JPH02274422A - Foreknowing method for short circuit in electrochemical machining - Google Patents

Abstract

PURPOSE:To foreknow generation of an arc, which is a premonitory sign of a short circuit, so as to prevent the short circuit caused by generation the arc by detecting interpole voltage for its abnormally rising phenomenon during supplying a machining pulse and interrupting its supply. CONSTITUTION:In the case of electrochemical machining in which a workpiece is electrochemically machined by supplying a machining pulse between electrodes, opposedly provided with a predetermined space, and the workpiece in an electrolyte, a discriminator 35 detects interpole voltage for its abnormally increasing phenomenon during supplying the machining pulse. By an off-signal from this discriminator 35, each AND gate 54-1 to 54-n is turned off, and each transistor 42-1... of each discharge switch 25-1 is turned off stopping a discharge of each capacitor 23-1. Thus preventing generation of a short circuit, the workpiece W can be prevented from burning.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for predicting short circuits in electrolytic machining, and in particular, predicts the occurrence of arcs during supply of machining pulses, prevents short circuits, and improves the quality of workpieces. A method for predicting short circuits in electrolytic machining that can prevent burnouts, etc. is developed.

[Prior art] Conventionally, electrolytic machining is performed while feeding the electrode to maintain a small gap between the electrode and the workpiece, and a special inter-electrode gap abnormality detection device has been used to detect sparks generated between the electrode and the workpiece. A method disclosed in Japanese Patent Publication No. 56-30124 is known, and a method for predicting short circuits in electrolytic machining in which a workpiece is electrolytically processed by passing a pulsed current using a thin wire as an electrode is disclosed in Japanese Patent Publication No. 57-22690. Those disclosed are known.

[Problems to be Solved by the Invention] Incidentally, the former abnormality detection device detects an abnormal phenomenon between poles by detecting a voltage drop phenomenon and a current increase phenomenon when a spark occurs. However, since this device detects the occurrence of spark itself, which is an abnormal phenomenon, the workpiece has already been burnt out by the spark at the time of detection. Therefore, for example, as disclosed in Japanese Patent Application Laid-open No. 63-216628, when using an electrode having an electrode surface that follows the machined surface of a workpiece for electrolytic finishing of a workpiece, it is possible to achieve a desired three-dimensional finish. This poses a fatal problem for finishing work, as it instantly burns out the workpiece that has been machined into the shape.

In addition, the latter short circuit prediction method predicts the occurrence of a short circuit rather than detecting the occurrence of an abnormal phenomenon itself, but in this prediction method, the voltage between the electrodes during the machining pulse pause time is Since this method detects and predicts short circuits based on an abnormal drop in the inter-electrode voltage, which shows a substantially constant value during normal times, it is not possible to predict short circuits that occur during the supply of machining pulses. Therefore, especially when the pulse width of the supplied machining pulse is relatively large, as in the electrolytic finishing process described above, a short circuit may occur due to machining debris generated in the gap during the supply of the machining pulse, causing burnout of the workpiece. There was the same problem as the former, that is, it was stored away.

Therefore, the purpose of this invention is to solve the above-mentioned problems,
In particular, it is an object of the present invention to realize a method for predicting short circuits in electrolytic machining, which prevents short circuits and prevents burnout of workpieces by predicting the occurrence of arcs during supply of machining pulses.

[Means for Solving the Problem] In order to achieve this object, the first invention of this application supplies a machining pulse between an electrode and a workpiece, which are disposed opposite to each other with a predetermined gap in an electrolytic solution. A method for electrolytic machining, characterized by comprising the steps of: detecting an abnormal increase in the voltage between machining electrodes during the supply of the machining pulse; and, based on this detection, cutting off the supply of the machining pulse. Further, in a second invention, the step of detecting the abnormal increase phenomenon of the machining voltage includes the step of detecting the machining voltage during the supply of the machining pulse, and the peak value of the machining voltage immediately after the start of supply of the machining pulse. and a step of comparing the peak value with the electrode-to-electrode voltage.Furthermore, the third invention is characterized in that the step of detecting the abnormal increase phenomenon of the electrode-to-electrode voltage includes the step of detecting the abnormal increase phenomenon in the electrode-to-electrode voltage. The method includes the steps of: detecting a voltage between machining points during supply of machining pulses; detecting a bottom value after a peak value of the voltage between machining electrodes; and comparing this bottom value with the voltage between machining holes. Features.

Further, a fourth aspect of the present invention provides a method for electrolytically machining a workpiece by supplying a machining pulse due to discharge of electric charge of a capacitor between electrodes and a workpiece that are disposed opposite to each other at a predetermined gap in an electrolytic solution, in which the workpiece is charged by charging the capacitor. a step of setting a voltage; a step of detecting a voltage between the machining pulses while the machining pulse is being supplied; and a step of comparing this machining voltage with a set voltage of the capacitor, and cutting off the supply of the machining pulse based on the comparison result. It is characterized by comprising a step.

[Operation] According to the configuration of the first invention of this application, when a machining pulse is supplied between the electrode and the workpiece, which are disposed opposite to each other with a predetermined gap in the electrolytic solution, immediately before arcing, which is a sign of a short circuit, occurs. Based on the knowledge obtained through experiments that the voltage between the electrodes increases abnormally, the phenomenon of abnormal increase in the voltage between the electrodes is detected, and when this phenomenon is detected, the supply of machining pulses is cut off to cause a short circuit. This prevents burnout of the workpiece.

Further, according to the configuration of the second invention, when the machining voltage due to the machining pulse supply is equal to or higher than the peak value immediately after the machining pulse supply starts, for example, it is detected as an abnormal increase phenomenon of the machining pulse voltage,
Since the supply of machining pulses is cut off, arc occurrence can be predicted at an early stage.

Furthermore, according to the configuration of the third invention, the bottom value after the peak value of the voltage between electrodes is detected, and for example, when the voltage between electrodes is equal to or higher than a predetermined value with respect to this bottom value, it is detected as an abnormal increase phenomenon of the voltage between electrodes. Therefore, the occurrence of an arc can be predicted at an earlier point in time.

Further, according to the configuration of the fourth invention, the machining pulse voltage is compared with the set voltage of the condenser by comparing the machining pulse voltage due to discharge of the electric charge of the condenser with the set voltage of the condenser. In order to cut off the supply, a simple configuration is used to predict the occurrence of an arc and prevent the occurrence of a short circuit.

[Example] Hereinafter, an example of the present invention will be described in detail and specifically with reference to the drawings.

1 to 3 show an electrolytic finishing apparatus 1 capable of implementing each invention of this application. In FIG. 1, an electrolytic finishing processing apparatus 1 includes an electrode fixing device 3 that fixes an electrode 2, a work fixing device 5 that fixes a workpiece 4, a drive converter 7 that converts the rotational motion of a motor 6 into reciprocating motion, and a processing pulse. a control device 12 consisting of a head drive control section 9, a processing condition control section 10, an electrolyte flow control section 11, etc., an input device 13 for inputting various data, etc., and an electrolyte filtration system that filters the electrolyte. [Apparatus] Consists of 4, processing tank 15, etc.

The electrode fixing device 3 has an electrode 2 made of pure copper, graphite, etc. attached to the lower end of a rod 16 provided at its lower part, with a gap such that the electrode surface 2a and the processed surface 4a of the workpiece 4 are spaced in a three-dimensional direction. Fix it so that it maintains 17. The electrode fixing device 3 is moved up and down by the rotation of the motor 6 in response to a control signal from the head drive control section 9, and sets a predetermined gap 17 between the electrode surface 2a and the processing surface 4a. Further, the workpiece fixing device 5 is a table made of highly insulating granite or ceramics, and the workpiece 4 is fixed on the upper surface thereof using a setting jig or the like (not shown). In addition, in Figure 1,
Reference numeral 18 is a nozzle for spouting clean electrolyte into the gap 17.

The input device 13 inputs the material and machining area of the workpiece 4, the target machining amount, machining pulse conditions, initial electrode gap, etc., and sends these signals to the head drive control section 9 of the control device 12 and the machining conditions. Output to control unit IO. Further, the electrolyte filtration device 14 filters an electrolyte containing electrolytic products generated during machining, and the electrolyte is added to the machining tank 15 at the start of machining based on the control signal of the electrolyte flow control unit 110. At the same time, the gap 1 between the electrode 2 and the workpiece 4 is supplied during machining.
In order to remove the machining debris generated in step 7, a clean electrolytic solution is jetted into the gap 17 through the nozzle 18 in synchronization with the electrode 2 which moves upward every time a machining pulse is supplied.

A power supply device 8 that supplies predetermined machining pulses between the electrode 2 and the workpiece 4, and the machining condition control section 10 that controls the power supply device 8 are configured as shown in FIG. 2, for example.

That is, the power supply device 8 includes a DC power supply section 19 and a charging/discharging section 20, and the DC power supply section 19 includes a transformer 21 and a rectifier 22.
A transformer 21 lowers the voltage to a predetermined value, a rectifier 22 rectifies the DC current, and supplies the direct current to capacitors 23-1 to 23-n, which will be described later.

The charging/discharging unit 20 also includes a plurality of capacitors 23-1 to 23-n that discharge charges between electrodes, and each of these capacitors 23-
Diodes 24-1 to 24-n connected to diodes 1 to 23-n to prevent backflow of charges to the DC power supply section 19 side, and a discharge switch 25-1 that is opened and closed to discharge charges to the discharge side.
25-n, a charging switch 26, etc., for supplying and disconnecting power from the DC power supply section 19 in order to charge each of the capacitors 23-1 to 23-n to a predetermined value.

The processing condition control unit 10 controls the capacitors 23-1 to 23-n.
A voltage detector 27 detects the charging voltage value of the voltage detector 27, a voltage comparator 29 compares the charging voltage value detected by the voltage detector 27 with the output value from the D/A converter 28, and a current detector 30 that detects the current value of the electric charge; a current peak hold circuit 31 that holds the peak value of the current detected by the current detector 30; and a current peak hold circuit 31 that holds the peak value of the current detected by the current detector 30; /A converter 3
A current comparator 33 compares the output value of the electrode 2 with the output value of the electrode 2, a voltage detector 34 detects the voltage between the electrodes 2 and the workpiece 4, and a voltage detector 34 detects the voltage between the electrodes 2 and the workpiece 4. ,
A voltage change discriminator 35 that discriminates the change, and an input signal from the voltage change discriminator 35 and a pulse generator 38 that generates a pulse with a predetermined time width are used to control each discharge switch 25.
Gate circuit 3 that outputs opening/closing drive signals to -1 to 25-n
6, a charging voltage setting device 37 that sets a charging voltage value to be supplied to each of the capacitors 23-1 to 23-n and outputs the signal to the D/A converter 28, and a charging voltage setting device 37 that sets a current value flowing between the electrodes. It consists of a current setter 39 that outputs the signal to the D/A converter 32, and a CPO 40 that calculates and processes processing conditions and the like based on input signals from each of the circuits.

FIG. 3 is a circuit configuration diagram that further embodies the schematic configuration diagram of FIG. 2, and the same parts as in FIG. 2 are given the same reference numerals and will be explained.

The DC power supply section 19 is connected to each coil 21-1 of the transformer 21.
21-3 to drop the voltage to a predetermined value, each diode 22-1 to 22-3 rectify the voltage to obtain a DC power, and output it via the resistor 41.

The discharge switch 25-1 (discharge switch 25-1~
Since all 25-n have the same configuration, the discharge switch 25-n
1) is five transistors 42
-1 to 46-1, six resistors 47-1 to 52-1,
and a diode 53-1, each of the transistors 42-1 to 46-1 is sequentially turned on by an opening/closing drive signal input from an AND gate 54-1 of the gate circuit 36,
The charge in the capacitor 23-1 is discharged.

Note that the capacitor 23-1 has a capacitance of 0°2, for example.
It is configured by connecting five 2F (farad) capacitors 23a to 23e in parallel, and by further connecting these in parallel, the power supply device 8 as a whole has a capacitance of 10 to 20F. A resistor 55-1 is connected in parallel to this capacitor 23-1.

Further, the charging switch 26 is a discharging switch 25-1.
Almost similarly, it is composed of five transistors 56 to 60, seven resistors 61 to 67, and a diode 68, and each transistor 56 to 60 is turned on and off by the output of the voltage comparator 29 to generate a direct current. The power from the power supply section 19 is supplied and cut off, and each of the capacitors 23-1 to 23-n is charged to a predetermined value.

The voltage detector 27 includes a capacitor 69 whose one end is grounded.
-1 and outputs a charged voltage value obtained by dividing the voltage by two series resistors 70 and 71 connected in parallel with this capacitor 69. The output side of this voltage detector 27 is connected via a resistor 72 to one input side of a comparator 73 of the voltage comparator 29 . The other input side of the comparator 73 is connected to the output side of the D/A converter 28 via a resistor 74. A diode 75 is connected between the resistor 72, 74 and the comparator 73.
．． Connect 76. The output side of this comparator 73 is connected via the resistor 61 to the base of the transistor 56 of the charging switch 2G.

The current detector 30 includes a resistor 77 on the ground side of the electrode 2, and connects the electrode 2 side of the resistor 77 to one input side of an amplifier 79 via a resistor 78, and connects the other input side of the amplifier 79 to the other input side of the amplifier 79. The input side is grounded via a resistor 80. This amplifier 79 has an output side connected to the input side connected to the resistor 78 via a resistor 81, and an output side connected to one input side of an amplifier 82. This amplifier 82 connects the other input side to the output side, and outputs the inter-electrode current value from the output side.

The current peak hold circuit 31 includes the current detector 3
The output side of the 0 amplifier 82 is connected to the other input side of an amplifier 83, and one input side of this amplifier 83 is connected to the output side via a diode 84.

Further, one input terminal of the amplifier 83 is connected to one input side and an output side of the amplifier 86 via a resistor 85, and the output side of the amplifier 83 is connected to the other input side of the amplifier 86 via a diode 87. Connecting. the amplifier 86
The other input side of is grounded via a capacitor 88, and an analog switch 89 is connected across this capacitor 880. An analog switch 89 connects to the pulse generator 38.

This current peak hold circuit 31 is connected to the current detector 3.
Hold the peak value of the current value detected at 0,
This value is output to a current comparator 33, which will be described later, and
It is reset by the reset pulse of the pulse generator 38.

The output side of the D/A converter 32 and the output side of the amplifier 86 of the current peak hold circuit 31 are connected to a resistor 90, respectively.
．． 91 to the input side of the comparator 92 of the current comparator 33, and diodes 93, 94 are connected between each resistor 90, 91 and the comparator 92, respectively. A resistor 95 is connected to the output side of the comparator 92, and this resistor 95
While connecting one end of to a grounded diode 96,
It is connected to the terminal 97 of the CPU 40.

The signal at the terminal 97 controls the inter-electrode current value to a predetermined current value.

The electrode-to-electrode voltage detector 34 includes two coils 100.101 and 102.1 connected in series to the electrode 2 and the workpiece 4.
03 and a noise cutting filter consisting of capacitors 104 and 105 are connected, and the coil 103 is connected to a resistor 106.
is connected to one input side of amplifier 107 via.

The coil 10 is connected to the other input terminal of the amplifier 107.
1 through the resistor 108, and the resistor 109
Ground through. Further, the output side of the amplifier 107 is connected to one input side via a resistor 110 and to one input side of an amplifier 112 via a resistor 111. The other input side of the amplifier 112 is grounded via a resistor 113, and its output side is connected to one input side via a resistor 114, detects and amplifies the voltage between poles, and uses the voltage change discriminator 35 to be described later. Output to.

The gate circuit 36 is an AND game) 54-1 to 54-
n, the pulse generator 38 and the voltage change discriminator 3
It is turned on and off by the signal from 5.

That is, the ON signal (H level) of the processing command pulse of the pulse generator 38 and the ON signal (H level) of the voltage change discriminator 35 are
H), each AND game) 5 in order to discharge the charge of each of the capacitors 23-1 to 23-n to the discharge side as desired.
4-1 to 54-n are turned on, and discharge switches 25-1 to 25-2 are turned on.
5-n transistors 42-1 to 42-0 are turned on to discharge each capacitor 23-1 to 23-n,
In order to stop discharging the electric charge of each of the capacitors 23-1 to 23-n by at least one off signal (L level) from the pulse generator 38 or the voltage change discriminator 35,
Each of the AND gates) 54-1 to 54-n is turned off, and each transistor 42 of each discharge switch 25-1 to 25-n is turned off.
-1 to 42-n are turned off and each capacitor 23-1 to 23-
Stop the discharge of n. In this case, each AND gate 54
The opening/closing control of -1 to 54-n can also be selectively controlled by the pulse generator 38 depending on the current density of the required processing pulse. Note that reference numeral 115 in FIG. 3 is a diode that prevents the discharge switches 25-1 to 25-n from being destroyed by back electromotive force.

The above is a description of the electrolytic finishing apparatus 1 that can implement each invention of this application. Next, the basic principles of each invention of this application will be explained based on FIGS. 4 and 5.

FIG. 4(a) shows that the electrode gap between the electrode 2 and the workpiece 4 of the electrolytic finishing apparatus 1 is kept constant, and that the gap between the electrodes (
The waveforms of the gap voltage were obtained through experiments when a machining pulse with a pulse intensity t as shown in C) was supplied. increasing the set voltage of the charging voltage setter 37 from state A in the region;
That is, this is a waveform when the charging voltage of the capacitors 23-1 to 23-n is increased (the charging voltage is increased rapidly).

Observing the change in the gap voltage from this figure, the gap voltage rises and reaches a peak at the same time as the machining pulse is turned on, and then, when the gap is normal (a), it decreases monotonically; As the machining condition becomes abnormal (increasing the voltage), the voltage between the electrodes becomes oscillatory, and when an arc occurs between the electrodes, as in corrugated machining, the voltage between the electrodes increases abnormally and the peak value A phenomenon that greatly exceeds the above occurs.

Possible causes of this phenomenon are as follows. That is, as shown in the equivalent circuit of FIG.
There is a resistance R and an inductance L that the wiring has, and the relationship between the charging voltage V1 of the capacitor and the voltage between electrodes V2 is experimentally determined to be Vl-3 in the case of normal electrolytic finishing processing by the electrolytic finishing device 1. >V2 and the gap between the electrodes becomes abnormal, a sudden change in current occurs, and the voltage between the electrodes v2 increases due to the inductance of the wiring. At this time, the inter-electrode voltage V2 is the normal inter-electrode voltage and the Ldi/dt due to the current change is superimposed, and just before the arc occurs, this di/dt is large and reaches ■2'', 2■. The interelectrode voltage V2 will rise rapidly.

Note that FIG. 4(b) shows a current waveform corresponding to the voltage wave carving where an arc occurred, and from this figure, the following can be inferred about the circumstances leading to the short circuit.

That is, A in the figure until the machining current value abnormally decreases is the part where normal machining is performed, and the machining current value gradually decreases from the peak value due to the generation of bubbles, machining debris, etc. Then, due to the generation of a large amount of air bubbles, the gap between the electrodes becomes temporarily insulated, and the current value between the electrodes abnormally decreases.Then, the insulation condition is eliminated and the current value between the electrodes increases. The gap between the electrodes is in an extremely unstable state, and the gap between the electrodes becomes temporarily insulated again, the current value between the electrodes abnormally decreases, and a discharge phenomenon (arc) occurs between the electrodes. The part where this arc occurs is indicated by B in the figure. Then, due to the generation of the arc, the electrode 2 and the workpiece 4 are partially welded (short-circuited), and the current value between the electrodes increases abnormally. This becomes C in the diagram.

According to experiments, it has been confirmed that the size of the discharge mark formed on the workpiece 4 is proportional to the amount of electricity B. In addition, Fig. 4 shows the pulse a of the processing pulse to be supplied.
The case where t is 20 m sec is shown, but if the pulse width t is shortened to 5 m 5 ec, for example, Fig. 6 (a) (b)
), and it has been confirmed that an abnormal increase in the inter-electrode voltage and an abnormal decrease in the inter-electrode current value occur at once and an arc occurs.

In this way, although there are slight differences in the waveform shape of the inter-electrode voltage depending on the magnitude of the pulse width t, a phenomenon occurs in which the inter-electrode voltage always increases abnormally immediately before an arc occurs and a short circuit occurs. do. The inventions of this application focus on this phenomenon obtained through experiments and detect an abnormal increase in the voltage between the electrodes, thereby predicting the occurrence of an arc and preventing short circuits between the electrodes. .

Next, regarding the first and second inventions of this application, Sections 7 to 9
This will be explained based on the diagram.

FIG. 7 shows the voltage change discriminator 35, which includes a peak hold circuit 35a, a comparison circuit 35b, a peak pass storage circuit 35c, a cutoff holding circuit 35d, and an offset addition circuit 35e. Consists of etc.

The peak hold circuit 35a includes an amplifier 121 which connects the output side of the electrode-to-electrode voltage detector 34 to the other input side via an analog switch 120, and connects the output side of the amplifier 121 to the other input side via a diode 122 and a resistor 123. It has an amplifier 124 connected to the other input side, and the other input side of the amplifier 121 is grounded via a resistor 125,
One input side is connected to the output side of diode 122.

Further, the other input side of the amplifier 124 is connected to the capacitor 12.
6 to ground, and both ends of this capacitor 126 have
A resistor 127 connected in series and an analog switch 128 are connected, and one input side of the amplifier 124 is connected to its output side.

Further, the comparison circuit 35b includes a comparator 130 in which the output side of the comparator 124 is connected to the other input side via a resistor 129, and one input terminal of the comparator 130 is connected via a resistor 131 to be described later. The output side of the adder 143 is connected to the output side of the adder 143. Further, a resistor 132 is connected to the output side of the comparator 130 and grounded via a diode 133.

The peak passage storage circuit 35c includes a flip-flop (
The output side of the comparator 130 is connected to one trigger terminal of the FF 134 via a resistor 132. The output terminal Q of this FF134 is gate 1
35 to the analog switch 120, and also to one input side of a NAND gate 136 whose other input side is connected to the trigger terminal of the FF 134. Further, the D terminal of the FF 134 is pulled up to the power supply via a resistor 137, the S terminal is grounded, and the R terminal is connected to the pulse generator 38 via a gate H38.

The cutoff holding circuit 35d! , tFF139, and the trigger terminal of this FF139 is connected to the NAND gate 13.
6 is connected, and the other output is connected to one input of the NAND gate 140. In addition, NAND
The other input side of the gate 140 is connected to the pulse generator 38, and its output side is connected via the gate 141 to the gate circuit 36. Reference numeral 142 in the figure is a resistor for pulling up the FF 139 to the power supply.

The offset adder circuit 35e has an adder 143, and the other input side of the adder 143 is connected to the electrode gap voltage detector 34 via a resistor 144, and the resistors 145 to 147 (however, the resistor 146 is connected to the power supply via a variable resistor (one end of which is grounded). Further, one input side of the adder 143 is connected to its output side via a resistor 148, and both are grounded via a resistor 149. In addition,
The analog switch 12B is connected to the gate 138.

Here, the operation of this voltage change discriminator 35 will be explained. First, when a machining command pulse is output from the pulse generator 38, the analog switch 128 and the FF 134.
9 is released from the reset state and enters the set state, the discharge switches 25.1 to 25-n are turned on and machining pulses are supplied, and the gap voltage detection circuit 34 detects the gap voltage. This electrode-to-electrode voltage is calculated by the offset addition circuit 3
The signal is input to the comparator circuit 35b via 5e, and is also input to the peak hold circuit 35a, where its peak value is held.

The inter-electrode voltage increases and reaches a peak value, and the inter-electrode voltage that has passed through the offset addition circuit 35e is transferred to the peak hold circuit 35.
When the value falls below the peak value held by a, the output of the comparator 130 is inverted (L-1()), and an on signal (H) is input to the trigger terminal of the FF 134, and the output of the FF 130 is
4 is turned on, it is stored that the peak of the voltage between electrodes has passed, and the on signal (
H) becomes an off signal (L) by the gate 135, turns off the analog switch 120, and prohibits input from the electrode-to-electrode voltage detector 34 to the peak hold circuit 35a.

If the condition between the machining electrodes is normal and no short circuit occurs, the voltage below the peak value will be detected for a time corresponding to the pulse width of the machining pulse, and after the machining pulse is turned off, the voltage between the machining electrodes will become O If an abnormality occurs between them and the voltage between the electrodes increases and exceeds the peak value, the output of the comparator 130 is inverted (H-)L)
Then, the FF134 is turned off, and the NAND
The output of gate 136 is inverted (L-+H) and FF13
Turn on 9.

By turning on the FF 139, an off signal (L) is input from the output enabled to the NAND gate 140, and the NAND gate 140 is turned on.
The output of the gate 140 is inverted (L) to H. This NA
Due to the ON signal (H) of the ND gate 140, the gate 14
1 outputs an off signal (L), each gate (54-1 to 54-n) of the gate circuit 36 turns off, and the discharge switch 25
-1 to 25-n are turned off to cut off the supply of processing pulses. This off state is maintained until a pulse from the pulse generator 38 is input to the reset terminal of the FF 139.

Note that the gates in this embodiment are not limited to those in the above embodiments, and it goes without saying that any appropriate gate can be used. In addition, each divided circuit is
For example, it can be modified as appropriate, such as by being composed of one part.

Next, an example of an electrolytic finishing method using the voltage change discriminator 35 described above will be described based on the flowchart of FIG. 8.

During finishing, the electrode 2 used when performing die-sinking electrical discharge machining on the workpiece 4 or the remaining material from wire-cut electrical discharge machining is fixed as the electrode 2 to the lower end of the rod 16 of the electrode fixing device 3. After fixing the workpieces 4 to the workpiece fixing device 5 (Sl) and aligning the electrode 2 and the workpiece 4 (S2), data regarding the workpiece 4 and data such as processing conditions are inputted using the input device 13 (S3). .

Then, an electrolytic solution such as sodium nitrate is supplied to the machining tank 15 (S4), and the electrodes 2 are set to a position that maintains the initial electrode gap (S5), and automatic finishing operation is started. A state in which the electrolyte in the gap 17 is stationary (S6) (a state in which the flow and movement of the electrolyte has almost stopped)
Then, a predetermined machining pulse is supplied (S
7) Do. Then, it is determined whether or not the voltage between the machining electrodes increases abnormally while the machining pulse is being supplied (S8).

This determination (S8) is made by the voltage change discriminator 3 based on the voltage between electrodes detected by the electrode voltage detector 34, as described above.
5, and if the voltage between the electrodes increases abnormally, the supply of machining pulses is cut off (S9).

If an abnormal increase in the inter-electrode voltage is not detected while the machining pulse is being supplied, the electrode 2 is raised (SIO) after the machining pulse is turned off, and the gap 1
Supplying a jet of electrolyte from the nozzle 18 to 7 (511)
t, t, machining debris consisting of electrolytic products and the like generated by the supply of machining pulses is removed from the gap 17. Then, the electrode 2 is lowered (S12), and it is determined whether the number of machining times is the number set in the step (S3) or not (S13).
L/, in the case of NO in this judgment (S13), return to the step (S5), and set the electrode 2 again at the position where the initial electrode gap was set, so that the set position of the electrode 2 is always the same. As the machining progresses, the electrode gap becomes larger), and if the determination (S13) is YES, the finishing machining is finished (S14).

In this way, in this embodiment, the abnormal increase in the voltage between the electrodes, which occurs immediately before the arc occurs during the supply of machining pulses, can be suppressed.
The supply of machining pulses is detected when the machining voltage reaches a peak (M V p or more), and the supply of machining pulses is cut off before point B where an arc occurs, as shown in Figure 9. (pulse width 11), a high voltage higher than the peak value Vp is not supplied between the electrodes, and it is possible to prevent a short circuit between the electrode and the workpiece during supply of the machining pulse.

Therefore, in particular, a workpiece machined into a predetermined shape and an electrode having an electrode surface that follows the machined surface of the workpiece are used to supply a relatively large pulse width, for example, a single machining pulse, in an electrolytic solution. When used for electrolytic finishing, which finishes workpieces, expensive workpieces that have been machined into a desired three-dimensional shape will not be burned out due to the supply of processing pulses, and the workpiece can be finished with high precision and in a short time. .

By the way, in the above embodiment, if an abnormal increase in the voltage between the electrodes occurs at two or more locations, as shown in FIG. 4, the supply of machining pulses will be cut off at the first abnormal increase. , An abnormal increase in the voltage between the electrodes is thought to indicate that some kind of abnormal condition has occurred between the electrodes, and there is virtually no problem in cutting off the machining pulse early at the first abnormal rise. In fact, it has been confirmed through experiments that it is safer.

In the above embodiment, the reference value for detecting an abnormal increase in the inter-electrode voltage is set to the peak value Vp, or the reference value is set to Vp±α・VpXβ by setting the resistance constant of each circuit, etc. (However, α and β are predetermined values).

Fig. 10.11 shows an embodiment of the third invention of this application, and its feature is that the bottom value after the peak value of the machining pulse voltage is detected, and the bottom value is The present invention is based on the detection of an abnormal increase in voltage between electrodes. The voltage change discriminator 35 shown in FIG.
The peak hold circuit 35a, the comparison circuit 35b, the peak passing memory circuit 35c, the cutoff holding circuit 35d, and the offset addition circuit 35e (the above circuits have the same configuration as in FIG. 7, so their explanation will be omitted). In addition, it includes a bottom hold circuit 35f, a comparison circuit 35g, and the like.

This bottom hold circuit 35f has an output side of the offset addition circuit 35e connected to the other input side via an analog switch 150. It has a width amplifier 151 and an amplifier 153 whose output side is connected to the other input side via a diode 152.

One input side of amplifier 151 is connected to its output side.

Further, one input side of the amplifier 153 is connected to its output side, and the other input side is connected to a power supply via a capacitor 154. A resistor 155 and an analog switch 156 connected in series are connected to both ends of this capacitor 1540, and the analog switch 156 is connected to the gate 138.

The comparison circuit 35g also includes a comparator 1 in which the output side of the amplifier 153 is connected to one input side via a resistor 157.
The other input side of the comparator 158 is connected to the output side of the offset addition circuit 35e via a resistor 159, and also connected to the output side of the offset addition circuit 35e via a resistor 160. The output side of the comparator 158 is connected to one input side of the NAND gate 136 via a resistor 161, and also connected to one input side of the NAND gate 136 through a resistor 161. is grounded via diode 162. Note that the analog switch 150 of the bottom hold circuit 35f is connected to FF1 of the peak pass storage circuit 35c.
Connect to one output terminal Q of 34. Reference numeral 163 in the figure is a resistor that connects the other input side of the amplifier 151 to a power source.

This voltage change discriminator 35 operates as follows.

That is, the peak hold circuit 35a and the comparison circuit 35b
When the peak value of the inter-electrode voltage is detected and the peak passing is memorized in the peak passing memory circuit 35c, that is, the FF 134 is turned on, the analog switch 150 is turned on by the on signal (H) of the FF 134, and the offset addition is performed. The voltage between electrodes is input from the circuit 35e to the bottom hold circuit 35f. (In this case, the analog switch 120 is turned off and input to the peak hold circuit 35a is prohibited.) Then, the bottom value BO (see FIG. 11) is held in the bottom hold circuit 35f, and this bottom value B
o and the voltage from the offset addition circuit 35e, that is, the voltage between electrodes, are compared in the comparator circuit 35g, and when the voltage between electrodes reaches the bottom value of 80 or more, the output of the comparator 158 is inverted (L
4H) L/, outputs an on signal (H) to the NAND gate 136. The NAND gate 136 receives this on signal (H
) and the output signal (H) of FF134, the output is inverted (L4H)L/, turning on FF139, and the output signal Q (L) is NAND game)140 (L-+H
), gate) 141 (H→L) to the gate circuit 36
outputs an off signal (L) to the discharge switches 25-1 to 25-2.
5-n is turned off. And this off state is FF1
It is held until a reset pulse is supplied to 39. Note that the NAND gate 136 may be configured to be turned on and off only by the output of the comparison circuit 35g.

As described above, in this embodiment, the bottom value BO after the peak value of the inter-electrode voltage is detected, the inter-electrode voltage is compared with this bottom value BO, and the inter-electrode voltage is determined to be equal to or higher than the bottom value of 80. Since the supply of machining pulses is cut off when this occurs, it is possible to detect the rising point of the abnormal rise in the voltage between the electrodes before an arc occurs, and cut off the supply of machining pulses at an earlier point (Fig. 11). The pulse width t2) can prevent burnout of the workpiece. Additionally, even if there is a time delay in the circuit from detecting an abnormality to cutting off the machining pulse, the machining pulse can be shut off before the inter-electrode voltage rises abnormally, ensuring that the workpiece is not burnt out. It can be prevented. This embodiment is effective when the workpiece 4 has a large processing area. In addition. It goes without saying that the reference value in this embodiment can also have a predetermined width with respect to the bottom value Bo, similarly to the second invention.

12 to 14 show an embodiment of the fourth invention of this application, which is characterized by comparing the inter-electrode voltage during supply of machining pulses with the set voltages of the capacitors 23-1 to 23-n, Based on the comparison results, an abnormal increase in the voltage between electrodes is detected. Hereinafter, this will be explained by assigning the same reference numerals to the same parts as in FIGS. 2 and 3.

In FIG. 12, the voltage change discriminator 35 compares the inter-electrode voltage detected by the inter-electrode voltage detector 34 and the output signal from the D/A converter 28, and outputs the result to the gate circuit 36. do. That is, the charging voltage setting device 37 is connected to the capacitor 23.
-1 to 23-〇 charging voltage is set, and the value obtained by D/A converting this set voltage and the voltage between electrodes 34
This method detects an abnormal increase in the voltage between the electrodes by comparing the voltage between the electrodes detected with the voltage between the electrodes.

As shown in FIG. 13, this voltage change discriminator 35 connects the output side of the electrode-to-electrode voltage detector 34 to the other input side of the comparator 170 via a resistor 171.
A resistor 173 whose one end is grounded via a resistor 172 and a resistor 174 whose one end is connected to the D/A converter 28 are connected to one input terminal of the resistor 172 . The output side of this comparator 170 is connected to the trigger terminal of the FF 177 via a resistor 175, and the trigger terminal is grounded via a diode 17B. One output terminal Q of the FF 177 is connected to one input side of each AND gate (54-1 to 54-n) of the gate circuit 36. Note that the D terminal of FF177 is connected to resistor 1.
7B to the power supply, the S terminal is grounded, and the R terminal is connected to the pulse generator 38.

This voltage change discriminator 35 uses a comparator when the voltage detected by the electrode-to-electrode voltage detector 34 exceeds the voltage set by the charging voltage setter 37 and D/A converted by the D/A converter 28. The output of the FF 170 is inverted (L-H) L/ to turn on the FF 177, and outputs an off signal (L) from its output terminal to the gate circuit 36, thereby turning on each AND gate) 54-1 to 5.
4-n is turned off to cut off the supply of processing pulses. This cutoff state is caused by the FF 177.
It is held until a reset pulse is input to the R terminal.

As described above, in this embodiment, the voltage between the electrodes and the set voltage Vt of the capacitors 23-1 to 23-n are compared, and when the voltage between the electrodes is equal to or higher than the set voltage Vt, the discharge switches 25-1 to 25-n are activated.
25-n to cut off the supply of charge from the capacitors 23-1 to 23-n (see Fig. 14), a high voltage higher than the set voltage Vt of the capacitors 23-1 to 23-0 is applied between the electrodes. It is possible to detect an abnormal voltage rise phenomenon that occurs immediately before an arc occurs, and to prevent the occurrence of short circuits. Moreover, the voltage change discriminator 35 can utilize the output signal of the charging voltage setter 37 that sets the charging voltage of the capacitors 23-1 to 23-n, and the circuit configuration can be simplified.

It should be noted that the means for detecting an abnormal increase in voltage between electrodes in the present invention is not limited to the configuration of the voltage change discriminator of each of the above embodiments, but may be used in combination with each embodiment, or may be used to detect an abnormal increase in voltage between electrodes. Any other suitable classifier that can detect . In addition, in the above embodiment, short circuit prediction was performed by detecting only the phenomenon of abnormal increase in the voltage between electrodes, but for example, the phenomenon of abnormal decrease in the current value between electrodes that occurs in combination with the phenomenon of abnormal increase in voltage between electrodes is detected. Also detected, these 2
If two phenomena occur simultaneously, the supply of machining pulses may be cut off to predict the occurrence of an arc. Furthermore, the flowchart shown in FIG. 8 is also an example, and it goes without saying that it can be applied to other electrolytic finishing, electrolytic die engraving, and the like.

[Effects of the Invention] Since each of the inventions according to this application is configured as described above, it produces the effects described below.

(First invention) Since the phenomenon of abnormal increase in the voltage between machining electrodes during the supply of machining pulses is detected and the supply of machining pulses is cut off, it is possible to predict the occurrence of an arc, which is a sign of a short circuit. It is possible to prevent short circuits and prevent burnout of the workpiece due to short circuits.

Therefore, especially when used for electrolytic finishing, the workpiece can be finished with high accuracy in a short time without burning out an expensive workpiece machined into a desired three-dimensional shape.

(Second invention) In order to detect an abnormal increase in the voltage between machining points by comparing the voltage between the machining electrodes to be detected and its peak value, for example, the supply of machining pulses is cut off immediately before the voltage between machining electrodes exceeds the peak value. Therefore, arc occurrence can be predicted at an early stage, and short circuits due to arc occurrence can be prevented.

(Third invention) To detect an abnormal increase in voltage at an earlier point in time by comparing the inter-electrode voltage and the bottom value of the inter-electrode voltage after the peak value to detect an abnormal increase in the inter-electrode voltage. Even if the workpiece has a large processing area, it is possible to reliably predict arc occurrence and prevent workpiece burnout due to short circuits.

(Fourth invention) The inter-electrode voltage is compared with a set voltage for setting the charging voltage of the capacitor, and for example, when the inter-electrode voltage is higher than the set voltage, it is detected as an abnormal rise phenomenon and the supply of charge from the capacitor is cut off. Therefore, with a simple configuration, a voltage higher than a set voltage is not supplied between the poles, the occurrence of an arc can be predicted, and burnout of the workpiece due to short circuit can be prevented.

[Brief explanation of drawings]

Fig. 1 is a schematic configuration diagram of an electrolytic finishing processing apparatus that can implement each invention of this application, Fig. 2 is a block diagram of the main parts, Fig. 3 is a circuit diagram of the main parts, and Fig. 4 is a schematic diagram of the electrolytic finishing processing equipment that can implement each invention of this application. A waveform diagram for explaining the basic principle of the invention, FIG. 5 is an equivalent circuit diagram, FIG. 6 is a waveform diagram similar to FIG. 4 showing another example, and FIG. and a circuit diagram of a voltage change discriminator showing an embodiment of the second invention, FIG. 8 is a flowchart showing an example of the finishing method of the invention, FIG. 9 is a timing chart thereof, and FIG. 11 is a timing chart of the same invention, and FIG. 12 is a main block diagram of an electrolytic finishing apparatus showing an embodiment of the fourth invention of this application. 13 is a circuit diagram of a voltage change discriminator according to the invention, and FIG. 14 is a timing chart thereof. 1... Electrolytic finishing processing device, 2... Electrode, 4...
Workpiece, 8... Power supply device, 9... Head drive control section, IO... Processing condition control section 11...
Electrolyte flow control unit, 12...control device, 34...electrode voltage detector, 35...voltage change discriminator 35a...
・Peak hold circuit, 35b...comparison circuit 35f・
...bottom hold circuit, 36...gate circuit 37.
...Charging voltage setting device, 40...CPtJ. Figure 7 Figure 4 Figure 5 Figure 6 73rd prisoner Figure 14 Procedure amendment April 70, 1990

Claims (4)

[Claims] (1) A. In a device for electrolytically machining a workpiece by supplying a machining pulse between the electrodes and the workpiece, which are disposed opposite to each other with a predetermined gap in an electrolytic solution, b. A short circuit prediction method in electrolytic machining, comprising: detecting an abnormal rise phenomenon; and c) cutting off the supply of the machining pulse based on this detection. (2) In the short circuit prediction method according to claim 1, the step of detecting the phenomenon of abnormal increase in the voltage between the machining electrodes comprises: a. detecting the voltage between the machining electrodes while the machining pulses are being supplied; and b. A method for predicting short circuits in electrolytic machining, comprising: detecting a peak value of a voltage between electrodes immediately after the start of supply; c. comparing the peak value with the voltage between electrodes. (3) In the short circuit prediction method according to claim 1, the step of detecting the phenomenon of an abnormal increase in the voltage between the electrodes comprises: a. detecting the voltage between the electrodes while the machining pulse is being supplied; and b. this voltage between the electrodes. A method for predicting short circuits in electrolytic machining, comprising: detecting a bottom value after a peak value; c. comparing this bottom value with the voltage between electrodes. (4) A. Electrolytic machining of a workpiece by supplying machining pulses caused by discharge of electric charge of a capacitor between the electrodes and the workpiece, which are disposed opposite to each other at a predetermined gap in an electrolytic solution, B. Charging of the capacitor a step of setting a voltage, c. a step of detecting the inter-electrode voltage during the supply of the machining pulse, and d. comparing the inter-electrode voltage with the set voltage of the capacitor;
A method for predicting short circuits in electrolytic machining, comprising: cutting off the supply of machining pulses based on the comparison result;