JP2756962B2 - Control device for wire electric discharge machine - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control apparatus for a wire electric discharge machine that generates a discharge between a traveling wire electrode and a workpiece and processes the workpiece with discharge energy. . [Prior Art] Conventionally, in a wire electric discharge machine, at present, a workpiece is machined using a portion in which a wire electrode travels in a vertical direction, in other words, in a vertical direction. The wire electrode is guided by a roller 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 mounted moves in the X and Y directions according to the processing status of the workpiece in response to a command from the NC unit, and performs servo movement between the wire electrode supplied to the wire head, that is, the servo function. Is repeated to advance the processing.
In other words, the wire head not only advances relatively in the machining direction during wire electric discharge machining, but also becomes unstable when the electric discharge machining becomes unstable depending on the situation of machining chips, etc. The workpiece is then retracted and then advanced again to perform electrical discharge machining on the workpiece. Then, the workpiece moves in the horizontal direction, that is, the X direction and the Y direction in response to a command from the NC device, and the movements of the two are combined, and the workpiece is subjected to electric discharge machining into a predetermined machining shape by the relative movement of the two. . Conventionally, Japanese Patent Application Laid-Open No. 54-156296 discloses a control method of a wire electric discharge machine. The control method of the wire-cut electric discharge machine has a switching element in a charging circuit of a capacitor, and uses a charge / discharge of the capacitor to supply a current to a machining gap formed between a wire electrode and a workpiece. An electric cutting process is performed by intermittently supplying a discharge current, and a charging current of the capacitor is controlled in accordance with a state of the current-carrying gap. Even if it is detected that the state of the energized working gap is short-circuited or close to a continuous arc state, the current supplied to the energized working gap is not reduced for a predetermined time, and the energizing is performed within the predetermined time. If the state of the machining gap does not return, the current flowing through the energized machining gap is reduced. Further, a wire electrode disconnection prevention circuit for wire electric discharge machining for preventing disconnection of a wire electrode in wire electric discharge machining is disclosed in JP-A-61-288930 and JP-A-61-288931. The wire-electrode wire-cutting-electrode-breaking-prevention circuit is provided with a circuit for preventing a change in a machining current flowing through at least one of a power supply provided on an upper side and a lower side with respect to a workpiece in order to supply a machining current to the wire electrode. A concentrated discharge detection circuit for detecting whether or not a concentrated discharge state is detected, and a processing average current for detecting whether or not the processing average current is equal to or greater than a predetermined value set according to the current capacity of the wire electrode. When a signal from the detection circuit and the signals from both of these detection circuits is input, and the state in which a concentrated discharge state and the machining average current have exceeded a predetermined value has continued for a predetermined time or more, the pulse of the pulse power supply
A control circuit for controlling ON and OFF times to reduce the energy of arc discharge. In addition, it has 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 when the short circuit occurs. Furthermore, a power supply device for electric discharge machining in a wire cut electric discharge machine, that is, a wire electric discharge machine, is disclosed in Japanese Utility Model Laid-Open Publication No. 59-8729. The power supply device for wire-cut electric discharge machining disclosed in this publication binarizes the discharge state between the two electrodes of the wire electrode and the work, continuously counts the binarized abnormal discharge state in a predetermined time cycle, and performs measurement. When the counted 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 suspended, and the electric discharge machining is performed after the recovery of the state between the two electrodes. Let it resume. That is, the electric discharge machining current is temporarily interrupted in response to the detection of an abnormal discharge. If an abnormal discharge occurs, the abnormal discharge is counted continuously. Transistor is turned on. [Problems to be Solved by the Invention] However, the control method of the wire-cut electric discharge machine disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 54-156296 reduces the electric discharge machining current if abnormal discharge continues for a predetermined time. While monitoring the discharge voltage and waiting for natural recovery, the original normal electric discharge machining current is passed. Therefore, even though the current is reduced, as the current flows, the discharge cannot be dispersed, the concentrated discharge continues, and the long-term natural recovery is maintained. It takes time, and in some cases, it cannot be restored to a normal state, and there is a problem that the electric discharge machining speed is reduced. In addition, since a capacitor is used to measure the duration of abnormal discharge, it varies with power supply voltage, temperature, etc.
There is also a problem in reproducibility. Further, since the setting of the duration is performed by manually operating the variable resistor, a setting error is large, a setting operation error occurs, and there is a problem in accuracy and reproducibility. Further, Japanese Patent Application Laid-Open No. 61-288930 and Japanese Patent Application Laid-Open
In the circuit for preventing wire electrode disconnection for wire electric discharge machining disclosed in JP-A-288931, the arc discharge energy is reduced if the abnormal discharge continues for a predetermined time, similarly to the circuit disclosed in JP-A-54-156296. To reduce
The electric discharge machining speed has the same problem as the above. In order to solve the above problems, a power supply device for electric discharge machining disclosed in Japanese Utility Model Application Laid-Open No. 59-8729 has been provided. That is, in the power supply device for electric discharge machining, since the electric discharge machining current is completely prevented, the recovery to the normal electric discharge machining state is quickened, and the machining speed is not reduced so much. Since counting can reduce the error in time measurement and further increase the setting accuracy has a temporary effect, but in actual machining, abnormal discharge takes a long time, for example, the number of machining pulses, that is, the number of discharge current pulses. It takes a long time to recover the insulation between the wire electrode and the workpiece because it occurs for a time equivalent to 100 to 200 pieces, and the discharge pulse transistor is turned off to recover the normal discharge state. The current must be interrupted for a long time. By the way, the abnormal discharge pulse does not function as energy for electric discharge machining, and is generated not only for one pulse but also continuously for several tens to several hundreds of pulses, which causes a reduction in machining efficiency. In that respect, there is a problem. SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problem, and when abnormal discharge occurs between poles between a wire electrode and a workpiece, the abnormal discharge is minimized, that is, the insulation recovery between the poles is shortened in a short time. An object of the present invention is to provide a control device for a wire electric discharge machine which can be achieved as quickly as possible and can improve a machining speed. [Means for Solving the Problems] The present invention is configured as follows to achieve the above object. The present invention relates to a buffer amplifier that adjusts an electric signal of a gap voltage between a wire electrode and a workpiece to a discharge voltage value suitable for discharge pulse control, and a discharge pulse width of μse.
an oscillator for transmitting a discharge pulse on the order of c, generating a processing clock pulse for receiving a reference clock pulse from the oscillator and generating an electrical signal in which the pulse width and pause time of the processing pulse are controlled to predetermined processing clock pulses The discharge voltage value is set to one of a preset reference voltage for detecting whether the discharge voltage value from the buffer amplifier for one discharge pulse from the oscillator or the oscillator is normal discharge or abnormal discharge. And a comparator that compares each of the discharge pulses with the discharge pulse. The comparator compares the discrimination reference voltage with the discrimination reference voltage. The comparator compares the discrimination reference voltage with the discrimination reference voltage. Sometimes, the discharge current is turned on, and when the discharge voltage value is the abnormal discharge having a low value, A discharge current off prohibition pulse for detecting that the subsequent discharge voltage value is the abnormal discharge and turning off the discharge current, a discharge current is generated when the discharge current off prohibition pulse operates, and the discharge current off prohibition pulse is generated. A discharge current off detection logic that turns off the discharge current for a predetermined period of time by not operating, and counts a discharge current off period of the discharge current off detection logic by operating from a pause time of a machining clock pulse in which the abnormal discharge has occurred. The discharge current off pulse counter, and the number of pulses in the off state of the discharge current from the discharge current off pulse counter is greater than or equal to a predetermined voltage value at which the gap voltage at which residual ions in the machining fluid are erased and insulation is restored. The off state is continued until a predetermined predetermined number of processing clock pulses is reached. The discharge current is turned on discharge current off pulse number setting device to resume electric discharge machining for the workpiece, a control device of a wire electric discharge machine, characterized in that it consists after a time it becomes. [Operation] 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 control device of this wire electric discharge machine detects a discharge current binarized for each discharge pulse, that is, a normal discharge or an abnormal discharge, and if an abnormal discharge is detected, immediately turns off a discharge pulse transistor and the like. Since the discharge current is interrupted only for the set period, the state of applying abnormal discharge voltage between the electrodes is reduced as much as possible. Since the speed is increased and the gap is cut off, the abnormal discharge state can be eliminated in a very short time, and the time required to return to the normal discharge can be shortened. Therefore, the electric discharge machining speed for the workpiece can be increased. EDM time can be reduced. [Embodiment] Hereinafter, an embodiment 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. FIG. 1 is a block circuit diagram showing an example of a power supply device for wire electric discharge machining applied to a control device of a wire electric discharge machine according to the present invention. In a wire electric discharge machine, a work, that is, a work 2
Is installed. Generally, the work mount is configured to be movable in a horizontal direction. The work mount on which the work 2 is mounted moves in the X and Y directions in accordance with the processing state of the work 2 according to a command from the NC device, and moves between the wire electrode 1 supplied to the wire head. The servo movement is repeatedly advanced by a servo feed mechanism 4 driven by a servo motor 5, and the workpiece 2 is subjected to electrical discharge machining into a predetermined machining shape by a relative motion obtained by combining the two. Further, a wire head is provided above and below the workpiece 2, and these wire heads are composed of a power supply, a power supply holding member, a die guide member, a working liquid jet nozzle, and the like.
The wire electrode 1 sent from the 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, discharges the workpiece 2, and then discharges the inner cylinder of the lower wire head. It is discharged to a take-up reel, a used wire reservoir, etc. through the body. In the machining power supply device for wire electric discharge machining, in the case of a transistor power supply, a machining clock pulse generator 10 receives a reference clock pulse from the oscillator 14 and generates an electric signal of a machining pulse. In this machining clock pulse generator 10, the pulse width P and the pause time R of the machining pulse
(See FIG. 2) is controlled to a predetermined value. Further, the discharge current I _P flowing through the machining gap 17 between the wire electrode 1 and the workpiece 2,
It is controlled by the number of transistors incorporated in the discharge current control circuit 13. In this case, if the distance that the gap between the poles 17 can be dielectric breakdown immediately discharge is started, both electrodes are connected by the arc column, the discharge current I _P flows, the predetermined discharge machining the workpiece 2 Done. When the machining clock pulse reaches the pause time R, the discharge state stops. Here, for applying a discharge voltage i.e. inter-electrode voltage V _G with respect to the wire electrode 1 and the workpiece 2, the pulse machining power source 3, a discharge pulse, such as a transistor for processing pulses in the working DC power supply discharge current control circuit 13 The switch is opened and closed by a switch for applying a discharge pulse voltage between both electrodes of the wire electrode 1 and the workpiece 2 to supply discharge energy. The workpiece 2 can be subjected to electrical discharge machining by melting the workpiece 2 by the discharge energy. However, both electrodes between states of a wire electric discharge machine, machining waste, depending on the cause of wire vibration may become abnormal discharge does not rise that bipolar voltage V _G. If the abnormal discharge period continues for a predetermined period or more, the wire serving as the wire electrode 1 is broken, and it becomes impossible to perform electric discharge machining. The control device of this wire electric discharge machine has the following features in particular. First, in the buffer amplifier 6,
Discharge voltage between wire electrode 1 and workpiece 2, that is, voltage between contacts
The electrical signal is V _G was adjusted to a voltage value suitable for discharge pulse control distinguishes discharge state to the normal discharge H and abnormal discharge L each processing clock pulse or discharge pulse is issued from the processing clock pulse generator 10 Therefore, the comparator 7 compares the binarized value of the voltage value into the normal discharge H and the abnormal discharge L. The discrimination reference voltage of the comparator 7 is set by the potentiometer 15, and the comparator 7
Are output to the discharge current off detection logic 9 as a voltage value of the abnormal discharge L of the binarized voltage value, that is, a signal. In FIG. 2, the waveform (A) shows the waveform of the voltage V _G between the wire electrode 1 and the workpiece 2 with respect to the passage of time t (unit: μsec) on the horizontal axis, and the voltage value V ₀ is abnormal. This is the voltage value of the voltage detection level. If the discharge voltage or higher than the inter-electrode voltage V _G is the voltage value V _0, and treated as a normal discharge H, inter-electrode voltage V _G is equal lower than the voltage value V _0, abnormal discharge L Process as Waveform (B) shows the time t
A processing clock pulse generated by the processing clock pulse generator 10 with respect to (unit: μsec) progress is shown, and a pulse width (on time) and a pause time (off time) are shown. The waveform (C) shows the operation state of the discharge current off detector with respect to the passage of time t (unit: μsec). Waveform (D), time t
(Unit, .mu.sec) shows a discharge current OFF state with respect to the elapsed, when the abnormal discharge subsequent machining machining gap voltage V _G at the clock pulse is lower than the voltage value V ₀ which abnormal voltage detection level state, the second processing clock The pulse generator is turned off from the pause time of the pulse, and is kept off for a predetermined number of machining clock pulses. Here, the discharge current off pulse number setting device
12, the number of pulses for turning off the discharge current is set as shown in FIG. 2 (D). The discharge current off pulse counter 11 responds to the set pulse number n ₀ to be turned off in the discharge current off pulse number setting device 12.
Are 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 a higher period than inter-electrode voltage V _G is abnormal voltage detection level until immediately before entering off-time from the on-time start of processing clock pulse by the processing clock pulse generator 10 even momentarily, the state as a normal discharge state i.e. normal discharge H, are controlled so as not work discharge current off detection logic 9 by the discharge current off prohibiting pulse 8 to prohibit turning off the discharge current I _P. That is, the discharge current is controlled so as not to be interrupted. However, the control device of this wire electric discharge machine is
When processing a clock pulse generator 10 inter-electrode voltage V _G until immediately before entering off-time from the on-time start of processing clock pulse by less than abnormal voltage detection level,
This state is an abnormal discharge state, that is, abnormal discharge L, in which the discharge current off prohibition pulse 8 does not act, the discharge current off detection logic 9 is activated, and the processing clock pulse generator 10 generates the next processing clock pulse. on inter-electrode voltage V _G until immediately before entering the off-time from the time the start it is determined whether lower than abnormal voltage detection level, when still lower than the abnormal voltage detection level, the next processing clock pulse generator It is controlled so that a predetermined number n ₀ of processing pulses, that is, a signal of a discharge current pulse, is cut off from the processing clock pulse by the device 10. Next, an example of the operation of the control device of the wire electric discharge machine according to the present invention will be described with reference to FIGS. 1, 2, 3 (A) and 3 (A).
This will be described with reference to FIG. FIGS. 3 (A) and 3 (B) are flowcharts showing an example of the operation of the control device of the wire electric discharge machine according to the present invention. First, turn on the operation switch of the wire electric discharge machine,
The servo motor 5, the wire supply device, the machining fluid supply device, and the like are turned on (step 50). In order to perform electric discharge machining on the workpiece 2, a reference clock pulse is generated by the oscillator 14 (step 51). Upon receiving the electric signal of the reference clock pulse, the machining clock pulse generator 10 generates a machining pulse electric signal based on the set pulse width P and the pause time R for performing electric discharge machining (step 5).
2). In this case, at the beginning of electric discharge machining, the comparator 7
Therefore, the discharge current off prohibition pulse 8 does not work, and no prohibition pulse is generated. Further, the discharge current off detection logic 9 discharge current machining the discharge current control circuit 13 without turning off the I _P clock pulse generator 10
Input the processing clock pulse from The discharge current control circuit 13 controls the electric signal of the machining pulse having a voltage and a pulse width necessary for electric discharge machining based on the electric signal of the machining clock pulse (step 53). Next, the electric signal of the machining pulse is input to the pulse machining power supply 3, and the pulse machining power supply 3 outputs a predetermined discharge current.
I _P or discharge voltage V _G is charged, is applied to the discharge voltage V _G to the machining gap 17 between the wire electrode 1 and the workpiece 2 (Step 5
Four). Workpiece 2 is discharge machining by discharge voltage V _G to the machining gap 17 is applied (step 55). It is determined whether finishing or machining of the machining 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, electrical discharge machining is continuously performed on the workpiece 2. In this case, the electrical signals of the discharge voltage V _G applied to the machining gap 17 between the wire electrode 1 and the workpiece 2 is input to the buffer amplifier 6, the electrical signal input suitable for controlling the buffer amplifier 6 adjusting the voltage value V _G (step
58). Next, the voltage value V _{G of} the adjusted discharge voltage of the gap 17
The electrical signal is input to the comparator 7 of the voltage value V _G of the abnormal voltage detection level voltage value V ₀ which, in other words, compared to the minimum voltage value required to generate normal discharge, the voltage value
V _G is determined whether higher than the voltage value V ₀ (Step 5
9). Since the voltage value V _G applied to the machining gap 17 is higher than the predetermined voltage value V ₀ is not a abnormal discharge even by applying a discharge voltage between the electrodes 17, continued electrical discharge machining with respect to the workpiece 2 , The process proceeds to step 51. On the contrary, when the voltage value V _G applied to the machining gap 17 is lower than the predetermined voltage value V _0, the discharge voltage V _G applied to the machining gap 17
Is the first abnormal discharge, and 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 determined (step 61). When the number N is the first time, the process is returned to step 51, and the number N is 2 If the voltage value V _G also becomes round eyes is applied to the machining gap 17 is still lower than the predetermined voltage value V _0, the discharge voltage between the electrodes 17
As it will be abnormal discharge by applying a V _G, the discharge current by the off-detection logic 9 exerts a discharge current off prohibiting pulse 8, i.e. the switch discharge pulse by turning off the discharge current I _P
Do not flow into gap 17. As a result, the gap 17
The discharge current _IP is cut off (step 62). Subsequently, a reference clock pulse is generated from the oscillator 14 (step 63), and the number of reference clock pulses generated from the oscillator 14, that is, the pulse number n is counted (step 6).
Four). Next, it is determined whether or not the pulse number n is greater than the discharge current off pulse number n ₀ set by the discharge current off pulse number setting device 12 (step 65). In other words,
Discharge current greater until than the discharge current off pulse number n ₀ set by the off pulse number setting unit 12 counts the reference clock pulse number or pulse number n without applying a discharge voltage V _G to the machining gap 17. That is, the set pulse number n ₀
During the, as a state where the machining gap 17 generates the abnormal discharge between the still and the wire electrode 1 and the workpiece 2, the discharge voltage V _G to the machining gap 17 is not applied, the discharge current I of the machining gap 17 Block _P. When the reference clock pulse number, that is, the pulse number n becomes larger than the set pulse number n ₀ , it is determined that the gap 17 has already returned to a state where normal discharge can be performed, that is, the discharge machining condition is satisfied, and the discharge voltage V _{G is} applied to the gap 17. In order to apply
Proceed to In other words, if an abnormal discharge state occurs in gap 17,
Detects the discharge voltage V _G to the times eyes, if not already normal discharge state, the discharge current I _P flowing through the inter-electrode gap 17 once cut off for a predetermined period of time, the discharge machining in the subsequent turn on the discharge pulse switch Let it resume. [Effects of the Invention] 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 control device of this wire electric discharge machine detects whether the discharge is normal or abnormal at each discharge pulse, and when abnormal discharge is detected, switches off the discharge pulse transistor and shuts off the discharge current between the electrodes immediately. As a result, the state where abnormal discharge is applied between the poles is minimized, and the abnormal discharge state can be eliminated in a very short time because no abnormal discharge is applied between the poles. And so on, the insulation recovery is fast, and the time required to return to normal discharge is extremely short, so that the electric discharge machining speed can be improved. Therefore, if the control device of this wire electric discharge machine is used, abnormal discharge is detected quickly for each discharge pulse, and the discharge current is immediately cut off. That is, it is possible to prevent the generation of the downstream arc. In addition, if the control device of this wire electric discharge machine is used, even if abnormal electric discharge occurs, useless abnormal electric discharge which does not contribute to electric discharge machining can be reduced.
The machining speed with respect to the workpiece can be improved by increasing the normal electric discharge effective for electric discharge machining with little adverse effect on the machining surface accuracy.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an example of a power supply device for wire electric discharge machining applied to a control device for a wire electric discharge machine according to the present invention, and FIG. 2 is a wire electric discharge machine according to the present invention. FIG. 3A and FIG. 3B are flowcharts showing an example of the operation of the control device of the wire electric discharge machine according to the present invention. 1 ... wire electrode, 2 ... workpiece, 3 ... pulse machining power supply, 4
… Servo feed mechanism, 5… Servo motor, 6… Buffer amplifier, 7… Comparator, 8… Discharge current off prohibition pulse, 9… Discharge current off detection logic, 10… Machining clock pulse generator, 11 …… Discharge current off pulse counter, 12
... discharge current off pulse number setting device, 13 ... discharge current control circuit, 14 ... oscillator, 15 ... potentiometer.

Continuation of front page    (56) References JP-A-60-34223 (JP, A)                 JP-A-61-159326 (JP, A)                 Actual opening sho 59-8729 (JP, U)

Claims (1)

(57) [Claims] A buffer amplifier for adjusting an electric signal of a gap voltage between the wire electrode and the workpiece to a discharge voltage value suitable for discharge pulse control; an oscillator for transmitting a reference clock pulse having a discharge pulse width on the order of μsec; A processing clock pulse generator that receives a reference clock pulse from an oscillator and generates an electric signal in which the pulse width and pause time of the processing pulse are controlled to a predetermined processing clock pulse; A comparator that compares the discharge voltage value with one voltage value of a preset discrimination reference voltage for each discharge pulse to detect whether the discharge voltage value from the buffer amplifier is normal discharge or abnormal discharge; When the discharge voltage value is the normal discharge having a high value by comparison with the discrimination reference voltage in the comparator. A discharge current off prohibition pulse for turning on a discharge current, and detecting that the subsequent discharge voltage value is the abnormal discharge when the discharge voltage value is the abnormal discharge having a low value, and turning off the discharge current; A discharge current off detection logic that turns on the discharge current when a discharge current off prohibition pulse is generated and turns off the discharge current for a predetermined period by not generating the discharge current off prohibition pulse; a machining clock in which the abnormal discharge has occurred A discharge current off-pulse counter that operates from the pause time of the next processing clock pulse after the pulse and counts a discharge current off period of the discharge current off detection logic; and a discharge current off state from the discharge current off pulse counter. When the number of pulses is equal to or lower than the predetermined voltage at which the residual ions in the machining fluid are erased and the insulation is restored. The off state is continued until a predetermined predetermined machining clock pulse number equal to or higher than the voltage value is reached, and after a lapse of time equal to or higher than the predetermined voltage value, the discharge current is turned on to perform electric discharge machining on the workpiece. A control device for a wire electric discharge machine, comprising: a discharge current off pulse number setting device for restarting.