Machine tool control device

Abstract

Provided is a control device for a machine tool that can suitably shred chips in a state without good conformability. A control device for a machine tool which oscillates a tool and a workpiece relative to each other while machining comprises: an oscillation amplitude calculation unit that calculates an oscillation amplitude on the basis of the feed speed of the tool and an oscillation condition for oscillating the workpiece and the tool relative to each other; a minimum value setting unit that sets a minimum value for the oscillation amplitude; a comparison unit that compares the oscillation amplitude calculated value calculated by the oscillation amplitude calculation unit and the oscillation amplitude minimum value set by the minimum value setting unit; an oscillation command generation unit that generates an oscillation command on the basis of the oscillation condition and the value of the oscillation amplitude obtained from the comparison results of the comparison unit; and a position / speed control unit that oscillates the workpiece and the tool relative to each other on the basis of a superimposition command obtained by superimposing the oscillation command over a position command.

Description

[Technical field]

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

[0002] Conventionally, oscillating cutting has been applied as a measure against chips in drilling, turning, etc. Conventional numerical control devices realize oscillating cutting by superimposing an oscillating command on a position command.

[0003] There is a temporary state where the tool cannot follow the change in the command immediately after applying the swing command or immediately after the feed rate is changed. In this state, the swing amplitude required to chop the chips may not be obtained at the actual position of the tool. In this case, there is a problem that the chips cannot be chopped appropriately. In order to continue chopping the chips, a technique has been proposed that corrects the frequency or amplitude so that the tool path overlaps even if a tracking error occurs (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2019-40252 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, the oscillation amplitude is determined by multiplying the command by the oscillation amplitude magnification factor according to the feed rate. Therefore, if the oscillation amplitude magnification factor is increased in advance in consideration of the delay in following the command, the oscillation amplitude will be excessive in the steady state, which will have an impact on the tool and the roughness of the machined surface. Therefore, it is desired to appropriately shred the chips in a state where the follow-up ability is poor, such as immediately after the start or end of processing. [Means for solving the problem]

[0006] According to one aspect of the present disclosure, a control device for a machine tool that performs processing while swinging a tool and a workpiece relative to one another includes a swing amplitude calculation unit that calculates a swing amplitude based on swing conditions for swinging the workpiece and the tool relative to one another and a feed speed of the tool, a minimum value setting unit that sets a minimum value of the swing amplitude, a comparison unit that compares the calculated value of the swing amplitude calculated by the swing amplitude calculation unit with the minimum value of the swing amplitude set by the minimum value setting unit, a swing command generation unit that generates a swing command based on the value of the swing amplitude obtained from the comparison result by the comparison unit and the swing conditions, and a position and speed control unit that swings the workpiece and the tool relative to one another based on a superposition command in which the swing command is superimposed on a position command. Effect of the Invention

[0007] According to the present invention, it is possible to provide a control device for a machine tool that can appropriately chop chips even in a state where tracking ability is poor. [Brief description of the drawings]

[0008] [Figure 1] FIG. 2 is a block diagram showing a configuration of a control device according to the present embodiment. [Diagram 2] 5 is a flowchart showing a process of the control device according to the present embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] An example of an embodiment of the present invention will now be described. FIG. 1 is a block diagram showing the configuration of a control device 1 for a machine tool according to this embodiment. The control device 1 controls a machine tool 2 that performs machining while oscillating a tool and a workpiece relative to one another. The control device 1 oscillates the tool relative to the workpiece so as to generate small chips in order to prevent chips generated by cutting from becoming entangled with the workpiece or the tool.

[0010] The control device 1 may be connected to a higher-level computer (not shown), such as a CNC (Computer Numerical Controller) or a PLC (Programmable Logic Controller).

[0011] As shown in FIG. 1, the control device 1 includes a position command generating unit 11, a first adder 12, an integrator 13, a swing command generating unit 14, a second adder 15, a learning controller 16, a position / speed control unit 17, a swing condition setting unit 18, a swing amplitude calculation unit 19, a minimum value setting unit 20, a comparison unit 21, a processing condition input unit 22, a lower limit value input unit 23, a recommended value calculation unit 24, a memory unit 25, a display control unit 26, and a display unit 27.

[0012] Position command generating unit 11 generates a position command for motor 201 of machine tool 2 based on machining conditions for machining a workpiece with a tool. Here, the machining conditions may be output from a host computer such as a CNC or PLC to position command generating unit 11. The generated position command is input to first adder 12 as shown in FIG. 1.

[0013] The first adder 12 calculates a position deviation. Specifically, the first adder 12 calculates a position deviation that is a difference between a position feedback based on the position detection by the encoder of the motor 201 of the feed axis and a position command.

[0014] The integrator 13 calculates an integrated value of the position deviation. Specifically, the integrator 13 calculates the integrated value of the position deviation by integrating the position deviation calculated by the first adder 12.

[0015] The swing command generating unit 14 generates a swing command. Specifically, the swing command generating unit 14 generates a swing command based on the swing amplitude value and the swing conditions obtained from the comparison result by the comparing unit 21. The swing command generating unit 14 may obtain the swing command from the swing conditions including the swing amplitude magnification and the swing frequency magnification and the machining conditions, or may obtain the swing command from the swing conditions including the swing amplitude and the swing frequency.

[0016] The learning controller 16 calculates a correction amount for the superimposition command based on the superimposition command, and corrects the superimposition command by adding the calculated correction amount to the superimposition command using an adder. This learning controller 16 has a memory, and correlates the oscillation phase and the superimposition command within one oscillation period or multiple oscillation periods and stores them in the memory. The learning controller 16 reads out the superimposition command stored in the memory at a timing when the phase delay of the oscillation operation according to the responsiveness of the motor 201 can be compensated for, and outputs the superimposition command to the adder as a correction amount.

[0017] Position and speed control unit 17 generates a torque command for motor 201 that drives the feed axis based on the superimposed command after adding the correction amount, and controls motor 201 by the generated torque command. This allows machine tool 2 to perform machining while relatively swinging the tool and the workpiece.

[0018] The swing condition setting unit 18 sets swing conditions for swinging the workpiece and the tool relatively. Specifically, the swing condition setting unit 18 sets a swing amplitude or a swing amplitude magnification, and a swing frequency or a swing frequency magnification. The swing conditions including the swing amplitude or the swing amplitude magnification, and the swing frequency or the swing frequency magnification are input to a swing amplitude calculation unit 19.

[0019] The swing amplitude calculation unit 19 calculates the swing amplitude based on the swing conditions set by the swing condition setting unit 18 and the feed rate of the tool.

[0020] The minimum value setting unit 20 sets a minimum value of the oscillation amplitude. Specifically, the minimum value setting unit 20 sets the minimum value of the oscillation amplitude based on CNC parameters, specifications in the machining program, and the like.

[0021] Furthermore, the minimum value setting unit 20 may change the minimum value of the oscillation amplitude according to the machining conditions. Here, the machining conditions include the rotation speed of the workpiece, the feed speed of the tool, the command acceleration, the inertia, the cutting load, the machine rigidity, etc., but it is particularly preferable that the machining conditions are the command acceleration, the inertia, the cutting load, or the machine rigidity.

[0022] For example, when the command acceleration, inertia, cutting load, or machine stiffness changes, the minimum value setting unit 20 changes the minimum value of the oscillation amplitude by multiplying the minimum value of the oscillation amplitude in the state before the change by a magnification (override value). Similarly, when the time or distance from the start of oscillation to the machining point changes, the minimum value setting unit 20 multiplies the minimum value of the oscillation amplitude in the state before the change by a magnification (override value). This allows the control device 1 to reduce tracking delay because the time from the start of oscillation to the machining point becomes longer. Factors that cause the cutting load to fluctuate include, for example, changes in the specifications of the workpiece and the tool.

[0023] Furthermore, the minimum value setting unit 20 may select the minimum value of the oscillation amplitude stored in the storage unit 25 according to the machining conditions. For example, when a plurality of machining conditions are stored in the storage unit 25, the machining conditions may each be provided with a preset value. For example, when the machining condition is a cutting load and it is difficult to estimate the cutting load, the machining condition may be the result of actual machining or air cutting stored in the storage unit 25.

[0024] The comparison unit 21 compares the calculated value of the oscillation amplitude calculated by the oscillation amplitude calculation unit 19 with the minimum value of the oscillation amplitude set by the minimum value setting unit 20. Specifically, the comparison unit 21 determines whether the calculated value of the oscillation amplitude calculated by the oscillation amplitude calculation unit 19 is less than the minimum value of the oscillation amplitude set by the minimum value setting unit 20.

[0025] When the calculated value of the oscillation amplitude is less than the minimum value of the oscillation amplitude, the comparison unit 21 determines the minimum value of the oscillation amplitude as the value of the oscillation amplitude. When the calculated value of the oscillation amplitude is equal to or greater than the minimum value of the oscillation amplitude, the comparison unit 21 determines the calculated value of the oscillation amplitude as the value of the oscillation amplitude.

[0026] The processing condition input unit 22 receives input of processing conditions, for example, through an input operation by a user. The processing condition input unit 22 outputs the input processing conditions to the recommended value calculation unit 24 and the storage unit 25.

[0027] The lower limit input unit 23 receives an input of a minimum value of the oscillation amplitude by, for example, an input operation by a user. The lower limit input unit 23 outputs the input oscillation amplitude to the recommended value calculation unit 24 and the storage unit 25.

[0028] The recommended value calculation unit 24 estimates the minimum value of the oscillation amplitude corresponding to the input machining conditions newly input by the machining condition input unit 22 or the lower limit input unit 23, based on the multiple machining conditions stored in the storage unit 25. In this case, the storage unit 25 stores multiple minimum values ​​of the oscillation amplitude in association with the machining conditions. This allows the recommended value calculation unit 24 to calculate a more accurate estimate based on the multiple data (i.e., the minimum value of the oscillation amplitude and the machining conditions) stored in the storage unit 25.

[0029] The display control unit 26 causes the setting information including the minimum value of the oscillation amplitude and the processing conditions to be displayed on the display unit 27. The display unit 27 is composed of an LCD (Liquid Crystal Display), a CRT (Cathode Ray Tube), etc., and displays various images according to the control of the display control unit 26.

[0030] Furthermore, when setting information is displayed on display unit 27, minimum value setting unit 20 may select and set a desired setting value using the setting information displayed on display unit 27. For example, minimum value setting unit 20 may accept an input or selection from a user regarding the setting information displayed on display unit 27, and set a desired setting value in response to the input or selection from the user.

[0031] FIG. 2 is a flowchart showing the process of the control device 1 according to the present embodiment. In step S1, the swing amplitude calculation unit 19 calculates the swing amplitude based on swing conditions for relatively swinging the workpiece and the tool. In step S2, the minimum value setting unit 20 sets a minimum value of the oscillation amplitude.

[0032] In step S3, the comparison unit 21 compares the calculated value of the oscillation amplitude calculated by the oscillation amplitude calculation unit 19 with the minimum value of the oscillation amplitude set by the minimum value setting unit 20. Specifically, the comparison unit 21 determines whether the calculated value of the oscillation amplitude calculated by the oscillation amplitude calculation unit 19 is less than the minimum value of the oscillation amplitude set by the minimum value setting unit 20. If the calculated value of the oscillation amplitude is less than the minimum value of the oscillation amplitude (YES), the process proceeds to step S4. If the calculated value of the oscillation amplitude is equal to or greater than the minimum value of the oscillation amplitude (NO), the process proceeds to step S5.

[0033] In step S4, the comparison unit 21 determines the minimum value of the oscillation amplitude as the value of the oscillation amplitude. In step S5, the comparison unit 21 determines the calculated value of the oscillation amplitude as the value of the oscillation amplitude.

[0034] In step S6, the swing command generating unit 14 generates a swing command based on the swing amplitude value and the swing conditions obtained from the comparison result by the comparing unit 21. Specifically, the swing command generating unit 14 generates a swing command based on the swing amplitude value and the swing conditions determined in step S4 or step S5.

[0035] In step S7, the learning controller 16 calculates a correction amount for the superimposition command based on the superimposition command, and corrects the superimposition command by adding the calculated correction amount to the superimposition command using an adder. Thereafter, the position and speed control unit 17 generates a torque command for the motor 201 that drives the feed axis based on the superimposition command after the correction amount has been added, and controls the motor 201 using the generated torque command.

[0036] According to this embodiment, the control device 1 includes a swing amplitude calculation unit 19 that calculates a swing amplitude based on the swing conditions for swinging the workpiece and the tool relatively and the feed speed of the tool, a minimum value setting unit 20 that sets a minimum value of the swing amplitude, a comparison unit 21 that compares the calculated value of the swing amplitude calculated by the swing amplitude calculation unit 19 with the minimum value of the swing amplitude set by the minimum value setting unit 20, a swing command generation unit 14 that generates a swing command based on the swing amplitude value and the swing conditions obtained from the comparison result by the comparison unit 21, and a position and speed control unit 17 that swings the workpiece and the tool relatively based on a superposition command in which the swing command is superimposed on a position command.

[0037] This allows the control device 1 to set a lower limit value for the oscillation amplitude, so that chips can be appropriately chopped in a state where tracking is poor, such as immediately after the start or end of processing.

[0038] Furthermore, the minimum value setting unit 20 changes the minimum value of the oscillation amplitude according to the machining conditions for machining the workpiece with the tool, thereby enabling the control device 1 to use an appropriate minimum value of the oscillation amplitude according to the machining conditions.

[0039] The control device 1 further includes a storage unit 25 that stores multiple minimum values ​​of the oscillation amplitude in association with the machining conditions, and the minimum value setting unit 20 selects the minimum value of the oscillation amplitude stored in the storage unit 25 according to the machining conditions. This allows the control device 1 to select an appropriate minimum value of the oscillation amplitude according to multiple machining conditions.

[0040] The control device 1 further includes a recommended value calculation unit 24 that estimates the minimum value of the oscillation amplitude corresponding to the newly input machining conditions based on the machining conditions stored in the storage unit 25. This allows the control device 1 to calculate a more accurate estimate based on a plurality of data (i.e., the minimum value of the oscillation amplitude and the machining conditions) stored in the storage unit 25.

[0041] The control device 1 further includes a display control unit 26 that displays setting information including the minimum value of the oscillation amplitude and the processing conditions on the display unit 27. This allows, for example, an operator who operates the control device 1 to view and check the setting information.

[0042] Furthermore, the minimum value setting unit 20 selects and sets a desired setting value using the setting information displayed on the display unit 27. This allows, for example, an operator operating the control device 1 to set an appropriate minimum value for the oscillation amplitude by viewing and checking the setting information.

[0043] The control device 1 further includes a learning controller 16 that calculates a correction amount for the superimposition command based on the superimposition command and corrects the superimposition command by adding the calculated correction amount to the superimposition command. Generally, the higher the oscillation frequency, the larger the deviation (superimposition command) from the oscillation command. Therefore, the correction by the learning controller 16 can improve the followability to the periodic oscillation command. As a result, the control device 1 can improve the followability to the superimposition command and easily achieve a desired chip length while suppressing deterioration of machining accuracy.

[0044] Although the embodiment of the present invention has been described above, the above control device 1 can be realized by hardware, software, or a combination of these. In addition, the control method performed by the above control device 1 can also be realized by hardware, software, or a combination of these. Here, being realized by software means being realized by a computer reading and executing a program.

[0045] The program can be stored and provided to a computer using various types of non-transitory computer readable media. The non-transitory computer readable media includes various types of tangible storage media. Examples of the non-transitory computer readable media include magnetic recording media (e.g., hard disk drives), magneto-optical recording media (e.g., magneto-optical disks), CD-ROM (Read Only Memory), CD-R, CD-R / W, and semiconductor memory (e.g., mask ROM, PROM (Programmable ROM), EPROM (Erasable PROM), flash ROM, and RAM (random access memory)).

[0046] Furthermore, although the above-described embodiments are preferred embodiments of the present invention, the scope of the present invention is not limited to only the above-described embodiments, and the present invention can be implemented in various modified forms without departing from the gist of the present invention. [Explanation of symbols]

[0047] 1 Control device 2 Machine tools 11 Position command generation section 12 First adder 13. Accumulator 14 Swing command generator 15 Second adder 16 Learning Controller 17 Position and speed control section 18 Oscillation condition setting section 19 Swing amplitude calculation section 20 Minimum value setting section 21 Comparison section 22 Processing condition input section 23 Lower limit input section 24 Recommended value calculation section 25 Memory section 26 Display control section 27 Display section

Claims

1. A control device for a machine tool that performs machining while swinging a tool and a workpiece relative to each other, a swing amplitude calculation unit that calculates a swing amplitude based on swing conditions for relatively swinging the workpiece and the tool and a feed rate of the tool; a minimum value setting unit that sets a minimum value of the oscillation amplitude; a comparison unit that compares the oscillation amplitude calculated by the oscillation amplitude calculation unit with the minimum value of the oscillation amplitude set by the minimum value setting unit; a swing command generating unit that generates a swing command based on the swing amplitude value obtained from the comparison result by the comparing unit and the swing condition; a position and speed control unit that relatively swings the workpiece and the tool based on a superimposed command in which the swing command is superimposed on a position command; A control device comprising:

2. The control device according to claim 1 , wherein the minimum value setting unit changes the minimum value of the oscillation amplitude in accordance with machining conditions for machining the workpiece with the tool.

3. A storage unit that stores a plurality of minimum values ​​of the oscillation amplitude in association with the processing conditions, The control device according to claim 2 , wherein the minimum value setting unit selects the minimum value of the oscillation amplitude stored in the storage unit in accordance with the machining conditions.

4. The control device according to claim 3 , further comprising a recommended value calculation unit that estimates a minimum value of the oscillation amplitude corresponding to a newly input machining condition based on the machining condition stored in the storage unit.

5. The control device according to claim 2 , further comprising a display control unit that causes a display unit to display setting information including the minimum value of the oscillation amplitude and the processing conditions.

6. The control device according to claim 5 , wherein the minimum value setting unit selects and sets a desired setting value using the setting information.

7. 7. The control device according to claim 1, further comprising a learning control unit that calculates a correction amount of the superimposition command based on the superimposition command, and corrects the superimposition command by adding the calculated correction amount to the superimposition command.

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