Based on the machining principle analysis of the nature ruled surfaces, the technologies of NC programming for intricate nature ruled surfaces by wire-EDM were studied, including the profile marking standard, the algorithm of seeking corresponding points, equal-error synchro-linear approximation of profiles and the method to calculate the maximum inclining angle of ruling.

In this paper, by the motion analysis of four-axis wire-Electric Discharge Machining (WEDM) machine tools, it is concluded that, during the machining of intricate ruled surfaces only with linear boundary curves, the maximum inclining angle of the wire and the maximum displacements of the machining table and the wire guiding head occur on the vertices of the boundary lines.