Advanced memory type profiling control method for a machine tool

A profiling control method of an advanced memory type for a machine tool including:

• a tracer provided with a stylus at an end thereof which is moved along a surface of a model for detecting a shape of the model, said stylus performing a spheric motion around a ball seat fixed in the tracer, and the tracer comprises means for detecting components e.sub.x, e.sub.y and e.sub.z in a three-orthogonal-axis system of positional variation of the stylus to the ball seat of the tracer;
• a control unit for producing control signals for the tracer by utilizing an output signal of the tracer;
• a tracer drive unit for moving the tracer on the basis of the control signals for the tracer;
• a machine body for controlling a cutting tool on the basis of the control signals for the tracer;
• said method comprising the steps of:
• calculating coordinates of the stylus from the coordinates (X, Y, Z) of the ball seat and the positional variations (e.sub.x, e.sub.y, e.sub.z) on the basis of the following equations:
• Xp=X+e.sub.x
• Yp=Y+e.sub.y
• Zp=Z+e.sub.y -l
• where l is a distance between the ball seat and the stylus when e.sub.z =0, said coordinates being used as the control signals for the tracer;
• calculating control signals for the machine body by calculating respective numbers (Cxn, Cyn, Czn) of distribution pulses, corresponding to movement of an end mill of the machine body, from coordinates (Xpn+1, Ypn+1, Zpn+1) and (Xpn, Ypn, Zpn) at sampling times n+1 and n on the basis of the following equations:
• Cxn=(Xpn+1-Xpn)/.DELTA.h
• Cyn=(Ypn+1-Ypn)/.DELTA.h
• Czn=(Zpn+1-Zpn)/.DELTA.h
• wherein .DELTA.h is a unit of minimum movement of the end mill, and when Cxn<0, Cyn<0 Czn<0, movements of the end mill in a negative direction are represented, respectively;
• storing the control signals for the machine body in a memory;
• and
• driving the end mill on the basis of the control signals for the machine body stored in the memory, characterized in that said step of calculating the control signals comprises a step of calculating average velocity vectors (Vpxn, Vpyn, Vpzn) of the stylus from coordinates (Xpn+m, Ypn+m, Zpn+m) and (Xp, Yp, Zp) of the stylus at sampling times n+m and n on the basis of the following equations:
• ##EQU17## where .DELTA.ts is a time interval for sampling.