Wire EDM taper cutting method using path data of two planes of a workpiece

A wire electrode discharge machining method for cutting a workpiece by moving a wire electrode relative to the workpiece and producing an electric discharge across the wire electrode and the workpiece, comprising the steps of:

• preparing and entering path data specifying contours on an upper and on a lower plane of the workpiece;
• separately preparing and entering auxiliary data including an amount of wire diameter compensation, workpiece mounting position and guide positions necessary for moving the wire electrode relative to the workpiece;
• continuously finding first relative travel quantities (.DELTA.x.sub.w1, .DELTA.y.sub.w1 ;
• .DELTA.x.sub.w2, .DELTA.y.sub.w2) of the wire electrode with respect to the upper and lower planes of the workpiece over a predetermined period of time;
• converting said first relative travel quantities into second relative travel quantities (.DELTA.x.sub.u, .DELTA.y.sub.u ;
• .DELTA.x.sub.d, .DELTA.y.sub.d) of the upper and lower guides with respect to said workpiece by using said auxiliary data including workpiece mounting position and guide position data;
• moving the upper and lower guides relative to the workpiece in accordance with said second relative travel quantities;
• producing pulses of a number of equivalent to integral portions of said second relative travel quantities to move the uppr and lower guides relative to the workpiece;
• and
• correcting subsequent second relative travel quantities of the upper and lower guides with respect to the workpiece by decimal portions of the present second relative travel quantities.