JPH0487720A - Electric discharge machining device - Google Patents

Abstract

PURPOSE:To increase a ratio at which machining speed is increased when peak current value of pulse current is increased by sending a machining pulse signal from a distributor into one of a plural number of pulse power supply, and allowing flow of pulse current having a waveform subjected to pulse power supply setting, between electrodes. CONSTITUTION:An electrode 1 and a workpiece 2 are approached to each other until electric discharge occurs by moving them relatively. Machining pulse signal P and pulse power supply selection signal A/B are output into a distributor 7 from an oscillator 33 which observes voltage VG between electrodes, and a first or second pulse power supply 5 or 4 is selected to output machining pulse signal YB or YA. This signal turns on the first or second pulse power supply 5 or 4 and a switch 22 or 16 to allow flow of pulse current between electrodes through a machining feeder 6. After pulse current is allowed to flow, a signal YO from the oscillator 33 is stopped and a switch 11 of DC power supply 3 is turned off to stop application of DC voltage between electrodes. This operation is repeated and pulse current is allowed to flow between electrodes to perform electric discharge machining.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention moves an electrode and a workpiece while facing each other, applies a DC voltage between the electrode and the workpiece, and generates a pulse current. The present invention relates to an electric discharge machining apparatus that processes a workpiece by applying current, and particularly to an electric discharge machining apparatus that can increase the rate at which machining speed increases when the peak current value of a pulse current is increased.

[Sub^ Technique] Figure 4 is a block diagram showing a conventional electrical discharge machining device.
In the figure, (1) is the electrode, (2) is the workpiece, and (3)
is a DC power supply that generates a no-load voltage between the electrode (1) and the workpiece (2) serving as the other electrode, that is, between the electrodes, and includes a DC variable voltage source (10), a switching element such as a transistor (hereinafter , switch) (11), a switch circuit in which a variable resistor (12) and a reverse current blocking diode (13) are connected in series, and a flywheel diode (14)
It is connected to the electrode (1) and the workpiece (2). (6) is a machining feeder having a direct current resistance R and an equivalent inductance L representing the entire machining circuit, and a pulse power source ( 27) to the electrode (1) and the workpiece (2), for example, a coaxial cable is used.

The pulse power supply (27) is a DC voltage source (28) with a voltage of V
, a switch circuit in which a switch (29) and a reverse current blocking diode (30) are connected in series, and a flywheel diode (
31) and a surge absorption circuit of a surge absorption voltage source (32). (8) is an oscillator that operates the DC power supply (3) to generate a no-load voltage between the electrodes, and also generates a voltage between the electrodes. This device measures and detects the occurrence of electrical discharge, generates a machining pulse signal P, and inputs and outputs various machining conditions. (9) is a condition setting device that sets processing conditions for the oscillator (8).

Next, a procedure for applying a pulse current between the electrodes during electrical discharge machining in the conventional electrical discharge machining apparatus shown in FIG. 4 will be described.

Send signal Y from the oscillator (8) to the switch (11) of the DC power supply (3), and turn on the switch (11) (hereinafter referred to as ON).
) and apply a DC voltage between the electrodes.

Note that before this, the machining conditions DN sent in advance from the condition setting device (9) are latched in the latch circuit of the oscillator (8), and this data DN is sent from the oscillator (8) to the DC power supply (3). The values of the DC variable voltage source (lO) and the variable resistor (12) are set.

Thereafter, the electrode (1) and the workpiece (2) are moved relatively to each other until electric discharge occurs. When discharge occurs, the oscillator (8) that monitors the interelectrode voltage v6 outputs a processing pulse signal P, which is a control signal that controls the timing of pulsed current application, and the switch (29) of the pulsed power supply (27) is turned on, and a pulse current is passed between the electrodes through the processing feeder (6). After applying the pulse current, stop the signal Y from the oscillator (8) and turn on the DC power supply (3).
) is turned off (hereinafter referred to as OFF) to stop applying the DC voltage between the electrodes. After the pulse current is applied, the signal Y is sent from the oscillator (8) to the switch (11) of the DC power supply (3) again after a period of time.
The switch (11) is turned on to apply a DC voltage between the electrodes.

The above operation is repeated and a pulse current is passed between the electrodes to perform electrical discharge machining.

FIG. 5 is a time chart showing the above procedure, and shows the inter-electrode voltage V. and interelectrode pulse current 1. This is an example of the DC power supply signal Y and the processing pulse signal P.

After DC voltage is applied between the electrodes from the DC power supply (3), when discharge occurs, the interelectrode voltage V6 changes from the no-load voltage to the arc voltage V
Move to A. At the same time, a DC current starts flowing between the electrodes from the DC power supply (3).

The oscillator (8) is the interelectrode voltage■. When the change in is observed and the occurrence of electric discharge is detected, a machining pulse signal P is output immediately after that.

The pulse width of the machining pulse signal P is from the time when the DC voltage is applied between the electrodes to the time t, if the discharge occurs later than t, and if the discharge occurs before time tD, the pulse width is t.
adjusted to l.

The processing pulse signal P is sent to the switch (2) of the pulse power supply (27).
9) and set the peak current value "P2" or "IP" respectively.
A pulse current of 1 is applied between the electrodes.

Next, the waveform of the pulse current will be explained with reference to FIG. The maximum value of the pulse current is the value obtained by subtracting the arc voltage VA between the electrodes from the voltage V of the DC voltage source (28) of the pulse power source (27), divided by the equivalent resistance R of the processing feeder (6), V - V. ^/R. Current gradient V at time 0
-■ A/L is maximized and increases exponentially with the passage of time, and after the end of the machining pulse signal P, the current value gradually decreases from the peak current value IP until it reaches zero. As a result, the pulse current has a triangular shape. In the examples shown in FIGS. 5 and 6, the peak-current value of the pulse current is IPI with respect to the end time t1 of the processing pulse signal P, and the processing pulse signal P
For the end time t2, the peak current value of the pulse current becomes IF5. Further, the pulse widths of the pulse currents are T2 and T2, respectively.

[Problems to be Solved by the Invention] In the conventional electrical discharge machining apparatus as described above, the peak current value 1p of the pulse current is increased to increase the energy,
In order to increase the amount of machining in one discharge, the end time t of the machining pulse signal P must be delayed, and as a result, the pulse width of the pulse current becomes wider, so the duty of machining time increases and the number of machining increases. It will decrease.

As the duty of machining time increases, the discharge of machining sludge becomes worse and the number of machining operations decreases, so even if the peak current value 1p of the pulse current is increased, the rate at which the amount of machining (machining speed) increases within a certain period of time decreases. The problem was that it became smaller.

The present invention was made to solve this problem, and an object of the present invention is to obtain an electric discharge machining apparatus that can increase the rate of increase in machining speed when the peak current value IP of the pulse current is increased.

[Means for Solving the Problems] The electric discharge machining apparatus according to the present invention moves an electrode and a workpiece relative to each other while facing each other, applies a DC voltage between the electrode and the workpiece, and generates a pulse. In devices that process a workpiece by passing current, each has a DC voltage source with a different voltage, and multiple pulse power supplies supply pulsed current between the electrodes, and multiple pulse power supplies are connected to the electrodes and the workpiece. It is provided with a common machining feeder to be connected and a distributor that distributes a machining pulse signal outputted by detecting the occurrence of electric discharge between the electrodes to i of a plurality of pulse power sources.

[Function] In this invention, a processing pulse signal is sent from a distributor to one of a plurality of pulse power sources each having a DC voltage source with a different voltage and supplying a pulse current between electrodes, and the pulse power source A pulse current having a preset waveform is applied between the electrodes from one pulse power source.

[Example] Hereinafter, an example of the electric discharge machining apparatus according to the present invention will be described.

FIG. 1 is a block diagram showing an embodiment of the present invention. In FIG. 1, (1) is an electrode, (2) is a workpiece, and (3) is an electrode.
) is a DC power supply that generates a no-load voltage between electrodes, and includes a DC variable voltage source (10), a switch (11), and a variable resistor (
12) and a backflow blocking diode (13) in series, and a flywheel diode (14), which is connected to the electrode (1) and the workpiece (2). (6) is the equivalent DC resistance R representing the entire processing circuit
and a processing feeder with an equivalent inductance L, the second
The pulse power source (4) and the first pulse power source (5) are connected to the electrode (
1) and a feeder connected to the workpiece (2). Note that portions with the same symbols as in the above-mentioned diagram N4 indicate the same portions.

The second pulse power source (4) is a DC voltage source (1
5), switch (■6) and reverse current blocking diode (17
) in series, a surge absorption circuit consisting of a flywheel diode (18) and a surge absorption voltage source (19), and a pulse width regulator (2o) that adjusts the ON time of the switch (16). has been done. The first pulse power supply (5) is a DC voltage source (21
), switch (22) and backflow blocking diode (23)
A surge absorption circuit consisting of a flywheel diode (24) and a surge absorption voltage source (25), and a pulse width regulator (26) that adjusts the ON time of the switch (22). ing.

(33) is an oscillator that operates the DC power supply (3) to generate a no-load voltage between the electrodes, measures the voltage v6 between the electrodes to detect the occurrence of discharge, and generates the machining pulse signal P. This is a device that inputs and outputs various processing conditions. (9) is a condition setting device that sets processing conditions for the oscillator (33). (7) receives the processing pulse signal P from the oscillator (33) and the selection signal A/B of the pulse power supply, and receives the processing pulse signal P.
This is a distributor that outputs either a processing pulse signal Yo to the second pulse power source (4) or a processing pulse signal Yh to the first pulse power source (5).

Next, a procedure for applying a pulse current between the electrodes during electrical discharge machining in the electrical discharge machining apparatus which is an embodiment of the present invention shown in FIG. 1 will be described.

Switch (11) from oscillator (33) to DC power supply (3)
A signal Y is sent to the electrode, the switch (11) is turned on, and a DC voltage is applied between the electrodes. Note that before this, the machining conditions DN sent in advance from the condition setting device (9) are latched in the latch circuit of the oscillator (33), and this data D
N is sent from the oscillator (33) to the DC power supply (3) to set the values of the DC variable voltage source (10) and variable resistor (12). Thereafter, the electrode (1) and the workpiece (2) are moved relatively to each other until electric discharge occurs. When a discharge occurs, an oscillator (3
3), the processing pulse signal P and the pulse power selection signal A/B, which are control signals for controlling the timing of energization of the pulse current, are output to the distributor (7), and from the distributor (7), the pulse power supply It is selected to the second pulse power source (4) or the first pulse power source (5) determined by the selection signal A/B, and only one of the machining pulse signal Y or the machining pulse signal YA is output. The machining pulse signal YB or the machining pulse signal YA is supplied from the second pulse power source (4) or the first
The switch (16) or switch (22) of the pulse power source (5) is turned on to apply a pulse current between the electrodes through the processing feeder (6). After applying the pulse current, the signal Y from the oscillator (33) is stopped and the DC power source (3
) is turned off to stop applying the DC voltage between the electrodes.

After the pulse current has been applied, the signal Y is sent from the oscillator (33) to the switch (11) of the DC power supply (3) again after a period of time, and the switch (11) is turned on to apply DC voltage between the electrodes. Apply. The above operation is repeated and a pulse current is passed between the electrodes to perform electrical discharge machining.

Figure 2 is a time chart showing the above procedure, and shows the interelectrode voltage V, interelectrode pulse current I, DC source signal Y, machining pulse signal P, pulse power source selection signal A/B, and machining pulse signals YA and YB. This is an example.

After DC voltage is applied between the electrodes from the DC power supply (3), when discharge occurs, the interelectrode voltage V6 changes from the no-load voltage to the arc voltage V
Move to A. At the same time, a DC current starts flowing between the electrodes from the DC power supply (3).

The oscillator (33) observes the change in the interelectrode voltage (6), and when it detects the occurrence of discharge, immediately outputs the machining pulse signal P.

The pulse power supply selection signal A/B is set to a level at which the distributor (7) is activated to output the machining pulse signal YB from the time when the DC voltage is started to be applied between the electrodes to the time t, or if discharge occurs later than that. If the electric discharge occurs before the above time t, the distributor (7) is operated to transmit the machining pulse signal Y.
The level changes to output A.

The processing pulse signal P output from the oscillator (33) is switched to the processing pulse signal YB or the processing pulse signal YA by the distributor (7), and is switched to the switch (16) of the second pulse power source (4) or the second pulse signal YA, respectively. 1 nokurusu power supply (
5) Turn on the switch (22). As a result, a pulse current having a peak current value IP2 or a peak current value "PI" flows between the electrodes.

Next, the waveform of the pulse current will be explained with reference to FIG. The maximum value of the pulse current flowing between the electrodes from the second pulse power source (4) is the DC voltage source (
15) The value obtained by subtracting the arc voltage VA between the electrodes from the voltage VH divided by the equivalent resistance R of the processing feeder (6) v
-VA/R, and the maximum value of the pulse current flowing between the electrodes from the first pulse power source (5) is
The value obtained by subtracting the arc voltage VA between the electrodes from the voltage V of the DC voltage source (21) in 5) is divided by the equivalent resistance R of the processing feeder (6), which is VL-VA/R. The current gradient at time O is the second
In the case of a pulse current flowing between the electrodes from the pulse power source (4), V - VA/L, and in the case of a pulse current flowing between the electrodes from the first pulse power source (5), VL - vA/L.
are respectively maximized and increase exponentially with the passage of time, and after time t, the second pulse power supply (4
) in the case of a pulsed current flowing between the electrodes, the peak current value IP2 is reached, and in the case of a pulsed current flowing between the electrodes from the first pulsed power source (5), the peak current value IPI is reached.
After reaching , it gradually decreases to zero.

As a result, the pulse current has a triangular shape. In the examples shown in FIGS. 2 and 3, the voltage of the surge absorption voltage source (19) of the second pulse power source (4) and the first Pulse power supply (5
) The voltage of the surge absorbing voltage source (25) is set in advance. Further, the voltage (2) of the DC voltage source (15) and the voltage VL of the DC voltage source (21) are also set in advance so as to obtain the waveform shown in FIG. 3.

Further, the switch (16) of the second pulse power source (4) and the switch (22) of the first pulse power source (5) are turned ON.
The time is adjusted to t by the pulse width adjuster (20) and pulse width adjuster (2B), respectively. These pulse width adjusters (20) and (2B) control the processing pulse signal P.
This is necessary when obtaining a time t that is different from the pulse width of .

The circuit performs general one-shot operation, for example,
A monostable multivibrator is used.

Note that in the above embodiment, the pulse power supply is used for the first and second pulse power supplies.
Although this is the case of two pulse power supplies, there may be three or more pulse power supplies. When the number of pulse power supplies is N (N>2), the pulse power supply selection signal DIDN-1Y-YN is output from the oscillator due to the discharge delay time 1-1 from the DC voltage application start time, and the number of N pulse power supplies is Pulse currents having different peak current values IP1 to 'PN can be switched from the pulse power source to supply current between the electrodes.

For example, if there are three pulse power supplies (N-3), - For example, if discharge occurs later than the discharge delay time tD2, the pulse power supply selection signal Y3 is output, and tD2 and tDl
By outputting Y2 if a discharge occurs between t and 1, and outputting Yl if a discharge occurs before t,1, the pulse power source can be switched and a pulse current can be passed between the electrodes.

Further, the reference for outputting the pulse power supply selection signals Y1 to YN is the discharge delay time t −T from the DC voltage application start time.
However, between DC voltage application DI DN-
1 No-load voltage value ■ after a certain time t from the starter. GI is measured by measuring O and comparing the value with the reference value v -
The GN-1 pulse selection signal Y - YN may be determined and output.

[Effects of the Invention] As explained above, this invention involves relatively moving an electrode and a workpiece while facing each other, and applying a DC voltage and passing a pulse current between the electrode and the workpiece. In electrical discharge machining equipment that processes workpieces, there are multiple pulse power supplies that each have DC voltage sources with different voltages and supply pulsed current between the electrodes, and a common pulse power supply that connects the multiple pulse power supplies to the electrodes and the workpiece. Since we have installed a machining feeder and a distributor that detects the occurrence of electric discharge between the electrodes and distributes the output machining pulse signal to one of the multiple pulse power sources, the pulse width of the pulse current does not have to be wide. , peak current value 1p of pulse current
can be increased, the machining energy is large, and the effect of discharging machining sludge remains the same, which has the effect of increasing the rate at which the machining speed increases.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a diagram illustrating the procedure for applying a pulse current between electrodes during electrical discharge machining of an apparatus according to an embodiment of the invention, and FIG. 3 is a waveform diagram illustrating the waveform of the pulse current in an embodiment of the present invention, FIG. 4 is a block diagram showing a conventional electric discharge machining apparatus, and FIG. FIG. 6 is a waveform diagram illustrating the pulse current waveform of the device shown in FIG. 4. In the figure, (1) is the electrode, (2) is the workpiece, and (3)
is the DC power supply, (4) is the second pulse power supply, and (5) is the first
(6) is a processing feeder, (7) is a distributor, (9) is a condition setting device, and (33) is an oscillator. In addition, in the figures, the same reference numerals indicate the same or corresponding parts. Figure 2 Agent Patent Attorney Muneharu Sasaki Figure 3 Figure 6 Figure 6 Procedural Amendment (Voluntary) W-12□18

Claims (1)

[Claims] Electrical discharge in which an electrode and a workpiece are moved relative to each other while facing each other, a DC voltage is applied between the electrode and the workpiece, and a pulse current is passed to process the workpiece. In the processing device, one DC power supply that generates a no-load voltage between electrodes, a plurality of pulse power supplies each having a DC voltage source with a different voltage and supplying a pulse current between the electrodes, and a plurality of pulse power supplies that generate a pulse current between the electrodes. A common machining feeder connects a power source to the electrodes and the workpiece, and the DC power supply is activated to apply a DC voltage between the electrodes, detect the occurrence of electric discharge between the electrodes, and output a machining pulse signal. An electric discharge machining apparatus comprising: an oscillator; and a distributor that distributes the machining pulse signal to one of the plurality of pulse power sources.