Interruptable numerical contouring control system with return to path

Abstract

A numerical control contouring system in which successive path segments are executed according to successive blocks of command signals making up a path program, the system being interruptable at any time by a feedhold signal to stop the controlled movable member at a random point on the path. The system is characterized by the improvement of preventing the system from resuming normal operation unless and until the member is returned to the path stopping point after it has been, for any reason, displaced therefrom under manual control or the like. In one embodiment, the axis component displacements of the member from the stopping point are represented by signals created and displayed, and the operator's restart pushbutton switch is rendered ineffective until the displayed displacement signals are reduced to zero. In another embodiment, the axis component displacement signals are utilized to create a non-program block of command signals, and means responsive to a restart signal first cause the member to be moved back to the path stopping point before the system is automatically restored to normal operation. In a third embodiment, after each movement of the controlled member following its arrival at the stopping point, the axis components for that movement are signaled and stored, and means responsive to a restart signal first utilize such stored signals to execute such movements in reverse order and senses to return the member to the path stopping point, and next restore normal operation of the system so that movement along the path is resumed.