Curve interpolating method

A method of generating a smooth curve from a commanded sequence of points by a numerical controller for a multi-axis machine tool having three linear axes and two or more rotary axes to perform interpolation along the generated curve, comprising:

• calculating interpolation points between points of a commanded sequence of points and setting the calculated interpolation points as geometrical command points;
• noticing respective points of the geometrical command points one by one so as to select a noticed point and geometrical command points located before and behind the noticed point, wherein the number of geometrical command points has been decided in advance;
• resolving each of the geometrical command points into a component of three linear axes and a component of two or more rotary axes;
• generating an approximated curve for linear axes with regard to the component of three linear axes;
• moving the component of three linear axes toward the approximated curve for linear axes so as to obtain corrected command point for the linear axes;
• generating an approximated curve for rotary axes with regard to the component of two or more rotary axes;
• moving the component of two or more rotary axes toward the approximated curve for rotary axes so as to obtain corrected command point for rotary axes;
• synthesizing the component of three linear axes of the corrected command point for the linear axes which has been moved and the component of two or more rotary axes of the corrected command points for rotary axes which has been moved so as to obtain a synthesized corrected command point;
• repeating the noticing, resolving, generating, moving, generating, moving, and synthesizing with regard to the respective geometrical command points;
• generating a curve passing through a point sequence of the synthesized corrected command points;
• and
• interpolating the generated curve.