JPS62287917A - Electric discharge machinine - Google Patents

Abstract

PURPOSE:To make it possible to discriminate the interpole condition without lowering the rate of machining, by superposing high frequency alternate voltage during the quiescent time of pulse voltage applied to the interpole gap so that the degree of insulation of insulative machining fluid is detected in accordance with the leakage current across the interpole gap. CONSTITUTION:A control instruction signal generating device 17 superposes high frequency alternate voltage from an electrical sources 18 during a deionizing period or the quiescent time of pulse voltage applied between a wire electrode 2 and a workpiece 1 from a machining power source 15, and a current detector 6 detects interpole leakage current running due to the lowering of insulation of the machining fluid 3 which is caused by machined chips. Thus detected current value is delivered to a detecting circuit 119 through an amplifier 117 and a switch 118 which is turned on during the quiescent time. An output power SE obtained through envelope detection is compared with preset reference values V1, V2 by comparators 120, 121, and the degree of insulation is determined by means of an AND gate 22 to perform predetermined control. Thus, it is possible to appropriately discriminate whether the condition of machining is satisfactory or not without lowering the rate of machining, thereby it is possible to prevent accidents due to breakage of the wire electrode.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention [Industrial Applications] This invention generates electrical discharge between an electrode and a workpiece, and cuts the workpiece with this emitted energy/region. 1 to do double work! This relates to infant care equipment.

[Conventional technology]

Conventionally, this type of electrical discharge machining equipment has two types: one that drills a hole in a workpiece with a rod-shaped electrode, and the other that drills a hole in the workpiece using a drill or the like and passes the wire 7:i through it. There is a method in which the workpiece is cut by moving the wire electrode relatively.The following describes the outline of this one-shift machine, and the electric discharge machining using wire electric shock is shown in Figure 6. This will be explained using a device as an example.

In the 6th cause, (1) is the workpiece, and the cut hole [1]
wires passed through? + P-image liquid (3) between the silkworm (2)
) by supplying it.

The above-mentioned insulating liquid (3), hereinafter referred to as "nako liquid", is pumped from the tank (4) to the pump (5) to the workpiece (1) and the wire! fffl gap of lt pole (2) (pole 1μm
It is injected by the gap moon ζ nozzle (6).

The relative motion between the workpiece (1) and the wire M, pole (2) is.

This is performed by moving the table σD on which the workpiece (1) is placed. The tape tva1) is driven by a Y-axis drive motor a3 and an X-axis drive motor Q2Jζ. With the above configuration, the relative movement between the workpiece (1) and the electrode (2) is as described above.

This is a two-dimensional plane motion within the Y-axis plane.

Wire W% (2) is supplied by wire supply reel (7), lower wire guide (8A), workpiece (1)
It passes through the inside and reaches the upper guide (8B), and is wound up by the wire winding and tension roller 0G via the electric energy feeding section (9).

The drive motors (2) for the X and Y axes and the control device α4) that drives and controls α3 are a control device using a Kazuhama control device (NO control device), a copying device, or a control device using a '1jjx fence. 1 power supply 09 that supplies energy is 1, for example, DC w
! , source (15a), switching element (151))
, a current limiting resistor (15(3)) and a limiting circuit (15d) that controls the switching element (15b).

Next, the operation of the conventional device will be explained. A high frequency pulse voltage is applied from the W machining power supply 05 to the workpiece (1) and the wire it.
FiA (2) is applied to Ilfi, and a part of the workpiece (1) is scattered by m1 due to a discharge explosion caused by one vice.

In this case, since the gap between the electrodes is gasified and ionized by the high temperature, a certain pause time is required before applying the primary pulse voltage, and if this pause time is too short, the insulation between the electrodes will not recover sufficiently. Before this occurs, the discharge concentrates again at the same location, causing the wire 7 pole (2) to melt fJ-.

Therefore, in a normal machining power supply, the type of workpiece.

Wire 1 condition such as downtime of 770 engineering power 1af9 depending on board thickness etc.! Normally, processing is carried out under conditions that provide sufficient margin to prevent ffl breakage. Therefore.

The electric discharge speed must be considerably lower than the theoretical limit value, and if the wire electrode (2) is not uniform and its thickness changes, or if there are protrusions or scratches on a part of the wire electrode, the discharge will be concentrated. In this case, melting of the wire electrode (2) is unavoidable.

[The opening point that the invention seeks to solve] - As mentioned above, in the conventional wire cup discharge device, the wire is connected to the pole (two poles).
) In order to avoid breaking the wire, the machining must be done at the source (
The problem was that the 11 speed was extremely low because the wire was not disconnected even if the discharge concentrated on one point of the pole (2), such as by reducing the output power of the wire (to).
,was there.

Therefore, conventionally, safety measures have been taken to determine whether the 7IO machining state is good or not or whether the electrode is in a state immediately before damage, and based on the determination result, automatically restore the normal machining state or avoid damage to the electrode. 710 Please reduce the speed.
This is what is being done.

In this case, the most common means for determining whether the processed state (A) is good or bad or the wire MfM is about to break (2) is to observe the average value of the above-mentioned inter-electrode voltage values. That is,
When the average 7 voltage value is low, it means that the impedance between the electrodes is low, and dielectric breakdown due to discharge is likely to occur due to short circuit or accumulation of dust in the parts, resulting in discharge concentration (
This indicates that the main cause of wire breakage) has occurred.

However, when machining with a narrow gap (essential for machining with a good f'I of 11 degrees), short circuits occur frequently even with normal gap conditions, so safety measures were taken to detect short circuits. However, there was still a problem in that the labor efficiency was significantly reduced.

This invention was made to solve this problem, and it is possible to accurately determine the quality of the machining condition without reducing the continuous speed by 1 mm, and to prevent electrode damage accidents. The purpose is to obtain engineering equipment.

[Means for solving problems]

The discharge machining equipment according to the present invention has a pulse voltage of 100 KHz during the rest time J (deionization time between on-times that does not contribute to 7111 machining) of the pulse voltage applied between 'rIli and the workpiece. A detection means for detecting the degree of insulation of the machining fluid in the gap between the poles from the current value generated by applying the high-frequency alternating voltage as described above, and a detection means for detecting the degree of insulation of the machining fluid in the gap between the poles. A light discriminating means for discriminating the original state of the inter-electrode gap is provided for determining the inter-electrome condition based on the comparison result between the degree of insulation of the gap and a preset reference value, and the condition Q1 is displayed based on the output of this discriminating means. It is equipped with a transom monitor function.

[For production]

In the present invention, during the rest time of applying the pulse voltage a],
A high-frequency alternating current voltage was applied, which was independent of the ion concentration/concentration.

The pure degree of insulation can be detected. In other words, the WJ frequency AC voltage is 1 millimeter (suffuji)! The coexistence of deionized ions is AztI! When m is marked between i and m of the workpiece, the degree of transfer ψJ of electrolytic ions is insensitive to high frequencies, so only the degree of insulation due to the processing powder can be detected independently. In general, the causes of accidents during 7XI construction are:

This is due to concentration of discharge and depression, which causes wire breakage. Concentration of discharge points occurs when the transom impedance decreases due to I'1 powder when machining powder removal is poor, but in the conventional detection method, a unipolar voltage is applied, so the insulation level also decreases due to dissolved metal ions. It was detected without distinction. With this,! Although the concentration of decomposed metal ions is not a factor of discharge concentration, it is assumed that the interpolar condition is unnecessarily deteriorated and the recovery means is operated frequently, reducing the operating efficiency. The true discharge concentration factor is detected by the detection means, the detection result of this detection means is compared with a preset reference value by the specific gravity means, and based on the comparison result, the gap state determination means determines the The control means determines the state, and when the control means receives an abnormality determination signal from the above-mentioned determination means, the control means performs control so as to restore the state of the gap between the poles, so as not to reduce the single tool machining speed.

[Embodiments of the invention]

FIG. 1 is a perspective view showing one embodiment of the present invention, and the symbols (1) to (to) are exactly the same as those of the conventional device described above. The head is a high-frequency AC voltage current (due to processing powder.?! One, Zm detector for detecting the electric current flowing due to the edge drop, and the α force is a control command signal generator, which is a signal from the current detector Q6. The controller includes a detected current receiving means, a transom voltage detecting means, a comparing means for comparing the detected voltage with a reference value, and a pole gap state determining means for determining the pole gap state based on the output of the comparing means. 04. It is configured to supply a control command signal to a processing power source (to), etc.

High frequency AC power supply (to) is 10~25v1 frequency IME
(z (100KHz ~ 20MEZ usable) CI
) Consisting of an alternating current flETA generator (18a) and a row of current limiting impedance elements (18b), the 1β generator αG
When the pulse voltage is generated, the impedance element (181)) has no effect on the gap between the electrodes, and the voltage is 710 min.fl! , switching 1 child of source α9 (15
AC voltage is applied to the transom only when b) is off, ie during the rest period.

FIG. 2 shows the waveform of the chamber pressure Vg during t due to the configuration shown in FIG. M
The signal Sp when the pulse voltage is on, the Sn obtained by extracting the current signal only during the rest time using this Sp, and this SD are further envelope-detected, and the level /L' is set in three stages, and the distance between the poles is The impedance is low and a large leakage current flows above V1 (equivalent to 200Ω or less), and at a lower level NV't (equivalent to 1.5KΩ or higher).

Level/l/Vl Lower level and ■2 or less (71
Repe/L/) which is determined by the specific resistance of the liquid when not working 0
divided into V 1 (, V 1 ~ V!, Vl〉), respectively.
b as a group of signals.

FIG. 3 shows an example circuit for obtaining the signal group shown in FIG.
The current signal of the current detector σQ is amplified by an intensifier circuit (117) and becomes an input to an analog switch (118) as a signal. The opening/closing of the analog switch (118) is controlled by Sp, which is the suspension side signal of the pulse signal of NAKODEN # (to), and in this example, the signal is passed through the signal only during the suspension time. This passing signal is SJ), and a circuit (119) for envelope detection of this signal is composed of a diode D, a resistor R, and a capacitor C. The output Bx of 1 (139) is supplied to a voltage comparator, eD. , the output of the voltage comparator (2) becomes 1 when the input signal SD is greater than vl, and the output of the voltage comparator Q becomes 1 when the input signal SD is smaller than v2. AND gate I221 is Vz
This is for extracting a signal that is larger than Vl and smaller than Vl.

According to experiments, the impedance between poles is 500-700Ω
In the above cases, the discharge itself generates an arc column in the liquid and generates a high force (5000 to 70
00° C.) and the pinch effect is performed in a 1llJI manner, indicating that sufficient energy is distributed to the workpiece side.

In addition, when the resistance is 200Ω or less, spark discharge certainly exists (between V, but it does not exist between the electrode and the workpiece, but rather between the palm of the hand → swodge → the workpiece, or between the electrode → It was found that even if a discharge occurs from metal ions to the workpiece, the energy is not sufficiently distributed to the workpiece and the discharge state simply damages the wire fem.Therefore,
If this kind of condition is not removed immediately, the wire's
,! My damage and disconnection will occur.

Therefore, by controlling the working state (2) depending on whether it is 'V+( or Vl~22), it is possible to prevent the wire w from being damaged or disconnected. Discrimination means for discriminating the original state of the gap I′iJ1 based on the output of
This shows an example of the structure of the insulation deterioration signal (Ml<
) is counted by a counter (to) via a gate (goods). Further, the normal insulation level signal (V+-Vz) resets the above-mentioned counter (to) so that it does not continue counting unless abnormal discharge continues.

Therefore, it can be said that the contents of the counter (to) directly indicate the state between the two poles. This is because if the discharge is normal, the thermal force is ``0'', but if the positive zero discharge and the abnormal discharge are manipulated back and forth.

The average of the contents of the counter (to) becomes larger as it becomes abnormal, and becomes smaller as it becomes normal.

If there is a series of abnormal discharges up to I leading to wire breakage (2), the digital comparator (to) outputs a danger signal SA, and based on this signal, the state can be controlled.

Further, the analog output SN from the D/A converter is used for analog display, or the danger signal Bi is supplied to the monitor circuit. This monitor circuit #8@ is composed of a negative AND gate 1, a light emitting diode (LKD) 1, and a resistor re.

FIG. 5 is a time chart of the abnormal discharge detection mentioned above, and shows the analog value SM of the contents of the counter.

This figure shows the relationship among the danger signal SJ, the current signal, and the interpolar snow pressure signal Vg. Hereinafter, the operation of displaying the i-interval state (2) on a monitor will be described based on the contents of the above-mentioned power counter (a).

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an embodiment of the present invention, and FIG. 2 is a time chart showing the operation of this embodiment. FIG. 8 is a circuit diagram showing an example of means for detecting the degree of insulation between poles;
Fig. 4 is a circuit diagram showing an example of a means for identifying the gap state between poles, Fig. 5 is a time chart showing its operation, and Fig. 6 is a conventional wire-cutting W171O construction bag? It is a Harasaka diagram showing f. In the figure, (1) is the workpiece, (2) is the wire electrode, and α9 is processed 1! OQ is a W position detector, αη is a control command signal generator, 011 frequency alternating current is a source, and 2 is a discriminating means for discriminating the inter-plane gap shape U. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (1)

[Claims] An electrode and a workpiece are placed facing each other with an insulating machining fluid interposed between them, and a pulse voltage is applied between the electrode and the workpiece to generate an electric discharge between the two, and the workpiece is machined using the discharge energy. In the electric discharge machining apparatus, a means for superimposing a high frequency AC voltage during a rest period of the pulse voltage applied between the electrode and the workpiece, a detection means for detecting the insulation degree of the insulating machining fluid; a comparison means for comparing the insulation degree of the gap between the electrode and the workpiece detected by the detection means with a preset reference value; An electrical discharge machining apparatus characterized by comprising a gap state determining means for determining a gap state based on an output signal and outputting a signal.