Josef Stirnimann

Investigation of the Scaling Effects in Meso-Micro EDM

The ability to remove chip volumes in micro-nano scale has enabled implementation of electrical discharge machining (EDM) in high precision and micro-machining of difficult to machine electrically conductive materials, such as metals and ceramics. Despite of its wide spread application in tool making and precision applications, the limited process understanding limits exploitation of the EDM process capabilities. In current work, scaling effects caused due to the electrode projection area and erosion depth have been analysed for the single and multiple discharges. Material removal caused by a single discharge has been simulated using a heat conduction model and validated through the experimental results. However, the paradigm shift in the optimal pulse duration value to obtain high material removal rate observed for multiple discharge process does not correlate to the single discharge removal values, even when considering the discharge frequencies during the erosion. It has been evaluated that this shift originates from the decrease in the efficiency of material removal per spark in actual erosion conditions. Different plasma states generated due to the limited dielectric availability in micro cavities and gas bubble dynamics have been proposed to be the cause for origination of the scaling effects in meso-micro EDM.Copyright

FEASIBILITY STUDY ON THE USE OF FRACTAL ANALYSIS FOR EVALUATING THE SURFACE QUALITY GENERATED BY WATERJET

Original scientific paper The paper presents the fractal analysis application for a simple evaluation of the quality of waterjet treated surfaces, especially after abrasive waterjet cutting. This analysis will enable the elimination of subjective assessments of treated surfaces. This will ensure a clear estimate of the quality of the surface and the ability to objectively compare the quality of the cutting edge obtained by using different cutting parameters.