Despite these advances, research is still needed on some aspects of electrochemical machining. Current areas needing attention include tool design, process monitoring and control, electrolyte processing, disposal of machining products (known as sludge) and accuracy. The complexity of ECM process makes it difficult to theoretically predict and on-line monitor the interelectrode gap size which greatly affects the ECM performance. Lack of efficient methods of process control hinders the integration of ECM equipment within the modem manufacturing environment. Tool design is often
a costly empirical procedure, rather than an exact science. Significant experience and expert knowledge are required to successfully operate the process. Additionally, ECM generates a large quantity of waste, mainly metal hydroxide sludge. The processing and disposal of the sludge, which may include heavy metals from the workpiece material&' are complex and costly [9].