Numerical control device, machine tool system, and numerical control method

Abstract

The present application provides a numerical control device, a machine tool system, and a numerical control method, which can suppress eccentricity due to relative vibration of a cutting tool and a workpiece, improve the accuracy of a finished shape, and suppress the influence on the front end of the cutting tool. The numerical control device causes a machine tool to perform thread cutting processing of forming a thread on a workpiece by performing multiple plunge processing on the workpiece by relatively moving the cutting tool and the workpiece, and includes: a drive unit that controls a main shaft that rotates the workpiece and a drive shaft of three axes; a vibration superimposition unit that superimposes vibration applied to two or more of the three axes on the relative movement of the cutting tool and the workpiece so as to relatively vibrate the cutting tool and the workpiece along a thread groove; and a thread cutting vibration adjustment unit that shifts the phase of the vibration by a vibration phase shift amount determined in advance each time with respect to the phase of the main shaft in the multiple plunge processing.

Description

TECHNICAL FIELD

[0001] The present application relates to a numerical control device, a machine tool system, and a numerical control method, particularly to a numerical control device, a machine tool system, and a numerical control method that make a machine tool perform thread cutting processing while cutting chips BACKGROUND

[0002] For example, a numerical control device of a machine tool that performs thread cutting processing while cutting chips is described in Patent Literature 1.

[0003] The control device of the machine tool described in Patent Literature 1 avoids long connected chips from being entangled on a workpiece or a cutting tool, and avoids damaging a machined surface of the workpiece, when performing thread cutting processing on the workpiece.

[0004] Specifically, the control device of the machine tool described in Patent Literature 1 is provided with a vibration setting unit that is configured to relatively move a workpiece and a cutting tool in a machining feed direction while relatively rotating the workpiece and the cutting tool, and to perform spiral cutting processing a plurality of times by relatively vibrating the workpiece and the cutting tool in a radial direction of the workpiece, thereby performing thread cutting processing, and to locally include, in a cutting processed portion at a predetermined cutting-in processing, a pattern of vibration at each cutting-in processing with vibration and a portion of other cutting-in processing that is completely cut.

[0005] Patent Literature 1: International Publication No. 2016 / 056526 pamphlet. SUMMARY

[0006] PROBLEMS TO BE SOLVED BY THE INVENTION

[0007] In thread cutting processing of a workpiece of a machine tool, in order to improve machining accuracy, it is desirable to suppress the influence of relative vibration of a cutting tool and a workpiece on the workpiece in rotation as much as possible. In this regard, the control device described in Patent Literature 1 is vibration of a single-axis cutting tool in the workpiece diameter direction, and thus there is a possibility that the workpiece in rotation will be eccentric. Therefore, it is desirable to suppress eccentricity due to relative vibration of a cutting tool and a machining object, to improve the accuracy of a finished shape, and to suppress the influence on the tip of the cutting tool.

[0008] MEANS FOR SOLVING THE PROBLEMS

[0009] (1) The first aspect of the present disclosure is a numerical control device that causes a machine tool to perform thread cutting processing of forming a thread on a machining object by causing a cutting tool to move relative to the machining object to perform a plurality of cutting-in processes on the machining object, the numerical control device comprising:

[0010] a drive unit that controls a main shaft that rotates the machining object and a drive shaft of a 3-axis;

[0011] a vibration superimposition section that superimposes vibrations applied to two or more of the three axes on the relative movement of the cutting tool and the work object in order to cause the cutting tool and the work object to vibrate relative to each other along the thread groove; and

[0012] a thread cutting vibration adjustment section that causes the phase of the vibration to be offset by a predetermined vibration phase offset amount each time in the plurality of the plunge machining.

[0013] (2) A second aspect of the present disclosure is a machine tool system including:

[0014] the numerical control device according to the above (1); and

[0015] a machine tool that relatively moves a cutting tool and a work object to perform plunge machining on the work object a plurality of times, thereby forming a thread on the work object.

[0016] (3) A third aspect of the present disclosure is a numerical control method of a numerical control device that causes a machine tool to perform thread cutting machining of relatively moving a cutting tool and a work object to perform plunge machining on the work object a plurality of times, thereby forming a thread on the work object,

[0017] in the numerical control method,

[0018] controls a drive shaft of a spindle that rotates the work object and a three-axis,

[0019] in order to cause the cutting tool and the work object to vibrate relative to each other along the thread groove, superimposes vibrations applied to two or more of the three axes on the relative movement of the cutting tool and the work object, and causes the phase of the vibration to be offset by a predetermined vibration phase offset amount each time in the plurality of the cutting machining.

[0020] Effects of the Invention

[0021] According to each aspect of the present disclosure, in thread cutting machining of a work object by a machine tool, by applying vibrations to two or more of an X-axis, a Y-axis, and a Z-axis, it is possible to suppress eccentricity due to relative vibration of a cutting tool and a work object, to improve the accuracy of a finished shape, and to suppress the influence on the front end of the cutting tool. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 is a block diagram that shows a machine tool system of an embodiment of the present disclosure.

[0023] Figure 2is a plan view showing a vibration direction of the cutting tool with respect to a thread groove direction of the workpiece from a viewpoint of the workpiece observing the cutting tool.

[0024] Figure 3 is a partial sectional view showing a vibration direction of the cutting tool with respect to the workpiece from a front end side of the workpiece.

[0025] Figure 4 is a conceptual view showing a locus of the cutting tool in one thread groove of the workpiece from a Z-axis direction after the first and second cutting-in processes.

[0026] Figure 5 is a conceptual view showing a locus of the cutting tool in the thread groove of the workpiece from the Z-axis direction at the first cutting-in process.

[0027] Figure 6 is a conceptual view showing a locus of the cutting tool in the thread groove of the workpiece from the Z-axis direction at the first cutting-in process.

[0028] Figure 7 is a conceptual view showing a locus of the cutting tool in the thread groove of the workpiece from the Z-axis direction at the first cutting-in process.

[0029] Figure 8 is a conceptual view showing a locus of the cutting tool in the thread groove of the workpiece from the Z-axis direction at the first cutting-in process.

[0030] Figure 9 is a conceptual view showing a locus of the cutting tool in the thread groove of the workpiece from the Z-axis direction at the first cutting-in process.

[0031] Figure 10 is a conceptual view showing a rotation of the workpiece without the cutting-in process in the workpiece from the Z-axis direction at the second cutting-in process.

[0032] Figure 11 is a conceptual view showing a rotation of the workpiece without the cutting-in process in the workpiece from the Z-axis direction at the second cutting-in process.

[0033] Figure 12 is a conceptual view showing a locus of the cutting tool in the thread groove of the workpiece from the Z-axis direction at the second cutting-in process.

[0034] Figure 13 is a conceptual view showing a locus of the cutting tool in the thread groove of the workpiece from the Z-axis direction at the second cutting-in process.

[0035] Figure 14 is a conceptual view showing a locus of the cutting tool in the thread groove of the workpiece from the Z-axis direction at the second cutting-in process.

[0036] Figure 15 is a conceptual diagram showing a locus of a cutting tool in a thread groove of a workpiece when viewed from the Z-axis direction at the time of the second plunge-cut machining.

[0037] Figure 16 is a conceptual diagram showing a locus of a cutting tool in one thread groove of a workpiece when viewed from the Z-axis direction at the time of the first and second plunge-cut machining.

[0038] Figure 17 is a conceptual diagram showing a locus of one thread groove after the first and second plunge-cut machining when the cutting angle θ is 90°.

[0039] Figure 18 is a conceptual diagram showing a locus of one thread groove after the first and second plunge-cut machining when the cutting angle θ is 80°.

[0040] Figure 19 is a conceptual diagram showing a locus of one thread groove after the first and second plunge-cut machining when the cutting angle θ is 45°.

[0041] Figure 20 is a conceptual diagram showing a locus of one thread groove after the first and second plunge-cut machining when the cutting angle θ is 0°. DETAILED DESCRIPTION

[0042] Hereinafter, an embodiment of the present disclosure will be described in detail using the drawings.

[0043] Figure 1 is a block diagram showing a machine tool system of an embodiment of the present disclosure.

[0044] As shown in Figure 1 , the machine tool system 10 is provided with a machine tool 100 and a numerical control device 200. Further, the numerical control device 200 can also be included in the machine tool 100.

[0045] First, the machine tool 100 will be described.

[0046] As shown in Figure 1 , the machine tool 100 is provided with a linear servo motor 101, a spindle table 102, a spindle motor 103, and a workpiece 104. The spindle motor 103 rotates the workpiece 104, which is a machining target, installed on a rotation shaft by means of a chuck not shown. In addition, the linear servo motor 101 moves the spindle table 102, on which the spindle motor 103 is installed, in the X-axis direction and the Y-axis direction. Figure 1The workpiece 104 is moved in the feed direction of the Z-axis by the linear servo motor 101. In addition, the linear servo motor 101 and the movement of the workpiece 104 in the feed direction are superimposed to reciprocate the workpiece 104 in the Z-axis direction. The cutting tool 110 is moved in the feed direction of the workpiece 104 to perform a plunge cut on the leading end of the rotating workpiece 104 to form a thread. The thread is formed by performing a plurality of plunge cuts.

[0047] In addition, the machine tool 100 is provided with a linear servo motor 105, a support table 106, a support column 107, a linear servo motor 108, a tool table 109, and a cutting tool 110. The linear servo motor 105 reciprocates the support table 106 in the Y-axis direction, which is not shown. The cutting tool 110 is a turning tool or the like that performs a plunge cut on the rotating workpiece 104. The support column 107 is provided on the support table 106. The linear servo motor 108 is installed on the side surface of the support column 107 to reciprocate the tool table 109, on which the cutting tool 110 is installed, in the X-axis direction.

[0048] In addition, the reciprocation in the X-axis direction, the reciprocation in the Y-axis direction, and the reciprocation in the Z-axis direction correspond to the vibration in the X-axis direction, the vibration in the Y-axis direction, and the vibration in the Z-axis direction, respectively. Hereinafter, the reciprocation will be referred to as the vibration.

[0049] The workpiece 104 is rotated by the spindle motor 103 and moved in the feed direction of the Z-axis by the linear servo motor 101. In addition, the workpiece 104 is vibrated in the Z-axis direction by the linear servo motor 101, and as a result, the cutting tool 110 is relatively vibrated in the Z-axis direction with respect to the workpiece 104. Furthermore, the cutting tool 110 is vibrated in the Y-axis direction by the linear servo motor 105 and in the X-axis direction by the linear servo motor 108. By cooperating the movement in the feed direction of the Z-axis and the vibration in the Z-axis direction of the rotating workpiece 104 with the vibration in the X-axis direction and the vibration in the Y-axis direction of the cutting tool 110, the cutting tool 110 performs a thread cutting process on the workpiece 104. In the following description, the vibration in the Z-axis direction of the cutting tool 110 will be described by vibrating the workpiece 104 in the Z-axis direction by the linear servo motor 101 to vibrate the cutting tool 110 in the Z-axis direction with respect to the workpiece 104.

[0050] The vibration in the X-axis direction, the vibration in the Y-axis direction, and the vibration in the Z-axis direction of the cutting tool 110 are shown in Figure 2 and Figure 3 .

[0051] Figure 2 is a plan view showing the vibration direction of the cutting tool 110 in the thread groove direction of the workpiece 104 when the workpiece 104 is viewed from the side of the cutting tool 110. In Figure 2 , the cutting tool 110 is not shown.Figure 3 is a partial cross-sectional view showing a vibration direction of the cutting tool 110 with respect to the workpiece 104 as viewed from the front end side of the workpiece 104. Figure 2 The direction of travel of the tool shown indicates a direction in which the cutting tool 110 is relatively moved with respect to the workpiece 104 by moving the workpiece 104 in the feed direction of the Z axis by using the linear servo motor 101. In Figure 3 and Figure 4 In the and, the cutting tool 110 is represented by a triangle for simplicity.

[0052] As shown in Figure 2 , the cutting tool 110 vibrates in the Y axis direction and the Z axis direction, and the vibration direction is the same as the thread groove direction. As shown in Figure 3 , the cutting tool 110 vibrates in the X axis direction in addition to the vibration in the Y axis direction and the Z axis direction shown in Figure 2 . As shown in Figure 3 , the chip is cut off at a portion where the front end of the cutting tool 110 reaches the outer peripheral surface of the workpiece 104.

[0053] Figure 4 is a conceptual diagram showing the trajectory of the cutting tool in one thread groove of the workpiece after the first and second plunge machining as viewed in the Z axis direction. The shape of the first and second plunge machining is shown in Figure 4 , but in fact, the plunge machining is repeatedly performed the same as the first and second plunge machining until it becomes a circle having a diameter set to the trajectory in one thread groove. Figure 4 The auxiliary circle of shows the circumference of the workpiece 104 and the maximum machining depth machined in the first plunge machining. The number of times of the plunge machining is set by performing the thread cutting machining by performing several times of the plunge machining.

[0054] The cutting tool 110 forms the shape of the first and second plunge machining shown in Figure 4 by machining the workpiece 104.

[0055] The motor that moves the workpiece 104 in the feed direction of the Z axis and vibrates in the Z axis direction and the motor that vibrates the cutting tool 110 in the directions of the X axis and the Y axis can also be a servo motor connected to a ball screw instead of the linear servo motor 101, the linear servo motor 108, and the linear servo motor 105.

[0056] Next, the numerical control device 200 will be described.

[0057] As shown in Figure 1As shown, the numerical control device 200 includes a parsing processing section 201, an interpolation processing section 202, an acceleration / deceleration processing section 203, a control command output section 204, and a drive section 205. The interpolation processing section 202 includes a vibration superimposition section 2021 and a vibration adjustment section 2022.

[0058] The parsing processing section 201 parses a machining program including one or more program blocks on a program block basis, reads out a movement path and a feed speed, generates a movement command, and outputs it to the interpolation processing section 202. In addition, the parsing processing section 201 reads out a vibration command from the machining program, generates a vibration condition, and outputs it to the interpolation processing section 202.

[0059] In the interpolation processing section 202, the vibration superimposition section 2021 calculates a command movement amount of movement at a feed speed designated during a control cycle, i.e., a processing cycle, of the numerical control device 200, calculates a vibration movement amount during the processing cycle for vibrating the cutting tool 110 and the workpiece 104 using the vibration command, and further calculates a superimposed movement amount by superimposing the vibration movement amount and the command movement amount. Specifically, the vibration superimposition section 2021 calculates the superimposed movement amount in a manner that superimposes vibration in which two of the three drive axes, i.e., the X-axis and the Z-axis, or all of the three drive axes, i.e., the X-axis, the Y-axis, and the Z-axis, are synchronized, on the relative movement of the cutting tool 110 and the workpiece 104.

[0060] By vibrating two of the three drive axes, i.e., the X-axis and the Z-axis, or all of the three drive axes, i.e., the X-axis, the Y-axis, and the Z-axis, it is possible to suppress eccentricity due to the relative vibration of the cutting tool and the workpiece, to improve the accuracy of the finish-machined shape, and to suppress the influence on the front end of the cutting tool. For example, as shown in Figure 1 In the case where the vibration is only the X-axis vibration in the radial direction of the workpiece 104, the force is applied in parallel with the radial direction of the workpiece. However, if the X-axis, the Y-axis, or the Z-axis, or the X-axis, the Y-axis, and the Z-axis are vibrated, and vibrated in the direction of the thread groove as shown in Figure 2 , it is possible to disperse the force in the radial direction of the workpiece, and to suppress eccentricity.

[0061] The vibration adjustment section 2022 shifts the phase of the vibration by a predetermined vibration phase shift amount with respect to the phase of the spindle in each of the plurality of plunge cutting processes. For example, the vibration adjustment section 2022 sets the phase of the vibration in the second plunge cutting process in an opposite relationship to the phase of the vibration in the first plunge cutting process, and vibrates in a manner in which the plunge cutting process is started from the start of the return motion of the vibration in the first plunge cutting process and the plunge cutting process is started from the start of the forward motion of the vibration in the second plunge cutting process. Here, the return motion of the vibration refers to a motion in which the tip of the cutting tool 110 approaches the outer peripheral surface of the workpiece 104, and the forward motion of the vibration refers to a motion in which the tip of the cutting tool 110 moves away from the outer peripheral surface of the workpiece 104. The operation of the vibration adjustment section 2022 will be described in detail later.

[0062] The acceleration / deceleration processing section 203 converts the superimposed movement amounts of the respective drive shafts, which have been adjusted by the vibration phase shift amount, output from the interpolation processing section 202, into movement commands for each processing cycle taking acceleration / deceleration into account, in accordance with a predetermined acceleration / deceleration pattern.

[0063] The control command output section 204 outputs the movement commands output from the acceleration / deceleration processing section 203 as control commands to the drive section 205.

[0064] The drive section 205 controls the spindle that rotates the workpiece 104, and the Z-axis that moves and vibrates the workpiece 104, the X-axis that vibrates the cutting tool 110, and the Y-axis that vibrates the cutting tool 110, in accordance with the control commands. The drive section 205 includes a spindle control section that controls the spindle motor 103 that rotates the workpiece 104, and a Z-axis servo control section that controls the linear servo motor 101 that moves and vibrates the workpiece 104 in the feed direction of the Z-axis. In addition, the drive section 205 includes an X-axis servo control section that controls the linear servo motor 108 that vibrates the cutting tool 110 in the X-axis direction, and a Y-axis servo control section that controls the linear servo motor 105 that vibrates the cutting tool 110 in the Y-axis direction. These control sections are well known, and therefore the illustration and description thereof are omitted.

[0065] The above describes the functional blocks included in the numerical control device 200.

[0066] To realize these functional blocks, the numerical control device 200 is provided with an arithmetic processing device such as a CPU (Central Processing Unit). In addition, the numerical control device 200 is also provided with an auxiliary storage device such as an HDD (Hard Disk Drive) in which various control programs such as application software and an OS (Operating System) are stored, and a main storage device such as a RAM (Random Access Memory) for storing data temporarily required for the arithmetic processing device to execute programs.

[0067] Further, in the numerical control device 100, the arithmetic processing device reads the application software and the OS from the auxiliary storage device, and performs arithmetic processing based on these application software and OS while expanding the read application software and OS in the main storage device. In addition, various hardware provided in each device is controlled according to the arithmetic processing result thereof. Thereby, the functional blocks of the present embodiment are realized. That is, the present embodiment can be realized by cooperation of hardware and software.

[0068] In the case where the arithmetic processing amount of the numerical control device 200 is large, for example, a GPU (Graphics Processing Unit) is mounted in a personal computer, and when the GPU is used for arithmetic processing, high-speed processing can be performed by a technique called GPGPU (General-Purpose computing on Graphics Processing Units), and thus is preferable. Further, in order to perform processing at higher speed, a computer cluster is constructed using a plurality of computers loaded with such a GPU, and parallel processing is performed by the plurality of computers included in the computer cluster.

[0069] Next, the use of the cutting tool 110 will be described. Figures 5 to 16 The operations of the first cutting-in processing and the second cutting-in processing will be described. In the first cutting-in processing, the cutting tool 110 is moved to the position of the thread groove of the workpiece. Figures 5 to 16 In the first cutting-in processing, the cutting tool 110 is moved to the position of the thread groove of the workpiece.

[0070] Figures 5 to 9 are conceptual diagrams each showing the trajectory of the cutting tool in the Z-axis direction observed from the thread groove of the workpiece at the time of the first cutting-in processing. Further, in the first cutting-in processing, only the vibration of the cutting tool in the X-axis direction and the Y-axis direction is shown, but as shown in Figures 5 to 9 Figure 2

[0071] In the first cutting-in processing, the cutting tool 110 is moved to the position of the thread groove of the workpiece. Figure 5 ​​As shown, the cutting tool 110 vibrates in a manner that the cutting process begins from the start of the return motion of the vibration. During the return motion of the cutting tool 110, the tip of the cutting tool 110 reaches the outer peripheral surface of the workpiece 104. The workpiece 104 is then cut into the workpiece from the tip by the cutting tool 110.

[0072] Next, as Figure 6 As shown, after the cutting tool 110 performs the forward movement, as Figure 7 The cutting tool 110 is shown to return.

[0073] Furthermore, such as Figure 8 As shown, the cutting tool 110 is moved to the desired position. This results in... Figure 9 The cutting tool is shown following its trajectory in a threaded groove.

[0074] exist Figures 5 to 9 The diagram shows the trajectory of the cutting tool in a threaded groove during one revolution of the workpiece 104, but the number of revolutions of the workpiece 104 is determined by the length of the portion forming the threaded groove. Therefore, during the first cut, the number of revolutions of the workpiece 104 determines the number of revolutions, and the threaded groove is formed in a helical shape.

[0075] Next, in the second cutting operation, the phase of the vibration is offset relative to the phase of the spindle by a predetermined vibration phase offset amount. Specifically, in this embodiment, the vibration adjustment unit 2022 sets the phase of the vibration in the second cutting operation to be opposite to the phase of the vibration in the first cutting operation, and vibrates in a manner that in the first cutting operation, the cutting operation begins from the start of the vibration's return motion, and in the second cutting operation, the cutting operation begins from the start of the vibration's forward motion. Then, the trajectory of the cutting tool 110 during the return motion in the second cutting operation is brought to the position of the trajectory of the cutting tool 110 during the switch from the forward motion to the return motion in the first cutting operation.

[0076] In the second cutting process, such as Figure 10 As shown, workpiece 104 is moved from... Figure 9 The trajectory of the threaded groove rotates, causing workpiece 104 to rotate half a revolution. Figure 11 The trajectory of the thread groove. The rotational motion without cutting is to change the phase of the second cutting relative to the phase of the first cutting, so that the starting position of the trajectory of the cutting tool 110 during the forward motion in the second cutting reaches the specified position of the trajectory of the cutting tool 110 during the first cutting.

[0077] After that, as Figure 12As shown, the cutting tool 110 vibrates in a manner that initiates the cutting process from the start of the forward vibration. Furthermore, in the following operation, the chips are cut off at the portion of the cutting tool 110 that reaches the outer peripheral surface during the return motion.

[0078] Next, as Figure 13 As shown, after the cutting tool 110 performs a return motion, as... Figure 14 As shown, the cutting tool 110 is moved forward.

[0079] And, as Figure 15 As shown, the cutting tool 110 is made to return. Thus, the desired result is obtained. Figure 16 The cutting tool is shown following a trajectory in a thread groove. Moreover, in the second entry machining, similarly to the first entry machining, the number of revolutions determined by the rotation of the workpiece 104 results in the thread groove being formed in a helical shape.

[0080] In the subsequent third entry machining, similar to the second entry machining, no entry machining is performed, and the workpiece 104 is rotated half a revolution. This rotational motion without entry machining is to change the phase of the entry machining of the third entry machining relative to the phase of the second entry machining, so that the starting position of the trajectory of the cutting tool 110 during the forward motion in the third entry machining reaches the predetermined position of the trajectory of the cutting tool 110 during the second entry machining. Through the rotational motion without entry machining in the third entry machining, the starting position of the trajectory of the third cutting tool 110 returns to the starting position of the trajectory of the first cutting tool 110. The vibration adjustment unit 2022 sets the phase of the vibration in the third entry machining to be opposite to the phase of the vibration in the second entry machining.

[0081] exist Figure 16 The diagram shows the shapes for the first and second cutting passes, but in reality, the cutting is performed until the trajectory in one thread groove becomes a circle of the set diameter. The number of cutting passes is set by performing the thread cutting process several times.

[0082] <Relationship between cutting angle and cutting path>

[0083] In the above explanation, the angle θ (hereinafter referred to as the cutting angle θ) of the vibration direction of the Y-axis of the cutting tool relative to the X-axis direction was fixed as constant. However, the cutting angle θ can be set arbitrarily within the range of 0°≤θ≤90°. Figures 17 to 20 These are conceptual diagrams representing the trajectory (cutting path) of a thread groove after the first and second entry machining when the cutting angle θ is 90°, 80°, 45°, and 0°.

[0084] In addition, although Figures 17 to 20The vibration of the Z-axis is not shown, but in fact, the cutting tool also relatively vibrates in the Z-axis direction with respect to the workpiece 104. When the cutting angle θ is 0°, the vibration of the cutting tool in the Y-axis direction disappears, and the vibration in the X-axis direction and the Z-axis direction, that is, the vibration of the 2-axis, occurs.

[0085] As shown in FIG. 6, the shape of the cutting path differs depending on the cutting angle θ. When the cutting angle θ is 0°, as shown in FIG. 7, the cutting path is an ellipse. Figures 17 to 20 Figure 20 As shown in FIG. 6, the shape of the cutting path differs depending on the cutting angle θ. When the cutting angle θ is 0°, as shown in FIG. 7, the cutting path is an ellipse.

[0086] The greater the cutting angle θ, the more the force in the radial direction of the workpiece 104 can be dispersed in a direction other than the radial direction of the workpiece, and thus the force in the radial direction of the workpiece 104 can be reduced. However, as shown in FIG. 8, the greater the cutting angle θ, the more the trajectory of the cutting tool becomes uneven, and the variation in the cutting load becomes uneven. Therefore, the cutting angle θ is adjusted in accordance with the machining conditions of the thread cutting machining. Figures 17 to 20

[0087] The respective constituent parts of the numerical control device 200 described above can be realized by hardware, software, or a combination thereof. In addition, the numerical control method performed by the respective constituent parts of the numerical control device 200 described above in cooperation with each other can also be realized by hardware, software, or a combination thereof. Here, the realization by software means the realization by a computer reading and executing a program.

[0088] The program can be stored using various types of non-transitory computer readable media and provided to a computer. The non-transitory computer readable media include various types of tangible storage media. Examples of the non-transitory computer readable media include a magnetic recording medium (for example, a hard disk drive), a magneto-optical recording medium (for example, a magneto-optical disk), a CD-ROM (Read Only Memory), a CD-R, a CD-R / W, and a semiconductor memory (for example, a mask ROM, a PROM (Programmable ROM), an EPROM (Erasable PROM), a flash ROM, and a RAM (random access memory)).

[0089] The above-described embodiments are suitable for the embodiments of the present application, but the scope of the present application is not limited to the above-described embodiments, and the present application can be implemented in various ways with various modifications without departing from the spirit of the present application.

[0090] ​​For example, in the above embodiment, the trajectory of the cutting tool 110 at the time of the return operation in the second cutting-in process reaches the position where the trajectory of the cutting tool 110 at the time of the switch from the forward operation to the return operation in the first cutting-in process, but the trajectory of the cutting tool 110 at the time of the return operation in the second cutting-in process can also exceed the position where the trajectory of the cutting tool 110 at the time of the switch from the forward operation to the return operation in the first cutting-in process.

[0091] Further, in the above embodiment, the case where the number of vibrations of the cutting tool 110 is fixed in the first and second cutting-in processes, and the cutting tool 110 is vibrated in the X-axis direction at a ratio of 2 times with respect to the rotation of the workpiece 1 is described as an example.

[0092] However, in the first and second cutting-in processes, the frequency of the vibration can also be changed.

[0093] For example, in the first cutting-in process, the cutting tool 110 can also be vibrated at a ratio of 1 time with respect to the rotation of the spindle 8, and in the second cutting-in process, the cutting tool 110 is vibrated at a ratio of 1 time with respect to the rotation of the spindle 4. The same also applies to the third and subsequent cutting-in processes, and the frequency of the vibration can also be increased with the number of cutting-in processes.

[0094] Thus, the frequency is gradually increased each time the number is increased, and the concave-convex of the thread bottom surface of the workpiece 104 based on the thread cutting process is made finer.

[0095] Further, in the above embodiment, the amplitude of the vibration is the same as the cutting-in amount at the time of the cutting-in process, and thus the cutting-in processed portions at the time of the two consecutive cutting-in processes contact each other.

[0096] However, the amplitude of the vibration can be set to be larger than the cutting-in amount, for example, by a ratio with respect to the actual cutting-in amount of the workpiece by the cutting tool (amplitude / cutting-in ratio).

[0097] For example, by making the amplitude / cutting-in ratio larger than 1, the amplitude can be set to be larger than the cutting-in amount, and the trajectory of the cutting tool 110 at the time of the return operation in the second cutting-in process can exceed the position where the trajectory of the cutting tool 110 at the time of the switch from the forward operation to the return operation in the first cutting-in process.

[0098] Further, in the above embodiment, the cutting-in amount in each cutting-in process is set to be the same, but the cutting-in amount can also be controlled to be smaller as the number of cutting-in processes increases. Thus, as the number of cutting-in processes increases, the concave-convex of the thread bottom surface of the workpiece 104 is gradually made smaller. The amplitude of the vibration in the cutting-in process can be set according to the cutting-in amount, and controlled to be smaller as the number of cutting-in processes increases.

[0099] In addition, in the above-described embodiment, the Z-axis direction movement of the rotating workpiece 104 and the vibration are cooperated with the X-axis direction and Y-axis direction vibrations of the cutting tool 110, and the cutting tool 110 thread-cutting processes the workpiece 104.

[0100] However, the X-axis direction and Y-axis direction vibrations can be imparted to the workpiece 104, or the cutting tool 110 can be moved in the direction opposite to the feed direction instead of moving the workpiece 104 in the feed direction. Figure 1 In addition, instead of vibrating the workpiece 104 in the Z-axis direction, a motor such as a linear motor that vibrates the cutting tool 110 can be provided to vibrate the cutting tool 110 in the Z-axis direction.

[0101] The numerical control device, the machine tool system, and the numerical control method of the present disclosure, including the above-described embodiment, can adopt various embodiments having the following structures.

[0102] (1) The first aspect of the present disclosure provides a numerical control device (for example, the numerical control device 200) that causes a machine tool (for example, the machine tool 100) to perform an action of thread-cutting processing that moves a cutting tool relative to a workpiece to perform multiple plunge processes on the workpiece to form a thread on the workpiece, the numerical control device comprising:

[0103] a drive section (for example, the drive section 205) that controls a drive shaft of a spindle that rotates the workpiece and a 3-axis;

[0104] a vibration superimposition section (for example, the vibration superimposition section 2021) that superimposes vibration applied to two or more of the 3-axis on the relative movement of the cutting tool and the workpiece in order to vibrate the cutting tool and the workpiece relative to each other along a thread groove; and

[0105] a thread-cutting vibration adjustment section (for example, the vibration adjustment section 2022) that shifts the phase of the vibration relative to the phase of the spindle by a predetermined vibration phase shift amount each time in the multiple plunge processes.

[0106] According to the numerical control device, in thread-cutting processing of a workpiece of a machine tool, by applying vibration to two or more of the X-axis, Y-axis, and Z-axis, it is possible to suppress eccentricity due to the relative vibration of the cutting tool and the workpiece, to improve the accuracy of the finished shape, and to suppress the influence on the front end of the cutting tool.

[0107] (2) The numerical control device according to the above-described (1), wherein the vibration superimposition section is configured to change the frequency of the vibration.

[0108] According to the numerical control device, as the number of times increases, the frequency is gradually increased, and the concave-convex of the thread bottom surface of the work based on the thread cutting processing can be made thin.

[0109] (3) The numerical control device according to (1) or (2), wherein the vibration superimposition section is configured to set the amplitude of the vibration in accordance with the amount of plunge machining of each of the plunge machinings.

[0110] (4) The numerical control device according to any one of (1) to (3), wherein the vibration superimposition section vibrates two of the three axes.

[0111] (5) The numerical control device according to any one of (1) to (4), wherein the vibration superimposition section vibrates the three axes, and an angle formed between two of the three axes is 0° or more and 90° or less.

[0112] (6) A second aspect of the present disclosure provides a machine tool system (e.g., machine tool system 10) including:

[0113] the numerical control device according to any one of (1) to (5) (e.g., numerical control device 200); and

[0114] a machine tool (e.g., machine tool 100) that forms a thread on a work by performing a plurality of times of plunge machining on the work by relatively moving a cutting tool and the work.

[0115] According to the machine tool system, in the thread cutting processing of the machine tool on the work, by applying vibration to two or more of the X-axis, the Y-axis, and the Z-axis, the core deviation due to the relative vibration of the cutting tool and the work can be suppressed, the accuracy of the finish shape can be improved, and the influence on the front end of the cutting tool can be suppressed.

[0116] (7) A third aspect of the present disclosure is a numerical control method of a numerical control device (e.g., numerical control device 200) that causes a machine tool (e.g., machine tool 100) to perform thread cutting processing of forming a thread on a work by performing a plurality of times of plunge machining on the work by relatively moving a cutting tool and the work, in which the numerical control method,

[0117] controls a drive shaft of a spindle that rotates the work and three axes,

[0118] in order to cause the cutting tool and the work to relatively vibrate along a thread groove, superimposes vibration applied to two or more of the three axes on the relative movement of the cutting tool and the work,

[0119] in the plurality of times of the plunge machining, causes the phase of the vibration to be offset from the phase of the spindle by a vibration phase offset amount that is decided in advance each time.

[0120] According to the numerical control method, in the thread cutting process of the workpiece by the machine tool, by applying vibration to two or more of the X-axis, Y-axis, and Z-axis, the eccentricity due to the relative vibration of the cutting tool and the workpiece can be suppressed, the precision of the finished shape can be improved, and the influence on the front end of the cutting tool can be suppressed.

[0121] Reference Signs

[0122] 10 Machine tool system

[0123] 100 Machine tool

[0124] 101 Linear servo motor

[0125] 102 Spindle table

[0126] 103 Spindle motor

[0127] 104 Workpiece

[0128] 105 Linear servo motor

[0129] 106 Support table

[0130] 107 Support column

[0131] 108 Linear servo motor

[0132] 119 Tool table

[0133] 110 Cutting tool

[0134] 200 Numerical control device

[0135] 201 Analysis processing section

[0136] 202 Interpolation processing section

[0137] 203 Acceleration / deceleration processing section

[0138] 204 Control command output section

[0139] 205 Driving section

[0140] 2021 Vibration superimposition section

[0141] 2022 Vibration adjustment section

Claims

1. A numerical control device that causes a machine tool to perform an action of thread cutting processing of moving a cutting tool and a work relative to each other to perform a plurality of plunge cuttings on the work to form a thread on the work, characterized by comprising: a drive section that controls a spindle that rotates the work and a drive shaft of three axes; a vibration superimposition section that superimposes a vibration applied to the three axes on a relative movement of the cutting tool and the work in order to vibrate the cutting tool and the work relative to each other along a thread groove; and a thread cutting vibration adjustment section that shifts a phase of the vibration by a vibration phase shift amount decided in advance each time relative to a phase of the spindle in a plurality of the plunge cuttings, wherein the vibration superimposition section makes the vibration of the three axes at an angle formed between two of the three axes of 0° or more and 90° or less.

2. The numerical control device according to claim 1, characterized in that the vibration superimposition section is configured to change a frequency of the vibration.

3. The numerical control device according to claim 1, characterized in that the vibration superimposition section is configured to set an amplitude of the vibration according to a plunge amount of each of the plunge cuttings.

4. A system comprising: the numerical control device according to any one of claims 1 to 3; and a machine tool that moves a cutting tool and a work relative to each other to perform a plurality of plunge cuttings on the work to form a thread on the work.

5. A numerical control method of a numerical control device that causes a machine tool to perform an action of thread cutting processing of moving a cutting tool and a work relative to each other to perform a plurality of plunge cuttings on the work to form a thread on the work, the numerical control method characterized by comprising: controlling a spindle that rotates the work and a drive shaft of three axes, superimposing a vibration applied to the three axes on a relative movement of the cutting tool and the work in order to vibrate the cutting tool and the work relative to each other along a thread groove, shifting a phase of the vibration by a vibration phase shift amount decided in advance each time relative to a phase of the spindle in a plurality of the plunge cuttings, and making the vibration of the three axes at an angle formed between two of the three axes of 0° or more and 90° or less. ​ ​ ​ ​ ​ 4. A machine tool system characterized by comprising: ​ ​ ​ ​ ​ ​ ​ ​

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