R. Sagar, Netaji Subhash Instute of Technology, Delhi, India

Abstract

Electric Discharge Machining provides a method of making transverse through holes in a stent. It has the advantage that the heat input is minimum to the work piece, the process is almost stress free, and is independent of work piece hardness. The tool for making the hole has less hardness than the work piece. The tool itself is a hollow tube. It helps in flushing the die-electric more effectively. Experiments have been conducted to determine optimum operating parameters such as current, time duration, and die electric flow rate. The roundness, and taper of the hole generated are also checked. The shape memory properties of the stent with drilled hole are determined and it is found that they are satisfactory. The shape memory alloy Nitinol (Ni-Nickel, Ti-Titanium) attracted lot of attention for its engineering applications.  It has a marvelous application in vibration suppression, biomedical engineering e.t.c. Nitinol has low thermal conductivity, high resistivity and is fatigue and corrosion resistant. One of the most important aspects of Nitinol is its ability to experience large, reproducible shape recovery after temperature cycling. EDM does not make direct contacts between the electrode and work piece thereby eliminating mechanical stresses, chatter and vibrations.