Pitch error compensation system

Claim 1

A pitch error compensation system for a machine tool provided with a pulse motor adapted to move a movable member through a feed screw and a pulse generator for producing a train of pulses to be applied to said pulse motor in accordance with numerical information, comprising: memory means for storing said numerical information including control data to instruct incremental feed amounts of said movable member and compensating data used to compensate the positioning error of said movable member therein, said compensating data consisting of data pairs of compensating directions and compensating positions determined as positions where said positioning error changes in magnitude beyond a predetermined unit amount of positioning error; presettable counter means for registering an incremental feed amount supplied from said memory means; accumulating counter means for indicating an absolute position Of said movable member in accordance with said incremental feed amount; position detecting means responsive to said memory means for registering said compensating positions; direction detecting means responsive to said memory means for registering said compensating directions; comparator means for comparing contents in said accumulating counter means and said position detecting means to select compensating directions between the absolute position of said movable member and a predetermined origin; and summing counter means responsive to said direction detecting means and said comparator means for detecting a positioning error for said incremental feed amount in accordance with the selected compensating directions, said presettable counter means being responsive to said summing counter means for modifying said registered incremental feed amount in accordance with said positioning error.