Patent ID: 7393311

Claim:
A monitoring method for a tool-holding spindle having a tool-gripping collet driven by an axially shiftable control rod, and a sensor positioned for sensing an axial position of the rod and delivering an output signal as a function of said position, comprising, whenever each tool is initially picked from a tool crib in a working session, the steps of: (a) after checking that the collet is closed, taking a predetermined number of readings of a position of the control rod (P c1 , P c2 , . . . , P cn ) by means of said sensor, at predetermined intervals starting from a predetermined delay (T) after the closure of the collet; (b) computing a current average of said readings (P c1 , P c2 , . . . , P cn ) whereby a value for the current position of the rod (P m ) is obtained; (c) notifying that the collet closure is regular and storing said current position value (P c ) as previous position value (P m ); and further comprising the steps, to be carried out when subsequently picking the respective tool within the same working session, of: (d) taking said predetermined number of rod position readings (P c1 , P c2 , . . . , P cn ) by means of said sensor, at said predetermined intervals starting from a predetermined delay (T) after the closure of the collet; (e) computing the current average of said readings (P c1 , P c2 , . . . , P cn ) whereby a fresh value for the current rod position (P c ) is obtained; (f) comparing the current rod position value (P c ) with the corresponding stored previous rod position value (P m ) and, if their deviation is less than a predetermined threshold (S), notifying that the collet closure is regular, and otherwise notifying that the collet closure is defective; (g) if the collet closure is regular, storing said current rod position value (P c ) as previous rod position value (P m ).