Feedrate control system

Claim 1

A feedrate control system for numerically controlled machine tools comprising: a tool having a rotatable spindle, means for producing a fixed number of pulses for each rotation of the spingle, switch means having first and second positions, a first interpolator connected through said switch means when in a first position to receive the spindle pulses and to iterate a selected override quantity at the spindle pulse rate; a feedrate control signal source, said first interpolator being connected through said switch means when in said second position to iterate said override quantity at a fixed rate, an override selector means connected to the first interpolator for providing said override quantity, a second interpolator connected to receive a part program feedrate number and being further connected to iterate said number at the rate overflows occur from the first interpolator, and an axis command interpolator connected to receive the overflows from the second interpolator and to iterate a predetermined number placed therein at the rate said overflows occur, the output of the axis command interpolator being connected directly to control the rate at which a machine tool is moved relative to the spindle.