GB950506A - Improvements relating to electrolytic removal of metal - Google Patents

Abstract

In removing metal solely by electrolytic action from a workpiece, e.g. a rough forged turbine blade, the workpiece is clamped to an electrically non-conductive part or parts of a support so that should electrolyte become trapped between the workpiece and its support electrolysis between them is prevented. The workpiece is connected anodically, a cathode is disposed so that there is an anode-cathode gap of 0.005-0.040 inch, and electrolyte is directed through the gap at a rate of the order of 2 gallons per minute per square inch of workpiece surface subjected to electrolytic action. Fig. 1 shows a workpiece 12 clamped at 13 and 14 to non-conductive upraised portions 40 of a fixture 11. The portions 40 may be of ceramic or synthetic resin material or may be integral parts of the fixture 11 coated with such. A cathode 15 and electrolyte shoot 16 are supported in a box 17 and can be moved vertically by an electric motor 22 through gearing 21,20. Electrolyte is supplied to the cathode-workpiece gap by a pump 24 at a rate of flow fast enough to prevent the formation of local concentrations of electrolysis products at the anodic workpiece face. The used electrolyte is caught in a tank 10 and recirculated via a filter 26. A power unit 30 supplies electrolyzing current, the value of which depends on the closeness of the cathode and workpiece. A signal representative of the current is passed from the power unit 30 to a servo control unit 31 which controls the electric motor 22 so as to maintain the cathode-workpiece gap constant. Fig. 3 shows an alternative workpiece mounting where a workpiece 43 is held by metal clamps 48 aaginst non-conductive carrying members 44 of ceramic or synthetic resin of a metal fixture 42. Electrolyzing voltages not exceeding 48 volts, e.g. 12 volts, a current density of 30-150 amps./sq.inch and an electrolyte of an aqueous solution of sodium chloride at 20-60 lbs./sq.inch are specified. <PICT:0950506/C3/1> <PICT:0950506/C3/2> <PICT:0950506/C3/3>