Improvement on µ-electro discharge machining process

In the case of micro electro discharge machining (µEDM) processes, they have been analysed within the project following the difficulties stated by the industrial end-user Sarix. The main problem found when analysing these processes is the appearance of a wrong inter-electrode gap due to the generation wear on the electrode working as the tool or the wrong positioning of the machine axes. Besides, due to the nature of the process itself the part material is modified during the machining, generating a heat affected zone (HAZ) on the machined surfaces that can be detrimental for the mechanical behaviour of the part. On the one hand, the proper identification of the actual electrode geometry has been undertaken by the University of Leuven and BLUM-Novotest. By both contact (electrical spark analysis) and non-contact methods (laser system), an electrode measurement routine has been developed obtaining measurement uncertainties below 0,5 µm. Once developed an accurate way for the identification of the electrode geometry, the University of Leuven has carried out several experimental tests in order to analyse the wear generation along the µEDM process and implement the obtained results into a model for its application to actual machining processes. This model has been introduced by Sarix into their NC system, allowing the automatic tool wear compensation on µEDM milling operations Also, thanks to the possibility to accurately identify the contact between the electrode and a machined surface and the better understanding of the electrode wearing along the µEDM process, Sarix has added several features on their own CAM for the improvement of the depth accuracy on the machined features and the generation of optimized tool paths yielding considerably lower processing times. Besides, Tagueri has worked on a system for the analysis of single sparks up to a frequency rate of 100 Mhz. This analysis has enabled the in-line identification of ‘good’ and ‘bad’ sparks during a µEDM process, making it possible to detect variations or trends along a machining process. The in-line application of this analysis can help aid the machine operator on decision making related to the modification of process parameters or even the stopping of a process based on the historical data and the observations during the machining process. Finally, trying to face the material modification (HAZ) during the µEDM process, the University of Brunel has worked on the development of a machine prototype for micro electro chemical machining (µECM). Due to the chemical nature of this process, it is possible to remove part material without modifying its state. After the development of a machine structure, an innovative pulse generator and a new control system, the performance of the prototype has been proven on the manufacturing of micro stylus for precision probes.