GB2060460A

GB2060460A - Spark Erosion Method

Info

Publication number: GB2060460A
Application number: GB8030565A
Authority: GB
Original assignee: VUMA Vyskumny Ustav Mechanizacie a Automatizacie
Current assignee: VUMA Vyskumny Ustav Mechanizacie a Automatizacie
Priority date: 1979-09-28
Filing date: 1980-09-22
Publication date: 1981-05-07
Also published as: SE8006763L; FR2466308A1; CS210083B1; FR2466308B1; AT388891B; ATA308780A; DE3024023A1; SE451805B; GB2060460B; CH648229A5

Abstract

Electrospark working of shaped surfaces of a workpiece (1) submerged at least partly in a working liquid (5) contained in a vessel (4) with the surface (3) being worked facing the bottom of the vessel (4) and situated above a tool electrode (2) consisting of at least one electrode preferably in bar form is carried out with relative movement of workpiece and tool electrode in direction of a tangent of or parallel to the worked surface and substantially perpendicular to the worked surface at a speed of their relative movement higher than 0.2 ms<-1>. <IMAGE>

Description

SPECIFICATION Method of Electrospark Working of Shaped Surfaces of Workpieces and an Arrangement and Tool Electrode for Execution of this Method The invention relates to a method of electrospark working of shaped surfaces of workpieces, particularly of rotational and planar surfaces, an arrangement and a tool electrode for execution of this method.

Electrospark working of technologically demanding shaped surfaces of workpieces, particularly of those with high technical-physical properties, for instance stress resistivity, hardness, toughness and not oriented roughness, is more and more applied in practice. The electrospark working and the respective arrangements have however despite their many advantages some drawbacks or limiting factors, which present their wider application. One of these limiting factors is a worsened rinsing of the interelectrode space and a reduced stability of the working process when working larger surfaces and a low efficiency limited by the required roughness of the worked surface.

At present, additional movements of the electrode and forced rinsing over openings in the tool electrode are used for improvement of rinsing of the interelectrode space and in order to improve the working efficiency while maintaining the required quality of the surface a multichannel working is provided. In the first case even due to additional movements the widened gap need not be sufficient for effective removal of working products, particularly when finishing the working at reduced power of individual discharges, another possible drawback is the cumbersome removal of extensions after openings and gaps for rinsing.A limiting factor of an increased productivity of working in the second case is the non linear dependence on the increased number of channels due to difficulties resulting froni a simultaneous advance of a number of electrodes, which are usually connected with a single support so that in case of a short circuit of one electrode all remaining electrodes are put out of operation by a simultaneous movement out of engagement.

It is an object of this invention to provide a method and an arrangement which would to a high degree eliminate these drawbacks of known methods and arrangements.

A method of electrospark working of the shaped surfaces of a workpiece by a tool electrode, the electrode and workpiece being connected together to a source of electrical impulses, according to the invention comprises a mechanism for advancing the workpiece relative to the tool electrode in a vessel filled with a working liquid, which is supplied into the vessel in a clean form, the polluted working liquid being drained from the vessel, the tool electrode acting on the worked surface of the workpiece in direction tangential or parallel to the worked surface and in a direction substantially perpendicular to the worked surface of the workpiece at a speed of their relative movement higher than 0.2 ms-'.

The workpiece is advantageously situated above the tool electrode so that the worked surface faces the bottom of the vessel containing the working liquid.

The tool electrode for carrying out the method of the invention can be a single rod which has a shape corresponding to the final shape of the worked surface of the workpiece, whereby the length of the active surface of the tool electrode corresponds to the width of the worked surface or it can be formed by at least two rods mutually insulated and connected each to a special current feeding channel from an impulse generator.

Advantages of the method of the present invention consist in an improvement of conditions for removal of working products from the interelectrode space and in the liquidation of occasional disturbing conditions in the spark gap, such as bridges of conglomerations of conductive impurities or temporary short circuits on one or more channels at multichannel working, thus substantially improving the stability of the working process, increasing the percentage of productive electric impulses from the generator, reducing the overall machining time of working and due to reduction of short circuits and improved rinsing also improving and making uniform the final roughness of the worked surface. In addition this method enables working also of larger workpieces without need of their complete submerging into the working liquid.

The attached drawing shows diagrammatically an exemplary embodiment for carrying out the method of electrospark working of shaped surfaces of workpieces according to this invention.

The workpiece 1, the dimensions of which can be relatively large, is situated in a vessel 4 above a tool electrode 2 and the worked surface 3 of the workpiece 1 is facing the bottom of the vessel 4.

Only the worked part of the workpiece 1 is submerged in the working liquid 5. Both the workpiece 1 and the tool electrode 2 are connected by conductors 6 and 7 to a generator 8 of electric impulses.

The tool electrode 2 is fixed in a support not shown on the drawing, the workpiece 1 is similarly supported above the tool electrode 2 so that the worked surface of the workpiece is facing the bottom of the vessel 4.

The vessel 4 is filled with a working liquid 5 in which is the workpiece 1, moved by a driving element 1 7 and the tool electrode 2, moved by a mechanism 11 which is started to be moved relatively in direction 9 tangentially or parallel to the worked surface 3 of the workpiece 1, so that the size of the interelectrode space remains constant. The mutual relative movement of the workpiece 1 and the tool electrode 2 can be along a straight line or with rotational workpieces along a circular or part circular path and can be progressive or reciprocal. With continuing removal of material the workpiece 1 and the tool electrode 2 approach in direction 10 substantially perpendicular to the worked surface 3.Clean working liquid 5 is supplied into the vessel 4 via a nozzle 1 3. A lateral rinsing of the whole content of the vessel is applied and the pulluted working liquid is removed through a conduit 15 for regeneration and repeated application. The tool electrode 2 is suitably a single rod which has a shape corresponding to the final shape of the worked surface 3 so that the length of the active surface of the tool electrode corresponds to the width of the worked surface 3.

In order to increase the working speed, a tool electrode 2 may be formed by at least two bars is used which are mutually insulated and each of which is connected to a special channel 16 for an independent current supply from an impulse generator 8.

The tool electrode 2 acts on the worked surface 3 of the workpiece 1 in a direction 9 tangential or parallel to the worked surface 3 and in a direction 10 substantially perpendicular to the worked surface 3 of the workpiece at a speed of their relative movement higher than 0.2 ms-l and preferabiy between 0.2 ms' and 5 ms'.

Claims

1. A method of electrospark working of the shaped surfaces of a workpiece by a tool electrode, the electrode and workpiece being connected together to a source of electrical impulses, comprising a mechanism for advancing the workpiece relative to the tool electrode in a vessel filled with a working liquid, which is supplied into the vessel in a clean form, the polluted working liquid being drained from the vessel, the tool electrode acting on the worked surface of the workpiece in direction tangential or parallel to the worked surface and in a direction substantially perpendicular to the worked surface of the workpiece at a speed of their relative movement higher than 0.2 ms~,.

2. A method of working as claimed in Claim 1 wherein the speed is between 0.2 ms-' and 5 ms-'.

3. An arrangement for carrying out the method as claimed in Claim 1 the workpiece being situated above the tool electrode so that the worked surface of the workpiece is facing the bottom of the vessel.

4. A tool electrode for carrying out the method as claimed in Claim 1 comprising a bar, the active surface of which corresponds to the final shape of the worked surface of the workpiece, whereby the length of this active surface of the tool electrode corresponds to the width of the worked surface of the workpiece.

5. A tool electrode as claimed in Claim 4 the tool electrode comprising at least two mutually insulated bars, each of which is connected to an independent current supply from an impulsegenerator.

6. Method of electrospark working of shaped surfaces of workpieces substantially as described with reference to the accompanying drawing.

7. An arrangement for electrospark working of shaped surfaces, substantially as described, with reference to the attached drawing.

8. A tool electrode for electrospark working of shaped surfaces of workpieces substantially as described, with reference to the accompanying drawing.