Control device of machine tool

Abstract

The present invention provides a control device for a machine tool, which can smoothly stop the oscillation at an arbitrary timing without impairing the chip-breaking property and can suppress the impact generated in the machine tool. The machine tool performs machining while relatively oscillating a tool and a workpiece. The control device (1) of the machine tool includes: an oscillation command generation unit (12) that generates an oscillation command based on machining conditions and oscillation conditions; an oscillation stop determination unit (13) that determines the timing of oscillation stop; and a position-velocity control unit (17) that relatively oscillates the tool and the workpiece based on an overlapping command generated by overlapping the position command or the position deviation with the oscillation command. The oscillation command generation unit (12) gradually attenuates the oscillation amplitude starting from the timing when the oscillation stop is notified by the oscillation stop determination unit (13).

Description

Technical Field

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

[0002] Conventionally, as a chip countermeasure for hole opening machining, turning machining, etc., oscillatory cutting has sometimes been applied. In machining where oscillatory cutting is applied, when the oscillation stops and the movement command changes abruptly, the machine tool generates an impact. The mechanical impact affects the life of the machining tool and the like and the accuracy of the machined workpiece.

[0003] As a technique related to oscillation stop, for example, the following technique has been proposed: when reaching the machining stop position, the oscillation amplitude is reduced as the feed operation progresses, thereby preventing cutting in beyond the machining stop position (for example, refer to Patent Document 1).

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: International Publication No. 2016-047485 Summary of the Invention

[0007] Problems to be Solved by the Invention

[0008] However, the technique of Patent Document 1 is not aimed at reducing the impact generated in the machine tool. In addition, the technique of Patent Document 1 is a technique for reducing the oscillation amplitude according to the remaining movement distance, etc. when reaching a predetermined machining stop position, rather than a technique for smoothly stopping the oscillation at an arbitrary timing.

[0009] Therefore, a technique is desired that can smoothly stop the oscillation at an arbitrary timing without impairing the chip breakability and can suppress the impact generated in the machine tool.

[0010] Means for Solving the Problems

[0011] The present disclosure is a control device for a machine tool, in which the machine tool performs machining while relatively oscillating a tool and a workpiece. The control device is characterized by including: an oscillation command generation unit that generates an oscillation command based on oscillation conditions; an oscillation stop determination unit that determines the timing of oscillation stop; and a control unit that relatively oscillates the tool and the workpiece based on an overlapping command generated by overlapping the oscillation command on a movement command. The oscillation command generation unit gradually attenuates the oscillation amplitude starting from the timing when the oscillation stop determination unit notifies the oscillation stop.

[0012] Advantages of the Invention

[0013] According to one aspect of the present disclosure, a control device for a machine tool can be provided that can smoothly stop the oscillation at any timing without impairing the chip-breaking property and can suppress the impact generated in the machine tool. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 Shows the structure of a control device for a machine tool according to an embodiment of the present disclosure.

[0015] Figure 2 Shows the position command and position deviation in conventional oscillatory cutting.

[0016] Figure 3 Shows the position command and position deviation in oscillatory cutting according to an embodiment of the present disclosure.

[0017] Figure 4 For explaining the method of updating and advancing the oscillation phase in oscillatory cutting according to an embodiment of the present disclosure.

[0018] Figure 5 Shows the position command and position deviation when the update of the oscillation phase is stopped at the time of oscillation stop notification in oscillatory cutting according to an embodiment of the present disclosure.

[0019] Figure 6 Shows the position command and position deviation when the oscillation phase is rapidly advanced at the time of oscillation stop notification and stopped at a specific phase in oscillatory cutting according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0020] Hereinafter, an embodiment of the present disclosure will be described in detail with reference to the drawings.

[0021] Figure 1 Shows the structure of a control device 1 for a machine tool according to an embodiment of the present disclosure. As Figure 1 shown, the control device 1 for a machine tool according to this embodiment is configured to include a servo control device 10 that drives and controls a motor 30 for driving a feed axis.

[0022] As Figure 1 shown, the control device 1 for a machine tool according to this embodiment includes a first adder 11, an oscillation command generation unit 12, an oscillation stop determination unit 13, a second adder 14, a learning controller 15, a third adder 16, and a position speed control unit 17.

[0023] In the control device 1 for a machine tool according to this embodiment, a position command generation unit 20 generates a position command as a movement command for the motor 30 based on machining conditions. As Figure 1 shown, the generated position command is input to the first adder 11 of the servo control device 10 described later.

[0024] The first adder 11 calculates the position deviation. Specifically, the first adder 11 calculates the difference between the position feedback obtained from the position detection by the encoder of the motor 30 of the feed axis and the position command, that is, the position deviation.

[0025] The swing command generation unit 12 generates a swing command based on at least the swing conditions. The swing command generation unit 12 can obtain the swing command according to the swing conditions such as the swing amplitude magnification and the swing frequency magnification and the machining conditions, or can obtain the swing command according to the swing conditions such as the swing amplitude and the swing frequency. For example, in the present embodiment, when calculating the swing command, the swing amplitude magnification and the swing frequency magnification are used as the swing conditions. However, when used for the case where the swing axis has stopped, if the swing amplitude and the swing frequency are directly used as the swing conditions, even the stopped axis can swing. In addition, the magnification and the conditions that are not magnification can be arbitrarily combined.

[0026] In addition, the swing command generation unit 12 starts to gradually attenuate the swing amplitude at the timing when the swing stop is notified from the swing stop determination unit 13 described later. The attenuation of the swing amplitude at the time of this swing stop notification will be described in detail later.

[0027] The swing stop determination unit 13 determines the timing of swing stop. Specifically, the swing stop determination unit 13 can determine the timing of swing stop based on the machining conditions, or can determine the timing of swing stop according to an external notification. More specifically, the swing stop determination unit 13 determines the swing stop at an arbitrary timing during machining according to the machining program and the machining parameter setting, or the signal input from the outside, etc., and notifies the swing command generation unit 12. In addition, the swing stop determination unit 13 can also notify the swing command generation unit 12 of the swing stop in advance so that the swing can be stopped at an arbitrary timing.

[0028] The second adder 14 generates an overlapping command. Specifically, the second adder 14 overlaps the swing command generated by the swing command generation unit 12 with respect to the position deviation calculated by the first adder 11, thereby generating an overlapping command. In addition, the second adder 14 can be configured to add the swing command generated by the swing command generation unit 12 to the position command. Or, it can be configured that the swing command (speed command) is generated in the swing command generation unit 12, and the second adder 14 adds the swing command to the movement command (speed command).

[0029] The learning controller 15 calculates a correction amount for the overlapping command based on the overlapping command, and adds the calculated correction amount to the overlapping command by the third adder 16, thereby correcting the overlapping command. The learning controller 15 has a memory, and associates the swing phase with the correction amount and stores them in the memory within one cycle or multiple cycles of the swing. At a timing capable of compensating for the phase delay of the swing motion corresponding to the responsiveness of the motor 30, the overlapping command stored in the memory is read out and output as a correction amount to the third adder 16. When there is no swing phase for which the correction amount is output among the swing phases stored in the memory, the correction amount to be output can be calculated based on the correction amount close to the swing phase. Generally, the higher the swing frequency, the greater the position deviation with respect to the swing command. Therefore, by using this learning controller 15 for correction, the followability for the periodic swing command can be improved.

[0030] The position and speed control unit 17 generates a torque command for the motor 30 used to drive the feed shaft based on the overlapping command added with the correction amount, and controls the motor 30 according to the generated torque command. Thereby, machining is performed while relatively swinging the tool and the workpiece.

[0031] Next, the attenuation of the swing amplitude at the time of swing stop notification will be described in detail.

[0032] Figure 2 Shows the position command and position deviation in the conventional swing cutting. Figure 3 Shows the position command and position deviation in the swing cutting of the first embodiment. The position command in this description refers to the overlapping command in the protection scope. In Figure 2 and Figure 3 , the horizontal axis represents time (seconds), and the first axis (left) of the vertical axis represents the position command (overlapping command) (mm), and the second axis (right) represents the position deviation (mm).

[0033] As Figure 2 shown, in the conventional swing cutting, the swing amplitude is not attenuated at the timing of notifying the swing stop. Therefore, immediately after the swing stops, the swing command suddenly becomes 0, the position command changes sharply, and the position deviation increases sharply. As a result, the machine tool generates a large impact, which is related to the deterioration of the life of the machining tool and the like and the accuracy of the machined workpiece.

[0034] In contrast, in the present embodiment, the swing command generation unit 12 is configured to gradually attenuate the swing amplitude from the timing when the swing stop determination unit 13 notifies the swing stop. Therefore, as Figure 3As shown, in the oscillatory cutting of the present embodiment, since the oscillation amplitude gradually decays from the timing when the oscillation stop is notified until the oscillation stops, the position command does not change abruptly, and the change in the position deviation becomes smooth. As a result, the impact generated in the machine tool can be reduced, and the deterioration of the life of the machining tool and the like and the accuracy of the machined workpiece can be suppressed.

[0035] There is no particular limitation on the method by which the oscillation command generation unit 12 decays the oscillation amplitude when the oscillation stop is notified. For example, the oscillation command generation unit 12 can apply a filter to the oscillation amplitude immediately before stopping the oscillation to gradually decay the oscillation amplitude. Alternatively, the oscillation command generation unit 12 can also gradually decay the oscillation amplitude by decreasing the oscillation amplitude by a specified value each time immediately before stopping the oscillation.

[0036] A specific example is given to more specifically explain the method by which the oscillation command generation unit 12 decays the oscillation amplitude when the oscillation stop is notified.

[0037] For example, when the control cycle of the control device 1 of the machine tool of the present embodiment is set to 1 ms, the oscillation command generation unit 12 can be set to decay the oscillation amplitude in several control cycles. For example, in order to decay in 4 control cycles (4 ms), a first-order low-pass filter with a time constant of 4 / 3 ms can be applied, or the specified value of the decay can be set to 1 / 4 of the (current) oscillation amplitude.

[0038] In addition, the decay time can also be determined according to the oscillation frequency. For example, when the oscillation frequency is 20 Hz, the oscillation period is 1 / 20 = 50 ms. When it is desired to decay within 1 / 4 cycle, it can be set to decay in 50 / 4 = 12.5 ms. And when the oscillation frequency changes, it can be configured to change the time accordingly.

[0039] In addition, regarding the time constant and the specified value of the above filter, for example, they can be set by input from a program, or can be set by parameters. As a result, the time constant and the specified value of the above filter can be set to arbitrary values, and the oscillation amplitude can be reliably decayed.

[0040] The oscillation command generation unit 12 can correct the oscillation amplitude and the oscillation phase so that the oscillation can stop at an arbitrary timing notified by an external notification. That is, the oscillation command generation unit 12 can, in addition to the timing when the oscillation stop is notified from the oscillation stop determination unit 13, also correct the oscillation amplitude and the oscillation phase in accordance with an arbitrary timing when the oscillation stop is notified in advance by an external notification, thereby gradually decaying the oscillation amplitude. As a result, the oscillation amplitude can be decayed and the oscillation can be stopped at an arbitrary timing notified by an external notification, and the impact generated in the machine tool can be suppressed, thereby suppressing the deterioration of the machining accuracy.

[0041] In addition, the swing command generation unit 12 may stop updating the swing phase at the timing when the swing stop determination unit 13 notifies the swing stop. Alternatively, the swing command generation unit 12 may rapidly advance the phase to a specific swing phase after the swing stop notification from the swing stop determination unit 13. Hereinafter, with reference to Figure 4 These methods for updating and advancing the swing phase will be described in detail.

[0042] Here, Figure 4 A method for updating and advancing the swing phase in swing cutting for explaining an embodiment of the present disclosure. In Figure 4 Specifically, a sine wave-shaped swing command is shown. In Figure 4 The horizontal axis represents the swing phase (°), and the vertical axis represents the position (mm).

[0043] When generating Figure 4 the sine wave-shaped swing command shown, the magnitude of the swing command for each swing phase changes. Therefore, if the swing phase is continuously updated after the swing stop notification, the swing command also changes according to the swing phase, and thus the convergence speed of the swing command depends on the swing phase at the time of the swing stop notification. Therefore, if the update of the swing phase is stopped when the swing stop is notified, the convergence speed of the swing command cannot be increased beyond the attenuation speed of the swing amplitude, but it is possible to prevent the swing command from becoming larger than at the time of the swing stop notification. In particular, if it is Figure 4 the swing command shown, when the swing stop is notified while the swing phase is 0 to 180°, that is, when the swing command increases (the absolute value of the swing command increases), by stopping the update of the swing phase, it is possible to prevent the swing command from becoming larger than at the time of the swing stop notification and to accelerate the convergence of the swing command.

[0044] In addition, in Figure 4 the case of the swing command shown, the swing command is the smallest at the swing phase of 0 (360)°. Therefore, when the swing stop is notified, by rapidly advancing the swing phase to 0 (360)° and then stopping the update of the swing phase, the convergence speed of the swing command can be maximized.

[0045] Figure 5 Shows the position command and the position deviation when the update of the swing phase is stopped at the time of the swing stop notification in the swing cutting of an embodiment of the present disclosure. In Figure 5 the horizontal axis represents time (seconds), the first axis (left) of the vertical axis represents the position command (overlay command) (mm), and the second axis (right) represents the position deviation (mm). As Figure 5As shown, by stopping the update of the swing phase at the swing stop notification, the position command after the overlapping swing command, i.e., the overlapping command, can converge quickly, and the change in the position deviation can be smoothed. Therefore, the swing can be smoothly stopped at an arbitrary timing without impairing the chip cutting property, and thus the impact generated by the machine tool can be suppressed, thereby suppressing the deterioration of the life of the cutting tool and the like and the accuracy of the workpiece being machined.

[0046] In addition, Figure 6 This shows the position command and the position deviation when the swing phase is rapidly advanced after the swing stop notification and stopped at a specific phase (e.g., swing phase 0°) in the swing cutting of an embodiment of the present disclosure. In Figure 6 the horizontal axis represents time (seconds), and the first axis (left) of the vertical axis represents the position command (overlapping command) (mm), and the second axis (right) represents the position deviation (mm). As Figure 6 shown, by rapidly advancing the swing phase to a specific phase such as 0° and stopping after the swing stop notification, the position command after the overlapping swing command, i.e., the overlapping command, can converge quickly, and the change in the position deviation can be smoothed. Therefore, similar to the Figure 5 case, the swing can be smoothly stopped at an arbitrary timing without impairing the chip cutting property, and thus the impact generated by the machine tool can be suppressed, thereby suppressing the deterioration of the life of the cutting tool and the like and the accuracy of the workpiece being machined.

[0047] According to the control device 1 of the machine tool of the present embodiment described above, the following effects are achieved.

[0048] In the control device 1 of the machine tool of the present embodiment, a swing stop determination unit 13 for determining the timing of swing stop is provided, and a swing command generation unit 12 is provided. The swing command generation unit 12 gradually attenuates the swing amplitude starting from the timing of the determined swing stop notified by the swing stop determination unit 13.

[0049] That is, in the control device 1 of the machine tool of the present embodiment, instead of attenuating the swing amplitude according to the movement command or the remaining movement distance as in the past, the swing amplitude is gradually attenuated from the timing of the notified swing stop until the swing stops. Thus, by gradually attenuating the swing amplitude at the timing of the notified swing stop, the position command does not change abruptly, and the change in the position deviation becomes smooth. Therefore, the impact generated in the machine tool can be reduced, thereby suppressing the deterioration of the life of the cutting tool and the like and the accuracy of the workpiece being machined. Therefore, according to the control device 1 of the machine tool of the present embodiment, the swing can be smoothly stopped at an arbitrary timing without impairing the chip cutting property, and the impact generated by the machine tool can be suppressed, thereby suppressing the deterioration of the life of the cutting tool and the like and the accuracy of the workpiece being machined.

[0050] In addition, in the present embodiment, it is configured that at the timing when the swing stop is notified, a filter is applied to the swing amplitude immediately before the swing stops, or the swing amplitude immediately before the swing stops is decreased by a prescribed value each time. Thereby, the swing amplitude can be reliably gradually attenuated until the swing stops.

[0051] Moreover, in the present embodiment, it is configured that at the timing when the swing stop is notified, the update of the swing phase is stopped, or at the timing when the swing stop is notified, the swing phase is quickly advanced to a specific phase. Thereby, the swing command and the overlap command can be attenuated more quickly.

[0052] Furthermore, the present disclosure is not limited to the above-described mode, and modifications and improvements within the scope that can achieve the object of the present disclosure are included in the present disclosure.

[0053] Description of reference numerals

[0054] 1 Control device of machine tool

[0055] 10 Servo control device

[0056] 11 First adder

[0057] 12 Swing command generation unit

[0058] 13 Swing stop determination unit

[0059] 14 Second adder

[0060] 15 Learning controller (learning control unit)

[0061] 16 Third adder (learning control unit)

[0062] 17 Position and velocity control unit (control unit)

[0063] 20 Position command generation unit

[0064] 30 Motor.

Claims

1. A control device for a machine tool, which performs machining while relatively swinging a tool and a workpiece, Characterized in that, The control device includes: A swing command generation unit that generates a swing command based on swing conditions; A swing stop determination unit that determines the timing of swing stop; And A control unit that relatively swings the tool and the workpiece based on an overlapping command generated by overlapping the movement command with the swing command, When the absolute value of the swing command increases, the swing command generation unit stops updating the swing phase upon receiving notification of the swing stop timing from the swing stop determination unit, thereby gradually attenuating the swing amplitude.

2. The control device for a machine tool according to claim 1, characterized in that, The swing command generation unit gradually attenuates the swing amplitude by applying a filter to the swing amplitude immediately before stopping the swing.

3. The control device for a machine tool according to claim 1, characterized in that, The swing command generation unit gradually attenuates the swing amplitude by decreasing the swing amplitude immediately before stopping the swing by a prescribed value each time.

4. The control device for a machine tool according to any one of claims 1 to 3, characterized in that, The swing stop determination unit determines the timing of swing stop based on machining conditions.

5. The control device for a machine tool according to any one of claims 1 to 3, characterized in that, The swing stop determination unit determines the timing of swing stop according to an external notification.

6. The control device for a machine tool according to claim 5, characterized in that, The swing command generation unit corrects the swing amplitude and the swing phase so that the swing can be stopped at any timing notified by an external notification.

7. The control device for a machine tool according to any one of claims 1 to 3, characterized in that, The control device further includes a learning control unit that calculates a correction amount of the overlapping command based on the overlapping command and corrects the overlapping command by adding the calculated correction amount to the overlapping command.

8. The control device for a machine tool according to claim 4, characterized in that, The control device further includes a learning control unit that calculates a correction amount of the overlapping command based on the overlapping command and corrects the overlapping command by adding the calculated correction amount to the overlapping command.

9. The control device for a machine tool according to claim 5, characterized in that, The control device further includes a learning control unit that calculates a correction amount of the overlapping command based on the overlapping command and corrects the overlapping command by adding the calculated correction amount to the overlapping command.

10. The control device for a machine tool according to claim 6, characterized in that, The control device further includes a learning control unit that calculates a correction amount of the overlapping command based on the overlapping command and corrects the overlapping command by adding the calculated correction amount to the overlapping command.

11. A control device for a machine tool, which performs machining while relatively swinging a tool and a workpiece, Characterized in that, The control device includes: A swing command generation unit that generates a swing command based on swing conditions; A swing stop determination unit that determines the timing of swing stop; and A control unit that causes the tool to swing relative to the workpiece based on an overlapping instruction generated by overlapping the movement instruction with the swing instruction. The swing instruction generation unit stops updating the phase after quickly advancing the phase to a specific swing phase with the smallest absolute value of the swing instruction at the timing when swing stop is notified from the swing stop determination unit, thereby gradually attenuating the swing amplitude.

12. The control device for a machine tool according to claim 11, wherein The swing instruction generation unit gradually attenuates the swing amplitude by applying a filter to the swing amplitude immediately before stopping the swing.

13. The control device for a machine tool according to claim 11, wherein The swing instruction generation unit gradually attenuates the swing amplitude by decreasing the swing amplitude immediately before stopping the swing by a predetermined value each time.

14. The control device for a machine tool according to any one of claims 11 to 13, wherein The swing stop determination unit determines the timing of swing stop based on machining conditions.

15. The control device for a machine tool according to any one of claims 11 to 13, wherein The swing stop determination unit determines the timing of swing stop according to an external notification.

16. The control device for a machine tool according to claim 15, wherein The swing instruction generation unit corrects the swing amplitude and the swing phase so that the swing can be stopped at any timing notified by the external notification.

17. The control device for a machine tool according to any one of claims 11 to 13, wherein The control device further includes a learning control unit that calculates a correction amount of the overlapping instruction based on the overlapping instruction and corrects the overlapping instruction by adding the calculated correction amount to the overlapping instruction.

18. The control device for a machine tool according to claim 14, wherein The control device further includes a learning control unit that calculates a correction amount of the overlapping instruction based on the overlapping instruction and corrects the overlapping instruction by adding the calculated correction amount to the overlapping instruction.

19. The control device for a machine tool according to claim 15, wherein The control device further includes a learning control unit that calculates a correction amount of the overlapping instruction based on the overlapping instruction and corrects the overlapping instruction by adding the calculated correction amount to the overlapping instruction.

20. The control device for a machine tool according to claim 16, wherein The control device further includes a learning control unit that calculates a correction amount of the overlapping instruction based on the overlapping instruction and corrects the overlapping instruction by adding the calculated correction amount to the overlapping instruction.

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