GB1065485A - Method and apparatus for electrolytically shaping an electrically conductive workpiece - Google Patents

Abstract

<PICT:1065485/C6-C7/1> <PICT:1065485/C6-C7/2> A conductive workpiece is shaped electrolytically by making it one electrode in an electrolyticbath and disposing adjacent to it tool electrodes movable between first and second positions respectively closer to and farther from each other, shaping the workpiece by initially effecting longitudinal approaching movement between it and the tool electrodes while the latter are in the first (closer) and then effecting transverse movement between the workpiece and the tool electrodes by moving the latter towards said second position so as to increase the area over which the workpiece is shaped. As shown, the workpiece 11 which is a turbine blade blank is mounted as anode in a closed cylinder 12 between two similar pistons 26, each carrying a cathode assembly 16 comprising a pair of electrodes 20, 21 pivotally mounted by spindles 25 and supporting a third electrode 22 by grooved connections allowing relative sliding movement. Attached to the pistons are bushes 27 secured to a carriage 30 slidable on fixed bars 41, 42. Rods 31 passing through the bushes are provided with micrometer stop nuts 35 and cam ends 32 engaged by followers on mounting plates 33 on the spindles 25. Secured to each carriage 30 is a push rod 43 having a roller engaging a track on a plate 45 movable transversely of the cylinder and by a nut 50 driven from a lead screw by an electric motor. A quick-release traverse for the plate with the lead screw stationary is provided by releasing a hydraulic clamp for the nut on the plate 45 and rotating the nut by a handwheel. Prior to each shaping operation compressed air is passed through each half of the cylinder to remove residual electrolyte from a previous operation and to operate the clamp for the nut 50. The compressed air source 66 Fig. 3 (not shown) is also arranged by means of doubleacting rams to raise or lower the cover 63 for the working area of the cylinder 12. Only when the cover is held closed does the compressed air close a pressure switch 68 (not shown) so that the electric motor is energized and the electrolyte is pressurized. When this is done, high pressure electrolyte is fed into the work gap and also via spring-biased needle valves 80 Fig. 4 (not shown) behind each piston 26 to compensate for the force tending to separate the pistons. When the electric motor drive is started the carriages 30 move inwardly, bringing the electrode assemblies 16 towards the workpiece. When the nuts 35 engage fixed abutment plates 36, the rods 31 are arrested and further movement of the carriages cause the followers on plates 33 to ride along the control cam surfaces 32 and move the electrodes 20, 21 away from each other as well as forwardly. Progress of machining is indicated by feelers 55 of dial gauges 56 engaging abutments 57 on the cylinder. Finally when spindle 61 of micrometer 62 engages microswitch 60, operation is stopped. On release of the electrolyte pressure the electrolyte behind the pistons returns through the needle valves 80, overcoming the spring loading. In a modification Fig. 6 (not shown) only a pair of pivotally mounted electrodes are carried by each piston, the electrode mountings having chamfered followers engaging a single central rod having a pair of axially inclined cam surfaces.