The computer numerical control(CNC) system has many advantages compared to the conventional numerical control system. It has more flexibility by using softwares rather than hardwares, and it can perform more complicated jobs. Also, diagnostic programs for maintenance purpose can be stored in memory which facilitates the maintenance.
In this dissertation, the CNC system retrofitting a conventional lathe is designed and constructed. Using hydraulic system as actuator, a closed-loop control system is constructed. For the purpose of controlling this system, minicomputer PDP-8/E is used and some suitable softwares are developed, which enable the on-line control of the machine-tool.