Experimental investigation of spark generation in electrochemical discharge machining of non-conducting materials

• We fabricated tapered tool electrodes with sharp tip to investigate spark generation.
• Energy of sparks was stochastically modeled with mixture log-normal distribution.
• The average energy of single spark was estimated.
• We correlated material removal with machining energy with a finite element model.
• Holes were drilled with tapered tools and are consistent with predictions.

Electrochemical discharge machining (ECDM), also known as spark assisted chemical engraving (SACE), is an effective micro-machining process for non-conducting materials. Process modeling of ECDM, including spark generation and material removal, is not fully established however. Empirical estimation for discharge energy results in large prediction error of material removal and is hard to experimentally validate. In this paper, an experiment-based stochastic model for spark energy estimation is presented. Tapered tool electrodes were fabricated by electrochemical machining (ECM) to improve the consistency of spark generation. Energy of sparks was experimentally determined and fit into a two-component mixture log-normal distribution to reveal electrochemical characteristics of tool electrodes. A finite element based model was established to correlate spark energy and the geometry of removed material. Material removal was treated as heat transfer problem because electrical energy released by spark generation transfers into thermal energy on the workpiece, resulting in material removal due to thermal melting and chemical etching. Predictions of material removal by the model demonstrated good consistency with experimental results.