JPS61182722A - Electric discharge machine - Google Patents

Abstract

PURPOSE:To make it possible to perform the electric discharge machining of such planned performances as feed speed, machining accuracy, etc. by providing a control unit for detecting the state of electric discharge at a machining space and cancelling the starting of an ON-state time while it remains non-loaded. CONSTITUTION:A control unit is provided to detect and judge the state of electric discharge at a machining space 23 and cancel the starting of the ON- state time of an ON-state time setting circuit 9 while it remains non loaded without generation of electric discharge. And because the ON-state time setting circuit 9 works and outputs an ON-time signal after starting of the electric discharge at the machining space 23 by controlling the control circuit, the electric discharge almost accords with the gate pulse output from a pulse generation circuit, and the electric discharge of a specified ON-pulse width and that of OFF-pulse width come into being repeated by turns. This constitution has such effect that the electrical discharge of such planned performances as a specified feed speed, roughness of workface, enlarged machining allowance, machining accuracy, electrode consumption rate, etc. can be performed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an electrical discharge machining apparatus, and particularly to an improvement in a machining pulse generating power source.

[Prior art and problems]

Conventionally, pulse generation circuits that use capacitor charging/discharging or multi-by-break circuits have been used, but these require individual resistors, capacitors, etc. to change the pulse width, rest width, two frequencies, etc. according to the purpose. It was necessary to make complex switching adjustments, and there was a limit to the range of changes, making it impossible to generate desired pulses. Furthermore, even if the pulse width, pause width, etc. are set to a predetermined value according to the purpose, depending on the state of the machining gap, the output pulse of the pulse generation circuit and the machining gap may not match, making it impossible to perform electrical discharge machining with the planned performance. There were drawbacks. In addition, it is not possible to adaptively control the constantly changing gap conditions, and abnormal discharges such as gas discharges and arc discharges continue, deteriorating the machined surface, or the machining fluid cannot be jetted or deepens due to continued abnormal discharges. When machining, there was a drawback that the machining stopped completely.

[Means for solving problems]

The present invention was invented to improve this point, and the clock pulses generated by the clock pulse generation circuit are added to a time setting circuit constituted by a counter and a count number switching setting device, and the clock pulses are alternately transmitted from the time setting circuit. A gate pulse having a corresponding on-pulse width and off-pulse width is generated based on the output on-time signal and off-time signal, and the generated pulse is applied to an electronic switch to turn on and off a power supply connected in parallel to the machining gap, thereby performing the machining. In the device which supplies gap repetition machining pulses, the discharge state of the machining gap is detected and the on-time time starting operation of the on-time time setting circuit is performed during a no-load state in which no discharge occurs. Stop I
It is characterized by having 11 circuits.

〔Example〕

To explain the following with reference to one embodiment of the drawings, in FIG. 1, 1 is an oscillation circuit that generates clock pulses, and as shown in FIG. C and various other types can be used. 2 is a time setting circuit that sets an off time by counting clock pulses with a counter; the clock pulses from the oscillation circuit 1 are first input to a counter connected in series;
Counting is performed in addition to 4. Reference numeral 5 denotes a relay that selects the count number to a desired value, and this selection output is applied to a decade counter 6 and converted into a BCD signal, which is converted into a decimal signal by a decoder 1.

8 is an output selection relay of the decoder 7. Reference numeral 9 denotes a time setting circuit for setting the on time, which is also operated by a counter 10° 11, a selection relay 12 for the number of counts, a decade counter 13, a decoder 14, and an output selection relay 15, similar to the off time time setting circuit. It is configured.

16 is a counting circuit for counting the number of output pulses from the time setting circuit 2, which is composed of two counters 17 and 18, and outputs an output signal every time a predetermined number is counted. Reference numeral 19 generates gate pulses having on-pulse widths and off-time widths corresponding to the on-time signal and the off-time signal, which are alternately output from the time setting circuit 9 for setting the on-time and the time setting circuit 2h1 for setting the off-time. With the pulse generation circuit, NAN
D+ and NAND2 constitute a 7 lip-flop circuit. , 20 is a gate pulse phase inversion amplifier, 2
Reference numeral 1 designates a transistor as a switching element which repeatedly generates machining pulses and applies them to the machining gap 23 by switching the voltage source 22 on and off in response to gate pulses. 24
is a detection control circuit that detects the discharge state of the machining gap, that is, for example, the gap voltage, generates an inversely proportional voltage by comparing it with, for example, a reference voltage, and controls the output voltage by adding it to the clock pulse oscillation circuit 1. , 25 is an on-pulse clamp circuit that detects and discriminates the no-load voltage that does not cause discharge in the machining gap and clamps the on-pulse, and 26 is a reference value that discriminates the detection signal voltage of the machining gap using a reference value that sets the lower limit of normal discharge. This is a discrimination circuit that outputs a signal when the following conditions occur.

In the above, a clock pulse is generated by the operation of the oscillation circuit 1. This clock pulse is the basis for determining the on-time and off-time of the gate pulse. First, this clock pulse is added to the counter 3 of the time setting circuit 2 that sets the off time and counted. If this output is selected as B by the relay 5, a pulse is output every two clock pulses, and the counter If terminal A of 4 is selected, the frequency is divided so that every 8 clock pulses are output. This frequency-divided signal is then sent to the decade counter 6.
A BCD signal corresponding to the count is output. This BCD signal is converted into a decimal signal by a decoder 7, which is switched and selected by a relay 8. For example, counter 3
If you select °゛2'' as the output of 81 decoder 7, the output of decoder 7 will be twice the output of counter 3, so one pulse will be output for every 2X2=4 clock pulses.
If the output of counter 4 and decoder 6 are selected, one off-time signal pulse will be output every time 8x8x6=384 clock pulses are input.This output signal is "0". is output when the selected count is reached by counting from the end of the previous discharge, and this count time is the off time.In other words, after the discharge is completed, the output side of the decoder 7 is kept at 1". 11111 to NAND4, and signal 11 from the other side.
If 1+1 is added, the output of NAND4 is (L 0
11, the output of NANOa is 1'', the output of NAND2 of the flip-flop is '0', and NANDl is '1', which is inverted by the phase inversion amplifier circuit 20 and a '0° signal is applied to the transistor 21 to keep it in the off state. However, when the output of the decoder 7 becomes II O12 upon completion of a predetermined count, this output "0" is added to NANOa, and if the signal "1°" is added from the other side, this output is 1" and NANOa.
The output of NOa is “0”, the output of NAND2 is “+1+t,
Also, since 1" is applied to NANOa from the other side, the output becomes "0", and this gate pulse is inverted and amplified by the circuit 20 and applied to the transistor 21, turning on the switch.

While the time setting circuit 2 that sets this off time is counting, the output 1101+ of N A N D 2 is added to AND3, so the time setting circuit 9 that sets the on time does not count, but as described above, the off time When the time is completed, the switch 21 is turned on to start discharging and N A
When the output of N D z becomes 1'', 0111 is sent to AND3.
is added, so a clock pulse from the oscillator 1 is added from one side, and the on-time vF is set by the off-time signal output from the time setting circuit 2 that sets the on-time.
It constitutes a control circuit that causes the I2!1 setting circuit 9 to start counting to start fm. Of course, instead of the synchronization signal of the flip-flop NAND2, the off-time signal output from the decoder 7 may be directly applied to the AND3.

Thus, counting of circuit 9 is started, but counter 10
．． 11.13. The operations of the decoder 14 and the like are the same as those of the time setting circuit 2 that sets the previous off time, and by selecting the relay 12.15, any pulse can be used from rough machining with a long pulse width to finishing machining with a short pulse width. Can generate wide on-time. When this on-time is completed, the decoder 14 outputs an on-time signal that becomes "O", and this is added to AND+, making the output "0", so the flip 70 knob is inverted and NAND is applied.
The + output is inverted to 1'', and the inverted 0'' output pulse is applied to the transistor 21 by the phase inversion amplifier circuit 20, and the transistor 21 is switched off, completing the discharge of one pulse. The output of the decoder 14 is inverted by each NANDs~8, and a signal "1" is applied to the clear terminal of each counter to clear it.
3 receives the 1101+ signal from NAND2, so the gate closes and circuit 9 does not count clock pulses, but circuit 2 cleared by NAND7
starts counting. That is, this NAND 7 constitutes a control circuit that causes the time setting circuit 2 to start counting so as to start the off time based on the on time signal output from the time setting circuit 9 that sets the on time. Of course, the flip-flop NANOa synchronizes with the on-time signal.
The counter may be cleared using the output of the off-time signal, which is similar to the case where the synchronization signal of the off-time signal is added to AND3.

In this way, the time setting circuit 2 for setting the off time operates again, and when the set count is completed in the same way, the time setting circuit 9 for setting the on time starts counting.
As if an on-pulse signal is output at the set count number,
This is repeated, and the time setting circuits 9 and 2 output the on-time signal and the off-time signal alternately, and the circuit 19 outputs the on-time signal.

A gate pulse having an on-pulse width and an off-pulse width corresponding to the off-time signal is generated and applied from the circuit 20 to the switch transistor 21, and a machining pulse is supplied to the gap 23 by on/off switching.

Incidentally, the time setting circuit 9 for setting the on-time can also clear a counter using the off-time signal output from the time setting circuit 2 for setting the off-time, and start counting for on-time shaping.

Further, the time setting circuit 2 for setting the off-time may also have a counter cleared in advance in the same way as the time setting circuit 9 for setting the on-time so that it can be started by the on-time signal or synchronization signal output from the circuit 9. can.

As described above, the gate pulse is generated and the switch is turned on and off to supply the machining pulse to the machining gap, but when a no-load state occurs where no discharge occurs, the control is performed as follows. The on-pulse clamp circuit 25, that is, this clamp circuit is made of a discriminator Schmitt or the like, outputs "1" when the voltage of the machining gap 23 is a no-load voltage higher than the discharge voltage, and sets the on-time. Since the counters 10 and 11 of the setting circuit 9 are cleared and held, even if the switch 21 is turned on when the time setting circuit 2 for setting the off time completes the count, the gap 23 is too wide and the discharge does not start. In this case, counting is not performed by the time setting circuit 9 that sets the on-time.When a discharge occurs in the gap, the output of the circuit 25 becomes °'0'' and counting is performed after the discharge has definitely started.
The discharge due to the on-pulse width set by the time setting circuit 9 that sets the on-time can be made almost constant.

If the machining voltage becomes lower than the set reference value due to some reason in the machining gap, the discrimination circuit 26 determines this and changes the output 11111 so far to 1''→
Change to “0”. Then, the output of gate AND1 is set to “O”.
and keep the output of AND2 at O'', switch 21
is kept off to interrupt the electrical discharge machining, and the machining is completely stopped until the machining gap is returned to normal by servo control of the machining gap or purification of the jet machining fluid.

That is, this discrimination circuit 26 can be combined with gates AND+, AND2, etc. to constitute an interruption control circuit that interrupts the generation of gate pulses from the pulse generation circuit 19 when the state of the machining gap is out of the normal range. prevent the deterioration of

The circuit 16 adds the number of discharges according to the number of operations of the time setting circuit 2 which sets the off time, and when it reaches a certain set value, the discharge is forcibly interrupted temporarily, or the machining gap 23 is widened by raising the electrode. This is to remove and purify processing debris that accumulates in the gaps.

As described above, the clock pulses generated by the oscillation circuit 1 are counted by the time setting circuit 2 for setting the off time and the time setting circuit 9 for setting the on time, thereby generating the on time and off time signals according to the set count number. Then, the pulse generation circuit generates a gate pulse with an on-pulse width and an off-pulse width corresponding to the signal, and this is added to the on/off switch for generating machining pulses, so the pulse width can be changed from rough machining with a long pulse width to The desired machining pulse can be generated arbitrarily over a very wide range up to short finishing machining.

However, once these on-pulses and off-pulses are set by the switching relay, a constant pulse will always be supplied to the gap, but the circuit 24 detects the discharge state of the gap 23 and oscillates with this output. By controlling the circuit 1, the gate pulse can be adaptively controlled by changing the clock pulse, which is the basis for setting the on-pulse and the off-pulse, in a gap state.

That is, the detection circuit 24 detects, for example, the average voltage of the machining gap and compares this detected value with a reference value to generate an inversely proportional voltage. By applying this voltage to the oscillation circuit 1, which is configured as shown in FIG. 2, the oscillation output (o) is proportional to the input (in) voltage.
When the frequency r of ut) changes as shown in Figure 3a, and therefore the machining gap widens and the gap voltage rises, circuit 2
Since the low voltage inverted by 4 is applied to the oscillation circuit 1, the oscillation frequency r of the oscillation circuit with respect to the gap voltage
decreases in inverse proportion as shown in Figure 3.

In this way, when the frequency of the output clock pulse of the oscillation circuit 1 decreases, the on and off pulse widths set by the time setting circuit 9 that sets the on time and the time setting circuit 2 that sets the off time have an equal number of counts. Therefore, when the machining gap widens, a discharge with a proportionally large pulse width occurs. Conversely, when the gap narrows, the gap detection voltage decreases,
As shown in FIG. 3, since the frequency of the clock pulse of the oscillation circuit 1 increases, the on and off pulse widths set by the time setting circuit 9 for setting the on time and the time setting circuit 2 for setting the off time become shorter. Therefore, a discharge with a small pulse width is generated in a narrow gap. In this way, by controlling the clock pulse oscillation frequency of the oscillation circuit 1 according to changes in the machining gap, the machining pulse can be easily controlled.When the machining gap is wide, a large discharge with a long pulse width is performed, and when the machining gap is narrow, a large discharge is performed. By generating a small electric discharge with a short width, it is possible to constantly generate an adaptive electric discharge according to changes in the state of the gap, and stable and highly accurate electric discharge machining can be performed.

Although the case where one clock pulse oscillation circuit 1 is provided has been described above, it is also possible to separately provide a time setting circuit 9 for setting the on-time and a time setting circuit 2 for setting the off-time. Also, if one of them is a fixed oscillator and the other is controlled to change according to the state of the machining gap as described above, it is possible to make only the on-pulse or off-pulse adaptive and the other one with a constant pulse width. On-pulse and off-pulse duty can be controlled.

〔Effect of the invention〕

As described above, the present invention provides a counter that counts clock pulses to set on-time and off-time, and a switching device that switches and sets the count number of the power counter for independently setting on-time and off-time. Two separate time setting circuits are provided for on time and off time, and the off time (or on time) is determined by the on time (or off time) signal output from the time setting circuit.
A control circuit performs related control to start alternating operation of the two separately provided time setting circuits so as to start the time of , and outputs an on-time signal and an off-time signal alternately from the operating time setting circuit, In addition to the pulse generation circuit, a gate pulse having an on-pulse width and an off-pulse width corresponding to the above-mentioned both signals is generated to turn on the power switch;
Since the machining pulse is supplied to the machining gap by turning it off, it is possible to generate any pulse over a wide range from rough machining to finishing machining by selecting and switching the count number of the counter in the time setting circuit. Moreover, since the time setting circuit is provided with a switching device that switches and sets the count number of the counter to arbitrarily set the on time and off time independently of each other, the on pulse width and the off pulse width can be independently set. Change control is possible, and by simply changing the count number of the counter, you can easily set only the on-pulse or only the off-pulse to the desired pulse width without changing anything else. The most suitable pulse can be easily generated according to the machining conditions, and the electronic switch is reliably turned on and off by the output gate pulse of the pulse generation circuit consisting of 70 flips, resulting in stable machining. I can do it.

It should be noted that counters constituting the time setting circuit and devices for switching and setting the count number other than those in the embodiments can be similarly used, and the combination circuit of the counter and switching device is not limited to the circuit in the embodiments.

In the embodiment, since a switching device is used which switches and sets the count number of the counter by switching operation in decimal notation, the switching can be extremely easily changed and arbitrary pulses can be generated.

The present invention provides control by providing a control circuit that detects and discriminates the discharge state of the machining gap and stops the start operation of the on-time time of the on-time time setting circuit during a no-load state in which no discharge occurs. According to 1. On time
The II setting circuit operates after the discharge starts in the machining gap and outputs an on-time signal, so the gate pulse output from the pulse generation circuit and the discharge almost match, there are no pulses that do not discharge, and the pulse width of each discharge is reduced. becomes equal, and discharges with a predetermined on-pulse width and off-pulse width are repeated alternately, and from this, the predetermined machining speed, machined surface roughness,
This has the effect of allowing electric discharge machining to be performed with the planned performance in terms of machining expansion allowance, machining accuracy, electrode consumption ratio, etc.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of an embodiment of the present invention, and FIG. 2a is a circuit diagram of an embodiment of the present invention. 3b and 3c are partial specific circuit diagrams, and FIGS. 3a and 3b are diagrams illustrating its operation. 1...Oscillator circuit 2.9...Time setting circuit 3, 4. 6
．． 10.11.13...Counter 5,
8.12.15......Switching relay 7.14
......7':]-taAND1. AND2
, AND3......AND gate NAND3, NANO4, NANDs. NAND? ...... Nantes Gate 19...
・・・・・・Flip-flop 20・・・・・・・・・
Phase inversion amplifier 21... Switch element 22... Voltage source 23... Machining gap 25... On Pulse clamp circuit 26・
...Discrimination circuit patent applicant: Kiyoshi Inoue, representative of Inoue Japax Institute Co., Ltd., ~5, Shi/

Claims (1)

[Claims] An oscillation circuit that generates clock pulses, a counter that counts clock pulses generated by the oscillation circuit and sets on-time and off-time, and a count number of the counter for independently setting on-time and off-time. Two time setting circuits are provided for on-time and off-time, each consisting of a switching device for switching and setting, and the on-time (or off-time) is output from the time setting circuit.
A control circuit that starts the alternating operation of the two separately provided time setting circuits so as to start the off time (or on time) according to a signal, and alternately outputs from the time setting circuit that operates under the control of the control circuit. A generating circuit consisting of a flip-flop that generates a gate pulse having an on-pulse width and an off-pulse width corresponding to an on-time signal and an off-time signal, and a voltage source connected in parallel to the machining gap is turned on by the gate pulse generated by the pulse generating circuit.・In an electric discharge machining apparatus which is provided with an electronic switch for off-switching and repeatedly supplies machining pulses to the machining gap by switching on and off a voltage source by the electronic switch, the electric discharge state of the machining gap can be controlled. An electric discharge machining apparatus characterized in that a control circuit is provided that detects and discriminates and stops the on-time start operation of the on-time time setting circuit while the no-load state is in which no electric discharge occurs.