Probir Saha

Multi-objective optimization in wire-electro-discharge machining of TiC reinforced composite through Neuro-Genetic technique

This paper proposed a Neuro-Genetic technique to optimize the multi-response of wire electro-discharge machining (WEDM) process. The technique was developed through hybridization of a radial basis function network (RBFN) and non-dominated sorting genetic algorithm (NSGA-II). The machining was done on 5vol% titanium carbide (TiC) reinforced austenitic manganese steel metal matrix composite (MMC). The proposed Neuro-Genetic technique was found to be potential in finding several optimal input machining conditions which can satisfy wide requirements of a process engineer and help in efficient utilization of WEDM in industry.

A New Approach of Tool Wear Monitoring and Compensation in RµEDM Process

This paper presents a new approach of tool wear compensation based on “volume removal per discharge” (VRD) in “reverse-micro-electrical-discharge machining.” In this process, a plate with predrilled microhole is used as a tool, the erosion of which limits the fabrication of desired height of microrod(s). Therefore, in order to achieve the dimensional accuracy of this microrod(s), such tool plate wear needs to be compensated. Since this approach is based on the real-time estimation of volume removal from workpiece, which is obtained by multiplying the number of “contributing” pulses with VRD, an accurate estimation of VRD is very much essential for availing correct tool wear compensation. In this work, VRD is estimated by considering two new aspects: the number of actual “contributing” pulses and the variation of VRD with machining depth. These pulses are identified by a “pulse discriminating” system developed in house. The real-time material removal volume from workpiece is then used to estimate the “real-time height” of microrods after considering the over cut and taperness of each microrod. The proposed method is also compared with the normal machining method and “uniform wear method” and found to be more accurate with a negligible error of maximum 1.7%.

Feasibility of using modified VPP approach in prediction of real time volume estimator (VRT) in µEDM–drilling

In this work, authors have proposed a modified volume removal per pulse (VPP) approach to predict real time volume estimator (VRT) in µEDM–drilling. The present trend to compensate tool wear in µEDM–drilling uses the difference between target volume and the predicted VRT. Therefore, an accurate prediction of VRT is very important to achieve good dimensional accuracy. Here, target volume refers to the desired volume of the machined hole. According to the proposed approach, VPP was estimated considering two new aspects. First one is the number of actual contributing pulses (Np) and latter one is the variation of VPP with respect to the machining depth. The pulses were identified by a newly developed pulse discrimination (PD) system. The validation results confirm well acceptability of the proposed approach in prediction of VRT. This predicted VRT, in combination with the target volume, could be used for online tool wear compensation in µEDM–drilling.

Development of an algorithm for online pulse discrimination in micro-EDM using current and voltage sensors and their comparison

Voltage pulse or current pulse can be used as the main monitoring parameter of the sparks that occur in micro electrical discharge machining (μEDM) process. The spark gap should be monitored for many purposes including study of material removal characteristics, which can be followed by tool wear monitoring and compensation. The system which fulfils the requirements of monitoring spark gap by using gap waveforms is called pulse discriminating (PD) system. The purpose of this research is to compare the capability of effective pulse discrimination using voltage and current pulses by online application of an algorithm written in LABVIEW separately. The comparison is based on the evaluation of the following responses - effective counting of total number of pulses and percentage of different kind of pulses that exist in μEDM.

Development and Analysis of Butt and Lap Welds in Micro-friction Stir Welding (µFSW)

Manufacturing of the ever smaller components, be it mechanical, electronic, etc., is being chased now a days. Likewise in friction stir welding (FSW), when the thickness of the joining plates is reduced to less than 1 mm, i.e. micro-friction stir welding (µFSW), the application areas relate to joining thin-walled structures in electrical, electronic and micro-mechanical assemblies and in the packaging industry. The advantages of FSW like it being a solid state process, it not requiring any shielding gases or fluxes and its possibility to weld dissimilar and different thickness alloys emphasize the use of it to weld micro-thickness plates. In the present work, commercial grade AA6XXX series aluminium alloys of thickness 0.44 mm have been welded together in both butt and lap fashion. Tests have been conducted to measure the joint’s tensile strength (by conducting both transverse and longitudinal tension tests) and the micro-hardness. The use of lap welds in application areas of µFSW has been established.

Optimization of Process Parameters in Micro Electro- Discharge Drilling [micro EDM-Drilling]: A Taguchi Approach

This paper applies Taguchi methodology to optimize the machining parameters in micro EDM-drilling of copper using a tungsten carbide tool electrode. The experimental design has been applied to find out the optimal combination of process parameters corresponding to maximum material removal rate, minimum over-cut, minimum tool wear ratio and minimum error-in-depth of drilled hole. Orthogonal array and signal-to-noise ratio is employed to optimize the process parameter. Analysis of variance (ANOVA) is performed to determine the influence of parameters such as, gap voltage, capacitance, feed rate and spindle rotationof micro EDM-drilling process on the performance measures. From the analysis, it is concluded that gap-voltage and capacitance arethe most significant parameters whereas spindle speed is the least among all.