Abstract: The invention relates to an NC data creation method for machining a curved surface (101) having a cutting boundary surface (102) in the depth direction. Data specifying the three-dimensional curved surface (101) and the curved surface (102) of a cutting boundary in the depth direction are inputted. When the three-dimensional curved surface (101) is defined by a set of a plurality of point-sequence paths (11i), a point sequence Q(i,j) of a tool nose corresponding to a point sequence A(i,j) is determined. Next, there is determined a projected point sequence B'(i,j) obtained by projecting the point sequence Q(i,j) of the tool nose onto a reference plane (103), as well as a projected point sequence C(i,j) obtained by projecting the first-mentioned projected point sequence onto the curved surface (102) of the cutting boundary.

Abstract: A method of creating NC data for grooving, a unit normal vector (N) at the position (Pe) of a grooving end point is obtained after creation of NC data for grooving, a movement vector (D) is obtained by multiplying a designated movement distance (da) by the unit normal vector (N), and NC data for withdrawal are created for moving a tool (TL), by the amount of the movement vector (D), from the position (Pe) at which grooving ends.

Abstract: The method of the invention includes determining a circular arc (CAR) passing through three discretely given consecutive points (P.sub.i-1, P.sub.i, P.sub.i+1), determining a tangent vector of a tangent line contacting the circular arc (CAR) at the central point (P.sub.i) of these three points, thereafter performing a spline interpolation between the two points P.sub.i-1, P.sub.i using position vectors and tangent vectors at the points (P.sub.i-1, P.sub.i), thereby obtaining a curve smoothly connecting the two points P.sub.i-1, P.sub.i, and thereafter determining a point sequence connecting curve (CVL) by similarly performing an interpolation between every two adjacent consecutive points.

Abstract: A curved surface creation method suitable for use in creating two curved surfaces for coarse and finishing machining. A first space curve (1) is divided into N segments, a second space curve separately obtianed is similarly divided into N segments and a curved surface for coarse machining is created by connecting corresponding i-th dividing points R.sub.i (i=1, 2, . . . ). Next, the first space curve (1), which is obtained by successively connecting the dividing points R.sub.i (i=1, 2, 3, . . . ), is divided into M (>N) segments, the second space curve is similarly divided into M segments and a curved surface for finishing machining is created by connecting the i-th dividing points S.sub.i (i=1, 2, 3, . . . ) of the first space curve (1), which is divided into M segments, with and the corresponding dividing points of the second space curve.

Abstract: NC data for grooving are created by inputting a groove shape (GR) which lies on a three-dimensional curved surface as well as a groove-depth specifying curve (GRC) which indicates a relationship between a distance d from one end and groove depth hk of a point at this distance, obtaining the distance dk from one end of the groove-depth specifying curve (GRC) in accordance withdk=lk.multidot.Lj/Liwhere Li represents the total length of the groove shape, lk the distance from one end of the groove shape and Lj the total length of the groove-depth specifying curve (GRC), obtaining, from the groove-depth specifying curve, the depth hk at the distance dk from the abovementioned one end, and adopting the groove depth hk as groove depth of a point at the distance lk from the one end of the groove shape (GR).