Method of digitizing a profile locus

In a profiling method for performing NC working on the basis of locus data obtained by profiling a shape of a model by a stylus of a profiling machine, a method of digitizing profiling locus data comprising the steps:

• (a) detecting displacement of the stylus by stylus detection means and generating digitized stylus detection signals (.epsilon..sub.x, .epsilon..sub.y, .epsilon..sub.z);
• (b) producing profiling speed command signals, for driving respective drive motors corresponding to three axes of the profiling machine in response to the stylus detection signals on the basis of central position signals of the stylus from a profiling data processing unit, by a profiling speed controlling unit;
• (c) detecting drive positions of the drive motors by position detection means to produce drive position signals;
• (d) adding the drive position signals (X, Y, Z,) for the three axes to the stylus detection signals (.epsilon..sub.x, .epsilon..sub.y, .epsilon..sub.z) of the stylus displacement detecting means by an arithmetic operation unit for a central position of the stylus, to produce profiling data signal;
• and
• (e) passing the profiling data signal through an electric filter in the profiling data processing unit to apply a time constant, defined by a rate of change of the displacement (.epsilon..sub.x, .epsilon..sub.y, .epsilon..sub.z) of the stylus according to the relation K=.vertline..epsilon..sub.x .vertline.+.vertline..epsilon..sub.y .vertline.+.vertline..epsilon..sub.z .vertline., in which K is the rate of change, to the profiling data signal, wherein the time constant of the electric filter in the profiling data processing unit is automatically made smaller as the rate of change K of the displacement of the stylus increases, and producing the central position signal of the stylus to the profiling speed controlling unit.