JPS6331328B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electric discharge machining apparatus that automatically searches for machining conditions and optimizes the electric discharge machining conditions.

Conventionally, in order to perform electrical discharge machining efficiently, machining conditions that make electrical discharge machining stable are sequentially searched for to increase the effective discharge occurrence rate. In such an apparatus, desired machining efficiency cannot be obtained unless the speed or cycle of searching for machining conditions is appropriate. In other words, when searching for electrical discharge machining conditions, when the search step is raised or lowered by one step, the machining state settles to a steady state after a predetermined time delay, and then the magnitude of the effective discharge occurrence rate is determined, and the result of this determination is The machining is performed by changing machining conditions (for example, machining fluid pressure, set voltage, machining pulse duty factor, electrode vertical hunting period, etc.) depending on the conditions. The delay time from when the machining conditions are changed by one step until the machining condition settles down varies depending on the type of machining conditions changed and the level of the machining conditions (machining voltage 100V, 200V, 300V, etc.), but conventionally The delay time was set to an average (intermediate) value. Therefore, depending on the machining conditions, the delay time may be set too early or too late, resulting in a decrease in machining efficiency.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an electric discharge machining apparatus which eliminates the above-mentioned conventional drawbacks, sets an appropriate delay time in accordance with changes in electric discharge machining conditions, and improves machining efficiency.

In order to achieve the above object, the present invention is an electric discharge machining apparatus that includes a search device that repeatedly searches for electric discharge machining conditions, and an adjustment device that adjusts the search period of this search device according to the machining conditions.

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

FIG. 1 is a block diagram showing one embodiment of the present invention. In the figure, 1 is a pulse power supply, 2 is an electrode, 3 is a workpiece, 4 is an effective discharge rate detection circuit for detecting and processing a discharge state based on a voltage waveform between electrodes to obtain an effective discharge rate, and 5 is a size discrimination circuit for determining the maximum value of effective discharge rate, 6, 9, 10, 1
1 and 12 are AND gates; 7 is a search order sequence circuit for determining the search order of each processing condition;
8 is an oscillator, 13 is a search pulse generation circuit for determining the search speed for each processing condition, 14 is an OR gate, and 15, 16, 17, and 18 are processing fluid pressure, set voltage, pulse duty factor, and electrode, respectively. Search range limiting circuits 19, 20, 21, and 22 are used to determine the search range of the vertical hunting period, and setting circuits 19, 20, 21, and 22 are used to set the values of the machining fluid pressure, set voltage, pulse duty factor, and electrode vertical hunting period, respectively. , 23, 24, 25, and 26 are storage circuits for storing the optimum values of each processing condition;
Reference numerals 7, 28, 29, and 30 indicate output terminals for outputting control signals to be applied to drive circuits (not shown) for each processing condition.

Next, the operation of the present invention will be explained. Each machining condition setting circuit 19, 20, 21, 22 is activated by a machining start signal included in the search order sequence circuit 7.
An initial value is given to , and machining is started. The search is started in the order determined by the search order sequence circuit 7. For example, in the case of machining fluid pressure, an output signal is obtained from terminal A and is applied to the machining fluid pressure search range limiting circuit 15, and within a predetermined pressure range, A machining fluid pressure signal set by the machining fluid pressure setting circuit 19 is generated to change the machining fluid pressure. During this time, the effective discharge rate is detected by the effective discharge rate detection circuit 4 based on the inter-electrode voltage waveform, the maximum value of the effective discharge rate is determined by the magnitude discrimination circuit 5, and the value when the effective discharge rate is the maximum is determined. The machining fluid pressure value is stored in the memory circuit 23, and at the same time as the search ends, the stored value is set again in the machining fluid pressure setting circuit 19, and machining is performed using the optimum value. In the above operation, the search clock pulse is
A signal is obtained from the search clock pulse generation circuit 13 with a period _T3 shown in waveform G in FIG. According to experiments, the value of this period _T3 is 1 when searching for machining fluid pressure.
Since it takes about 20 seconds for electrical discharge machining to reach a steady state when the machining fluid pressure is changed by a step (for example, 0.1 Kg/cm ² ), about 20 seconds is recommended. In addition, it is connected to the output of the size discrimination circuit 5.
Since this search pulse is applied to the other input of the AND gate 6, the AND gate 6 opens only during the _T0 interval. The value of T ₀ is preferably 0.1 to 1 second. That is, after the search pulse is applied, the output signal of the magnitude discrimination circuit 5 is obtained from the AND gate 6 within the time width of the pulse T ₀ when the next search pulse is input. That is, the size is determined between 19 seconds and 20 seconds after the machining fluid pressure is changed by one step. Also, when searching for the set voltage,
The output terminal B of the search order sequence circuit 7 becomes the "1" level, and the set voltage is searched in the same manner as described above using a search pulse of period T ₁ shown in the waveform E determined by the search pulse generation circuit 13 to find the optimum value. . The value of the period T ₁ may be relatively short, and a value of about 5 seconds is recommended. Similarly, when searching for a duty factor, the search pulse _T2 is approximately
About 10 seconds is fine. Further, the period of the search pulse in the electrode vertical hunting period may be the same period as in the case of machining fluid pressure.

As described above, the present invention is an electric discharge machining apparatus equipped with a search device that repeatedly searches for electric discharge machining conditions and an adjustment device that adjusts the search period of this search device according to the machining conditions. (period) to an appropriate value and determines the magnitude of the effective discharge rate after electrical discharge machining reaches a steady state, making it possible to set the optimum machining conditions.
Moreover, processing efficiency can be improved.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention;
FIG. 2 is a waveform diagram illustrating the operation of FIG. 1. DESCRIPTION OF SYMBOLS 1... Pulse power supply, 2... Electrode, 3... Workpiece, 4... Effective discharge rate detection circuit, 5... Maximum value discrimination circuit, 7... Search sequence, 8... Oscillator,
13...Search pulse generation circuit, 15...Working fluid search range limiting circuit, 16...Setting voltage search range limiting circuit, 17...Pulse duty factor search range limiting circuit, 18...Electrode upper and lower hunting period search range Limited circuit, 19... Processing fluid pressure setting circuit,
20... Set voltage setting circuit, 21... Pulse duty factor setting circuit, 22... Electrode up and down hunting cycle setting circuit, 23... Machining fluid pressure memory circuit, 24... Set voltage memory circuit, 25... Pulse Duty factor memory circuit, 26... Electrode upper and lower hunting memory circuit, 27... Machining fluid pressure control output terminal, 28... Set voltage control output terminal, 29...
...Pulse duty factor control output terminal, 30
...Electrode top and bottom hunting cycle control output terminal.

Claims (1)

[Claims] 1. In an electrical discharge machining apparatus that supplies a machining fluid between an electrode and a workpiece disposed facing each other, and supplies machining pulses from a pulse power source between the electrode and the workpiece, the electrode and the workpiece are An effective discharge rate detection circuit that detects the discharge state occurring between the workpieces and obtains the effective discharge rate, a size discrimination circuit that determines the maximum value of the effective discharge rate from this effective discharge rate detection circuit, and settings for the machining pulses mentioned above. The machining conditions such as voltage, duty factor, pressure of the machining fluid, and vertical hunting cycle of the electrode are gradually changed from the initial values in a predetermined order, and when the effective discharge rate reaches the maximum, the above-mentioned size is determined. A search device that stores the value of the machining condition based on the output from the circuit, and a search pulse generation circuit that sets a search period for the machining condition that the search device gradually changes from the initial value for each machining condition. An electrical discharge machining device characterized by having the following.