JPH05212673A - Electro-discharge machining method of super abrasive grain grinding wheel and device thereof - Google Patents

Abstract

PURPOSE:To keep off any disconnection of an electrode in preventing the wire electrode from contacting with abrasive grains during machining operation by making a discharge gap between the wire electrode and the super abrasive grains larger than a grain size of each abrasive grain. CONSTITUTION:A rectilinear part of a wire electrode being rectilinearly supported in space between two wire guides 40 and transferred at the specified speed, is approximated to a super abrasive grain grinding wheel 20 rotating at the specified speed. In succession, a discharge voltage is impressed to an interval between the wheel 20 and a wire electrode 22 by a discharge power means 46 in the state that a discharge gap larger than a diameter of each abrasive grain in the wheel 20 is kept in space between them, while the wheel 20 and the wire electrode 22 are relatively converted whereby electro-discharge machining takes place. In consequence, such a possibility that the wire electrode 22 might be contacted with the abrasive grains is prevented from occurring, and any possible disconnection of the wire electrode 22 is kept back while chips are favorably discharged out.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric discharge machining method and apparatus for performing electric discharge machining such as truing, dressing and forming on a superabrasive grindstone.

[0002]

2. Description of the Related Art Conventionally, processing such as truing, dressing, and forming for a superabrasive grindstone has been generally performed by a forming grindstone, and the bond holding the abrasive grains of the superabrasive grindstone is a resin type soft bond. As for the shaped grindstone, a GC or alumina-based grindstone is used, and when the bond is a metal-based hard grindstone, a harder metal-bonded diamond grindstone is used as the shaped grindstone.

However, the conventional processing method using the shaped grindstone has a drawback in that it is difficult to process the superabrasive grindstone into an accurate shape because the shaped grindstone also wears.

Therefore, in recent years, for a superabrasive grindstone using a metal bond, a method of electric discharge machining using a die-sinking electric discharge machine has been adopted. This electric discharge machine has a structure as shown in FIG. 3, and in a machining fluid (water or oil) 2 filled in a tank 1, a superabrasive grindstone 3 supported by a grindstone support arm 4 is provided with an electrode. Support arm 5
A discharge voltage is applied between the super-abrasive grindstone 3 and the electrode wheel 6 by the discharge power supply device 9 while abutting the electrode wheel 6 supported on the electrode wheel 6 and driving and rotating them by the motors 7 and 8. As a result, as shown in FIG.
The outer peripheral surface of is processed according to the shape of the electrode wheel 6. In the figure, 10 is an X-axis moving table that moves the grindstone support arm 4 in the X-axis direction, 11 is the same Y-axis moving table, 12 is an X-axis motor that drives the X-axis moving table,
Reference numeral 13 is a Y-axis motor that drives the Y-axis moving table, and 14 is a control circuit that controls these motors.

However, in such a conventional electric discharge machining, since the disc-shaped electrode wheel 6 is required, there are many disadvantages in terms of structure and space, and the superabrasive grindstone 3 is used as an electrode. There are drawbacks such that it can only be machined into a shape that fits the wheel 6 and that it is difficult to machine very finely or in a narrow space.

On the other hand, a method of using a wire electrode instead of the electrode wheel 6 and performing electric discharge machining of a metal-bonded diamond grindstone with this wire electrode has been studied. In this method, as shown in FIG. 5, the wire electrode 15 is pressed against the outer peripheral surface of the diamond grindstone 17 by a wire guide 16, and a discharge voltage is applied from a power source 18 between them so that the grindstone 17 and the wire electrode 15 are opposed to each other. The wire electrode 1 is moved by the presence of the wire guide 16.
The chips between 5 and the diamond grindstone 17 are hard to be removed,
There is a drawback that secondary discharge is likely to occur, which has been one of the causes for cutting the wire electrode. Further, the wire guide 16 has an obstacle that it cannot perform machining of a fine shape or machining in a narrow place, and these drawbacks cause the electric discharge machining of the superabrasive grindstone by the wire electrode. It was a hindrance to practical use.

[0007]

DISCLOSURE OF THE INVENTION The object of the present invention is to eliminate the need for a wire guide as in the prior art and to improve the chip removal when performing the electric discharge machining of a superabrasive grindstone with a wire electrode. It is intended to prevent the secondary discharge and the cutting of the wire electrode due to the subsequent discharge, and to enable fine shape processing with one wire electrode.

[0008]

In order to solve the above-mentioned problems, an electric discharge machining method according to the present invention is designed so that a superabrasive grindstone rotating at a predetermined speed is linearly supported between two wire guides. The linear portions of the wire electrodes transferred at a velocity are brought close to each other, and a discharge gap larger than the diameter of the abrasive grains of the superabrasive grain grindstone is maintained between them, and between these superabrasive grain grindstones and the wire electrode. The electric discharge machining is characterized in that the electric discharge voltage is applied and the superabrasive grindstone and the wire electrode are relatively displaced.

Further, the electric discharge machining apparatus of the present invention is supported linearly between the two wire guides and the grindstone supporting means for rotatably supporting the superabrasive grain grindstone to be machined, and the superabrasive grind at the linear portion. A wire electrode for performing electric discharge machining on a grain grindstone, a discharge power supply means for applying a discharge voltage between the superabrasive grain grindstone and the wire electrode, the grindstone support means and the wire electrode are relatively displaced in the XY direction. Position control means for
It is characterized by consisting of.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of an electric discharge machining apparatus according to the present invention, in which 20 is a metal-bonded superabrasive grindstone which is a processing target, and 21 is the superabrasive grindstone 20 which is rotatable. A grindstone supporting means for supporting, and 22 are wire electrodes for performing electric discharge machining on the superabrasive grindstone 20.

The whetstone supporting means 21 is a Y-axis moving table 25 which is movable in the Y-axis direction, and the Y-axis moving table 25.
A Y-axis motor 26 that drives the X-axis moving table 25, an X-axis moving table 27 that is movable on the Y-axis moving table 25 in the X-axis direction, an X-axis motor 28 that drives the X-axis moving table 27, and an X-axis moving table 27. A conductive support arm 29 attached via an electric insulator 30 is provided, and the support arm 29 is provided with the superabrasive grindstone 20 in a working fluid 32 such as oil or water filled in a tank 31. Is rotatably supported, and is driven and rotated at a predetermined speed by a motor 34 via a belt 35. 36 in the figure is the X
The control device controls the axis motor 28 and the Y-axis motor 26, and includes a servo circuit and a control circuit.

The wire electrode 22 is linearly supported by the two wire guides 40, 40, and the straight line portion 22a between the wire guides 40, 40 is predetermined in the machining fluid 32 on the superabrasive grindstone 20. Are arranged close to each other while maintaining the discharge gap of the wire electrode 22, the wire electrode 22 extends from the supply device 41, and the tip reaches the winding device 42. Due to
The linear portion 22a is transferred at a predetermined speed while being given an appropriate tension.

The support arm 29 and the wire electrode 22 are
It is connected to a discharge power supply 46 via brushes 44, 45, and a discharge voltage is applied from the discharge power supply 46 between the superabrasive grindstone 20 and the wire electrode 22 during processing.

When electric discharge machining is performed on the superabrasive grindstone 20 with the electric discharge machine having the above-mentioned structure, the superabrasive grindstone 2 is used.
0 is driven and rotated by a motor 34 at a predetermined speed, and while the wire electrode 22 is transferred at a predetermined speed, a discharge gap larger than the diameter of the abrasive grain is formed between the wire electrode 22 and the superabrasive grindstone 20. In this state, a discharge voltage is applied from the discharge power supply 46 between the superabrasive grindstone 20 and the wire electrode 22. Then, the control device 36 shifts the X-axis moving table 27 and the Y-axis moving table 25 in the XY directions to control the position of the support arm 29, thereby processing the superabrasive grindstone 20 into a predetermined shape (FIG. 2). reference).

At this time, the wire electrode 22 and the superabrasive grindstone 2
Since the discharge gap between 0 and 0 is larger than the grain size of the abrasive grain,
The wire electrode 22 does not contact the abrasive grains during processing,
Therefore, disconnection of the electrodes does not occur. Further, since the chips are satisfactorily discharged through the large discharge gap and do not stay between the wire electrode 22 and the superabrasive grindstone 20, secondary discharge due to the chips is unlikely to occur.

The thickness of the wire electrode 22 is about 0.05.
It can be appropriately determined within the range of about 0.5 mm depending on the processing conditions. For example, when the wire diameter is 0.1 mm or less, even if the discharge gap is taken into consideration, the gap of 0.15 mm Since the wire electrode 22 is inserted therein, fine processing becomes possible. Further, since the wire electrode 22 is processed in the straight part, the side surface of the grindstone can be processed. Especially when processing a multi-edged grindstone, the machining accuracy of the gap depends on the diameter of the grindstone but is several μm. Is. The wire electrode 22
It is also possible to configure the wire guide supporting the NC to be NC controlled.

[0017]

[Experimental Example] With an electric discharge machine as shown in FIG. 1, a metal-bonded diamond grindstone that is a superabrasive grindstone (abrasive grain size: 20 to 30 μm, concentration 75, outer diameter 180 mm,
(Thickness 10 mm) was subjected to electric discharge machining using a wire electrode having a wire diameter of 0.2 mm and a brass material. As the processing conditions at this time, the rotational speed of the grindstone is 20 rpm, the transfer speed of the wire electrode is 3 m / min, and the tension of the linear portion is 100.
0 gr and the discharge gap was 50 μ, which was larger than the abrasive grain size. As the discharge conditions, the maximum current value is 3A, the pulse ON time is 50μSec, and the pulse OFF time is 25μ.
Sec, the no-load voltage was set to 100V, and the processing voltage was set to 250V.

Under the above conditions, the target of the machining allowance (grinding allowance) is set to 0.3 mm, and the machining of the machining allowance of 0.1 mm is repeated three times to process the outer peripheral surface and the thickness of the diamond grindstone. I went. As a result, it was possible to perform machining with an accuracy of ± 5μ in outer diameter tolerance and ± 3μ in thickness tolerance without causing wire electrode disconnection.

[0019]

According to the present invention, the following effects can be expected. (1) Since a grindstone can be processed into various shapes with a single thin wire electrode without using an electrode wheel such as die-sinking electric discharge machining, the structure is simple and the apparatus is small. (2) By making the discharge gap between the wire electrode and the superabrasive grindstone larger than the grain size of the abrasive grain, the wire electrode is prevented from coming into contact with the abrasive grain during processing and the disconnection of the electrode is prevented. be able to. In addition, since the chips are satisfactorily discharged through the large discharge gap and do not stay between the wire electrode and the superabrasive grindstone, secondary discharge due to the chips is unlikely to occur. (3) Since it is processed in the linear portion of the linearly supported wire electrode, it is possible to reliably perform fine shape processing or processing in a narrow place by selecting the wire diameter of the wire electrode. Pitch processing is also possible by the distance between the multi-edge wheels, that is, the side surface processing. (4) It is possible to significantly shape the grindstone as compared with the conventional fine processing of dressing and truing of the grindstone.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of an electric discharge machine according to the present invention.

FIG. 2 is an enlarged sectional view of a main part of FIG.

FIG. 3 is a configuration diagram showing an example of a conventional electric discharge machine.

FIG. 4 is an enlarged cross-sectional view of a main part of FIG.

FIG. 5 is a configuration diagram showing another example of a conventional electric discharge machine.

[Explanation of symbols]

 20 Super Abrasive Grain Stone 21 Grindstone Supporting Means 22 Wire Electrode 36 Controller 40 Wire Guide 46 Discharge Power Supply

Claims (2)

[Claims] 1. A linear portion of a wire electrode, which is linearly supported between two wire guides and is transported at a prescribed speed, is brought close to a superabrasive grain grindstone that rotates at a prescribed speed, and the superabrasive grain is interposed between them. While maintaining a discharge gap that is larger than the diameter of the abrasive grains of the grindstone, a discharge voltage is applied between these superabrasive stone and wire electrode, and the superabrasive stone and wire electrode are relatively displaced. A method of electric discharge machining of a superabrasive grindstone, which comprises performing electric discharge machining by means of electric discharge machining. 2. A grindstone support means for rotatably supporting a superabrasive grindstone to be machined, and a wire electrode linearly supported by two wire guides, and the electric discharge machining is performed on the superabrasive grindstone at the linear portion. And a discharge power supply means for applying a discharge voltage between the superabrasive grindstone and the wire electrode, and a position control means for relatively shifting the grindstone supporting means and the wire electrode in the XY direction. Discharge machine for superabrasive grindstone.