JPH01103228A - Controller for wire electric discharge machine - Google Patents

Abstract

PURPOSE:To dissolve the abnormal electric discharge state in a short time and increase the electric discharge working speed by detecting the normal or abnormal electric discharge at each electric discharge pulse and immediately turning OFF a switch such as transistor for electric discharge pulses when the abnormal electric discharge is detected. CONSTITUTION:An electric discharge current control circuit 13 applies a pulse voltage into between the electrodes 17 from a working power source 13 according to the clock signals of an oscillator 14, and electric discharge work is carried out. At each electric discharge pulse, the electric discharge voltage is adjusted to the voltage proper for control by a buffer amplifier 6, and compared with an abnormal voltage detection level voltage value in a comparator 7, and when the adjusted value is lower, the abnormal electric discharge is detected by an electric discharge current off detecting logic 9, and an electric discharge current off prohibiting pulse 8 is applied, and the electric discharge current between the electrodes 17 is cut off, and then a standard clock is generated from the oscillator 14. When the number of pulses increases over the value of an electric discharge current off pulse setting device 12, electric discharge work is restarted. Thus, the electric discharge work speed can be improved.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is directed to the control of a wire electrical discharge machine that generates electrical discharge between a traveling wire electrode and a workpiece, and processes the workpiece using discharge energy. Regarding equipment.

[Conventional technology]

Conventionally, the current state of wire electric discharge machines is to machine a workpiece using a portion in which a wire electrode runs vertically, in other words, in an up-down direction. The wire electrode is guided by rollers fixed to the main body of the wire electric discharge machine and supplied to a wire head having a wire guide.

On the other hand, the table on which the workpiece is attached moves in the X and Y directions according to the machining status of the workpiece according to commands from the NC device, and moves in servo mode between it and the wire electrode supplied to the wire head. Processing progresses by repeating the function. In other words, the wire head not only moves relatively in the machining direction during wire electrical discharge machining, but also when electrical discharge machining becomes unstable due to conditions such as machining debris, the wire head moves back to the machining trajectory for an instant to eliminate short circuits. Electric discharge machining is performed by moving backward along the line, then moving forward again. Then, in response to commands from the NC device, the workpiece moves in the horizontal direction, that is, in the Processed.

Conventionally, Japanese Patent Application Laid-Open No. 54-156296 discloses a method for controlling a wire-cut electrical discharge machining apparatus. This control method for a wire-cut electrical discharge machining apparatus includes a switching element in a capacitor charging circuit, and utilizes charging and discharging of the capacitor to control a current-carrying machining gap formed between a wire electrode and a workpiece. Electrical cutting is performed by passing a discharge current intermittently, and the charging current of the capacitor is controlled according to the state of the current-carrying gap, and the state of the current-carrying gap is short-circuited or continuous arcing. Even if it is detected that the state is close to that, the current flowing through the energized machining gap is not reduced for a predetermined time, and if the state of the energized machining gap is not restored within the predetermined time, This reduces the current flowing through the energized machining gap.

Moreover, as a wire electrode disconnection prevention circuit for wire electric discharge machining that prevents wire electrode disconnection in wire electric discharge machining, Japanese Patent Laid-Open Nos. 61-288930 and 61-2
It is disclosed in Japanese Patent No. 88931. The wire electrode disconnection prevention circuit for wire electrical discharge machining prevents fluctuations in the machining current flowing through at least one of feeders provided above and below the workpiece in order to supply the machining current to the wire electrode. A concentrated discharge detection circuit detects whether or not a concentrated discharge state is present, and a machining average current detects whether the machining average current is equal to or higher than a predetermined value set according to the current capacity of the wire electrode. The signals from the detection circuit and these rain detection circuits are input, and when the state where the concentrated discharge state and the machining average current exceed a predetermined value continues for a predetermined time or more, the pulse ON/OFF time of the pulse power source is changed. It has a control circuit that controls and reduces the energy of arc discharge, and a sensitivity correction circuit that detects a short circuit between the wire electrode and the workpiece and reduces the detection sensitivity of the concentrated discharge detection circuit in the event of a short circuit. It is something that you have.

Furthermore, as a power supply device for electric discharge machining in a wire cut electric discharge machine, that is, a wire electric discharge machine, the Utility Model Application No. 59-872
There is one disclosed in Publication No. 9.

The power supply device for wire-cut electric discharge machining disclosed in the publication binarizes the discharge state between the wire electrode and the workpiece, continuously counts and measures the binarized abnormal discharge state at a predetermined time cycle. When the count value exceeds the set count value, the machining pulse transistor is turned off in response to the signal of the abnormal discharge phenomenon, the abnormal discharge is temporarily interrupted, and the discharge machining is started after waiting for the state between the two poles to recover. It is intended to restart the In other words, the electric discharge machining current is temporarily cut off in response to the detection of abnormal discharge, and if an abnormal discharge occurs, the abnormal discharge is counted continuously, and the machining pulse is only output when the count value exceeds a preset value. transistor is turned on.

[Problem that the invention seeks to solve]

However, the control method for wire-cut electrical discharge machining equipment disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 54-156296 reduces the electrical discharge machining current if abnormal electrical discharge continues for a predetermined period of time, and waits for natural recovery while monitoring the electrical discharge voltage. The original normal electrical discharge machining current is passed through the machine, so even though it has been reduced, as long as the current is passed, the discharge cannot be dispersed and the concentrated discharge continues.
This has the undesirable problem that it takes a long time for natural recovery, and in some cases, it is not possible to recover to a normal state, which reduces the electrical discharge machining speed. Furthermore, since a capacitor is used to measure the duration of abnormal discharge, it varies depending on the power supply voltage, temperature, etc., and there are also problems with accuracy, reproducibility, etc. Furthermore, since the duration is set manually using a variable resistor, there is a large setting error, which can lead to setting errors.
There were problems with accuracy and reproducibility.

Furthermore, the wire electrode breakage prevention circuit for wire electrical discharge machining disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 61-288930 and the above-mentioned Japanese Patent Application Laid-Open No. 61-288931 is also disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 54-156296. As well as things,
If the abnormal discharge continues for a predetermined period of time, the arc discharge energy is reduced, and the electric discharge machining speed has a hard point similar to the above.

In order to solve the above-mentioned problems, a power supply device for electric discharge machining is disclosed in the above-mentioned Japanese Utility Model Application Publication No. 59-8729. That is, in the electrical discharge machining power supply device,
Since the electric discharge machining current is completely stopped, recovery to normal electric discharge machining status is faster, the machining speed does not decrease significantly, and errors in time measurement can be reduced because counting is performed using digital signals of predetermined time cycles. Although further increasing the setting accuracy has some effect, in actual machining, abnormal discharge occurs for a long time, for example, 100 to 200 in terms of the number of machining pulses, that is, the number of discharge current pulses.
Since this occurs over a period of time equivalent to 1,000 yen, it takes a long time to recover the insulation between the wire electrode and the workpiece, and in order to restore the normal discharge state, the discharge pulse transistor must be turned off.
The discharge current must be cut off for a long time by setting the temperature to F.

By the way, abnormal discharge pulses do not function as energy for electrical discharge machining, and they occur not only for one pulse, but also for tens to hundreds of pulses continuously, which causes a decrease in machining efficiency. In that respect, there are problems.

The purpose of this invention is to solve the above-mentioned problems, and when an abnormal discharge occurs between the wire electrode and the workpiece, the insulation between the electrodes can be recovered by minimizing the abnormal discharge, that is, in a short period of time. It is an object of the present invention to provide a control device for a wire electric discharge machine that can achieve the following as quickly as possible and improve machining speed.

[Means for solving problems]

In order to solve the above problems and achieve the above objects, the present invention is configured as follows.

That is, the present invention detects the discharge state from the interelectrode voltage between the wire electrode and the workpiece for each discharge pulse, turns off the discharge current for a predetermined period upon detection of abnormal discharge,
Regarding the control device for a wire electric discharge machine, which is characterized in that the electric discharge current is then turned on and electric discharge machining is restarted, the control device for the wire electric discharge machine is characterized in that the voltage value of the inter-electrode voltage is at the abnormal voltage detection level. A wire discharge characterized in that a discharge current off detection logic is activated when the voltage is lower than the voltage value, and the discharge current is controlled to be turned off for a predetermined number of machining clocks when the voltage value of the next inter-electrode voltage is still low. This relates to the control of processing machines.

[Effect]

The control device for a wire electric discharge machine according to the present invention is configured as described above and operates as follows. That is, the present invention detects a binary discharge current for each discharge pulse, that is, normal discharge or abnormal discharge, and when abnormal discharge is detected, immediately turns off the discharge pulse transistor, etc., and interrupts the discharge current. The discharge voltage applied between the electrodes is reduced as much as possible, and since the electrode gap is in a cutoff state, abnormal discharge conditions can be resolved in a very short time. For example, residual ions in machining oil can be immediately erased. Insulation recovery is made extremely fast, and the time required to return to normal discharge is short, thereby increasing the speed of electrical discharge machining of workpieces.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a control device for a wire electric discharge machine according to the present invention will be described in detail with reference to the drawings.

In FIG. 1, a block circuit diagram showing an example of a machining power supply device for wire electric discharge machining applied to a control device for a wire electric discharge machine according to the present invention is shown. In a wire electric discharge machine, a workpiece, that is, a workpiece 2, is installed on a workpiece mount. Generally, the workpiece mount is configured for horizontal movement. That is, the workpiece mount to which the workpiece 2 is attached moves in the X direction and the Y direction according to the machining status of the workpiece 2 according to commands from the NC device, and the workpiece mount is moved in the X direction and the Y direction according to the machining status of the workpiece 2, and is connected to the wire electrode 1 supplied to the wire head. Servo motor between 5
The workpiece 2 is electrically discharge-machined into a predetermined machining shape by repeated servo movement by the servo feed mechanism 4 driven by the servo feed mechanism 4, and by a relative movement that is a combination of both movements. Furthermore, wire heads are provided above and below the workpiece 2, and these wire heads are comprised of a feeder, a feeder holding member, a die guide member, a machining fluid spray nozzle, and the like.

The wire electrode 1 fed from an automatic wire feeder via a roller guide or the like passes through a die guide member installed in the inner cylinder of the upper wire head, and after electrical discharge machining of the workpiece 2, is transferred to the inner cylinder of the lower wire head. It passes through the body and is discharged to a take-up reel, used wire collection area, etc.

In this machining power supply device for wire electric discharge machining, in the case of a transistor power supply, a machining pulse electric signal is generated by a machining clock generator 10 in response to a reference clock from an oscillator 14. In this machining clock generator 10, the pulse width P and pause time R (see FIG. 2) of the machining pulse are controlled to predetermined values. Further, the discharge current 1. flowing in the bending space 17 between the wire electrode l and the workpiece 2. is controlled by the number of transistors incorporated in the discharge current control circuit 13, and if the gap between the electrodes 17 is a distance that can cause dielectric breakdown, the discharge starts immediately, and both poles are connected to the arc column. are connected, a discharge current I9 flows, and a predetermined discharge machining is performed on the workpiece 2. When the machining clock reaches the rest time R, the discharge state stops. Here, in order to apply a discharge voltage, that is, a voltage between machining points VG to the wire electrode l and the workpiece 2, the pulse machining power supply 3 uses the machining DC power supply for discharge pulses such as a machining pulse transistor in the discharge current control circuit 13. The switch is opened and closed to apply a discharge pulse voltage between the wire electrode 1 and the workpiece 2, thereby supplying discharge energy. This discharge energy causes the workpiece 2 to
The workpiece 2 can be subjected to electrical discharge machining by melting. By the way, in the state between the two electrodes of the wire electric discharge machine, the voltage v6 between the two electrodes may not rise due to causes such as machining debris and wire vibration, resulting in abnormal discharge. If this abnormal discharge period continues for a predetermined period of time or more, the wire that is the wire electrode 1 will break, making it impossible to perform electrical discharge machining.

In particular, regarding this machining power supply device for wire electrical discharge machining,
It has the following characteristics. First, in the buffer amplifier 6, the electric signal which is the discharge voltage between the wire electrode 1 and the workpiece 2, that is, the inter-electrode voltage 6, is adjusted to a voltage value suitable for control, and the machining clock, which is the discharge voltage, output from the oscillator 14 is adjusted. In order to distinguish the discharge state into normal discharge H and abnormal discharge for each pulse, the comparator 7 compares the binarized voltage values for normal discharge H and abnormal discharge. The discrimination reference voltage of the comparator 7 is set by the potentiometer 15, and the voltage value output from the comparator 7 is the voltage value of the abnormal discharge side of the binarized voltage value, that is, the signal is set by the discharge current off detection logic. 9. In FIG. 2, waveform (A) shows the waveform of the inter-electrode voltage vG between the wire iris 1 and the workpiece 2, and the voltage value is ■. is the voltage value at the abnormal voltage detection level.

If the discharge voltage, that is, the interelectrode voltage V, is higher than the voltage value v0, it is treated as a normal discharge H, and the interelectrode voltage V, is i! j voltage If the voltage value is 0 or lower, it is treated as abnormal discharge. Waveform (B) is processing clock generator 1
The processing clock issued by 0 is shown, and the pulse width (on time) and rest time (off time) are shown. Waveform (C) shows the operating state of the discharge current off detector, and when a state in which the inter-electrode voltage V is lower than the voltage value v0 of the abnormal voltage detection level occurs, it starts operating from the rest time of the next machining clock. Start. Waveform (D) shows the discharge current off state, and even in the next machining clock, the inter-electrode voltage ■6 is the voltage value ■ at the abnormal voltage detection level. If the state is lower than , the off state is entered from the pause time of the second processing clock, and the off state continues for a predetermined number of processing clocks. That is, here, the discharge current off-pulse number setting device 12 sets the second
As shown in Figure (D), the number of pulses for turning off the discharge current is set. This discharge current off pulse number setting device 1
The setting pulse Dn is turned off at 2.

In response to this, the discharge current off pulse counter 11 is controlled to count the number n of off pulses and output the signal to the discharge current off detection logic 9. In this case, if there is even a momentary period in which the inter-electrode voltage v0 is higher than the abnormal voltage detection level from the start of the on-time of the machining clock by the machining clock generator 10 to just before the transition to the off-time, the state is normal. In the discharge state, that is, normal discharge H, the discharge current is 1. The discharge current off detection logic 9 is controlled so as not to operate by a discharge current off inhibition pulse 8 that prohibits turning off the discharge current off detection logic 9. That is, the discharge current is controlled so as not to be interrupted.

However, if the machining clock voltage vG is lower than the abnormal voltage detection level from the start of the on-time to the off-time of the machining clock by the machining clock generator IO, the state is considered to be an abnormal discharge state, that is, an abnormal discharge. , the discharge current off inhibition pulse 8 does not act, the discharge current off detection logic 9 is activated, and then the machining clock generator l
It is determined whether the inter-electrode voltage V is lower than the abnormal voltage detection level from the start of the on-time to the off-time of the next machining clock by O, and if it is still lower than the abnormal voltage detection level, , the following processing clock generator 10
It is controlled to cut off a predetermined number of machining pulses, ie, discharge current pulse signals, from the machining clock.

Next, an example of the operation of the control device for a wire electric discharge machine according to the present invention will be described with reference to FIGS. 1, 2, 3(A), and 3(B). Figure 3 (A) and Figure 3 C
B) is a flowchart showing an example of the operation of the control device for a wire electric discharge machine according to the present invention.

First, the operation switch of the wire electrical discharge machine is turned on, and the servo motor 5, wire supply device, machining fluid supply device, etc. are turned on (step 50). A clock is generated (step 51).

Processing clock generator 1 receiving the electrical signal of the reference clock
An electric signal of a machining pulse is generated based on the pulse width P and pause time R set for performing electric discharge machining using 0 (step 52). In this case, at the beginning of electrical discharge machining,
Since there is no object to be compared by the comparator 7, the discharge current OFF prohibition pulse 8 does not work, and no prohibition pulse is generated. In addition, the discharge current off detection logic 9 indicates the discharge current 1.
The machining clock from the machining clock generator 10 is input to the discharge current control circuit 13 without turning off the machining clock.

The shielding current control circuit 13 controls the electric signal of the machining pulse to have the voltage and pulse width necessary for electric discharge machining based on the electric signal of the machining clock (step 53). Next, the electric signal of the machining pulse is input to the pulse machining power source 3, and the pulse machining power source 3 is charged with a predetermined discharge current 2, that is, a discharge voltage VG, and the discharge voltage V is applied to the wire electrode 1 and the workpiece. 2 (step 54). The workpiece 2 is subjected to electrical discharge machining by applying the discharge voltage vG to the gap 17 (step 55). It is determined whether finishing or machining of the machined surface of the workpiece 2 has been completed (step 56), and if it has been completed, the operation of the wire electric discharge machine is stopped (step 57). If finishing or machining of the machined surface of the workpiece 2 has not been completed, the workpiece 2 will continue to be subjected to electrical discharge machining.

In this case, the electric signal of the discharge voltage 6 applied to the gap 17 between the wire electrode 1 and the workpiece 2 is input to the buffer amplifier 6, and the input electric signal is converted into a signal suitable for control in the buffer amplifier 6. Adjust the voltage value to ■G (step 58
) 0 Then, the voltage value v of the discharge voltage of the adjusted electrode gap 17
Input G electricity No. 48 to comparator 7, and calculate the voltage value v
6 is the voltage value of the abnormal voltage detection level■. ,In other words,
Compare with the lowest voltage value required to generate normal discharge and determine whether the voltage value ■2 is higher than the voltage value V (
Step 59). If the voltage value VG applied to the gap 17 is higher than the predetermined voltage value v0, applying the discharge voltage to the gap 17 will not cause an abnormal discharge, so continue to perform electrical discharge machining on the workpiece 2. Therefore, the process proceeds to step 51. On the contrary, if the voltage value vG applied to the electrode gap 17 is lower than the predetermined voltage value V, the discharge voltage V applied to the electrode gap 17 is the first abnormality. This is a discharge, the discharge current off detection logic 9 is activated, the number N of abnormal discharges is counted (step 60), and the number N of abnormal discharges is counted (step 60).
Step 61), if the number N is the first time, the process returns to step 51, and even if the number N is the second time, the gap 17
If the voltage value vG applied to is still lower than the predetermined voltage value V, it is assumed that an abnormal discharge will occur even if the discharge voltage V is applied to the gap 17, and the discharge current off detection logic 9 prohibits the discharge current from being turned off. Pulse 8 is applied, that is, the discharge pulse switch is turned off, and the discharge current 1. Do not let it flow into the gap 17. As a result, the electrode gap 17 has a discharge current ip
enters the cut-off state (step 62). Subsequently, a reference clock is generated from the oscillator 14 (step 63), and the number of reference clocks, that is, the number of pulses n, generated from the oscillator 14 is counted (step 64). It is determined whether the number of discharge current off pulses n0 set by the discharge current off pulse number setting device 12 is greater than (step 65). In other words, it is determined whether the number of discharge current off pulses no. , the number of reference clocks, that is, the number of pulses is counted without applying the discharge voltage v0 to the gap 17. That is, during the set number of pulses n, there is still a gap between the wire electrode 1 and the workpiece 2. Assuming that the gap 17 is in a state where an abnormal discharge occurs, the discharge voltage 6 is not applied to the gap 17, and the discharge current I of the gap 17 is cut off. When the number n increases, the machining gap 17 has already returned to a state where normal discharge can occur, that is, the discharge machining conditions are set,
The process proceeds to step 51 in order to apply the discharge voltage 1 to the electrode gap 17. In other words, when an abnormal discharge state occurs in the gap 17, the second discharge voltage v6 is detected, and if it is not yet in a normal discharge state, the discharge current IP flowing in the gap 17 is temporarily interrupted for a predetermined period. Then, the discharge pulse switch is turned on to restart the discharge machining.

(Effects of the Invention) The control device for a wire electrical discharge machine according to the present invention is configured as described above, and operates as follows.That is, the present invention can determine whether a normal discharge or an abnormal discharge is generated for each discharge pulse. If an abnormal discharge is detected, the switch for the discharge pulse transistor etc. is immediately turned off and the discharge current between the electrodes is cut off. Since abnormal discharge does not flow in between, the abnormal discharge state can be resolved in a very short time. For example, residual ions in the machining oil can be removed in a short time, resulting in quick insulation recovery, and therefore the time required to return to normal discharge. It only takes a short time to scratch,
Electric discharge machining speed can be improved. In addition, since the abnormal discharge is quickly detected for each discharge pulse and the discharge current is immediately cut off, it is possible to prevent the generation of wasteful continuous abnormal discharges that do not contribute to electric discharge machining, that is, follow-on arcs.

Therefore, even if abnormal discharge occurs, it is possible to reduce wasteful abnormal discharge that does not contribute to electrical discharge machining, and it has little negative impact on machined surface accuracy, and by increasing normal discharge that is effective for electrical discharge machining, The processing speed for objects can be improved.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an example of a machining power supply device for wire electrical discharge machining applied to a control device for a wire electrical discharge machine according to the present invention, and FIG. 2 shows a control state of the control device for a wire electrical discharge machine according to the present invention. The explanatory diagram shown as a waveform and FIGS. 3(A) and 3(B) are flowcharts showing an example of the operation of the control device for a wire electric discharge machine according to the present invention. ■−・−・−Wire electrode, 2−・Workpiece, 3・・Long・
Pulse processing power supply, 4--Servo feed mechanism, 5-- Servo motor, 6-- Banfa amplifier, 7-- Comparator, 8-- Discharge current off prohibition pulse, 9-・・Surface discharge current off detection logic, 1o・−・
Concave machining clock generator, 11...Discharge current off-pulse counter, 12--Discharge current off-pulse number setter, 13...Discharge current control circuit, I4
-・・・・・oscillator, 15−・−potentiometer. Another person for patent use Agent of Yobu TA Co., Ltd. Patent attorney Onaka Sodai 1 Figure 2

Claims (2)

[Claims] (1) The discharge state is detected for each discharge pulse from the interelectrode voltage between the wire electrode and the workpiece, and upon detection of abnormal discharge, the discharge current is turned off for a predetermined period, and then the discharge current is turned on for electrical discharge machining. A control device for a wire electrical discharge machine, characterized in that the control device controls the wire electrical discharge machine to restart. (2) When the voltage value of the electrode-to-electrode voltage is lower than the voltage value of the abnormal voltage detection level, the discharge current off detection logic is activated,
The control device for a wire electric discharge machine according to claim 1, wherein the control device controls the discharge current to be turned off for a predetermined number of machining clocks when the voltage value of the next machining voltage is still low. .