Multiphysics simulation of the electrochemical finishing of micro bores

Abstract

For several high-precision applications, especially in hydraulic systems and fuel injectors, micro bores are needed. In most cases the shape of the injection hole, especially the edge rounding, has a significant influence on the atomization fluids and therefore on the combustion process [1]. Usually these micro bores are machined by electrical discharge machining (EDM) [2]. Due to the process characteristics of EDM sharp edges arise and a specific influence on t edge shape is not possible. For this reason a specific adjustment of the edge rounding is required. Therefore an Electrochemical Machining (ECM) process has been developed in cooperation of Chemnitz University of Technology and Fraunhofer Institute for Machine Tools and Forming Technology IWU, SITEC Industrietechnologie GmbH and Continental Automotive GmbH [3]. To characterize the process of the electrochemical finishing of micro bores several models have been developed with COMSOL Multiphysics. In the first model the coupling between the application mode electric current and deformed geometry was applied to investigate the erosion process. By help of this model the machined geometry after a processing time of 1 s could be simulated. In a more complex model the non-isothermal fluid ow was anal. It could be observed that the temperature distribution has a less influence on t electrical conductivity of the electrolyte and therefore also on the current density, which determines the edge rounding process. Selected results of the simulations are validated with experimental ones