Control device

Abstract

The present invention provides a technology capable of improving the machined surface quality of oscillation cutting in a control device for a machine tool. A control device 1 comprises: an oscillation conditions setting unit 11 that sets a plurality of oscillations conditions for oscillating a tool and a workpiece relative to one another; an oscillation command generation unit 12 that generates, on the basis of the plurality of oscillation conditions and machining conditions for machining the workpiece by means of a machine tool, an oscillation command obtained as a superposition of a plurality of different sine waves; and an oscillation command superimposing unit 14 that superimposes the oscillation command on a movement command or a position deviation of the tool or the workpiece.

Description

Control device

[0001] The present disclosure relates to a control device.

[0002] Conventionally, in machine tools, a technique for performing swing cutting while swinging a tool and a workpiece relative to each other in order to shred chips during machining is known. This type of technique is described in Patent Documents 1 and 2.

[0003] JP 2023-170949 A Patent No. 7436658 A

[0004] Compared to normal cutting without oscillation, cutting with oscillation involves areas where the tool movement trajectory has larger gaps, resulting in a problem of reduced machined surface quality. Therefore, conventional technology has room for improvement in terms of improving machined surface quality.

[0005] The present disclosure has been made in consideration of the above-mentioned problems, and aims to provide a technique that can improve the quality of the machined surface in swing cutting in a machine tool control device.

[0006] The present disclosure relates to a control device for a machine tool that performs machining while swinging a tool and a workpiece relative to one another, the control device comprising: a swing condition setting unit that sets a plurality of swing conditions for swinging the tool and the workpiece relative to one another; a swing command generation unit that generates a swing command that superimposes a plurality of different sine waves based on the plurality of swing conditions and machining conditions for machining the workpiece using the machine tool; and a swing command superimposition unit that superimposes the swing command on a movement command or position deviation of the tool or the workpiece.

[0007] According to the present disclosure, it is possible to provide a technique for improving the quality of the machined surface in swing cutting in a control device for a machine tool.

[0008] 1 is a functional block diagram of a control device for a machine tool according to a first embodiment. FIG. 1 is a graph showing an oscillation cutting path when machining control of the prior art is executed. FIG. 2 is a schematic diagram explaining the relationship between path difference and surface roughness when machining control of the prior art is executed. FIG. 2 is a graph showing an oscillation cutting path when machining control by the control device of this embodiment is executed. FIG. 3 is a schematic diagram explaining the relationship between path difference and surface roughness when machining control by the control device of this embodiment is executed. FIG. 3 is a graph showing an oscillation cutting path when the amplitude of the second harmonic is set to ⅔ or more of the reference wave. FIG. 4 is a table explaining surface roughness that changes depending on the relationship between the amplitude of the second harmonic and the amplitude of the reference wave. FIG. 4 is a graph showing an oscillation cutting path when I is set based on the coefficient of a positive second harmonic. FIG. 5 is a graph showing the relationship between a movement command and an oscillation cutting path when infeed occurs by the maximum amplitude of the oscillation command. FIG. 6 is a graph showing the relationship between a movement command and an oscillation cutting path when infeed is offset by the maximum amplitude of the oscillation command. FIG. 7 is a graph showing the relationship between a movement command and an oscillation cutting path when a shock occurs at the start of oscillation cutting. 10 is a graph showing the relationship between a movement command and an oscillation cutting path when the phase is offset to avoid a shock at the start of oscillation cutting. It is a functional block diagram of a learning controller applied to a control device of a machine tool according to a second embodiment. It is a graph explaining a change in position deviation due to learning control applied in the second embodiment.

[0009] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the description of the second and subsequent embodiments, the same reference numerals will be used to designate components common to the first and second embodiments, and the description thereof will be omitted as appropriate.

[0010] [First embodiment] Figure 1 is a functional block diagram of a control device 1 for a machine tool according to a first embodiment. First, the machine tool that is the object to be controlled by the control device 1 shown in Figure 1 will be described. The machine tool performs machining while oscillating the tool 2 and the workpiece relative to one another based on a machining program, conditions specified by an operator, etc., thereby generating air cutting to shred chips. Machining methods include cutting and threading.

[0011] The machine tool includes, for example, a mechanism including a motor 30 that operates at least one spindle that rotates the tool 2 and the workpiece relative to one another, and at least one feed axis that moves the tool 2 relative to the workpiece. The tool 2 is a cutting tool that cuts the workpiece. Note that the shape of the workpiece is not limited when machined using a machine tool. That is, the machine tool can be used in cases where the workpiece has a tapered or arc-shaped portion on the machining surface, requiring multiple feed axes (Z-axis and X-axis), or in cases where the workpiece is columnar or cylindrical and only one specific feed axis (Z-axis) is sufficient.

[0012] The control device 1 causes the machine tool to perform swing cutting by superimposing a swing command that commands relative swing between the workpiece and the tool 2 on a movement command that commands relative movement between the workpiece and the tool 2. The control device 1 is configured using, for example, a computer that includes memories such as a ROM (read only memory) and a RAM (random access memory), a CPU (central processing unit), and a communication control unit, all connected to one another via a bus.

[0013] The CPU, memory, and control program stored in the memory of the control device 1 work together to realize a functional section that causes the machine tool to perform swing cutting.

[0014] The control device 1 of this embodiment has, as functional units, a machining condition setting unit 10, a swing condition setting unit 11, a swing command generation unit 12, a position deviation calculation unit 13, a swing command superposition unit 14, a position control unit 15, a speed / current control unit 16, and a maximum amplitude / phase calculation unit 17.

[0015] The machining condition setting unit 10 sets a plurality of machining conditions for relatively swinging the tool 2 and the workpiece. The machining conditions are specified by a machining program or set as parameters of the control device 1. The machining conditions set by the machining condition setting unit 10 are input to the swing command generating unit 12.

[0016] The machining conditions will be described. The machining conditions include information necessary for machining, such as the spindle rotation speed (1 / min), the feed amount per spindle rotation (mm / rev), and the cutting depth (mm). The feed amount per spindle rotation (mm / rev) can also be calculated from a combination of the spindle rotation speed (1 / min) and the feed rate (mm / min) of the tool 2. The feed amount per minute (mm / min) may also be included in the machining conditions.

[0017] The swing condition setting unit 11 sets a plurality of swing conditions for swinging the tool 2 and the workpiece relative to each other. The swing conditions are specified by a machining program or set as parameters of the control device 1. The swing conditions set by the swing condition setting unit 11 are input to the swing command generating unit 12.

[0018] The oscillation conditions will now be described. The oscillation conditions include, as information for uniquely identifying the vibration waveform, at least a frequency parameter, which is information relating to the relative oscillation frequency per rotation between the tool 2 and the workpiece, and an amplitude parameter, which is information relating to the oscillation amplitude with respect to the relative feed amount per rotation between the tool 2 and the workpiece. The frequency parameter and the amplitude parameter may be determined from the spindle rotation speed, feed rate per minute, feed rate per minute, depth of cut, spindle rotation speed, frequency magnification, amplitude magnification, etc.

[0019] In this embodiment, the oscillation frequency magnification I (times), which is the number of oscillations per rotation of the spindle, is used as a frequency parameter, or the oscillation frequency f (Hz) itself may be used. The oscillation frequency magnification I (times) may be specified directly, or may be calculated from the oscillation frequency (Hz) and the rotation speed S (1 / min) of the spindle after specifying the oscillation frequency (Hz). Furthermore, the oscillation amplitude magnification K (times), which indicates the magnitude of the oscillation amplitude (mm) relative to the magnitude of the feed amount per rotation of the spindle, is used as an amplitude parameter, or the oscillation amplitude (mm) itself may be used. Similarly, the oscillation amplitude magnification K (times) may be specified directly, or may be calculated from the oscillation amplitude (mm) and the rotation speed S (1 / min) of the spindle after specifying the oscillation amplitude (mm).

[0020] The swing command generating unit 12 generates a swing command by superimposing a plurality of different sine waves based on a plurality of swing conditions and machining conditions for machining the workpiece by the machine tool. The swing command generated by the swing command generating unit 12 is input to the swing command superimposing unit 14. Note that the method of generating a swing command by the swing command generating unit 12 of this embodiment will be described in detail later.

[0021] The position deviation calculation unit 13 calculates a position deviation, which is the difference between a movement command for the tool 2 or workpiece and a position feedback based on position detection by the encoder 45 of the feed axis motor 30. The position deviation calculation unit 13 is configured by, for example, an adder. The position deviation calculated by the position deviation calculation unit 13 is input to the swing command superimposition unit 14. Note that the position deviation may be calculated by an integrator and then input to the swing command superimposition unit 14.

[0022] The swing command superimposing unit 14 generates a superimposed command by superimposing (adding) the swing command generated by the swing command generating unit 12 on a position deviation, which is a movement command that reflects position feedback. The swing command superimposing unit 14 is configured, for example, by an adder. The superimposed command generated by the swing command superimposing unit 14 is input to the position control unit 15. Note that instead of superimposing on the position deviation, the swing command superimposing unit 14 may be configured to superimpose (add) the swing command generated by the swing command generating unit 12 on a movement command (position command).

[0023] The position control unit 15 generates a position command based on the superimposed command input from the position control unit 15 , and outputs the position command to the speed / current control unit 16 .

[0024] The speed / current control unit 16 outputs operation commands (speed command / current command) for controlling the speed and current based on the position command to the motor 30. As a result, swing machining is performed in which the workpiece and the tool 2 are swung relative to each other.

[0025] The maximum amplitude / phase calculation unit 17 calculates the maximum amplitude or the phase at the maximum amplitude of the waveform obtained by superimposing a plurality of different sine waves. In this embodiment, the maximum amplitude / phase calculation unit 17 calculates both the maximum amplitude and the phase at the maximum amplitude of the waveform obtained by superimposing a plurality of different sine waves, which is generated by the swing command generation unit 12.

[0026] Next, a method for calculating a swing command by the swing command generator 12 of this embodiment will be described in comparison with the prior art.

[0027] First, machining control of the prior art will be described with reference to Figures 2 and 3. Figure 2 is a graph showing the swing cutting path when the prior art machining control is executed. Figure 3 is a schematic diagram explaining the relationship between the path difference and surface roughness when the prior art machining control is executed. In the following description, the horizontal axis of the swing cutting path graph represents the rotation angle (phase) of the workpiece, and the vertical axis represents the position of the tool 2.

[0028] In the prior art, a swing command is determined to cross the previous pass and the current pass so as to generate an air-cut portion that shreds the chips. The swing command is calculated, for example, by the following Equation 1:

[0029]

[0030] Here, f, S, t, K, and I in Equation 1 represent the following parameters, respectively: f: feed amount per revolution [mm / rev] S: spindle rotation speed [min －１ ] t: time [s] K: coefficient (oscillation amplitude magnification) I: coefficient (oscillation frequency magnification)

[0031] The surface roughness of the machined surface of a workpiece can be calculated, for example, using the following formula 2. As shown in formula 2, the path difference between adjacent passes has a significant effect on the surface roughness of the machined surface of the workpiece. In this regard, as shown in Figure 2, with the conventional technology, the path difference d0 of the oscillating cutting path is about twice the path difference of the normal cutting path in some places, which shows that the quality of the machined surface deteriorates.

[0032]

[0033] Here, h, d, and R in Equation 2 represent the following parameters, respectively: h: theoretical surface roughness [μm], d: path difference between adjacent passes [mm], and R: corner radius of tool 2 [mm].

[0034] Next, machining control performed by the control device 1 of this embodiment will be described. In this embodiment, the swing command generator 12 generates a swing command expressed by Equation 4 as a swing command formula for improving the quality of the machined surface, for example, based on the following Equation 3, which superimposes harmonics. In this way, by generating a swing command in which multiple sine waves, preferably cosine waves and sine waves in terms of phase difference, are superimposed, the distance between adjacent swing cutting paths can be made smaller than before, making it possible to improve the quality of the machined surface.

[0035]

[0036] Here, N, f, S, t, and K in Equation 3 ａｍ , K. ｂｍ , I respectively represent the following parameters: N: 1, 2, 3, ... (natural number) f: feed amount per time [mm / rev] S: spindle rotation speed [min －１ ] t: Time [s] K ａｍ , K. ｂｍ : Coefficient (oscillation amplitude magnification) I: Coefficient (oscillation frequency magnification)

[0037]

[0038] Here, N, f, S, t, and K in Equation 4 ａｍ , K. ｂｍ , I., A. ｍａｘ , θ ｍａｘ respectively represent the following parameters: N: 1, 2, 3, ... (natural number) f: feed amount per time [mm / rev] S: spindle rotation speed [min －１ ] t: Time [s] K ａｍ , K. ｂｍ : Coefficient (oscillation amplitude magnification) I: Coefficient (oscillation frequency magnification) A ｍａｘ : Maximum value θ of Equation 3 ｍａｘ : arcsin (A ｍａｘ ) / (2πSI / 60)

[0039] 4 and 5, the oscillation path and surface roughness when an oscillation command is made by superimposing a double harmonic on the reference wave when N in Equation 4 is 2 will be described. FIG. 4 is a graph showing an oscillation cutting path when machining control is executed by the control device 1 of this embodiment. FIG. 5 is a schematic diagram explaining the relationship between the path difference and surface roughness when machining control is executed by the control device 1 of this embodiment. When N in Equation 4 is 2 and K ｂ1 = 0, K ａ２ = 0, the following equation 5 is derived. ａ１ The cosine term following is the reference wave, K ｂ２ The sine term following indicates the second harmonic.

[0040]

[0041] 4 and 5, in this embodiment, by superimposing a plurality of sine waves, the path difference d1 is smaller than the conventional path difference d0 shown in Fig. 2. As shown in the above-mentioned formula 2, the path difference has a large effect on the surface roughness, and therefore, according to this embodiment, which can reduce the path difference, it is clear that the quality of the machined surface can be improved.

[0042] Furthermore, in this embodiment, the second harmonic (K ｂ２ The amplitude of the sin term following the reference wave (K ａ１ By making the difference (cosine term following the difference) equal to or less than two-thirds, the path difference can be further reduced and the quality of the machined surface can be further improved.

[0043] The relationship between the amplitude of the second harmonic and the amplitude of the reference wave will be explained with reference to Figures 4 and 6. The above-mentioned Figure 4 is a graph showing the oscillation path when the amplitude of the second harmonic is set to 2 / 3 or less of the reference wave. In contrast, Figure 6 is a graph showing the oscillation cutting path when the amplitude of the second harmonic is set to 2 / 3 or more of the reference wave. The path difference d2 in Figure 6 is larger than the path difference d1 in Figure 4.

[0044] FIG. 7 is a table illustrating how surface roughness changes depending on the relationship between the amplitude of the second harmonic and the amplitude of the reference wave. The table in FIG. 7 shows the surface roughness corresponding to cases where the amplitude of the second harmonic is less than two-thirds of the reference wave and where the amplitude of the second harmonic is more than two-thirds of the reference wave. For reference, the table in FIG. 7 also shows the surface roughness for normal cutting without oscillation. In the table in FIG. 7, the machining conditions are assumed to be the same: f = 0.1 mm / rev, S = 1000 min-1, and corner radius R of tool 2 = 0.4 mm.

[0045] When the amplitude of the second harmonic is less than 2 / 3 of the reference wave, the oscillation condition is I = 1.67, K ａ１ = 0.9, K ｂ２ = -0.5, and the maximum path difference dmax is about 0.15 [mm]. In addition, the oscillation conditions for 2 / 3 or more are I = 1.67, K ａ１ = 0.9, K ｂ２ = -0.7, and the maximum path difference dmax is approximately 0.16 [mm]. As shown in the table in Figure 7, when the amplitude of the second harmonic is less than 2 / 3 of the reference wave, the surface roughness is approximately 7.0 [μm], whereas when the amplitude of the second harmonic is more than 2 / 3 of the reference wave, the surface roughness is approximately 8.1 [μm]. Thus, when the amplitude of the second harmonic is less than 2 / 3 of the reference wave, the surface roughness can be lower. Note that, for reference, in normal cutting without oscillation, no oscillation conditions are set and no oscillation is performed, so the surface roughness is approximately 3.1 [μm].

[0046] Next, a method for determining the coefficient I will be described. In this embodiment, I is the coefficient of the second harmonic, K ｂ２ The reference number term in the swing command is determined according to the positive or negative sign of K ａ１ >0 and is always a positive sign.

[0047] 4 and 8, I and the coefficient of the second harmonic K ｂ２ The relationship between K ｂ２ <0 and the coefficient of the second harmonic has a negative sign. ｂ２< 0, I is set to satisfy the condition I = n + 2 / 3 (n = 1, 2, 3, ...), which makes it easier to shred chips as in the oscillating cutting path shown in Figure 4. In contrast, Figure 8 is a graph showing an oscillating cutting path when I is set based on the coefficient of the second harmonic with a positive sign. ｂ２ If I is set to satisfy the condition I=n+1 / 3 (n=1, 2, 3, . . . ), chips are easily shredded, as in the swing cutting path shown in FIG.

[0048] Furthermore, the swing command generator 12 of this embodiment performs a superimposing process of superimposing a swing command on a movement command based on the maximum amplitude and the phase at the time of the maximum amplitude calculated by the maximum amplitude / phase calculator 17 .

[0049] 9 and 10, the superposition process using the maximum amplitude calculated by the maximum amplitude / phase calculation unit 17 will be described. Fig. 9 is a graph showing the relationship between the movement command and the swing cutting path when cutting-in by the maximum amplitude of the swing command occurs. Fig. 10 is a graph showing the relationship between the movement command and the swing cutting path when cutting-in by the maximum amplitude of the swing command is offset.

[0050] 9, when a swing command is simply superimposed on a movement command, cutting by the maximum amplitude of the swing command may occur. In order to prevent cutting by the maximum amplitude, the swing command generator 12 of this embodiment performs an offset by the maximum amplitude of the swing command calculated by the maximum amplitude / phase calculator 17.

[0051] The swing command superimposing unit 14 superimposes the movement command (position deviation) and the swing command with an offset of the maximum amplitude. As shown in Fig. 10, by offsetting the maximum amplitude of the swing command, the swing cutting path moves backward relative to the movement command, preventing unintended cutting. The swing command generating unit 12 performs offset processing, for example, so that the position of the tool 2 moves away from the workpiece by the distance of the maximum amplitude.

[0052] Next, the superposition process using the phase at the maximum amplitude calculated by the maximum amplitude / phase calculation unit 17 will be described with reference to Fig. 11 and Fig. 12. Fig. 11 is a graph showing the relationship between the movement command and the swing cutting path when a shock occurs at the start of swing cutting. Fig. 12 is a graph showing the relationship between the movement command and the swing cutting path when the phase is offset to avoid the shock at the start of swing cutting.

[0053] 11, even if the maximum amplitude of the swing command is offset, the swing operation may not start smoothly depending on the phase at the start of swing cutting, which may result in a shock. In this embodiment, the swing command generator 12 performs an offset based on the phase at the maximum amplitude calculated by the maximum amplitude / phase calculator 17, in order to avoid a shock at the start of swing. The swing command generator 12 performs an offset, for example, so that the phase at the maximum amplitude coincides with the start timing of swing cutting.

[0054] The swing command superimposing unit 14 superimposes the movement command (position deviation) and the swing command in a state where they are offset based on the phase at the time of maximum amplitude. As shown in Fig. 12, by offsetting the swing command by the phase at which it becomes maximum, the transition to swing cutting becomes smoother and the shock at the start of swing cutting can be reduced.

[0055] As described above, the control device 1 of the first embodiment comprises a swing condition setting unit 11 that sets a plurality of swing conditions for swinging the tool 2 and the workpiece relative to one another, a swing command generation unit 12 that generates a swing command in which a plurality of different sine waves are superimposed based on the plurality of swing conditions and the machining conditions for machining the workpiece using a machine tool, and a swing command superimposition unit 14 that superimposes the swing command on a movement command or position deviation of the tool 2 or the workpiece.

[0056] This reduces the path difference between adjacent passes that affects surface roughness, thereby improving the quality of the machined surface.

[0057] In this embodiment, the oscillation command is generated by superimposing sine waves having frequencies that are integer multiples of the reference oscillation frequency.

[0058] As a result, superimposing harmonics of integer multiples makes the swing command somewhat easier than, for example, harmonics of real multiples with decimal points, making it easier to code the control software and facilitating calculations, thereby reducing the control load.

[0059] In this embodiment, the oscillation command is generated by superimposing sine waves having frequencies that are even multiples of the reference oscillation frequency.

[0060] As a result, compared to superimposing sine waves with odd multiples of the frequency, by superimposing sine waves with even multiples of the frequency, the area surrounded by adjacent oscillating cutting paths can be made into a parallelogram shape, and the path difference can be reduced, thereby further improving the quality of the machined surface.

[0061] In this embodiment, the oscillation command is generated by superimposing sine waves having a frequency twice the reference oscillation frequency.

[0062] This makes it possible to achieve oscillation machining with small path differences and high-quality machined surfaces through simple oscillation command and control by superimposing sine waves (harmonics) of double the frequency.

[0063] In this embodiment, the oscillation command is generated by superimposing sine waves having an amplitude smaller than the reference oscillation amplitude.

[0064] This makes it possible to avoid a situation in which noise is generated by superimposing a sine wave having an amplitude larger than the reference oscillation amplitude, making it impossible to perform oscillation cutting properly.

[0065] In this embodiment, the oscillation command is generated by superimposing sine waves having an amplitude equal to or less than two-thirds of the reference oscillation amplitude.

[0066] This allows the path difference to be further reduced, and the quality of the machined surface to be further improved.

[0067] In addition, the control device 1 of this embodiment further includes a maximum amplitude / phase calculation unit 17 that calculates the maximum amplitude or the phase at the maximum amplitude of a waveform obtained by superimposing multiple different sine waves, and the swing command generation unit 12 generates a swing command that is offset based on the maximum amplitude or the phase at the maximum amplitude.

[0068] By offsetting based on the maximum amplitude, it is possible to prevent situations where the swing cutting path pulls in response to a movement command and cuts in ahead of the target. Also, by offsetting based on the phase at the time of maximum amplitude, it is possible to reduce shock at the start of swing and to start swing cutting smoothly.

[0069] Second Embodiment Next, a configuration of a second embodiment that differs from the first embodiment will be described with reference to Fig. 13. Fig. 13 is a functional block diagram of a learning controller 50 that is applied to a machine tool control device 1 according to the second embodiment.

[0070] The control device 1 of the second embodiment further includes a learning controller 50 and a correction command superimposition unit 55 in addition to the configuration of the first embodiment. As shown in Fig. 13 , the learning controller 50 and the correction command superimposition unit 55 are disposed, for example, between the swing command superimposition unit 14 and the position control unit 15.

[0071] The learning controller 50 includes an adder 51, a band-limiting filter 52, a learning memory 53, and a dynamic characteristic compensation element 54.

[0072] The adder 51 adds the superimposed command input from the swing command superimposing unit 14 and the correction data input from the learning memory 53, and outputs the result to the band-limiting filter 52. The superimposed command input from the swing command superimposing unit 14 includes the difference between the position command and the position feedback, and is therefore generally the same as the position deviation input to a learning controller.

[0073] The band-limiting filter 52 removes disturbances asynchronous with the oscillation command in order to stabilize the learning control. The cutoff frequency of the band-limiting filter 52 is set based on the maximum frequencies of a plurality of different sine waves, and is set to, for example, a frequency that is twice or several times the maximum frequency. The band-limiting filter 52 performs a filter process on the output of the adder 51 to remove disturbances, thereby obtaining correction data and outputting the correction data to the learning memory 53.

[0074] The learning memory 53 associates the swing phase of a predetermined swing period with the correction data and stores them in memory. The learning memory 53 stores, for example, correction data obtained by correcting the position deviation from one period before and the superimposed command of the swing command. The period of the learning controller 50 is set based on the period of a sine wave (reference wave) that serves as the basis for the swing command output by the swing command generator 12, and for example, the period of the reference wave is set as the learning period.

[0075] The dynamic characteristic compensation element 54 adjusts the timing (phase) for compensating for the position deviation stored in the learning memory 53. The dynamic characteristic compensation element 54 outputs a correction command (correction amount) for compensating for the phase delay of the controlled object. The correction command output by the dynamic characteristic compensation element 54 is input to the correction command superimposition unit 55.

[0076] The correction command superimposing unit 55 adds the correction command input from the learning controller 50 to the superimposed command of the position deviation and swing command generated by the swing command superimposing unit 14. The superimposed command corrected by the learning controller 50 and the correction command superimposing unit 55 is output to the position control unit 15. The subsequent processing is the same as in the above embodiment.

[0077] As described above, the control device 1 of the second embodiment further includes a learning controller 50 that performs learning control based on the position deviation, in addition to the configuration of the first embodiment.

[0078] As a result, the position deviation is compensated for by the learning control, thereby achieving highly accurate tracking and further improving the quality of the machined surface. Fig. 14 is a graph illustrating the change in position deviation due to the learning control applied in the second embodiment. The left side of Fig. 14 shows the change over time in position deviation when normal control without learning control is performed, and the right side of Fig. 14 shows the change over time in position deviation when learning control is performed. As can be seen from Fig. 14, by performing learning control with the control device 1 as in the second embodiment, the position deviation can be effectively reduced.

[0079] In the second embodiment, the period of the learning control is set based on the period of the sine wave that is the basis of the swing command.

[0080] This allows the period of the learning control to be set in accordance with the period of the sine wave that is the basis for the swing command, and the learning control can be executed appropriately and reliably.

[0081] In the second embodiment, the off frequency of the band-limiting filter 52 for learning control is set based on the maximum frequency of a plurality of different sine waves.

[0082] As a result, even if the oscillation command includes a plurality of different sine waves, filtering processing can be appropriately performed based on the maximum frequency of the plurality of sine waves.

[0083] The present disclosure is not limited to the above-described embodiments, and includes modifications and improvements within the scope of achieving the object of the present disclosure.

[0084] The following supplementary note is further disclosed regarding the above embodiment and modified examples: (Supplementary note 1) A control device (1) for a machine tool that performs machining while swinging a tool (2) and a workpiece relative to one another, the control device (1) comprising: a swing condition setting unit (11) that sets a plurality of swing conditions for swinging the tool (2) and the workpiece relative to one another, a swing command generating unit (12) that generates a swing command in which a plurality of different sine waves are superimposed based on the plurality of swing conditions and machining conditions for machining the workpiece by the machine tool, and a swing command superimposing unit (14) that superimposes the swing command on a movement command or position deviation of the tool (2) or the workpiece.

[0085] (Supplementary Note 2) In the machine tool control device (1) described above in (Supplementary Note 1), the swing command generating unit (12) generates the swing command by superimposing sine waves having frequencies that are integer multiples of a reference swing frequency.

[0086] (Supplementary Note 3) In the machine tool control device (1) described in (Supplementary Note 1) or (Supplementary Note 2) above, the swing command generating unit (12) generates the swing command by superimposing sine waves having frequencies that are even multiples of a reference swing frequency.

[0087] (Supplementary Note 4) In the machine tool control device (1) described in any one of (Supplementary Note 1) to (Supplementary Note 3) above, the swing command generating unit (12) generates the swing command by superimposing sine waves having a frequency twice the reference swing frequency.

[0088] (Supplementary Note 5) In the machine tool control device (1) described in any one of (Supplementary Note 1) to (Supplementary Note 4) above, the swing command generation unit (12) generates the swing command by superimposing sine waves having an amplitude smaller than a reference swing amplitude.

[0089] (Supplementary Note 6) In the machine tool control device (1) described above in (Supplementary Note 5), the swing command generation unit (12) generates the swing command by superimposing sine waves having amplitudes that are two-thirds or less of the reference swing amplitude.

[0090] (Supplementary Note 7) The machine tool control device (1) described in any one of (Supplementary Note 1) to (Supplementary Note 6) above further comprises a maximum amplitude / phase calculation unit (17) that calculates the maximum amplitude or the phase at the maximum amplitude of a waveform obtained by superimposing the plurality of different sine waves, and the swing command generation unit (12) generates the swing command that is offset based on the maximum amplitude or the phase at the maximum amplitude.

[0091] (Supplementary Note 8) The control device (1) for a machine tool according to any one of (Supplementary Note 1) to (Supplementary Note 7) above further comprises a learning controller (50) that performs learning control based on the position deviation.

[0092] (Supplementary Note 9) In the control device (1) for a machine tool described above (Supplementary Note 8), the period of the learning control is set based on the period of a sine wave that is a reference for the swing command.

[0093] (Supplementary Note 10) In the machine tool control device (1) described in (Supplementary Note 8) or (Supplementary Note 9) above, the cutoff frequency of the band-limiting filter (52) for the learning control is set based on the maximum frequency of the plurality of different sine waves.

[0094] REFERENCE SIGNS LIST 1 control device 2 tool 10 machining condition setting section 11 swing condition setting section 12 swing command generating section 13 position deviation calculation section 14 swing command superposition section 15 position control section 16 speed / current control section 30 motor 45 encoder 50 learning controller

Claims

1. A control device for a machine tool that performs machining while swinging a tool and a workpiece relative to one another, comprising: a swing condition setting unit that sets a plurality of swing conditions for swinging the tool and the workpiece relative to one another; a swing command generation unit that generates a swing command by superimposing a plurality of different sine waves based on the plurality of swing conditions and the machining conditions for machining the workpiece using the machine tool; and a swing command superimposition unit that superimposes the swing command on a movement command or position deviation of the tool or the workpiece.

2. The control device according to claim 1, wherein the oscillation command generating unit generates the oscillation command by superimposing sine waves having frequencies that are integer multiples of a reference oscillation frequency.

3. The control device according to claim 1 or 2, wherein the oscillation command generating unit generates the oscillation command by superimposing sine waves having frequencies that are even multiples of a reference oscillation frequency.

4. A control device according to any one of claims 1 to 3, wherein the oscillation command generating unit generates the oscillation command by superimposing sine waves having a frequency twice the reference oscillation frequency.

5. A control device according to any one of claims 1 to 4, wherein the swing command generating unit generates the swing command by superimposing sine waves having an amplitude smaller than a reference swing amplitude.

6. The control device according to claim 5, wherein the swing command generating unit generates the swing command by superimposing sine waves having amplitudes that are two-thirds or less of the reference swing amplitude.

7. A control device as claimed in any one of claims 1 to 6, further comprising a maximum amplitude / phase calculation unit that calculates the maximum amplitude or the phase at the maximum amplitude of the waveform obtained by superimposing the plurality of different sine waves, and wherein the swing command generation unit generates the swing command that is offset based on the maximum amplitude or the phase at the maximum amplitude.

8. A control device according to any one of claims 1 to 7, further comprising a learning controller that performs learning control based on the position deviation.

9. The control device according to claim 8, wherein the period of the learning control is set based on the period of a sine wave that is the basis of the oscillation command.

10. The control device according to claim 8 or 9, wherein the cutoff frequency of the band limiting filter of the learning control is set based on the maximum frequency of the plurality of different sine waves.

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