JPH0994719A - Feeding device for electric discharge machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To supply a stable work current to an electrode dispite of the rotation time and rotation-stop time of the electrode mounted on a main spindle. SOLUTION: In providing a feeding ring 24, rotating together with a main spindle 14, and performing discharge work while rotating an electrode 22; a feeding brush 26a and the outer peripheral surface of the ring 24 are contacted, and also a work current is supplied to the electrode 22 via the ring 24. Also, in performing electric discharge work without rotating the electrode 22, the side surface of the ring 24 can be nipped by nipping members 28a and 28b, and also the work current is supplied to the electrode 22 via the ring 24 from a contact member.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply device for an electric discharge machine which discharges a work by means of an electrode mounted on a spindle.

[0002]

2. Description of the Related Art Electric discharge machining is a technique for machining a work into a desired shape by applying a machining voltage between the work and an electrode and utilizing the electric discharge phenomenon generated between the two electrodes. The electric discharge machine performs a discharge in the Z-axis direction while rotating the spindle, that is, the electrode in the machining process, or performs only the Z-axis direction feed without rotating the electrode to perform the electric discharge machining and apply a machining current to the electrode. In order to supply the power, a disk-shaped or ring-shaped power supply plate as a power-supplied member and a power supply brush that contacts the power supply plate are provided at the tip of the main shaft. Generally, when electric discharge machining is performed by rotating an electrode, for example, machining of pores with a diameter of 1 mm or less, thread cutting, and machining while indexing an electrode, a small machining current is supplied to the electrode, while the electrode is not rotated. In the case of processing, a large current is supplied to the electrodes.
Conventionally, a machining current is supplied from a power feeding brush to an electrode via a power feeding plate regardless of whether the electrode is rotated or not.

[0003]

As described above, in the conventional electric discharge machine, in order to constantly supply the machining current from the power feeding brush to the electrode through the power feeding plate to stably rotate the main shaft, the power feeding brush is used. And the power supply plate cannot be sufficiently brought into contact with each other, and the electrical contact resistance between them becomes large. Therefore,
When supplying a large current, excessive Joule heat is generated,
The spindle is thermally deformed and the machining accuracy is reduced. In order to solve this, it is conceivable that the contact pressure between the power supply brush and the power supply plate can be adjusted, but as described above, the same as above when rotating the electrodes to perform electric discharge machining. In order to supply the processing current from the power feeding brush to the electrode via the power feeding plate, the contact pressure between the power feeding brush and the power feeding plate must be set below a certain level, and in order to reduce the electrical contact resistance. It becomes difficult to obtain a desired contact pressure, and there is a limit to reduction of heat generation between the power feeding brush and the power feeding plate when supplying a large current. An object of the present invention is to supply a stable machining current to an electrode mounted on a main shaft regardless of whether the electrode is rotated or stopped.

[0004]

When electric discharge machining is performed without rotating the electrode, the electric power is supplied so that the side surface of the power-supplied member is in contact with the electrode and the machining current is supplied to the electrode via the power-supplied member. It can be solved by providing means. That is,
The present invention provides a power supply device for an electric discharge machine that supplies a machining current to an electrode mounted on a rotatably supported spindle.
A disk-shaped power-supplied member provided at the tip of the main shaft so as to rotate together with the main shaft, and the disk-shaped power-supplied member for supplying a machining current to the electrode via the power-supplied member. A first power supply unit that is in contact with the outer peripheral surface of the member and the power-supplied member are provided so as to be sandwiched, and a side surface of the power-supplied member is sandwiched to supply a machining current to the electrode via the power-supplied member. The gist is a power feeding device of an electric discharge machine including a second power feeding means. Further, the gist of the second power feeding means is a power feeding device of an electric discharge machine including a brake that holds a side surface of the power fed member to stop rotation of the spindle.

[0005]

When electric discharge machining is performed by rotating the electrode, the first power feeding means, which comes into contact with the outer peripheral surface of the disk-shaped power-supplied member provided at the tip of the main shaft, causes the electrode to pass through the power-supplied member. A machining current is supplied to. On the other hand, when electric discharge machining is performed without rotating the electrode, the second contact is made from both sides so as to sandwich the side surface of the disk-shaped power-supplied member provided at the tip of the spindle.
The machining means supplies the machining current to the electrode via the power-supplied member.

[0006]

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. First, referring to FIG. 2, an electrode head 10 of an electric discharge machine equipped with a power supply device of the present invention holds a spindle head 12 so as to be movable in the Z-axis direction in FIG. Electrode 22
Is installed. The electrode head 10 is movably mounted in a horizontal plane by a ram 44 and a saddle 42. That is, the saddle 42 is provided movably in the X-axis direction on the column 40 fixed to the bed 48, and the ram 44 is provided movably in the Y-axis direction on the saddle 42. Further, the workpiece W to be electric discharge machined is immersed in a machining liquid (not shown) in the machining tank 46, and
It is fixed on a table 50 provided on the bed 48. With such a configuration, the electric discharge machine can connect the electrode 22 to the X
A work voltage is applied between the electrode 22 and the work W while being fed in the axial, Y-axis, and Z-axis directions, and the work W is discharge-machined into a desired shape.

Next, referring to FIG. 1, inside the electrode head 10 of the power feeding device of the electric discharge machine according to the present invention, a feed motor 34 as a feed device for moving the spindle head 12 in the Z-axis direction, A feed screw 38 connected to the rotary shaft of the feed motor 34 is provided. The feed screw 38 engages with the nut 36 fixed to the mounting portion 12a of the spindle head 12, and when the feed motor 34 rotates, the spindle head 12 moves in the Z-axis direction, that is, the vertical direction in FIG. Move in the direction.

Bearings 16a, 1 are provided in the spindle head 12.
The spindle 14 is rotatably supported via 6b, and the bearings 16a and 16b have their outer rings fixed to the spindle head 12 by bearing retainers 16c and 16d. Further, a spindle motor 30 for rotating the spindle 14 is provided in the electrode head 10, and the spindle 14 is connected to a rotating shaft of the spindle motor 30 via a coupling 32. Spindle 1
A cylindrical electrode chuck 20 to which an electrode 22 is attached is attached to the tip of the electrode 4 via an electrical insulator 18, and an annular power supply ring 24 is attached to the outer peripheral surface of the electrode chuck 20 as a power-supplied member. There is.

Further, the tip of the spindle head 12 is provided with first and second power feeding means 26, 28 for feeding a machining current to the electrode 22 via the power feeding ring 24. The first power feeding means 26 includes a power feeding brush 26a and an adjusting screw 26.
b, a spring 26c arranged between the power feeding brush 26a and the adjusting screw 26b. The power supply brush 26a is the spring 2
6c and the adjusting screw 26b are urged to contact the outer peripheral surface of the power supply ring 24. In addition, the power supply brush 26a
Is connected to a power supply device (not shown) of the electric discharge machine via an appropriate electric wire (not shown). On the other hand, the second power feeding means 28 includes a pair of holding members 28 a and 28 b provided so as to be able to hold both side surfaces of the power feeding ring 24, and the holding member 28.
A cylinder 28c fixed to the inner surface of the spindle head 12 in order to move the a and 28b toward and away from both end surfaces of the power feed ring 24.
Consists of Here, the cylinder 28c is a well-known cylinder type fluid actuator, and a hydraulic pressure source (not shown).
Alternatively, it is connected to an air source (not shown).

The sandwiching members 28a, 28b are made of a conductive material and are connected to a power supply unit (not shown) of the electric discharge machine via an appropriate electric wire like the power feeding brush 26a. Further, the contact members 28d and 28e attached to the side surfaces of the sandwiching members 28a and 28b on the inner side in the radial direction, which face the power feeding ring 24, reduce electric contact resistance between the holding members 28a and 28b and the power feeding ring 24. It is formed of a material that can make good contact with the power supply ring 24, for example, carbon, and preferably the power supply ring 24 and the contact members 28d and 28e are contacted with each other in a contact area as wide as possible. It is better to

The power supply ring 24 and the holding member 28 are also provided.
It is also possible to configure a brake that stops the rotation of the main shaft 14 by using a and 28b and the cylinder 28c.
In this case, the sandwiching members 28a, 28b have a large frictional force and a small contact resistance to withstand a large pressing force for stopping the main shaft 14, and when contacting the power feeding ring 24, the rotation direction of the main shaft 14 is increased. It is necessary to have a structure that does not shift. Further, the cylinder 28c and the holding member 2
It will be readily understood that 8a, 28b and contact members 28d, 28e need to have considerable strength, respectively.

Next, the operation of the power feeding device according to the present embodiment will be described. First, when the electric discharge machining is started, an appropriate electrode 22 is attached to the electrode chuck 20. When electrical discharge machining is performed while rotating the electrode 22, for example, the diameter is 1 m.
In the case of machining pores of m or less, thread cutting, and machining while indexing the electrode 22, the spindle motor 30 drives the spindle 1
4, while feeding the electrode 22 in the Z-axis direction by the feed motor 34, the electrode 22 is fed from the feeding brush 26a through the feeding ring 24 and the electrode chuck 20.
A machining current is supplied to. On the other hand, when electric discharge machining is performed without rotating the electrode 22, the feed motor 34 feeds the electrode 22 in the Z-axis direction to the cylinder 28.
The clamping members 28a and 28b are urged toward each other by c, and the feeding ring 24 is clamped by the clamping members 28a and 28b to fix the rotation of the main shaft 14 and the electrode 22, and the clamping members 28a and 28b and the contact. From the members 28d and 28e, the feeding ring 24 and the electrode chuck 2
A machining current is supplied to the electrode 22 via 0 and. Electrode 2
When electric discharge machining is performed without rotating 2, the large machining current is generally supplied between the electrode 22 and the work W, but the contact members 28d and 28e and the power supply ring 24 are in good contact with each other. Since the contact resistance between the two becomes smaller,
It becomes possible to supply a large machining current without generating a large amount of heat. In addition, the holding member 2 is held by the cylinder 28c.
If 8a and 28b are urged toward each other, the second
The power supply means 28 can also act as a brake that stops the rotation of the main shaft 14.

[0013]

When electric discharge machining is carried out without rotating the electrode, a second power feeding means for sandwiching the side surface of the disk-shaped power-supplied member and supplying a machining current to the electrode via the power-supplied member is provided. Since it is provided, heat generation during machining with a large current is not taken into account without considering the contact pressure with the first power supply member that contacts and slides on the outer peripheral surface of the power-supplied member, without sacrificing the indexing accuracy or rotation accuracy of the spindle. Can be prevented. Moreover, since an arbitrary contact area can be obtained between the second power feeding means and the power-supplied member, the electrical contact resistance between the two can be sufficiently reduced, and the machining current can be stably supplied to the electrodes. It becomes possible to do. Further, since the second power feeding means can be used not only for supplying the machining current but also as a brake for stopping the rotation of the main spindle, it assists the braking torque of the main spindle and stabilizes the electrode when supplying a large current. Retention can be realized.

[Brief description of drawings]

FIG. 1 is a sectional view of a main part of a power supply device for an electric discharge machine according to an embodiment of the present invention.

FIG. 2 is a front view showing an electric discharge machine equipped with the power supply device of the present invention.

[Explanation of symbols]

 10 ... Electrode head 12 ... Spindle head 14 ... Spindle 20 ... Electrode chuck 22 ... Electrode 24 ... Power feeding ring 26 ... First power feeding means 26a ... Power feeding brush 26b ... Adjusting screw 26c ... Spring 28 ... Second power feeding means 28a, 28b ... Clamping member 28c ... Cylinder 28d, 28e ... Contact member

Claims (2)

[Claims] 1. A power supply device of an electric discharge machine for supplying a machining current to an electrode mounted on a rotatably supported spindle, a disc-shaped device provided at a tip of the spindle so as to rotate together with the spindle. A power-supplied member, a first power-supplying unit that comes into contact with an outer peripheral surface of the disk-shaped power-supplied member for supplying a processing current to the electrode through the power-supplied member, and the power-supplied member. A second electric power supply means which is provided so as to be sandwichable and which sandwiches a side surface of the power-supplied member and supplies a machining current to the electrode via the power-supplied member. Power supply device. 2. The power feeding device for an electric discharge machine according to claim 1, wherein the second power feeding means includes a brake that holds a side surface of the power fed member to stop rotation of the spindle.