JPH11151617A - Generating discharge machining method and device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To use a relatively thick pipe electrode, and to improve the accuracy of the side surface machining. SOLUTION: As a pipe electrode 14 rotated around the axial center by a rotating means, a material with a large thickness t0 is selected, and a cutting tool 24 is provided movable in the radial direction of the pipe electrode 14, immediately under a ring guide 21 to guide the pipe electrode 14 slidable. When the pipe electrode 14 is moved in the axial direction to a discharge machining position, the outer periphery of the pipe electrode 14 is cut off by the edge 24a of the cutting tool 24, and its thickness t1 is made thinner than the value subtracting the discharge gap δ from the maching allowance s of the side surface of a work 11 (t1 <s-δ), and a discharge is generated between the tip of the pipe electrode 14 made in the thin wall, and the work 11, to cut down the side surface of the work 11 in a layer form, so as to carry out a finish machining of the side surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to electric discharge machining,
In particular, the present invention relates to a method and apparatus for generating electric discharge by performing electric discharge between a tip end surface of a pipe electrode and a workpiece to perform machining.

[0002]

2. Description of the Related Art As shown in FIG. 4, the electric discharge machining is carried out by rotating a pipe electrode 1 and moving the pipe electrode 1 in two directions X and Y intersecting the axis thereof, so that the pipe electrode 1 and a workpiece 2 are connected to each other. A voltage is applied from the power supply 3 to generate a discharge between the tip end surface of the pipe electrode 1 and the workpiece 2, and the pipe electrode 1 is sent a predetermined distance in the axial direction Z each time one surface is finished. This is a processing method in which the workpiece 2 is dug down in layers to create a hole 4 having a desired contour and depth. At the time of this electric discharge machining, a machining fluid is sent at a high pressure to the tip through the inside of the pipe electrode 1 (arrow A).

In this type of electric discharge machining, in order to improve machining efficiency, rough machining is performed by increasing the supply current in an initial stage, and finishing is performed by decreasing the supply current in a final stage. I have. In this case, as shown in FIG. 5, the bottom surface 4a of the hole 4 'formed in the workpiece 2 is finished with high precision, but the side surface thereof is extremely rough. Therefore, usually, as shown in the same manner, after the side surface 4b of the hole to be created is processed in the depth direction while leaving a predetermined allowance s, the pipe electrode 1 is removed as shown in FIG. A so-called side surface finishing process is performed in which the machining allowance s is removed while being sequentially fed in the axial direction Z, thereby creating a hole 4 having a desired surface accuracy.

However, according to the above-mentioned side surface finishing, as shown in FIG. 6, when the allowance s is smaller than the value obtained by adding the wall thickness t of the pipe electrode 1 and the discharge gap δ (s
<T + δ), the amount of wear on the tip end surface of the pipe electrode 1 becomes non-uniform in the radial direction, and not only the shape accuracy of the inner surface 4a of the created hole 4 is deteriorated, but also the inner peripheral side of the pipe electrode 1 is not consumed in some cases There is a problem that the portion 1a remains and it becomes impossible to finish the side surface. For this reason, Japanese Patent Application Laid-Open
In the electric discharge machining method described in JP-A-108945, a pipe electrode 1 having a thickness t similar to or smaller than the above-mentioned allowance s is selected (s ≧ t) to prevent abnormal consumption of the pipe electrode. Care was taken to prevent it.

[0005]

However, as described above, when selecting a pipe electrode 1 having a thickness t less than the allowance s, the selected pipe electrode 1 becomes extremely thin depending on the allowance s. Insufficient rigidity makes it difficult to attach the pipe electrode to the mechanism for supporting and rotating the pipe electrode 1 with high precision, and the roundness and straightness of the thin pipe are generally poor. There is a problem that large rotational runout occurs in the pipe electrode, and it is extremely difficult to finish the side surface of the workpiece with high accuracy.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and has as its object to reduce the thickness of the pipe electrode before the electric discharge machining position so that a relatively thick pipe can be formed. The present invention provides a method and apparatus for generating electric discharge, which enables the use of electrodes and greatly contributes to improvement of machining accuracy.

[0007]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the method of the present invention is to rotate a pipe electrode around its axis while moving the pipe electrode in a direction intersecting the axis and in an axial direction. In the generating electric discharge machining method of generating a discharge between the tip end surface and the workpiece and finishing the side surface of the workpiece, in the middle of moving the pipe electrode in the axial direction, the wall thickness is reduced by peripheral machining. It is characterized in that it is reduced to less than the allowance for the workpiece.

Further, according to the present invention, there is provided an apparatus for supporting a pipe electrode for rotating the pipe electrode about its axis, a direction intersecting the axis of the pipe electrode supported on the pipe electrode, and Moving means for moving in the axial direction;
A power source for applying a voltage between the pipe electrode and the workpiece, generating electric discharge between a tip surface of the pipe electrode and the workpiece by rotating the pipe electrode to perform side machining. The apparatus is characterized in that the moving means supports a processing means for processing the outer periphery of the pipe electrode in accordance with the axial movement of the pipe electrode.

In the electric discharge machining method and apparatus constructed as described above, while the pipe electrode is moved in the axial direction, the outer periphery is processed by the processing means supported by the moving means to reduce the wall thickness. As the pipe electrode to be used, a relatively thick and highly rigid one can be selected, and it is possible to mount the pipe electrode on a rotating means for supporting and rotating the pipe electrode with high accuracy, and to realize the roundness of the pipe itself, In combination with the increase in straightness, the rotational runout is suppressed.

[0010]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 2 shows the overall structure of the electric discharge machining apparatus according to the present invention. In the figure, 10
Is a processing table, on the upper surface of which is a processing tank 13 in which a base 12 for positioning and mounting the workpiece 11 is mounted, and a rotating device (rotating means) 15 for supporting the pipe electrode 14 in a vertical state and rotating it around its axis. A moving device (moving means) 16 for moving the pipe electrode 14 to the electric discharge machining position via the power supply and a power supply (not shown) for applying a voltage between the pipe electrode 14 and the workpiece 11 are provided. .

The moving device 16 includes a column 17 movably disposed on the processing table 10 in a direction X perpendicular to the plane of the drawing, and an upper end of the column 17 in a horizontal direction Y orthogonal to the X direction.
And a vertical slide member 19 that supports the rotating device 15 and that is mounted on the tip of the horizontal slide member 18 so as to be movable in the vertical direction (the axial direction of the pipe electrode 14) Z. And These pillars 1
7, the horizontal slide member 18 and the vertical slide member 19
The pipe electrodes 14 are moved by independent driving means (not shown) controlled by a numerical controller (NC device), and the pipe electrodes 14 are mounted on the base 12 in the processing tank 13 by these movements. It moves to a predetermined electric discharge machining position for the placed workpiece 11. In addition, the processing tank 13
A processing fluid 20 is stored in the inside of the processing fluid 20.
Is operated by a circulating pump (not shown).
5 and is fed back into the processing tank 13 through the pipe electrode 14.

An L-shaped bracket 22 having a ring guide 21 on a lower piece 22a for slidably inserting the pipe electrode 14 is detachably attached to the horizontal slide member 18 of the moving device 16. ing. The ring guide 21 plays a role of controlling the posture (centering) when supporting the pipe electrode 14 on the spindle 15 a of the rotating device 15 and preventing the vibration when the rotating device 15 rotates the pipe electrode 14. The mounting height of the bracket 22 is adjusted so that the ring guide 21 is located near the workpiece 11.

On the other hand, the lower piece 22a of the bracket 22
A processing device 23 for processing the outer periphery of the pipe electrode 14 extending downward through the ring guide 21 is disposed on the lower surface of the pipe electrode 14. As shown in FIG. 1, the processing device 23 includes a cutting tool 24 having a cutting blade 24 a at a tip thereof, and a feed for supporting the cutting tool 24 and moving the cutting tool 24 in the radial direction of the pipe electrode 14 as indicated by an arrow A. The unit 25 is provided as one unit, and three such units are arranged in the circumferential direction of the pipe electrode 14. The feed means 25 of each unit is controlled synchronously by the NC device. With this control, each cutting tool 24 advances in synchronization with a predetermined machining position, and its cutting edge 2
4a is cut into the outer periphery of the pipe electrode 14 rotated by the rotating device 15 and moved in the axial direction by the vertical slide member 19, and the outer periphery of the pipe electrode 14 is deleted over a predetermined depth.

Hereinafter, an electric discharge machining method using the generating electric discharge machine configured as described above will be described. In the present embodiment, the inner surface (side surface) of a hole 4 '(FIG. 2) formed in the workpiece 2 in advance by bottom surface processing is to be finished. as shown in, predetermined as a pipe electrode 14 has a large wall thickness t ₀ sufficiently than cash s taken (t _0> s) shall, i.e. select a high rigidity, it to the spindle 15a of the rotating device 15 Is supported so as to have a projection length. At this time, the pipe electrode 14 is positioned such that its tip end projects slightly downward from the ring guide 21. By selecting a thick and highly rigid material for the pipe electrode 14 as described above, when the pipe electrode 14 is supported by the spindle 15a of the rotating device 15, the pipe electrode 1
No deformation occurs in 4 and its mounting accuracy is improved.

After the preparation is completed, when the apparatus is started, first, the support 17 and the horizontal slide member 18 move in accordance with a command from the NC apparatus, and the rotating apparatus 15 moves horizontally in the two directions of X and Y to form a processing tank. The pipe electrode 14 is positioned at a predetermined position above the workpiece 11 in the pipe 11. Next, the rotating device 15 operates in response to a command from the NC device to rotate the pipe electrode 14, and then the vertical slide member 19 descends to feed the pipe electrode 14 in the axial direction Z thereof. At this time, the processing device 2
The plurality of cutting tools 24 are positioned at a predetermined forward position by the operation of the corresponding feeding means 25, and the outer periphery thereof is formed at a predetermined depth by the cutting blade 24 a of the cutting tool 24 in response to the rotation of the pipe electrode 14. As a result, the tip portion of the pipe electrode 14 has a thickness t ₁ (t ₁ <s−) smaller than a value obtained by subtracting the gap δ from the allowance s.
δ). In the present embodiment, the outer periphery processing (cutting) of the pipe electrode 14 is performed directly below the ring guide 21 and is performed by three cutting tools 24 equally arranged in the circumferential direction. During the rotation, no rotational vibration occurs in the pipe electrode 14, and the outer periphery thereof is uniformly deleted. In addition, since the cutting is performed in the working fluid 20, the cutting tool 24 is not worn out early by the cutting heat, or the cut pipe electrode 14 is not thermally deformed.

The pipe electrode 14 thus thinned
Of the pipe electrode 14 approaches the workpiece 11, a discharge is generated between the tip of the pipe electrode 14 and the workpiece 11, and the lowering of the pipe electrode 14 is stopped at this position. Next, pipe electrode 1
When the support 17 and the horizontal slide member 18 move in accordance with a command from the NC device, the work 4 makes one round along the inner circumference of the hole 4 ′ of the workpiece 11. Complete. The rotating device 15 has a built-in correction feed mechanism (not shown) for feeding the pipe electrode 14 in the axial direction in accordance with the consumption of the pipe electrode 14. The degree of wear is determined, and correction feeding is performed at any time. The side surface processing is repeated in layers while sequentially feeding the pipe electrode 14 in the axial direction Z, and the entire processing of the inner surface of the hole 4 ′ of the workpiece 11 is completed. Since the pipe electrode 14 has a thick wall and high rigidity between the rotating device 15 and the ring guide 21, rotation deflection of the pipe electrode 14 during the electric discharge machining is suppressed. At the same time, the tip of the pipe electrode 14 involved in the discharge has a thickness t ₁ smaller than the allowance s, so that the tip does not wear out abnormally. Can be finished with high precision.

In the above embodiment, the cutting tool 2 is used as the processing device 23 for processing the outer periphery of the pipe electrode 14.
4, but the type and structure of the processing device 23 are arbitrary. For example, as shown in FIG.
Instead of 4, an electrode rod 26 may be provided. In this case, a voltage is applied from the power supply 27 to the electrode rod 26 to generate a discharge between the tip of the electrode portion 26 and the pipe electrode 14 to perform the outer peripheral machining. According to the method, unlike the above-described cutting method, no processing reaction force is generated, so that only one electrode rod 26 needs to be prepared.

In this apparatus, the cutting tool 24 or the electrode rod 26 of the processing apparatus 23 is largely retracted so that the thick pipe electrode 14 can be directly processed into the bottom surface of the workpiece 11 (hole 4 '). ), And therefore can be used for both bottom processing and side processing, and there is no double investment in equipment.

[0020]

As described above, according to the electric discharge machining method and apparatus according to the present invention, the thickness of the pipe electrode is reduced before the electric discharge machining position. This makes it possible to use a thick pipe electrode, suppresses rotational deflection of the pipe electrode as much as possible, and performs side processing with high precision. Further, according to the apparatus according to the present invention, the existing moving means for moving the rotating means for supporting the pipe electrode is merely provided with the processing means for processing the outer periphery of the pipe electrode. Can be shared, and there is no double investment of equipment, and there are some that have high utility value.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing one embodiment of a generating electric discharge machining method according to the present invention.

FIG. 2 is a side view showing a partial cross section of the overall structure of the electric discharge machine according to the present invention.

FIG. 3 is a sectional view showing another embodiment of the electric discharge machining method according to the present invention.

FIG. 4 is a schematic view showing a general implementation state of the electric discharge machining.

FIG. 5 is a schematic diagram showing the state of implementation of bottom surface processing and side surface processing by generating electric discharge machining in order.

FIG. 6 is a cross-sectional view showing an example of a defect in conventional side processing.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Workpiece 13 Processing tank 14 Pipe electrode 15 Rotation apparatus (rotation means) 16 Moving apparatus (movement means) 23 Processing apparatus (processing means)

Claims (2)

[Claims] 1. A pipe electrode is rotated in a direction intersecting with its axis and in an axial direction while rotating the pipe electrode about its axis, so that a discharge is generated between a tip end surface of the pipe electrode and a workpiece, and In the generating electric discharge machining method of finishing the side surface of the workpiece, while moving the pipe electrode in the axial direction,
A method of generating electrical discharge machining, wherein the thickness is reduced to a value equal to or less than an allowance for a workpiece by outer peripheral machining. 2. A rotating means for supporting a pipe electrode and rotating it about its axis, a moving means for moving the rotating means in a direction intersecting with the axis of the pipe electrode supported thereon and in an axial direction, A power supply for applying a voltage between the workpiece and the workpiece, wherein the rotation of the pipe electrode generates a discharge between the tip surface and the workpiece to perform side machining, and the generation electric discharge machining apparatus, The electric discharge machining apparatus according to claim 1, wherein the moving means supports a processing means for processing an outer periphery of the pipe electrode in accordance with an axial movement of the pipe electrode.