3D CFD simulation of electrochemical machining based on dissolving characteristics within the SIREKA joint research project

Within the BMBF funded research project SIREKA, the project partners CFX Berlin Software GmbH, SITEC Industrietechnologie GmbH, Fraunhofer Institute for Machine Tools and Forming Technology, and alphacam GmbH develop in cooperation with the Technische Universität Chemnitz a simulation model prototype to simulate and optimize electrochemical machining (ECM) [1]. CFD simulations of electrolyte flow and metal dissolving together with experimentally determined dissolving characteristics are used to examine the ECM process in detail. The optimized cathode shape is exported as STL data file and generated in short time via rapid prototyping. With a metal coating, it can be directly used to validate the simulation results and also for production purposes. This presentation shows results of the 3D simulation of the ECM process for basic electrode shapes, e.g. half sphere, cone, pyramid, and cube. The simulations include the calculation of electric potential distribution and mesh deformation due to metal dissolving. The dissolving speed is calculated from experimentally determined characteristic curves as a function of current density and power supply properties [2]. During the surface deformation, mesh quality decreases locally so that remeshing is occasionally necessary. This is done automatically by extracting the deformed surfaces as STL files, remeshing the deformed geometry with tetrahedrons and prisms and restarting the simulation from the latest result. The simulation uses a commercial finite-volume computational fluid dynamics (CFD) solver so that electrolyte flow, turbulence effects, gas and heat generation can be included in the simulation to extend the model towards ab-initio modelling. The simulation results are compared to experimental results that were produced at Fraunhofer IWU. For this purpose a half sphere cathode was used for the removal experiments. The process parameters like feed rate and voltage were calculated also from experimentally determined characteristic curves of the stainless steel 1.4301 [2]. After the removal experiments the machined shapes were measured with a 3 axis coordinate measuring machine. Subsequently the geometries of simulation and removal experiment were compared and the deviations were determined.