JPS6331327B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrical discharge machine control device.

Conventionally, in order to perform electrical discharge machining stably, the discharge state is detected, each machining stability factor is controlled in order so that the discharge state, that is, the effective discharge rate is the best, and the optimal value of the machining stability factor is automatically determined. That's what I was doing.

However, the order of searching for such machining stability factors is, for example, as a search in the initial stage of machining, the machining fluid pressure setting voltage, pulse duty factor, and electrode top and bottom hunting cycles are performed once each, and then as a re-search, machining fluid pressure and electrode top and bottom hunting cycles are performed once. Hunting period only 5
They searched a predetermined area alternately at ~10 minute intervals.
Such relatively simple repetition has the disadvantage that the best processing efficiency cannot be obtained depending on the material and shape to be processed.

As a result of investigating the machining characteristics between various machining conditions in electric discharge machining, the present invention theoretically determines the search order for each machining stability factor, and if the order is followed, the best machining efficiency can be obtained. It is an object of the present invention to provide a control device for controlling optimal machining conditions for an electric discharge machine in which a detailed search order for machining conditions is set. To be more specific, the present invention determines the search order for machining conditions such as machining fluid pressure, pulse duty factor, set voltage, and electrode vertical hunting period based on the influence of machining characteristics among machining conditions. This control device for an electric discharge machine is characterized in that the initial search is performed alternately over a predetermined number of times, and the search is performed again to search a predetermined range at regular time intervals.

An embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of a control device for an electrical discharge machine according to the present invention. In the figure, 1 is a pulse power source, 2 is an electrode, 3 is a workpiece,
4 is an effective discharge rate detector, 5 is a maximum value discriminator for determining the maximum value of the effective discharge rate, 6 is a search clock generator, and 7 is a search order sequence circuit for determining the search order of each machining condition. ,8,9,1
0 and 11 are processing fluid pressure, set voltage, pulse duty factor, initial value, upper limit value, lower limit value, search pulse period for the search of the electrode upper and lower hunting period, and a setting range limiting circuit for each factor for determining the search pulse period, respectively;
12, 13, 14, and 15 are settings with terminals 20, 21, 22, and 23 for digitally setting specific values of machining fluid pressure, set voltage, pulse duty factor, and electrode up and down hunting period and outputting them in analog form. Circuits 16, 17, 18, and 19 indicate storage circuits for storing the optimum values of each of the processing conditions described above. Further, a specific example of the search order sequence circuit No. 7 is shown in FIG. In Figure 2,
701 and 702 are serial-parallel shift registers consisting of a set of two 8-bit shift registers for determining the order of initial search for processing conditions; 703 is a shift register of the same type for determining the order of re-search;
04 is an OR gate, one input is given from the rightmost bit of the re-search shift register 703, and the other input is given from the initial search shift register 703.
The output of the OR gate 704 is applied to the leftmost bit of the re-search shift register 703 in a serial input format. 705 is an inverter, 706 is a one-shot multivibrator, and switch 70
7 is input to a parallel type input other than the leftmost parallel type input terminal of the shift register, and at the same time,
A multivibrator 706 is also provided. 70
Reference numerals 8, 709, 710, and 711 are OR gates that output commands for the respective orders of machining fluid pressure, set voltage, pulse duty factor, and electrode vertical hunting period;
4,715 are terminals 8', 9', 10', 1 in Figure 1
1'. OR gate 708, 70
9, 710, 711 inputs are shift register 70
It is connected to each output of 1,702,703.
The terminal 716 is connected when the search for each processing condition is completed.
Setting range limiting circuits 12, 13, 14, 1 for each factor
5 through a connection not shown. A timer 717 performs re-search at predetermined intervals and supplies its output signal to the shift pulse input of the re-search shift register 703.

Next, the operation of the above circuit configuration will be explained. When the machining start switch 707 is turned ON for a short time, an initial search is performed, and the initial value is set as shown in FIG. 3, which will be described later. FIG. 3 is a characteristic diagram showing the relationship between effective discharge rate when machining fluid pressure and set voltage are changed. The set voltage here refers to the set voltage of the electrode gap following servo, and corresponds to the machining gap. The effective discharge rate indicates the proportion of pulses applied to the machining gap that are used for electrical discharge machining, and corresponds to the machining speed. Curves A to E show contour lines of effective discharge rate, with curve E indicating a high effective discharge rate and curve A indicating a low effective discharge rate. In the same figure, to find the highest point _P4 of the effective discharge rate,
As an initial value, the set voltage is first set to 55V, the machining fluid pressure is set to a point _P0 of 0.05Kg/cm ² , and the machining fluid pressure is increased to search for 0.5Kg/cm ² . Then, the machining fluid pressure of approximately 0.3 Kg/cm ² at the point P ₁ where the effective discharge rate is high is determined. Next, set the machining fluid pressure to the previously determined value (0.3
Kg/cm ² ), lower the set voltage, and find the set voltage of about 30V at point P ₂ where the effective discharge is the best. Next, fix the set voltage at 30V and change the machining fluid pressure to find the best effective discharge rate at point _P4 .
Get _P4 . The above describes the interaction between machining fluid pressure and set voltage. A similar interaction occurs between the set voltage and the pulse duty factor, but a detailed explanation will be omitted.

The initial values are set within the machining fluid pressure setting circuit 12, the setting voltage setting circuit 13, the pulse duty factor setting circuit 14, and the electrode hunting cycle setting circuit 15. Initial search registers 701, 702
Since the leftmost side is the “1” level, OR
The output of gate 708 becomes “1” level, and OR
Since the outputs of the gates 709, 710, and 711 are at the "0" level, only the machining fluid pressure is searched. The machining fluid pressure searches for a predetermined range determined by the machining fluid pressure range limiting circuit 8, and during this time, the machining fluid pressure value at which the effective discharge rate is maximum is stored in the machining fluid pressure storage circuit 16 by a maximum value determination circuit (not shown). At the same time as the first machining fluid pressure search is completed, this stored value is set in the machining fluid pressure setting circuit 12, and a machining fluid pressure search end signal is input to the terminal 716. is updated to the "1" level, and the OR gate 709 becomes the "1" level. Since the sequence in this case is determined by the set voltage, the set voltage is searched and the optimum value of the set voltage is determined by the same operation. The search end signal for the set voltage is similarly input from the terminal 716,
The third bit from the left of shift register 701 is updated to the "1" level, the OR gate 710 is updated to the "1" level, and this circuit searches for a duty factor. The same operation is repeated thereafter, and when the fourth shift register from the left of the initial search shift register 702 is reached, the initial search is completed.

Next, when a predetermined period of time has elapsed from the start of machining by the timer 717, a re-search signal is sent as a shift pulse to the shift register at regular intervals, for example, about 5 minutes, and the leftmost bit of the shift register 703 becomes "1" level and becomes AND. The output of the gate 708 becomes "1" and the machining fluid pressure is searched. At the time of re-search, a predetermined range is searched by the search range limiting circuit 8, but the value is set to almost the best value in the initial search, and as the machining depth increases, the amount slightly deviated from the best value is corrected. Since the range is narrower than the initial search, for example, it is best to search 2 to 3 steps above and below the value found in the initial search.If this is widened, the machining efficiency will be reduced. becomes. At the same time as the machining fluid pressure search ends, a machining fluid pressure search end signal (not shown) is given to the timer 717 and the shift register 703
Set the second bit from the left to the "1" level and search for the set voltage.

Machining example Electrode material: Copper-tungsten alloy Workpiece material: Cemented carbide Machining Pulse current: 40A (peak) Pulse width: 2μs Under the above machining conditions, a conventional electrical discharge machining machine can achieve a machining speed of 3 mm ³ /min. I was able to get it.

As described above, during electric discharge machining, the present invention repeats the above machining conditions in a predetermined order based on the interaction characteristics of the machining conditions such as machining fluid pressure, set voltage, pulse duty factor, and electrode vertical hunting period. Since this electric discharge machine control device is equipped with an initial search order sequence circuit for searching and a re-search order sequence circuit for searching the machining conditions in a predetermined order at predetermined time intervals, the material of the electrode and workpiece, The machining efficiency is improved even if the shape changes each time the machine is machined, and the operator does not need to be highly skilled in operating the electrical discharge machining machine, so it is easy to operate.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention;
FIG. 2 is a detailed circuit diagram showing a part of FIG. 1, and FIG. 3 is an electrical discharge machining characteristic diagram illustrating the operation of the present invention. DESCRIPTION OF SYMBOLS 1... Pulse power supply, 2... Electrode, 3... Workpiece, 4... Effective discharge rate detector, 5... Maximum value discriminator, 6... Search clock generator, 7... Search order sequence circuit , 8... Machining fluid pressure range limiting circuit, 9... Setting voltage range limiting circuit, 10... Pulse duty factor range limiting circuit, 11... Electrode upper and lower hunting range limiting circuit, 12... Machining fluid pressure setting circuit , 13... Setting voltage setting circuit, 14
...Pulse duty factor setting circuit, 15...
...Electrode upper and lower hunting period setting circuit, 16,1
7, 18, 19... Memory circuit, 701, 702...
...Shift register for initial search, 703...Shift register for re-search, 704, 708, 709, 7
10,711...OR gate, 717...timer.

Claims (1)

[Claims] 1. In an electric discharge machine that performs machining by intermittent arc discharge by supplying machining fluid and machining pulses to a gap in which an electrode and a workpiece are arranged facing each other, a pulse power supply that supplies the machining pulses and a detector that detects the effective discharge rate of the machining pulse applied to the machining pulse, a maximum value determination circuit that determines the maximum value of the effective discharge rate, machining fluid pressure, set voltage, duty factor, and upper and lower hunting of the electrode. Each setting circuit is provided for each processing condition such as cycle and searches by gradually changing each processing condition from the initial value, and when each processing condition is changed by each setting circuit, a signal is sent from the maximum value judgment circuit. a memory circuit that stores the machining conditions that maximize the effective discharge rate; a setting range limiting circuit that predetermines the initial value, upper limit, lower limit, and search cycle of the search by each of the setting circuits; An initial search circuit section generates a signal to perform an initial search for each of the above-mentioned processing conditions in a predetermined order for each condition at the start of processing; An electric discharge machine control device comprising: a search order sequence circuit comprising a re-search circuit section that generates a signal for repeating the search.