Abstract: A method and apparatus are disclosed for automatically realigning a machine element to a predetermined position after an interruption of power to a drive mechanism coupled to the machine element. After the termination of power, the apparatus measures a displacement of the machine element during a predetermined period of time; and this displacement is stored in a nonvolatile memory. When power is restored to the drive mechanism, the apparatus is operative to automatically move the machine element back through a distance equal to the stored displacement. Consequently, the machine element realigns to the position it had before the power interruption.

Abstract: An apparatus for controlling the transmission of multiple level priority interrupt signals to a central processing unit. A number of storage elements are responsive to the interrupt signals on an individual basis. A last-in first-out memory having an output connected to the processing unit stores storing the interrupt signals in order of descending priorities. A comparator circuit compares the priority of a new interrupt signal in the storage element with the highest priority interrupt signal currently in the memory. If the new interrupt signal is of the same or a higher priority, an interrupt request signal is sent to the processing unit. Subsequently, the processing unit returns an acknowledge signal which is operative to load the new interrupt signal into the memory, thereby providing the new interrupt signal as an output therefrom. The acknowledge signal also resets the storage element associated with the new interrupt signal.

Abstract: A method and apparatus are disclosed for controlling the initiation of cutting motions for cutting multiple start threads on a rotating workpiece held in a spindle of a numerically controlled machine. The numerical control contains an interpolator circuit responsive to a spindle feedback circuit connected to the spindle for generating a marker pulse and a predetermined number of spindle pulses for every revolution of the spindle. The apparatus provides input signals representing a particular threading start number relative to the total number of threading starts. Next, a control signal is generated which represents a number of spindle pulses as a function of the ratio of the particular threading start number to the total number of threading starts. Upon detecting an occurrence of a marker pulse which would normally initiate a threading motion, the apparatus is operative to inhibit a number of spindle pulses corresponding to the control signal.

Abstract: A method and apparatus are disclosed for modifying command signals representing predetermined positions of a machine element relative a workpiece as a function of measurable unprogrammed changes in the relative position therebetween. The machine element is responsive to a servomechanism circuit which in turn responds to a control device producing the command signals to command motion of the machine element to programmed points relative to the workpiece. The servomechanism circuit produces interrupt signals for transferring the command signals thereto. A measuring circuit is responsive to the unprogrammed change in relative position between the machine element and the workpiece and is operative to produce feedback signals representing the direction and magnitude of the change in relative position. A first circuit is responsive to the measuring circuit for producing a first signal representing a current unprogrammed change in relative position with reference to a predetermined point.

Abstract: In an EDM process, a method and apparatus are disclosed for determining the quality of a machining gap by detecting a voltage signal across the gap in response to a low power pulse applied immediately prior to a machining pulse. Upon detecting a first predetermined number of consecutive inferior gap voltage signals in response to corresponding low power pulses the application of low power pulses and machining pulses is terminated for a predetermined period of time. Thereafter, only the low power pulses are applied to the machining gap; and after detecting a second predetermined number of consecutive good gap voltage signals in response to corresponding low power pulses, the machining pulses are reapplied.

Abstract: A digital circuit useful in a numerical control system for determining during a preliminary execution of a program the axial components of a tool offset compensation. During a preliminary operation of the program, the sum of the squares of the axial components of displacement of the tool are compared to the square of the desired tool offset. When the sum of the squares equals or exceeds the square of the offset, the current values of the axial components of displacement are stored and used as the axial offset components during a subsequent execution of the program.