Machine tool

Abstract

This machine tool comprises: a tool holding part for holding a tool; a workpiece holding part for holding a workpiece; and a drive control part for driving and controlling the tool holding part and the workpiece holding part so as to perform: (i) first screw machining for cutting the workpiece along a rotation axis of the workpiece from a first cutting position on an axis orthogonal to the rotation axis of the workpiece so as to follow the rotation axis, the first screw machining cutting the workpiece by relatively vibrating the tool on an axis different from the rotation axis; and (ii) second screw machining for linearly cutting the workpiece along the rotation axis of the workpiece from the first cutting position so as to follow the rotation axis.

Description

machine tools

[0001] The technical field of the present application relates to a method for machining a screw and a machine tool capable of machining a screw.

[0002] Generally, in machine tools that perform turning, the cutting tool and workpiece are rotated relative to each other along the circumferential direction of the workpiece while the workpiece is fed relatively along the rotation axis of the workpiece to machine the workpiece into a desired shape. This type of machining can produce long, continuous chips, which tend to remain in the machining chamber and require regular chip cleaning. This increases the time required to machine the workpiece. Furthermore, if long chips remain in the machining chamber, they may damage the workpiece or other components.

[0003] Therefore, in the machine tool disclosed in Patent Document 1, chips are broken up by vibrating the machine during turning.

[0004] U.S. Patent No. 10,610,993 (Patent No. 6,914,840)

[0005] However, in the machining method of Patent Document 1, as shown in FIG. 6, a large load is applied to the tool due to vibration, which increases the frequency of tool replacement.

[0006] Therefore, the present invention provides a machining path, machining method, machine tool, etc. for thread machining that reduces the load on the tool.

[0007] Fig. 1 is an explanatory diagram for explaining an example of a schematic configuration of a machine tool; Fig. 2 is a block diagram showing the configuration of the machine tool; Fig. 3 is an example of a diagram showing the movement trajectory of a machining point of a tool relative to a position change in the Z axis; Fig. 4 is an example of a diagram showing the movement trajectory of a machining point of a tool relative to a position change in the Z axis; Fig. 5 is an example of a diagram showing the movement trajectory of a machining point of a tool relative to a position change in the Z axis; Fig. 6 is a diagram showing a conventional machining method

[0008] (Machine Tool) FIG. 1 is a schematic diagram showing the main components of a machine tool 1. This machine tool 1 is an NC lathe that performs turning by rotating a workpiece W and bringing a cutting tool 3 into contact with the workpiece W. Examples of such turning include external diameter turning, internal diameter turning, drilling, profile taper turning, grooving, end face turning, and thread cutting. FIG. 1 shows a state in which a thread cutting operation is being performed on a machine tool capable of these operations. When performing thread cutting, this machine tool 1 moves the workpiece W and the cutting tool 3 relatively on the Z axis and vibrates the cutting tool 3 in the radial direction of the workpiece W based on program code.

[0009] In the following description, the rotation axis of the workpiece W is defined as the Z axis, the vertical direction perpendicular to the Z axis is defined as the X axis, and the direction perpendicular to both the X axis and the Z axis (the direction perpendicular to the plane of the paper in FIG. 1) is defined as the Y axis. In FIG. 1, the radial direction of the workpiece W and the X axis are parallel to each other.

[0010] When applying vibration in thread cutting, it is preferable to vibrate the tool 3a or the workpiece parallel to the X-axis, but this is not limitative and vibration may be parallel to the Y-axis or in a direction having components of the X-axis and Y-axis. Furthermore, when applying vibration treatment in thread cutting, it is preferable to vibrate in the radial direction of the workpiece W, but any direction including a radial vibration component will suffice. For example, in the case of FIG. 1, vibration may be in a direction having components of the X-axis and Z-axis.

[0011] The machine tool 1 includes a spindle 2 (an example of a workpiece holder) having a chuck mechanism 6 at its tip, a headstock 5 that rotatably holds the spindle 2, a cutting tool 3, and a tool holder 4 (e.g., a tool rest or tool spindle) that holds the cutting tool 3 movably in the X-, Y-, and Z-axes. The headstock 5 incorporates a spindle drive unit 11 ( FIG. 2 ) that rotates the spindle 2 and is fixed to the bed of the machine tool 1. The spindle drive unit 11 ( FIG. 2 ) is configured, for example, by a servo motor. The spindle drive unit 11 functions as a rotation drive unit that rotates the cutting tool 3 and the workpiece W relative to each other in the circumferential direction of the workpiece W. In this embodiment, machining is performed using the existing drive units of the workpiece holder and the tool holder, without installing a new vibration mechanism for applying vibration in the machine tool. In other words, machining is performed by controlling the existing drive units of the workpiece holder and the tool holder, while the workpiece holder and the tool holder are moved relative to each other with the vibration movement superimposed thereon. The machining method disclosed in Patent Document 1 has large vibration swings that propagate to the machine tool itself, degrading the quality of thread machining. Therefore, the machine tool is mechanically reinforced to prevent the vibration from propagating. Alternatively, a separate vibration mechanism that prevents vibration from propagating is attached to the machine tool. However, the machining method of this embodiment makes it possible to perform machining without the need to attach a separate vibration mechanism.

[0012] 1 shows a cutting tool 3 which is a general-purpose tool 3a for a lathe, and which is held by a tool holder 4.

[0013] The tool holder 4 is driven in each axial direction by a tool feed drive unit 10 (FIG. 2). The tool feed drive unit 10 has an X-axis feed mechanism, a Y-axis feed mechanism, and a Z-axis feed mechanism that perform feed operations on the X-axis, Y-axis, and Z-axis. Each feed mechanism is configured, for example, by a combination of a ball screw and a servo motor.

[0014] (Configuration of machine tool and peripheral devices) As shown in Figure 2, the machine tool 1 has a first control device 20 that controls the movement of the tool 3a and workpiece W. The first control device 20 has a storage unit 21 that stores programs and the like for executing (interpreting) NC programs and sending drive signals to the spindle drive unit 11 and tool feed drive unit 10, and a drive control unit 22 that has an OS and the like that makes the programs function. In the machine tool 1, the spindle drive unit 11 and tool feed drive unit 10 receive signals from the first control device 20 and move the workpiece W and tool 3a.

[0015] The drive control unit 22 of the first control device 20 executes (analyzes) the NC program stored in the memory unit 21 to create operation commands from the operation codes of the NC program, and drives the spindle drive unit 11 and the tool feed drive unit 10 based on the operation commands. The drive control unit 22 is a functional unit that reads and executes the NC program stored in the memory unit 21, and while sequentially reading the NC program, recognizes (analyzes) the written NC code and controls the drive based on the written program. If the recognized NC code relates to rotation control of the spindle 2, the drive control unit 22 transmits a corresponding control signal to the spindle drive unit 11. Furthermore, if the recognized NC code relates to feed control of the tool holder 4, the drive control unit 22 transmits a corresponding control signal to the tool feed drive unit 10.

[0016] The spindle drive unit 11 controls the rotation of the spindle 2 , for example, the rotation speed and the forward / reverse direction of rotation, in accordance with a control signal sent from the drive control unit 22 .

[0017] Similarly, the tool feed drive unit 10 controls the operation of the tool holding unit 4 in accordance with a control signal transmitted from the drive control unit 22, for example, controls the speed (feed speed) at which the tool 3a is moved (speed control), and also controls the movement position of the cutting edge of the tool 3a (position control).

[0018] Furthermore, the storage unit 21 may store a parameter (for example, a vibration amplitude of 0) for controlling so that vibration is not applied to a movement path that applies vibration in the NC program when the NC program into which a thread cutting command is inserted is executed. The first control device may be configured to execute the NC program sequentially in block order while checking the values ​​of the parameters stored in the storage unit 21.

[0019] The first control device 20 executes these drive control functions and storage functions by processing them using a calculation means such as a CPU or an LSI.

[0020] Machine tool 1 further has a second control device 40 that controls the display on display unit 32 of the operation panel. Second control device 40 has a storage unit 42 that stores programs and the like that control the display on the screen of operation panel 30, a display control unit 41 that has an OS and the like that makes the programs function, and a programming unit 43 that creates NC programs.

[0021] The memory unit 42 of the second control device 40 stores programs for supporting NC program creation and programs related to the screen display of the input screen 35 for supporting such creation. The display control unit 41 of the second control device 40 has an OS that runs these programs and can support NC program creation on the screen display while running these programs. The programming unit 43 creates an NC program based on information set by conditions, etc., on the NC program creation support screen. The programming unit 43 may also have a function for directly writing NC code, such as G code or M code, to directly create or edit an NC program, or a function (code insertion unit 44) for inserting G code or M code into a specific line or block of an NC program.

[0022] The second control device 40 processes and executes these storage functions, display control functions, and programming functions using a calculation means such as a CPU or LSI that is different from the calculation means of the first control device 20.

[0023] The operation panel 30 is provided with a program execution button 31 and a display unit 32 (e.g., a touch panel) that displays a screen for displaying information about the program and the machine tool (e.g., coordinates), etc. An operator can perform operations such as various settings related to machining and creating NC programs on the operation panel while checking the display on the display unit 32.

[0024] The drive control unit 22 starts executing the NC program when the program execution button 31 on the operation panel 30 of the machine tool 1 is pressed. The drive control unit 22 reads the NC program stored in the memory unit 21. Then, the drive control unit 22 controls the spindle drive unit 11 and the tool feed drive unit 10 based on the read NC program to perform machining.

[0025] In thread cutting, the spindle 2 holding the workpiece W is rotated around the Z-axis by the spindle drive unit 11. Then, the position of the tool holder 4 on the X-axis is defined in the NC program by the tool feed drive unit 10, so that the depth of cut of the tool 3a on the X-axis can be set to a predetermined value. In this state, the tool feed drive unit 10 feeds and drives the tool holder 4 in the Z-axis direction, moving the tool 3a relatively along a line parallel to the rotation axis of the workpiece W. In Figure 1, the movement path (tool path) of the cutting edge of the tool 3a is shown by a dashed line. As shown in FIG. 1 , after the cutting edge of tool 3a is positioned at a start position (Xa, Za), it moves at a predetermined cutting feed rate in the X-axis direction to a first cutting position (X1, Za). It then moves to a position (X1, Z1) at a feed rate per revolution (mm / rev) corresponding to the thread pitch to thread the workpiece W. It then moves to a relief position (Xa, Zb) and returns to the start position (Xa, Za), completing the first thread cutting. Next, while cutting into the workpiece W by a predetermined cutting depth, tool 3a is moved along a similar path to perform multiple thread cutting operations on the workpiece W—seven times in this example. The tool path for multiple thread cutting operations is as follows:a) First thread cutting operation (First thread cutting operation) (Xa,Za) → (X1,Za) → (X1,Z1) → (Xa,Zb) → (Xa,Za) b) Second thread cutting operation (Second thread cutting operation) (Xa,Za) → (X2,Za) → (X2,Z2) → (Xa,Zb) → (Xa,Za) c) Third thread cutting operation (Third thread cutting operation) (Xa,Za) → (X3,Za) → (X3,Z3) → (Xa,Zb) → (Xa,Za) d) Fourth thread cutting operation (Fourth thread cutting operation) (Xa,Za) → (X4,Za) → (X4,Z4) → (Xa,Zb) → (Xa,Za) e) Fifth thread cutting operation (Fifth thread cutting operation) (Xa,Za) → (X5,Za) → (X5,Z5) → (Xa,Zb) → (Xa,Za) f) Sixth thread cutting (sixth thread cutting) (Xa,Za) → (X6,Za) → (X6,Z6) → (Xa,Zb) → (Xa,Za) g) Seventh thread cutting (seventh thread cutting) (Xa,Za) → (X7,Za) → (X7,Z7) → (Xa,Zb) → (Xa,Za) Thus, during thread cutting, the relative movement of tool 3a is performed multiple times. The dotted line in Figure 1 indicates the movement trajectory of the machining point of tool 3a. In this way, the operation of cutting the thread tooth surface is performed multiple times using different cutting paths that are not the same. In other words, the program is not written so that the movement trajectory of the machining point follows the same cutting path. The dotted line in FIG. 1 is a straight line, representing the movement trajectory of the machining point of the tool 3a in conventional thread cutting. In Patent Document 1, a vibration component is added to all of this machining, so the infeed position must also be newly set. This is because the focus is solely on preventing the generation of long chips. In contrast, in this embodiment, a vibration component is sometimes added to this movement trajectory and sometimes not, because the load on the tool and machine tool is taken into consideration. In this embodiment, a vibration component is added to this movement trajectory. Therefore, if vibration is added to a linear movement trajectory such as the dotted line in FIG. 1, the movement trajectories for the first, third, and fifth vibration cutting passes in FIG. 3 are obtained. On the other hand, the second, fourth, and sixth cutting passes in FIG. 3 are linear cuts without the addition of a vibration component. Furthermore, in the first and second cutting passes in FIG. 3, the tool 3a is moved relative to the tool 3a along the Z axis from the same infeed position.Similarly, in the third and fourth machining operations in FIG. 3, the tool 3a is relatively moved in the Z-axis direction from the same cutting position.

[0026] To reiterate, in conventional thread cutting, if the thread cutting portion of one circumference indicated by the dotted line in FIG. 1 is considered to be one cutting, the cutting amount of the tool 3 a on the X axis (radial direction of the workpiece) relative to the workpiece W is kept constant while one cutting is being performed (thread cutting portion).

[0027] In contrast, the NC program for thread cutting in this embodiment is an NC program that includes code for changing the amount of cutting in the X-axis (radial) direction of the tool 3a during one cutting operation. In particular, it is preferable to include G-code or M-code in the NC program, in which the amount of cutting periodically changes, as in the first vibration cutting operation shown in Figure 3. Instead of G-code or M-code, codes related to vibration, such as a code combining symbols and numbers like "#20240327" or the name of a function like "frequency," may also be used.

[0028] (NC Program) An outline of how to create an NC program including a code related to vibration will be described below, specifically, how to create an NC program for thread machining.

[0029] Figure 3 is a diagram showing the machining path of thread cutting when the NC program created in this embodiment is executed by machine tool 1. The vertical axis of the diagram shows the thread cutting position on the X axis of the machining point of tool 3a, and the horizontal axis shows the movement amount on the Z axis of the machining point of tool 3a (position of the machining point of tool 3a) in terms of the number of revolutions of the work spindle. With existing vibration-free thread machining, a thread can be machined by performing the linear machining shown in Figure 3 three times. Even if one finish machining is added, a thread can be machined with four linear machining operations.

[0030] In contrast, as shown in this figure, the drive control unit 22 of this embodiment executes the program seven times to machine the thread by controlling the relative movement between the workpiece W and the tool 3a based on the NC program.

[0031] Based on the NC program, the drive control unit 22 moves the tool holder 4 relative to the workpiece in the Z-axis direction at a constant speed while vibrating it in the X-axis direction (the workpiece radial direction) during the first, third, and fifth cuts (vibration machining). As a result, the machining point trajectory of the tool 3a held by the tool holder 4 (the trajectory of the tip of the tool 3a in FIG. 1) traces a sinusoidal vibration waveform in the XZ plane. Based on the NC program, the drive control unit 22 only moves the tool holder 4 relative to the workpiece in the Z-axis direction at a constant speed without vibrating it in the X-axis direction (the workpiece radial direction) during the second, fourth, and sixth cuts (non-vibration machining). In FIG. 3, the second, fourth, and sixth cuts are performed by moving the tool holder 4 in the Z-axis direction from the same cut position as the first, third, and fifth cuts, respectively. In this case, macro programming is performed using the G code and M code of the NC program to repeat vibration machining and non-vibration machining (linear machining) six times, and the machining path is as shown in Figure 3. In other words, the drive control unit 22 accurately executes the contents of the command codes of the NC program.

[0032] On the other hand, when executing the seventh (final) cutting command code of the NC program, the drive control unit 22 only moves the tool holder 4 in the Z-axis direction but does not vibrate the tool holder 4. In other words, the NC program command code for the seventh (final) cutting is processed by setting the address value related to the vibration amplitude of the tool 3a to 0, deleting the address related to the vibration of the tool 3a, or ignoring the address related to the vibration of the tool 3a. When the parameter value in the first control device is set to 0 and a finish thread machining block (which may be NC code containing only the X-coordinate) is read in the NC program, the first control device can also control the spindle drive unit and the tool feed drive unit so that they do not vibrate relative to each other on the X-axis. The NC program command code for the seventh (final) cutting sets the X-coordinate address, which determines the position of the tool holder 4, to a constant value so that the position of the tool 3a in the X-axis direction is maintained constant. For example, if the X-coordinate position of the cutting in the NC program corresponding to the seventh (final) infeed machining is the same as the thread root diameter position, the movement trajectory of the machining point during thread machining at that X-coordinate position can be controlled so that vibration is not applied. As a result, the trajectory of the machining point of the tool 3a held by the tool holder 4 traces a straight line (a trajectory without vibration in the X-axis direction) in the XZ plane, with a constant position on the X-axis. This prevents the shape accuracy of the finished surface from being reduced due to vibration of the tool 3a. This finishing pass without vibration in the X-axis direction may be performed multiple times, rather than just the last of multiple infeed machining passes. In this embodiment, since the first half of the thread machining is performed with vibration and the second half is not, vibration application does not need to be disabled. For example, if the X-coordinate position of the cutting in the NC program is the same as the thread root diameter position, the lower limit of the movement trajectory may be controlled to be the X-coordinate of the thread root diameter position, as in the fifth (vibration) thread machining pass in which vibration is applied. Furthermore, the finishing pass may be a zero cut.

[0033] It is also possible to use a configuration in which the workpiece holder 4 moves in the Z-axis direction instead of the configuration in which the tool holder 4 moves in the Z-axis direction. The tool path for thread cutting in Figure 3 is as follows. If X0 is the outer position of the thread (thread X coordinate), the cutting depth is X0 - X1 (= X1 - X3 = X5 - X3). The root diameter position of the thread is the thread finishing position (thread finishing X coordinate). Furthermore, no vibration is applied during the escape operation or return operation of the tool during thread cutting. These settings also reduce the load on the tool and machine tool. a) First thread cutting (first thread cutting) (Xa,Za) → (X1,Za) → with vibration → (X1,Z1) → without vibration → (Xa,Zb) → (Xa,Za) b) Second thread cutting (second thread cutting) (Xa,Za) → (X1,Za) → without vibration → (X1,Z2) → without vibration → (Xa,Zb) → (Xa,Za) c) Third thread cutting (third thread cutting) (Xa,Za) → (X3,Za) → with vibration → (X3,Z3) → without vibration → (Xa,Zb) → (Xa,Za) d) Fourth thread cutting (fourth thread cutting) (Xa,Za) → (X3,Za) → without vibration → (X3,Z4) → without vibration → (Xa,Zb) → (Xa,Za) e) Fifth thread cutting process (5th thread cutting process) (Xa,Za) → (X5,Za) → With vibration → (X5,Z5) → Without vibration → (Xa,Zb) → (Xa,Za) f) Sixth thread cutting process (6th thread cutting process) (Xa,Za) → (X5,Za) → Without vibration → (X5,Z6) → Without vibration → (Xa,Zb) → (Xa,Za) g) Seventh thread cutting process (7th thread cutting process) (Xa,Za) → (X5,Za) → Without vibration → (X5,Z7) → Without vibration → (Xa,Zb) → (Xa,Za)

[0034] Here, when performing cutting, the NC program is programmed so that there is a point where the vibration waveform (vibration machining) drawn by the tip of the tool 3a on the XZ plane comes into contact with the straight line (non-vibration machining). In Figure 3, the NC program is programmed so that the waveform showing the change in the cutting amount on the X axis of the tool 3a relative to the position change on the Z axis comes into contact with the vibration waveform on the XZ plane when cutting is performed before and after that (before and after the straight line machining pass).

[0035] For example, the vibration waveform of the tool tip during the third incision cutting and the linear movement trajectory of the tool tip during the fourth incision cutting, which is the next in the execution order, will be described. The third and fourth incisions are performed from the same incision position (X coordinate) relative to the radial direction of the thread (X axis). For example, the X coordinate command value of the NC program is the same. Therefore, these two thread cuttings may be programmed as a pair. That is, for the movement trajectories of two linear cuttings from the same incision position, vibration may be added to one linear cutting and not to the other linear cutting. The valley of the vibration waveform during the third incision cutting and the linear line during the fourth incision cutting are located at a position where they intersect. The vibration waveform is triangular, but may also be arc-shaped or wavy. The vibration waveforms for the first, third, and fifth incisions are in phase. That is, the phase difference between the waveforms in FIG. 3 is 0°. The phase difference is not limited to this; there may be a phase difference between the vibration waveforms. For example, the phase difference may be 180°, or may be set within a range of 90° to 270°. Although the first and second waveforms have the same period, this does not necessarily have to be the case. The chip-breaking effect is achieved as long as the movement trajectories of the two tools 3a in vibration machining and linear (non-vibration machining) contact at least one point. Patent Document 1 creates a path of no cutting action, but creating a path of no cutting action accelerates the tool movement because no cutting action occurs. Then, the tool collides with the workpiece again in an accelerated state, which increases the impact and accelerates tool wear. Therefore, it is preferable to create an NC program that sets a path of the tool tip that provides a point of contact or tangent overlap sufficient to break the chip.

[0036] By creating an NC program in this manner, when cutting with tool 3a is performed, there is no workpiece to be cut in this cutting, although it is a point at the contact point with the previous cutting. Therefore, the cutting operation of the workpiece with tool 3a ends, and chips are generated by the end point. This can be said to be chips that have been cut by the conventional chips. In other words, a non-cutting point where no cutting is performed by tool 3a is created. The existence of the non-cutting area means that the cutting point (cutting edge) of tool 3a is in contact with the workpiece but is not cutting, so the chips are broken. In response to this, the first control device reads a machining program including a command code corresponding to the first cutting position (e.g., the first and second cutting positions in Figure 3) and acquires information regarding the first cutting position. Then, when the first control device determines that this first cutting position is (i) a position closer to the thread root diameter position than the thread outer diameter position, and (ii) the same position as the thread root diameter position or a position closer to the thread outer diameter position than the thread root diameter position, it performs first thread machining (first machining in FIG. 3 ) in which the tool is vibrated relatively on an axis different from the rotation axis along the rotation axis of the workpiece to cut the workpiece. When the first control device determines that this first cutting position is (i) a position closer to the thread root diameter position than the thread outer diameter position, and (ii) a position closer to the rotation axis than the same position as the thread root diameter position, it performs linear machining without applying vibration.

[0037] As shown in Figure 4, by making the maximum cutting depth the same for each machining cycle, the load on the tool can be made uniform. As can be seen from Figure 4, by making the cutting depth (depth) the same for vibration machining (waveform) and non-vibration machining (straight line), the load on the tool can be made the same for each machining cycle, thereby extending the usable life of a single tool. This reduces the number of tool changes, thereby reducing the time when thread machining is unavailable due to tool changes, and therefore improving machining efficiency. Furthermore, with the machining shown in Figure 4, the maximum cutting depth can be adjusted simply by adjusting the amplitude, making it easier to predict tool wear and the timing and frequency of tool changes, thereby improving setup efficiency.

[0038] In this way, if an NC program including vibration-related code can be created, there is no need to install a separate high-pressure coolant device to break up chips, as was previously required. Furthermore, since the load on the tool when machining threads with vibration can be reduced, the tool can be used for a longer period of time than before, and the frequency of tool replacement can be reduced. This leads to reduced tool costs. Furthermore, because the tool replacement time is reduced, more time can be secured for machining threads with the machine tool than before.

[0039] Furthermore, in the thread cutting process shown in Figure 6, the vibration waveform has two peaks and three valleys per rotation of the workpiece spindle, resulting in high-speed vibration. Therefore, when performing the thread cutting process shown in Figure 6 with a conventional machine tool, the machine tool itself vibrates, resulting in a decrease in thread cutting quality. Therefore, when performing the thread cutting process shown in Figure 6 with a conventional machine tool, it was necessary to reinforce the structure to be vibration-resistant. Alternatively, measures such as installing a vibration mechanism to counter vibration were required. In the thread cutting process shown in Figure 5, the vibration waveform has two peaks and three valleys per four rotations of the workpiece spindle. By vibrating more slowly than in the thread cutting process shown in Figure 6, vibration can be prevented from being transmitted to the machine tool itself. As a result, it is possible to create an NC program for the thread cutting process shown in Figure 5 and execute the NC program on a current machine tool without taking measures such as reinforcing the conventional machine tool. It should be noted that the form is not limited to that shown in Fig. 5, and as long as there is one or less peaks or one or less bottoms of the waveform during one rotation of the workpiece spindle, the effect of vibration can be reduced compared to the machining shown in Fig. 6. Furthermore, although the vibration waveform is triangular, it is not limited to this and may be arc-shaped or so-called wavy.

[0040] W Workpiece 1 Machine tool 2 Spindle (workpiece holder) 3a Threading tool (tool) 4 Tool holder 10 Tool feed drive unit (feed drive unit) 11 Spindle drive unit (rotation drive unit) 23 Drive control unit (threading control unit)

Claims

1. A machine tool comprising: a tool holding unit that holds a tool; a work holding unit that holds a work; and a drive control unit that drives and controls the tool holding unit and the work holding unit to perform: (i) a first thread machining operation in which the work is cut along the rotation axis of the work from a first cutting position on an axis perpendicular to the rotation axis of the work, the first thread machining operation being a first thread machining operation in which the work is cut along the rotation axis of the work by vibrating the tool relatively on an axis different from the rotation axis; and (ii) a second thread machining operation in which the work is cut in a straight line along the rotation axis of the work from the first cutting position.

Images