JPS63185520A - Electric discharge machining control device - Google Patents

Abstract

PURPOSE:To aim at preventing concentrated electrical discharge by providing AE sensors on an electrode and a workpiece to measure the position of electrical discharge at predetermined time intervals on a real time base during electrical discharge machining so as to monitor whether or not the electrical discharge is carried out at one and the same position or in the vicinity thereof. CONSTITUTION:Signals from SE sensors S1, S2, S3 are led to the corresponding logic elements f1, f2, f3, respectively, through a circuit composed of an amplifier (a), a diode (b), a battery (c), a comparator (d), a diode (e) and the like. These three logic elements pass clock signal therethrough and delivers these to an AE signal arrival time measuring counter i1, i2, i3 until the AE signals arrives. In this arrangement, one set of data per predetermined machining time is extracted and is delivered to a computer. Further, when the computer determines that the electric discharge is carried out at one and the same position or in the vicinity thereof, the computer at once controls the electrical discharge so that the position of the electric discharge is displaced, thereby it is possible to prevent concentrated electric discharge.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applicable to electrical discharge machining, in which a voltage is applied between an electrode and a workpiece to produce a discharge, and the workpiece is machined in a concentrated manner at a specific location. The present invention relates to an electric discharge machining control device for preventing electric discharge from occurring.

[Conventional technology]

In electric discharge machining, it is known that when a so-called concentrated electric discharge occurs, in which the electric discharge is concentrated at a specific location, it causes various adverse effects on the electric discharge machining. For example, in die-sinking electrical discharge machining, the heat-affected layer of the workpiece becomes thicker or the surface roughness becomes rougher, making it impossible to guarantee the quality and machining accuracy of the machined surface. In some cases, this can even lead to continuous arcing, which can even thermally damage the workpiece. Furthermore, in wire electrical discharge machining, the wire may break, making it impossible to continue machining.

If the wires are reconnected and reprocessed, it will be difficult to automate the process.

Therefore, conventional measures have been taken to prevent the occurrence of concentrated discharge by observing the voltage and current waveforms between the electrode and the workpiece.

[Problem that the invention seeks to solve]

However, since the above-mentioned conventional technology performs control after detecting the occurrence of concentrated discharge, when controlling to stop concentrated discharge, when viewed from the viewpoint of machining accuracy or machining quality, The problem was that it was already too late.

In other words, once a concentrated discharge occurs, the condition between the electrodes in that area becomes poor, and the quality of the surface machined under this condition is extremely difficult to recover, even if the concentrated discharge is subsequently removed. It was difficult. Furthermore, in wire electrical discharge machining, wires often break due to concentrated electrical discharge. This means that the wire, which is an important means of control, is lost before the concentrated discharge can be detected or not.

Therefore, sufficient effects could not be obtained by controlling the concentrated discharge after it occurred.

The present invention aims to solve the above problems.

[Means for solving problems]

In order to solve the above-mentioned problems, the basic idea of the present invention is to detect when a concentrated discharge is about to occur and perform control to prevent concentrated discharge at that point, rather than after the concentrated discharge has occurred. I took it. To this end, we decided to measure the discharge position in real time at regular intervals during electrical discharge machining to monitor whether discharge was occurring repeatedly at or near the same position. In order to measure the discharge position, AE (Acoustic Em
A that detects ultrasonic signals called ission) signals.
A plurality of E-sensors were provided on the electrode, the workpiece, or both. Then, the discharge position was determined based on the time from the start of discharge to the time when the AB signal reached each AE sensor. As a control means for eliminating concentrated discharge, the previously used control means described above was used.

Therefore, specifically, in the electrical discharge machining control device of the present invention,
a plurality of AE sensors provided on the workpiece or the electrode or both; means for interrupting the electrical discharge machining state by setting a continuous machining period that is a period during which the electrical discharge pulse voltage is continuously applied; Means for starting the next continuous machining period after waiting for the AE flaw signal to disappear after the end of the machining period, and measuring the time from the first discharge start point to the time when the AB signal reaches each AE sensor after entering the continuous machining period. A to do
E signal arrival time measuring means; and means for controlling machining conditions so as to move the discharge position when the measured value obtained by the AE signal arrival time measuring means is within a predetermined range centered on the previous measured value. We decided to have

〔Example〕

FIG. 1 is a diagram showing the mounting location of an AE sensor in an embodiment of the present invention. In Figure 1, l is a DC power supply, m
is a protection resistor, n is a switching transistor, sl
Is S the AE sensor and A the radiation? i1 location, p is the processing electrode, and q is the workpiece.

The AE sensor may be attached only to the processing electrode p or the workpiece q, or may be attached to both of them. However, in order to specify the discharge position, it is necessary to install a plurality of them. From discharge point A, each AE sensor SI+
S! , the distance to 33 is 'l='! +r3, the time it takes for the AC signal emitted at the discharge point A to reach each AE sensor corresponds to the distance. A signal detected by the AE sensor is sent to a control circuit via a coaxial cable.

FIG. 2 shows its control circuit. In Figure 2, a is an amplifier, b is a diode, C is a battery, d is a comparator, e is a diode, f to r4 are logic elements, g+,
gz is a flip-flop, h is a latch circuit, 10 is a counter for measuring continuous processing period, 11 to i
3 is a counter for measuring the arrival time of the AE signal, j is a logic element, l is a DC power supply, m is a protection resistor, n is a switching transistor, and U is a discharge start detection circuit.

FIG. 3 is a diagram showing waveforms at various locations in FIG.
The circled numbers in the figure correspond to the numbers in FIG. 3.

The operation in FIG. 2 is as follows. The signals from each AE sensor sent from FIG. 1 are sent from amplifier a, diode b, battery C, and comparator d.

The signals are guided to corresponding logic elements f1 to r, respectively, through an amplification/shaping circuit composed of a diode e and the like. on the other hand,
When a voltage is applied from the direct type R1 through the protective resistor m and the switching transistor n and discharge starts, the discharge start detection circuit U detects this and the flip-flop g
1 gives a signal to start discharging. In response to the signal, the logic elements r, to r, pass the clock until they receive a signal indicating that the AE wave has arrived, and input it to the corresponding AE signal arrival time measuring counters 11 to i.

The distance from each AB sensor S1 to S to the discharge point can be known from the count numbers of the AE signal arrival time measurement counters i, to i3. However, this is the first discharge point after the start of electrical discharge machining. Although the discharges occur one after another, it is not possible to measure the discharge points from the second discharge onwards. This is because once the AE wave from the first discharge is generated, its reverberation remains for a while, so the AE wave from the second discharge
It is difficult to know when the E wave reaches the AE sensor (because it happens).Therefore, the continuous machining period, which is the period during which the discharge pulse voltage is continuously applied, is set to a constant value, and the When the time has passed, discharging is stopped and all A
The discharge is restarted once the residual effects of the E waves are gone.

Reference numeral 10 denotes a continuous machining period measuring counter that measures the elapse of a certain continuous machining period. The logic element r4 is for notifying that the reverberation of AE waves has disappeared in all AE sensors. When the AE waves reach all the AE sensors, data regarding all the distances r1 to r to be measured have been taken into the AE signal arrival time measurement counters 11 to i3. Therefore,
The logic element k detects that the AE waves have reached all the AE sensors, and the latch circuit latches the measurement data to ~h. As described above, one set of data is collected for each fixed machining time described above.

The collected data is sent to the convenience store, for example,
Processing is performed according to the procedure shown in FIG.

FIG. 4 is a diagram showing an example of a procedure for processing measured data by a computer. In a computer, the average processing value of data measured several times (for example, n times) is calculated,
It is compared with the previous averaged value to determine whether discharge is occurring at or near the same position. In the following description of FIG. 4, the numbers ``■'' to ``■'' correspond to processes ``■'' to ``■'' shown in FIG.

■ Input the data 9 times.

(2) Average processing is performed for each data of each AE sensor S1 to s3, and average processing values A, B, and C are obtained.

■ The above A, B, and C are the previous averaging processing values P.

Check whether it is in the vicinity of Q and R.

■ If it is in the vicinity, it is judged to be a sign of concentrated discharge, so take control measures to avoid it (for example, control of electrode position, control of input electrical conditions, control of machining fluid injection, etc.) .

■ If they are not in the nearby range, replace P, Q, and R with new averaged values A, B, and C.

In addition, in the process shown in FIG. 4, the data that has been measured and averaged multiple times (n times) is compared with the previously averaged data, but data from one measurement is compared. It can also be used as a thing.

〔Effect of the invention〕

As described above, according to the present invention, the discharge position is measured in real time, and when a discharge occurs at or near the same position, the discharge position is controlled to be immediately moved, thereby preventing concentrated discharge from occurring. It is now possible to prevent it.

[Brief explanation of the drawing]

Fig. 1: A diagram showing the mounting location of the AE sensor in an embodiment of the present invention. Fig. 2: A control circuit in an embodiment of the present invention. Fig. 3.
...Waveform diagram of each part of the control circuit in Fig. 2. Fig. 4... In the diagram showing the processing procedure of measurement data, A is a discharge point,
a is an amplifier, b is a diode, C is a battery, d is a comparator, e is a diode, fl to f4 are logic elements, g
++g2 is a flip-flop, hl is a latch circuit, 10 is a counter for measuring continuous processing period, 11 to i is a counter for measuring AE signal arrival time, ``,'' is a logic element, ■ is a DC power supply, m is a A protective resistor, n is a switching transistor, p is a processing electrode, q is a workpiece, and U is a discharge start detection circuit. Patent applicant Muto - Husband (1 other person) Representative patent attorney
Mori 1) Hiroshi (3 others)! 4 flash

Claims (1)

[Claims] In an electrical discharge machining control device that applies a discharge pulse voltage between an electrode and a workpiece to cause discharge and machine the workpiece while controlling machining conditions, a plurality of AE sensors provided on the workpiece, the electrode, or both are used. and means for interrupting the electrical discharge machining state by setting a continuous machining period which is a period during which the electrical discharge pulse voltage is continuously applied; means for starting a continuous machining period; AE signal arrival time measuring means for measuring the time from the first discharge start point in the continuous machining period to the time point at which the AB signal reaches each AE sensor; An electrical discharge machining control device comprising: means for controlling machining conditions such that a discharge position is moved when a measured value obtained by the time measuring means is within a predetermined range centered on the previous measured value.