Fabrication of micro ball joint by using micro-EDM and electroforming

Miniature products are useful in present-day industrial applications. In the area of micro machine, micro transmissions and linkages are needed. The micro transmissions such as gear and rack can be made by wire-cut, electric discharge machining (micro-EDM), injection molding, etc. Comparatively, mechanical linkages such as bearing or ball joint are much difficult to be manufactured due to the need of assembly. In this paper, a technique to fabricate micro ball joint and bearings by micro-EDM and electroforming is proposed. The electrode is first taken as a workpiece and is machined by wire electro-discharge grinding (WEDG) to form a round ball at its free end. This is followed by coating a removable conductive layer on its surface. Electroforming is then applied to fabricate the shell for the ball socket. After washing away the sacrificial layer the micro ball joint is obtained. Micro bearings can be manufactured by similar procedures. By applying the proposed approach a micro ball joint contains tungsten carbide rod with ball and the shell of the ball is fabricated successfully. The whole component is less than [email protected] in dimensions. Testing of the finished micro ball joint proves that it functions properly. Using this technique, many micro machine applications such as micro robot, micro robotic arm and micro stage can be realized.