JPS6176219A - Electric discharge machining device for fine hole - Google Patents

Abstract

PURPOSE:To stably hold an electrode with no lateral deflection and improve accuracy for machining a fine hole, by providing a groove formed on an external surface of the pipe electrode and supplying machining fluid to be jetted from the pipe. CONSTITUTION:An electrode 1 forms on its external surface over the whole area a doglegged groove 12. The pipe electrode 1, rotated by a motor 7 at a high speed, increases contact resistance with fluid interposing in a gap formed between the electrode and a machined hole 10a in a workpiece 10, and the rotating electrode 1 itself, on which centripetal action acts so as to decrease the resistance, maintains the rotary axis in the center. In this way, a device, preventing lateral deflection, flection vibration, etc. of the thin pipe electrode 1, enhances accuracy of straightness in the machined hole.

Description

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

[Prior art]

A thin pipe electrode is used, and the pipe electrode is given high-speed rotation around its axis, and machining feed is given in the direction opposite to the workpiece, and while a jet of machining fluid is supplied from the pipe electrode, a flow is created between the electrode and the workpiece. 2. Description of the Related Art A small hole electric discharge machining apparatus that performs machining by repeating pulsed discharge is well known. By using water as the machining fluid, machining can be performed at about twice the speed as when using kerosene.

However, the machined hole diameter is less than 1111IIlφ, especially 0.1
When the diameter is about 0.2 mm, the pipe electrode bulges out, 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 drill a straight hole with high precision.

[Problem solving means]

The present invention was proposed to eliminate the drawbacks of the conventional method, and is characterized by forming groups (kerfs, side cuts, etc.) on the outer surface of the pipe electrode.

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

In FIG. 1, 1 is a pipe electrode for drilling small holes, 2 is a spindle that supports the electrode, and the spindle 2 is rotatably mounted on a frame 4 via a bearing 3. 5 is a rack and pinion that engages with the frame, and is driven by a servo motor.
6. 1 is a motor that rotates the spindle 2 and the electrode 1; 8 is a machining liquid supply pump; the machining liquid stored in the liquid tank 9 is jetted out from the tip i1a through the spindle 2 and the electrode pipe 1; 10 is a workpiece, 11
is a machining power source that causes a pulse discharge to occur between the electrode 1 and the workpiece 10, and is connected between the spindle 2, which is energized by a brush, and the workpiece 10.

Tip i1a of pipe electrode 1 rotated by motor 7
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. The machining liquid supplied from the pump 8 is ejected from the pipe electrode light @1a, flows upward through the gap between the pipe electrode 1 and the workpiece machining hole 10a, and machining is continued while flowing away machining chips and the like.

FIG. 2 is an enlarged view of the electrode 1, in which a doglegged groove 12 is formed over the entire outer surface. FIG. 3 shows an example in which grooves 13 parallel to the axial direction are formed on the outer surface of the electrode.

The pipe electrode 1 rotated at high speed by the motor 7 includes
Since the kerf grooves 12 and 13 are formed as shown in FIGS. 2 and 3, they are cut into the machined hole 10 of the workpiece by high-speed rotation.
By increasing the contact resistance with the liquid present in the gap between the rotating pipe electric rod 1 itself, a centripetal action acts to reduce the resistance, and the rotating pipe electric rod 1 itself is maintained centered on the rotation axis. That is, most of the already machined part of the workpiece 10 is hydraulically guided (grease center) by the tip of the rotating pipe electrode 1 to the center of the hole, which prevents lateral vibration of the thin pipe electrode. Prevents deflection, vibration, etc., and improves the straightness accuracy of machined holes.

In addition, water, oil, etc. are used as the machining fluid supplied from the pump 8, and generally the kinematic viscosity is 5 to 5 at most after reaching IC3.
It is about 6c3. In the present invention, the kinematic viscosity of the processing liquid is increased by, for example, adding a surfactant, a thickener such as polyethylene glycol, polyvinyl alcohol, glycerin, gelatin, agar, etc. to the water base.

The kinematic viscosity of the machining fluid is increased to, for example, 1st or more and then supplied.

Then, it is highly viscous and intervenes in the gap between the machined hole and the pipe electrode, thereby enhancing the dynamic pressure control effect and further improving the center guiding effect of the rotating electrode 1. 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 0.18 mIIlφ, and the inner diameter is 0.06.
When drilling a hole in an SKD material using a 1 mφ 3s pipe electrode, the rotation speed of the electrode was 11000 rp, water was used as the processing fluid, and the bend in the hole was approximately 0.05 mm when the hole was drilled to a depth of 3 ommt. The processing speed at this time was 35 mm/min.

Next, using a pipe electrode with five grooves of 0.02 mm depth formed on the surface, the same process was performed (when the hole turned out to be 10100 l11, the accuracy of the bend in the hole was approximately 0.02 mm). Furthermore, when water mixed with 5% silicon-based surfactant was used as the machining liquid, the machining could be performed with high accuracy of approximately 0.0+2 bending at a depth of 100 mm.

〔effect〕

As described above, the present invention forms a group on the outer surface of the pipe electrode, supplies a jet of machining fluid from the pipe, and rotates the vibrator electrode at high speed. Since electrical discharge machining is used, the rotating pipe electrode is centripetally guided to the center of rotation by dynamic pressure control of the intervening machining fluid when the tip of the pipe electrode is in the already machined hole, thereby preventing lateral runout. It is held stably without any problems, improving the accuracy of small hole machining, and the depth can be increased, making it possible to drill holes with a hole diameter of 11Il.
It is possible to machine deep holes with a bending accuracy of about 0.01 mm with a bending accuracy of about 0.01 mm, making it possible to machine deep holes with a length of about 100 mm or even longer at fflφ or less. In addition to forming groups of pipe electrodes, the center kite effect of centripetal dynamic pressure on the rotating pipe electrodes is enhanced by using a machining fluid whose kinematic viscosity is increased in Stokes units for the machining fluid supplied in a jet flow. This has the effect of further increasing the accuracy of small hole machining.

[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... Pipe electrode 6... Machining feed servo motor 7...
... Rotating motor 8 ... Machining fluid supply pump 10 ...
... Workpiece 11 ... Processing power source 12, 43 ... Group patent applicant Kiyoshi Inoue Representative of Inoue Japax Laboratory Co., Ltd. 'Kita-' Bee SaiztR Sai 31koku

Claims (1)

[Claims] A thin pipe electrode is used, and the pipe electrode is given high-speed rotation around its axis, and machining feed is given in the direction opposite to the workpiece, and while a jet of machining fluid is supplied from the pipe electrode, the flow between the electrode and the workpiece is 1. A small hole electrical discharge machining device for machining by repeatedly applying pulsed discharge to a small hole, characterized in that groups are formed on the outer surface of the pipe electrode.