One notable difficulty with ECM, common to a variety of manufacturing operations, is an inability to predict a priori the tool and process parameters required in order to satisfy the final specifications of the fabricated part. In this talk, Faraday will present preliminary results from a Phase I SBIR program aiming to demonstrate the potential for a phenomena-based design platform to predict optimal ECM tool shape using commercially available multiphysics simulation software. This capability is anticipated to dramatically shorten the process/tooling development cycle, eliminating much or all of the iterative prototyping necessary in the absence of a predictive tool. The validation argument will be presented via comparison of simulation results with data from parallel ECM experiments. The initial validation work encompasses a small subset of experimental parameters: electrolyte salt (“active” NaCl vs “passive” NaNO3) and electrolyte flow/tool geometry (“cross flow” past a solid tool, and “through-flow” in a tubular tool). The initial feasibility demonstration of the tool design platform will include only ECM based on potentiostatic direct currents, constant tool advancement rates, and simulations including only primary current distributions. Reasonable agreement between the simulated and experimentally derived profiles is observed. Eventually, however, the goal is to extend the model to other modes of ECM processing, including: 1) pulse-current ECM (PECM), where the tool is withdrawn from the workpiece during pulse current off-times to flush the gap; and also 2) pulse/pulse-reverse ECM (P/PR ECM) in metal-solubilizing electrolytes, where the tool gap is maintained relatively constant. An approach to modeling the optimal inter electrode gap dimension during PECM has been reported by Rajurkar and collaborators [[1]]; to our knowledge no modeling has been performed on constant-gap pulse/pulse-reverse ECM in solubilizing electrolytes. Faraday has developed and patented novel approaches to ECM based on pulse reverse currents [[2],[3],[4]] that do not require complicated electrolytes and results in improved surface finishes and better process control; application of the predictive model to these approaches is anticipated to provide substantial gains in both manufacturing logistics and economics.
The authors acknowledge the financial support of U.S. Army Contract No. W15QKN-16-C-0070.
References
[[1]] B. Wei, K.P. Rajurkar, S. Talpallikar. “Identification of Interelectrode Gap Sizes in Pulse Electrochemical Machining.” J. Electrochemical Society 144(11): 3913-19, 1997.
[[2]] C. Zhou, E.J. Taylor, J. Sun, L. Gebhart, R. Renz. “Electrochemical Machining using Modulated Reverse Electric Fields.” U.S. Patent No. 6,402,931, issued 11 June 2002.