JP2714851B2 - EDM control device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric discharge machining control device, and more particularly, to an optimal control for keeping a machining state always optimal.

[Prior Art] FIG. 11 shows, for example, the document “Mechanical Technology” (June 1980, Vo
l28, No. 7, pp. 25-27) is a block diagram of the conventional electric discharge machining control device shown in FIG. In FIG. 11,
(1) is a target value setter for setting a target value R in the electric discharge machining state, and (2) is a target value R set by the target value setter (1).
EDM process (EDM event including an electric discharge phenomenon) controlled according to (3) is an electrode control for controlling the EDM process (2) by setting a machining gap between a machining electrode and a workpiece as an operation amount Xa. System, (4) is EDM process (2)
(5) is a target value R set in the target value setting unit (1) and a state detector (4). This is a comparator that outputs a deviation E from the detected state quantity Y.

FIG. 12 is a block diagram of an electric discharge machining control device different from the above-mentioned conventional example disclosed in, for example, Japanese Patent Publication No. 62-54602. In FIG. 12, (1), (2),
(4) and (5) are the same as the conventional example shown in FIG. (6) is a power supply control system for controlling the state of the electric discharge machining process (2) with the machining power supply pulse condition applied to the machining gap as the operation amount Xb.

Next, the operation of the conventional electric discharge machining control device configured as described above will be described.

In the electric discharge machining control device shown in FIG. 11, a target value R in a desirable state of the electric discharge machining process (2) is set in the target value setter (1) and sent out. On the other hand, the state quantity Y of the electric discharge machining process (2) is detected by the state detector (4).

The electrode control system (3) operates the manipulated variable Xa so that the detected state quantity Y matches the target value R, and controls the state of the electric discharge machining process (2) based on the manipulated variable Xa. That is, the electrode control system (3) realizes the operation amount Xa of the machining gap such that the deviation E between the target value R and the detected state amount Y becomes zero, and the state of the electric discharge machining process (2) is always desirable. I am trying to become.

FIG. 13 is a waveform diagram of the inter-electrode voltage Vg detected by the state detector (4) as the state quantity Y during machining. In FIG. 13, Va is the arc voltage, and t _d is the no-load time. As shown in FIG. 13, unloading time t _d is varied irregularly affected by the minute unevenness of discharge craters generated on the amount and the processing surface of the processing debris floating in the machining gap.

Further, FIG. 14 is a diagram showing an example of a power spectrum of the unloading time t _d during the machining. As shown in FIG.
The dynamic characteristic of the electric discharge machining process (2) has a frequency band of several hundred Hz. On the other hand, the dynamic characteristic of the electrode control system (3) that operates the machining gap as the operation amount Xa is determined by the servo system, and its response is about several tens Hz.

On the other hand, in the electric discharge machining control device shown in FIG.
The power supply control system (6) sets the machining power supply pulse condition as the manipulated variable Xb, for example, operates the pulse interval or the electric discharge machining current so that the state of the electric discharge machining process (2), that is, the electric discharge machining state is always in a desirable state. I have.

Manipulating the machining power supply pulse conditions corresponds to adjusting the amount of machining waste generated by machining.

Therefore, in a range where the variation of the electric discharge machining state is relatively small, the electric discharge machining state can be controlled more finely and at a higher speed as compared with the electric discharge machining control device shown in FIG.

[Problems to be Solved by the Invention] In the conventional electric discharge machining control device having the electrode control system (3) shown in FIG. 11, the response of the electrode control system (3) is about several tens Hz. In addition, there is a problem that the electric discharge machining process (2) having a frequency band of several hundred Hz cannot be sufficiently controlled.

The conventional electric discharge machining control device having the power supply control system (6) shown in FIG. 12 has high responsiveness, but generally has a control range smaller than that of the electrode control system (3) and an appropriate power supply. However, there is a problem that large fluctuations in the electric discharge machining process (2) cannot be sufficiently compensated.

The present invention has been made to solve such a problem, and a plurality of driving mechanisms are combined in the same axial direction to appropriately operate the respective driving mechanisms.

Alternatively, an object of the present invention is to provide an electric discharge machining control device capable of appropriately operating an electrode control system and a power supply control system, always compensating for variations in an electric discharge machining process, and improving electric discharge machining efficiency.

[Means for Solving the Problems] A first electric discharge machining control device according to the present invention includes a state quantity during machining in which a control target value of an electric discharge machining state set in a target value setting device is detected by a state detector. Of the machining power supply pulse condition in the power supply control system so that the deviation of the power supply becomes zero. At the same time, the deviation between the command value of the machining power supply pulse condition set by the command value setting device and the operation amount of the machining power supply pulse condition operated by the power supply control system is integrated by a deviation integrator, and based on this integrated value, Operate the machining gap with the electrode control system,
Compensates for fluctuations in the EDM state.

Further, the second electric discharge machining control device according to the present invention includes a plurality of electric discharge machining control devices, each of which has at least one of a frequency characteristic and a positioning accuracy different in order to move at least one of the machining electrode and the workpiece in the same axial direction. By combining these drive mechanisms and operating the respective drive mechanisms appropriately, variations in the electric discharge machining state are compensated.

[Operation] In the present invention, with respect to the variation of the electric discharge machining state,
Variations that cannot be compensated for even when the power supply control system operates the machining power supply pulse conditions are obtained by the deviation integrator, and the variations are controlled by the electrode control system, so that variations in the electric discharge machining state are appropriately compensated.

Further, the second electric discharge machining control device according to the present invention combines a plurality of drive mechanisms in the same axial direction, and operates a drive mechanism having a high frequency characteristic among the drive mechanisms instead of the above-described power supply control system, A variation that cannot be compensated for by the drive mechanism is obtained by the deviation integrator, and the variation is controlled by the remaining drive mechanisms to appropriately compensate for the variation in the electric discharge machining state.

FIG. 1 is a block diagram of an electric discharge machining control device according to one embodiment of the present invention. In FIG. 1, (1) to (1)
(6) is exactly the same as the conventional example shown in FIGS. 11 and 12, and the power supply control system (6) is set in the target value setter (1) as in the conventional example shown in FIG. The deviation E between the control target value R of the detected electric discharge machining state and the state quantity of the electric discharge machining process (2) detected by the state detector (4) is compared with the state comparator (5).
To control the control amount Xb of the electric discharge machining power supply pulse condition.

In FIG. 1, (7) is a command value setting device for setting a command value Rv of the machining power supply pulse condition, and (8) is a command value Rv output from the command value setting device (7) and a power control system ( 6) Deviation of machining power supply pulse condition operated by 6) from control amount Xb
A comparator that outputs Ev, and (9) is a deviation integrator that integrates the deviation Ev output by the comparator (8). Deviation integrator (9)
Is output to the electrode control system (3).

By the way, the power spectrum of each system in the electric discharge machining control device configured as described above is as shown in FIG. In FIG. 2, (2f) shows the frequency characteristics of the electric discharge machining process (2), (3f) shows the frequency characteristics of the electrode control system (3), and (6f) shows the frequency characteristics of the power supply control system (6). As shown in FIG. 2, the frequency characteristic (2f) of the electric discharge machining process (2) has a frequency band from several tens Hz to several hundred Hz, and the frequency characteristic (3f) of the electrode control system (3) is several 10Hz
And the frequency band (6f) of the power supply control system (6) has a frequency band of several hundred Hz.

Therefore, the frequency characteristic (6f) of the power supply control system (6) is several hundreds.
Since it has a frequency band up to Hz, it is more advantageous than the electrode control system (3) for compensating for variations in the electric discharge machining process.

Therefore, the power supply control system (6) is operated so that the deviation E between the target value R set by the target value setter (1) and the state quantity Y detected by the state detector (4) becomes zero, and machining is performed. By manipulating the manipulated variable Xb of the power pulse condition, the fluctuation of the electric discharge machining state is compensated.

On the other hand, if it is attempted to compensate for the variation of the electric discharge machining state only by the power supply control system (6), the distance of the machining gap increases with machining, or the amount of machining waste generated with machining sharply increases. For example, the operation amount Xb of the processing power supply pulse condition continuously takes the maximum value or the minimum value that can be operated by the power supply control system (6).

For this reason, although a small change in the electric discharge machining state can be compensated, a sufficient compensation effect cannot be obtained for a large change.

Therefore, a deviation Ev between the command value Rv of the machining power pulse condition set by the command value setting device (7) and the manipulated variable Xb of the machining power pulse condition operated by the power control system (6) is obtained. Is integrated by a deviation integrator (9), and the integrated value M is output to an electrode control system (3). The electrode control system (3) is a manipulated variable for varying the distance between the machining electrode and the workpiece from the integral value M.
By operating Xa, large fluctuations in the electric discharge machining state that cannot be completely compensated by the power supply control system (6) are promptly compensated.

The power supply control system (6) and the electrode control system (3) thus configured cooperate with each other to compensate for the variation in the electric discharge machining state, so that the electric discharge machining state varies in a frequency band of several hundred Hz. In this case, or even in the case of large fluctuation, a stable electric discharge machining state can be always maintained.

In the present embodiment, the case where the electrode control system (3) directly manipulates the manipulated variable Xa by receiving the integral value M from the deviation integrator (9) has been described. However, as shown in FIG. The value M may be sent to the electrode control system (3) after being filtered by the signal processing filter (10).

The signal processing filter (10) is a low-pass filter having a frequency characteristic (10f) as shown in FIG. 4 in consideration of the frequency characteristic (3f) of the electrode control system (3) shown in FIG. The control system (3) performs an appropriate operation.

This low-pass filter is a linear filter FI
An R digital filter, an IIR digital filter, a nonlinear ε-separated digital filter, or an analog filter using an operational amplifier or the like may be used.

In addition, the electrode control system (3) has a plurality of drive mechanisms (3a), (3
b), ..., (3n), the filters (10a1), (10a2), ... corresponding to the driving mechanisms (3a), (3b), ..., (3n) as shown in FIG. , (10an), an operation amount suitable for each of the driving mechanisms (3a) to (3n) is obtained.

In this case, the filters (10a1) to (10a2) are frequency characteristics (3af) to (3af) of the driving mechanisms (3a) to (3n) shown in FIG.
In order to take into account nf) and to avoid mutual interference, one having frequency characteristics (10f1) to (10fn) as shown in FIG. 7 is used.

Further, the frequency characteristic of any one of the plurality of driving mechanisms (3a) to (3n) is higher than the frequency characteristic of the electrode control system in the conventional electric discharge machine, and substantially equal to the frequency characteristic of the power supply control system described above. When they are close to each other, the same operation is achieved even if the power supply control system (6) in the configuration of FIG.

Next, FIG. 8 is a block diagram of an electric discharge machining control device according to another embodiment of the present invention. In FIG. 8,
(1) to (5) and (7) to (9) are exactly the same as the embodiment shown in FIG.

By the way, an electric discharge machine is to machine a workpiece into a desired shape by relatively moving a machining electrode and a workpiece. At least one of the machining electrode and the workpiece is the same. In some cases, the drive system is configured by a drive system in which a plurality of drive mechanisms that move in the axial direction are combined.

In this case, at least one of the frequency characteristics and the positioning accuracy may be different in each drive mechanism. For example, the first drive mechanism mainly has a small drive range but has a high responsiveness in order to quickly compensate for fluctuations in the electric discharge machining state, and the second drive mechanism mainly has the machining that proceeds with the progress of machining. A mechanism having a low response but a large drive range for electrode feeding, a mechanism having a large drive range with a coarse positioning accuracy for the first drive mechanism, and a mechanism having a small drive range for the second drive mechanism Is a mechanism having a high positioning accuracy.

In such a case, the electric discharge machining control device shown in FIG. 1 may not be able to compensate for variations in the electric discharge machining state.

Therefore, in this embodiment, at least one of the frequency characteristic and the positioning accuracy is different, and the electric discharge machining control device has an electrode control system configured by a driving system in which a plurality of driving mechanisms for moving in the same axial direction are combined. To compensate for fluctuations in the state of electrical discharge machining due to

Therefore, the deviation integrator (9) uses the deviation between the control target value set by the target value setter (1) and the state quantity detected by the state detector (4) to form an electrode control system (3). Gap that is operated when it is added as a control command for the drive mechanism (3a) of the above, and the command value that is commanded by the command value setter (7)
The deviation Ev from Rv is integrated, and the integrated value M is output as a control command for the other drive mechanism (3b).

With this configuration, the electrode control system (3) moves the machining electrode or the workpiece in the same axial direction.
Even in the case of a drive system combining a plurality of drive mechanisms different in at least one of frequency characteristics and positioning accuracy, the signal processing filter (10) is configured in consideration of the frequency characteristics and control range of each drive mechanism. By doing so, the same operation as in the above embodiment can be achieved.

In this embodiment, the integral value M is directly output to the drive mechanism (3b). However, as shown in FIG.
May be sent to the drive mechanism (3b) after being filtered by the signal processing filter (10).

In the embodiment shown in FIG. 9, two drive mechanisms (3
Although the electrode control system (3) composed of (a) and (3b) has been described, as shown in FIG.
Each of the driving mechanisms (3b) to (3) can be used even in an electric discharge machining control device having an electrode control system (3) composed of (a) to (3n).
An operation amount suitable for n) can be obtained.

[Effects of the Invention] As described above, the present invention compensates for fluctuations in the state of electric discharge machining by manipulating machining power supply pulse conditions in a power supply control system, and also uses a deviation integrator to compensate for fluctuations that cannot be completely compensated for in a power supply control system. In order to move the machining electrode or the workpiece in the same axis direction, a combination of a plurality of drive mechanisms that differ in at least one of the frequency characteristics and the positioning accuracy is used. Since each drive mechanism is operated with the same configuration as above to compensate for fluctuations in the electric discharge machining state, a stable electric discharge machining state can be always maintained, and the electric discharge machining efficiency can be significantly improved. It has the effect that can be.

[Brief description of the drawings]

FIG. 1 is a block diagram of an electric discharge machining control device according to an embodiment of the present invention, FIG. 2 is a frequency characteristic diagram of each part of the electric discharge machining control device shown in FIG. 1, FIG. 3, FIG. Fig. 8, ninth
FIG. 10 and FIG. 10 are block diagrams of an electric discharge machining control device according to another embodiment of the present invention, FIG. 4 is a frequency characteristic diagram of a signal processing filter of the electric discharge machining control device shown in FIG. 3, and FIG. FIG. 7 is a frequency characteristic diagram of an electrode control system of the electric discharge machining control device shown in FIG. 5, FIG. 7 is a frequency characteristic diagram of a signal processing filter of the electric discharge machining control device shown in FIG. 5, FIG. FIG. 13 is a block diagram of a conventional electric discharge machining control device, FIG. 13 is a waveform diagram of a gap voltage of the conventional electric discharge machining control device shown in FIG. 11, and FIG.
FIG. 14 is a frequency characteristic diagram of the conventional electric discharge machining control device shown in FIG. In each figure, 1 is a target value setter, 2 is an electric discharge machining process, 3
Is an electrode control system, 4 is a state detector, 6 is a power control system, 7 is a command value setting device, 9 is a deviation integrator, and 10 is a signal processing filter. Note that the same reference numerals in the drawings indicate the same or corresponding parts.

Claims (2)

(57) [Claims] A target value setting device for setting a control target value in an electric discharge machining state, and a command value setting for setting a command value of a machining power supply pulse condition applied to a machining gap between a machining electrode and a workpiece. A state detector for detecting a state quantity of electric discharge machining controlled according to the control target value and the machining power supply pulse condition; and a machining power supply pulse condition based on a deviation between the control target value and the state quantity. A power control system for controlling an electric discharge machining state, a deviation integrator for integrating a deviation between a command value of the machining power pulse condition and an operation amount output by the power control system, and a machining gap based on an integral value of the deviation integrator. And an electrode control system for controlling an electric discharge machining state with the operation amount as an operation amount. 2. A target value setter for setting a control target value of an electric discharge machining state, a state detector for detecting a state quantity of electric discharge machining controlled according to the control target value, A command value setting device for setting a command value of a machining gap between;
At least one of the frequency characteristics and the positioning accuracy is different, and at least one of the processing electrode and the workpiece is an electrode control system configured by a driving system in which a plurality of driving mechanisms for moving in the same axial direction are combined. Integrating the deviation between the command value and the machining gap operated when adding a deviation between the control target value and the state quantity as a control command for at least one drive system constituting the electrode control system; An electric discharge machining control device, comprising: a deviation integrator that uses an integral value as a control command for a drive system other than the drive system.