Machine tool and processing method

Abstract

To provide a machine tool which can inhibit waviness of a processed surface.SOLUTION: A machine tool includes: a workpiece spindle; a first spindle; a second spindle; a second spindle support part rotatably supporting the second spindle; at least one clamp having one end part fixed to the second spindle support part, the other end part engaged with the second spindle, and a linear motion device which expands or contracts along a second axis; a detector configured to detect vibration of a processing tool in a processing step in which the workpiece spindle and the first spindle are rotated to process a workpiece in accordance with processing conditions; and a control unit configured to control the linear motion device with a control signal. The control unit includes: an acquisition unit which acquires vibration data indicating vibration of the processing tool detected by the detector; and a creation unit which uses the acquired vibration data to create a vibration control signal which is a control signal for causing the first spindle to vibrate by expansion and contraction of the linear motion device so as to cancel out vibration of the processing tool. The control unit controls the linear motion device in accordance with the created vibration control signal.SELECTED DRAWING: Figure 9

Description

[Technical Field]

[0001] The present disclosure relates to machine tools and machining methods. [Background technology]

[0002] Conventionally, there are techniques for reducing waviness that occurs on the machined surface due to vibration of the grinding wheel in grinding processes. For example, Patent Document 1 discloses a gear grinding machine that reduces waviness by controlling the preload applied to the bearing of the grinding wheel spindle that supports the grinding wheel. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2017-159377 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the method of Patent Document 1 requires the provision of a preload applying means. This problem is not limited to gear grinding machines, but is common to other machine tools that have a spindle to which a processing tool is attached. [Means for solving the problem]

[0005] The present disclosure can be realized in the following forms.

[0006] (1) According to a first aspect of the present disclosure, there is provided a machine tool including: a work spindle to which a workpiece is attached; a first spindle to which a processing tool for processing the workpiece is attached; a second spindle that rotates about a second axis perpendicular to the first axis of the first spindle and rotates the first spindle about the second axis; a second spindle support unit that rotatably supports the second spindle; at least one clamp having one end, the other end, and a linear motion device that expands and contracts along the second axis and limits rotation of the second spindle; a detector that detects vibrations of the processing tool during a processing step in which the workpiece is processed by rotating the work spindle and the first spindle in accordance with processing conditions; and a control unit that controls the linear motion device using a control signal. The linear motion device has one end fixed to either the second spindle support portion or the second spindle, and the other end engaged with the other of the second spindle support portion or the second spindle, and the at least one clamp presses the second spindle against the second spindle support portion by extending or retracting the linear motion device, thereby limiting the rotation of the second spindle. The control unit has an acquisition unit that acquires vibration data indicating the vibration of the processing tool detected by the detector, and a creation unit that uses the acquired vibration data to create a vibration control signal that is the control signal for vibrating the first spindle by extending or retracting the linear motion device so as to cancel out the vibration of the processing tool, and the control unit controls the linear motion device according to the created vibration control signal. According to this embodiment, vibration of the processing tool can be suppressed by controlling the linear motion device using the vibration control signal created by the creation unit. A linear motion device provided in a machine tool for limiting rotation of the second spindle can be used to suppress vibration of the processing tool. (2) In the machine tool of the above aspect, the control unit includes a first vibration data creating unit that creates first vibration data having a phase that differs from the phase of the vibration data by a provisional phase difference and a predetermined reference data amplitude; a second vibration data creating unit that creates second vibration data by changing the first vibration data to a provisional magnification of the reference data amplitude; and a second vibration data creating unit that acquires the amplitude of the vibration data in a state where the linear motion device is controlled in accordance with the provisional vibration control signal created using the first vibration data by setting a first value of the provisional phase difference to a plurality of first values, and acquires the amplitude of the vibration data in a state where the linear motion device is controlled in accordance with the provisional vibration control signal created using the first vibration data by setting a first value of the provisional phase difference to a plurality of first values, and acquires the amplitude of the vibration data by using the first value among the plurality of first values ​​that minimizes the amplitude of the vibration data. and a second determination unit that acquires the amplitude of the vibration data in a state in which the linear motion device is controlled in accordance with the provisional vibration control signal created using the second vibration data by setting the second value of the provisional magnification to a plurality of second values, and determines the amplitude of the vibration data for creating the vibration control signal using the second value among the plurality of second values ​​that minimizes the amplitude of the vibration data. The creation unit may create the vibration control signal using the vibration data having the phase difference determined by the first determination unit and the amplitude determined by the second determination unit. According to this aspect, the vibration control signal can be created by adapting it to the current vibration data. Therefore, vibration can be suppressed with high accuracy. (3) In the machine tool of the above aspect, the creation unit may, in a preparation step executed before the machining step, calculate a transfer function that uses the provisional excitation control signal as an input and the vibration data as an output, and create the excitation control signal by inputting data of the opposite phase of the vibration data in a state where the linear motion device is not controlled according to the excitation control signal into an inverse function of the calculated transfer function. According to this aspect, the excitation control signal can be created using the previously created transfer function and the current vibration data. (4) In the machine tool of the above aspect, in the machining process, machining is performed by changing the relative position of the machining tool with respect to the workpiece in synchronization with the rotation period of the workpiece spindle, and the control unit includes: a graph information acquisition unit that acquires graph information representing a graph with the vibration frequency of the vibration data on the horizontal axis and the period of undulations generated on the machined surface of the workpiece on the vertical axis at a rotation speed of the workpiece spindle that is the same as the machining conditions; and a judgment unit that judges whether the frequency of the vibration data in a state where the linear motion device is not controlled in accordance with the vibration control signal is higher than a predetermined upper limit frequency, and when the judgment unit judges that the frequency of the vibration data is higher than the upper limit frequency, the creation unit may obtain the period of the undulations corresponding to the vibration frequency in the graph, obtain the vibration frequency in the graph that is lower than the upper limit frequency and corresponds to the obtained period of the undulations, and create the vibration control signal using the vibration data of the obtained vibration frequency. According to this embodiment, even if the frequency of the vibration data is higher than the upper limit frequency to which the linear motion device can respond, the waviness occurring on the machined surface of the workpiece can be suppressed by applying vibrations of a frequency to which the linear motion device can respond to the first spindle. (5) In the machine tool of the above aspect, the control unit may include an amplitude determination unit that determines whether the amplitude of the vibration data when the linear motion device is not controlled in accordance with the vibration control signal is greater than a predetermined reference amplitude, and the creation unit may create the vibration control signal using the latest vibration data when the amplitude determination unit determines that the amplitude of the vibration data is greater than the reference amplitude. Vibration data may fluctuate even during machining due to, for example, wear of the machining tool. Therefore, according to this aspect, even if the amplitude of the vibration data becomes greater than the reference amplitude, the vibration control signal can be created again. Therefore, even if the vibration data fluctuates, waviness of the machined surface can be suppressed. (6) In the machine tool of the above aspect, the at least one clamp may include a plurality of clamps, and the creation unit may create the vibration control signal for each of the plurality of clamps. According to this aspect, when there are a plurality of clamps, a vibration control signal can be created for the linear motion device of each clamp. In particular, when the processing tool vibrates not only in one direction but also in multiple directions, the phases of the plurality of vibration control signals corresponding to the plurality of clamps can be shifted from one another to apply vibration to the first spindle in multiple directions. Therefore, when vibrations occur in the processing tool in multiple directions, the vibrations in these multiple directions can be suppressed. (7) According to a second aspect of the present disclosure, there is provided a method for mass-producing products using a machine tool, the machine tool including: a work spindle to which a workpiece is attached; a first spindle to which a processing tool for processing the workpiece is attached; a second spindle that rotates about a second axis perpendicular to the first axis of the first spindle, the second spindle for rotating the first spindle about the second axis; a second spindle support portion that rotatably supports the second spindle; at least one clamp having one end, the other end, and a linear motion device that expands and contracts along the second axis, the at least one clamp for restricting rotation of the second spindle; and a detector that detects vibrations of the processing tool during a processing step in which the workpiece is processed by rotating the work spindle and the first spindle in accordance with processing conditions. The one end is fixed to either the second spindle support portion or the second spindle, and the other end engages with the other of the second spindle support portion or the second spindle, and the at least one clamp presses the second spindle to the second spindle support portion by extending or retracting the linear motion device, thereby restricting rotation of the second spindle. The machining method includes: a first step of generating a vibration control signal to vibrate the first spindle by extending or retracting the linear motion device so as to cancel out vibration of the machining tool detected by the detector in the machining process using a prototype of the product as the workpiece; and a second step of controlling the linear motion device in accordance with the vibration control signal generated in the first step in the machining process of mass-produced products of the product. According to this aspect, vibration of the machining tool can be suppressed in the mass-produced production using the vibration control signal obtained in advance. The present disclosure can be realized in various forms, and in addition to the forms described above, can be realized in the form of, for example, a control method for a linear motion device, a control method for a machine tool, or a control program for a linear motion device. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 2 is an explanatory diagram showing a schematic configuration of a grinding machine. [Figure 2] FIG. 2 is a front schematic view of the ball screw and the second main spindle moving device. [Figure 3] FIG. 2 is a diagram illustrating the positional relationship between a workpiece and a grinding wheel. [Figure 4] 3 is a cross-sectional schematic diagram of the grinding machine taken along a plane passing through the second axis and parallel to the XY plane. FIG. [Figure 5] FIG. 2 is a diagram showing the electrical configuration of the grinding machine. [Figure 6] FIG. 1 is a diagram illustrating machining of a workpiece. [Figure 7] FIG. 2 is a diagram illustrating the positional relationship between a grinding wheel and a workpiece. [Figure 8] FIG. 10 is a diagram illustrating the relationship between disturbance and cutting amount. [Figure 9] 10 is a flowchart showing a procedure for vibration control signal generation processing. [Figure 10] 10A and 10B are diagrams illustrating a vibration control signal generation process. [Figure 11] FIG. 10 is a diagram illustrating a transfer function. [Figure 12] 10 is a flowchart showing a procedure for vibration data setting processing. [Figure 13] FIG. 10 is a diagram illustrating a graph drawn based on graph information. DETAILED DESCRIPTION OF THE INVENTION

[0008] A. First embodiment: A1.Mechanical configuration of grinding machine: FIG. 1 is an explanatory diagram showing the schematic configuration of a grinding machine 100 as a machine tool. FIG. 1 shows an X-axis, a Y-axis, and a Z-axis that are orthogonal to each other. The X-axis and the Z-axis are coordinate axes parallel to the horizontal plane. The Y-axis is a coordinate axis parallel to the vertical direction. The arrows representing the X-axis, Y-axis, and Z-axis in FIG. 1 and the arrows representing the X-axis, Y-axis, and Z-axis in other figures point in the same direction. When specifying the direction, positive and negative signs are used in combination to indicate the direction, with "+" indicating the positive direction indicated by the arrow and "-" indicating the negative direction opposite to the direction indicated by the arrow.

[0009] The grinding machine 100 includes a bed 10, a workpiece spindle 20, a workpiece spindle moving mechanism 30, a ball screw 40, a first spindle 50, a first spindle housing 52, a second spindle moving device 60, and a control unit 80. The grinding machine 100 processes a cylindrical workpiece W held by the workpiece spindle 20 into an external gear by grinding the outer peripheral surface of the workpiece W with a grinding wheel S as a processing tool held by the first spindle 50. The grinding machine 100 is configured so that the relative position of the grinding wheel S with respect to the workpiece spindle 20 is changed by the second spindle moving device 60, thereby processing the workpiece W into a helical gear.

[0010] The bed 10 supports the work spindle 20, the first spindle 50, etc. The bed 10 is made of, for example, cast iron.

[0011] The workpiece axis moving mechanism 30 rotatably supports the workpiece spindle 20. The workpiece spindle 20 rotates around a workpiece axis AW that is parallel to the Y-axis. The workpiece axis moving mechanism 30 moves along the Y-axis. A workpiece W is attached to the workpiece spindle 20.

[0012] The first spindle 50 is rotatably supported by a first spindle housing 52. A grinding wheel S is attached to the tip of the first spindle 50. In this embodiment, the grinding wheel S has a helical grinding tooth (not shown). An acceleration sensor 71 is attached inside the first spindle housing 52 as a detector for detecting vibrations. The first spindle 50 rotates around a first axis A1. The first spindle 50 is also called the grinding wheel spindle. The first spindle 50 moves along the first axis A1 by a ball screw 40.

[0013] The ball screw 40 includes a ball screw base 41, two guide rails 42, a screw shaft 43, and a ball screw motor 44. The two guide rails 42 are fixed to the ball screw base 41. The screw shaft 43 is disposed between the two guide rails 42. The screw shaft 43 is rotatably fixed to the ball screw base 41 by a bearing (not shown). The ball screw motor 44 is attached to the end of the screw shaft 43 coaxially with the screw shaft 43. A first spindle housing 52 is movably attached to the screw shaft 43. The rotational force of the ball screw motor 44 is transmitted to the ball screw 40, causing the screw shaft 43 to rotate. When the screw shaft 43 rotates, the first spindle housing 52 moves along the ball screw 40, guided by the two guide rails 42. When the first spindle housing 52 moves, the first spindle 50 supported by the first spindle housing 52 also moves in conjunction with it.

[0014] The second spindle moving device 60 has a second spindle support portion 61, a second spindle 62, and multiple clamps 63. The second spindle 62 is rotatably supported by the second spindle support portion 61. The second spindle 62 rotates around a second axis A2 parallel to the X-axis. The second spindle 62 has a second spindle head 62a exposed from the second spindle support portion 61 and a second spindle base portion 62b housed inside the second spindle support portion 61. The ball screw base 41 is fixed to the second spindle head 62a. When the second spindle 62 rotates around the second axis A2, the first spindle housing 52 and the first spindle 50 rotate in conjunction with it. This changes the angle of the grinding wheel S with respect to the workpiece W. The second spindle 62 is also called the pivot axis.

[0015] Fig. 2 is a schematic front view of the ball screw 40 and the second main spindle moving device 60 as viewed along the X direction. Fig. 2 is a diagram showing the first main spindle 50 positioned at a reference position. The reference position of the first main spindle 50 refers to the position where the first axis A1 is parallel to the Z axis.

[0016] FIG. 3 is a diagram illustrating the positional relationship between the workpiece W and the grinding wheel S. In the machining process, the relative position of the grinding wheel S with respect to the workpiece W is changed in synchronization with the rotation cycle of the workpiece spindle 20, and machining is performed. FIG. 3 shows a case where the second spindle 62 has rotated from a reference position. As described above, the workpiece W rotates around the workpiece axis AW. The grinding wheel S rotates around the first axis A1. The rotation angle of the second spindle 62 with respect to the reference position is also called the swivel angle. In this embodiment, the maximum value of the swivel angle is approximately several tens of degrees.

[0017] When machining the workpiece W into a helical gear whose tooth trace TL is inclined relative to the axis of the workpiece W, prior to machining, the second spindle 62 is rotated so that the first axis A1 of the first spindle 50 is inclined relative to the Z axis. Then, with the workpiece W set at a first position PO1 in the Y direction, the grinding wheel S and the workpiece W are rotated so that the grinding teeth of the grinding wheel S mesh with the teeth GH of the workpiece W. Once machining of all the teeth GH of the workpiece W at the first position PO1 is completed, the workpiece W is moved from the first position PO1 to a second position PO2. Note that, during the process of moving the workpiece W to the second position PO2, the workpiece W is rotated so that the grinding teeth of the grinding wheel S mesh with the teeth GH of the workpiece W. Then, similar to the first position PO1, the grinding wheel S and the workpiece W are rotated so that the grinding teeth of the grinding wheel S mesh with the teeth GH of the workpiece W, and the teeth GH are machined at the second position PO2. In this way, the teeth GH of the workpiece W are machined by repeating the movement of the workpiece W in the Y direction and the rotation of the grindstone S and the workpiece W.

[0018] 4 is a schematic cross-sectional view of the grinding machine 100 taken along a plane that passes through the second axis A2 and is parallel to the XY plane. As shown in FIG. 4, the second spindle moving device 60 has a second shaft bearing 65 and a second shaft rotating motor 66 in addition to the components described above.

[0019] The second shaft bearing 65 is a ball bearing that rotatably supports the second main shaft 62. In this embodiment, a bearing that can support both thrust loads and radial loads is used as the second shaft bearing 65. The second shaft rotation motor 66 is disposed coaxially with the second main shaft 62. The rotational force of the second shaft rotation motor 66 causes the second main shaft 62 to rotate around the second axis A2.

[0020] As shown in FIG. 2, in this embodiment, the multiple clamps 63 include four clamps 63. In a front view taken along the X-axis direction, the clamps 63 are arranged at equal intervals along a circle centered on the second axis A2. As shown in FIG. 4, the second axis head 62a is formed with a groove 67 for receiving the clamp 63 at a position where the clamp 63 is attached. As shown in FIG. 2, in a front view taken along the X-axis direction, the groove 67 has an arc-like shape centered on the second axis A2. The length of the arc corresponds to the rotation angle range of the second main shaft 62.

[0021] As shown in FIG. 4, the clamp 63 has one end 63a, the other end 63b, and a linear motion device 64. The one end 63a is fixed to either the second main shaft support portion 61 or the second main shaft 62. The other end 63b engages with the other of the second main shaft support portion 61 or the second main shaft 62. In this embodiment, the one end 63a is fixed to the second main shaft support portion 61. The other end 63b engages with the second main shaft 62, specifically the second shaft head 62a. The linear motion device 64 expands and contracts along the second axis A2.

[0022] In this embodiment, the linear motion device 64 is a hydraulic linear motion cylinder. Note that, in addition to a hydraulic linear motion cylinder, a pneumatic linear motion cylinder, an electromagnetic linear motion cylinder, or the like can also be used as the linear motion device 64.

[0023] The linear motion device 64 has a piston rod 64a, a cylinder 64b, and a piston 64d. One end of the piston rod 64a is inserted into the cylinder 64b. A piston 64d is fixed to one end of the piston rod 64a. The portion of the piston rod 64a exposed from the cylinder 64b is housed inside a groove 67 formed in the second shaft head 62a. A cylindrical other end portion 63b is attached to the other end of the piston rod 64a. The piston rod 64a moves along the axial direction by adjusting the pressure in the internal space defined by the cylinder 64b and the piston 64d. The other end portion 63b moves along the second axis A2 in conjunction with the piston rod 64a.

[0024] The clamp 63 presses the second main shaft 62 against the second main shaft support portion 61 as the linear motion device 64 extends or retracts, thereby restricting the rotation of the second main shaft 62. In this embodiment, when restricting the rotation of the second main shaft 62, the hydraulic pressure of the clamp 63 is controlled so that the other end 63b approaches the one end 63a. As a result, the linear motion device 64 retracts, causing the other end 63b to press the second main shaft 62 against the second main shaft support portion 61, thereby restricting the rotation of the second main shaft 62. On the other hand, when rotating the second main shaft 62, the hydraulic pressure of the clamp 63 is controlled so that the other end 63b moves away from the one end 63a. As a result, as the linear motion device 64 extends, the pressing force exerted by the other end 63b on the second main shaft 62 is eliminated, and the second main shaft 62 is set to a rotatable state.

[0025] A2.Processing steps: In the machining process of the workpiece W, a setting process is performed in which the second spindle 62 is rotated by a desired rotation angle before the machining process in which the grinding wheel S comes into contact with and grinds the workpiece W. In detail, in the setting process, after the restriction on the rotation of the second spindle 62 by the clamp 63 is released, the second spindle 62 is rotated by the desired rotation angle by the rotation of the second shaft rotating motor 66. Thereafter, the rotation of the second spindle 62 is restricted by the clamp 63.

[0026] A3. Grinding machine electrical configuration: FIG. 5 is a diagram illustrating the electrical configuration of the grinding machine 100. As shown in FIG. 5, the control unit 80 is configured as a computer having a processor 81 and a storage unit 82. The storage unit 82 is realized by a memory such as a RAM or a ROM. The processor 81 and the storage unit 82 are communicatively connected via a bus (not shown). The processor 81 has, as functional units, an acquisition unit 84, a creation unit 85, a determination unit 86, a first vibration data creation unit 87, a second vibration data creation unit 88, a first determination unit 89, a second determination unit 90, and an amplitude determination unit 91. Each functional unit is realized by executing a program stored in the storage unit 82. The control unit 80 may be configured to include an electrical circuit such as an ASIC (application specific integrated circuit).

[0027] The acquiring unit 84 acquires vibration data indicating the vibration of the grinding wheel S detected by the acceleration sensor 71. The creating unit 85 uses the acquired vibration data to create a vibration control signal, which is a control signal for vibrating the first spindle 50 by the extension and contraction of the linear motion device 64 so as to cancel out the vibration of the grinding wheel S.

[0028] The vibration control signal is a control signal to the linear motion device 64, and includes, for example, a direct or indirect command value for hydraulic pressure, a direct or indirect command value for the hydraulic pressure change speed, etc. In this embodiment, the vibration control signal is created using vibration data. The vibration data is data representing the periodic displacement, i.e., vibration, applied to the first main spindle 50 by the extension and contraction of the linear motion device 64.

[0029] The first vibration data creation unit 87 creates first vibration data having a phase that differs from the phase of the vibration data by a provisional phase difference and a predetermined reference data amplitude. The second vibration data creation unit 88 creates second vibration data by modifying the first vibration data so that the first vibration data is a provisional magnification of the reference data amplitude. The first determination unit 89 acquires the amplitude of the vibration data in a state in which the linear motion device 64 is controlled in accordance with a provisional vibration control signal created using the first vibration data by setting the first value of the provisional phase difference to a plurality of first values. Then, the first determination unit 89 determines the phase difference of the vibration data relative to the vibration data for creating the vibration control signal using the first value that minimizes the amplitude of the vibration data among the plurality of first values. The second determination unit 90 acquires the amplitude of the vibration data in a state in which the linear motion device 64 is controlled in accordance with a provisional vibration control signal created using the second vibration data by setting the second value of the provisional magnification to a plurality of second values, and determines the amplitude of the vibration data for creating the vibration control signal using the second value among the plurality of second values ​​that gives the smallest amplitude of the vibration data.

[0030] The amplitude determining unit 91 determines whether the amplitude of the vibration data in a state in which the linear motion device 64 is controlled in accordance with the vibration control signal is greater than a predetermined reference amplitude.

[0031] The storage unit 82 stores hydraulic drive data 95. The hydraulic drive data 95 is data for converting vibration data into a vibration control signal. The hydraulic drive data 95 is, for example, data that associates vibration data with a command value for hydraulic pressure to be applied to the linear motion device 64 and a command value for the hydraulic pressure change speed. The hydraulic drive data 95 is data that is obtained in advance by experiment or the like.

[0032] In addition to the above components, the grinding machine 100 also includes a workpiece shaft rotation motor 21, a first shaft rotation motor 51, and a coolant pump 12. The workpiece shaft rotation motor 21 is a motor for rotating the workpiece spindle 20. The first shaft rotation motor 51 is a motor for rotating the first spindle 50. The coolant pump 12 is a pump for supplying coolant to cool the machining surface MS of the workpiece W during the machining process. A control unit 80 controls each component, such as the workpiece shaft rotation motor 21 and the first shaft rotation motor 51. An acceleration sensor 71 detects accelerations along the X-axis, Y-axis, and Z-axis, and transmits the detected values ​​to the control unit 80.

[0033] A4. Explanation of machined surface waviness: FIG. 6 is a diagram illustrating machining in this embodiment. FIG. 6 shows one tooth GH of the workpiece W. As shown in FIG. 6, in this embodiment, the position of the grinding wheel S is changed six times along the tooth trace direction from the first period PE1 to the sixth period PE6. The cutting amount in the first period PE1 is referred to as the first cutting amount d1. Similarly, the cutting amounts in each of the second period PE2 to the sixth period PE6 are referred to as the second cutting amount d2 to the sixth cutting amount d6. Since the cutting amounts from the first cutting amount d1 to the sixth cutting amount d6 vary, waviness occurs in the machined surface MS.

[0034] FIG. 7 is a diagram illustrating the positional relationship between the grinding wheel S and the workpiece W. FIG. 7 is a schematic diagram of a cross section taken along a plane passing through the first axis A1 and parallel to the XZ plane. FIG. 8 is a diagram illustrating the relationship between disturbance and the amount of removal. The horizontal axis of FIG. 8 represents time. The vertical axis of FIG. 8 represents displacement.

[0035] The solid line in Figure 8 indicates the displacement of the disturbance. The dashed line in Figure 8 indicates the displacement of the workpiece position. Note that the displacement of the disturbance is the displacement of the grinding wheel S in the X direction due to the disturbance, with the +X direction being positive and the -X direction being negative, based on the first axis A1, as shown in Figure 7. The workpiece position in Figure 8 is the displacement of the reference point RP on the outer surface of the workpiece W, as shown in Figure 7. More specifically, the workpiece position in Figure 8 is the displacement of the reference point RP in the X direction, with the +X direction being positive and the -X direction being negative, based on the reference line RL, which passes through the workpiece axis AW and is parallel to the Z axis, as shown in Figure 7. Figure 8 has two vertical axes. The left vertical axis in Figure 8 is the vertical axis of the disturbance. The right vertical axis in Figure 8 is the vertical axis of the workpiece position. Figure 8 is a diagram showing the case where the workpiece W rotates at a constant angular velocity. Twice the amplitude of the waveform showing the workpiece position in Figure 8 corresponds to the outer diameter WD of the workpiece W. The period PE of the waveform showing the work position shown in Fig. 8 is the reciprocal of the rotation speed of the work spindle 20. In Fig. 8, the vertical axis is adjusted so that the amplitude of the disturbance waveform and the amplitude of the work position waveform match.

[0036] The inventors have found that disturbances cause periodic displacement of the grinding wheel S. The disturbances are thought to be caused by unbalance of the grinding wheel S, vibrations transmitted from the coolant pump 12, and fluctuations in grinding wheel resistance due to unevenness on the grinding wheel surface or machined surface MS of the grinding wheel S. Of these disturbances, unbalance of the grinding wheel S and vibrations transmitted from the coolant pump 12 are thought to be the cause of periodic displacement of the grinding wheel S, i.e., vibration.

[0037] The inventors have confirmed that there is a strong correlation between the displacement of the intersection point PI between the phase indicated by the waveform of the disturbance and the waveform of the workpiece position in FIG. 8 and the amount of removal. Note that FIG. 8 illustrates the intersection point PI at the reference point RP. Therefore, in this embodiment, the clamps 63 are controlled to cancel out the vibration of the grinding wheel S caused by the disturbance. This makes it possible to suppress waviness of the machined surface MS caused by the disturbance. Specifically, the second spindle 62 of the second spindle moving device 60 is displaced by extending and retracting the four clamps 63 of the second spindle moving device 60. This makes it possible to displace the first spindle 50 and the grinding wheel S attached to the second spindle 62.

[0038] In order to suppress vibration of the grinding wheel S, it is possible to increase the rigidity of the first spindle 50, the ball screw 40, etc. However, if the diameter of the first spindle 50 is increased to increase the rigidity, the weight of the first spindle 50 may increase, which may result in increased vibration. It is also possible to increase the rigidity of the first-axis rotation motor 51, for example. However, since increasing the rigidity of the motor tends to increase the response speed, increasing the rigidity of the motor may result in unstable control. In this regard, the above-mentioned expected disadvantages can be avoided by adopting a method of suppressing vibration using the displacement of the linear motion device 64.

[0039] A5. Vibration control signal creation process: 9 is a flowchart showing the procedure of the vibration control signal generation process. When the processing step is started, the control unit 80 sets the variable n to an initial value of "1" and starts the vibration control signal generation process.

[0040] In step S10, the acquisition unit 84 receives and acquires vibration data, which is a detection value in the X direction, transmitted from the acceleration sensor 71. The acquisition unit 84 stores the acquired vibration data in the storage unit 82 as the nth vibration data, where "n" is the value of the variable n. The vibration data acquired in step S10 is vibration data in a state in which the linear motion device 64 is not controlled in accordance with the vibration control signal. The "state in which the linear motion device 64 is not controlled in accordance with the vibration control signal" is, in detail, a state in which the hydraulic pressure of the linear motion device 64 is controlled to be approximately constant so that the clamp 63 limits the rotation of the second main shaft 62.

[0041] In step S12, the first vibration data creation unit 87 creates first vibration data whose amplitude is a predetermined reference data amplitude Ath and whose phase is delayed by time θ from the vibration data. In other words, the time θ is the phase difference between the vibration data and the first vibration data. In this embodiment, the time θ is a value obtained by dividing the period of the vibration data by an integer. The time θ is also referred to as a provisional phase difference. The value of this time θ is also referred to as a first value. The creation unit 85 uses the hydraulic drive data 95 and the first vibration data to create a provisional vibration control signal for displacing the first spindle 50.

[0042] The control unit 80 controls the linear motion devices 64 according to the created provisional vibration control signal. In this embodiment, the control unit 80 controls the four linear motion devices 64 according to the same vibration control signal. Specifically, the control unit 80 controls the hydraulic pressure of the linear motion devices 64 using the provisional vibration control signal in synchronization with the period PE of the acquired amplitude data. When the linear motion device 64 operates so that the other end 63b approaches the one end 63a, the second axis head 62a is displaced periodically in the X direction in conjunction with the linear motion device 64. The vibration control signal is adjusted within a hydraulic pressure range that allows the linear motion device 64 to exert a force sufficient to appropriately limit the rotation of the first spindle 50.

[0043] In step S14, the acquisition unit 84 acquires vibration data in the same manner as in step S10. The acquisition unit 84 stores the acquired vibration data in the storage unit 82 as the (n+1)th vibration data.

[0044] In step S16, the determination unit 86 determines whether the amplitude A(n+1) of the (n+1)th vibration data is smaller than the amplitude A(n) of the nth vibration data. The amplitude A used for the determination is the average value of the amplitudes A detected at a predetermined time, excluding singular points. If it is determined in step S16 that the amplitude A(n+1) of the (n+1)th vibration data is smaller than the amplitude A(n) of the nth vibration data, in step S18, the creation unit 85 sets the time obtained by adding a predetermined shift time θs to the time θ as a new time θ, increments the variable n, and returns the process to step S12. By performing step S18, the time θ, which is the phase difference, is lengthened by the shift time θs. Therefore, in the next step S12, first vibration data having an increased phase difference from the vibration data is created. In this embodiment, the shift time θs is a value obtained by dividing the period of the vibration data by an integer.

[0045] If it is determined in step S16 that the amplitude A of the (n+1)th vibration data is not smaller than the amplitude A of the nth vibration data, in step S20, the first determination unit 89 determines the time θ with the smallest amplitude among the amplitude data up to the (n+1)th data as the phase difference between the vibration data of the excitation data for creating the excitation control signal. In this embodiment, the time θ of the nth amplitude data is determined as the phase difference of the vibration data of the excitation control signal for creating the excitation control signal.

[0046] In step S22, the creation unit 85 creates second vibration data by multiplying the amplitude of the first vibration data used to acquire the nth vibration data by m. This "m" is also referred to as a provisional magnification. The provisional magnification m is a value greater than 1. The value of the provisional magnification m is also referred to as a second value. As in step S12, the control unit 80 controls the linear motion device 64 using a provisional vibration control signal created by the creation unit 85 using the created second vibration data.

[0047] In step S24, the acquisition unit 84 acquires vibration data in the same manner as in step S10. The acquisition unit 84 stores the acquired vibration data in the storage unit 82 as the (n+1)th vibration data.

[0048] In step S26, it is determined whether the amplitude A(n+1) of the (n+1)th vibration data is smaller than the amplitude A(n) of the nth vibration data. If it is determined in step S26 that the amplitude A(n+1) of the (n+1)th vibration data is smaller than the amplitude A(n) of the nth vibration data, in step S28, the creation unit 85 sets the value obtained by adding a predetermined addition value ms to the temporary magnification m as a new temporary magnification m, increments the variable n, and returns the process to step S22. By performing step S28, the temporary magnification m is increased by the addition value ms. Therefore, in the next step S22, second vibration data with increased amplitude is created.

[0049] If it is determined in step S26 that the amplitude A(n+1) of the (n+1)th vibration data is not smaller than the amplitude A(n) of the nth vibration data, then in step S30, the second determination unit 90 determines the value of the provisional magnification m with the smallest amplitude among the amplitude data up to the (n+1)th data as the magnification of the vibration data for generating the vibration control signal. In other words, the provisional magnification m of the nth amplitude data is determined as the magnification of the vibration data for generating the vibration control signal. The generation unit 85 generates the vibration control signal using the vibration data having the determined phase difference of time θ and the amplitude of the determined magnification. After step S30 is performed, the control unit 80 terminates this processing routine. The control unit 80 controls the linear motion device 64 according to the generated vibration control signal. This suppresses the vibration of the grinding wheel S.

[0050] 10 is a diagram illustrating the vibration control signal generation process. By repeatedly performing step S18, the time θ is incremented by the shift time θs. In step S20, the time θ at which the amplitude of the vibration data at each phase is minimum is determined as the time θ for generating the vibration control signal.

[0051] Similarly, step S28 is repeated for the amplitude of the vibration data, and the provisional magnification m is increased by the additional value ms. In step S30, the magnification with the smallest amplitude among the vibration data at each magnification is determined as the magnification for generating the vibration control signal. Note that FIG. 10 is a graph in which the horizontal axis represents time or magnification and the vertical axis represents the amplitude of the amplitude data. The "set value" shown in FIG. 10 indicates the time determined by the first determination unit 89 or the magnification determined by the second determination unit 90.

[0052] After the vibration control signal creation process is performed, the amplitude determination unit 91 determines whether the amplitude of the vibration data acquired by the acquisition unit 84 is greater than the reference amplitude. The vibration data that the amplitude determination unit 91 determines is the vibration data acquired after the vibration control signal creation process is performed. Therefore, this vibration data is vibration data in a state in which the linear motion device 64 is controlled so as to suppress the vibration of the grinding wheel S. The degree of vibration of the grinding wheel S may change over time due to wear of the grinding wheel S, etc. Therefore, when the amplitude determination unit 91 determines that the amplitude of the vibration data is greater than the reference amplitude, it outputs an instruction to start the vibration control signal creation process. In the vibration control signal creation process, which is triggered by this start instruction, the vibration control signal created by the creation unit 85 is a vibration control signal created using the latest vibration data. Therefore, even if the vibration of the grinding wheel S changes over time, the vibration of the grinding wheel S can be suppressed.

[0053] According to the first embodiment described above, the control unit 80 includes an acquisition unit 84 and a creation unit 85. The acquisition unit 84 acquires vibration data indicating the vibration of the grinding wheel S. The creation unit 85 uses the vibration data to create a vibration control signal that controls the linear motion device 64 to vibrate the first spindle 50 so as to cancel out the vibration of the grinding wheel S. The control unit 80 controls the linear motion device 64 using the created vibration control signal. This suppresses the vibration of the grinding wheel S, thereby reducing waviness in the machined surface MS of the workpiece W. The linear motion device 64 is also provided to limit the rotation of the second spindle 62, which changes the angle of the grinding wheel S relative to the workpiece W. Therefore, the vibration of the grinding wheel S can be suppressed using the linear motion device 64 already installed in the grinding machine 100.

[0054] The control unit 80 also includes a first vibration data generating unit 87, a second vibration data generating unit 88, a first determining unit 89, and a second determining unit 90. The first vibration data generating unit 87 generates first vibration data whose phase differs from the phase of the vibration data by a time θ. The second vibration data generating unit 88 generates second vibration data by multiplying the amplitude of the first vibration data by m. The first determining unit 89 then determines the time θ at which the amplitude of the vibration data is minimum as the phase difference of the vibration data for generating the vibration control signal. The second determining unit 90 determines the magnification m at which the amplitude of the vibration data is minimum as the magnification of the vibration data for generating the vibration control signal. This allows for the generation of an appropriate vibration control signal by sequentially monitoring the vibration of the grinding wheel S, which is the output relative to the vibration control signal, which is the input to the linear motion device 64. The vibration control signal generated in this manner reflects the actual behavior of the grinding machine 100. Therefore, a vibration control signal that can accurately suppress the vibration of the grinding wheel S can be generated.

[0055] The control unit 80 also has an amplitude determination unit 91. When the amplitude determination unit 91 determines that the amplitude of the vibration data is greater than the reference amplitude, it executes a vibration control signal creation process. By performing the vibration control signal creation process, the creation unit 85 creates a vibration control signal using the latest vibration data. As a result, even if the degree of vibration of the grinding wheel S fluctuates over time, it is possible to create a vibration control signal that can suppress the vibration of the grinding wheel S after the fluctuation.

[0056] B. Second embodiment: In the first embodiment, the vibration control signal is adjusted by a trial and error method in the machining process. In this embodiment, a transfer function K is calculated in a preparation process executed before the machining process. Then, in the machining process, a vibration control signal is created using the transfer function K. The same configurations and processing steps as in the first embodiment are denoted by the same reference numerals, and detailed explanations will be omitted as appropriate.

[0057] FIG. 11 is a diagram illustrating the transfer function K in this embodiment. In this embodiment, the linear motion device 64 is described by way of example using a system in which the hydraulic pressure is adjusted by the aperture of a fluid control valve that controls the oil flow rate. The vibration control signal output from the control unit 80 is input to an amplifier that amplifies the signal provided in the linear motion device 64, and the amplifier output is input to a fluid control valve that controls the hydraulic pressure in the cylinder 64b. The aperture of the fluid control valve is adjusted according to the amplifier output. This causes the cylinder 64b to move, displacing the second spindle 62. The displacement of the second spindle 62 is transmitted in sequence through the ball screw 40, the first spindle housing 52, and the first spindle 50. The displacement of the first spindle 50 is transmitted to the grinding wheel S and affects the displacement of the grinding wheel S. Therefore, the transfer function K can be calculated using the vibration control signal as an input and vibration data as an output.

[0058] In this embodiment, in the preparation step, vibration data associated with the vibration control signal obtained by an experiment or the like is stored in the storage unit 82. The creation unit 85 uses the vibration data associated with the vibration control signal stored in the storage unit 82 to find a transfer function K, and stores the found transfer function K in the storage unit 82.

[0059] In the processing step, the creation unit 85 inputs data of the opposite phase of the vibration data acquired by the acquisition unit 84 into the inverse function of the transfer function K, and creates a vibration control signal using the output data. In this embodiment, the creation unit 85 uses the output data from the inverse of the transfer function K as the vibration control signal.

[0060] According to the second embodiment described above, the creation unit 85 determines the transfer function K in the preparation step. Then, in the processing step, the creation unit 85 creates a vibration control signal using data output by inputting data in the opposite phase of the acquired vibration data into the reciprocal of the transfer function K. This allows the vibration control signal to be created in the processing step using the transfer function K determined in advance, thereby eliminating the need for trial and error.

[0061] C. Third embodiment: The upper limit of the frequency of vibration that can be applied to the first spindle 50 is determined by the specifications of the linear motion device 64, etc. Therefore, there are cases where the frequency of the vibration data obtained in the first embodiment cannot be realized. Therefore, in this embodiment, if the frequency of the vibration data obtained in the first embodiment exceeds the upper limit of the frequency that can be output by the linear motion device 64, the vibration data is changed. The same configurations and processing steps as those in the above embodiments are denoted by the same reference numerals, and detailed explanations will be omitted as appropriate.

[0062] The control unit 80 of this embodiment has a graph information acquisition unit (not shown) as a functional unit. The graph information acquisition unit acquires graph information representing a graph in which the horizontal axis represents the vibration frequency of the vibration data and the vertical axis represents the period of waviness generated on the machined surface MS of the workpiece W, at a rotation speed of the workpiece spindle 20 that is the same as the machining conditions. The graph information is created by experiments or the like.

[0063] 12 is a flowchart showing the procedure of the vibration data setting process. When the machining process starts, the control unit 80 starts the vibration data setting process.

[0064] In step S40, the determination unit 86 determines whether the frequency fi of the vibration data acquired by the acquisition unit 84 is equal to or less than the upper limit frequency fa. Note that this vibration data is data in a state in which no periodic displacement is applied to the first spindle by the linear motion device 64. The upper limit frequency fa is the upper limit of the frequency of vibration that can be applied to the first spindle 50 by the linear motion device 64. The upper limit frequency fa is determined by the specifications of the linear motion device 64. The upper limit frequency fa is pre-stored in the storage unit 82. If it is determined in step S40 that the frequency fi is equal to or less than the upper limit frequency fa, the linear motion device 64 can respond to the frequency fi. Therefore, in step S42, the creation unit 85 performs the vibration control signal creation process shown in FIG. 9 and ends this processing routine.

[0065] If it is determined in step S40 that the frequency fi is not equal to or less than the upper limit frequency fa, then in step S44 the creation unit 85 uses the graph created by the graph creation unit to create waveform data having a frequency lower than the frequency fi of the vibration data.

[0066] Fig. 13 is a diagram illustrating a graph drawn from the graph information acquired by the graph information acquisition unit. Fig. 13 shows the results of simulating the waviness period of the machined surface MS when the rotation speed of the workpiece axis AW is fixed and the frequency of the vibration data is changed to various values. The graph information is obtained by experiments or the like and is stored in advance in the memory unit 82.

[0067] 8, the intersection point PI between the waveform of the disturbance and the phase indicated by the waveform of the workpiece W correlates with the amount of cutting. Here, the period of the disturbance is shorter than the rotation period of the workpiece spindle 20.

[0068] Theoretically, when the period of the disturbance and the period of the position of the workpiece W match, the amount of removal will be a constant value, and no waviness will occur on the machined surface MS. On the other hand, when the period of the disturbance and the period of the position of the workpiece W do not match, the amount of removal will change periodically. The period of this fluctuation in the amount of removal is called the waviness period.

[0069] Ideally, it would be preferable to be able to apply a displacement to the first main spindle 50 so as to cancel out the disturbance, but there are cases where the frequency of the disturbance is high and it is difficult to cancel out the disturbance. Therefore, by applying a displacement to the first main spindle 50 so as to cancel out the swell, it is possible to reduce the swell.

[0070] The horizontal axis in FIG. 13 is the frequency of the vibration data. The vertical axis in FIG. 13 is the waviness period. As shown in FIG. 13, when the rotation period of the workpiece spindle 20 is fixed, the waviness period changes periodically according to the frequency of the vibration data. In other words, there are multiple frequencies of vibration data with the same waviness period. In FIG. 13, the frequency of the vibration data at which the waviness period is maximum occurs when the rotation period of the workpiece spindle 20 matches the period of the disturbance or an integer multiple of this period. The frequency of the vibration data is also called the vibration frequency.

[0071] When the frequency fi of the vibration data is greater than the upper limit frequency fa, vibration data having the same swell period as the swell period at frequency fi and a frequency smaller than the upper limit frequency fa is set as the vibration data to create the excitation data. This makes it possible to reduce the swell.

[0072] 12, the creation unit 85 creates waveform data having the same swell period as the swell period at frequency fi and a frequency lower than the upper limit frequency fa. This waveform data is created, for example, by converting the frequency of the acquired vibration data. The created waveform data is then used as vibration data for creating excitation data.

[0073] In step S46, the creation unit 85 performs a low-frequency control signal creation process. This low-frequency control signal creation process differs from the vibration control signal creation process shown in Fig. 9 only in the content of step S12. Therefore, a detailed description of the low-frequency control signal creation process will be omitted. In step S12 of the vibration control signal creation process, first vibration data is created from the vibration data. In contrast, in step S12 of the low-frequency control signal creation process, the waveform data created in step S44 is used as vibration data to create the first vibration data.

[0074] According to the second embodiment described above, when the frequency of the vibration data is higher than the upper limit frequency fa, the creation unit 85 creates a vibration control signal using waveform data of a frequency that is lower than the upper limit frequency fa in the graph and that corresponds to the undulation period of the acquired vibration data. This makes it possible to reduce undulations occurring on the machined surface MS even when the linear motion device 64 cannot respond to the frequency of the vibration data.

[0075] D. Fourth embodiment: In the first embodiment, the vibration data is adjusted in the machining process. In the second embodiment, the vibration data is created using a transfer function K determined in advance and vibration data acquired in the machining process. In this embodiment, the vibration data is created in the machining process of a prototype before the machining process of the product. The method of creating the vibration data is the same as that shown in the first and second embodiments.

[0076] The machining method of this embodiment includes a first process and a second process. In the first process, a prototype of the product is used as the workpiece W. A vibration control signal is generated to vibrate the first spindle 50 by extending and retracting the linear motion device 64 so as to cancel out the vibration of the grinding wheel S detected by the acceleration sensor 71. In the second process, the linear motion device 64 is controlled according to the vibration control signal generated in the first process in a process for machining mass-produced products. By making the machining conditions for the prototype the same as those for the final product, the vibration control signal obtained for the prototype can be used as the vibration control signal for the final product. The machining conditions include the rotational speed of the workpiece axis AW, the rotational speed of the first spindle 50, and the swivel angle of the second spindle 62.

[0077] According to the third embodiment described above, in the production of mass-produced products, the vibration of the grindstone S can be suppressed using the vibration control signal obtained in advance.

[0078] E. Other Embodiments: (E1) In the first embodiment described above, a grinding machine 100 is exemplified as a machine tool. The machine tool to which the present disclosure is applicable is not limited to a grinding machine. For example, the present disclosure can also be applied to a sub-machine tool that uses a cutting tool as a processing tool. Furthermore, in the first embodiment described above, a grinding machine 100 that processes a workpiece W into an external gear is exemplified, but the present disclosure can also be applied to a grinding machine that processes a workpiece W into an internal gear. Regardless of the type of processing tool, the present disclosure can be applied to a machine tool that has a first spindle to which the processing tool is attached and a second spindle that rotates the first spindle.

[0079] (E2) In the first embodiment, in the vibration control signal generation process, when time θ is the horizontal axis and the amplitude of the vibration data is the vertical axis, the time θ at which the amplitude is minimum is determined as the time θ of the vibration data. As another embodiment, the minimum amplitude may be predicted from a relational expression between time θ and the vibration data, and the time θ corresponding to the predicted minimum amplitude may be determined as the time θ of the vibration data. Similarly, with regard to the magnification m, the magnification of the vibration data may be determined from a relational expression between the provisional magnification m and the vibration data.

[0080] (E3) In the first embodiment described above, the acceleration sensor 71 was exemplified as a detector for detecting vibrations of the grinding wheel S. The detector is not limited to the acceleration sensor 71, and vibrations may be detected using the current value of the first-axis rotation motor 51 or the current value of the ball screw motor 44. Furthermore, in the first embodiment, the acceleration sensor 71 is disposed inside the first spindle housing 52, but the location of the acceleration sensor 71 is not limited to this. For example, the acceleration sensor 71 may be attached to the workpiece axis AW. Furthermore, the detector is not limited to one, and multiple detectors may be used to detect vibrations of the grinding wheel S.

[0081] (E4) In the first embodiment, the vibration in the X direction has been described, but the vibration of the grinding wheel S that is suppressed is not limited to one direction. In the first embodiment, four linear motion devices 64 are provided. Therefore, by making the phases of the four vibration control signals corresponding to the four linear motion devices 64 different from each other, it is possible to apply displacement to the first spindle 50 not only in the X direction but also in the Y direction and the Z direction. Furthermore, the grinding machine 100 may be provided with only one linear motion device 64, rather than multiple linear motion devices. Even when one linear motion device 64 is provided, it is possible to apply displacement to the first spindle 50 in at least one direction. Furthermore, the configuration of the clamp 63 is not limited to the configuration shown in the first embodiment. For example, the clamp 63 may be configured to clamp the second spindle head 62a from the outer periphery of the second spindle head 62a.

[0082] (E5) In the first embodiment, the linear motion device 64 applies a displacement to the first spindle 50 in order to suppress vibrations caused by disturbances to the grinding wheel S. However, the present invention is not limited to this, and the linear motion device 64 may apply a displacement to the first spindle 50 in order to machine the machining surface MS into a desired shape.

[0083] (E6) In the second embodiment, the vibration control signal is calculated using the transfer function K. In another embodiment, the vibration control signal calculated using the transfer function K may be changed using the trial and error method shown in the first embodiment.

[0084] (E7) In each of the above embodiments, vibration data is used to generate excitation data. In another embodiment, data generated by performing frequency analysis on the vibration data may be used instead of the vibration data detected by the acceleration sensor 71. Specifically, the vibration data may contain multiple frequency components. Therefore, the frequency component with the largest amplitude among the multiple frequency components contained in the vibration data may be used to generate vibration data for generating excitation data.

[0085] (E8) In the first embodiment, one end 63a of the clamp 63 is fixed to the second main shaft support portion 61, and the other end 63b engages with the second main shaft 62. In another embodiment, one end 63a of the clamp 63 may be fixed to the second main shaft 62, and the other end 63b may engage with the second main shaft support portion 61. That is, a groove 67 for accommodating the other end 63b may be formed in the second main shaft support portion 61. In another embodiment, the second main shaft support portion 61 may have a support portion for attaching the clamp 63, the support portion having a shape that covers all or part of the outer periphery of the second shaft head 62a and sandwiches the second shaft head 62a. In this embodiment, the other end 63b of the clamp 63 engages with this support portion, and the one end 63a of the clamp 63 is fixed to the surface of the second shaft head 62a that faces the support portion. Explaining with reference to Figure 4, the support portion has a shape that faces the surface of the second axis head 62a on which the ball screw 40 is attached. In this configuration, when the linear motion device 64 extends, the clamp 63 presses the second main shaft 62 against the second main shaft support portion 61, thereby restricting the rotation of the second main shaft 62.

[0086] The present disclosure is not limited to the above-described embodiments and can be realized in various configurations without departing from the spirit thereof. For example, the technical features of the embodiments corresponding to the technical features in each aspect described in the Summary of the Invention section can be appropriately replaced or combined to solve some or all of the above-described problems or achieve some or all of the above-described effects. Furthermore, if a technical feature is not described as essential in this specification, it can be appropriately deleted. [Explanation of symbols]

[0087] 10...bed, 12...coolant pump, 20...work spindle, 21...work spindle rotation motor, 30...work spindle movement mechanism, 40...ball screw, 41...ball screw base, 42...guide rail, 43...screw shaft, 44...ball screw motor, 50...first spindle, 51...first spindle rotation motor, 52...first spindle housing, 60...second spindle movement device, 61...second spindle support portion, 62...second spindle, 62a...second spindle head, 62b...second spindle base, 63...clamp, 63a...one End, 63b...other end, 64...linear motion device, 64a...piston rod, 64b...cylinder, 64d...piston, 65...second shaft bearing, 66...second shaft rotary motor, 67...groove, 71...acceleration sensor, 80...control unit, 81...processor, 82...storage unit, 84...acquisition unit, 85...creation unit, 86...judgment unit, 87...first vibration data creation unit, 88...second vibration data creation unit, 89...first determination unit, 90...second determination unit, 91...amplitude judgment unit, 95...hydraulic drive data, 100...grinding machine

Claims

1. a work spindle on which a workpiece is attached; a first spindle to which a processing tool for processing the workpiece is attached; a second main shaft that rotates about a second axis perpendicular to the first axis of the first main shaft, and that rotates the first main shaft about the second axis; a second main shaft support portion that rotatably supports the second main shaft; at least one clamp having one end, an opposite end, and a linear motion device that extends and retracts along the second axis, the at least one clamp for limiting rotation of the second spindle; a detector for detecting vibration of the processing tool during a processing step in which the workpiece is processed by rotating the workpiece spindle and the first spindle in accordance with processing conditions; a control unit that controls the linear motion device using a control signal, the one end is fixed to either the second main shaft support portion or the second main shaft, and the other end is engaged with the other of the second main shaft support portion or the second main shaft, and the at least one clamp presses the second main shaft against the second main shaft support portion as the linear motion device extends or contracts, thereby restricting rotation of the second main shaft, The control unit an acquisition unit that acquires vibration data indicating the vibration of the processing tool detected by the detector; a creation unit that uses the acquired vibration data to create a vibration control signal that is the control signal for vibrating the first spindle by expanding and contracting the linear motion device so as to cancel out the vibration of the processing tool, The control unit controls the linear motion device in accordance with the generated vibration control signal.

2. 2. The machine tool according to claim 1, The control unit a first vibration data generating unit that generates first vibration data having a phase that is different from the phase of the vibration data by a provisional phase difference and a predetermined reference data amplitude; a second vibration data creating unit that creates second vibration data by changing the first vibration data so that the first vibration data becomes a provisional magnification of the reference data amplitude; a first determination unit that acquires amplitude of the vibration data in a state in which the linear motion device is controlled in accordance with the provisional vibration control signal created using the first vibration data by setting a first value of the provisional phase difference to a plurality of first values, and determines a phase difference between the vibration data and the vibration data for creating the vibration control signal by using the first value among the plurality of first values ​​that minimizes the amplitude of the vibration data; a second determination unit that acquires the amplitude of the vibration data in a state in which the linear motion device is controlled in accordance with the provisional vibration control signal created using the second vibration data by setting the second value of the provisional magnification to a plurality of second values, and determines the amplitude of the vibration data for creating the vibration control signal by using the second value among the plurality of second values ​​that minimizes the amplitude of the vibration data, The creation unit creates the vibration control signal using the vibration data having the phase difference determined by the first determination unit and the amplitude determined by the second determination unit.

3. 2. The machine tool according to claim 1, The creation unit, in a preparation process executed before the machining process, calculates a transfer function that uses the provisional vibration control signal as an input and the vibration data as an output, and creates the vibration control signal by inputting data of the opposite phase to the vibration data when the linear motion device is not controlled according to the vibration control signal into an inverse function of the calculated transfer function and using the output signal.

4. 4. The machine tool according to claim 1, In the machining step, the relative position of the machining tool with respect to the workpiece is changed in synchronization with the rotation period of the workpiece spindle, and machining is performed. The control unit a graph information acquiring unit that acquires graph information representing a graph in which the horizontal axis represents the vibration frequency of the vibration data and the vertical axis represents the period of waviness occurring on the machined surface of the workpiece at the same rotation speed of the workpiece spindle as the machining conditions; a determination unit that determines whether or not a frequency of the vibration data in a state in which the linear motion device is not controlled in accordance with the vibration control signal is higher than a predetermined upper limit frequency, When the determination unit determines that the frequency of the vibration data is higher than the upper limit frequency, the creation unit obtains, in the graph, the swell period corresponding to the vibration frequency, obtains, in the graph, the vibration frequency that is lower than the upper limit frequency and corresponds to the obtained swell period, and creates the vibration control signal using the vibration data of the obtained vibration frequency.

5. 4. The machine tool according to claim 1, the control unit includes an amplitude determination unit that determines whether or not the amplitude of the vibration data in a state in which the linear motion device is not controlled in accordance with the vibration control signal is greater than a predetermined reference amplitude, The creation unit creates the vibration control signal using the latest vibration data when the amplitude determination unit determines that the amplitude of the vibration data is greater than the reference amplitude.

6. 2. The machine tool according to claim 1, the at least one clamp comprises a plurality of clamps; The creation unit creates the vibration control signal for each of the plurality of clamps.

7. A method for processing mass-produced products using a machine tool, comprising: The machine tool comprises: a work spindle on which a workpiece is attached; a first spindle to which a processing tool for processing the workpiece is attached; a second main shaft that rotates about a second axis perpendicular to the first axis of the first main shaft, and that rotates the first main shaft about the second axis; a second main shaft support portion that rotatably supports the second main shaft; at least one clamp having one end, an opposite end, and a linear motion device that extends and retracts along the second axis, the at least one clamp for limiting rotation of the second spindle; a detector that detects vibration of the processing tool during a processing step in which the workpiece is processed by rotating the workpiece spindle and the first spindle in accordance with processing conditions, the one end is fixed to either the second main shaft support portion or the second main shaft, and the other end is engaged with the other of the second main shaft support portion or the second main shaft, and the at least one clamp presses the second main shaft against the second main shaft support portion as the linear motion device extends or contracts, thereby restricting rotation of the second main shaft, The processing method comprises: a first step of generating a vibration control signal for vibrating the first spindle by expanding and contracting the linear motion device so as to cancel out the vibration of the processing tool detected by the detector in the processing step using a prototype of the product as the workpiece; a second step of controlling the linear motion device in accordance with the vibration control signal generated in the first step during the processing of the mass-produced product.

Images