EDM Method of machining workpieces with a controlled crater configuration

A method of machining an electrically conductive workpiece with a tool electrode juxtaposed therewith across a machining gap flooded with a liquid machining medium,

• wherein a succession of time-spaced electrical pulses are passed through said gap to produce between the opposed surfaces of the tool electrode and the workpiece discrete electroerosive discharges each of which results in the formation of a discharge crater on a localized spot on the workpiece surface and the consequential localized stock removal therefrom and which, with such discharge craters formed successively and randomly throughout the workpiece surface opposed to the tool electrode surface, cumulatively remove stock from the workpiece while the tool electrode is moved relative to the workpiece along a predetermined path to advance stock removal in the workpiece;
• wherein the liquid machining medium may be forced to flow through said machining gap;
• and
• wherein the tool electrode may be displaced relative to the workpiece, independently of but simultaneously with the aforesaid relative displacement therebetween,
• said method comprising:
• reducing the surface roughness of said machined workpiece by increasing at least one of the rate of said flow of the liquid machining medium through said gap and the rate of the second-mentioned relative displacement between the tool electrode and the workpiece to such an extent that each of said discharge craters becomes elliptical in shape and has its major axis at least two times greater than its minor axis.