Micro Electrochemical Machining for Tapered Holes of Fuel Jet Nozzles

An electromachining process of tapered holes for fuel jet nozzles is presented, in which a tapered hole is shaped by ECM after a straight cylindrical pilot hole is drilled by EDM. In the electrode side-insulated ECM shaping step, the tapered shape, filleted corner and also improved surface roughness can be obtained simultaneously by controlling either applied machining voltage (current) or feeding speed of tool electrode. The influences of machining voltage, pulse duration, pulse duty ratio and electrode feeding speed to hole diameter's variance were investigated experimentally. A tapered hole with inlet diameter 175pm and outlet diameter 200(jm was machined by raising applied voltage gradually during electrode feeding, and a tapered hole with inlet diameter 181(j,m and outlet diameter 203pm was machined by decreasing electrode feeding speed gradually, on lmm thick nickel plate specimen. Preliminary experiments show the feasibility of the electromachining process for the tapered holes of fuel jet nozzles.