Involute interpolation speed control system

A method for speed control in an involute interpolation speed control system including a cutter, for effecting an involute interpolation to which a cutter compensation is applied when machining by a numerical control apparatus, said method comprising the steps of:

• a) reading commands from a command storage unit, for generating data regarding a direction in which a first involute curve as an actual machining configuration is rotated, coordinates of the end point of the first involute curve, a position of a center of a basic circle as viewed from a start point of the first involute curve, a radius of the basic circle, a feed speed, a direction in which the cutter is offset, and an amount of offset of the cutter;
• b) creating an offset vector of the cutter based on the commands;
• c) calculating an equation of a second involute curve connecting a start point and an end point after the offset vector has been created;
• d) determining a radius of curvature of the second involute curve at a center of the cutter;
• e) determining a feed speed override value based on the direction in which the cutter is offset, the offset amount, and the radius of curvature;
• f) interpolating, in a pulse distributing unit, the second involute curve based on a value obtained by multiplying the feed speed override value by the feed speed;
• and
• g) controlling the cutter based on the second involute curve interpolated in said step (f), so that a cutting speed of the cutter is maintained at a constant value.