric center Oa. Here, the state in which the rotation center of the tool 36 is offset from the geometric center Oa is called tool eccentricity. In tool eccentricity, the rotation center of the tool 36 is set at a position offset from the geometric center Oa in the XY cross-section of the tool 36. The rotation center Ob shown in Figure 3 is an example of a rotation center set at a position offset from the geometric center Oa. The rotation direction K2 is the direction in which the geometric center Oa rotates when the tool 36 rotates around the rotation center Ob.

[0028] Figure 4 is the first diagram showing how a workpiece 35 is cut by a machine tool 3 in the machining system 1 according to Embodiment 1. In Figure 4, the cutting process is shown with the rotation center Ob of the tool 36 aligned with the geometric center Oa.

[0029] Figure 4 shows the process in which the first cutting edge G1, second cutting edge G2, third cutting edge G3, and fourth cutting edge G4 sequentially contact the workpiece 35, until the first cutting edge G1 contacts the workpiece 35 again. In other words, Figure 4 shows the tool 36 completing one rotation.

[0030] The feed direction D is the direction in which the tool 36 moves relative to the workpiece 35. In Figure 4, the feed direction D is the positive X direction. The trajectory qa is the trajectory of the geometric center Oa as the tool 36 rotates and moves in the feed direction D. In Figure 4, the trajectory qa is a straight line parallel to the feed direction D. The trajectory qb is the trajectory of the rotation center Ob as the tool 36 rotates and moves in the feed direction D. In Figure 4, the trajectory qa coincides with the trajectory qb.

[0031] In Figure 4, the distance between the machined surface of the workpiece 35 and the geometric center Oa remains constant during one rotation of the tool 36. In the cutting process shown in Figure 4, the first cutting edge G1, the second cutting edge G2, the third cutting edge G3, and the fourth cutting edge G4 all sequentially contact the workpiece 35. In the cutting process shown in Figure 4, cutting is performed by each of the first cutting edge G1, the second cutting edge G2, the third cutting edge G3, and the fourth cutting edge G4.

[0032] Figure 5 is a second diagram showing the cutting of a workpiece 35 by a machine tool 3 in the machining system 1 according to Embodiment 1. Figure 5 shows the cutting process with tool eccentricity. In Figure 5, the rotation center Ob is set at a position offset from the geometric center Oa toward the part of the surface of the tool 36 where the first cutting edge G1 is formed. Figure 5 shows the tool 36 completing one rotation.

[0033] In Figure 5, the feed direction D is in the positive X direction. In Figure 5, the trajectory qb is a straight line parallel to the feed direction D. In Figure 5, the geometric center Oa periodically changes between a position shifted in the positive Y direction relative to the trajectory qb and a position shifted in the negative Y direction relative to the trajectory qb during one rotation of the tool 36. In Figure 5, the trajectory qa is a curve with a waveform that periodically changes in the positive Y direction and the negative Y direction around the straight line that is the trajectory qb.

[0034] In Figure 5, the distance between the machined surface of the workpiece 35 and the geometric center Oa changes during one rotation of the tool 36. As shown in Figure 5, when the distance between the machined surface and the geometric center Oa is greater than the distance between the machined surface and the trajectory qb, the first cutting edge G1 and the second cutting edge G2 pass through a position shifted in the positive Y direction from the machined surface. Therefore, in the cutting process shown in Figure 5, cutting by the first cutting edge G1 and cutting by the second cutting edge G2 are not performed. Also, as shown in Figure 5, when the distance between the machined surface and the geometric center Oa is narrower than the distance between the machined surface and the trajectory qb, the third cutting edge G3 and the fourth cutting edge G4 come into contact with the workpiece 35. Therefore, in the cutting process shown in Figure 5, cutting by the third cutting edge G3 and cutting by the fourth cutting edge G4 are performed.

[0035] The machining system 1 performs cutting operations involving tool eccentricity through tool eccentricity control by the control device 2. Tool eccentricity control refers to a control that shifts the geometric center Oa relative to the rotation center Ob by moving the workpiece 35 and the tool 36 relative to each other using the feed drive unit. Specifically, the command generation unit 11 generates operation commands for the X-axis drive unit 22 and the Y-axis drive unit 23, respectively, to impart rotational motion around the rotation center Ob at a specific frequency to the geometric center Oa.

[0036] In Figure 5, the period for rotating the geometric center Oa around the rotation center Ob is the same as the period for rotating the tool 36 by the spindle drive unit 21. The control device 2 performs the above-described control for the X-axis drive unit 22 and the Y-axis drive unit 23 as tool eccentricity control, thereby realizing cutting operations with tool eccentricity as shown in Figure 5.

[0037] Figure 6 is a third diagram showing the cutting of a workpiece 35 by a machine tool 3 in the machining system 1 according to Embodiment 1. Figure 6 shows the cutting process with tool eccentricity. The rotation center Ob shown in Figure 6 is in a different position from the rotation center Ob shown in Figure 5. Figure 6 shows the tool 36 making one rotation. In Figure 6, the feed direction D is in the positive X direction. In Figure 6, the trajectory qa is a curve with a waveform that changes periodically in the positive Y direction and the negative Y direction around the straight line that is the trajectory qb.

[0038] In Figure 6, the distance between the machined surface of the workpiece 35 and the geometric center Oa changes during one rotation of the tool 36. As shown in Figure 6, when the distance between the machined surface and the geometric center Oa is greater than the distance between the machined surface and the trajectory qb, the second cutting edge G2 and the fourth cutting edge G4 pass through a position shifted in the positive Y direction from the machined surface. Therefore, in the cutting process shown in Figure 6, cutting by the second cutting edge G2 and cutting by the fourth cutting edge G4 does not occur. Also, as shown in Figure 6, when the distance between the machined surface and the geometric center Oa is narrower than the distance between the machined surface and the trajectory qb, the first cutting edge G1 and the third cutting edge G3 come into contact with the workpiece 35. Therefore, in the cutting process shown in Figure 6, cutting by the first cutting edge G1 and cutting by the third cutting edge G3 occur.

[0039] In Figure 6, the period for rotating the geometric center Oa around the rotation center Ob is equal to twice the period for rotating the tool 36 by the spindle drive unit 21. The control device 2 performs tool eccentricity control on the X-axis drive unit 22 and the Y-axis drive unit 23, respectively, as shown in Figure 5, thereby realizing cutting operations with tool eccentricity as shown in Figure 6.

[0040] In Figures 5 and 6, tool eccentricity control is used to include vibrations in the Y-axis direction, which is perpendicular to the feed direction D, in the movement of the tool 36 relative to the workpiece 35. In practice, the machining system 1 uses tool eccentricity control to include vibrations in the X-axis direction, which is the same as the feed direction D, in the movement of the tool 36 relative to the workpiece 35. Alternatively, the machining system 1 may use tool eccentricity control to include vibrations that are a combination of vibrations in the X-axis direction and vibrations in the Y-axis direction in the movement of the tool 36 relative to the workpiece 35.

[0041] Next, the correction of the operation command by the command correction unit 12 will be explained. The command correction unit 12 applies a correction to the operation command for linear motion in the X-axis direction, superimposing vibration motion onto the movement of the tool 36 on the workpiece 35. In other words, the command correction unit 12 corrects the operation command to the X-axis drive unit 22.

[0042] Alternatively, the command correction unit 12 may perform a correction to superimpose vibrational motion on the operation of the tool 36 relative to the workpiece 35, for both the operation command for linear motion in the X-axis direction and the operation command for linear motion in the Y-axis direction. That is, the command correction unit 12 may correct the operation command for the X-axis drive unit 22 and the operation command for the Y-axis drive unit 23.

[0043] The amplitude, frequency, and phase information of the vibration motion superimposed by the correction of the operation command in the command correction unit 12 are input to the command correction unit 12 from outside the control device 2. As one example, the amplitude, frequency, and phase are calculated by a device outside the control device 2, and this information is input to the command correction unit 12 from that device. The amplitude, frequency, and phase information may also be input to the command correction unit 12 by the user of the machining system 1. The amplitude, frequency, and phase information may also be described in the machining program input to the control device 2. The command correction unit 12 may also acquire the amplitude, frequency, and phase information from the machining program.

[0044] The command correction unit 12 performs correction to superimpose a vibrating motion with amplitude, frequency, and phase that makes the thickness of the cut portion non-uniform within the cut portion per cutting edge of the tool 36 on the motion of the tool 36 relative to the workpiece 35. Through this correction, the command correction unit 12 suppresses chatter vibration, which is self-excited vibration that occurs intermittently during machining of the workpiece 35.

[0045] In order to make the thickness of the cut portion non-uniform within the cut portion per cutting edge, it is desirable that the correction amount of the position of the tool 36 by the aforementioned vibrating motion reaches a maximum value or a minimum value at the moment when the cutting edge comes into contact with the workpiece 35. In order to superimpose such a vibrating motion, it is desirable to correct the motion command in consideration of the phase lag caused by the control of the feed drive unit or the dynamic stiffness of the machine tool 3. Here, the phase lag refers to the phase lag in the actual vibrating motion of the tool 36 relative to the motion command.

[0046] The command correction unit 12 superimposes a vibrating motion with preset amplitude, frequency, and phase on the motion of the tool 36 relative to the workpiece 35. By applying the vibrating motion having a phase set according to the phase lag to the motion of the tool 36 relative to the workpiece 35, the correction amount of the position of the tool 36 by the vibrating motion can reach the maximum value or the minimum value at the moment when the cutting edge comes into contact with the workpiece 35. When the correction amount reaches the maximum value or the minimum value at the moment when the cutting edge comes into contact with the workpiece 35, it is possible to provide a difference in thickness within the cut portion. Accordingly, the control device 2 makes the thickness of the cut portion non-uniform within the cut portion per cutting edge.

[0047] The control device 2 reduces the cutting process gain, which is the cutting force increment per unit vibration displacement, by making the thickness of the cut portion non-uniform. Since increases and decreases in the cutting process gain affect increases and decreases in chatter vibration, the control device 2 can suppress chatter vibration by reducing the cutting process gain. Accordingly, the control device 2 can suppress chatter vibration during machining of the workpiece 35.

[0048] FIG. 7 is a first diagram for explaining an example of correction by the command correction unit 12 included in the control device 2 of the machining system 1 according to the first embodiment. FIG. 8 is a second diagram for explaining an example of correction by the command correction unit 12 included in the control device 2 of the machining system 1 according to the first embodiment.

[0049] FIG. 7 shows an XY cross-section of the tool 36, that is, a cross-section perpendicular to the central axis of the tool 36. FIG. 7 also schematically shows an XY cross-section of the workpiece 35 when being cut by the tool 36. FIG. 7 shows a state where the tool 36 makes one rotation. In FIG. 7, the feed direction D is the positive X direction.

[0050] Here, an example will be described in which, when the rotation center of the tool 36 is aligned with the geometric center Oa, an operation command to the X-axis drive unit 22 is corrected by the command correction unit 12. The vibration direction S is the direction of the vibration operation to be superimposed on the operation of the tool 36 relative to the workpiece 35. In FIG. 7, the vibration direction S is the same as the X-axis direction.

[0051] FIG. 8 shows a first graph representing the displacement amount of the tool 36 during one rotation of the tool 36 as shown in FIG. 7, and a second graph representing the cutting force exerted by each cutting edge of the tool 36 during one rotation of the tool 36 as shown in FIG. 7. Here, the displacement amount of the tool 36 refers to the displacement amount of the tool 36 caused by the vibration operation when the center of the vibration operation is used as a reference. In the first graph, the vertical axis represents the displacement amount and the horizontal axis represents time. A displacement amount when the tool 36 is displaced in the positive X direction relative to the center of the vibration operation is defined as a positive displacement amount. A displacement amount when the tool 36 is displaced in the negative X direction relative to the center of the vibration operation is defined as a negative displacement amount. In the second graph, the vertical axis represents cutting force and the horizontal axis represents time.

[0052] Cutting of the workpiece 35 by the first cutting edge G1 is performed when the absolute value of the negative displacement amount is increasing. The feed amount d1 shown in FIG. 7 is the feed amount per cutting edge for the first cutting edge G1. The cutting force F1 exerted by the first cutting edge G1 changes as shown in the second graph of FIG. 8.

[0053] After cutting by the first cutting edge G1, the absolute value of the negative displacement is maximized when the cutting edge of the second cutting edge G2 reaches its foremost position in the positive X direction. In the example shown in Figure 7, the second cutting edge G2 does not contact the workpiece 35. Therefore, cutting by the second cutting edge G2 does not occur. t1 in Figure 8 represents the time when the absolute value of the negative displacement is maximized. In Figure 7, the white arrow pointing in the negative X direction indicates that the absolute value of the negative displacement is maximized.

[0054] After t1, the absolute value of the negative displacement decreases, and the displacement becomes zero. Subsequently, the positive displacement increases. When the positive displacement is increasing, the workpiece 35 is cut by the third cutting edge G3. The feed rate d3 shown in Figure 7 is the feed rate per cutting edge for the third cutting edge G3. The cutting force F3 by the third cutting edge G3 changes as shown in the second graph of Figure 8.

[0055] The positive displacement is maximized when the cutting edge of the fourth cutting edge G4 reaches its foremost position in the positive X direction after cutting by the third cutting edge G3. The feed rate d4 shown in Figure 7 is the feed rate per cutting edge for the fourth cutting edge G4. The cutting force F4 by the fourth cutting edge G4 changes as shown in the second graph of Figure 8. t2 shown in Figure 8 represents the time when the positive displacement is maximized. In Figure 7, the white arrow pointing in the positive X direction indicates that the positive displacement is at its maximum.

[0056] After t2, the positive displacement decreases and becomes zero. Subsequently, the absolute value of the negative displacement increases, and cutting of the workpiece 35 by the first cutting edge G1 is performed again.

[0057] In the examples shown in Figures 7 and 8, the frequency of the vibration is the same as the frequency at which the spindle drive unit 21 rotates the tool 36. Therefore, of the four cutting edges of the tool 36, the cutting edge that produces the thinnest cut is the same cutting edge for each rotation of the tool 36. Also, of the four cutting edges of the tool 36, the cutting edge that produces the thickest cut is the same cutting edge for each rotation of the tool 36.

[0058] In the examples shown in Figures 7 and 8, the cutting edges that produce the thinnest cut portion in each rotation of the tool 36 are the first cutting edge G1 and the third cutting edge G3. The cutting edge that produces the thickest cut portion in each rotation of the tool 36 is the fourth cutting edge G4. The cutting edge that is not used for cutting in each rotation of the tool 36 is the second cutting edge G2.

[0059] In this way, the frequency of the vibration operation is determined so that the cutting edge that produces the thinnest cut portion per cutting edge is the same cutting edge for each rotation of the tool 36. As a result, the control device 2 can improve the chatter vibration suppression effect compared to the case where the cutting edge that produces the thinnest cut portion per cutting edge is not the same cutting edge for each rotation of the tool 36.

[0060] When the cutting edge that produces the thinnest cut portion per blade is the same cutting edge for each rotation of the tool 36, the command correction unit 12 may change the frequency of the vibration operation depending on the situation. For example, the command correction unit 12 changes the frequency of the vibration operation when the rotational speed of the tool 36 is changed. In this case, the command correction unit 12 changes the frequency of the vibration operation in proportion to the rotational speed of the tool 36. This allows the control device 2 to continue operating in such a way that the cutting edge that produces the thinnest cut portion per blade is the same cutting edge for each rotation of the tool 36. The rotational speed is defined as the number of rotations per unit time.

[0061] In Embodiment 1, the frequency of the vibration operation is not limited to a frequency determined such that the cutting edge that produces the thinnest cut portion per cutting edge is the same cutting edge for each rotation of the tool 36. In Embodiment 1, the frequency of the vibration operation may be determined such that the cutting edge that produces the thinnest cut portion per cutting edge among the three or more cutting edges of the tool 36 is not the same cutting edge for two consecutive rotations of the tool 36.

[0062] In this case, the cutting edge that produces the thickest cut portion per cutting edge is sequentially switched with each rotation of the tool 36. Therefore, it is possible to prevent the cutting force from concentrating on a specific cutting edge of the tool 36 while the tool 36 is repeatedly rotated. As a result, uneven wear on a specific cutting edge is prevented, and the lifespan of the tool 36 can be extended.

[0063] When the cutting edge that produces the thinnest cut portion per cutting edge is not the same cutting edge in two consecutive rotations of the tool 36, the command correction unit 12 may change the frequency of the vibration operation depending on the situation. For example, the command correction unit 12 changes the frequency of the vibration operation when the rotational speed of the tool 36 is changed. In this case, the command correction unit 12 changes the frequency of the vibration operation in proportion to the rotational speed of the tool 36. As a result, the control device 2 can continue to operate in such a way that the cutting edge that produces the thinnest cut portion per cutting edge is not the same cutting edge in two consecutive rotations of the tool 36.

[0064] In the above, the vibration direction S was assumed to be the same as the X-axis direction, which includes the feed direction D. The vibration direction S may also be the same as the Y-axis direction. Alternatively, the vibration direction S may be an oblique direction between the X-axis and Y-axis directions.

[0065] Next, the operation procedure of the machining system 1 will be described. Figure 9 is a flowchart showing an example of the operation procedure of the machining system 1 according to Embodiment 1. Here, the feed direction D is assumed to be the positive X direction. The command correction unit 12 corrects the operation command for linear motion in the X-axis direction and the operation command for linear motion in the Y-axis direction, respectively.

[0066] In step S1, the control device 2 generates a rotation command and an operation command in the command generation unit 11. The command generation unit 11 generates a rotation command for the spindle drive unit 21 and operation commands for the X-axis drive unit 22, the Y-axis drive unit 23, and the Z-axis drive unit 24, respectively. The command generation unit 11 outputs the operation command for the X-axis drive unit 22 and the operation command for the Y-axis drive unit 23 to the command correction unit 12.

[0067] In step S2, the control device 2, in the command correction unit 12, performs a correction on the operation command to superimpose a vibration operation on the operation of the tool 36. The command correction unit 12 corrects the operation command for the X-axis drive unit 22 and the operation command for the Y-axis drive unit 23 that were generated in step S1.

[0068] The control device 2 outputs the rotation command generated in step S1 to the spindle drive unit 21. The control device 2 outputs the operation command for the Z-axis drive unit 24 generated in step S1 to the Z-axis drive unit 24. The control device 2 outputs the operation command for the X-axis drive unit 22, which has been corrected in step S2, to the X-axis drive unit 22. The control device 2 outputs the operation command for the Y-axis drive unit 23, which has been corrected in step S2, to the Y-axis drive unit 23.

[0069] In step S3, the machine tool 3 cuts the workpiece 35 by rotating the tool 36 according to the rotation command and moving the table 32 and head 33 according to the motion command. The spindle drive unit 21 rotates the tool 36 by driving the spindle 34 according to the rotation command. The X-axis drive unit 22 moves the head 33 in the X-axis direction by driving according to the motion command. The Y-axis drive unit 23 moves the table 32 in the Y-axis direction by driving according to the motion command. The Z-axis drive unit 24 moves the head 33 in the Z-axis direction by driving according to the motion command.

[0070] In step S2 described above, the command correction unit 12 performs a correction on the operation command by superimposing vibrational motion of amplitude, frequency, and phase on each of the three or more cutting edges of the tool 36, causing the cutting thickness by the cutting edge to become uneven during one rotation of the tool 36. As a result, the command correction unit 12 suppresses vibrations of the tool 36 that occur during the machining of the workpiece 35.

[0071] According to Embodiment 1, the control device 2 includes a command generation unit 11 that generates rotation commands for the spindle drive unit 21 and operation commands for the feed drive unit, and a command correction unit 12 that suppresses vibrations of the tool 36 generated during machining of the workpiece 35 by superimposing vibrations of amplitude, frequency, and phase on the operation commands to make the thickness of the cut portion uneven within the cut portion per cutting edge. The control device 2 reduces the cutting process gain by superimposing vibrations on the operation of the tool 36 on the workpiece 35 so that the thickness of the cut portion is not uniform within the cut portion per cutting edge. By reducing the cutting process gain, the control device 2 can suppress chatter vibrations. As a result, the control device 2 has the effect of suppressing chatter vibrations during machining of the workpiece 35.

[0072] The command generation unit 11 generates an operation command for a first feed drive unit that moves the tool 36 and the workpiece 35 relative to each other in a first direction, and an operation command for a second feed drive unit that moves the tool 36 and the workpiece 35 relative to each other in a second direction. The command correction unit 12 may correct the operation command for the first feed drive unit and the operation command for the second feed drive unit. As a result, the control device 2 can suppress chatter vibration when operating the tool 36 in two directions perpendicular to the rotation axis.

[0073] The frequency of the vibration operation may be determined such that the cutting edge that produces the thinnest cut portion per cutting edge is the same cutting edge for each rotation of the tool 36. This allows the control device 2 to improve its chatter vibration suppression effect.

[0074] The frequency of the vibration operation may be determined such that the cutting edge that produces the thinnest cut portion among three or more cutting edges is not the same cutting edge during two consecutive rotations of the tool 36. This prevents uneven wear on a particular cutting edge and extends the lifespan of the tool 36.

[0075] The command correction unit 12 may change the frequency of vibration when the frequency at which the spindle drive unit 21 rotates the tool 36 is changed. This allows the control device 2 to continue operating such that the cutting edge that produces the thinnest cut portion per cutting edge is the same cutting edge for each rotation of the tool 36. Alternatively, the control device 2 may continue operating such that the cutting edge that produces the thinnest cut portion per cutting edge is not the same cutting edge for two consecutive rotations of the tool 36.

[0076] Embodiment 2. Figure 10 shows an example of the configuration of the machining system 1A according to Embodiment 2. The machining system 1A according to Embodiment 2 detects the vibration of the tool 36 that occurs during machining of the workpiece 35, determines the frequency of the vibration, and adjusts the rotational speed of the tool 36. In Embodiment 2, the same reference numerals are used for the same components as in Embodiment 1, and the configuration that differs from Embodiment 1 will be mainly described.

[0077] The machining system 1A is a system that performs machining using a machine tool 3A. The machining system 1A comprises a control device 2A and a machine tool 3A. The control device 2A controls the machine tool 3A. The control device 2A comprises a command generation unit 11, a command correction unit 12, and a sensor processing unit 13. The machine tool 3A has the same configuration as the machine tool 3 shown in Figure 1, and also includes a sensor 25.

[0078] Sensor 25 is an acceleration sensor, a displacement sensor, or a cutting dynamometer. Sensor 25 detects chatter vibrations of the tool 36 that occur during machining of the workpiece 35. Sensor 25 outputs a signal showing the waveform of the detected vibration to the control device 2A. The signal from sensor 25 is input to the sensor processing unit 13. Based on the result of detecting chatter vibrations by sensor 25, the sensor processing unit 13 calculates the frequency of the chatter vibration.

[0079] The sensor processing unit 13 detects the vibration frequency by frequency analysis of the signal from the sensor 25. The sensor processing unit 13 performs frequency analysis using, for example, the Fast Fourier Transform. Other frequency analysis methods may be used by the sensor processing unit 13.

[0080] Furthermore, the sensor processing unit 13 is not limited to calculating the frequency of chatter vibration based on the signal from the sensor 25. The sensor processing unit 13 may also calculate the frequency of chatter vibration based on the signal output by the rotary encoder provided on the motor of the feed drive unit, or the signal output by the linear encoder provided on the feed drive unit. The sensor processing unit 13 may also calculate the frequency of chatter vibration based on the current command sent to the motor of the feed drive unit.

[0081] Here, let S1 be the target value for the rotational speed of the tool 36, fc be the frequency calculated by the sensor processing unit 13, n be the number of cutting edges on the tool 36, and m be an arbitrary natural number. The sensor processing unit 13 generates an adjustment command to adjust the rotational speed of the tool 36 to a target value that satisfies the following equation (1).

[0082]

[0083] The sensor processing unit 13 outputs the generated adjustment command to the command generation unit 11. The command generation unit 11 adjusts the rotation speed indicated in the rotation command according to the adjustment command from the sensor processing unit 13. The command generation unit 11 outputs a rotation command that has been adjusted according to the adjustment command.

[0084] The control device 2A determines a target value for the rotational speed of the tool 36 using the above formula (1), which is a calculation formula that incorporates the frequency of the generated chatter vibration, and adjusts the rotational speed of the tool 36 to the target value. The control device 2A can suppress chatter vibration by superimposing multiple vibrations that have opposite phases to each other. The control device 2A can obtain the effect of suppressing chatter vibration by reducing the cutting process gain as described in Embodiment 1, and the effect of suppressing chatter vibration by superimposing multiple vibrations that have opposite phases to each other.

[0085] According to Embodiment 2, the sensor processing unit 13 outputs an adjustment command to the command generation unit 11 for adjusting the rotational speed of the tool 36 to a target value that satisfies the above equation (1), and the command generation unit 11 outputs a rotation command that has been adjusted according to the adjustment command. As a result, the control device 2A can further suppress chatter vibration.

[0086] Embodiment 3. Figure 11 shows an example of the configuration of the machining system 1B according to Embodiment 3. In the machining system 1B according to Embodiment 3, if the vibration of the tool 36 is not suppressed after adjusting the rotational speed of the tool 36, the rotational speed of the tool 36 is adjusted again. In Embodiment 3, the same reference numerals are used for components that are the same as those in Embodiment 1 or 2, and the configuration that differs from Embodiment 1 or 2 will be mainly described.

[0087] The machining system 1B is a system that performs machining using a machine tool 3B. The machining system 1B comprises a control device 2B and a machine tool 3B. The control device 2B controls the machine tool 3B. The control device 2B comprises a command generation unit 11, a command correction unit 12, a sensor processing unit 13, and a vibration determination unit 14. The machine tool 3B has the same configuration as the machine tool 3A shown in Figure 10.

[0088] The sensor 25 detects chatter vibration of the tool 36 and outputs a signal showing the waveform of the detected vibration to the control device 2B. The signal from the sensor 25 is input to the sensor processing unit 13 and the vibration determination unit 14, respectively. The vibration determination unit 14 determines whether or not the chatter vibration of the tool 36 has been suppressed by adjusting the rotational speed of the tool 36 in accordance with the adjustment command in the command generation unit 11.

[0089] The vibration determination unit 14 determines that chatter vibration has been suppressed, for example, when the amplitude of the vibration decreases due to adjustment of the rotational speed of the tool 36. If the vibration determination unit 14 determines that chatter vibration has not been suppressed because the amplitude of the vibration has not decreased, it instructs the sensor processing unit 13 to recalculate the target value for the rotational speed of the tool 36.

[0090] The sensor processing unit 13 recalculates the target value for the rotational speed of the tool 36 according to instructions from the vibration determination unit 14. The sensor processing unit 13 recalculates the target value by substituting a different value for the natural number m in equation (1) than the value used when adjusting the rotational speed last time. In this way, the sensor processing unit 13 recalculates the target value by changing the natural number substituted into equation (1) above if it is determined that the vibration of the tool 36 is not suppressed. The sensor processing unit 13 outputs an adjustment command to the command generation unit 11 to adjust the rotational speed of the tool 36 to the recalculated target value.

[0091] The command generation unit 11 adjusts the rotation speed indicated in the rotation command according to the adjustment command from the sensor processing unit 13. The command generation unit 11 outputs a rotation command that has been adjusted according to the adjustment command. Subsequently, the recalculation of the target value in the sensor processing unit 13 and the adjustment of the rotation speed in the command generation unit 11 are repeated until the vibration determination unit 14 determines that chatter vibration has been suppressed. In this way, the control device 2B can suppress chatter vibration.

[0092] According to Embodiment 3, the vibration determination unit 14 determines whether or not the vibration of the tool 36 has been suppressed by adjusting the rotational speed of the tool 36 in accordance with the adjustment command. If the sensor processing unit 13 determines that the vibration of the tool 36 has not been suppressed, it changes the natural number in equation (1) above to recalculate the target value of the rotational speed and outputs an adjustment command to the command generation unit 11 to adjust the rotational speed of the tool 36 to the recalculated target value. As a result, the control device 2B can further suppress chatter vibration.

[0093] Embodiment 4. Figure 12 shows an example of the configuration of the processing system 1C according to Embodiment 4. The processing system 1C according to Embodiment 4 changes at least one of the amplitude and phase of the vibration operation while detecting the thickness of the portion to be cut by the cutting edge of the tool 36. In Embodiment 4, the same reference numerals are used for the same components as in Embodiments 1 to 3, and the configuration that differs from Embodiments 1 to 3 will be mainly described.

[0094] The machining system 1C is a system that performs machining using a machine tool 3C. The machining system 1C comprises a control device 2C and a machine tool 3C. The control device 2C controls the machine tool 3C. The control device 2C comprises a command generation unit 11, a command correction unit 12, and a cutting thickness detection unit 15. The machine tool 3C has the same configuration as the machine tool 3 shown in Figure 1.

[0095] The cutting thickness detection unit 15 detects the thickness of the cutting portion per cutting blade. The cutting thickness detection unit 15 outputs information indicating the detected thickness to the command correction unit 12. The command correction unit 12 modifies at least one of the amplitude and phase of the vibration operation according to the thickness detected by the cutting thickness detection unit 15. The command correction unit 12 performs a correction on the operation command, superimposing the vibration operation with modified amplitude and phase onto the operation of the tool 36 on the workpiece 35.

[0096] Here, assume that the workpiece 35 is being cut by all three or more cutting edges of the tool 36. For example, the command correction unit 12 modifies at least one of the amplitude and phase according to the detected thickness so that the thickness of the portion cut by at least one of the three or more cutting edges of the tool 36 approaches zero. The command correction unit 12 modifies at least one of the amplitude and phase until cutting is no longer performed by at least one of the three or more cutting edges of the tool 36.

[0097] If the amplitude of the vibration motion superimposed on the movement of the tool 36 relative to the workpiece 35 is insufficient, or if the phase difference, which is the difference between the phase of the spindle 34 and the phase of the vibration motion, is inappropriate, the change in thickness of the cut portion per cutting edge may be small even when vibration motion is superimposed on the movement of the tool 36 relative to the workpiece 35. The smaller the change in thickness of the cut portion per cutting edge, the smaller the effect of suppressing chatter vibration by reducing the cutting process gain.

[0098] The control device 2C can increase the variation in thickness of the cut portion per cutting blade by detecting the thickness of the cut portion with the cutting thickness detection unit 15 and changing at least one of the amplitude and phase of the vibration operation. This improves the effect of suppressing chatter vibration.

[0099] According to Embodiment 4, the command correction unit 12 modifies at least one of the amplitude and phase of the vibration operation according to the thickness detected by the cutting thickness detection unit 15. This allows the control device 2C to further suppress chatter vibrations.

[0100] Next, the hardware configuration for realizing the control devices 2, 2A, 2B, and 2C according to Embodiments 1 to 4 will be described. The control devices 2, 2A, 2B, and 2C are realized by processing circuits. The processing circuit may be a circuit in which a processor executes software, or it may be a dedicated circuit.

[0101] When the processing circuit is implemented by software, the processing circuit is, for example, the control circuit 50 shown in Figure 13. Figure 13 is a diagram showing an example configuration of the control circuit 50 according to Embodiments 1 to 4. The control circuit 50 includes an input unit 51, a processor 52, a memory 53, and an output unit 54. The input unit 51 is an interface circuit that receives data input from outside the control circuit 50 and provides it to the processor 52. The output unit 54 is an interface circuit that sends data from the processor 52 or the memory 53 to the outside of the control circuit 50.

[0102] The control devices 2, 2A, 2B, and 2C are implemented by software, firmware, or a combination of software and firmware. The software or firmware is written as a program and stored in memory 53. In the control circuit 50, the processor 52 reads and executes the program stored in memory 53 to realize the functions of the control devices 2, 2A, 2B, and 2C. In other words, the control circuit 50 is equipped with memory 53 for storing the program that will ultimately execute the processing of the control devices 2, 2A, 2B, and 2C. This program can also be said to cause the computer system to execute the procedures and methods of processing of the control devices 2, 2A, 2B, and 2C. Memory 53 is also used as temporary memory when the processor 52 executes various processes.

[0103] Here, the command generation unit 11 and command correction unit 12 of control devices 2, 2A, 2B, and 2C, the sensor processing unit 13 of control devices 2A and 2B, the vibration determination unit 14 of control device 2B, and the cutting thickness detection unit 15 of control device 2C are referred to as the processing units of control devices 2, 2A, 2B, and 2C. The processing units of control devices 2, 2A, 2B, and 2C are realized by using a processor 52 and a memory 53.

[0104] The processor 52 is a CPU (Central Processing Unit). The processor 52 may also be a central processing unit, processing unit, arithmetic unit, microprocessor, microcomputer, processor, or DSP (Digital Signal Processor). The memory 53 may be, for example, a non-volatile or volatile semiconductor memory such as RAM (Random Access Memory), ROM (Read Only Memory), flash memory, EPROM (Erasable Programmable Read Only Memory), EEPROM® (Electrically Erasable Programmable Read Only Memory), magnetic disk, flexible disk, optical disk, compact disk, minidisc, or DVD (Digital Versatile Disc).

[0105] Figure 13 shows an example of hardware when the functions of control devices 2, 2A, 2B, and 2C are realized using a general-purpose processor 52 and memory 53. The functions of control devices 2, 2A, 2B, and 2C may also be realized by dedicated hardware circuits. Figure 14 shows an example of the configuration of a dedicated hardware circuit 55 according to embodiments 1 to 4.

[0106] The dedicated hardware circuit 55 includes an input section 51, an output section 54, and a processing circuit 56. The processing units of the control devices 2, 2A, 2B, and 2C are realized by the processing circuit 56. The processing circuit 56 is a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or a circuit combining these. Each function of the control devices 2, 2A, 2B, and 2C may be realized by the processing circuit 56 separately for each function, or all functions may be realized together by the processing circuit 56. In addition, the control devices 2, 2A, 2B, and 2C may be realized by combining the control circuit 50 and the hardware circuit 55.

[0107] The configurations shown in each of the embodiments described above are examples of the content of this disclosure. The configurations of each embodiment can be combined with other known technologies. The configurations of each embodiment may be combined with each other as appropriate. It is possible to omit or modify parts of the configurations of each embodiment without departing from the gist of this disclosure.

[0108] 1, 1A, 1B, 1C Machining system, 2, 2A, 2B, 2C Control device, 3, 3A, 3B, 3C Machine tool, 11 Command generation unit, 12 Command correction unit, 13 Sensor processing unit, 14 Vibration determination unit, 15 Cutting thickness detection unit, 21 Spindle drive unit, 22 X-axis drive unit, 23 Y-axis drive unit, 24 Z-axis drive unit, 25 Sensor, 30 Bed, 31 Column, 32 Table, 33 Head, 34 Spindle, 35 Workpiece, 36 Tool, 50 Control circuit, 51 Input unit, 52 Processor, 53 Memory, 54 Output unit, 55 Hardware circuit, 56 Processing circuit, D Feed direction, G1 First cutting edge, G2 Second cutting edge, G3 Third cutting edge, G4 Fourth cutting edge, K1, K2 Rotation direction, Oa Geometric center, Ob Rotation center, qa, qb Trajectory, S vibration direction.

Claims

1. A control device for a machine tool, comprising a feed drive unit for operating a tool having three or more cutting edges and a workpiece relative to each other, and a spindle drive unit for rotating the tool, the control device comprising: a command generation unit for generating rotation commands for the spindle drive unit and operation commands for the feed drive unit; and a command correction unit for suppressing vibrations of the tool that occur during machining of the workpiece by superimposing vibrations of amplitude, frequency, and phase that cause uneven thickness of the cutting portion within the cutting portion by each cutting edge onto the operation of the tool relative to the workpiece.

2. The control device for a machine tool according to claim 1, characterized in that the command generation unit generates an operation command for a first feed drive unit which is a feed drive unit that operates the tool and the workpiece relatively in a first direction perpendicular to the rotation axis of the tool, and an operation command for a second feed drive unit which is a feed drive unit that operates the tool and the workpiece relatively in a second direction perpendicular to the rotation axis and each of the first directions, and the command correction unit corrects the operation command for the first feed drive unit and the operation command for the second feed drive unit.

3. The control device for a machine tool according to claim 1 or 2, characterized in that the frequency of the vibration operation is determined such that the cutting blade that produces the thinnest cut portion per cutting blade among the three or more cutting blades is the same cutting blade for each rotation of the tool.

4. The control device for a machine tool according to claim 1 or 2, characterized in that the frequency of the vibration operation is determined such that the cutting edge that produces the thinnest cut portion among the three or more cutting edges is not the same cutting edge during two consecutive rotations of the tool.

5. The control device for a machine tool according to any one of claims 1 to 4, characterized in that the command correction unit changes the frequency of the vibration operation when the rotational speed of the tool is changed.

6. A control device for a machine tool according to any one of claims 3 to 5, comprising a sensor processing unit that calculates the frequency of vibration based on the result of detecting vibration of the tool that occurs during the machining of the workpiece, wherein S1 is the target value of the rotational speed of the tool, fc is the frequency calculated by the sensor processing unit, n is the number of cutting edges of the tool, and m is an arbitrary natural number, the sensor processing unit outputs an adjustment command to the command generation unit for adjusting the rotational speed of the tool to the target value that satisfies the following calculation formula (1), and the command generation unit outputs the rotation command that has been adjusted according to the adjustment command.

7. The control device for a machine tool according to claim 6, further comprising a vibration determination unit that determines whether or not the vibration of the tool has been suppressed by adjusting the rotational speed of the tool in accordance with the adjustment command, wherein the sensor processing unit, when it is determined that the vibration of the tool has not been suppressed, changes the natural number in the calculation formula to recalculate the target value and outputs the adjustment command to the command generation unit for adjusting the rotational speed of the tool to the recalculated target value.

8. A control device for a machine tool according to any one of claims 1 to 7, comprising a cutting thickness detection unit for detecting the thickness of the cutting portion, wherein the command correction unit changes at least one of the amplitude and the phase in the vibration operation according to the thickness detected by the cutting thickness detection unit.

9. A machining system comprising: a machine tool having a feed drive unit for moving a tool having three or more cutting edges and a workpiece relative to each other; a spindle drive unit for rotating the tool; and a control device for controlling the machine tool, wherein the control device comprises: a command generation unit for generating rotation commands for the spindle drive unit and operation commands for the feed drive unit; and a command correction unit for suppressing vibrations of the tool that occur during machining of the workpiece by superimposing vibrations of amplitude, frequency, and phase that cause uneven thickness of the cut portion within the cut portion by each cutting edge onto the movement of the tool relative to the workpiece.

10. A program characterized by causing a computer system to execute the following steps: generating a rotation command for a spindle drive unit that rotates a tool having three or more cutting edges, and an operation command for a feed drive unit that moves the tool and the workpiece relative to each other; and performing a correction on the operation command to suppress vibrations of the tool that occur during the machining of the workpiece by superimposing vibrations of amplitude, frequency, and phase that cause the thickness of the cutting portion in the cutting portion by each of the cutting edges to be uneven on the operation of the tool relative to the workpiece.

11. A machining method characterized by comprising the steps of: generating a rotation command for a spindle drive unit that rotates a tool having three or more cutting edges, and an operation command for a feed drive unit that moves the tool and the workpiece relative to each other; and suppressing vibrations of the tool that occur during machining of the workpiece by superimposing vibrations of amplitude, frequency, and phase that cause the thickness of the cut portion to be uneven within the cut portion by each of the cutting edges onto the operation of the tool relative to the workpiece.

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