JPS5854941B2 - Hoden Kakousouchi - Google Patents

Description

[Detailed description of the invention] The present invention provides an on-off switch in the machining gap between the electrode and the workpiece.
The present invention relates to an electric discharge machining apparatus that repeatedly performs machining by applying a machining pulse while turning off the pulse discharge.

In electric discharge machining, when the material combination of the electrode and the workpiece is determined, the ratio of ■po・6 to teon ■p0・6/τon is controlled to be below a certain value at the peak Ip of the discharge flow and the pulse width τon. By reducing the electrode wear rate,
It is known that processing can be performed with less than 1% consumption.

However, for repeated discharges, the discharge waiting time from applying voltage to the gap until the discharge starts changes depending on the gap adjustment of the machining gap and the concentration of intervening machining debris, etc., and the discharge state after the discharge starts also varies. Therefore, even if a predetermined controlled pulse voltage is applied, the current peak Ip and the pulse width τon change in the gap state, and the desired electric discharge machining without electrode consumption cannot be performed.

The present invention was proposed in view of this point, and includes ■pO°6
The present invention is characterized in that /τon is controlled to a predetermined value or less while detecting the discharge state.

This will be explained below using an example diagram.

In FIG. 1, 1 is an electrode, 2 is a workpiece, and they face each other to form a machining gap.

Reference numeral 3 denotes a switching element such as a transistor, which controls the processing power source 4 on and off by switching it to generate processing pulses.

A flip-flop 5 applies a control signal to the switch 3, and a multi-by-break 6 performs binary control.

Reference numeral 7 denotes a discriminator circuit for discriminating and checking the gap voltage to detect the start of discharge, and 8 a one-shot multi-timer, etc., which is activated by the discharge start signal of the discriminator circuit 7 and determines the pulse width τon.

Reference numeral 9 denotes a discrimination circuit that detects and discriminates the current peak Ip during discharging. Based on this discrimination output, time changes such as circuit constants of the timer 8 are controlled by switching between analog and digital modes.

10 is the control device, and this control is ■p0°6/τon<
Based on the detected and determined Ip, τon is controlled to change so that it becomes k.

11 is an AND gate with 8 timer outputs and 6 multi-outputs,
This combined signal is added as a set signal to the flip-flop 5.

In the machining gap, the flip-flop 5 is reset by the oscillation of the multi-by-break 6, and the switch 3 is turned on, thereby applying a machining pulse from the power source 4 to generate electric discharge.
One pulse discharge is completed by setting the flip-flop 5 using the inverted output of the multi-6 and turning off the switch 3. Electric discharge machining is performed by repeating this based on the operation of the multi-by-break 6. Each repeated pulse discharge is discriminated and checked by discrimination circuits 1 and 9, respectively.

That is, the discrimination circuit 7 detects the start of discharge by the gap voltage drop and sends an activation signal to the timer 8.

The timer 8 starts operating in response to a discharge start signal from the discriminator circuit γ, and when a predetermined time period is completed, which corresponds to the discharge pulse width τon, a signal is output to the AND gate 10 and the flip-flop 5 is activated. set.

That is, the flip-flop 5 is not set only by the oscillation output of the multi-by-break 6, but is set by ANDing the multi-oscillation output and the output of the timer 8.

By the way, if the current peak ■p increases for some reason, this will be detected and determined by the discrimination circuit 9, and the timer 8 will be controlled by the output signal of this discrimination circuit to increase the pulse width τo.
n is increased and changed.

This control for changing τon increases τon in accordance with an increase in Ip so as to satisfy the condition of IpO°6/τon<k (constant value).

Conversely, when Ip decreases, τon
is controlled to decrease, and a pulse discharge that always satisfies the condition of Ip0.6/τon<k is performed.

This ■p0°6/τon<k is, for example, when performing St processing using a Cu electrode, when the polarity is such that the electrode is the positive electrode and the workpiece is the negative electrode, ■p0°6/τon<k.
If it is 0.4, processing can be performed with an electrode consumption ratio of 1φ or less.

Furthermore, when increasing the machining speed as a main factor or increasing the roughness of the machined surface as a whole, the desired machining can be carried out by optimally setting and controlling each of the above values.

FIG. 2 shows another embodiment in which the current peak Ip is controlled by detecting and determining the pulse width τon of the discharge generated in the gap, and a plurality of power switches 31, 32,
33 are connected in parallel, each with a control flip-flop 51.
．． 52 and 53 are provided, and a selection circuit 13 is inserted into this reset signal circuit to perform selection control.

Reference numeral 12 is a discrimination circuit that detects the voltage signal in the gap and discriminates whether the time from the start to the end of discharge, that is, the pulse width τon, is long or short.

Then, the selection circuit 13 is controlled using this discrimination signal.

The reset signal by multi-by-break 6 is sent to selection circuit 1.
Flip-flop selected through 3 51.52,5
3 and turns on the selected switches 31, 32, 33. However, if the previous pulse discharge is determined by the discrimination circuit 12 and the pulse width τon is short, the discrimination signal is added to the selection circuit and turns on the multi-by-break 6. A reset signal is applied to the flip-flop 51 to turn on the switch 31,
The flip-flop 51 is set by the multi-inversion signal to end the pulse discharge.

Since the circuit resistance of the discharge pulse caused by on/off switching control of only the switch 31 is higher than that of the other switches 32, 33, etc. operated in parallel, the current peak Ip is reduced, and the current peak Ip is small corresponding to the pulse width τon. A discharge takes place.

When the pulse width τon of the discharge thus generated increases, the selection circuit 13 selects the flip-flops 51 and 52 or 51, 52 and 53 based on the output of the discrimination circuit 12, and applies a reset signal to 32
, and 33 are operated in parallel.

The normal discharge pulse width τon, which reduces the circuit resistance and increases the current peak Ip by simultaneously operating multiple switches in this way, changes depending on the state of the gap at the start of discharge, so it corresponds to the change in the waiting time for the start of discharge. However, the response of gap control by servo etc. is very slow compared to repeated discharge, so when the discharge pulse width is shortened, a discharge with a short pulse width τon is performed continuously, and the pulse width is increased again. In this case, a long pulse τon discharge continues to occur until the gap servo performs response control, and as described above, the discrimination circuit 12 selects a plurality of parallel switches 31, 32, If the next discharge flow peak Ip is controlled by the selection control of 33, the target pulse discharge can be easily repeatedly generated. By designing so that 6/τon<k is satisfied, processing can always be performed under the condition that the electrode is not consumed.

Although the above has been explained using one example, various types of control devices can be used to control the peak Ip and pulse width τon of the discharge flow, and various types of devices can also be used for detection and discrimination. ,■p0°6/τon is kept at a constant value by the following control, and by setting k to a certain value depending on the material combination of the electrode and workpiece, and the conditions from rough machining to finishing machining, etc. High-precision electrical discharge machining is possible under non-consumable conditions with a wear ratio of 1% or less.

Further, it is possible to perform machining under conditions where the machining speed is increased and the roughness of the machined surface is reduced.

[Brief explanation of the drawing]

FIG. 1 is a circuit configuration diagram of one embodiment of the present invention, and FIG. 2 is a circuit diagram of another embodiment.

Claims (1)

[Claims] 1. In electrical discharge machining equipment that applies machining pulses to the machining gap between the electrode and the workpiece by on/off control of a switch,
A device that detects and determines the peak Ip or pulse width τon of the discharge current generated in the machining gap, and based on the detection and determination, ■ the ratio of p0°6 and τon, and ■ the ratio of p0°6/τon always below a set constant value. The above Ip or τo
An electrical discharge machining device characterized by being provided with a control device for controlling n.