Sergiu Nanu

Experimental Study on Unsynchronized Ultrasonic Assistance of Electro Discharge Machining Process

The paper deals with experimental study on unsynchronised (out of phase) ultrasonic assistance (US) of electrical discharge machining (EDM) process, considering finishing and semi-finishing operations. The main output technological parameters at classic EDM are not as good as they are expected due to instability of material removal process and long duration of gas bubble formed around plasma channel. The US longitudinal oscillations of electrode-tool produce cavitation within frontal working gap leading to collective implosion of gas bubbles. This hydraulic phenomenon can remove the workpiece material in solid or plastic state or even in liquid state. The goal of our study is to emphasize and quantify the influence of US assistance into EDM process and also to determine a correlation between EDM and US parameters, considering an unsynchronised condition. Nevertheless some optimization conditions of working parameters are needed to attain notable expected performances. From experimental data analysis, it can be noticed that significant growth in process productivity is achieved when EDM process frequency is equal with the ultrasonic assistance frequency.

Aspects of Finite Element Analysis of Microdrilling by Ultrasonically Aided EDM and Related Knowledge Management

Ultrasonic vibrations of electrode-tool and workpiece were applied successfully in specific cases to increase some parameters at micro-EDM, this working mode being characterized through machining instability due to vary narrow working gap. Our researches proved that all main technological parameters of micro-EDM can be improved by ultrasonic aiding (μEDM+US) in terms of machining rate, volumetric relative wear and surface roughness if some optimization conditions of working parameters are fulfilled. A multiphysics Finite Element Analysis (FEA) of material removal mechanism was achieved using two time dependent modules of Comsol 4.2 in order to attain the working parameters optimization. The FEA results compared to experimental data aiming at model validation led to some useful measures to optimize the working parameters. The knowledge management process was approached in order to suggest how human resource from an organization that uses μEDM+US can apply and improve the research results. Our EDM+US strategy is based on relative long pulse time with very low current overlapped on collective bubbles implosion occurring at the final of a liquid ultrasonic stretching semiperiod, and relative low consumed power on ultrasonic chain, contributing to increase the main output technological parameters mentioned above.

Specific Aspects on Modelling and Simulation of the Synchronized Ultrasonic Assistance of the Electro-Discharge Machining Process

The context of our research is based on the conclusion that simulation is used to describe and analyse the behavior of an existing or conceptual system. Electro discharge machining aided by ultrasonics EDM+US (as well as micro) is a complicated process that requires a powerfull tool to simulate. In this study we considered COMSOL multiphysics FEA software, using our own developed parametric model based on literature survey knowledge and our own previuos researches on subject. Some preliminary simulations results and conclusions are also presented.