JPS58223530A - Electrospark machining apparatus for wire cut - Google Patents

Abstract

PURPOSE:To increase electrospark machining speed by giving high order forcible vibration to a wire electrode and changing the repetitive number of the electrospark machining depending on the thickness of a workpiece. CONSTITUTION:Pulse voltage is applied cross a workpiece 3 and a wire electrode 1 by a power supply 10 for electrospark machining. A high order forcible vibraton is given to the wire electrode 1 by a vibration device 4 to provide a plurality of bellies and knots. The change in the plate thickness of the workpiece 3 when it is cut is detected by a detector 12 and the frequency of applied pulse voltage of the power source 10 is controlled by this plate thickness detecting signal. As the plate thickness becomes thicker, the repetitive number of discharge is increased. Since the high order vibration is given to the wire electrode 1, the number of bellies in the plate thickness can be increased dependently on the plate thickness to improve working speed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a wire-cut electric discharge machining apparatus that processes a wire A7 electrode that moves between guides and a workpiece by applying pulse discharge to a gap in which they face each other with a minute gap.

A thin wire with a diameter of about 0.05 to 0.5 mm is used for the wire electrode. This wire is moved with tension applied between the guides, causing an electrical discharge in the gap between the opposing workpieces and processing, so the pressure of the electric current acts on the discharge point, and the string is played just in time. The frequency of vibration of the wire electrode at this time, F (c/s), is −upper V (1) L r where n: vibration order, L: length between guides U ) P
: Tension ('?), (1; Gravitational acceleration.

r: ° Unit length of wire electrode 4 times 41 (ki/cm)
It is expressed as This vibration of the wire electrode seems to be inconvenient for wire cutting, but it is due to the effect of moving the discharge point.

It is actually effective for wire cutting, such as extinguishing arc short circuits and promoting the removal of processed chips and gas, and there is an idea to actively utilize this vibration to increase processing speed. Conventionally, a device has already been proposed that forcibly applies seven vibrations to the wye.

On the other hand, when wire cutting is performed, processing conditions are not always constant from beginning to end. There are various thicknesses of workpieces, from thick to thin, and there are plate processing processes in which the thickness of a single plate changes locally. Since the amount of machining increases when the plate thickness is thicker than when the plate thickness is thinner, the machining feed rate does not decrease inversely proportionally even though the machining chips are removed by the vibration.

In view of these points, the present invention applies high-order forced vibration to the wire electrode, and also provides a machining power source that changes and controls the number of discharge repetitions as a function of the thickness of the workpiece, thereby increasing the machining speed. It is measured by

The present invention will be explained below with reference to the drawings. In FIG. 1, 1 is a wire electrode, 2 is a guide, and 3 is a workpiece. A predetermined tension P is applied to the wire electrode 1 between the guides 2 having a length of L, and assuming that the unit length weight of the wire electrode and the gravitational acceleration are constant, in the vibration according to equation (1),
If it is forced to vibrate using a vibrating device (not shown), it will vibrate at an order n proportional to its frequency F. For convenience, it is assumed that vibration of order n=3 is given. (a) The workpiece 2 facing the wire electrode 1 is the thinnest plate, (b) the figure is about twice as thick, and (c) the plate is even thicker.

Therefore, the wire electrode 1 and the workpiece 2 that vibrate like this
Since the antinode of the vibration of the wire 1 is closest to the workpiece 2, the discharge mainly occurs at this antinode. Of course, the position of the two antinodes of vibration changes every cycle. (b) In the diagram, 1
Two vibrational antinodes face the workpiece 2, but two vibrational antinodes in the figure (b) and three vibrational antinodes in the figure (c) simultaneously face the workpiece 2. If the frequency of the pulse is increased so that discharge occurs one after another at each vibrating part facing the workpiece during the cycle, that is, the frequency in Figure (B) is doubled compared to that in Figure (A), and ( c) In the figure, if the control is tripled, the amount of processing will increase proportionally. (B) In the figure, the amount of machining is small because the plate thickness is thin, but in the figure (B), the amount of machining per unit length of machining feed is approximately doubled in proportion to the plate thickness, and (C) the workpiece in figure In the body, the number of discharges is approximately three times, but if the number of discharges is approximately twice as high in (B) and approximately three times as high in (C) as shown above, the machining power source must be pulsed again. By controlling the number in this way, processing speed can be increased. Therefore, even if the thickness of the workpiece changes locally, the workpiece can be machined at a substantially constant feed rate, and wire cutting can be performed with high efficiency and precision.

Next, FIG. 2 will be explained. 1 is a wire electrode.

Reference numeral 2 denotes a guide, and the wire electrode 1 moves between the guides from below to above in the direction of the arrow. Although the moving device is not shown, it is moved with a predetermined tension and speed using a capstan, a pinch roller, and a brake roller. 3 is a workpiece having a predetermined thickness, and 4 is a device for applying vibration to the wire A7 electrode 1. The vibration of a moving coil vibrated by electromagnetic force is transmitted to the wire 1 to cause the wire 1 to vibrate. 5 is a pulse generation switch for the processing power supply, 6 is a voltage source, switch 5
The on/off switching of the oscillator provides repeated pulses. Although the pulse may be directly supplied to the wire A7 electrode 1 and the three workpieces, a capacitor 7 is provided to increase the peak current I11 of discharge, and the pulse is supplied to the gap by charging and discharging the capacitor 7. Reference numeral 8 denotes a pulse generation circuit for controlling the on/off state of the switch 5, and an arbitrary oscillator, a method of generating pulses by counting clock pulses, and others can be used. Reference numeral 9 denotes a preset switch for a pulse frequency corresponding to the plate thickness, which performs presetting according to the plate thickness of the workpiece 3 to be machined.

In the above, the wire electrode 1 is vibrated by the vibration device 4 at a normal frequency of 1 to about 100 Kl-1z. For example, use a 0.2 φ CU wire for wire electrode 1, P = 800g, L = 10cm, r = 2,8
If x104ks/cm, the frequency F from equation (1)
= IOK HZ and order n = 12. F=33KH
n = 40 in z. F=50KH2rn=59. Therefore, if we perform a high-order vibration of order n = 40 with a vibration of F = 33 KHz, the antinodes of vibration will occur at intervals of approximately 2.5 u, and when machining a workpiece with a plate thickness of t = 10 mm,
When [=30mm, there are 12 antinodes, and t
At =50, you will be facing a 20 belly. Therefore, the setting by the preset device 9 is, for example, t=10mm.
The switching pulse is 30KHz, t = 30u
and 4sH-Hz, t = s.

All you have to do is to preset the frequency to 50KHz.

According to experiments, 5KD-1 at 0,2 miφCu1l
When cutting a single piece of wire, water with a specific resistance of 5 x 104 ΩCm was used as the machining fluid, a tension of about 600 g was applied to the wire electrode, and vibrations of 30 KHz were applied to the wire electrode. When machining a plate thickness of t=10, a machining feed rate of 2.3 mm/1 lin was obtained by machining with a 30 KHz pulse power source.

In the case of no vibration, this is approximately twice as high as 1.2 ww/In1n. Next, when machining was carried out at t=30, the machining feed rate was approximately 0.9 u/l1in, which was faster than approximately 0.6 mm/min when there was no vibration, but at this time, the processing speed with the pulse power supply was When the frequency was increased to 45 KH2, a maximum machining feed rate of 1.2 f/min was obtained.

Furthermore, at t=50u, the pulse frequency is increased to 50K)l
When increased to z, the maximum machining speed is approximately 0.8u/1llin
It became.

From the above, it can be seen that by applying high-order vibration to the wire electrode and controlling the pulse frequency of the machining power source according to the plate thickness, the machining feed rate can be approximately doubled.

Note that the vibration device 4 can be used not only in the embodiment, but can also be used, for example, by applying a magnetic field or changing magnetic field to the wire electrode portion through which a machining current flows or the wire portion provided with an energizing device to directly cause the wire electrode to vibrate. In addition, a vibration device using an electrostrictive or magnetostrictive material as a vibration source, or other mechanical vibration generating device can be used. The frequency is controlled and set to the best value depending on the machining conditions and conditions, but it is usually used in the range of 1 to 100 KHz.

FIG. 3 shows an example in which a workpiece 3 having a change in thickness is wire-cut. 10 is a processing power supply, 11 is a resistor that detects the voltage in the gap, and 12 is a device that discriminates and detects a plate thickness signal of the processed part of the workpiece 3 based on the detection voltage of the resistor 11. In addition, the pulse repetition rate is automatically controlled.

A required shape processing feed is applied to the workpiece 3 by an NC11JllIl device (not shown). If feed is applied in the X-axis direction in the illustrated state, the thickness of the workpiece will increase as the machining progresses. Since the illustrated workpiece 3 has a plate thickness that changes stepwise, there is a flat portion that does not change at the plate thickness change point during processing. Therefore, if the machining feed rate is kept almost constant, the voltage detected by the resistor 11 is almost constant while machining a flat portion where the plate thickness does not change, but as the number of plates increases, the voltage between the machining electrodes decreases. The detection voltage of the resistor 11 is determined by the device 12 to generate a plate thickness signal. The processing power supply 10 receives this plate thickness signal and presets the pulse repetition rate corresponding to the signal. That is, the frequency is increased by increasing the thickness of the plate.

The number of pulse repetitions is normally set to 10 within a range of about 500 KHz. Of course, when the plate thickness decreases, the number of repetitions is also changed to decrease. In this way, even if the thickness of the plate to be processed changes depending on the part to be machined, as the plate thickness increases, the vibration antinode facing the workpiece increases, so the pulse frequency should be controlled to increase accordingly. By doing this, the machining speed is increased, and conversely, when the plate thickness decreases, the pulse frequency is controlled to decrease, thereby keeping the machining feed rate almost constant and achieving high efficiency.

It is possible to complete high-precision shape cuts.

Note that in order to detect the plate thickness signal of the workpiece, when servo feeding is applied, a change in the plate thickness results in a change in the feed rate, so the plate thickness signal can be detected even if a change in the feed rate is detected. Also machining current and leakage current.

It can also be detected by other combinations of voltage, current, feed rate, etc. Also, if the design is such that the thickness changes depending on the position of the machining path due to the machining shape, the change in thickness can be detected when programming the NG tape. Since the information can be input in advance, the plate thickness signal can be easily detected as the machining progresses, and the number of discharge repetitions can be automatically controlled. The plate thickness signal may be detected using an optimal means depending on the processing conditions and processing mode.

In addition, if the machining power supply discharges a switching pulse by directly supplying it to the gap, the supplied pulse and the number of discharge repetitions will match, but the switching pulse shown in Fig. 2 will charge and discharge the capacitor 7 installed near the gap. In this method, the number of discharge repetitions in the machining gap due to capacitor discharge and the supply pulse for charging the capacitor do not necessarily match. Therefore, when using such capacitor charging and discharging, the voltage may be increased and the supplied current may be controlled without changing the frequency of the charging pulse.

That is, when a signal indicating an increase in plate thickness is inputted from the device 12 at 43 in FIG. 3, the current is controlled to increase while the frequency of the overlapping pulse supplied from the processing die m10 remains unchanged.

Then, the capacitor (not shown) installed near the gap is charged and discharged multiple times for each supply pulse to increase the number of discharge cycles in the gap, so even with this control, the plate thickness increases and the workpiece becomes thinner. In response to an increase in the number of vibrations of the opposing wire electrodes, the number of repetitions of electric discharge can be increased and vibration vibrations can be effectively utilized for machining, and similar machining effects can be expected.

Note that the current of the supply pulse of the processing power source is controlled by switching the number of parallel connection of on/off switching elements that generate pulses, controlling the circuit resistance, or controlling the voltage of the voltage source. Alternatively, the charging capacitor capacity can be changed at the same time.

As described above, the present invention causes the Wie A7 electrode to vibrate at a high order so that a plurality of vibration vibration amplitudes face the workpiece,
Therefore, when the thickness of the workpiece is thicker than when it is thinner, the number of opposing vibrational bands increases.

Therefore, this forced vibration is performed and the number of discharge repetitions is changed and controlled as a function of the plate thickness of the workpiece.

The number of discharge repetitions is controlled by controlling the frequency of the pulses supplied from the machining power supply and the current control of the supplied pulses, so that when the plate thickness increases, the discharge can be effectively performed at each part of the increasing vibration center facing the workpiece. .

Therefore, even if the plate thickness increases and the amount of processing increases, the processing speed can be increased, and high-speed processing can be performed without reducing the feed rate.

In addition, when machining workpieces with varying plate thicknesses, the machining power supply is controlled based on the plate thickness change signal.By controlling the machining power supply, the entire body can be machined at a nearly constant speed, increasing machining efficiency and machining accuracy. I can do it.

[Brief explanation of the drawing]

FIG. 1 is a diagram illustrating the present invention in detail, FIG. 2 is a configuration diagram of one embodiment of the invention, and FIG. 3 is a diagram of another embodiment. 1...Wire electrode 2...Guide 3...Workpiece 4...Vibration device 5. ......Switch 6...Voltage source 7...Capacitor 8...Pulse generating circuit 9... ...Preset switch 10...
..... Processing power supply 11 ..... Voltage detection resistor 12 ..... Plate thickness signal detection device Ij7

Claims (2)

[Claims] (1) A wire-cut electric discharge machining device is equipped with an imaging device that applies high-order forced vibration to the wire electrode moving between guides, and a machining power source that changes and controls the number of discharge repetitions as a function of the thickness of the workpiece. Wire A7 cut electric discharge machining equipment characterized by being provided with. (2) Wire A7 cut electric discharge machining equipment is equipped with a vibrating device that applies high-order forced vibration to the wire electrode moving between guides, and processing that changes and controls the discharge repetition rate as a function of the plate thickness of the workpiece. A width A7 cut electric discharge machining apparatus, characterized in that a power source is provided, and the machining power source is provided with a device for detecting and supplying a plate thickness proportional signal of a machined portion of a workpiece.