Machine tool and control device

Abstract

A machine tool is provided with: a main shaft to which an object to be cut (21) is attached; a rotation mechanism that rotates the main shaft; a tool holding unit that holds a tool; a movement mechanism that moves the main shaft and the tool holder relative to each other in the direction of the rotation axis of the main shaft; a vibration mechanism that vibrates the spindle and the tool holder relative to each other in a vibration direction; and a control unit that controls the rotating mechanism and the vibrating mechanism, the machine tool rotates the main shaft by the rotating mechanism and moves the object to be cut (21) and the tool by the moving mechanism and the vibrating mechanism while vibrating the object to be cut (21) relative to each other, thereby cutting the object to be cut (21). The control unit drives the rotation mechanism and the vibration mechanism such that the tool is positioned at the same position every constant rotation period of the spindle in the vibration direction, and controls the rotation mechanism and the vibration mechanism such that the outer circumferential surface or the inner circumferential surface of the object to be cut (21) is machined so as to have a substantially regular polygon shape when viewed from the direction of the rotation axis.

Description

Technical Field

[0001] The present invention relates to a machine tool and a control device for controlling the machine tool. Background Art

[0002] In so-called turning, since cutting is performed while rotating a workpiece (object to be cut) on a machine tool, the processed shape of the workpiece is restricted. Turning is mainly performed to obtain a cylindrical shape, a columnar shape, or a combination thereof.

[0003] Conventionally, in turning, a method has been proposed to process a workpiece into a shape other than a cylinder or a column by interlocking control of the movement of a tool and the rotation of the workpiece. Patent Document 1 discloses the following technique: By controlling a tool and a workpiece to change the cutting depth while moving the tool in the feed direction and synchronizing the rotation phases of the tool and the workpiece, a spiral groove shape is obtained by turning.

[0004] (Prior Art Document) (Patent Document) Patent Document 1: Japanese Patent Application Laid-Open No. 2002-36004 Summary of the Invention

[0005] (Problems to be Solved by the Invention) However, the above-mentioned technique is a technique for processing a spiral groove shape on a workpiece. For example, the above-mentioned technique cannot be used to machine a flat surface on the outer peripheral surface or the inner peripheral surface of the workpiece.

[0006] An object of the present invention is to efficiently machine an object to be cut into a substantially regular polygon by turning.

[0007] (Measures for Solving the Problems) (Mode 1) To solve the above problems, the machine tool according to the first aspect of the present invention includes: a spindle on which an object to be cut is mounted; a rotation mechanism that rotates the spindle; a tool holding portion that holds a tool for cutting the object to be cut; a moving mechanism that relatively moves the spindle and the tool holding portion in the axial direction of rotation of the spindle; a vibration mechanism that relatively vibrates the spindle and the tool holding portion in a vibration direction orthogonal to the axial direction of rotation; and a control portion that controls the rotation mechanism and the vibration mechanism, and while rotating the spindle by the rotation mechanism, relatively vibrates and moves the object to be cut and the tool by the moving mechanism and the vibration mechanism, thereby cutting the object to be cut. Wherein, the control portion drives the rotation mechanism and the vibration mechanism so that the tool is located at the same position every constant rotation period of the spindle in the vibration direction, and the control portion controls the rotation mechanism and the vibration mechanism to process the outer peripheral surface or the inner peripheral surface of the object to be cut into a substantially regular polygon when viewed from the axial direction of rotation.

[0008] (Second aspect) In the above first aspect, the control portion may set the number of vibrations of the vibration mechanism each time the spindle rotates one circle according to the number of sides of the regular polygon.

[0009] (Third aspect) In the above second aspect, when the constant rotation period is set to m circles and the number of sides of the regular polygon is set to n sides, m is a natural number of 1 or more, n is a natural number of 3 or more, and m and n are relatively prime to each other, the control portion may set the number of vibrations of the vibration mechanism to n / m.

[0010] (Fourth aspect) In any one of the above first to third aspects, when the tool is located at the amplitude upper limit of the vibration waveform of the tool generated by the vibration mechanism, the tool has a larger cutting depth into the object to be cut than when the tool is located at the amplitude lower limit of the vibration waveform. The control portion may synchronously control the moving mechanism and the vibration mechanism so that when cutting the outer peripheral surface of the object to be cut, the center of the side of the regular polygon is machined when the tool is located at the amplitude upper limit of the vibration waveform.

[0011] (Fifth aspect) In any one of the above-described Modes 1 to 4, when the tool is at the upper limit of the amplitude of the vibration waveform of the tool generated by the vibration mechanism, the penetration amount of the tool into the cutting object is larger than when the tool is at the lower limit of the amplitude of the vibration waveform. The control unit can synchronously control the moving mechanism and the vibration mechanism so that when cutting the inner peripheral surface of the cutting object, the vertices of the regular polygon are machined when the tool is at the upper limit of the amplitude of the vibration waveform.

[0012] (Mode 6) In any one of the above-described Modes 1 to 5, the moving mechanism can be configured to relatively move the main shaft and the tool holder in a direction parallel to the vibration direction.

[0013] (Mode 7) In the above-described Mode 6, the control unit can control the operation of the moving mechanism. When performing a first machining to obtain a machining surface that is substantially a regular polygon when viewed from the direction of the rotation axis and a second machining to machine the machining surface into a shape similar to the machining surface when viewed from the direction of the rotation axis, the control unit can control the rotation mechanism, the moving mechanism, and the vibration mechanism so that the phase of the vibration waveform of the tool generated by the vibration mechanism with respect to the rotation of the main shaft in the second machining is the same as that in the first machining.

[0014] (Mode 8) To solve the above problems, a control device according to Mode 8 of the present invention is for controlling a machine tool. The machine tool includes: a main shaft on which a cutting object is mounted; a rotation mechanism that rotates the main shaft; a tool holder that holds a tool for cutting the cutting object; a moving mechanism that relatively moves the main shaft and the tool holder in the rotation axis direction of the main shaft; and a vibration mechanism that relatively vibrates the main shaft and the tool holder in a vibration direction orthogonal to the rotation axis direction. While the machine tool rotates the main shaft through the rotation mechanism, the cutting object and the tool are relatively vibrated and moved through the moving mechanism and the vibration mechanism, whereby an outer peripheral surface or an inner peripheral surface of the cutting object is machined into a substantially regular polygon when viewed from the direction of the rotation axis. Among them, the control device drives the rotation mechanism and the vibration mechanism so that the tool is located at the same position every constant rotation period of the main shaft in the vibration direction.

[0015] (Effect of the Invention) According to the present invention, it is possible to efficiently machine a cutting object into a substantially regular polygon by turning. Description of the Drawings

[0016] Figure 1 It is a schematic structural diagram of a machine tool related to an embodiment of the present invention.

[0017] Figure 2 It is a view showing a workpiece machined into a polygon by outer diameter machining.

[0018] Figure 3 It is a front view showing the state of outer diameter machining related to the embodiment.

[0019] Figure 4 It is a perspective view showing the state of outer diameter machining related to the embodiment.

[0020] Figure 5 It is a top view and a side view showing the state of outer diameter machining related to the embodiment.

[0021] Figure 6 It is a view showing the machining trajectories of each path of outer diameter machining related to the embodiment.

[0022] Figure 7 It is a view showing the relationship between the workpiece rotation phase and the tool position related to the embodiment.

[0023] Figure 8 It is a view showing a workpiece machined into a polygon by inner diameter machining.

[0024] Figure 9 It is a front view showing the state of inner diameter machining related to the embodiment.

[0025] Figure 10 It is a perspective view showing the state of inner diameter machining related to the embodiment.

[0026] Figure 11 It is a view showing the state of inner diameter machining related to the embodiment.

[0027] Figure 12 It is a view showing the machining trajectories of each path of inner diameter machining related to the embodiment.

[0028] Figure 13 It is a view showing other examples of machining a workpiece into a polygon related to the embodiment. Detailed Embodiment

[0029] Hereinafter, based on the embodiment, a mode for implementing the present invention will be exemplarily described in detail with reference to the drawings. In addition, the dimensions, materials, shapes, and relative configurations of the structural components described in this embodiment should be appropriately changed according to the structure of the device to which the invention is applied and various conditions. That is, the scope of the present invention is not limited to the following embodiments.

[0030] The present invention is preferably used in a machine tool that processes a workpiece to be cut into a polygon using a tool while rotating the workpiece to be cut. In addition, the present invention can also be considered as a control device for controlling the machine tool. Embodiment

[0031] (Machine tool 10) First, the schematic structure of the machine tool 10 according to the embodiment of the present invention will be described. Figure 1 It is a schematic diagram showing the schematic structure of the machine tool 10 according to the embodiment. The machine tool 10 has a workpiece holding portion 11 that holds a workpiece 21 to be cut so as to be rotatable, a tool holding portion 13 that holds a tool for cutting the workpiece 21, and a control portion 15 that controls the operations of the workpiece holding portion 11 and the tool holding portion 13. In addition, for ease of explanation, the X-axis, Y-axis, and Z-axis orthogonal to each other are shown in the figure as needed. The X-axis and Z-axis face the horizontal direction, and the Y-axis faces the vertical direction. In addition, in the present embodiment, the rotation axis direction S1 of the workpiece 21 held by the tool holding portion 13 is the Z-axis direction.

[0032] The workpiece holding portion 11 holds the workpiece 21 so as to be rotatable in the rotation direction R1 and movable in the rotation axis direction S1 of the workpiece 21. The tool holding portion 13 holds the tool so as to be movable in a first direction S2 parallel to the rotation axis direction S1 and a second direction S3 orthogonal to the first direction S2. The rotation axis direction S1 and the first direction S2 are parallel to the Z-axis direction, and the second direction S3 is parallel to the X-axis direction. In addition, the tool holding portion 13 is configured to be able to hold a plurality of tools. Figure 1 shows a state in which the tool holding portion 13 holds a tool 31 for outer diameter machining and a tool 33 for inner diameter machining.

[0033] The machine tool 10 has a rotation mechanism that rotates the workpiece 21 by the workpiece holding portion 11, and a movement mechanism that relatively moves the workpiece 21 and the tool in parallel by the workpiece holding portion 11 and the tool holding portion 13. As the rotation mechanism, various known techniques such as various motors can be used, and as the movement mechanism, known techniques such as a linear servo motor, a ball screw mechanism, and a rack and pinion mechanism can be used.

[0034] In addition, the machine tool 10 also has a vibration mechanism that relatively vibrates the workpiece 21 and the tool in a direction parallel to the movement direction of the movement mechanism. In the present embodiment, the tool holding portion 13 holds the tool so as to be vibratable in a vibration direction V1 parallel to the X-axis direction. As the vibration mechanism, various known techniques capable of reciprocatingly vibrating the object to be vibrated can be used.

[0035] The control unit 15 is a control device configured to control the actions of the above-mentioned rotating mechanism, moving mechanism, and vibration mechanism. The control unit 15 can control various mechanisms in a linked manner, for example, it can control the workpiece holding unit 11 and the tool holding unit 13 so that the rotation phase of the workpiece 21 is synchronized with the movement of the tool in the feed direction and the cutting direction to perform turning processing.

[0036] In addition, in the present embodiment, a structure is shown in which the workpiece 21 is held so as to be movable in one direction, and the tool is held so as to be movable in two directions and vibrate in one direction. However, when the present invention is applied, the machine tool 10 may also be configured to hold the workpiece 21, rather than the tool, so as to be movable in two directions and vibrate in one direction. Alternatively, the machine tool 10 may also be configured to hold only the tool so as to be movable. More specifically, the machine tool 10 is configured so that the workpiece 21 and the tool can move relative to each other in the Z-axis direction and the X-axis direction and can vibrate relative to each other in the X-axis direction. Through this structure, the machine tool 10 can control the rotating mechanism and the vibrating mechanism in linkage, and process the outer circumference and inner circumference of the workpiece 21 into a roughly regular polygon when viewed from the direction of the rotation axis of the workpiece 21. Below, based on multiple processing examples, a method of vibrating the tool 31 in synchronization with the rotation phase of the workpiece 21 and cutting at the same time to process the workpiece 21 into a roughly regular polygon is described.

[0037] (Processing example 1) First, as a first machining example, a case where the outer peripheral surface of the workpiece 21 is machined into a substantially regular pentagon by cutting while vibrating the tool 31 in synchronization with the rotation phase of the workpiece 21 using the machine tool 10 will be described. Figure 2 (a) is a diagram showing a state in which the outer peripheral surface of the workpiece 21 is processed into a regular pentagon when viewed from the Z-axis direction, and shows a state in which the outer diameter processing tool 31 is in contact with the outer peripheral surface of the workpiece 21 . Figure 2 (b) is a perspective view of the workpiece 21 after the outer peripheral surface is processed when viewed from the Z-axis direction. The workpiece 21 is held by the claws 17 of the main spindle constituting the workpiece holding portion 11, and rotates integrally with the main spindle.

[0038] A method for machining the outer peripheral surface of the workpiece 21 into a regular pentagon by setting the number of vibrations of the tool 31 to 2.5 times per one rotation of the workpiece 21 is described. In the following description, the number of vibrations of the tool refers to the number of vibrations per one rotation of the workpiece 21. That is, when the number of vibrations is 2.5 times, the tool 31 vibrates 5 times when the workpiece 21 rotates two times.

[0039] use Figure 3 (a) to (c) Figure 4 , Figure 5Figures (a) and (b) are used to illustrate the state of the outer diameter machining with 2.5 vibration cycles. In Machining Example 1, while the machine tool 10 rotates the workpiece 21, the tool 31 is moved in the Z-axis direction (feed direction) and vibrates in the X-axis direction (cutting-in direction) to perform cutting. In addition, in Machining Example 1, the tool 31 vibrates in a sine wave through a vibration mechanism, and the workpiece 21 rotates counterclockwise in Figure 2 Figure (a).

[0040] Figure 3 Figures (a) to (c) are front views showing the state of the outer diameter machining performed by the machine tool 10, and the machining trajectory To is represented by a solid line. The machining trajectory To represents the position where the tip of the tool 31 in the cutting-in direction abuts against the workpiece 21, and the outer peripheral surface of the workpiece 21 is machined according to the machining trajectory To. In addition, in Figure 3 Figures (a) to (c), the amplitude upper limit AU, amplitude middle AM, and amplitude lower limit AL of the tool 31 are represented by a double-dashed line. The cutting-in amount of the tool 31 into the workpiece 21 in the X-axis direction is the largest when the tool 31 is at the amplitude upper limit AU and the smallest when the tool 31 is at the amplitude lower limit AL. Since the tool 31 abuts against the outer peripheral surface of the workpiece 21, the diameter of the circle representing the amplitude lower limit AL is the largest, and the diameter of the circle representing the amplitude upper limit AU is the smallest. In addition, in each figure showing the machining trajectory as in Figures 3(a) to (c), the machining trajectory is magnified in the vibration direction V1 of the tool, the feed direction, etc. to clearly show the vibration state of the tool.

[0041] Figure 3 Figure (a) is a front view showing the machining trajectory To of the first rotation of the workpiece 21 as viewed from the Z-axis direction. As described above, the tool 31 vibrates 2.5 times during one rotation of the workpiece 21. In Figure 3 Figure (a), the starting point of the first vibration of the tool 31 is denoted as point Po1, the end point of the first vibration of the tool 31, which is also the starting point of the second vibration of the tool 31, is denoted as point Po2, and the end point of the second vibration of the tool 31, which is also the starting point of the third vibration of the tool 31, is denoted as point Po3. Further, in Figure 3 Figure (a), the midpoint of the third vibration of the tool 31, that is, the position when the tool 31 makes 2.5 vibrations, is denoted as point Po3.5.

[0042] In this machining, the lower amplitude limit AL is set to be consistent with the outer peripheral surface of the workpiece 21 before machining. The tool 31 is located at the point Po1 and starts to contact the workpiece 21 at the lower amplitude limit AL. Then, when the workpiece 21 rotates 2 / 5 of a turn, the tool 31 vibrates once and moves to the point Po2, and contacts the workpiece 21 again at the lower amplitude limit AL. When the workpiece 21 rotates another 2 / 5 of a turn from here, the tool 31 vibrates once again and moves to the point Po3, and contacts the workpiece 21 at the lower amplitude limit AL. When the workpiece 21 rotates another 1 / 5 of a turn from here, the tool vibrates 1 / 2 time and moves to the point Po3.5, and contacts the workpiece 21 at the upper amplitude limit AU. In Figure 3 In (a) therein, the processed area Qo1 during the second rotation of the workpiece 21 is coated with diagonal lines.

[0043] Figure 3 (b) therein is a front view showing the machining trajectory To of the second rotation of the workpiece 21 when viewed from the Z-axis direction. In Figure 3 In (b) therein, the end point of the third vibration of the tool 31, which is also the starting point of the fourth vibration, is denoted as the point Po4, the end point of the fourth vibration of the tool 31, which is also the starting point of the fifth vibration of the tool 31, is denoted as the point Po5, and the end point of the fifth vibration of the tool 31, which is also the starting point of the sixth vibration of the tool 31, is denoted as the point Po6. Further, in Figure 3 In (b) therein, the midpoint of the third vibration of the tool 31, which is also the position of the tool 31 at the start of the second rotation of the workpiece 21, is denoted as the point Po3.5.

[0044] As described above, at the start of the second rotation of the workpiece 21, the tool 31 is located at the point Po3.5. By rotating the workpiece 21 1 / 5 of a turn from here, the tool 31 is moved to the point Po4 and contacts the workpiece 21 at the lower amplitude limit AL. Then, when the workpiece 21 rotates 2 / 5 of a turn, the tool 31 vibrates once and moves to the point Po5, and contacts the workpiece 21 again at the lower amplitude limit AL. When the workpiece 21 rotates 2 / 5 of a turn from here, the tool 31 vibrates once again and moves to the point Po6, and contacts the workpiece 21 at the lower amplitude limit AL. In Figure 3 In (b) therein, the processed area Qo2 during the second rotation of the workpiece 21 is coated with dots.

[0045] The above machining is sequentially repeated for the third rotation and subsequent rotations of the workpiece 21. That is, the odd-numbered rotations of the workpiece 21 are machined along the machining trajectory To shown in Figure 3 (a) therein, and the even-numbered rotations of the workpiece 21 are machined along Figure 3Machining is performed along the machining locus To shown in (b) therein. In addition, the control unit 15 drives the rotation mechanism and the vibration mechanism so that the tool 31 is located at the same position in the vibration direction V1 every constant rotation period of the spindle of the workpiece holding portion 11 that holds the workpiece 21. More specifically, when the workpiece 21 rotates by s (s: 0, 1, 2,...) × 144°, the tool 31 is located at the amplitude lower limit AL, and when the workpiece 21 rotates by t (t: 0, 1, 2,...) × 144° + 72°, the tool 31 is located at the amplitude upper limit AU. By continuously performing such machining in the rotation axis direction S1 (Z-axis direction) of the workpiece 21, the outer peripheral surface of the workpiece 21 is machined into a substantially regular pentagon as viewed from the rotation axis direction S1.

[0046] Figure 3 (c) therein is a diagram showing a state in which the machining loci To of the first rotation and the second rotation of the workpiece 21 are overlapped. In Figure 3 (c) therein, only the portion with a large cutting amount of the tool 31 with respect to the workpiece 21 in the overlapping part of the machining locus To of the first rotation of the workpiece 21 and the machining locus To of the second rotation of the workpiece 21 is shown. As Figure 3 (c) therein shows, it can be seen that the overlapping machining locus To is formed into a substantially regular pentagon, and the workpiece 21 is machined into a substantially regular pentagon by the above machining. As described above, Figure 3 (a) to (c) therein are diagrams in which a part is magnified and shown in the vibration direction V1 of the tool 31. In actual machining, the workpiece 21 is machined into a shape closer to a regular pentagon than the Figure 3 shape shown in (c) therein.

[0047] As Figure 3 (c) therein shows, in machining example one, each vertex of the regular pentagon of the workpiece 21 is machined when the tool 31 is located at the amplitude middle AM, and the center of each side of the regular pentagon of the workpiece 21 is machined when the tool 31 is located at the amplitude upper limit AU. That is, the circle representing the amplitude upper limit AU of the tool 31 is inscribed in the regular pentagon of the workpiece 21. The control unit 15 controls the rotation mechanism and the moving mechanism so that the workpiece 21 is cut by the tool 31 in accordance with such a positional relationship.

[0048] Figure 4 is a perspective view showing the machining locus To and the points Po1 to Po6 when the workpiece 21 rotates two turns. During machining, the tool 31 always moves in the Z-axis direction at a feed amount F per turn of rotation. That is, the distance in the Z-axis direction between the point Po1 and the point Po6 is 2F.

[0049] Figure 5 (a) therein is a top view as viewed from the Y-axis direction showing the machining locus To when the machining is further continued from the Figure 4 state and the tool 31 moves in the feed direction (Z-axis direction).Figure 5 In (b), it is viewed from the X-axis direction Figure 5 and is a side view of (a) in Figure 5 . In the first machining example, since the number of vibrations is 2.5, every time the workpiece 21 rotates two turns, the tool 31 is located at the same position in the vibration direction V1. That is, at the point Po1 where the workpiece 21 rotates in the first turn and the point Po1 where the workpiece 21 rotates in the third turn, the tool 31 is located at the same position in the vibration direction V1.

[0050] As described above, in Figure 4 , Figure 5 in (a) and (b), the machining locus To is shown magnified in the Z-axis direction. In actual machining, the feed rate F is set such that the portions of the workpiece 21 machined during odd-numbered turns and the portions of the workpiece 21 machined during even-numbered turns overlap partially in the Z-axis direction, and machining is performed. Then, the outer peripheral surface of the workpiece 21 is machined into a substantially regular pentagon.

[0051] The machine tool 10 can perform the machining of the above workpiece 21 by dividing it into multiple machining paths in the cutting-in direction. Figure 6 is a diagram showing the machining locus when machining the workpiece 21 in three paths. In Figure 6 , respectively, the outer peripheral surface 21a of the workpiece 21 before machining is indicated by a dashed line, the machining locus To1 of the first path (first machining) is indicated by a single-dot chain line, the machining locus To2 of the second path (second machining) is indicated by a double-dot chain line, and the machining locus To3 of the third path (third machining) is indicated by a solid line. In the first machining example, the machining locus To1 is depicted as contacting the outer peripheral surface 21a of the workpiece 21. Further, in Figure 6 , respectively, the region Qp1 machined in the first path is coated with oblique lines, the region Qp2 machined in the second path is coated with horizontal lines, and the region Qp3 machined in the third path is coated with vertical lines.

[0052] The control unit 15 can move the tool 31 in synchronization with the rotational phase of the workpiece 21, so that the rotational phases of the workpiece 21 when the tool 31 starts to contact the workpiece 21 are the same in multiple machining paths. In addition, by cutting the workpiece 21 with the same number of vibrations and feed rate, the phases of the vibration waveforms of the tool 31 are the same in multiple machining paths, and the positions of the vertices of the regular pentagon with respect to the rotational phase of the workpiece 21 are the same.

[0053] As Figure 6As shown, the machining trajectory To1, the machining trajectory To2, and the machining trajectory To3 are all roughly regular pentagons, and are similar in shape to each other. That is, when the workpiece 21 is observed from the Z-axis direction, a machining surface roughly in the shape of a regular pentagon is obtained in each path. That is, according to this embodiment, since the workpiece 21 can be machined into a roughly regular polygon by dividing into a plurality of machining paths, there is no need to excessively reduce the machining allowance of the workpiece 21, and the machining can be performed simply, without pre-processing, and efficiently.

[0054] Figure 7 Graph showing the relationship between the rotation phase of the workpiece 21 and the cutting direction position of the tool 31. Figure 7 In the graph, the vertical axis is the position of the cutting direction of the tool 31, and the horizontal axis is the rotation phase of the workpiece 21, and the cutting direction position of the tool 31 for the odd-numbered rotations and the even-numbered rotations of the workpiece 21 from the first path to the third path is shown. Figure 7 In FIG. 1 , the vibration waveforms L11, L12, and L13 are indicated by dotted lines, and the vibration waveforms L11, L12, and L13 indicate the cutting direction position of the tool 31 when the workpiece of the first, second, and third paths rotates by odd number of revolutions. Figure 7 In FIG. 1 , vibration waveforms L21 , L22 , and L23 are indicated by single-dot chain lines, and the vibration waveforms L21 , L22 , and L23 indicate the cutting direction positions of the tool 31 when the workpiece of the first, second, and third paths rotates by even-numbered turns.

[0055] like Figure 7 As shown, the control unit 15 drives the rotating mechanism, the vibrating mechanism, and the moving mechanism in a linked manner to make the phases of the vibration waveforms of the tool 31 consistent in multiple processing paths. In the first processing example, the phases of the vibration waveforms L11, L12, and L13 relative to the rotation phase of the workpiece 21 are consistent with each other, and the phases of the vibration waveforms L21, L22, and L23 relative to the rotation phase of the workpiece 21 are consistent with each other. By controlling each mechanism as described above, the workpiece 21 is processed into a substantially regular polygon in multiple paths.

[0056] In the first machining example, the cutting amount Xs of the tool 31 into the workpiece 21 in the X-axis direction and the vibration amplitude Xt (the difference between the amplitude upper limit AU and the amplitude lower limit AL) of the tool 31 are set to the same value. Alternatively, these values may be set to different values.

[0057] As described above, in the machine tool 10 according to the present embodiment, by synchronously controlling the rotation mechanism and the vibration mechanism, the outer peripheral surface of the workpiece can be machined into a substantially regular polygon by turning. In addition, as a method of machining the workpiece into a polygon, polygon machining in which the tool and the workpiece are rotated about parallel rotation axes can be cited. However, the machining method of the present embodiment can perform machining with higher efficiency compared to this polygon machining. Further, this polygon machining is interrupted cutting, while the machining method of the present embodiment can machine the workpiece into a substantially regular polygon by continuous cutting, so that cutting can be stably performed.

[0058] (Machining Example 2) Next, a case where the inner peripheral surface of the workpiece 21 is machined into a substantially regular pentagon by vibrating the tool 33 in synchronization with the rotation phase of the workpiece 21 and performing cutting using the machine tool 10 will be described as Machining Example 2. Figure 8 In (a) is a view showing a state in which the inner peripheral surface of the workpiece 21 is machined into a regular pentagon when viewed from the Z-axis direction, showing a state in which the tool 33 for inner diameter machining is in contact with the inner peripheral surface of the workpiece 21. Figure 8 In (b) is a perspective view of the workpiece 21 after machining the inner peripheral surface when viewed from the Z-axis direction. The workpiece 21 is held by the claw portion 17 and rotates integrally with the main shaft of the workpiece holding portion 11.

[0059] When machining the inner peripheral surface of the workpiece 21 into a regular polygon, it is performed in a state where a bottom hole 21b is previously formed in the workpiece 21. The diameter of the bottom hole 21b can be changed according to the machining allowance for the final shape and the tool 33 for inner diameter machining used.

[0060] Use Figure 9 in (a) to (c), Figure 10 , Figure 11 in (a) and (b) to describe a method of machining the inner peripheral surface of the workpiece 21 into a regular pentagon by setting the number of vibrations of the tool 31 per rotation of the workpiece 21 to 2.5 times. In Machining Example 2, the machine tool 10 also moves the tool 31 in the Z-axis direction (feed direction) and vibrates in the X-axis direction (cutting-in direction) while rotating the workpiece 21 to perform cutting. Further, in Machining Example 2, the tool 33 also vibrates in a sine wave by the vibration mechanism, and the workpiece 21 rotates counterclockwise in (a) of Figure 8 .

[0061] Figure 9Among (a) to (c) are front views showing the state of the inner diameter machining performed by the machine tool 10, and the machining locus Ti is represented by a solid line. The machining locus Ti represents the position where the tip of the cutting direction of the tool 33 comes into contact with the workpiece 21, and the inner peripheral surface of the workpiece 21 is machined according to the machining locus Ti. Further, in Figure 9 Among (a) to (c), the amplitude upper limit AU, the amplitude middle AM, and the amplitude lower limit AL of the tool 33 are represented by a double-dot chain line. Since the tool 33 comes into contact with the inner peripheral surface of the workpiece 21, the diameter of the circle representing the amplitude upper limit AU is the largest, and the diameter of the circle representing the amplitude lower limit AL is the smallest.

[0062] Figure 9 Among (a) is a front view of the machining locus Ti of the first rotation of the workpiece 21 when viewed from the Z-axis direction. As described above, during one rotation of the workpiece 21, the tool 33 vibrates 2.5 times. In Figure 9 Among (a), the starting point of the first vibration of the tool 31 is represented as point Pi1, the end point of the first vibration of the tool 31, which is also the starting point of the second vibration of the tool 33, is represented as point Pi2, and the end point of the second vibration of the tool 33, which is also the starting point of the third vibration of the tool 33, is represented as point Pi3. Further, in Figure 9 Among (a), the midpoint of the third vibration of the tool 33, which is the position when the tool 33 vibrates 2.5 times, is represented as point Pi3.5.

[0063] In this machining, the amplitude lower limit AL is set to be consistent with the inner peripheral surface (bottom hole 21b) of the workpiece 21 before machining. The tool 33 is located at point Pi1 and starts to come into contact with the workpiece 21 at the amplitude lower limit AL. Then, when the workpiece 21 rotates 2 / 5 of a turn, the tool 33 vibrates once and moves to point Pi2, and comes into contact with the workpiece 21 again at the amplitude lower limit AL. When the workpiece 21 rotates another 2 / 5 of a turn from here, the tool 33 vibrates once again and moves to point Pi3, and comes into contact with the workpiece 21 at the amplitude lower limit AL. When the workpiece 21 rotates another 1 / 5 of a turn from here, the tool vibrates 1 / 2 time and moves to point Pi3.5, and comes into contact with the workpiece 21 at the amplitude upper limit AU. In Figure 9 Among (a), the region Qi1 machined during the second rotation of the workpiece 21 is coated with oblique lines.

[0064] Figure 9 Among (b) is a front view showing the machining locus Ti of the second rotation of the workpiece 21 when viewed from the Z-axis direction. In Figure 9 Among (b), the end point of the third vibration of the tool 33, which is also the starting point of the fourth vibration, is represented as point Pi4, the end point of the fourth vibration of the tool 33, which is also the starting point of the fifth vibration of the tool 33, is represented as point Pi5, and the end point of the fifth vibration of the tool 33, which is also the starting point of the sixth vibration of the tool 33, is represented as point Pi6. Further, inFigure 9 In (b) thereof, the position of the tool 33 at the midpoint of the third vibration of the tool 33, i.e., the position of the tool 33 at the start of the second revolution of the workpiece 21, is denoted as the point Pi3.5.

[0065] As described above, when the workpiece 21 starts the second revolution, the tool 33 is located at the point Pi3.5. The workpiece 21 rotates 1 / 5 of a revolution from here to move the tool 33 to the point Pi4, and the tool 33 abuts against the workpiece 21 at the lower amplitude limit AL. Then, when the workpiece 21 rotates 2 / 5 of a revolution, the tool 33 vibrates once and moves to the point Pi5, and again abuts against the workpiece 21 at the lower amplitude limit AL. When the workpiece 21 rotates 2 / 5 of a revolution from here, the tool 33 vibrates once again and moves to the point Pi6, and abuts against the workpiece 21 at the lower amplitude limit AL. In Figure 9 In (b) thereof, the area Qi2 to be machined during the second revolution of the workpiece 21 is coated using points.

[0066] The above-described machining is sequentially repeated for the third revolution and subsequent revolutions of the workpiece 21. That is, the odd-numbered revolutions of the workpiece 21 are machined along the machining trajectory Ti shown in Figure 9 In (a) thereof, and the even-numbered revolutions of the workpiece 21 are machined along the machining trajectory Ti shown in Figure 9 In (b) thereof. In addition, the control unit 15 drives the rotation mechanism and the vibration mechanism so that the tool 33 is located at the same position in the vibration direction V1 every constant rotation period of the spindle of the workpiece holding unit 11 that holds the workpiece 21. More specifically, when the workpiece 21 rotates u (u: 0, 1, 2,...) × 144°, the tool 33 is located at the lower amplitude limit AL, and when the workpiece 21 rotates v (v: 0, 1, 2,...) × 144 + 72°, the tool 33 is located at the upper amplitude limit AU. By continuously performing such machining in the rotation axis direction S1 (Z-axis direction) of the workpiece 21, the inner peripheral surface of the workpiece 21 is machined into a substantially regular pentagon as viewed from the rotation axis direction S1 of the workpiece 21.

[0067] Figure 9 In (c) thereof is a view showing a state in which the machining trajectories Ti of the first revolution and the second revolution of the workpiece 21 are overlapped. In Figure 9 In (c) thereof, only the portion with a large cutting amount of the tool 33 with respect to the workpiece 21 in the overlapping portion of the machining trajectory Ti of the first revolution of the workpiece 21 and the machining trajectory Ti of the second revolution of the workpiece 21 is shown. As Figure 9 shown in (c) thereof, it can be seen that the overlapping machining trajectory is formed into a substantially regular pentagon, and the workpiece 21 is machined into a substantially regular pentagon by the above-described machining. As described above, Figure 9 In (a) to (c) thereof are views showing a part enlarged in the vibration direction V1 of the tool 33. In actual machining, the workpiece 21 is machined into a shape larger than Figure 9The shape shown in (c) is closer to a regular pentagon.

[0068] As Figure 9 shown in (c) in, in the second machining example, each vertex of the regular pentagon of the workpiece 21 is machined when the tool 31 is at the amplitude upper limit AU, and the center of each side of the regular pentagon of the workpiece 21 is machined when the tool 31 is at the amplitude middle AM. That is, the circle representing the amplitude middle AM of the tool 31 is inscribed in the regular pentagon of the workpiece 21. The control unit 15 controls the rotation mechanism and the movement mechanism so that the workpiece 21 is cut by the tool 33 in accordance with this positional relationship.

[0069] Figure 10 is a three-dimensional view showing the machining trajectory Ti and the points Pi1 to Pi6 when the workpiece 21 rotates two turns. During machining, the tool 33 always moves in the Z-axis direction at a feed per turn F. That is, the distance in the Z-axis direction between the point Pi1 and the point Pi6 is 2F.

[0070] Figure 11 In (a) in, it is a top view when observing from the Y-axis direction, showing the machining trajectory Ti when the tool 33 is further machined from the state of Figure 10 and moves in the feed direction (Z-axis direction). Figure 11 In (b) in, it is a side view when observing Figure 11 in (a) from the X-axis direction. In the second machining example, since the number of vibrations is 2.5, every time the workpiece 21 rotates two turns, the tool 33 is in the same position in the vibration direction V1. That is, between the point Pi1 when the workpiece 21 rotates the first turn and the point Pi1 when the workpiece 21 rotates the third turn, the tool 33 is in the same position in the vibration direction V1.

[0071] As described above, in Figure 10 , Figure 11 in (a) and (b), the machining trajectory Ti is enlarged and shown in the Z-axis direction. In actual machining, the feed amount F is set so that the machined part of the workpiece 21 during the odd-numbered turns of rotation and the machined part of the workpiece 21 during the even-numbered turns of rotation partially overlap in the Z-axis direction for machining. Then, the inner peripheral surface of the workpiece 21 is machined into a substantially regular pentagon.

[0072] The machine tool 10 can perform the machining of the above workpiece 21 by dividing it into multiple machining paths in the cutting-in direction. Figure 12 is a view showing the machining trajectory when machining the workpiece 21 in three paths. In Figure 12Among them, respectively, the machining locus Ti1 of the first path (first machining) is represented by a single-dot dash line, the machining locus Ti2 of the second path (second machining) is represented by a double-dot dash line, and the machining locus Ti3 of the third path (third machining) is represented by a solid line. In the second machining example, the machining locus Ti1 is depicted as being in contact with the inner peripheral surface of the workpiece 21, i.e., the bottom hole 21b. Further, in Figure 6 Among them, respectively, the region Qp1 machined in the first path is coated with oblique lines, the region Qp2 machined in the second path is coated with horizontal lines, and the region Qp3 machined in the third path is coated with vertical lines.

[0073] In the second machining example as well, the control unit 15 can move the tool 33 in synchronization with the rotation phase of the workpiece 21 so that the rotation phases of the workpiece 21 when the tool 33 starts to contact the workpiece 21 are the same in multiple machining paths. In addition, by cutting the workpiece 21 with the same number of vibrations and feed rate, the phases of the vibration waveforms of the tool 33 are the same in multiple machining paths, and the positions of the vertices of the regular pentagon with respect to the rotation phase of the workpiece 21 are the same.

[0074] As Figure 12 shown, the machining locus Ti1, the machining locus Ti2, and the machining locus Ti3 are all approximately regular pentagons and are similar shapes to each other. That is, when observing the workpiece 21 from the Z-axis direction, a machined surface in an approximately regular pentagon shape is obtained in each path. That is, according to the present embodiment, since the workpiece 21 can be machined into an approximately regular polygon by dividing it into multiple machining paths, it is not necessary to excessively reduce the machining allowance of the workpiece 21, and the machining of a regular polygon can be simply performed.

[0075] As described above, according to the machine tool 10 of the present embodiment, by interlocking and controlling the rotation mechanism and the vibration mechanism, the inner peripheral surface of the workpiece can be machined into an approximately regular polygon by turning. In addition, according to the machining method of the present embodiment, by appropriately setting the vibration amplitude and the cutting depth, the workpiece is machined into an approximately regular polygon by continuous cutting, so that stable cutting can be performed.

[0076] In summary, according to the present embodiment, the outer peripheral surface and the inner peripheral surface of the workpiece can be efficiently machined into an approximately regular polygon by turning. In addition, in the above machining example, the workpiece is machined into an approximately regular pentagon with a vibration number of 2.5 as the cutting condition, but the present invention can also set the vibration number to different values to machine other regular polygons. Hereinafter, a machining example in which the vibration number in the above machining example is changed and the workpiece 21 is machined into other regular polygons using the structure of the first embodiment will be described.

[0077] (Other machining examples) Next, use Figure 13Examples of other machining operations according to this embodiment will be described with reference to (a) to (f) below. Hereinafter, in the examples of other machining operations to be described, similarly, while rotating the workpiece 21, the machine tool 10 moves the tool in the Z-axis direction (feed direction) and vibrates in the X-axis direction (cutting-in direction) to perform cutting, and the workpiece 21 is machined into a substantially regular polygon. In Figure 13 In (a) to (f), the upper amplitude limit AU, the middle amplitude AM, and the lower amplitude limit AL of the tool are indicated by a two-dot chain line.

[0078] In the examples showing machining operations for outer diameter machining shown in Figure 13 In (a), (c), and (e), the starting point of the q-th vibration of the tool is denoted as point Poq, and the machining trajectory To is represented by a solid line. Further, in Figure 13 In (a), (c), and (e), the region Qo1 machined by the machining trajectory To of the first rotation of the workpiece 21 is coated with slashes, and the region Qo2 machined by the machining trajectory To of the second rotation of the workpiece 21 is coated with dots.

[0079] In the examples showing machining operations for inner diameter machining shown in Figure 13 In (b), (d), and (f), the starting point of the q-th vibration of the tool is denoted as point Piq, and the machining trajectory Ti is represented by a solid line. Further, in Figure 13 In (b), (d), and (f), the region Qi1 machined by the machining trajectory Ti of the first rotation of the workpiece 21 is coated with slashes, and the region Qi2 machined by the machining trajectory Ti of the second rotation of the workpiece 21 is coated with dots.

[0080] Figure 13 In (a), a diagram showing a state in which the workpiece 21 is machined into a substantially equilateral triangle by outer diameter machining with 3 vibrations is shown as Machining Example 3. In Machining Example 3, the tool vibrates 3 times per revolution of the workpiece 21, and the outer peripheral surface is machined into a substantially equilateral triangle. At this time, when viewed from the Z-axis direction, the machining trajectory To of the workpiece 21 is always the same trajectory regardless of the number of rotation cycles. Therefore, in Figure 13 only the region Qo1 is shown in (a).

[0081] Figure 13 In (b), a diagram showing a state in which the workpiece 21 is machined into a substantially equilateral triangle by inner diameter machining with 3 vibrations is shown as Machining Example 4. In Machining Example 4, the tool vibrates 3 times per revolution of the workpiece 21, and the inner peripheral surface is machined into a substantially equilateral triangle. At this time, when viewed from the Z-axis direction, the machining trajectory Ti of the workpiece 21 is always the same trajectory regardless of the number of rotation cycles. Therefore, in Figure 13 only the region Qi1 is shown in (b).

[0082] Figure 13 In (c) is a view showing a state in which the workpiece 21 is machined into a substantially equilateral triangle by means of outer diameter machining with a vibration frequency of 1.5 as Machining Example 5. In Machining Example 5, the tool vibrates 3 times while the workpiece 21 rotates twice, and the outer peripheral surface is machined into a substantially equilateral triangle. Figure 13 The machining trajectory To shown in (c) in [reference] is a trajectory obtained by overlapping the machining trajectory To of the first rotation of the workpiece 21 and the machining trajectory To of the second rotation of the workpiece 21 and extracting only the portions where the tool has a large cutting amount into the workpiece 21. Further, in Machining Example 5, as Figure 13 shown in (c) in [reference], when viewed from the Z-axis direction, the regions Qo1 and Qo2 coexist in a mixed manner.

[0083] Figure 13 In (d) is a view showing a state in which the workpiece 21 is machined into a substantially equilateral triangle by means of inner diameter machining with a vibration frequency of 1.5 as Machining Example 6. In Machining Example 6, the tool vibrates 3 times while the workpiece 21 rotates twice, and the inner peripheral surface is machined into a substantially equilateral triangle. Figure 13 The machining trajectory To shown in (d) in [reference] is a trajectory obtained by overlapping the machining trajectory To of the first rotation of the workpiece 21 and the machining trajectory To of the second rotation of the workpiece 21 and extracting only the portions where the tool has a large cutting amount into the workpiece 21. Further, in Machining Example 6, as Figure 13 shown in (d) in [reference], when viewed from the Z-axis direction, the regions Qi1 and Qi2 coexist in a mixed manner.

[0084] Figure 13 In (e) is a view showing a state in which the workpiece 21 is machined into a substantially square by means of outer diameter machining with a vibration frequency of 4 as Machining Example 7. In Machining Example 7, the tool vibrates 4 times while the workpiece 21 rotates once, and the outer peripheral surface is machined into a substantially square. At this time, when viewed from the Z-axis direction, the machining trajectory To of the workpiece 21 is always the same trajectory regardless of the number of rotation turns. Therefore, only the region Qo1 is shown in (e) in [reference]. Figure 13 In (e) in [reference]

[0085] Figure 13 In (f) is a view showing a state in which the workpiece 21 is machined into a substantially square by means of inner diameter machining with a vibration frequency of 4 as Machining Example 8. In Machining Example 8, the tool vibrates 4 times while the workpiece 21 rotates once, and the inner peripheral surface is machined into a substantially square. At this time, when viewed from the Z-axis direction, the machining trajectory Ti of the workpiece 21 is always the same trajectory regardless of the number of rotation turns. Therefore, only the region Qi1 is shown in (f) in [reference]. Figure 13 In (f) in [reference]

[0086] As described above, according to this embodiment, when viewed from the direction of the rotation axis of the workpiece, the outer peripheral surface and the inner peripheral surface of the workpiece can be efficiently machined into a substantially regular polygon by turning. In this embodiment, when the workpiece is machined into a regular n-sided polygon, when the constant rotation period of the workpiece is set to m rotations, the rotation mechanism and the vibration mechanism are linked and controlled so that the tool vibrates at a vibration frequency of n / m. At this time, m is a natural number of 1 or more, n is a natural number of 3 or more, and n and m are relatively prime to each other. Therefore, according to this embodiment, for example, the vibration frequency can be set to 1.2 and the workpiece can be machined into a substantially regular hexagon every 5 rotations, or the vibration frequency can be set to 1.75 and the workpiece can be machined into a substantially regular heptagon every 4 rotations.

[0087] As described above, by driving the rotation mechanism and the vibration mechanism so that the vibration frequency is n / m, the tool is located at the same position on the vibration direction V1 every constant rotation period m of the workpiece, and the workpiece is machined into a substantially regular n-sided polygon every m rotations of the workpiece. In addition, in addition to the rotation mechanism and the vibration mechanism, the workpiece can also be machined into a substantially regular polygon in multiple paths by driving the moving mechanism of the tool in a linked manner.

[0088] In the outer diameter machining according to this embodiment, the center of each side of the regular polygon of the workpiece is machined when the tool is at the amplitude upper limit AU. In addition, in the inner diameter machining according to this embodiment, each vertex of the regular polygon of the workpiece is machined when the tool is at the amplitude upper limit AU. The control unit 15 controls the rotation mechanism and the moving mechanism so that the workpiece is cut by the tool in this positional relationship, thereby machining the workpiece into a substantially regular polygon.

[0089] Furthermore, according to this embodiment, multiple vibration frequencies can be set for regular polygons with the same number of sides. For example, when machining the outer peripheral surface of the workpiece into an equilateral triangle, the vibration frequency can be set to 3 (see (a) in Figure 13 ), or the vibration frequency can be set to 1.5 (see (c) in Figure 13 ). Since there is a limit to the vibration speed generated by the vibration mechanism, by increasing the rotation period m by reducing the vibration frequency n / m, the rotational speed (peripheral speed) of the workpiece can be increased to reduce the machining time and improve the productivity.

[0090] <Other Embodiments> The above embodiments are only examples, and the present disclosure can be appropriately changed and implemented without departing from its gist. In addition, the processes and means described in the present disclosure can be freely combined and implemented as long as there is no technical contradiction. For example, in the above embodiment, machining is performed while rotating a cylindrical workpiece, but the workpiece is not limited to a cylindrical shape.

[0091] In addition, the processing described as being performed by one device can also be shared and executed by multiple devices. Alternatively, one device can execute the processing that has been described as being performed by different devices. In a computer system, it is possible to flexibly change the hardware structure by which each function is implemented.

[0092] (Description of Reference Numerals) 10: Machine tool; 15: Control unit; 21: Workpiece (object to be cut); 31: Tool; S1: Rotation axis direction; V1: Vibration direction.

Claims

1. A machine tool, comprising: A main shaft on which a workpiece to be machined is mounted; A rotation mechanism that rotates the main shaft; A tool holding portion that holds a tool for machining the workpiece to be machined; A moving mechanism that relatively moves the main shaft and the tool holding portion in the axial direction of rotation of the main shaft; A vibration mechanism that relatively vibrates the main shaft and the tool holding portion in a vibration direction orthogonal to the axial direction of rotation; And A control unit that controls the rotation mechanism and the vibration mechanism, While the main shaft is rotated by the rotation mechanism, the workpiece to be machined and the tool are relatively vibrated and moved by the moving mechanism and the vibration mechanism, whereby the workpiece to be machined is machined. It is characterized in that The control unit drives the rotation mechanism and the vibration mechanism so that the tool is located at the same position every constant rotation period of the main shaft in the vibration direction, and controls the rotation mechanism and the vibration mechanism to machine the outer peripheral surface or the inner peripheral surface of the workpiece to be machined into a substantially regular polygon when viewed from the axial direction of rotation.

2. The machine tool according to claim 1, characterized in that The control unit sets the number of vibrations of the vibration mechanism per rotation of the main shaft according to the number of sides of the regular polygon.

3. The machine tool according to claim 2, characterized in that When the constant rotation period is set to m revolutions and the number of sides of the regular polygon is set to n sides, m is a natural number of 1 or more, n is a natural number of 3 or more, and m and n are relatively prime to each other, The control unit sets the number of vibrations of the vibration mechanism to n / m.

4. The machine tool according to claim 1, characterized in that When the tool is at the amplitude upper limit of the vibration waveform of the tool generated by the vibration mechanism, the cutting depth of the tool into the workpiece to be machined is greater than when the tool is at the amplitude lower limit of the vibration waveform, The control unit synchronously controls the moving mechanism and the vibration mechanism so that when machining the outer peripheral surface of the workpiece to be machined, the center of the side of the regular polygon is machined when the tool is at the amplitude upper limit of the vibration waveform.

5. The machine tool according to claim 1, characterized in that When the tool is at the amplitude upper limit of the vibration waveform of the tool generated by the vibration mechanism, the cutting depth of the tool into the workpiece to be machined is greater than when the tool is at the amplitude lower limit of the vibration waveform, The control unit synchronously controls the moving mechanism and the vibration mechanism so that when machining the inner peripheral surface of the workpiece to be machined, the vertex of the regular polygon is machined when the tool is at the amplitude upper limit of the vibration waveform.

6. The machine tool according to claim 1, characterized in that The moving mechanism is configured to relatively move the main shaft and the tool holding portion in a direction parallel to the vibration direction.

7. The machine tool according to claim 6, characterized in that The control unit can control the operation of the moving mechanism, In the case of performing a first machining to obtain a machined surface that is substantially a regular polygon when viewed from the direction of the rotation axis, and a second machining to machine the machined surface into a shape similar to the machined surface when viewed from the direction of the rotation axis, the control unit controls the rotation mechanism, the movement mechanism, and the vibration mechanism so that the phase of the vibration waveform of the tool generated by the vibration mechanism with respect to the rotation of the spindle in the second machining is the same as that in the first machining.

8. A control device for controlling a machine tool, the machine tool comprising: a spindle on which an object to be cut is mounted; a rotation mechanism that rotates the spindle; a tool holding portion that holds a tool for cutting the object to be cut; a movement mechanism that relatively moves the spindle and the tool holding portion in the direction of the rotation axis of the spindle; and a vibration mechanism that relatively vibrates the spindle and the tool holding portion in a vibration direction orthogonal to the rotation axis direction, while the machine tool rotates the spindle by the rotation mechanism, the object to be cut and the tool are relatively vibrated and moved by the movement mechanism and the vibration mechanism, whereby an outer peripheral surface or an inner peripheral surface of the object to be cut is machined into a shape that is substantially a regular polygon when viewed from the direction of the rotation axis, characterized in that the control device drives the rotation mechanism and the vibration mechanism so that the tool is located at the same position every constant rotation period of the spindle in the vibration direction.

Images