JPS6013775B2 - Electric discharge machining equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electric discharge machining apparatus that performs machining by applying electric discharge to a minute gap between an electrode and a workpiece.

In conventional electrical discharge machining equipment, the machining gap is widened by causing opposing electrodes or workpieces to perform reciprocating motion, allowing flow of machining fluid to flow in and out, increasing the effect of eliminating machining shoulders and gas, and achieving stable machining. It is proposed that.

Normally, during this reciprocating motion, the gap is controlled to be wider than the discharge gap. . When the machining gap widens due to movement, the electric discharge is interrupted, and as the number of reciprocating movements increases, the average machining speed decreases. That is, since the reciprocating motion is normally performed about once per second, the discharge is stopped for about 1'2 to 1/3 of the total machining time. In view of this point, the present invention controls the machining gap so that electric discharge continues even when the machining gap widens by applying a magnetic field to the machining gap.

By applying a magnetic field to the machining gap, the machining gap becomes substantially susceptible to electrical discharge. Therefore, by increasing the magnetic field strength that acts when the gap widens, the easy discharge state of the gap is maintained and the discharge continues.

The present invention will be described below with reference to an embodiment of the drawings. Reference numeral 1 denotes an electrode, which is formed into a processed shape by press forming, cutting forming, electroplating forming, etc., and faces the workpiece 2 while maintaining a minute gap. Process.

3 is a power source that supplies machining pulses between the electrode 1 and the workpiece 2; the machining gap between the electrode 1 and the workpiece 2 is provided in a machining liquid such as water or oil;

5, the machining fluid is sprayed and supplied.

Reference numeral 6 denotes a magnet coil that causes the electrode to perform reciprocating motion in the direction of the opposing axis (Z-axis).When excited, the movable plate 8, which is always under pressure, is attracted by the spring 7, and when the excitation current is turned off, the plate 8 is moved by the pressure of the spring 7. By this, the movable plate 8
is fixed to the electrode support shaft 19, so that the electrode 1 moves reciprocally.

18 is a feed motor that gives Z-axis feed to electrode 1 according to the progress of machining, and 91, 92, 93...... are magnetic heads inserted in the void formed in electrode 1, and the magnetic head is generated by coil excitation. The magnetic field is arranged in a distributed manner over the entire electrode so that it acts locally on a minute portion of the machining gap, and each is provided so as to be switched and excited.

Reference numeral 10 denotes a rotary switch, which repeats reciprocating motion by intermittently supplying the current applied to the terminal 11 to the coil 6 by sequentially contacting and conducting the rotating contacts of fixed contacts arranged on the circumference.

12 is a magnetic field generating head 91, 92, 93...
With the switch, the fixing point is set to each head coil 91, 9.
2, 93, . . . , and the excitation current supplied to the terminal 13 is switched by sequential contact conduction of the rotary contacts.

14 is another rotary switch, and valve 1 is connected to the control current from terminal 5 into the machining fluid supply circuit by pump 5.
6, and also controls the opening and closing of valves. The rotary switches 10, 12, and 14 described above have their rotary contacts engaged with the rotating shaft of the motor 7, so as to perform synchronous switching corresponding to the rotational speed of the motor 17. Reference numerals 20 and 21 designate X-axis and Y-axis feed motors on a vertical plane for moving the workpiece 2, which are controlled by an NC control device 22 for each axis feed motor that controls the machining feed.

Electric discharge machining is performed by supplying pulses from a machining power source 3 to a gap where the electrode 1 and the workpiece face each other with a minute gap, and repeating the pulse discharge via the supplied machining fluid.

During machining, the motor 17 rotates at an appropriate speed to control on/off the current flowing from the terminal 11 to the coil 6, and the attractive force of the coil 6 and the repulsive force of the spring 7 actuated by this continuous excitation current cause the electrode 1 to 4 performs reciprocating motion in the Z-axis direction.

The reciprocating stroke can be arbitrarily controlled by adjusting the gap between the movable plates 8, and is determined by the cleaning effect of the machining gap. In other words, if the machining gap is widened by reciprocating motion, machining particles, gas, etc. generated by electric discharge can be easily removed, but
If the gap becomes too wide, it will be difficult to generate electric discharge, so the stroke should be controlled to the minimum. When the coil 6 is energized and the electrode 1 is raised by reciprocating motion, one of the magnetic field generating heads 91, 92, 93, etc. provided on the electrode 1 is energized by the rotary switch 12, which rotates synchronously, for processing. It acts by generating a local magnetic field in the gap. Note that since the electrode 1 is usually made of a non-magnetic or weakly magnetic material such as copper, silver, graphite, silver tungsten, etc., it is possible to easily apply the required magnetic flux to the machining gap between the electrode 1 and the workpiece 2, which is mainly made of iron. I can do it.

The magnetic field to be generated is usually on the order of 50 to 150, and the application of this magnetic field facilitates the generation of pulsed discharge.
Therefore, even if the gap is widened by reciprocating control, it is possible to widen the gap by synchronously generating a magnetic field of the required strength and repeating the pulse discharge in the gap. Discharge can be continued without interruption. In the machining gap widened in this way, machining fluid flows well in and out, and the effect of removing machining shoulders, generated gas, discharge decomposed carbon, etc. is enhanced. Further, as in the embodiment, the valve 16 is opened by the changeover switch 14 which rotates synchronously with the machining liquid to be injected from the nozzle 4 into the machining gap, and the gap is widened by increasing the amount of machining liquid supplied from the pump 5 and injecting it. This increases the flow of machining fluid and makes it possible to extremely effectively remove machining debris and clean gaps. In this way, reciprocating motion is performed on the electrode, and this motion is repeated in sync. A magnetic field is applied to the machining gap, and by controlling the magnetic field strength, a pulse discharge is generated repeatedly even when the gap widens due to reciprocating motion. By controlling the electric discharge machining so that it is not interrupted, the effect of removing machining debris etc. is excellent, and stable and efficient machining can be continued without reducing the machining speed.

The magnetic field acting on the machining gap is generated by magnetic field generating heads 91, 92, 93, . . . distributed over the entire electrode surface.・・・．・A local magnetic field is applied to a part of the machining gap, and the position of the application is sequentially switched and moved by the synchronization switch 12 for each reciprocating movement, thereby controlling the point of discharge generation in the machining gap and creating a discharge column. The movement can be controlled.

By controlling the movement of the discharge point, machining can proceed throughout the machining gap, allowing stable machining with high precision, and also making it possible to eliminate machining shoulders extremely easily, increasing the gap cleaning effect and preventing arcs and short circuits. It is possible to perform extremely high-speed, high-efficiency machining without any problems. The movement of the local magnetic field may be controlled to move in a predetermined order in a predetermined direction, but the movement of the local magnetic field can be adaptively controlled depending on the state of the machining gap. Furthermore, by controlling the excitation current applied to the terminal 13, the magnetic field strength can be adaptively controlled. Z, that is, the movement of the magnetic field, can not only be moved sequentially from one neighbor to the other of multiple magnetic poles, but also can be moved here and there over the entire machining gap, and the moving part can be moved according to the discharge state so that stable machining can be obtained. You can move it while making decisions.
The movement of the magnetic field can be effected by moving one or more magnetic poles on the machined surface by NC control, copying control, or other control devices. Depending on the processing mode, the magnetic field generation device may be provided on the workpiece side or around the processing gap, and may be constructed of permanent stone. Further, the working magnetic field can be configured to be induced into the machining gap by a magnetic iron core. The relative movement of the electrode 1 and workpiece 2 during processing for processing feed can be performed not only by the motor 18 in the Z-axis direction 2 but also by the motors 20 and 21 in the X-Y plane. The movement control signal can be used not only by the NC control device 22 but also by a copying control device, a sequence control device, and other automatic control devices, and the electrode and workpiece can be made to perform an eccentric rotation movement without rotating on its own axis.
A variety of other devices can be used, such as a head shaking motion, a miso-suri motion, a device that moves a predetermined amount in a star shape from the center position, and the movement is controlled to move a fixed distance at a constant triad) In addition, depending on the state of the machining gap, 3
For example, it is possible to detect the voltage, current, impedance change, etc. in the gap and perform servo control as a signal to perform follow-up control in machining.

In addition to the motor, the feed can be controlled using a hydraulic cylinder, elastic control of a spring, or electromagnetic force.
In addition to using a full-shaped electrode for the 4 electrodes, pipes,
It is also possible to perform shape processing using simple electrodes such as rods and plates, or by using them in combination and controlling the shape feed in two or three dimensions. The reciprocating motion device can be controlled by an external motor, controlled by a hydraulic cylinder, or configured using a magnetostrictive and electrostrictive element. The reciprocating movement period, stroke, etc. can be changed as appropriate, and can be changed according to the discharge state to always perform optimum reciprocating control. Reciprocating motion is not limited to the Z-axis in the electrode facing direction, but can be applied in the X-axis, Y-axis, and other directions of the opposing vertical plane, and can be applied in multiple directions in unison. Reciprocating motion can also be applied to the workpiece.
Also, the magnetic field that acts in synchronization with this reciprocating control is generated and acts even when the machining gap is at a narrow predetermined discharge gap.
Control can also be performed to increase the strength of the working magnetic field when the gap widens due to reciprocal motion, and control can be performed so that the discharge is not interrupted by the enhanced magnetic field.

The strength of the working magnetic field can be controlled by increasing the excitation current or by switching the winding ratio of the magnet, or by moving or rotating the electromagnet or permanent magnet. The acting magnetic field may be a magnetic field that acts not only locally on the machining gap but also on the entire gap. Furthermore, for the synchronous control of the reciprocating movement and the working magnetic field, or the synchronous control of the reciprocating movement, the working magnetic field, and the machining fluid injection, in addition to using a rotary sliding door, synchronous control by an electronic circuit or other control circuit devices can be used. .

In addition, the machining liquid injection nozzle 4 is provided with a plurality of holes around the machining gap, and the liquid can be injected into the gap from each direction simultaneously or by switching, and by linking the injection force with reciprocating control, it is possible to spray the liquid into the gap from various directions. The exclusion effect can be enhanced.

Furthermore, if a jet suction hole can be formed in the electrode or the workpiece, the effect will be further enhanced. Next, to explain an experimental example, a steel workpiece was machined using a nodal electrode.

The electrode processing area was 50 cm, and a plurality of magnetic field generating heads were arranged at 15 side corners of the flat electrode area of 50 cm, and the generated working magnetic field strength was variably controlled to a maximum of 1100 mm and a minimum magnetic field of 550 mm. Processing pulse conditions are 7, h=]0 ms during pulse
, On hiatus 7. ff=4boards, wave height lp=40A,
The reciprocating motion cycle was 1 time/second, and the stroke was 0.08 skin. The working magnetic field strength is 5$, lesif, when the discharge gap is normal.

When the gap widened due to the movement, the magnetic head was controlled to increase in 110 steps, and each magnetic head was switched in synchronization to move the working magnetic field. When a processing depth of 50 skin was processed, the processing time was 3 gluing hours, and the processed surface roughness was approximately 20 French Rmax.

When only reciprocating motion was performed without applying a magnetic field, the machining time required 7 hours. In this way, the traditional recipe o
Depending on the control, the actual machining time ratio will be 1'2 to 2', but according to the present invention, by the action of the magnetic field and its control, electric discharge can be generated even during reciprocating motion, and machining can be stopped. Since the process can be repeated without interruption, the machining speed can be increased two to three times compared to the conventional method. As explained above, the present invention can constantly generate electric discharge in the machining gap even during reciprocating motion to continue machining, and by controlling the reciprocating motion, the machining shoulder in the machining gap is always well eliminated, and there is no short circuit or arc. Stable electric discharge machining can be performed, thereby increasing machining speed and significantly improving machining efficiency.

[Brief explanation of the drawing]

The drawing is a sectional side view of a device according to an embodiment of the present invention. 1 is an electrode, 2 is a workpiece, 3 is a processing power source, 4 is a processing liquid injection nozzle, 5 is a pump, 6 is a magnet coil, 7 is a spring, 8 is a movable plate, 91, 92, 93...・・・・・・
・Magnetic head, 10, 12, 14 are rotary cutters, 1
1, 13, 15 are excitation power supply terminals, 16 is a control valve, 1
8, 20, 215 feed motor.

Claims (1)

[Scope of Claims] 1. An electric discharge machining device that processes an electrode and a workpiece by applying pulse discharge into a machining gap where they face each other, comprising: a motion control device that performs relative reciprocating motion between the electrode and the workpiece; An electrical discharge machining system comprising: a magnetic field generating device that generates a magnetic field in a gap; and a synchronous control device that controls the magnetic field generated by the magnetic field generating device in synchronization with the reciprocating motion of the motion control device. Device. 2. The discharge according to claim 1, wherein the synchronous control device turns on the working magnetic field of the magnetic field generator when the machining gap widens due to reciprocating motion, and turns off the working magnetic field when the gap narrows. Processing equipment. 3. The discharge according to claim 1, wherein the synchronous control device performs control to enhance the working magnetic field of the magnetic field generator when the machining gap widens due to reciprocating motion, and to reduce the working magnetic field when the gap narrows. Processing equipment. 4. The electrical discharge machining apparatus according to claim 1, wherein the reciprocating motion control device causes reciprocating motion in the direction in which the electrode and the workpiece are opposed, in the direction of the opposed vertical surface, or in the direction of the opposed direction and the direction of the opposed vertical surface. 5. The electrical discharge machining apparatus according to claim 1, wherein the magnetic field generating device generates a local magnetic field in a part of the machining gap and moves the magnetic field acting part.