JPS61117025A - Fine hole electric discharge machine - Google Patents

Abstract

PURPOSE:To make highly accurate drilling performable without producing any bend in a work hole, by forming a covering, which increases fluid friction, on an outer surface of a wire electrode partially or all over the surface, and feeding it with a machining fluid, while machining the hole while making the wire electrode rotate at high speed. CONSTITUTION:A chevroned covering 12 is formed on an outer surface of an electrode 1, a covering material is covered by means of plating or other methods. This covering material uses a homogeneous material as the electrode, other metals, alloys, plastics, ceramics, etc. And the electrode 1 is rotated at high speed by a motor 7 whereby contact resistance with a machining fluid interposed in a gap between a work hole 10a of a work body and the electrode is heightened. In the pipe electrode 1 itself rotating at this time, centripedal action works so as to reduce the resistance, whereby this electrode comes to be maintained centering on a rotary shaft. That is to say, the hole part being already machined, of the work body 10, comes to hydraulically guide a tip of the electrode 1 centering on the hole 10a, so that deflection, flection, vibration etc., in the thin electrode 1 are all prevented from occurring, thus straightness accuracy in the work hole is well improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an improvement in an apparatus for electrical discharge machining of a small hole using a thin wire electrode of a pipe or solid body.

[Prior art]

Conventionally, a thin pipe electrode is used, and the vibrator electrode is given high-speed rotation around its axis, and machining feed is given in the direction opposite to the workpiece, and a machining liquid is supplied in jet form from the pipe electrode while the electrode and the workpiece are rotated. A small hole electric discharge machining apparatus is known that performs machining by repeatedly performing pulse discharge in between. When water or a water-based liquid is used as the machining fluid, machining can be performed at a speed approximately twice as high as when using kerosene. However, the machined hole diameter is 1ml11φ or less, especially 0.1 to 0.311! +Rφ
If this happens, the pipe electrode will oscillate, making it difficult to provide accurate support and rotation. Therefore, there was a drawback that the machined hole would be curved, making it impossible to machine a straight hole with high accuracy.

[Problem solving means]

The present invention has been proposed to eliminate the drawbacks of the prior art, and is characterized by forming a coating on the surface of a thin wire electrode to increase fluid friction.

(Example) The present invention will be explained below with reference to an embodiment of the drawings.

In FIG. 1, reference numeral 1 denotes a vibrator electrode for drilling small holes, 2 a spindle for supporting the electrode, and the spindle 2 is rotatably suspended on a frame 4 by a bearing 3. 5 is a rack and pinion that engages with the frame, and is driven by a servo motor 6. 7 is a motor for rotating the spindle 2 and the electrode 1, and 8 is a machining fluid supply pump, which jets and supplies machining fluid stored in a liquid tank 9 from the tip 1a through the spindle 2 and the electrode pipe 1. Reference numeral 10 denotes a workpiece; 11 a machining power source that causes a pulse discharge to occur between the electrode 1 and the workpiece 10; the brush supplies electricity to the spindle 2; and the power supply is connected between the spindle 2 and the workpiece 10;

Tip 1a of pipe electrode 1 rotated by motor 1
The tip 1a of the pipe electrode 1 penetrates deeply into the machined hole of the workpiece 10 by performing electric discharge machining while facing the workpiece 10, and feeding is applied by the servo motor 6 as the machining progresses. Processing fluid supplied from pump 8 is pipe 1! It is ejected from the pole tip 1ira, flows upward through the gap between the pipe electrode 1 and the workpiece processing hole 10a, and continues processing while flowing and removing processing chips and the like.

Figure 2 is an enlarged view of electrode 1, with a dog-shaped coating 1 on the outer surface.
2 is formed. FIG. 3 shows an example in which a linear coating 13 parallel to the axial direction is formed on the outer surface of the electrode.

The covering material may be the same material as electrode 1, other metals, alloys (Zn, A7
etc.) plating, chemical plating, air plating, hot-dip plating,
Cover with other materials, or apply synthetic resin, ceramics, etc. The shape of the coating may be arbitrary, such as dots, lines, strips, spirals, or continuous planes.

The electrode 1, which is rotated at high speed by the motor 1, has a coating formed on its outer surface as shown in FIGS. A centripetal action acts to increase the contact resistance with the liquid and reduce the resistance of the rotating pipe electrode 1 itself, so that it is maintained centered around the rotation axis. That is, the workpiece 10
The tip of the rotating electrode 1, most of which has already been machined, is inserted into the hole 10.
Guide the hydrolitter to the center of a (grease center)
This prevents the thin electrode 1 from wobbling, bending, vibration, etc., and improves the straightness accuracy of the machined hole.

In addition, the machining fluid supplied from the pump 8 uses water, oil, etc., and generally has a kinematic viscosity of around 7C3t, high, + +
Even if I hear it, it is about 5-6c3. In the present invention, for example, a water-based surfactant, polyethylene glycol,
The kinematic viscosity of the processing liquid is increased by adding a thickener such as polyvinyl alcohol, glycerin, gelatin, agar, etc. If the kinematic viscosity of the machining fluid is increased to, for example, ISt or higher, it will be highly viscous and will be present in the gap between the machined hole and the pipe electrode, increasing the dynamic pressure control effect and further enhancing the center guiding effect of the rotating electrode 1. can be improved.

Note that if 1% of silicone surfactant is mixed with water, the kinematic viscosity will be about 2 St.

According to experiments, the outer diameter is 0.3 mmφ and the inner diameter is 0.3 mm. In+n
When drilling holes in SKD material with a +φ 3s vibe electrode, the electrode rotation speed is 1.00 Orpm and water is used as the processing fluid.
The bend in the hole is approximately 0.05 mm when machining a depth of 30 mm.
Met.

The processing speed at this time was about 11 mm/min.

Next, a coating with a thickness of about 10 μm was applied to the surface of the pipe electrode, oxidation treatment was performed, and when similar processing was performed, the depth was ioomm.
At t, the accuracy of the hole bending was approximately 0.02 mm.

At this time, the processing speed was approximately 38 mm/min.

The thickness of the coating layer on the electrode surface is usually about 5 to 20 microns, and in the case of metal coating, oxidation treatment can prevent side short circuits.

The rotation given to the electrode is about 500 to 2,000 rpm,
When the thin wire N pole is a solid body, the machining fluid can be supplied from opposing nozzles, and a supply nozzle is provided coaxially through the thin wire electrode to supply a jet of machining fluid along the electrode wire.

〔effect〕

As described above, the present invention involves forming a coating on a part or the entire surface of the wire electrode to increase fluid friction, and supplying machining fluid when machining a small hole by electrical discharge machining using a thin wire electrode. At the same time, since the wire electrode is rotated at high speed during machining, the rotating electrode is centripetally guided to the rotation center by controlling the dynamic pressure of the intervening machining fluid while the tip of the electrode is already inside the machining hole. It is held stably without any problems such as
It is possible to improve the accuracy of small hole machining and to perform deep hole machining at high speed. Hole diameter 1mmφ or less and length 1
0.00 mm, and even deeper hole drilling of 0.01 m
It can be processed with high precision, with a bending accuracy of about m.

[Brief explanation of the drawing]

FIG. 1 is an embodiment of the present invention, and FIGS. 2 and 3 are enlarged embodiments of electrodes used therein. 1... Line electrode 6... Machining feed servo motor...
... Rotating motor 8 ... Pump 10 ... Workpiece 11 ... Processing power source 12, 13 ... ... Electric rod surface coating layer patent application filed by Inoue Japax Institute Co., Ltd.), -. Representative: Kiyoshi Inoue ・1 page =: 、、、、;Mesai 1 (sake/IIL

Claims (1)

[Claims] Using a thin wire electrode, the thin wire electrode is given high-speed rotation around its axis and machining feed is given in the direction opposite to the workpiece, and a jet of machining fluid is supplied to the opposing gap between the electrode and the workpiece. A small hole electric discharge machining apparatus that performs machining by repeating pulsed discharge, characterized in that a coating for increasing fluid friction is formed on the outer surface of the thin wire electrode.