Experimental Investigations into Traveling Wire Electrochemical Spark Machining (TW-ECSM) of Composites

Abstract

Fiber reinforced composites, though relatively new, have already become important engineering materials. So far the main emphasis of research has been on the development of materials, but nowadays more attention is being paid to the industrial manufacture of products made of composites. Conventional machining methods and some unconventional machining methods like laser beam machining (LBM) and water jet machining (WJM) cannot be effectively applied for machining of composites due to the resulting problems of air borne dust, tool wear, and thermal damage. Recently electrochemical spark machining (ECSM) has been applied for the cutting and drilling of holes in composites. The success achieved in the application of ECSM for cutting of composites has stimulated interest in exploring the prospects of use of traveling wire electrochemical spark machining (TW-ECSM) process for cutting of composites. An apparatus for TW-ECSM is designed and fabricated in the laboratory. The results about the feasibility of the process and its performance during machining of composites are presented in this paper. Experiments are carried out on glass-epoxy and kevlar-epoxy composites, using sodium hydroxide (NaOH) as electrolyte. The wire and the workpiece were kept in physical contact with each other by the use of a gravity feed mechanism. The effects of voltage and concentration of the electrolyte on material removal rate, average diametral overcut, tool wear rate, and wire erosion ratio are reported. The theoretical analysis of the mechanism of the process identifies the thermo-mechanical phenomena as the main source of material removal in ECSM.

The path towards delamination-free drilling of composite materials

“…The glass-epoxy and aramid-epoxy laminates can be cut by ECSM [112][113][114]. The effects of voltage, electrolyte conductivity, fiber volume fraction and tool diameter on material removal rate, tool wear and overcut have been studied.…”

“…When a direct current is applied, hydrogen gas bubbles form at the surface of the cathode and the sparking occurs across these bubbles but not between electrodes. The mechanisms for material removal are melting and vaporization of the work material that is evidence by micrographs of the cut surfaces and mechanical erosion due to cavitation of the gas bubbles rupturing on the workpiece [114].…”

“…In this process, two electrodes are placed in a tank filled with an electrolyte such as an aqueous solution of NaCl or NaOH [114]. The tool is the cathode and could be a die [113] as in EDM.…”

Parametric analysis on electrochemical discharge machining of silicon nitride ceramics

“…material removal rate and radial overcut) are influenced by process parameters [10,11] such as applied voltage, electrolyte concentration and inter-electrode gap during an ECDM operation on non-conducting ceramic materials. Therefore, there is an urgent need of establishing the mathematical relationship between the process parameters and the criteria for obtaining optimal machining conditions.…”

Electrochemical Discharge Machining Process

“…Use of electrochemical spark (ECS) for machining of nonconductive materials such as ceramics [5][6][7][8][9] , glass [10][11][12] , composites 13 , and alumina 14,15 has been successfully carried out. Kulkarni 16,17 , et al have successfully explained the ECS process investigating the basic discharge mechanism by experimental measurements.…”