Electrochemical machining

1,135,571. Electro-machining. ROLLSROYCE Ltd. Dec.20, 1965 [Dec.23, 1964], No. 52381/64. Heading C7B. A workpiece, e.g. a turbine blade, is electrolytically machined in a succession of discrete operations each using a separate tool held in fixed spaced relationship to the workpiece while material is removed therefrom by passing electric current between the tool and workpiece; further layers of material are removed with successive tools having working surfaces dimensioned to lie closer to the finished shape of the workpiece. The tool may at least partially surround the workpiece. As shown for batch production, a frame 30 has an annular arrangement of stations 31 each adapted for supporting a tool 32 comprising at least two relatively movable parts allowing a workpiece 35 to be inserted between or withdrawn from them, e.g. by a ram 42, the stations being surrounded by a rotable head 33 having a series of work-holders 34 each supporting a workpiece. The head is adapted to be indexed by a motor 36 acting through gearing 37, 38, a ram 40 engaging a plunger 39 in slots 41 in the head for locating the workpieces in registration with the tools.