Machine tool control device

Abstract

A control device for a machine tool is provided that can reliably cut chips while suppressing machine tool vibration. The control device (1) for a machine tool that performs machining by oscillating the tool relative to the workpiece includes: an oscillation command generation unit (13) that calculates the oscillation amplitude and oscillation frequency based on machining conditions and generates an oscillation command; and a position and speed control unit (17) that oscillates the tool relative to the workpiece based on an overlap command generated by overlapping the oscillation command generated by the oscillation command generation unit (13) with a position command or position deviation, wherein the oscillation command generation unit (13) changes at least one of the oscillation amplitude and oscillation frequency during machining.

Description

Technical Field

[0001] This invention relates to a control device for machine tools. Background Technology

[0002] Currently, in machining processes such as hole drilling or turning, the load is prone to change at the start of cutting, making it difficult to break the chips using a cutter. Therefore, oscillating cutting is sometimes used. For example, Patent Document 1 describes a cutting process in which the cutting tool oscillates relative to the workpiece while cutting, thereby breaking the chips.

[0003] Prior art literature

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2017-56515 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] However, in order to reliably break up chips at the start of cutting, it is necessary to increase the oscillation amplitude. But if machining continues with the original oscillation amplitude after the machining has stabilized, the machine tool will generate large vibrations. Machine tool vibration can adversely affect machining accuracy, and therefore it is an important issue that needs to be addressed.

[0008] Therefore, in the control device of a machine tool that performs machining by oscillating the tool relative to the workpiece, it is desirable to be able to reliably cut the chips while suppressing machine tool vibration.

[0009] Methods for solving problems

[0010] One aspect of this disclosure is a control device for a machine tool that performs machining by oscillating a tool relative to a workpiece. The control device comprises: an oscillation command generation unit that calculates the oscillation amplitude and oscillation frequency based on machining conditions and generates an oscillation command; and a control unit that oscillates the tool relative to the workpiece based on an overlap command generated by overlapping the oscillation command generated by the oscillation command generation unit with a position command or position deviation. The oscillation command generation unit changes at least one of the oscillation amplitude and the oscillation frequency during machining.

[0011] Invention Effects

[0012] According to this disclosure, a control device for a machine tool can be provided that can reliably crush chips while suppressing machine tool vibration by changing the oscillation conditions (oscillation amplitude, oscillation frequency) to match the machining process. Attached Figure Description

[0013] Figure 1This is a functional block diagram of a machine tool control device according to one embodiment of the present disclosure.

[0014] Figure 2 This is a diagram showing the change in oscillation conditions during the hole-making process in Example 1.

[0015] Figure 3 This is a diagram showing the change in oscillation conditions during the hole-making process in Example 2.

[0016] Figure 4 This is a diagram showing the change in oscillation conditions during the hole-making process in Example 3.

[0017] Figure 5 This is a diagram showing the change in the oscillation conditions during the hole-making process in Example 4.

[0018] Figure 6 This is a diagram showing the change in oscillation conditions during the turning process in Example 5.

[0019] Figure 7 This is a diagram showing the change in oscillation conditions during the turning process in Example 6. Detailed Implementation

[0020] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0021] Figure 1 This is a functional block diagram of a machine tool control device 1 according to one embodiment of the present disclosure. Figure 1 As shown, the control device 1 of the machine tool in this embodiment is configured to include a servo control device 10 to drive and control the motor 30 used to drive the feed axis.

[0022] like Figure 1 As shown, the machine tool control device 1 of this embodiment includes an adder 11, an accumulator 12, a swing command generation unit 13, an adder 14, a learning controller 15, an adder 16, and a position and speed control unit 17.

[0023] In this embodiment, the machine tool control device 1 generates drive commands for the electric motor 30 through a machining program. For example... Figure 1 As shown, the generated drive command (position command) is input into the adder 11 of the servo control device 10, which will be described later.

[0024] Additionally, for example, the machining program of the machine tool control device 1 in this embodiment is generated by using a CAM system (not shown) to generate machining shape setting tool information, tool motion information, etc., from a CAD system (also not shown).

[0025] Adder 11 calculates the position deviation. Specifically, adder 11 calculates the difference between the position feedback obtained by the position detection of the encoder of the feed axis motor 30 and the position command, i.e., the position deviation.

[0026] Accumulator 12 calculates the cumulative value of the position deviation. Specifically, accumulator 12 calculates the cumulative value of the position deviation by accumulating the position deviation calculated by adder 11.

[0027] The swing command generation unit 13 calculates the swing amplitude and swing frequency according to the processing conditions and generates a swing command. That is, the swing command generation unit 13 calculates the swing conditions consisting of the swing amplitude and swing frequency according to the processing conditions and generates a swing command based on the calculated swing conditions.

[0028] Furthermore, the oscillation command generation unit 13 of this embodiment is characterized by changing at least one of the oscillation amplitude and oscillation frequency constituting the oscillation conditions during the machining process. Here, if the oscillation amplitude multiplier is set to K (times) and the feed rate is set to F (mm / revolution), then the oscillation amplitude K' (mm) is represented by K' = F × K. Similarly, if the oscillation frequency multiplier is set to I (times) and the spindle speed is set to S (minutes), then... -1 If the oscillation frequency I' (Hz) is represented by I' = S / 60 × I, then the changes in oscillation amplitude and oscillation frequency in this embodiment also include changes in the oscillation amplitude multiple and the oscillation frequency multiple.

[0029] Thus, in this embodiment, by changing the oscillation conditions during machining to match the machining process, machine tool vibration can be suppressed, and chips can be reliably shredded. The machining process in this embodiment includes not only the cutting process after the start of the cut but also the cutting feed before the cut. Furthermore, the changes in oscillation conditions include, for example, cases where the oscillation conditions are continuously changed, and cases where the oscillation action is stopped midway even when the oscillation amplitude is zero.

[0030] More specifically, the oscillation command generation unit 13 of this embodiment changes at least one of the oscillation amplitude and oscillation frequency based on the machining position, the elapsed time since the start of the cutting feed, or the amount of movement in the machining direction. For example, the change of oscillation conditions can begin immediately after a predetermined machining position, a predetermined elapsed time since the start of the cutting feed, or a predetermined amount of movement in the machining direction is reached, or the change of oscillation conditions can begin after a predetermined time has elapsed. Alternatively, the oscillation conditions can be changed in accordance with each change in the machining position, the elapsed time since the start of the cutting feed, or the amount of movement in the machining direction.

[0031] Alternatively, the oscillation command generation unit 13 of this embodiment can change at least one of the oscillation amplitude and oscillation frequency based on at least one of the spindle load, spindle speed, spindle speed deviation, spindle speed variation, feed axis load, feed axis speed, feed axis speed deviation, and feed axis speed variation. For example, the change of oscillation conditions can begin immediately after a predetermined spindle load, predetermined spindle speed, predetermined spindle speed deviation, predetermined spindle speed variation, predetermined feed axis load, predetermined feed axis speed, predetermined feed axis speed deviation, and predetermined feed axis speed variation are achieved, or the change of oscillation conditions can begin after a predetermined time has elapsed. In addition, the oscillation conditions can be changed in accordance with each change in the spindle load, spindle speed, spindle speed deviation, spindle speed variation, feed axis load, feed axis speed, feed axis speed deviation, and feed axis speed variation.

[0032] As a specific method for changing the oscillation conditions, changes can be made based on a time constant, or changes can be made by switching at specific oscillation phases, for example. Specific oscillation phases could include 0° and 90°. Furthermore, the oscillation command generation unit 13 can change at least one of the oscillation amplitude and oscillation frequency to a smaller value, or conversely, to a larger value. Various methods exist for changing the oscillation conditions during the processing performed by the oscillation command generation unit 13; therefore, specific examples will be given in detail later.

[0033] Adder 14 generates an overlap command. Specifically, adder 14 overlaps the accumulated value of the position deviation calculated by accumulator 12 with the swing command generated by swing command generation unit 13, thereby generating an overlap command. Adder 14 may also be configured to add the swing command generated by swing command generation unit 13 to the position command.

[0034] The learning controller 15 calculates a correction amount for the overlapping command based on the position deviation, and adds the calculated correction amount to the overlapping command via the adder 16, thereby correcting the overlapping command. The learning controller 15 has a memory that stores the deviation between the ideal position and the actual position of the motor 30, which can be defined for a certain cycle, in the memory. It reads the deviation stored in the memory for each cycle, thereby calculating a correction amount to bring the deviation close to zero. In this embodiment, the overlapping command, which includes an oscillation command, is prone to position deviation. The correction by the learning controller 15 improves the tracking accuracy for periodic oscillation commands.

[0035] The position and speed control unit 17 generates a torque command for driving the motor 30 of the feed axis based on the overlap command, and controls the motor 30 according to the generated torque command. As a result, machining is performed while the tool and the workpiece are oscillating relative to each other.

[0036] Next, specific examples will be given and referenced. Figures 2-7 The changes to the swing conditions during the addition process performed by the swing command generation unit 13 are explained in detail.

[0037] exist Figures 2-7 The embodiments shown illustrate examples of changing the oscillation amplitude (including oscillation amplitude multiples) or oscillation frequency (including oscillation frequency multiples), but the oscillation frequency can also be changed instead of the oscillation amplitude, or the oscillation amplitude can be changed instead of the oscillation frequency. Alternatively, both the oscillation amplitude and the oscillation frequency can be changed. Furthermore, in each embodiment, the oscillation conditions can be changed according to a time constant or switched in stages.

[0038] Furthermore, in the embodiments described later, as long as the chips can be shredded, the oscillation amplitude can be reduced to a level that does not produce air cutting (air vibration) and does not retract. Alternatively, the oscillation action can be stopped during processing (i.e., the oscillation amplitude is reduced to zero), and chip shredding based on the chip breaker groove can be switched. In practical applications, the oscillation amplitude or oscillation frequency is reduced as processing progresses, but it is not limited to this; the oscillation amplitude or oscillation frequency can also be increased.

[0039] Figure 2 This illustrates the change in oscillation conditions during hole drilling in Example 1. Example 1 is an example of applying this embodiment to hole drilling, where the oscillation amplitude is changed based on the drilling position. The drilling position is the Z-axis position, i.e., the amount of movement starting from the Z-axis reference position, point R. However, instead of the drilling position, the oscillation amplitude can also be changed based on the elapsed time since the start of the cutting feed and the amount of movement in the drilling direction.

[0040] like Figure 2 As shown in Embodiment 1, during the movement of the Z-axis position from point R towards the bottom of the hole, and during the movement from point R away from a predetermined distance, the oscillation amplitude is changed to a smaller value. This allows for the suppression of machine tool vibration while simultaneously breaking up chips. Furthermore, by changing the oscillation amplitude according to a time constant, impacts are prevented due to variations in oscillation amplitude during machining. Therefore, the oscillation amplitude changes slowly and gradually, reducing impacts caused by abrupt changes in oscillation amplitude and improving machining accuracy.

[0041] Furthermore, as a variation of this embodiment, the oscillation conditions can be changed at specific oscillation phases. Specifically, for example, the oscillation amplitude can be switched at 0° or 90° oscillation phases to change the oscillation. This reduces the impact caused by abrupt changes in oscillation amplitude and improves machining accuracy.

[0042] Figure 3This illustrates the change in oscillation conditions during the hole-making process in Example 2. Example 2 is an example of applying this embodiment to hole-making, specifically an example of changing the oscillation amplitude based on spindle load. Figure 3 As shown, if machining begins, the spindle load increases sharply to a peak, then gradually decreases and converges to a predetermined value. Since the machining process is considered to have entered a stable state at the point where the spindle load converges to the predetermined value, the oscillation amplitude is changed according to a time constant at that point. Thus, the same effect as in Example 1 can be obtained. Furthermore, as in Example 2, the oscillation amplitude can be temporarily changed to a small value, and then changed to a large value after a predetermined time.

[0043] As a variation of this embodiment, in addition to spindle load, the oscillation conditions can also be changed based on spindle speed, spindle speed deviation, or spindle speed variation. Alternatively, the oscillation conditions can be configured to be changed based on at least one of the feed axis load, speed, speed deviation, and speed variation.

[0044] Figure 4 This illustrates the change in oscillation conditions during the hole-making process in Example 3. Example 3 is an example of applying this embodiment to hole-making, specifically an example of changing the oscillation amplitude based on the spindle speed. Figure 4 As shown, if machining begins, the spindle speed temporarily decreases and then gradually increases until it converges to a predetermined value. Since the machining process is considered to have entered a stable state at the point where the spindle speed converges to the predetermined value, the oscillation amplitude is adjusted according to a time constant at that point. Thus, the same effect as in Examples 1 and 2 can be obtained.

[0045] Figure 5 This illustrates the change in oscillation conditions during the hole-making process in Example 4. Example 4 is an example of applying this embodiment to hole-making, specifically an example of changing the oscillation amplitude based on spindle speed deviation. Figure 5 As shown, once machining begins, the spindle speed deviation, after fluctuating and becoming unstable, converges to its original predetermined value. Since the machining process is considered to have entered a stable state at the point where the spindle speed deviation converges to the predetermined value, the oscillation amplitude is adjusted according to a time constant at that point. Thus, the same effect as in Examples 1-3 can be obtained.

[0046] Figure 6 This illustrates the change in oscillation conditions during turning in Example 5. Example 5 is an example of applying this embodiment to turning, where the oscillation amplitude is changed based on the amount of movement in the machining direction. Figure 6As shown, when machining begins, the amount of movement in the machining direction increases over time. At the point when machining has reached a stable state after a predetermined time has elapsed since the start of machining, the oscillation amplitude is switched to a smaller value. This allows for the suppression of machine tool vibration while simultaneously crushing chips.

[0047] Figure 7 This illustrates the change in oscillation conditions during turning in Example 6. Example 6 is an example of applying this embodiment to turning, specifically an example of changing the oscillation frequency based on the amount of movement in the machining direction. Figure 7 As shown, when machining begins, the amount of movement in the machining direction increases over time. At the point where machining has reached a stable state after a predetermined time from the start, the oscillation frequency is changed according to a time constant. This allows for the suppression of machine tool vibration while simultaneously breaking up chips. Furthermore, it reduces the impact caused by abrupt changes in oscillation frequency, thereby improving machining accuracy.

[0048] According to this embodiment, the following effects are achieved.

[0049] In this embodiment, the tool and workpiece are provided with: a swing command generation unit 13, which calculates the swing amplitude and swing frequency according to the processing conditions and generates a swing command; and a position speed control unit 17, which generates an overlap command by overlapping the swing command generated by the swing command generation unit 13 with the position command or position deviation, so that the tool and workpiece swing relative to each other, and the swing command generation unit 13 changes at least one of the swing amplitude and swing frequency during processing.

[0050] Currently, due to the large load at the start of cutting, the oscillation amplitude is set large to reliably crush the chips, resulting in machine tool vibration. According to this structure, by changing the oscillation amplitude and other parameters to appropriate values ​​during machining, machine tool vibration can be suppressed. Therefore, this structure enables chip crushing while suppressing machine tool vibration, thus improving machining accuracy.

[0051] In addition, in this embodiment, the oscillation command generation unit 13 changes at least one of the oscillation amplitude and oscillation frequency based on the machining position, the elapsed time since the start of the cutting feed, or the amount of movement in the machining direction.

[0052] According to this structure, by changing the oscillation conditions based on the machining position, the elapsed time since the start of the cutting feed, or the amount of movement in the machining direction, the oscillation conditions can be changed after the machining has stabilized, and the oscillation conditions can be changed at a more appropriate time.

[0053] In addition, in this embodiment, the swing command generation unit 13 changes at least one of the swing amplitude and swing frequency based on at least one of the spindle load, spindle speed, spindle speed deviation, spindle speed variation, feed axis load, feed axis speed, feed axis speed deviation, and feed axis speed variation.

[0054] According to this structure, by changing the oscillation conditions based on at least one of spindle load, spindle speed, spindle speed deviation, spindle speed variation, feed axis load, feed axis speed, feed axis speed deviation, and feed axis speed variation, the oscillation conditions can be changed after machining stabilizes, and the oscillation conditions can be changed at a more appropriate timing.

[0055] Furthermore, in this embodiment, the swing command generation unit 13 is configured to change at least one of the swing amplitude and swing frequency according to a time constant.

[0056] According to this structure, by changing the oscillation conditions according to the time constant, the impact caused by the change in oscillation conditions can be reduced, thereby improving the machining accuracy.

[0057] In addition, in this embodiment, the swing command generation unit 13 is configured to change at least one of the swing amplitude and swing frequency at a specific swing phase.

[0058] According to this structure, the swing conditions can be changed at a specific swing phase, such as at a swing phase of 0° or 90°, thereby reducing the impact caused by the change in swing conditions and improving machining accuracy.

[0059] In addition, in this embodiment, the swing command generation unit 13 is configured to change at least one of the swing amplitude and swing frequency to a smaller value.

[0060] Currently, due to the large load at the start of cutting, the oscillation amplitude is set large to reliably break the chips, resulting in machine tool vibration. However, according to this structure, by changing the oscillation amplitude and other values ​​to smaller values ​​during machining, the generation of machine tool vibration can be suppressed more reliably. Therefore, it is possible to break the chips while more reliably suppressing machine tool vibration, thereby improving machining accuracy.

[0061] In addition, in this embodiment, a learning controller 15 is also provided, which calculates the correction amount of the overlap command based on the position deviation and adds the calculated correction amount to the overlap command to correct the overlap command.

[0062] According to this structure, the overlapping command in this embodiment is prone to positional deviation because it includes a swing command. By correcting the overlapping command, the tracking accuracy for periodic swing commands can be improved.

[0063] This invention is not limited to the above-described embodiments; variations and improvements within the scope of achieving the objectives of this invention are also included in this invention.

[0064] Explanation of reference numerals in the attached figures

[0065] 1. Machine tool control device

[0066] 10 Servo Control Device

[0067] 11 Adders

[0068] 12 accumulators

[0069] 13. Swing Command Generation Unit

[0070] 14 Adders

[0071] 15. Learning Controller (Learning Control Unit)

[0072] 16. Adder (Learning Control Unit)

[0073] 17. Position and speed control unit (control unit)

[0074] 30 Electric motor.

Claims

1. A control device for a machine tool, wherein the machine tool performs machining by oscillating the tool relative to the workpiece, characterized in that, The control device includes: The oscillation command generation unit calculates the oscillation amplitude and oscillation frequency based on the processing conditions and generates oscillation commands; and The control unit, based on an overlap command generated by the oscillation command generation unit by overlapping a position command or position deviation with an overlap command generated by the oscillation command generation unit, causes the tool to oscillate relative to the workpiece. The oscillation command generation unit, based on the machining position, the elapsed time since the start of the cutting feed, or the amount of movement in the machining direction, determines that the machining has entered a stable state, and then changes at least one of the oscillation amplitude and the oscillation frequency during the machining process.

2. The machine tool control device according to claim 1, characterized in that, The swing command generation unit changes at least one of the swing amplitude and the swing frequency according to a time constant.

3. The machine tool control device according to claim 1, characterized in that, The swing command generation unit changes at least one of the swing amplitude and the swing frequency at a specific swing phase.

4. The machine tool control device according to claim 1, characterized in that, The swing command generation unit changes at least one of the swing amplitude and the swing frequency to a smaller value.

5. The machine tool control device according to claim 2, characterized in that, The swing command generation unit changes at least one of the swing amplitude and the swing frequency to a smaller value.

6. The machine tool control device according to claim 3, characterized in that, The swing command generation unit changes at least one of the swing amplitude and the swing frequency to a smaller value.

7. The machine tool control device according to any one of claims 1 to 6, characterized in that, The control device further includes a learning control unit, which calculates a correction amount for the overlapping command based on the position deviation, and corrects the overlapping command by adding the calculated correction amount to the overlapping command.

8. A control device for a machine tool, wherein the machine tool performs machining by oscillating the tool relative to the workpiece, characterized in that, The control device includes: The oscillation command generation unit calculates the oscillation amplitude and oscillation frequency based on the processing conditions and generates oscillation commands; and The control unit, based on an overlap command generated by the oscillation command generation unit by overlapping a position command or position deviation with an overlap command generated by the oscillation command generation unit, causes the tool to oscillate relative to the workpiece. The oscillation command generation unit, based on at least one of spindle load, spindle speed, spindle speed deviation, spindle speed variation, feed axis load, feed axis speed, feed axis speed deviation, and feed axis speed variation, determines that the machining has entered a stable state, and then changes at least one of the oscillation amplitude and the oscillation frequency during the machining process.

9. The machine tool control device according to claim 8, characterized in that, The swing command generation unit changes at least one of the swing amplitude and the swing frequency according to a time constant.

10. The machine tool control device according to claim 8, characterized in that, The swing command generation unit changes at least one of the swing amplitude and the swing frequency at a specific swing phase.

11. The machine tool control device according to claim 8, characterized in that, The swing command generation unit changes at least one of the swing amplitude and the swing frequency to a smaller value.

12. The machine tool control device according to claim 9, characterized in that, The swing command generation unit changes at least one of the swing amplitude and the swing frequency to a smaller value.

13. The machine tool control device according to claim 10, characterized in that, The swing command generation unit changes at least one of the swing amplitude and the swing frequency to a smaller value.

14. The control device for a machine tool according to any one of claims 8 to 13, characterized in that, The control device further includes a learning control unit, which calculates a correction amount for the overlapping command based on the position deviation, and corrects the overlapping command by adding the calculated correction amount to the overlapping command.

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