| In this research project, a new type of grinding-aided electrochemical discharge machining (G-ECDM) hybrid process has been developed, and a corresponding machining system has been designed and built. The material removal mechanism of the G-ECDM process in machining particulate reinforced aluminium alloy composites has been analysed both theoretically and experimentally. A model to reveal the electrical field acting on a hydrogen bubble in ECDM process has been established. A set of experiments was performed to verify the model and the experimental results agreed well with the predicted values.;To further study the G-ECDM mechanism, a series of single pulse studies have been conducted. The results showed that for the G-ECDM process, the grinding action would remove the crater's built-up edge. As a consequence, the material removal rate of G-ECDM was higher than that of ECDM and EDM. Although, the discharge waveform of the G-ECDM process resembles a form of abnormal arcing, the machining process was found to be stable. This is attributed to the rotational motion of the tool-electrode in constantly shifting the arcing position. The differences in the distribution of craters on the machined surface for the ECDM and G-ECDM processes can be satisfactorily explained by analysing the electrical field strength.;By examining tool performance, it was found that machining chips clogged to the tool-electrode, produced by the grinding action could be removed by EDM sparks. The EDM spark thus serves the role of cleaning the tool and as a result, preventing short circuiting from occurring. Moreover, EDM sparks that occurred between the clogged material and the workpiece did not cause any noticeable damage at the interface between the diamond grit and the binding material of the tool-electrode. Therefore, the clogged material provides protection to the tool and as a consequence, a longer tool life is expected from the G-ECDM process. |
