Machine tool control device

Abstract

A machine tool control device is provided that can reduce the adverse effects caused by sudden changes in the periodic variation of the spindle rotation speed while maintaining the effect of suppressing regenerative self-excited chatter. The machine tool control device includes: a variation command calculation unit that generates variation commands based on a speed command of the spindle motor in the machine tool and variation conditions for periodically varying the rotation speed of the spindle motor; and a speed control unit that controls the rotation speed of the spindle motor based on the speed command and the variation command, wherein, when the variation conditions change, the variation command calculation unit generates the variation command that gradually changes the amplitude and / or the frequency of the periodically varying rotation speed.

Description

Technical Field

[0001] This disclosure relates to a control device for a machine tool. Background Technology

[0002] During machining on a machine tool, chatter sometimes occurs continuously between the tool and the workpiece. Based on the primary cause of this vibration, chatter is classified into forced chatter and self-excited chatter. Forced chatter is generated by a forced vibration source, while self-excited chatter occurs when the dynamic characteristics of the machine tool overlap with the cutting process and meet specified conditions, without a specific vibration source. Regenerative self-excited chatter is caused by variations in the thickness of the cutting chips.

[0003] Previously, a technique for suppressing regenerative self-excited chatter by periodically varying the rotational speed of the spindle in a machine tool was known (see, for example, Patent Document 1).

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2012-091283 Summary of the Invention

[0007] The problem the invention aims to solve

[0008] However, in the aforementioned technologies, sudden changes in the periodic variations of the spindle rotation speed can lead to adverse effects such as mechanical shock and deterioration of the machined surface quality due to excessive speed deviation. Therefore, there is a need for a machine tool control device that can reduce the adverse effects caused by sudden changes in the periodic variations of the spindle rotation speed while maintaining the effect of suppressing regenerative self-excited chatter.

[0009] Solution for solving the problem

[0010] The control device for the machine tool disclosed herein includes: a variation command calculation unit that generates variation commands based on a speed command of a spindle motor in the machine tool and variation conditions for periodically varying the rotational speed of the spindle motor; and a speed control unit that controls the rotational speed of the spindle motor based on the speed command and the variation command, wherein, when the variation conditions change, the variation command calculation unit generates the variation command that gradually changes the amplitude and / or the frequency of the periodically varying rotational speed.

[0011] The effects of the invention

[0012] According to this disclosure, it is possible to reduce the adverse effects caused by sudden changes in the periodic variation of the spindle rotation speed while maintaining the effect of suppressing regenerative self-excited chatter. Attached Figure Description

[0013] Figure 1 This is a diagram showing an outline of the machine tool according to the first embodiment.

[0014] Figure 2 This is a flowchart illustrating the processing flow of the motor control device according to the first embodiment.

[0015] Figure 3 This is a graph showing the time history when the periodic variation of the spindle motor's rotational speed (spindle speed) is stopped in the first embodiment.

[0016] Figure 4 This is a graph showing the time history when the periodic changes in the spindle motor's rotational speed (spindle speed) were stopped.

[0017] Figure 5 This is a diagram showing an outline of the machine tool involved in the second embodiment.

[0018] Figure 6 This is a flowchart illustrating the processing flow of the motor control device according to the second embodiment.

[0019] Figure 7 This is a graph showing the time history when the amplitude of the periodically varying rotational speed (spindle speed) in the spindle motor is increased in the second embodiment.

[0020] Figure 8 This is a graph showing the time history when the amplitude of the periodically varying rotational speed (spindle speed) in the spindle motor is increased.

[0021] Figure 9 This is a graph showing the time history when the amplitude of the periodically varying rotational speed (spindle speed) in the spindle motor is reduced in the second embodiment.

[0022] Figure 10 This is a graph showing the time history when the amplitude of the periodically varying rotational speed (spindle speed) in the spindle motor is reduced.

[0023] Figure 11 This is a graph showing the time history when the frequency of the periodically varying rotational speed (spindle speed) in the spindle motor is increased in the second embodiment.

[0024] Figure 12This is a graph showing the time history when the frequency of the periodically varying rotational speed (spindle speed) in the spindle motor is increased.

[0025] Figure 13 This is a graph showing the time history when the frequency of the periodically varying rotational speed (spindle speed) in the spindle motor is reduced in the second embodiment.

[0026] Figure 14 This is a graph showing the time history when the frequency of the periodically changing rotational speed (spindle speed) in the spindle motor is reduced. Detailed Implementation

[0027] First, the first embodiment of this disclosure will be described. Figure 1 This is a diagram showing an outline of the machine tool according to the first embodiment.

[0028] The machine tool is a device that controls a motor control unit 1 based on speed commands from a numerical control unit 2, thereby rotating a spindle motor 3 to perform prescribed machining operations such as cutting. This machine tool suppresses regenerative self-excited chatter by periodically varying the rotational speed of the spindle motor 3, that is, by causing the rotational speed of the spindle motor 3 to vibrate in a sinusoidal wave.

[0029] The motor control device 1 includes a change command calculation unit 11, a change stop determination unit 12, a speed control unit 14, a current control unit 16, and a current detection unit 17.

[0030] The variation command calculation unit 11 generates variation commands based on the speed command of the spindle motor 3 in the machine tool and the variation conditions (amplitude and / or frequency) for periodically varying the rotational speed of the spindle motor 3, and outputs them as signals. When the variation conditions change, the variation command calculation unit 11 generates variation commands that gradually change the amplitude of the periodically varying rotational speed of the spindle motor 3, and outputs them as signals. Specifically, when the variation command calculation unit 11 receives a stop command signal as a variation condition from the variation stop determination unit 12, it generates variation commands that cause the amplitude of the periodically varying rotational speed of the spindle motor 3 to decrease (gradually decrease) and become zero, and outputs them as signals. The amount of decrease in the amplitude of the periodically varying rotational speed of the spindle motor 3 is determined by a predetermined amount of change (time constant), a value input from the machining program, or the value of a set parameter. The variation conditions are set by input from the machining program or set parameters.

[0031] The variable stop determination unit 12 generates a stop command that stops the variable rotation speed of the spindle motor 3 based on a predetermined trigger, and outputs it as a signal. The predetermined trigger can be a signal input from an external source such as the numerical control device 2, an input from the machining program, or a set parameter.

[0032] Reference numeral 13 indicates that the value obtained by adding the value of the speed command output as a signal from the spindle speed command 21 to the value of the variable command output as a signal from the variable command calculation unit 11 and subtracting the value of the actual speed feedback output as a signal from the speed detection unit 31 is input as a signal to the speed control unit 14.

[0033] The speed control unit 14 generates commands for controlling the rotational speed of the spindle motor 3 based on speed commands and variation commands, and outputs them as signals.

[0034] Reference numeral 15 indicates that the value obtained by subtracting the actual current feedback value from the current detection unit 17 as a signal output from the value of the command output by the speed control unit 14 is input as a signal to the current control unit 16.

[0035] The current control unit 16 generates a voltage command for driving the spindle motor 3 based on the input signal and outputs it as a signal.

[0036] The current detection unit 17 detects the signal that is the current value of the spindle motor 3, and outputs the detection result as a signal for actual current feedback.

[0037] The numerical control device 2 has a spindle speed command 21. The spindle speed command 21 generates a speed command for the spindle motor 3 and outputs it as a signal.

[0038] The spindle motor 3 rotates under the control of the motor control device 1. The speed detection unit 31 detects the rotational speed of the spindle motor 3 and outputs the detection result as a signal for actual speed feedback. The speed detection unit 31 employs an encoder or the like.

[0039] Figure 2 This is a flowchart illustrating the processing flow of the motor control device 1 according to the first embodiment. Figure 2 The process shown is repeated according to the cycle (control cycle) for generating change instructions.

[0040] If the change instruction calculation unit 11 receives a signal from the change stop determination unit 12 as a change condition (if "yes" is in step S11), the process proceeds to step S12. On the other hand, if the change instruction calculation unit 11 does not receive a signal from the change stop determination unit 12 as a change condition (if "no" is in step S11), the process proceeds to step S13.

[0041] In step S12, the value (a-ax) obtained by reducing the amplitude a (amplitude a in the variation command) of the periodically changing rotation speed of the spindle motor 3 by a specified change amount ax (x: a positive value less than 1) is set as the new amplitude a, and then the process proceeds to step S13.

[0042] If the amplitude 'a' of the periodically varying rotational speed of the spindle motor 3 decays and becomes zero (if "Yes" is true in step S13), proceed to step S15. On the other hand, if the amplitude 'a' of the periodically varying rotational speed of the spindle motor 3 does not become zero (if "No" is true in step S13), proceed to step S14.

[0043] In step S14, the variation command calculation unit 11 generates a variation command based on the amplitude 'a' calculated in step S12. On the other hand, in step S15, the variation command calculation unit 11 does not generate a variation command.

[0044] Figure 3 This is a graph showing the time history when the periodic variation of the rotational speed (spindle speed) of the spindle motor 3 is stopped in the first embodiment. (See diagram below.) Figure 3 As shown, when the spindle speed is 1000±500 [min] -1 When such periodic variations cease, the amplitude of the spindle speed gradually decays and becomes zero. In this way, the steepness of the speed change is softened, thus reducing the adverse effects on the quality of the machined surface.

[0045] on the other hand, Figure 4 This is a graph showing the time history when the periodic changes in the spindle motor's rotational speed (spindle speed) were stopped. For example... Figure 4 As shown, previously the spindle speed was 1000±500 [min] -1 When this periodic variation stops, the amplitude of the spindle speed suddenly becomes zero. In the past, this would have caused a mechanical shock due to the abrupt speed change, leading to a deterioration in the quality of the machined surface due to excessive speed deviation.

[0046] As explained above, the motor control device 1 according to the first embodiment includes: a variation command calculation unit 11, which generates variation commands based on the speed command of the spindle motor 3 in the machine tool and variation conditions for periodically varying the rotational speed of the spindle motor 3; and a speed control unit 14, which controls the rotational speed of the spindle motor 3 based on the speed command and the variation command, wherein, when the variation conditions change, the variation command calculation unit 11 generates variation commands that gradually change the amplitude of the periodically varying rotational speed.

[0047] This makes the steepness of speed changes more gradual, thus reducing the adverse effects caused by sudden changes in the periodic variation of the rotational speed of the spindle motor 3 while maintaining the effect of suppressing regenerative self-excited chatter.

[0048] In addition, the motor control device 1 includes a change stop determination unit 12, which generates a stop command to stop the change in rotational speed based on a predetermined trigger. When the change command calculation unit 11 receives the stop command as a change condition, it generates a change command to attenuate the amplitude of the periodically changing rotational speed and make it zero.

[0049] Therefore, especially when stopped, it is possible to reduce the adverse effects caused by the sudden stop of the periodic variation in the rotational speed of the spindle motor 3 while maintaining the effect of suppressing regenerative self-excited chatter.

[0050] Next, the second embodiment of this disclosure will be described. Figure 5 This is a diagram showing an outline of the machine tool according to the second embodiment. Furthermore, in the description of the second embodiment, descriptions of structures, functions, and effects common to the first embodiment are appropriately omitted by using the same reference numerals, etc.

[0051] Figure 5 The machine tool shown differs from the machine tool involved in the first embodiment in that, Figure 5 The machine tool shown is equipped with a motor control device 1A instead of a motor control device 1. The difference between the motor control device 1A and the motor control device 1 is that the motor control device 1A is equipped with a change condition setting unit 12A instead of a change stop determination unit 12.

[0052] When the change conditions change, the change command calculation unit 11 generates a change command that gradually changes the amplitude and / or frequency of the periodically changing rotational speed. Specifically, when the change conditions change, the change command calculation unit 11 compares the values ​​of the amplitude and / or frequency of the periodically changing rotational speed before the change with the values ​​after the change. If the value after the change is greater than the value before the change, the change command calculation unit 11 generates a change command that gradually increases the amplitude and / or frequency of the periodically changing rotational speed. If the value after the change is less than the value before the change, the change command calculation unit 11 generates a change command that decreases the amplitude and / or frequency of the periodically changing rotational speed.

[0053] The variable condition setting unit 12A sets the speed command of the spindle motor 3 in the machine tool and the variable conditions (amplitude and / or frequency) for periodically changing the rotational speed of the spindle motor 3, and outputs them as signals. The variable conditions are set using inputs from the machining program, set parameters, etc.

[0054] Figure 6 This is a flowchart illustrating the processing flow of the motor control device 1A according to the second embodiment. Figure 6 The process shown is repeated according to the cycle (control cycle) for generating change instructions.

[0055] In step S21, the variation command calculation unit 11 compares the amplitude setting value a0 received from the variation condition setting unit 12A as a variation condition signal with the current amplitude a. If the amplitude setting value a0 is greater than the current amplitude a, proceed to step S22. If the amplitude setting value a0 is the same as the current amplitude a, proceed to step S24. If the amplitude setting value a0 is less than the current amplitude a, proceed to step S23.

[0056] In step S22, the value (a+ax) obtained by increasing the amplitude a of the periodically changing rotation speed of the spindle motor 3 by a specified change ax (x: a positive value less than 1) is set as the new amplitude a, and then the process proceeds to step S24.

[0057] In step S23, the value (a-ax) obtained by reducing the amplitude a of the periodically changing rotational speed of the spindle motor 3 by a specified change ax (x: a positive value less than 1) is set as the new amplitude a, and then the process proceeds to step S24.

[0058] In step S24, the variation command calculation unit 11 compares the frequency setting value f0 received from the variation condition setting unit 12A as a variation condition signal with the current frequency f. If the frequency setting value f0 is greater than the current frequency f, proceed to step S25. If the frequency setting value f0 is the same as the current frequency f, proceed to step S27. If the frequency setting value f0 is less than the current amplitude f, proceed to step S26.

[0059] In step S25, the value (f+fx) obtained by increasing the frequency f of the periodically changing rotation speed of the spindle motor 3 by a specified change amount fx (x: a positive value less than 1) is set as the new amplitude f, and then the process proceeds to step S27.

[0060] In step S26, the value (f-fx) obtained by reducing the frequency f of the periodically changing rotation speed of the spindle motor 3 by a specified change amount fx (x: a positive value less than 1) is set as the new amplitude f, and then the process proceeds to step S27.

[0061] In step S27, the variation command calculation unit 11 generates a variation command based on amplitude a and frequency f.

[0062] Figure 7 This is a graph showing the time history when the amplitude of the periodically varying rotational speed (spindle speed) in the spindle motor 3 is increased in the second embodiment. (See diagram below.) Figure 7 As shown, the spindle speed in the spindle motor 3 is periodically varied at 1000 ± 200 [min]. -1 Such an increase in amplitude is used to make the spindle speed 1000±500 [min] -1 In this case, the amplitude gradually increases. That is, after the amplitude changes, the spindle speed of the spindle motor in this embodiment changes smoothly.

[0063] on the other hand, Figure 8 This is a graph showing the time history when the amplitude of the periodically varying rotational speed (spindle speed) in the spindle motor is increased. For example... Figure 8 As shown, the spindle speed of the spindle motor 3 is periodically varied at 1000 ± 200 [min]. -1 Such an increase in amplitude is used to make the spindle speed 1000±500 [min] -1 In this case, the amplitude increases sharply. That is, after the amplitude changes, the spindle speed of the spindle motor changes drastically.

[0064] Figure 9 This is a graph showing the time history when the amplitude of the periodically varying rotational speed (spindle speed) in the spindle motor 3 is reduced in the second embodiment. (See diagram below.) Figure 9 As shown, the spindle speed in the spindle motor 3 is periodically varied at 1000 ± 500 [min]. -1 The amplitude was reduced in that way to make the spindle speed 1000±200 [min] -1 In the case of [missing information], the amplitude decreases (gradually decreases). That is, after the amplitude changes, the rotational speed of the spindle motor 3 in this embodiment changes smoothly.

[0065] on the other hand, Figure 10 This is a graph showing the time history when the amplitude of the periodically varying rotational speed (spindle speed) in the spindle motor is reduced. For example... Figure 10 As shown, the spindle speed, which is periodically varied in the spindle motor, is 1000 ± 500 [min]. -1 The amplitude was reduced in that way to make the spindle speed 1000±200 [min] -1 In this case, the amplitude suddenly decreases. That is, after the amplitude changes, the spindle speed of the spindle motor changes drastically.

[0066] Figure 11 This is a graph showing the time history when the frequency of the periodically varying rotational speed (spindle speed) in the spindle motor 3 is increased in the second embodiment. (As shown) Figure 11 As shown, the spindle speed in the spindle motor 3 is periodically varied at 1000 ± 500 [min]. -1 As the period 2 [Hz] increases to 8 [Hz], the frequency gradually increases. That is, after the frequency changes, the spindle speed of the spindle motor 3 in this embodiment changes smoothly.

[0067] on the other hand, Figure 12 This is a graph showing the time history when the frequency of the periodically varying rotational speed (spindle speed) in the spindle motor is increased. For example... Figure 12 As shown, the spindle speed, which is periodically varied in the spindle motor, is 1000 ± 500 [min]. -1 When the period of the spindle motor is increased from 2 Hz to 8 Hz, the frequency increases dramatically. That is, after the frequency change, the spindle speed of the spindle motor changes drastically.

[0068] Figure 13 This is a graph showing the time history when the frequency of the periodically varying rotational speed (spindle speed) in the spindle motor 3 is reduced in the second embodiment. (As shown) Figure 13 As shown, the spindle speed in the spindle motor 3 is periodically varied at 1000 ± 500 [min]. -1 When the period of the spindle motor 3 decreases from 8 Hz to 2 Hz, the frequency decays (gradually decreases). That is, after the frequency changes, the spindle speed of the spindle motor 3 in this embodiment changes smoothly.

[0069] on the other hand, Figure 14 This shows the time history when the frequency of the periodically varying rotational speed (spindle speed) in the spindle motor was reduced. For example... Figure 14 As shown, the spindle speed, which is periodically varied in the spindle motor, is 1000 ± 500 [min]. -1 When the period of the spindle motor is reduced from 8 Hz to 2 Hz, the frequency decreases drastically. That is, after the frequency change, the spindle speed of the spindle motor changes drastically.

[0070] As explained above, the motor control device 1A according to the second embodiment includes: a variation command calculation unit 11, which generates variation commands based on the speed command of the spindle motor 3 in the machine tool and variation conditions for periodically varying the rotational speed of the spindle motor 3; and a speed control unit 14, which controls the rotational speed of the spindle motor 3 based on the speed command and the variation command, wherein, when the variation conditions change, the variation command calculation unit 11 generates variation commands that gradually change the amplitude of the periodically varying rotational speed and / or the frequency of the periodically varying rotational speed.

[0071] Therefore, according to the motor control device 1A, the steepness of the speed change is made gentler, so that while maintaining the effect of suppressing regenerative self-excited chatter, the adverse effects caused by the sudden change of the periodic variation of the rotational speed of the spindle motor 3 can be reduced.

[0072] Furthermore, when the change conditions change, the change instruction calculation unit 11 compares the values ​​before and after the change of the amplitude and / or frequency of the periodically changing rotational speed. When the value after the change is greater than the value before the change, the change instruction calculation unit 11 generates a change instruction that gradually increases the amplitude and / or frequency of the periodically changing rotational speed. When the value after the change is less than the value before the change, the change instruction calculation unit 11 generates a change instruction that decreases the amplitude and / or frequency of the periodically changing rotational speed.

[0073] Therefore, according to the motor control device 1A, it is possible to more reliably maintain the effect of suppressing regenerative self-excited chatter while reducing the adverse effects caused by sudden changes in the periodic variation of the rotational speed of the spindle motor 3.

[0074] The embodiments of the present invention have been described above. However, the motor control devices 1 and 1A described above can be implemented by hardware, software, or a combination thereof. Furthermore, the control method performed by the motor control devices 1 and 1A described above can also be implemented by hardware, software, or a combination thereof. Moreover, implementation by software means implementation by reading and executing a program by a computer.

[0075] Explanation of reference numerals in the attached figures

[0076] 1. 1A: Motor control device (machine tool control device); 11: Variable command calculation unit; 12: Variable stop determination unit; 12A: Variable condition setting unit; 14: Speed ​​control unit; 16: Current control unit; 17: Current detection unit; 2: Numerical control device; 21: Spindle speed command; 3: Spindle motor; 31: Speed ​​detection unit.

Claims

1. A control device for a machine tool, comprising: The variation command calculation unit generates variation commands based on the speed command of the spindle motor in the machine tool and the variation conditions for periodically varying the rotational speed of the spindle motor. The speed control unit controls the rotational speed of the spindle motor based on the speed command and the change command; as well as The change-stop determination unit generates a stop command to halt the change in rotational speed based on a predetermined trigger. When the change conditions change, the change command calculation unit generates a change command that gradually changes the amplitude and / or frequency of the periodically changing rotational speed. Upon receiving the stop command as a condition for the change, the change command calculation unit generates a change command that causes the amplitude of the periodically changing rotational speed to decay to zero.

2. A control device for a machine tool, comprising: The variation command calculation unit generates variation commands based on the speed command of the spindle motor in the machine tool and variation conditions for periodically varying the rotational speed of the spindle motor; and The speed control unit controls the rotational speed of the spindle motor based on the speed command and the variation command. in, When the changing conditions change, the change command calculation unit generates a change command that gradually changes the amplitude and / or frequency of the periodically changing rotational speed. When the change condition changes, the change instruction calculation unit compares the values ​​before and after the change of the amplitude and / or frequency of the periodically changing rotational speed. If the value after the change is greater than the value before the change, the change instruction calculation unit generates a change instruction that gradually increases the amplitude and / or frequency of the periodically changing rotational speed. If the value after the change is less than the value before the change, the change instruction calculation unit generates a change instruction that decreases the amplitude and / or frequency of the periodically changing rotational speed.

Images