Characteristics and improvement of the double-pass electro-chemical discharge machining

Glass and ceramics have broad applications in modern industries; however, unique properties such as brittleness, and low machinability limit their fabrication processes. This way, electro-chemical discharge machining (ECDM) is a new method that can shape hard, brittle, and non-conductive materials. ECDM improvement is the subject of recent investigations through the application of chemical and physical phenomena. Current research studies the accuracy and surface integrity (cracks and HAZ) aspects of the double-pass ECDM process (DP) which is a new and straightforward method. During the double-pass process, two sequential passes are employed to shape the final geometry. In addition, the variable voltage technique is studied to achieve higher machining efficiency in DP. Results showed that in the diameter difference of 100 µm, the double-pass process reduced overcut by up to 21% compared to the typical ECDM process. Also, the size and number of cracks and the extent of HAZ were significantly decreased. Finally, in the diameter difference larger than 300 μm (the constant voltage of 32 V), the enhancement modification (variable voltage) reduced the overcut by more than 80%. At the same time, depth results remained close (less than 5% difference) to the simple ECDM process.