An Experimental Investigation of Travelling Wire Electrochemical Spark Machining (tw-ecsm) of Epoxy Glass Using One-parameter-at-a-time (opat)

Electrochemical spark machining (ECSM) is hybrid machining process which is the controlled removal of metal by anodic dissolution as well as erosion in an electrolytic cell in which the workpiece is the anode and the tool is cathode. The experimental investigation with the developed TW-ECSM set-up has been needed to understand the behaviour of the process parameters on performance characteristics. One-Parameter-At-a-Time (OPAT) approach is extensively used to study the behaviour of newly developed process. This approach requires to find the suitable range of control parameters for desired outputs. In this technique, only one parameter is varied at a time in wide range while other parameters are kept at constant .In similar way, the effect of all individual control parameter on output is investigated. Epoxy glass, which is frequently used as a material for fabrication of micro structures, was used as a workpiece. In order to achieve the effective and controlled material machining, the following input process parameters are optimally controlled such as Applied Voltage, Wire velocity, Electrolyte concentration and Duty factor. The machining criteria during the TW-ECSM operation can be considered as Material removal rate (MRR).The experimental setup of TWECSM of the process parameters are to be properly controlled to achieve the good machining performance. KeywordsTraveling wire Electrochemical Spark Machining (TW-ECSM), Epoxy glass, Metal removal rate (MRR), OneParameter-At-a-Time (OPAT). 1.Introduction The advantages of electrochemical spark machining (ECSM) is an advanced hybrid machining process comprising the techniques of Electrochemical Machining (ECM) and Electro discharge Machining (EDM).The process is important since it can machine a variety of electrically non-conductive materials like ceramics, composites, alumina, glass etc. The recent developments in non-conductive are focused not only on improvements of strength and toughness, but also on possibilities for difficult-to-machine shapes. In 1968, Late Professor H. Kurafugi explained the method of machining of hole in glass using an electrolyte discharge system. Researchers have carried out studies for exploring the insight of the ECSM and TW-ECSM process for effective utilization and greater application of the process. Peng, and Liao[1] used their self developed TW-ECDM setup to slice small size (1030mm) bars of optical glass and quartz. They investigated the feasibility of electrical-thermal etching effect and electrolyte supply plays a major role for releasing stronger spark. They found that pulsed DC power gives better spark stability and more spark energy than constant DC power. Tandon et al.[2] carried out experimental study to find the effect of change in applied voltage across the electrodes and specific conductance of the electrolyte on MRR, tool wear rate (TWR) and radial overcut (ROC) during sinking-ECSM of Kevlar-fiber-epoxy and glass-fiber-epoxy composites. A parametric study of the process was performed using a design of experiment concept as well as a “one variable at a time” approach. MRR,TWR, ROC had found to increase and relative tool wear was found to decrease with an increase in applied voltage across the electrodes. Bhattacharyya et al.[3] proposed a new technology for the electrochemical discharge machining (ECDM) process has a potential in the machining of silicon nitride ceramics. They found that MRR increases with increase in applied voltage and electrolyte concentration but overcut increases with increase in electrolyte concentration. They observed that micro-cracks and other defects are generated on the machined surface at higher voltage. They have reported that the most effective range of parametric combinations for moderately higher machining rate and dimensional accuracy is centered around 80 V applied voltage and 25% NaOH electrolyte solution. They also found that the tool tip shape is a prominent factor for controlling spark generation. Yang,et al [4] explored the wettability and machining characteristics of different tool electrode materials and their impact on gas film formation during ECSM process. Different tool materials have different optimal voltages, which determine the gas film formation, and hence, achieved the hole diameter and average current. With varies wettability, surface roughness of tool electrode is key determinant of gas film formation. Han, et al [5] performed microelectrochemical discharge cutting of soda-lime glass using a cylindrical surface-textured electrode. They introduced that wire surface roughening is proposed to enhance spark discharge distribution over the tool surface and lower the working voltage. Fascio et al [12] proposed that micro fabrication of Pyrex glass is one of the key processes. Several applications need glass because of its unique properties like its chemical resistance, transparency, low electrical and thermal conductivity or biocompatibility. Kulkarni et al [16] analyzed * Corresponding Author ELK Asia Pacific Journals – Special Issue ISBN: 978-81-930411-4-7 the spark mechanisms in ECSM with an experimental study. In this work he had been made to measure the time varying current during this process to reveal the basic mechanisms of temperature rise and MRR.Jain et al. [12] conducted many experiments for machining of electrically non conducting materials like ceramics, composites, cermets etc. by electro chemical spark machining process. They had shown rotation of tool had improved the machining depth. When the machining depth was maximum, and orbital rotational tool was used. They described the geometrical parameters and surface integrity of the machine surface had studied and described the material removal process that was basically thermal phenomena. Manna and Kundal [13] developed an experimental TW-ECSM setup and verified experimentally the feasibility of the fabricated setup during machining of aluminum oxide (Al2O3). They conducted experiments based on Taguchi design to investigate the effect of process parameters such as supply voltage, electrolyte concentration, gap between tool and anode and wire speed on outputs MRR and spark gap width. They also observed irregular and scattered machined surface after fins and slicing due to the adhering of small particles scattered from the work surface during cutting and are not flashed out by the die electric fluid flow.First time a theoretical investigation of TW-ECSM process was proposed by Panda and Yadava [14]. They developed a 3-D finite element transient thermal model for the determination of temperature field and finally for the calculation of MRR considering Gaussian distributed input heat flux of the electro-chemical spark. They computed the temperature field in the workpiece using Galerkin’s FEM and then MRR using this temperature field. The calculated MRR was compared with the experimental MRR. Computational experiments were also performed for the determination of energy partition and spark radius of a single spark. They studied the effect of various input process parameters such as energy partition, duty factor, spark radius and ejection efficiency on MRR. They found that the MRR increases with increase in energy partition, duty factor, and ejection efficiency but decreases with increase in spark radius.