Advanced CAD integrated approach for 3D electrochemical machining simulations

Many cathode tool/work piece configurations as encountered in electrochemical machining (ECM) processes can only be analysed by real 3D modelling, rather than 2D or axi-symmetrical cross-sections. This paper presents an advanced CAD integrated approach for 3D simulations with strong non-linear boundary conditions including reaction efficiency and moving cathode tools. The simulation tool is completely integrated in the computer-aided design (CAD) package SolidWorks®, which enables to perform the ECM configuration from scratch, or by reading in existing CAD files (STEP, AutoCad, IGES, etc.). The software tool can visualize the electrode shape change profile at different stages of the process and presents current densities and potential distributions using colour plots, isolines and streamlines. The electrochemical process model assumes that the electrolyte is well stirred and refreshed such that the current density in the bulk and at the electrodes is governed by the Laplace equation. At the interfaces between electrodes and electrolyte, non-linear boundary conditions apply for modelling the electrode reactions. The whole geometry is discretized using tetrahedrons and the finite element method (FEM) is applied to compute the potential field distribution. The electrode shape is found by displacing the nodes on the work piece surface proportional with, and in the direction of the local current density according to Faraday's law, taking into account the efficiency of the dissolution reaction. At each time step the complete CAD model can be reconstructed as a direct input for the next computational step especially when the discretized model expects topology changes. An example deals with slot ECM of a stainless steel plate up to perforation. Three-dimensional results are compared with available data from 2D cross-section simulations. This allows to check the accuracy of the 3D ECM algorithm.