Digital control of an electro discharge machining (EDM) system
This thesis presents a model of the complete Electro Discharge Machining (EDM) system and the design and implementation of a digital controller for the servomotor control and the gap voltage and current pulse power generator. A Matlab/Simulink simulation is used to investigate the EDM system model behaviour and based on the simulation results, a compensated EDM control system is designed. Simulation studies were also earned out to predict the material removal rate of a steel workpiece in mm3/min . The control software of the EDM control process and servo system control was performed mainly in software with minimal hardware implementation. The control hardware consists of an eZdsp, userinterface device and analogue signal processing and interfacing circuit. The eZdsp communicates with the user-interface device by sending the information/instruction to the LCD screen while the user-interface device uses push button switches to communicate with the eZdsp. It is shown that one DSP microcontroller can be used to provide the control functions for the EDM system. The experimental studies of the Electro Discharge Machining process using a copper electrode, a graphite electrode and steel workpiece materials are presented in tabular and graphical forms. The analysis of the experimental results show that the material removal rate is influenced by the process parameters such as the gap current Igap• gap voltage V arc. pulse on-time Ion, and sparking frequency F, as well as the material properties of the electrode and the workpiece. Comparison studies between simulation and experimental results show reasonable agreement. Further improvement was made to the EDM process model based on the comparison studies. As a result, the predicted material removal rate using the improved EDM process model shows better agreement with experimental results.