GB1270876A - Electrolytic machining process and apparatus - Google Patents

Abstract

1,270,876. Electrolytic machining. MITSUBISHI DENKI K.K. Oct. 2, 1969 [Oct. 2, 1968], No.48581/69. Heading C7B. [Also in Division G3] An electrolytic machining process comprises the steps of disposing a workpiece and a working electrode with a working gap therebetween, supplying a liquid electrolyte to the working gap, effecting relative approach movement between the workpiece and the working electrode at a constant speed, applying a working voltage across the workpiece and the electrode thereby electrolytically to remove material from the workpiece, producing a signal proportional to the product of the working voltage multiplied by the reciprocal of the specific resistance of the electrolyte, and controlling the working voltage so as to maintain the signal at a constant value thereby to maintain constant the ratio of the working voltage to the specific resistance of the electrolyte during the electrolytic machining operation. Thereby the working gap and also the clearance between the working electrode and the side of a hole being machined can be kept constant. As shown, a working electrode 16 machines a workpiece 12. The electrode 16 is moved at a constant speed by a motor 68. The electrolyzing power is provided from a three-phase A. C, source 34 via a saturable three-phase reactor 38, transformer 36 and full wave rectifier 52. A signal V', representing working voltage, and a signal #', representing conductivity, are fed to a circuit 350 for multiplying V' by #' and the resultant signal S is compared at a comparison point 100 with a reference signal S o . Any difference between these signals causes control of current through reactor winding 50 thereby controlling the working voltage for the electrolytic machining. In circuit 350, conductivity signal #' is fed to a potentiometer 376 where the position of the wiper is controlled by a servomotor 362 which itself is controlled by a difference signal derived from signal V' and a signal e derived from a potentiometer 354. Specified electrolyzing conditions are:- an aqueous sodium chloride electrolyte, a working gap of 0À1 to 0À05 mm, a voltage of 5 to 20 volts, a current of 3,000 to 5, 000 amps and movement of the working electrode towards the workpiece at lmm/min.