DEVELOPMENT OF HYBRID EDM ELECTRODE FOR IMPROVING SURFACE MORPHOLOGY

Abstract

Electric Discharge Machining (EDM) is an important method for the machining or drilling holes, especially for difficult to machine materials. In EDM, materials removal starts when a potential difference is applied between the workpiece and tool electrode. This voltage is high enough to produce a spark between two electrodes. The spark melts and vaporizes a small material volume on each of the electrodes. The dielectric fluid that fills the gap between the electrodes flushes part of this material for working zone. The circulation on dielectric and the removal on machine-debris are very difficult, specially when the hole or the cavity becomes deep, which reduce the machining efficiency due to poor flow of dielectric fluid from the working gap. This poor flushing ends up with stagnation of dielectric and build-up of machining residues which apart from low material removal rate (MRR) also lead to short circuits, arcs and low surface finish. To improve the machining performance of EDM, a combined method of Electric Discharge Grinding EDG and Electric Discharge Machining has been developed. Most of the researchers have applied rotational motion to traditional electrode only. By this method due to rotation of electrode, dielectric circulation and debris removal improves. However, rotational head attachment of EDM is a very costly arrangement. In order to solve the problem stated above, in this research a new hybrid electrode was developed. The most noteworthy feature of the method using this hybrid electrode is that it removes the metal by abrasive action of ceramic material also, as in traditional EDM machining there is no as such action performed. The major advantage of ceramic material attached to the EDM electrode is that it removes metal by abrasive action. The objective of the present work is to investigate the effects of the various Developed Hybrid Electric Discharge Machine Electrode (HEDME) process parameters on the machining performance and to obtain the optimal sets of process parameters so that the performance of the developed hybrid machine can be enhanced. The Taguchi technique has been used to investigate the effects of the HEDME process parameters to predict optimal parameters. In the experimentation Taguchi L9 orthogonal array was used with Hybrid Electric Discharge Machine Electrode and it is explored with EN31 High Carbon Alloy Steel as workpiece. vii The literature survey has revealed that a very little research has been conducted to obtain the optimal levels of machining parameters that yield the best machining quality in machining of difficult-to-machine materials like High Carbon Alloy Steel. This steel is widely used in die and punch in manufacturing with expected application growth in the rapidly developing micro world. With its exceptional hardness, wear resistance and high mechanical strength it is becoming very desirable for a number of applications.