Experimental Characterization of Electrical Discharge Machining of Aluminum 6061 T6 Alloy using Different Dielectrics

Electrical discharge machining is a non-traditional machining method broadly employed in industries for machining of parts that have typical profiles and require great accuracy. This paper investigates the effects of electrical parameters: pulse-on-time and current on three performance measures (material removal rate, microstructures and electrode wear rate), using distilled water and kerosene as dielectrics. A comparison between dielectrics for the machining of aluminum 6061 T6 alloy material in terms of performance measures was performed. Aluminum 6061 T6 alloy material was selected, because of its growing use in the automotive and aerospace industrial sectors. The experimental sequence was designed using Taguchi technique of L9 orthogonal array by changing three levels of pulse-on-time and current, and test runs were performed separately for each dielectric. The results obtained show that greater electrode wear rate (EWR) and higher material removal rate (MRR) were achieved with distilled water when compared with kerosene. These greater EWR and MRR responses can be attributed to the early breakage of the weak oxide and carbide layers formed on the tool and alloy material surfaces, respectively. The innovative contributions of this study include, but are not limited to, the possibility of machining of aluminum 6061 T6 alloy with graphite electrode to enhance machinability and fast cutting rate employing two different dielectrics.Peer reviewe

Experimental Studies on Machinability of Inconel Super Alloy during Electro-Discharge Machining: Emphasis on Surface Integrity and Metallurgical Characteristics of the EDMed Work Surface

Inconel alloys are Nickel-Chromium based high temperature super alloys widely applied in aerospace, marine, nuclear power generation; chemical, petrochemical and process industries. Execution of traditional machining operations on Inconel super alloy is quite difficult due to its very low thermal conductivity which increases thermal effects during machining operations. Inconel often exhibits strong work hardening behavior, high adhesion characteristics onto the tool face, and thereby alters cutting process parameters to a remarkable extent. Additionally, Inconel may contain hard abrasive particles and carbides that create excessive tool wear; and, hence, surface integrity of the end product appears disappointing. The extent of tool life is substantially reduced. Thus, Inconel super alloys are included in the category of ‘difficult-to-cut’ materials. In view of the difficulties faced during conventional machining, non-traditional machining routes like Electro-Discharge Machining (EDM), Wire Electro-Discharge Machining (WEDM), micro-machining (micro-electro-discharge drilling) etc. are being attempted for processing of Inconel in order to achieve desired contour and intricate geometry of the end product with reasonably good dimensional accuracy. However, low material removal rate and inferior surface integrity seem to be a challenge. In this context, the present dissertation has aimed at investigating machining and machinability aspects of Inconel super alloys (different grades) during electro-discharge machining. Effects of process control parameters (viz. peak discharge current, pulse-on time, gap voltage, duty factor, and flushing pressure) on influencing EDM performance in terms of Material Removal Rate (MRR), Electrode Wear Rate (EWR) and Surface Roughness (SR) of the EDMed Inconel specimens have been examined. Morphology along with topographical features of the EDMed Inconel work surface have been studied in view of severity of surface cracking and extent of white layer depth. Additionally, X-Ray Diffraction (XRD) analysis has been carried out to study metallurgical characteristics of the EDMed work surface of Inconel specimens (viz. phases present and precipitates, extent of grain refinement, crystallite size, and dislocation density etc.) in comparison with that of ‘as received’ parent material. Results, obtained thereof, have been interpreted with relevance to Energy Dispersive X-ray Spectroscopy (EDS) analysis, residual stress and micro-indentation hardness test data. Effort has been made to determine the most appropriate EDM parameters setting to optimize MRR, EWR, along with Ra (roughness average), relative Surface Crack Density (SCD), as well as relative White Layer Thickness (WLT) observed onto the EDMed work surface of Inconel specimens. Moreover, an attempt has been made to examine the ease of electro-discharge machining on Inconel work materials using Deep Cryogenically Treated (DCT) tool/workpiece. A unified attempt has also made to compare surface integrity and metallurgical characteristics of the EDMed Inconel work surface as compared to the EDMed A2 tool steel (SAE 304SS) as well as EDMed Titanium alloy (Ti-6Al-4V)

Investigations on Machining Aspects of Inconel 718 During Wire Electro-Discharge Machining (WEDM): Experimental and Numerical Analysis

Wire electro- discharge machining (WEDM) is known as unique cutting in manufacturing industries, especially in the good tolerance with intricate shape geometry in die industry. In this study the workpiece has been chosen as Inconel 718. Inconel 718 super alloy is widely used in aerospace industries. This nickel based super alloy has excellent resistance to high temperature, mechanical and chemical degradations with toughness and work hardening characteristics materials. Due to these properties, the machinability studies of this material have been carried-out in this study. The machining of Inconel 718 using variation of wire electrode material (brass wire electrode and zinc coated brass wire) with diameter equal to 0.20mm has been carried out. The objective of this study is mainly to investigate the various WEDM process parameters and performance of wire electrodes materials on Inconel 718 with various types of cutting. The optimal process parameter setting for each of wire electrode material has been obtained for multi-objective response. The kerf width, Material Removal Rate (MRR) and surface finish, corner error, corner deviation and angular error are the responses which are function of process variables viz. pulse-on time, discharge current, wire speed, flushing pressure and taper angle. The non-linear regression analysis has been developed for relationship between the process parameter and process characteristics. The optimal parameters setting have been carried out using multi-objective nature-inspired meta-heuristic optimization algorithm such as Whale Optimization Algorithm (WOA) and Gray Wolf Optimizer (GWO). Lastly numerical model analysis has been carried out to determine MRR and residual stress using ANSYS software and MRR model validated with the experimental results. The overlapping approach has been adopted for solving the multi-spark problem and validate with the experimental results

Machining of Stainless Steels and Alloys Using Non-Traditional Machining Processes

Stainless steels and alloys are characterized primarily by their corrosion resistance, high strength, ductility, etc. used for various advanced applications like automotive and aerospace, sugar refineries, construction materials, etc. Many advanced high-speed machineries /systems need fine quality of parts to provide good performance in its working conditions. The machining of stainless steel and its alloys is of interest, because, of its excellent mechanical properties. Stainless steels and alloys are machined generally by traditional machining processes. But complex shapes and features on products are difficult task with the use of traditional metal cutting techniques. To machine the advanced materials to produce high dimensional accuracy and generation of intricate shapes in difficult-to-machine materials like stainless steels and alloys, nontraditional machining (NTM) techniques are now attractive the viable choices. To attain improved machining performance of the NTM processes, it is always necessary to find the optimal combinations of various process input parameters of those processes. In the present chapter, some aspects of machining of stainless steel and alloys using NTM processes such as electric discharge machining (EDM) and wire EDM, are discussed and some concluding remarks have been drawn from the study

Investigations on Tool Wear Rate of AISI D2 Die Steel in EDM using Taguchi Methods

EDM has become an important and cost-effective method of machining extremely tough and brittle electrically conductive materials. It is widely used in the process of making moulds and dies and sections of complex geometry and intricate shapes. The workpiece material selected in this study is AISI D2 Die Steel. The input parameters are voltage, current, pulse on time and pulse off time. L9 orthogonal array was selected as per the Taguchi method. The data have been analyzed using Minitab15 Software. The effect of above mentioned parameters upon machining performance characteristics such as Tool Wear Rate (TWR) are studied and investigated on the machine model C-3822 with PSR-20 Electric Discharge Machine.  The copper alloy was used as tool material.The results obtained showed that the optimum condition for tool wear rate (TWR) is A3, B2, C2, D3 i.e. Ton (40µs),Toff (8 µs), Ip (8 amp) and Vg (60V). The order of process parameters influencing the tool wear rate is Toff 12>"> Ip 12>"> Ton 12>"> Vg. Hence, pulse off parameter has more contribution to tool wear rate whereas gap voltage has the least contribution. As per the optimal level of parameters, the optimum value of TWR is 0.117 mm3/min. These results were validated by conducting confirmation experiments and found satisfactory. Keywords: EDM,TWR, MRR, ANOVA, Taguchi method, AISI D2 Die steel, copper electrod

Investigation and Optimization of Cutting Performance of High Chrome White Cast Iron by Wire Erosion

Wire electric discharge machining (WEDM) is an emerging approach to producing more accurate and precise complex products in the unconventional machining process. The WEDM process is affected by several process factors. Therefore, the appropriate combination of process factors is required to achieve economical and quality machining. Machining is very difficult due to the presence of chromium carbide in the structure of high-Cr white cast irons (HCCIs) with 12–17% Cr content in machining processes. Therefore, the machinability of HCCIs has always been a disadvantage. In this study, specially molded HCCIs samples were subjected to softening, casting (not heat treated) and hardened heat treatment processes, respectively. We aimed to experimentally investigated the changes in HCCIs samples characteristics, pulse on time, pulse of time, wire speed, and cutting performance in the WEDM process in this study. The L18 orthogonal array was used using the Taguchi method, and an experimental study was prepared. Afterward, an optimization study was carried out using mathematical models for WEDM with the help of performance outputs via ANOVA analysis. The experimental performances examined in this study are material removal rate and surface roughness. The experimental study determined that the material removal rate and surface roughness increased when the pulse on time increased. Later, machined samples morphological and structures properties were analyzed X-ray spectroscopy (EDS), scanning electron microscopy, microhardness and surface roughness. Furthermore, electrical conductivity of them was measured. © 2023, King Fahd University of Petroleum & Minerals

Development of Arrayed Structures Using Reverse EDM (R-EDM)

In recent years, reverse electric discharge machining (R-EDM) has been developed as a method for the fabrication of arrayed structures which find applications in the fabrication of fins and component assembly. In this study, the feasibility of R-EDM process in the fabrication of arrayed features of Ø 3 mm and height 2 mm on mild steel has been studied through response surface methodology (RSM) based experimentation. The influence of machining parameters i.e., peak current (Ip), pulse-on time (Ton) and flushing pressure (Fp) on some of the vital response characteristics like material removal rate (MRR), surface roughness (SR), taper, cylindricity error and micro hardness and surface morphology of the pillared structures has been investigated. Further, a hybrid optimization method i.e., principal component analysis (PCA) based grey relational analysis (GRA) technique, is utilized to obtain optimal parameter combination with an aim to improve machining conditions for fabrication of arrayed features during R-EDM process. Analysis of variance (ANOVA) results shows that Ip has significant effect followed by Ton on MRR and Ip has major contribution towards SR, taper and cylindricity error. Micro hardness has maximum value in heat affected zone (HAZ). The optimal parameter combination based on PCA based GRA is found to be Ip = 10 A, Ton = 100 µs and Fp = 0.3 kg/cm2 which was further ascertained using confirmatory tes

Response surface methodology and artificial neural network-based models for predicting performance of wire electrical discharge machining of inconel 718 alloy

This paper deals with the development and comparison of prediction models established using response surface methodology (RSM) and artificial neural network (ANN) for a wire electrical discharge machining (WEDM) process. The WEDM experiments were designed using central composite design (CCD) for machining of Inconel 718 superalloy. During experimentation, the pulse-on-time (TON), pulse-off-time (TOFF), servo-voltage (SV), peak current (IP), and wire tension (WT) were chosen as control factors, whereas, the kerf width (Kf), surface roughness (Ra), and materials removal rate (MRR) were selected as performance attributes. The analysis of variance tests was performed to identify the control factors that significantly affect the performance attributes. The double hidden layer ANN model was developed using a back-propagation ANN algorithm, trained by the experimental results. The prediction accuracy of the established ANN model was found to be superior to the RSM model. Finally, the Non-Dominated Sorting Genetic Algorithm-II (NSGA- II) was implemented to determine the optimum WEDM conditions from multiple objectives

Experimental investigation on low-frequency vibration assisted micro-WEDM of Inconel 718

AbstractThe micro-wire electric discharge machining (micro-WEDM) has emerged as the popular micromachining processes for fabrication of micro-features. However, the low machining rate and poor surface finish are restricting wide applications of this process. Therefore, in this study, an attempt was made to improve machining rate of micro-WEDM with low-frequency workpiece vibration assistance. The gap voltage, capacitance, feed rate and vibrational frequency were chosen as control factors, whereas, the material removal rate (MRR) and kerf width were selected as performance measures while fabricating microchannels in Inconel 718. It was observed that in micro-WEDM, the capacitance is the most significant factor affecting both MRR and kerf width. It was witnessed that the low-frequency workpiece vibration improves the performance of micro-WEDM by improving the MRR due to enhanced flushing conditions and reduced electrode-workpiece adhesion