Numerically controlled cutting method

A numerically controlled cutting method of cutting a curved surface which is generated by interconnecting corresponding points on two curved lines, comprising the steps of:

• supplying as inputs curve information specifying the two curved lines, information on wire radius including an electric discharge gap in wire-cut electric-discharge cutting, information on the direction of wire compensation, and division information for dividing the curved lines;
• dividing the curved lines based on said division information and computing dividing points mi, ni (i=1, 2, . . . );
• computing the vectors of normals in said direction of wire compensation at the dividing point mi on one of the curved lines and at the other dividing point ni corresponding to the dividing point mi, and computing wire compensation positions mi', ni' corresponding to the dividing points mi, ni upon wire position compensation in the directions of the normals using said information on the wire radius;
• computing the direction of the wire axis from said wire compensation positions mi', ni';
• computing the positions of points mi" (u, v), ni" (x, y) corresponding to the wire compensation positions mi', ni' and lying on planes parallel to a table for placing a workpiece thereon, using said direction of the wire axis, said wire compensation positions;
• and
• driving the table in the directions of X, Y based on x, y and driving the wire in the directions of U, V based on u, v to cut the workpiece along the curved surface.

A numerically controlled cutting method for taper cutting a workpiece along a predetermined curved surface, which intersects a first plane on a first side of the workpiece along a first curved line and which intersects a second plane on a second side of the workpiece and parallel to the first plane along a second curved line, using an elongated cutter having an axis, said method comprising the steps of:

• dividing the first curved line into segments which intersect each other at dividing points mi (i=1, 2, . . . ) and dividing the second curved line into corresponding segments which intersect each other at corresponding dividing points ni (i=1, 2, . . . );
• for each pair of dividing points mi, ni, determining a corresponding pair of cutter compensation positions mi', ni' lying in a plane which is substantially normal to said predetermined curve and which passes through the dividing points mi and ni, the compensation positions mi', ni' being spaced apart from the dividing points mi, ni so as to lie on the axis of said cutter when the dividing points mi, ni lie substantially on the periphery of said cutter;
• when the axis of the cutter passes through the compensation positions mi-1', ni-1', moving the cutter with respect to the workpiece so as to bring the axis of the cutter to a position passing through the compensation positions mi', ni';
• and
• repeatedly moving the cutter with respect to the workpiece until the predetermined curved surface is cut.