JPS603929B2 - Processing pulse power supply circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a machining pulse power supply circuit for an electrical discharge machining apparatus that can obtain an electrical discharge machined surface with small surface roughness.

In general, it is known that in order to reduce the surface roughness of a machined surface in an electrical discharge machining apparatus using a non-storage type pulse power source for machining, the width of the machining pulse can be narrowed.

For this reason, in conventional non-energized pulse power supply circuits,
A high-performance high-frequency switching element was used to generate machining pulses with a narrower pulse width in order to improve the surface roughness of the electrical discharge machined surface. However, the peak voltage of this type of pulse is large, on the order of several tens of volts, and the switching characteristics of switching elements used at such high voltages make it difficult to maintain the minimum pulse width of electrical discharge machining pulses. However, considering the effective discharge rate, the minimum value of the pulse width is approximately 2 [As] from a practical point of view.
ec] level. When machining is performed with such a machining pulse having a very narrow pulse width, the obtained surface roughness value is usually about 3 [ARmax]. Therefore, if a surface roughness of less than this value is required for the machined surface, it becomes necessary to perform polishing in a separate process, which poses the problem of increasing the number of processes and processing costs. Was. Therefore, an object of the present invention is to avoid narrowing the pulse width of the conventional processing pulse below the above-mentioned limit.
It is an object of the present invention to provide a power supply circuit for an electric discharge machining apparatus that can obtain an electric discharge machined surface with a smaller surface target degree at a relatively high machining speed.

The present invention reduces the pulse width of the electrical discharge machining pulse and at the same time smoothes the rise characteristics of the pulse.
This is based on the knowledge that it is possible to obtain an electrical discharge machining state with a shallow cutting depth, which is different from the conventional electrical discharge machining state.

Hereinafter, the present invention will be explained in detail with reference to illustrated embodiments.

FIG. 1 shows a circuit diagram of a non-storage machining pulse power supply circuit for an electric discharge machining apparatus according to the present invention.

The power supply circuit 1 includes a switching transistor 3 that is controlled on and off by a pulse controller 2, and a DC power supply 4 is connected to a collector circuit of the switching transistor 3 through a resistor 5.
connected via. 6 and 7 are either an electrode or a workpiece, and the other one is connected to the negative electrode of the DC power source 4, and one of the electrodes or the workpiece is connected to the negative electrode of the DC power supply 4, and On the other hand, an air-core coil 8 is provided between the output circuit of the switching transistor 3 and the switching transistor 3 .

The air-core coil 8 is provided for the purpose of smoothing the rise characteristic of the processing pulse generated by the switching operation of the switching transistor 3, and the selection switch 9 allows the emitter of the switching transistor 3 to be connected to the air-core coil 8. By connecting to any one of the taps 8a to 8d, the inductance of the coil in the emitter circuit can be adjusted.The pulse controller 2 controls the duration of the pulse taken out from the emitter circuit of the switching transistor 3. However, if you want to obtain an electrical discharge machined surface with small surface roughness such as in finishing machining, the pulse 1
It is appropriately set to output a processing pulse among pulses of 0 [French sec] or less.

On the other hand, the inductance value of the air-core coil 8 is determined so that the rising waveform of the electric discharge machining pulse has a gradual rise characteristic as shown by the dotted line in FIG. 2, as shown in FIG. It will be done. It was confirmed that the larger the value of this inductance, the more gradual the rising characteristics of the pulse waveform, and the more gradual the rising of this pulse waveform, the smaller the surface roughness of the electrical discharge machined surface. 10 during pulse
The reason why the surface roughness of the electrical discharge machined surface is reduced by making the rise characteristic of the thin machining pulse of [French sec] or less gentle is as follows.

If the pulse width of the machining pulse is narrowed, the size of the hole cut by the electric discharge becomes smaller and the surface roughness can be reduced. This is because the state of the hole changes, and the depth of the hole carved out by the discharge becomes smaller and at the same time the size of the hole becomes wider. According to experiments, it has been confirmed that by smoothing the rise characteristic of the machining pulse in this manner, the surface roughness of the electrical discharge machined surface can be reduced to about 1 [Rmax]. The inductance of the air-core coil required to obtain such good surface roughness is:
The value must be set with enough margin to cancel out the stray capacitance that exists on the switching element side when viewed from the air-core coil, and still make the pulse rise characteristics smooth. H] or more is required. Moreover, if the rising characteristic of the machining pulse is made gentle in this way, the effective discharge rate in the discharge machining gap will be reduced.

In order to improve the reduction in effective discharge rate, a resistor 10 is connected in parallel with the air-core coil 8', so that a DC bias is applied to the machining gap. Therefore, as shown in FIG. 2, the shape of the green leading edge of the processing pulse once rises vertically due to the resistor 10;
It will rise gently depending on the value of the inductance of the air-core coil 8. Therefore, compared to the case where the resistor 10 is not provided, the so-called discharge stiffness is improved and the effective discharge rate can be improved.

As a result, the surface roughness of the machined surface can be made extremely small without significantly reducing the electrical discharge machining speed. Of course, in order to improve the effective discharge rate, it is also effective to increase the DC power supply voltage, and in conventional devices, the DC main power supply voltage is about 60 to 100 volts, but according to experiments, it is effective to increase the DC power supply voltage. When the rise characteristics were made gentler, an effective discharge rate almost equivalent to that of the conventional method could be obtained by using a DC power supply voltage of 150 volts or more. In addition, resistor 1,
In addition to the above-mentioned action, it also has the action of quickly reducing the energy stored in the air-core coil 8 to zero when the transistor 3 is turned off.

In this way, by narrowing the pulse length of the machining pulse and at the same time making the rise of the machining pulse gradual, an electric discharge machining state with a shallow cutting depth can be obtained, and the surface roughness of the electric discharge machined surface can be reduced to approximately 1 [Rmax]. can be improved to. The surface roughness of the electrical discharge machined surface is set to a desired value by adjusting the switching position of the selection switch 9. Therefore, it is possible to obtain an electrical discharge machined surface with a smaller surface density without making the pulse of the machining pulse extremely small.
It becomes possible to use inexpensive elements as switching elements, and it is possible to reduce the cost of the device and to significantly improve the performance.
・In the above embodiment, a processing pulse power supply circuit is provided with only one switching circuit for generating processing pulses, but a high voltage superimposed power supply for triggering is additionally added, and The present invention can be similarly applied to a machining pulse power supply circuit in which a switching circuit is further provided corresponding to the superimposed power supply, and a machining pulse is applied to the machining gap using a DC main power supply and a high voltage superimposed power supply. In this case as well, the above-mentioned effects can be obtained.

According to the present invention, as described above, an electric discharge machined surface with a smaller surface roughness can be obtained at a relatively high machining speed without narrowing the pulse width of the machining pulse beyond the conventional limit. It has a great effect.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of an embodiment of the present invention, and FIG. 2 is a waveform diagram showing the waveform of the processing pulse of the present invention. 1...Power supply circuit, 2...Pulse controller, 3...
...Switching transistor, 4...DC power supply, 8...Air core coil, 9...Selection switch. Evening 7th figure, younger brother 2nd figure

Claims (1)

[Claims] 1. A non-storage type machining pulse power supply circuit for supplying machining pulses to an electric discharge machining gap, the pulse width being 1.0.
A switching circuit that generates a pulse of [μsec] or less, an inductance element provided on the output side of the switching circuit to give a gradual rise characteristic to the pulse generated in the switching circuit, and an electric discharge caused by the pulse in the machining gap. 1. A power supply circuit for machining pulses, comprising: a resistance element connected in parallel to the inductance element in order to facilitate the initiation of processing. 2 The inductance of the inductance element is 3 [μ
The processing pulse power supply circuit according to claim 1, wherein the power supply voltage applied to the switching circuit is 150 [V] or more.