GB1002956A - Electrolytic cavity sinking apparatus and method - Google Patents

Abstract

A method of electrolytically forming a cavity in a workpiece comprises relatively moving the workpiece and a hollow electrode towards each other at a controlled substantially constant rate, feeding electrolyte through the electrode into a gap between the electrode and workpiece at a controlled pressure, maintaining the temperature of the electrolyte supply to the electrode at a substantially constant level above ambient temperature, and applying a substantially constant direct voltage between the workpiece and the electrode, the method being characterized in that the pressure is always controlled to a level above that at which there is a formation of steam bubbles in the electrolyte in the gas sufficient to affect the dimensional accuracy of the cavity to substantial extent. A rate of relative movement of 0.010-0.800 inch/minute, a voltage of 5-18, a temperature of 100-180 DEG F. and a pressure of 30-300 pounds/inch2 are specified. Fig. 1 shows an electrode 22 in a holder 25 which is advanced by a ram 11. A workpiece (not shown) is held on a work table 127 <PICT:1002956/C6-C7/1> <PICT:1002956/C6-C7/2> mounted on a vertical slide controlled by a hand wheel 129. The entire ram assembly can be moved horizontally in the direction towards and away from the viewer looking at Fig. 1 by manual operation of a hand wheel 123. The ram 11 is advanced by a screw 31, Fig. 2, driven by a reversible motor M operating through a variable speed transmission VST, a transmission 57 comprising gearing and electric clutches 65 and 67, a sprocket 55, chain 41 and sprocket 39. Actuating one or other clutch 65 or 67 moves the electrode in a low or high speed range and further speed adjustment is by operating a control knob 45 of the variable speed transmission. An electrically operated brake 43 prevents the ram from overtravelling when the clutches are disengaged. Electrolysing voltage is controlled at a console C. Electrolyte is supplied to the electrode 22 from a tank 130 via hose 149, pump 145, filter 157, hose 159, valve 165, hose 27 and the electrode holder 25. The pressure and temperature of the electrolyte entering the electrode are measured at 169 and 175 respectively. Electrolyte from the work is collected in a pan beneath the table and is returned to the tank. The electrolyte in the tank is heated by an immersion heater 135 controlled by a thermostat 137 or is cooled by water flowing through a cooling coil 151. The pressure at which the electrolyte is supplied to the electrode is controlled by adjustment of valve 165 and a valve 161 in a passageway returning to the tank. A pressure gauge is provided at 163. A dial 23 indicates the depth to which a cavity has been sunk and means, Figs. 3 and 4 (not shown) are provided for presetting the depth to which the cavity is to be formed. Specification 943,101 is referred to.