JPH0459092B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a wire electric discharge machining apparatus in which a machining power source and a current-carrying cable can be selected according to machining conditions.

[Background of the invention]

Wire electrical discharge machining equipment is mainly used for machining molds, and the performance of wire electrical discharge machining equipment has been improved in line with the recent shortening of delivery times and higher precision of molds, but especially for rough machining. It is important to simultaneously improve the machining speed during finishing and improve the machined surface roughness during finishing.

FIG. 3 shows a conventional general wire electric discharge machining apparatus. In Fig. 3, workpiece 1 and wire electrode 2
The machining gap formed by the two is filled with machining liquid, and the wire electrode 2 is sent out from the supply reel 3, passes through the reels 4 and 5, and the wire guides 7 and 8, and is wound onto the take-up reel 6. The wire electrode 2 thus travels along a predetermined path and is given a constant tension. The wire electrode 2 is energized using the energizing terminal 1.
Perform steps 3 and 14. and wire guide 7,
8 and energizing terminals 13 and 14 are guide holders 9 and 10.
The machining liquid nozzle 11, 1 is attached to the outside of the
2 is installed. Workpiece 1 and wire electrode 2
In this case, discharge energy is supplied from a first machining power source 15 for rough machining and a second machining power source 16 for finishing machining to each power source via common energizing cables 25 and 26. Each processing power source 25, 26 includes a DC power source 17, 21, a switching element 18, 22,
It is composed of resistors 19 and 23 and pulse control circuits 20 and 24.

In such wire electric discharge machining equipment, during rough machining at high machining speeds, the rise and fall times of the electric discharge machining current are shortened to make the peak current a high value, and at the same time, in order to ensure sufficient pulse rest time, the current is turned off. It is necessary to lower the inductance of the cables 25 and 26. On the other hand, during finishing machining, the resistor 23 is set to a higher value than the resistor 19 of the first machining power source to lower the peak current. but,
If a coaxial cable or the like is used to lower the inductance of the current-carrying cables 25 and 26, the capacitance (stray capacitance) will increase, and during finishing machining, the energy stored in the capacitance 27 of the current-carrying cable will be released during discharge in the machining gap. , the discharge current from the capacitance 27 is superimposed on the pulse current set for finishing machining, resulting in an undesirable increase in the discharge machining current. As a result, the machined surface roughness may not be less than 3 to 5 μmRmax.

In order to deal with this problem, JP-A-59-73226 proposes that during rough machining and finishing machining, energized cables that are suitable for each machining condition are used, and during finishing machining, low inductance cables used for rough machining are replaced with electromagnetic cables. It is disclosed that the capacitance of the current-carrying system during finishing processing is reduced by cutting off the power using a switch and conducting the current through another low-capacitance cable. However, in rough machining, several tens to several
Electromagnetic switches that cut off current-carrying cables for rough machining use a pulsed current with a peak current value of several hundred amperes at a frequency of 100 kHz, so the contact area of the contacts is larger and the contact pressure is lower than those normally available on the market. This necessarily increases the external dimensions of the electromagnetic switch, making it difficult to install it near the machining gap. Therefore, it is not possible to completely eliminate the influence of the capacitance of the current-carrying cable for rough machining during finishing, and there is a limit to the improvement in machined surface roughness. Furthermore, because the electromagnetic switch is a special specification product with high frequency and large capacity, it is expensive and there are difficulties in managing the lifespan and reliability of the contacts.

[Purpose of the invention]

The purpose of the present invention is to solve the problems of the prior art as described above, and to provide a wire that has a simple and inexpensive configuration, improves the machining speed during rough machining, and can obtain good machined surface roughness during finishing machining. An object of the present invention is to provide an electrical discharge machining device.

[Summary of the invention]

In order to achieve the above object, in the present invention, discharge energy is supplied to the workpiece and the wire electrode by at least two machining power supplies selected according to the machining conditions and a dedicated energizing cable for each power supply,
In a wire electrical discharge machining device that processes a workpiece by intermittently generating electrical discharge in a machining gap formed between a workpiece and a wire electrode, (a) a wire is connected to the tip of each energizing cable 28, 29 dedicated to each power source; Upper current-carrying terminals 30, 32 and lower current-carrying terminals 31, 33 formed of conductors are provided, and the upper current-carrying terminal is located above the workpiece 1, and the lower current-carrying terminal is located below, respectively, with the wire electrode 2 in between. By arranging them so that they face each other at a distance or in parallel on one side of the wire electrode, and (b) by moving these current-carrying terminals, one power-carrying terminal for the power supply can be connected to the wire electrode. When 30 and 31 are in contact, energizing terminal moving means 34 to 40 switch the other power supply energizing terminals 32 and 33 to an open state.
The structure shall be equipped with the following.

In the wire electrical discharge machining apparatus of the present invention configured as described above, it is possible to select an appropriate machining power source and current-carrying cable during rough machining and finishing machining by moving the current-carrying terminal, and also to select an appropriate machining power source and current-carrying cable during rough machining and finishing, respectively, by moving the current-carrying terminal. and the wire electrode, the influence of unused cables on the electrical discharge machining current is completely eliminated. In addition, there is no need for a special electromagnetic switch to connect or disconnect the energized cable.
The current-carrying terminal moving function can be easily incorporated into the current-carrying part of the wire electrode.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIG.

The wire electrode 2 is connected to the supply reel 3 - reel 4 - wire guides 7, 8 - as in the conventional example shown in FIG.
It runs along the reel 5-take-up reel 6 path and is given a constant tension. In the machining gap formed between the workpiece 1 and the wire electrode 2, a machining fluid nozzle 1 attached to the outside of the guide holders 9 and 10 is provided.
1 and 12 are filled with machining fluid.

A first machining power source 15 for rough machining is connected to the workpiece 1 and upper and lower power terminals 30, 31 via a rough machining energizing cable 28, while a second machining power source 16 for finishing machining is connected to the workpiece 1 and the upper and lower current-carrying terminals 3 via the finishing processing current-carrying cable 29.
2,33. Here, a low-inductance cable such as a coaxial cable is used as the current-carrying cable 28 for rough machining, and a low-capacitance cable with sufficient distance between wires is used as the current-carrying cable 29 for finishing. Processing power supply 1
The internal configurations of 5 and 16 are the same as those shown in FIG. 3, and illustration thereof is omitted. The current-carrying terminals 30, 31 and 32, 33 are made of a highly hard conductive material such as tungsten and are formed into rod shapes. The lower current-carrying terminals 31 and 33 are held inside the insulating holder 35 in a similar manner. The insulating holders 34 and 35 are cylindrical bodies provided with a radial hole through which the wire electrode 2 is passed, and are slidably installed inside the lateral holes of the guide holders 9 and 10 and the machining fluid holders 11 and 12. One end of the insulating holders 34 and 35 is connected to the machining liquid nozzles 11 and 12 by a holder 36,
The current-carrying terminals 30 and 32 and 31 and 33 are connected to the movable parts of fixed current-carrying terminal moving actuators 38 and 39 via terminals 37, respectively.
The insulating holders 34 and 35 holding the holder 3
6, 37 and actuators 38, 39 constitute an energizing terminal moving mechanism. The actuators 38 and 39 may be hydraulic cylinders or solenoids, and are operated by signals from a control section (not shown) to move the insulating holders 34 and 35 to the left and right in the figure. As a result, the current-carrying terminals 30, 31 for rough machining
Either one of the energizing terminals 32 and 33 for finishing is brought into selective contact with the wire electrode 2, and the other is separated from the wire electrode 2, thereby switching between the machining power supplies 15 and 16 and the energizing cables 28 and 29. It is structured as follows.

During rough machining, the rough machining current-carrying terminals 30 and 31 are in contact with the wire electrode 2, and the finishing machining current-carrying terminals 32 and 33 are separated from the wire electrode 2, as shown in FIG. In this state, rough machining is performed by discharge energy supplied from the first machining power source 15 for rough machining via the low inductance cable 28.

During finishing, the actuators 38 and 39 move the insulating holders 34 and 35 and the current-carrying terminals 30, 31, 32, and 33 held thereto to the left in the figure, and the rough-processing current-carrying terminals 30 and 31 are connected to the wires. The wire electrode 2 is separated from the wire electrode 2, and the finishing current-carrying terminals 32 and 33 are brought into contact with the wire electrode 2. Then, finishing machining is performed using discharge energy supplied from the second machining power supply 16 for finishing machining via the low capacitance cable 29. At this time,
Since the low inductance cable 28 is completely isolated from the electrode wire 2, the low inductance cable 28 has no influence on the electrical discharge machining current.

Next, another embodiment of the present invention will be described with reference to FIG. To simplify the explanation, only the periphery of the upper current-carrying section is shown in FIG. 2, but the lower current-carrying section also has a similar configuration. In this embodiment, an energizing terminal moving actuator 38 is fixed to an insulating holder 40 provided above the guide holder 9, and a finishing energizing terminal 32 is attached to the movable part of the actuator 38, thereby constructing an energizing terminal moving mechanism. The current-carrying terminal 30 for rough machining is fixed to the guide holder 9. The solid line in FIG. 2 shows the state during finishing machining, in which the finishing energizing terminal 32 is in contact with the wire electrode 2, and the rough machining energizing terminal 30 is separated from the wire electrode 2.

During rough machining, the finishing machining current-carrying terminal 39 is moved to the left by the actuator 38, as shown by the dotted line in FIG. Then, the finishing current-carrying terminal 32 is separated from the wire electrode 2. The wire electrode 2, which had been pushed by the current-carrying terminal 32 for finishing, returns to the position shown by the dotted line, and the current-carrying terminal 3 for rough-processing returns to the position shown by the dotted line.
Contact with 0. In this embodiment, by moving the finishing terminal 32, the processing power sources 15, 16 and the energizing cables 28, 2 shown in FIG.
9 switching is performed.

In the two embodiments described above, the current-carrying cable is switched and connected during rough machining and finish machining, but even if the low capacitance cable for finishing machining is connected during rough machining, the electrical Since this has no effect on the finishing process, the current-carrying terminal for finishing may be left in contact with the wire electrode, and only the rough-processing current-carrying terminal may be brought into contact with and separated from the wire electrode.

In addition, in the above embodiment, the case was explained in which two types of machining power supplies and energizing cables for rough machining and finishing machining are switched. It is clear that even when switching between three or more types of processing power sources and energizing cables, such as adding a processing power source that supplies pulsed current and a energizing cable, this can be done by providing a energizing terminal moving mechanism for each energizing terminal. .

In addition, in the above embodiment, the upper and lower current-carrying terminals 32 and 33 are brought into contact with the wire electrode 2 during the finishing process to energize it. However, an energizing terminal for finishing may be provided only on either the upper or lower side.

〔Effect of the invention〕

According to the present invention, it is possible to select an appropriate machining power source and energizing cable for different machining conditions such as rough machining and finishing machining, and to connect and disconnect the energized cable to the energized part of the wire electrode. Because it is carried out in the finishing process, it is completely unaffected by the capacitance of the current-carrying cable used in the rough machining.
Since an undesirable increase in the electric discharge machining current due to the capacitance of the current-carrying cable is avoided, the machining speed can be increased during rough machining, and the machined surface roughness can be improved during finishing machining.

Furthermore, since the connection and disconnection of the energizing cable can be carried out simply by moving the energizing terminal, it can be realized with a relatively simple structure and at low cost, and maintenance is also easy.

[Brief explanation of the drawing]

FIG. 1 is a partial cross-sectional configuration diagram of an embodiment of the present invention, FIG. 2 is a cross-sectional diagram showing only the vicinity of the upper current-carrying part of another embodiment of the present invention, and FIG. 3 is a diagram of a conventional example. It is a block diagram shown in a partial cross section. 1...Workpiece, 2...Wire electrode, 15...Machining power supply for rough machining, 16...Machining power supply for finishing machining,
28... Current carrying cable for rough processing, 29... Current carrying cable for finishing processing, 30, 31... Current carrying terminal for rough processing, 32, 33... Current carrying terminal for finishing processing, 3
4, 35, 36, 37, 38, 39, 40... energizing terminal moving mechanism (34, 35, 40... insulation holder, 36, 37... holder, 38, 39... actuator).

Claims (1)

[Claims] 1. Supplying discharge energy to the workpiece and the wire electrode through at least two machining power supplies selected according to the machining conditions and a dedicated energizing cable for each power supply,
In a wire electrical discharge machining device that processes a workpiece by intermittently generating electrical discharge in the machining gap formed between the workpiece and the wire electrode, (a) each energizing cable 28 dedicated to each power source;
Upper current-carrying terminals 30, 32 and lower current-carrying terminals 31, 33 each formed of a conductor are provided at the tip of the workpiece 29, and the upper current-carrying terminal is located above the workpiece 1 and the lower current-carrying terminal is located below the workpiece 1.
(b) By moving these current-carrying terminals, they are arranged so that they face each other with a certain distance between them, or are arranged in parallel on one side of the wire electrode, and (b) by moving these current-carrying terminals,
One power supply terminal 3 for each wire electrode
When terminals 0 and 31 are in contact, current terminal moving means 34 to 40 are provided for switching the other power supply terminals 32 and 33 to an open state. A wire electrical discharge machining device characterized by: