Machine tools and control devices

Abstract

To efficiently process the polygonal shape by turning processing.SOLUTION: A machine tool includes: a main spindle to which a cutting object 21 is mounted; a rotation mechanism which rotates the main spindle; a tool holding part which holds a tool; a movement mechanism which relatively moves the main spindle and the tool holding part in the rotation axis direction of the main spindle; a vibration mechanism which relatively vibrates the main spindle and the tool holding part in the vibration direction; and a control unit that controls the rotation mechanism and the vibration mechanism. The machine tool cuts the cutting object 21 by moving the cutting object 21 and the tool while relatively vibrating them with the movement mechanism and the vibration mechanism while rotating the main spindle with the rotation mechanism. The control unit drives the rotation mechanism and the vibration mechanism so that the tool is located at the same position in the vibration direction for each constant rotation cycle of the main spindle, and controls the rotation mechanism and the vibration mechanism so that the outer peripheral surface or inner peripheral surface of the cutting object 21 is processed into a substantially-regular polygonal shape when viewed from the rotation axis direction.SELECTED DRAWING: Figure 4

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 the workpiece (object to be cut) is rotated by a machine tool while being cut, there are limitations on the finished shape of the workpiece. Turning is exclusively performed to obtain a cylindrical shape, a columnar shape, or a combined shape thereof.

[0003] Conventionally, in turning, a method of processing a workpiece into a shape other than a cylinder or a column by controlling the movement of a tool and the rotation of the workpiece in联动 has been proposed. Patent Document 1 discloses a technique for obtaining a spiral groove shape by turning by controlling a tool and a workpiece so that the cutting amount is varied in synchronization with the rotational phase of the workpiece while the tool is moved in the feed direction.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, the above-described technique is for processing a spiral groove shape on a workpiece, and for example, it is not possible to process a flat surface on the outer peripheral surface or the inner peripheral surface of the workpiece using the above-described technique.

[0006] An object of the present invention is to efficiently process a cutting object into a substantially regular polygon by turning.

Means for Solving the Problems

[0007] (Aspect 1) To solve the above problems, a machine tool according to embodiment 1 of the present invention comprises a spindle to which a workpiece to be cut is attached, a rotation mechanism for rotating the spindle, a tool holder for holding a tool for cutting the workpiece, a movement mechanism for moving the spindle and the tool holder relative to each other in the direction of the rotation axis of the spindle, a vibration mechanism for vibrating the spindle and the tool holder relative to each other in a vibration direction perpendicular to the rotation axis, and a control unit for controlling the rotation mechanism and the vibration mechanism, wherein the machine tool cuts the workpiece by rotating the spindle with the rotation mechanism and moving the workpiece and the tool while vibrating them relative to each other with the movement mechanism and the vibration mechanism, wherein the control unit drives the rotation mechanism and the vibration mechanism so that the tool is positioned at the same position in the vibration direction at regular rotation cycles of the spindle, and controls the rotation mechanism and the vibration mechanism so that the outer or inner surface of the workpiece is machined into a substantially regular polygon when viewed from the direction of the rotation axis.

[0008] (Aspect 2) In the above embodiment 1, the control unit may set the vibration frequency of the vibration mechanism per rotation of the main shaft based on the number of sides of the regular polygon.

[0009] (Aspect 3) In the above embodiment 2, when the constant rotation period is m rotations and the number of sides of the regular polygon is n, m is a natural number of 1 or more, n is a natural number of 3 or more, m and n are relatively prime, and the control unit may set the vibration frequency of the vibration mechanism to n / m.

[0010] (Aspect 4) In any one of the above embodiments 1 to 3, when the tool is located at the upper limit of the amplitude of the vibration waveform of the tool produced by the vibration mechanism, the amount of cutting by the tool into the workpiece is larger compared to when the tool is located at the lower limit of the amplitude of the vibration waveform, and the control unit may synchronize control the moving mechanism and the vibration mechanism so that when the outer surface of the workpiece is being cut, the center of the sides of the regular polygon is machined when the tool is located at the upper limit of the amplitude of the vibration waveform.

[0011] (Aspect 5) In any one of the above embodiments 1 to 4, when the tool is located at the upper limit of the amplitude of the vibration waveform of the tool produced by the vibration mechanism, the amount of cutting by the tool into the workpiece is larger compared to when the tool is located at the lower limit of the amplitude of the vibration waveform, and the control unit may synchronize control the moving mechanism and the vibration mechanism so that when the inner surface of the workpiece is being cut, the vertices of the regular polygon are machined when the tool is located at the upper limit of the amplitude of the vibration waveform.

[0012] (Aspect 6) In any one of the above embodiments 1 to 5, the moving mechanism may be configured such that the main shaft and the tool holding portion can move relative to each other in a direction parallel to the vibration direction.

[0013] (Aspect 7) In the above embodiment 6, the control unit can control the operation of the moving mechanism, and when performing a first machining operation to obtain a machined surface that is substantially a regular polygon when viewed from the direction of the rotation axis, and a second machining operation to machine the machined surface to a shape similar to the machined surface when viewed from the direction of the rotation axis, the control unit may control the rotation mechanism, the moving mechanism, and the vibration mechanism so that the phase of the vibration waveform of the tool caused by the vibration mechanism with respect to the rotation of the spindle in the second machining operation matches that of the first machining operation.

[0014] (Pattern 8) To solve the above problems, a machine tool according to aspect 8 of the present invention includes a spindle to which a workpiece to be machined is attached, a rotation mechanism that rotates the spindle, a tool holding portion that holds a tool for machining the workpiece, a movement mechanism that relatively moves the spindle and the tool holding portion in the axial direction of rotation of the spindle, and a vibration mechanism that relatively vibrates the spindle and the tool holding portion in a vibration direction orthogonal to the axial direction of rotation. While rotating the spindle by the rotation mechanism, the movement mechanism and the vibration mechanism relatively vibrate and move the workpiece and the tool, so that a control device that controls a machine tool for machining an outer peripheral surface or an inner peripheral surface of the workpiece into a substantially regular polygon when viewed from the axial direction of rotation drives the rotation mechanism and the vibration mechanism so that the tool is located at the same position in the vibration direction at every constant rotation cycle of the spindle.

Advantages of the Invention

[0015] According to the present invention, a workpiece can be efficiently machined into a substantially regular polygon by turning.

Brief Description of the Drawings

[0016] [Figure 1] It is a schematic configuration diagram of a machine tool according to an embodiment of the present invention. [Figure 2] It is a view showing a workpiece machined into a polygon by outer diameter machining. [Figure 3] It is a front view showing a state of outer diameter machining according to an embodiment. [Figure 4] It is a perspective view showing a state of outer diameter machining according to an embodiment. [Figure 5] It is a top view and a side view showing a state of outer diameter machining according to an embodiment. [Figure 6] It is a view showing a machining locus of each pass of outer diameter machining according to an embodiment. [Figure 7] It is a view showing the relationship between the workpiece rotation phase and the tool position according to an embodiment. [Figure 8] It is a view showing a workpiece machined into a polygon by inner diameter machining. [Figure 9]It is a front view showing the state of inner diameter machining according to the embodiment. [Figure 10] It is a perspective view showing the state of inner diameter machining according to the embodiment. [Figure 11] It is a view showing the state of inner diameter machining according to the embodiment. [Figure 12] It is a view showing the machining trajectory of each pass of inner diameter machining according to the embodiment. [Figure 13] It is a view showing another example of machining a workpiece into a polygon according to the embodiment.

Mode for Carrying Out the Invention

[0017] Hereinafter, with reference to the drawings, the mode for carrying out this invention will be exemplarily and specifically described based on the embodiment. Note that the dimensions, materials, shapes, and relative arrangements of the components described in this embodiment should be appropriately changed according to the configuration of the apparatus to which the invention is applied and various conditions. That is, it is not intended to limit the scope of this invention to the following embodiments.

[0018] The present invention is suitable for a machine tool that machines a cutting object into a polygon with a tool while rotating the cutting object. The present invention can also be regarded as a control device for controlling the machine tool.

[0019] <Embodiment> (Machine tool 10) First, the schematic configuration of the machine tool 10 according to the embodiment of the present invention will be described. FIG. 1 is a schematic diagram showing the schematic configuration of the machine tool 10 according to the embodiment. The machine tool 10 includes a workpiece holding portion 11 that rotatably holds a workpiece 21 as a cutting object, 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. For convenience of explanation, the X-axis, Y-axis, and Z-axis that are orthogonal to each other are shown in the drawing as necessary. The X-axis and the Z-axis face the horizontal direction, and the Y-axis faces the vertical direction. Also, 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.

[0020] The workpiece holder 11 holds the workpiece 21 so that it can rotate in the rotational direction R1 and move in the rotational direction axis S1 of the workpiece 21. The tool holder 13 holds the tool so that it can move in a first direction S2 parallel to the rotational direction axis S1 and in a second direction S3 perpendicular to the first direction S2. The rotational direction axis 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. Furthermore, the tool holder 13 is configured to hold multiple tools, and Figure 1 shows the tool holder 13 holding a tool 31 for outer diameter machining and a tool 33 for inner diameter machining.

[0021] The machine tool 10 includes a rotation mechanism that rotates the workpiece 21 using a workpiece holding section 11, and a movement mechanism that moves the workpiece 21 and the tool in parallel relative to each other using the workpiece holding section 11 and the tool holding section 13. Known technologies such as various motors can be used for the rotation mechanism, and known technologies such as linear servo motors, ball screw mechanisms, and rack and pinion mechanisms can be used for the movement mechanism.

[0022] Furthermore, the machine tool 10 is equipped with a vibration mechanism that vibrates the workpiece 21 and the tool relative to each other in a direction parallel to the direction of movement of the moving mechanism. In this embodiment, the tool holder 13 holds the tool so that it can vibrate in a vibration direction V1 parallel to the X-axis direction. Various known technologies capable of causing the object to be vibrated to reciprocate can be employed in the vibration mechanism.

[0023] The control unit 15 is a control device configured to control the operation of the aforementioned rotation mechanism, movement mechanism, and vibration mechanism. The control unit 15 can control various mechanisms in conjunction, for example, workpiece 2 The workpiece holder 11 and the tool holder 13 can be controlled so that turning is performed in synchronization with the rotational phase of the tool, including the movement in the feed direction and the cutting direction.

[0024] In this embodiment, 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 so as to be vibrable in one direction. However, in applying the present invention, the machine tool 10 may be configured to hold the workpiece 21 so as to be movable in two directions and so as to be vibrable in one direction instead of the tool. Alternatively, the machine tool 10 may be configured to hold only the tool so as to be movable. More specifically, the machine tool 10 should be configured so that the workpiece 21 and the tool are relatively movable in the Z-axis direction and the X-axis direction, and relatively vibrate in the X-axis direction. With this configuration, the machine tool 10 can control the rotation mechanism and the vibration mechanism in conjunction to machine the outer and inner surfaces of the workpiece 21 into a substantially regular polygon when viewed from the rotation axis direction of the workpiece 21. Below, a method for machining the workpiece 21 into a substantially regular polygon by cutting while vibrating the tool 31 in synchronization with the rotation phase of the workpiece 21 will be described based on several machining examples.

[0025] (Processing example 1) First, as machining example 1, we will explain the case in which the outer surface of the workpiece 21 is machined into a roughly regular pentagon by cutting while vibrating the tool 31 in synchronization with the rotational phase of the workpiece 21 using the machine tool 10. Figure 2(a) is a diagram showing how the outer surface of the workpiece 21 is machined into a regular pentagon when viewed from the Z-axis direction, and shows the outer diameter machining tool 31 in contact with the outer surface of the workpiece 21. Figure 2(b) is a perspective view of the machined outer surface of the workpiece 21 when viewed from the Z-axis direction. The workpiece 21 is held by the claw portion 17 that constitutes the main spindle of the workpiece holding portion 11 and rotates integrally with the main spindle.

[0026] This section describes a method for machining the outer surface of a workpiece 21 into a regular pentagon by setting the vibration frequency of the tool 31 per rotation of the workpiece 21 to 2.5 times. In the following description, the vibration frequency of the tool refers to the vibration frequency per rotation of the workpiece 21. That is, when the vibration frequency is 2.5 times, the tool 31 vibrates 5 times when the workpiece 21 rotates 2 times.

[0027] Figures 3(a) to 3(c), 4, and 5(a) and 5(b) illustrate how the outer diameter is machined at a vibration frequency of 2.5 times. In machining example 1, the machine tool 10 rotates the workpiece 21 while moving the tool 31 in the Z-axis direction (feed direction) and vibrating it in the X-axis direction (cutting direction) to perform cutting. In machining example 1, the tool 31 is vibrated in a sinusoidal wave by the vibration mechanism, and the workpiece 21 is rotated counterclockwise in Figure 2(a).

[0028] Figures 3(a) to 3(c) are front views showing the outer diameter machining process performed by the machine tool 10, with the machining trajectory To shown as a solid line. The machining trajectory To indicates the position where the tip of the tool 31 in the cutting direction contacts the workpiece 21, and the outer surface of the workpiece 21 is machined following the machining trajectory To. In Figures 3(a) to 3(c), the upper amplitude AU, the middle amplitude AM, and the lower amplitude AL of the tool 31 are shown as dashed lines. The amount of cutting of the tool 31 into the workpiece 21 in the X-axis direction is largest when the tool 31 is at the upper amplitude AU and smallest when the tool 31 is at the lower amplitude AL. Because the tool 31 contacts the outer surface of the workpiece 21, the diameter of the circle indicating the lower amplitude AL is largest and the diameter of the circle indicating the upper amplitude AU is smallest. Furthermore, in the drawings showing the machining trajectory, as shown in Figures 3(a) to 3(c), the machining trajectory is magnified to clearly show the vibration of the tool, including the vibration direction V1 and the feed direction.

[0029] Figure 3(a) is a front view showing the machining trajectory To of the workpiece 21 during its first rotation, as seen 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(a), point Po1 is the starting point of the first vibration of the tool 31, point Po2 is the ending point of the first vibration of the tool 31 and the starting point of the second vibration of the tool 31, and point Po2 is the ending point of the second vibration of the tool 31 and the tool The starting point of the third vibration of tool 31 is shown as point Po3. Furthermore, in Figure 3(a), the midpoint of the third vibration of tool 31, which is the position when tool 31 has vibrated 2.5 times, is shown as point Po3.5.

[0030] In this machining process, the lower amplitude limit AL is set to coincide with the outer surface of the workpiece 21 before machining. The tool 31 is positioned at point Po1 and begins to contact the workpiece 21 at the lower amplitude limit AL. When the workpiece 21 rotates 2 / 5 of a turn, the tool 31 vibrates once and moves to point Po2, where it again contacts the workpiece 21 at the lower amplitude limit AL. When the workpiece 21 rotates another 2 / 5 of a turn, the tool 31 vibrates once more and moves to point Po3, where it contacts the workpiece 21 at the lower amplitude limit AL. When the workpiece 21 rotates another 1 / 5 of a turn, the tool vibrates 1 / 2 of a turn and moves to point Po3.5, where it contacts the workpiece 21 at the upper amplitude limit AU. In Figure 3(a), the region Qo1 that is machined during the second rotation of the workpiece 21 is shaded.

[0031] Figure 3(b) is a front view showing the machining trajectory To of the workpiece 21 during its second rotation, as seen from the Z-axis direction. In Figure 3(b), point Po4 is shown as the endpoint of the third vibration of the tool 31 and the starting point of the fourth vibration; point Po5 is shown as the endpoint of the fourth vibration of the tool 31 and the starting point of the fifth vibration of the tool 31; and point Po6 is shown as the endpoint of the fifth vibration of the tool 31 and the starting point of the sixth vibration of the tool 31. Furthermore, in Figure 3(b), point Po3.5 is shown as the midpoint of the third vibration of the tool 31 and the position of the tool 31 at the start of the second rotation of the workpiece 21.

[0032] As described above, at the start of the second rotation of workpiece 21, tool 31 is located at point Po3.5. As workpiece 21 rotates 1 / 5 of a turn, tool 31 moves to point Po4 and contacts workpiece 21 at the lower amplitude limit AL. When workpiece 21 rotates 2 / 5 of a turn, tool 31 vibrates once and moves to point Po5, contacting workpiece 21 again at the lower amplitude limit AL. As workpiece 21 rotates another 2 / 5 of a turn, tool 31 vibrates one more time and moves to point Po6, contacting workpiece 21 at the lower amplitude limit AL. In Figure 3(b), the region Qo2 that is machined during the second rotation of workpiece 21 is filled in with dots.

[0033] From the third rotation onward of the workpiece 21, the above-described machining process is repeated sequentially. Specifically, for odd-numbered rotations of the workpiece 21, machining is performed along the machining trajectory To shown in Figure 3(a), and for even-numbered rotations of the workpiece 21, machining is performed along the machining trajectory To shown in Figure 3(b). Furthermore, the control unit 15 drives the rotation mechanism and vibration mechanism so that the tool 31 is positioned at the same location in the vibration direction V1 at regular rotational periods of the spindle of the workpiece holding unit 11 that holds the workpiece 21. More specifically, when the workpiece 21 rotates s(s:0,1,2,…)×144°, the tool 31 is at the lower amplitude limit AL, and when the workpiece 21 rotates t(t:0,1,2,…)×144+72°, the tool 31 is at the upper amplitude limit AU. As this machining is performed continuously in the rotation axis direction S1 (Z axis direction) of the workpiece 21, the outer surface of the workpiece 21 is machined into a roughly regular pentagon when viewed from the rotation axis direction S1.

[0034] Figure 3(c) shows the superimposed machining trajectories To of the first and second rotations of the workpiece 21. Figure 3(c) shows only the portion where the depth of cut of the tool 31 into the workpiece 21 is large, from the superimposed machining trajectory To of the first rotation of the workpiece 21 and the machining trajectory To of the workpiece 21 into the workpiece 21. As shown in Figure 3(c), the superimposed machining trajectory To is formed in the shape of a roughly regular pentagon, indicating that the workpiece 21 is machined into a roughly regular pentagon by the above machining process. As stated above, Figures 3(a) to (c) are diagrams that are partially enlarged in the vibration direction V1 of the tool 31, and in actual machining, the workpiece 21 is machined into a shape closer to a regular pentagon than the shape shown in Figure 3(c).

[0035] As shown in Figure 3(c), in machining example 1, each vertex of the regular pentagon of the workpiece 21 is machined when the tool 31 is positioned at the midpoint AM of the amplitude, and the center of each side of the regular pentagon of the workpiece 21. The workpiece 21 is machined when the tool 31 is at the upper amplitude limit AU. That is, the circle indicating the upper amplitude 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 movement mechanism so that the workpiece 21 is cut by the tool 31 in this positional relationship.

[0036] Figure 4 is a perspective view showing the machining trajectory To and points Po1 to Po6 when the workpiece 21 has made two rotations. During machining, the tool 31 always moves in the Z-axis direction with a feed rate F per rotation. That is, the distance in the Z-axis direction between point Po1 and point Po6 is 2F.

[0037] Figure 5(a) is a top view from the Y-axis direction showing the machining trajectory To when machining continues from the state in Figure 4 and the tool 31 moves in the feed direction (Z-axis direction). Figure 5(b) is a side view of Figure 5(a) from the X-axis direction. In machining example 1, since the vibration frequency is 2.5, the tool 31 is located at the same position in the vibration direction V1 every two rotations of the workpiece 21. That is, at point Po1 of the first rotation of the workpiece 21 and at point Po1 of the third rotation of the workpiece 21, the tool 31 is located at the same position in the vibration direction V1.

[0038] As described above, in Figures 4 and 5(a) and (b), the machining trajectory To is shown magnified in the Z-axis direction. In actual machining, the feed rate F is set so that the parts of the workpiece 21 machined at odd-numbered rotations and the parts machined at even-numbered rotations partially overlap in the Z-axis direction. The outer surface of the workpiece 21 is then machined into a roughly regular pentagon.

[0039] The machine tool 10 can perform the machining of the workpiece 21 described above by dividing it into multiple machining passes in the cutting direction. Figure 6 shows the machining trajectory when the workpiece 21 is machined in three passes. In Figure 6, the outer surface 21a of the workpiece 21 before machining is shown as a dotted line, the machining trajectory To1 of the first pass (first machining) is shown as a dashed line, the machining trajectory To2 of the second pass (second machining) is shown as a double dashed line, and the machining trajectory To3 of the third pass (third machining) is shown as a solid line. In machining example 1, the machining trajectory To1 is drawn so as to be tangent to the outer surface 21a of the workpiece 21. Furthermore, in Figure 6, the area Qp1 machined in the first pass is filled with a diagonal line, the area Qp2 machined in the second pass is filled with a horizontal line, and the area Qp3 machined in the third pass is filled with a vertical line.

[0040] The control unit 15 moves the tool 31 in synchronization with the rotational phase of the workpiece 21, thereby making the rotational phase of the workpiece 21 coincide with the point in time when the tool 31 begins to contact the workpiece 21 in multiple machining passes. As the workpiece 21 is cut with the same vibration frequency and feed rate, the phases of the vibration waveforms of the tool 31 coincide with each other in multiple machining passes, and the positions of the vertices of the regular pentagon relative to the rotational phase of the workpiece 21 coincide with each other.

[0041] As shown in Figure 6, machining paths To1, To2, and To3 are all approximately regular pentagons and are similar in shape to each other. That is, when the workpiece 21 is viewed from the Z-axis direction, a machined surface of approximately regular pentagonal shape is obtained in each path. In other words, according to this 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 material removal allowance of the workpiece 21, and machining can be performed simply and efficiently without pre-machining.

[0042] Figure 7 is a graph showing the relationship between the rotational phase of the workpiece 21 and the cutting direction position of the tool 31. In the graph of Figure 7, the vertical axis represents the cutting direction position of the tool 31, and the horizontal axis represents the rotational phase of the workpiece 21. It shows the cutting direction position of the tool 31 for odd-numbered and even-numbered rotations of the workpiece 21 from the 1st to the 3rd pass. In Figure 7, the vibration waveforms L11, L12, and L13, which indicate the cutting direction position of the tool 31 for odd-numbered rotations of the workpiece in the 1st, 2nd, and 3rd passes, are shown as dotted lines. Similarly, in Figure 7, the vibration waveforms L21, L22, and L23, which indicate the cutting direction position of the tool 31 for even-numbered rotations of the workpiece in the 1st, 2nd, and 3rd passes, are shown as dashed lines.

[0043] As shown in Figure 7, the control unit 15 drives the rotation mechanism, vibration mechanism, and movement mechanism in conjunction so that the phases of the vibration waveforms of the tool 31 coincide in multiple machining passes. In machining example 1, the phases of vibration waveforms L11, L12, and L13 coincide with the rotation phase of the workpiece 21, and the phases of vibration waveforms L21, L22, and L23 coincide with the rotation phase of the workpiece 21. By controlling each mechanism in this way, the workpiece 21 is machined into a substantially regular polygon in multiple passes.

[0044] Furthermore, in machining example 1, the depth of cut Xs of the tool 31 relative to the workpiece 21 in the X-axis direction and the vibration amplitude Xt of the tool 31 (the difference between the upper amplitude limit AU and the lower amplitude limit AL) are set to the same value. However, these values ​​may be set to different values.

[0045] As described above, the machine tool 10 of this embodiment allows for machining of the outer surface of a workpiece into a substantially regular polygon by controlling the rotation mechanism and vibration mechanism in conjunction. While polygon machining, which involves rotating the tool and workpiece around parallel axes, is another method for machining a workpiece into a polygon, the machining method of this embodiment is more efficient than such polygon machining. Furthermore, while polygon machining involves intermittent cutting, the machining method of this embodiment allows for continuous cutting to machine the workpiece into a substantially regular polygon, thus enabling stable cutting.

[0046] (Processing example 2) Next, as machining example 2, we will describe a case in which the inner circumferential surface of the workpiece 21 is machined into a roughly regular pentagon by cutting while vibrating the tool 33 in synchronization with the rotational phase of the workpiece 21 using the machine tool 10. Figure 8(a) is a diagram showing how the inner circumferential surface of the workpiece 21 is machined into a regular pentagon when viewed from the Z-axis direction, and shows the inner circumferential machining tool 33 in contact with the inner circumferential surface of the workpiece 21. Figure 8(b) is a perspective view of the machined inner circumferential surface of the workpiece 21 when viewed from the Z-axis direction. The workpiece 21 is held by the claw portion 17 and rotates integrally with the spindle of the workpiece holding portion 11.

[0047] When machining the inner circumferential surface of the workpiece 21 into a regular polygon, the process is carried out with a pilot hole 21b already formed in the workpiece 21. The diameter of the pilot hole 21b can be changed depending on the amount of material removed from the final shape and the internal diameter machining tool 33 used.

[0048] Using Figures 9(a)-(c), 10, and 11(a) and (b), a method for machining the inner surface of the workpiece 21 into a regular pentagon is described by setting the vibration frequency of the tool 31 per rotation of the workpiece 21 to 2.5 times. In machining example 2 as well, the machine tool 10 rotates the workpiece 21 and performs cutting by moving the tool 31 in the Z-axis direction (feed direction) while vibrating it in the X-axis direction (cutting direction). Also in machining example 2, the tool 33 is vibrated in a sinusoidal wave by the vibration mechanism, and the workpiece 21 is rotated counterclockwise in Figure 8(a).

[0049] Figures 9(a) to (c) are front views showing the internal diameter machining process performed by the machine tool 10, with the machining trajectory Ti shown as a solid line. The machining trajectory Ti indicates the position where the tip of the tool 33 in the cutting direction contacts the workpiece 21, and the inner surface of the workpiece 21 is machined following the machining trajectory Ti. In Figures 9(a) to (c), the upper amplitude AU, middle amplitude AM, and lower amplitude AL of the tool 33 are shown as dashed lines. Because the tool 33 contacts the inner surface of the workpiece 21, the diameter of the circle indicating the upper amplitude AU is the largest, and the diameter of the circle indicating the lower amplitude AL is the smallest.

[0050] Figure 9(a) is a front view showing the machining trajectory Ti of the workpiece 21 during its first rotation, as seen from the Z-axis direction. As described above, the tool 33 vibrates 2.5 times during one rotation of the workpiece 21. In Figure 9(a), the starting point of the first vibration of tool 31 is shown as point Pi1, the ending point of the first vibration of tool 31, which is the starting point of the second vibration of tool 33, is shown as point Pi2, and the ending point of the second vibration of tool 33, which is the starting point of the third vibration of tool 33, is shown as point Pi3.5. Furthermore, in Figure 9(a), the midpoint of the third vibration of tool 33, which is the position when tool 33 has vibrated 2.5 times, is shown as point Pi3.5.

[0051] In this machining process, the lower amplitude limit AL is set to coincide with the inner circumferential surface (pilot hole 21b) of the workpiece 21 before machining. The tool 33 is positioned at point Pi1 and begins to contact the workpiece 21 at the lower amplitude limit AL. When the workpiece 21 rotates 2 / 5 of a turn, the tool 33 vibrates once and moves to point Pi2, where it again contacts the workpiece 21 at the lower amplitude limit AL. When the workpiece 21 rotates another 2 / 5 of a turn, the tool 33 vibrates once more and moves to point Pi3, where it contacts the workpiece 21 at the lower amplitude limit AL. When the workpiece 21 rotates another 1 / 5 of a turn, the tool vibrates 1 / 2 of a turn and moves to point Pi3.5, where it contacts the workpiece 21 at the upper amplitude limit AU. In Figure 9(a), the region Qi1 that is machined during the second rotation of the workpiece 21 is shaded.

[0052] Figure 9(b) is a front view showing the machining trajectory Ti of the workpiece 21 during its second rotation, as seen from the Z-axis direction. In Figure 9(b), point Pi4 represents the end point of the third vibration of the tool 33 and the start point of the fourth vibration; point Pi5 represents the end point of the fourth vibration of the tool 33 and the start point of the fifth vibration of the tool 33; and point Pi6 represents the end point of the fifth vibration of the tool 33 and the start point of the sixth vibration of the tool 33. Furthermore, in Figure 9(b), point Pi3.5 represents the midpoint of the third vibration of the tool 33 and the position of the tool 33 at the start of the second rotation of the workpiece 21.

[0053] As described above, at the start of the second rotation of the workpiece 21, the tool 33 is located at point Pi3.5. As the workpiece 21 rotates 1 / 5 of a turn, the tool 33 moves to point Pi4 and contacts the workpiece 21 at the lower amplitude limit AL. When the workpiece 21 rotates 2 / 5 of a turn, the tool 33 vibrates once and moves to point Pi5, contacting the workpiece 21 again at the lower amplitude limit AL. As the workpiece 21 rotates another 2 / 5 of a turn, the tool 33 vibrates once more and moves to point Pi6, contacting the workpiece 21 at the lower amplitude limit AL. In Figure 9(b), the region Qi2 that is machined during the second rotation of the workpiece 21 is filled in with dots.

[0054] From the third rotation onward of the workpiece 21, the above-described machining process is repeated sequentially. Specifically, for odd-numbered rotations of the workpiece 21, machining is performed along the machining trajectory Ti shown in Figure 9(a), and for even-numbered rotations of the workpiece 21, machining is performed along the machining trajectory Ti shown in Figure 9(b). Furthermore, the control unit 15 drives the rotation mechanism and vibration mechanism so that the tool 33 is positioned at the same location in the vibration direction V1 at regular rotational periods 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 at the lower amplitude limit AL, and when the workpiece 21 rotates v(v:0,1,2,…)×144+72°, the tool 33 is at the upper amplitude limit AU. As this machining is performed continuously in the rotation axis direction S1 (Z axis direction) of the workpiece 21, the inner surface of the workpiece 21 is machined into a roughly regular pentagon when viewed from the rotation axis direction S1.

[0055] Figure 9(c) shows the superimposed machining trajectories Ti of the first and second rotations of the workpiece 21. Figure 9(c) shows only the portion where the depth of cut of the tool 33 into the workpiece 21 is large, from the superimposed machining trajectory Ti of the first rotation of the workpiece 21 and the machining trajectory Ti of the workpiece 21. As shown in Figure 9(c), the superimposed machining trajectories form an approximately regular pentagon, indicating that the workpiece 21 is machined into an approximately regular pentagon by the above machining process. As stated above, Figures 9(a) to (c) are diagrams that are partially enlarged in the vibration direction V1 of the tool 33, and in actual machining, the workpiece 21 is machined into a shape closer to a regular pentagon than the shape shown in Figure 9(c).

[0056] As shown in Figure 9(c), in machining example 2, each vertex of the regular pentagon of the workpiece 21 is machined when the tool 31 is at the upper amplitude 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 midpoint of the amplitude AM. That is, the circle representing the midpoint of the amplitude 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 this positional relationship.

[0057] Figure 10 is a perspective view showing the machining trajectory Ti and points Pi1 to Pi6 when the workpiece 21 has made two rotations. During machining, the tool 33 always moves in the Z-axis direction with a feed rate F per rotation. That is, the distance in the Z-axis direction between points Pi1 and Pi6 is 2F.

[0058] Figure 11(a) is a top view from the Y-axis direction showing the machining trajectory Ti when machining continues from the state in Figure 10 and the tool 33 moves in the feed direction (Z-axis direction). Figure 11(b) is a side view of Figure 11(a) from the X-axis direction. In machining example 2, since the vibration frequency is 2.5, the tool 33 is located at the same position in the vibration direction V1 every two rotations of the workpiece 21. That is, at point Pi1 of the first rotation of the workpiece 21 and at point Pi1 of the third rotation of the workpiece 21, the tool 33 is located at the same position in the vibration direction V1.

[0059] As described above, in Figure 10 and Figures 11(a) and (b), the machining trajectory Ti is shown magnified in the Z-axis direction. In actual machining, the feed rate F is set so that the parts of the workpiece 21 machined at odd-numbered rotations and the parts machined at even-numbered rotations partially overlap in the Z-axis direction. The inner surface of the workpiece 21 is then machined into a roughly regular pentagon.

[0060] The machine tool 10 can perform the machining of the workpiece 21 described above by dividing it into multiple machining passes in the cutting direction. Figure 12 shows the machining trajectory when the workpiece 21 is machined in three passes. In Figure 12, the machining trajectory Ti1 of the first pass (first machining) is shown as a dashed line, the machining trajectory Ti2 of the second pass (second machining) is shown as a double-dashed line, and the machining trajectory Ti3 of the third pass (third machining) is shown as a solid line. In machining example 2, the machining trajectory Ti1 is drawn so as to be tangent to the pilot hole 21b, which is the inner circumferential surface of the workpiece 21. Furthermore, in Figure 6, the area Qp1 machined in the first pass is filled with a diagonal line, the area Qp2 machined in the second pass is filled with a horizontal line, and the area Qp3 machined in the third pass is filled with a vertical line.

[0061] In machining example 2, the control unit 15 moves the tool 33 in synchronization with the rotational phase of the workpiece 21, and in multiple machining passes, the rotational phases of the workpiece 21 coincide with each other when the tool 33 begins to contact the workpiece 21. Then, as the workpiece 21 is cut with the same vibration frequency and feed rate, the phases of the vibration waveforms of the tool 33 coincide with each other in multiple machining passes, and the positions of the vertices of the regular pentagon relative to the rotational phase of the workpiece 21 coincide with each other.

[0062] As shown in Figure 12, machining paths Ti1, Ti2, and Ti3 are all approximately regular pentagons and are similar in shape to each other. That is, when the workpiece 21 is viewed from the Z-axis direction, a machined surface of approximately regular pentagonal shape is obtained in each path. In other words, according to this embodiment, since the workpiece 21 can be machined into an approximately regular polygon by dividing it into multiple machining paths, there is no need to excessively reduce the material removal allowance of the workpiece 21, and the machining of a regular polygon can be easily performed.

[0063] As described above, according to the machine tool 10 of this embodiment, by controlling the rotation mechanism and the vibration mechanism in conjunction, the inner surface of the workpiece can be machined to be a substantially regular polygon during turning. Furthermore, according to the machining method of this embodiment, by appropriately setting the vibration amplitude and depth of cut, the workpiece can be machined to be a substantially regular polygon by continuous cutting, thus enabling stable cutting.

[0064] Based on the above, according to this embodiment, the outer and inner surfaces of the workpiece are made into a substantially regular polygon by turning. This allows for efficient machining. Furthermore, in the machining example described above, the workpiece was machined into a roughly regular pentagon by setting the cutting condition to a vibration frequency of 2.5, but the present invention allows for machining into other regular polygons by setting the vibration frequency to a different value. Below, a machining example will be described in which the vibration frequency is changed from the machining example described above, and the workpiece 21 is machined into other regular polygons according to the configuration of Embodiment 1.

[0065] (Other processing examples) Next, other machining examples according to this embodiment will be described using Figures 13(a) to (f). In the other machining examples described below, the machine tool 10 rotates the workpiece 21 and performs cutting by moving the tool in the Z-axis direction (feed direction) while vibrating it in the X-axis direction (cutting direction), thereby machining the workpiece 21 into a substantially regular polygon. In Figures 13(a) to (f), the upper limit AU of the tool amplitude, the middle limit AM of the amplitude, and the lower limit AL of the amplitude are shown by dashed lines.

[0066] Figures 13(a), (c), and (e) show examples of machining by outer diameter machining. In these figures, the starting point of the tool's q-vibration is shown as point Poq, and the machining trajectory To is shown as a solid line. In addition, in Figures 13(a), (c), and (e), the region Qo1 machined by the machining trajectory To of the first rotation of the workpiece 21 is filled with diagonal lines, and the region Qo2 machined by the machining trajectory To of the second rotation of the workpiece 21 is filled with dots.

[0067] Figures 13(b), (d), and (f) show examples of machining by internal diameter machining. In these figures, the starting point of the tool's q-vibration is shown as point Piq, and the machining trajectory Ti is shown as a solid line. In addition, in Figures 13(b), (d), and (f), the region Qi1 machined by the machining trajectory Ti of the first rotation of the workpiece 21 is filled with diagonal lines, and the region Qi2 machined by the machining trajectory Ti of the second rotation of the workpiece 21 is filled with dots.

[0068] Figure 13(a) shows the machining process for example 3, where the workpiece 21 is machined into a roughly equilateral triangle shape by outer diameter machining with a vibration frequency of 3. In machining example 3, the tool vibrates three times for each rotation of the workpiece 21, and the outer surface is machined into a roughly equilateral triangle shape. 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 rotations, so only region Qo1 is shown in Figure 13(a).

[0069] Figure 13(b) shows machining example 4, in which the workpiece 21 is machined into a roughly equilateral triangle shape by internal diameter machining with a vibration frequency of 3. In machining example 4, the tool vibrates 3 times for each rotation of the workpiece 21, and the inner surface is machined into a roughly equilateral triangle shape. 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 rotations, so only region Qi1 is shown in Figure 13(b).

[0070] Figure 13(c) shows machining example 5, where the workpiece 21 is machined into a roughly equilateral triangle shape by outer diameter machining with a vibration frequency of 1.5. In machining example 5, the tool vibrates three times for every two rotations of the workpiece 21, and the outer surface is machined into a roughly equilateral triangle shape. The machining trajectory To shown in Figure 13(c) is an excerpt of the portion where the depth of cut of the tool into the workpiece 21 is large, by superimposing 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. Also, in machining example 5, as shown in Figure 13(c), when viewed from the Z-axis direction, regions Qo1 and Qo2 are mixed.

[0071] Figure 13(d) shows the machining process for example 6, where the workpiece 21 is machined into a roughly equilateral triangle shape by internal diameter machining with a vibration frequency of 1.5. In machining example 6, the tool vibrates three times for every two rotations of the workpiece 21, machining the inner surface into a roughly equilateral triangle shape. The machining trajectory To shown in Figure 13(d) is an excerpt of the portion where the depth of cut of the tool into the workpiece 21 is large, obtained by superimposing 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. Also, in machining example 6, as shown in Figure 13(d), the view from the Z-axis direction... Sometimes, regions Qi1 and Qi2 coexist.

[0072] Figure 13(e) shows the machining process for example 7, where the workpiece 21 is machined into a roughly square shape by outer diameter machining with a vibration frequency of 4. In machining example 7, the tool vibrates 4 times for each rotation of the workpiece 21, and the outer surface is machined into a roughly square shape. At this time, when viewed from the Z-axis direction, the machining trajectory To of the workpiece 21 is always the same regardless of the number of rotations, so only region Qo1 is shown in Figure 13(e).

[0073] Figure 13(f) shows the process of machining a workpiece 21 into a roughly square shape by internal diameter machining with a vibration frequency of 4, as machining example 8. In machining example 8, the tool vibrates 4 times for each rotation of the workpiece 21, and the inner surface is machined into a roughly square shape. 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 rotations, so only region Qi1 is shown in Figure 13(f).

[0074] As described above, according to this embodiment, when viewed from the direction of the rotation axis of the workpiece, the outer and inner surfaces of the workpiece can be efficiently machined into a substantially regular polygon by turning. In this embodiment, when machining a workpiece into a regular n-gon, the rotation mechanism and vibration mechanism are controlled in conjunction so that the tool vibrates at a frequency of n / m when the constant rotation period of the workpiece is m rotations. In this case, 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. Therefore, according to this embodiment, for example, the workpiece can be machined into a substantially regular hexagon every 5 rotations with a vibration frequency of 1.2, or the workpiece can be machined into a substantially regular heptagon every 4 rotations with a vibration frequency of 1.75.

[0075] As described above, by driving the rotation mechanism and vibration mechanism so that the vibration frequency is n / m, the tool is positioned at the same location in the vibration direction V1 every constant rotation period m of the workpiece, and the workpiece is machined into a roughly regular n-gon shape every m rotations of the workpiece. In addition, by driving the tool movement mechanism in conjunction with the rotation mechanism and vibration mechanism, the workpiece can be machined into a roughly regular polygon in multiple passes.

[0076] 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 positioned at the upper amplitude limit AU. Similarly, in the inner diameter machining according to this embodiment, each vertex of the regular polygon of the workpiece is machined when the tool is positioned at the upper amplitude limit AU. The control unit 15 controls the rotation mechanism and the movement mechanism so that the workpiece is cut by the tool in this positional relationship, thereby machining the workpiece into a substantially regular polygon.

[0077] 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 surface of a workpiece into an equilateral triangle, the vibration frequency can be set to 3 (see Figure 13(a)) or to 1.5 (see Figure 13(c)). Since there is a limit to the vibration speed of the vibration mechanism, increasing the rotation period m to reduce the vibration frequency n / m allows the rotation speed (peripheral speed) of the workpiece to be increased, reducing the machining time and improving productivity.

[0078] <Other Embodiments> The embodiments described above are merely examples, and this disclosure may be modified as appropriate without departing from its essence. Furthermore, the processes and means described in this disclosure can be freely combined and implemented as long as no technical inconsistencies arise. For example, in the embodiments described above, a cylindrical workpiece was machined while rotating it, but the workpiece is not limited to a cylindrical shape.

[0079] Furthermore, a process described as being performed by one device may be divided and executed by multiple devices. Alternatively, a process described as being performed by different devices may be performed by one device. It's perfectly acceptable for it to be executed in that way. In a computer system, the hardware configuration used to implement each function can be flexibly changed. [Explanation of Symbols]

[0080] 10...Machine tool, 15...Control unit, 21...Workpiece (object to be cut), 31...Tool, S1...Rotation axis direction, V1...Vibration direction

Claims

1. The spindle to which the workpiece to be cut is attached, A rotating mechanism for rotating the main shaft, A tool holder for holding a tool used to cut the object to be cut, A moving mechanism that moves the spindle and the tool holder relative to each other in the direction of the rotation axis of the spindle, A vibration mechanism that vibrates the main spindle and the tool holder with a constant amplitude relative to each other in a vibration direction perpendicular to the rotation axis, The rotation mechanism and the control unit that controls the vibration mechanism A machine tool comprising the rotating mechanism, which rotates the spindle, and which moves the workpiece and the tool while vibrating them relative to each other at a constant amplitude using the moving mechanism and the vibrating mechanism, thereby cutting the workpiece, The control unit drives the rotation mechanism and the vibration mechanism so that the tool is positioned at the same location in the vibration direction at each constant rotation period of the spindle, and controls the rotation mechanism and the vibration mechanism so that the outer or inner surface of the workpiece is machined into a substantially regular polygon when viewed from the direction of the rotation axis. When the aforementioned constant rotation period is m rotations and the number of sides of the aforementioned approximately regular polygon is n, m is a natural number greater than or equal to 2, n is a natural number greater than or equal to 3, and m and n are relatively prime. The control unit is characterized by setting the vibration frequency of the vibration mechanism to n / m.

2. When the tool is positioned at the upper limit of the amplitude of the vibration waveform of the tool caused by the vibration mechanism, the depth of cut of the tool into the workpiece becomes larger compared to when the tool is positioned at the lower limit of the amplitude of the vibration waveform. The machine tool according to claim 1, characterized in that the control unit synchronously controls the moving mechanism and the vibration mechanism so that when the tool is positioned at the upper limit of the amplitude of the vibration waveform, the center of the sides of the substantially regular polygon is machined when the outer surface of the workpiece is being cut.

3. When the tool is located at the upper limit of the amplitude of the vibration waveform of the tool caused by the vibration mechanism, the Compared to when the tool is at the lower limit of the amplitude of the vibration waveform, the depth of cut of the tool into the workpiece becomes larger. The machine tool according to claim 1, characterized in that the control unit synchronously controls the moving mechanism and the vibration mechanism so that when the inner surface of the workpiece is being cut, the vertices of the substantially regular polygon are machined when the tool is at the upper limit of the amplitude of the vibration waveform.

4. The machine tool according to claim 1, characterized in that the moving mechanism is configured to allow the main spindle and the tool holder to move relative to each other in a direction parallel to the vibration direction.

5. The control unit is capable of controlling the operation of the moving mechanism. The machine tool according to claim 4, characterized in that when performing a first machining process to obtain a machined surface that is substantially a regular polygon when viewed from the direction of the rotation axis, and a second machining process to machine the machined surface to a shape similar to the machined surface when viewed from the direction of the rotation axis, the control unit controls the rotation mechanism, the moving mechanism, and the vibration mechanism so that the phase of the vibration waveform of the tool caused by the vibration mechanism with respect to the rotation of the spindle in the second machining process matches that of the first machining process.

6. The spindle to which the workpiece to be cut is attached, A rotating mechanism for rotating the main shaft, A tool holder for holding a tool used to cut the object to be cut, A moving mechanism that moves the spindle and the tool holder relative to each other in the direction of the rotation axis of the spindle, A vibration mechanism that vibrates the main spindle and the tool holder with a constant amplitude relative to each other in a vibration direction perpendicular to the rotation axis, A control device for a machine tool that, while rotating the spindle by the rotation mechanism, moves the workpiece and the tool while vibrating them relative to each other at a constant amplitude by the moving mechanism and the vibration mechanism, thereby machining the outer or inner surface of the workpiece into a substantially regular polygon when viewed from the direction of the rotation axis, The rotation mechanism and the vibration mechanism are driven so that the tool is positioned at the same location in the vibration direction at each constant rotation period of the main spindle. When the aforementioned constant rotation period is m rotations and the number of sides of the aforementioned approximately regular polygon is n, m is a natural number greater than or equal to 2, n is a natural number greater than or equal to 3, and m and n are relatively prime. A control device characterized by setting the frequency of the vibration mechanism to n / m.

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