GB1115816A - Electrochemical machining method and apparatus therefor - Google Patents

Abstract

<PICT:1115816/C6-C7/1> A method of machining a workpiece electrochemically comprises positioning the uninsulated operating face of an electrolytic tool in closely spaced and substantially parallel relation to the surface of the workpiece and effecting relative feed movement between the tool and the workpiece in a direction substantially parallel to the surface of the workpiece, the rate of erosion of the workpiece being thus dependant upon the magnitude of the current flowing between the tool and workpiece, the rate of feed movement between the tool and workpiece and the length of the tool. Different depths of erosion across the width of the workpiece may be obtained by use of a tool having a varying distance between leading and trailing edges, Fig. 6a (not shown). The tool shown comprises head 91 and a shank 92 for machining a workpiece having two intersecting flat surfaces 97a, 97b to be machined. The tool shank comprises a conducting tool body 93 and an insulating jacket 94. Electrolyte is passed from the inlet tube 42 and via the vertical passage 95 to the workface. The workpiece is mounted upon a table 11 covered by insulating pad 30 Fig. 1 (not shown), the table being connected by a horizontal screw 14 and gears 15, 16 to an electric motor 17, which may be controlled to impart a required speed of horizontal movement to the table 11, and hence to the workpiece. Figs. 4a, 4b (not shown) illustrate electrical circuitry suitable for controlling the current density such that should the feed rate vary, the current density applied is automatically varied to compensate therefor, and to maintain a constant rate of erosion. The current density may be varied according to a predetermined pattern, e.g. by means of a cam Fig. 13 (not shown) or a data input device. In another embodiment Figs. 7-11 (not shown) two electrode tools of arcuate workface are used to machine annular workpieces. The workpiece 124 is rotated between the tools, which are positioned 180 degrees apart. Electrical circuitry Figs. 12a, b, c (not shown) is described by means of which the two tools may be moved automatically radially inwards to compensate for erosion of the workpiece, and thereby maintain the current density between tool and workpiece constant.