Numerical Control of a Lathe

This paper deals with the design of a digital biaxial contouring control system for a lathe, constructed at the Technion-Israel Institute of Technology. The system is capable of simultaneous application to both feed and crossfeed by means of an interpolator (in this case a DDA computer). It comprises a speed-control loop governed by the interpolator, and an incremental position-control loop. The biaxial motion may be linear, circular, or combined. The position and speed signals for each step are fed to the system from a command panel comprising a socket matrix with plugs used for "writing." As soon as a given command has been implemented, the system automatically passes on to the next. Transition from step to step is effected through a counter whose output contains a decoding network. The decoder outputs are connected to the command panel, which is scanned row by row. The axis position is measured by means of rotating encoder emitting 1000 pulses per revolution, of which 125 are utilized in ordinary operation. The required accuracy is 1 pulse, equivalent to 0.01 mm.