An extensive review on sustainable developments of dry and near-dry electrical discharge machining processes

Electrical discharge machining (EDM) is very essential unconventional electro-thermal machining process to machine the contour profile of hard materials in modern production industries. The liquid dielectric fluid has been replaced by the gas and minimum quantity of liquid mixed with gas (gas-mist) to encourage the green machining processes. The various gases and gas-mist have been used as the working fluid in dry and near-dry EDM respectively. The research-contextual, various dielectric fluids, sustainable and innovative developments, process parameters, machining characteristics, and optimization techniques applied in various dry and near-dry EDM have been illustrated through an extensive literature survey. Future research opportunities in both dry and near-dry EDM have been summarized to promote eco-friendly EDM research activities.

Comparative Analysis of Dry-EDM and Conventional EDM in machining of Hastelloy

Dry EDM may be a modification of the traditional electrical discharge machining (EDM) process during which the liquid dielectric is replaced by a gaseous medium. High velocity gas is supplied through it into the discharge gap. The flow of high velocity gas into the gap facilitates removal of debris and prevents excessive heating of the tool and work piece at the discharge spots. it's now known that aside from being an environment–friendly process, other advantages of the dry EDM process are low tool wear, lower discharge gap, lower residual stresses, smaller white layer and smaller heat affected zone.[1] Keeping literature review into consideration, during this research, an effort has been made by selecting compressed gas as a dielectric medium, with Hastelloy as a work piece material and copper as a tool electrode. Conventional experiments were also performed. Experiments are performed using Taguchi DoE orthogonal array to watch and analysis the consequences of various process parameters to optimize the response variables like material removal rate (MRR) and gear wear rate (TWR).

Simulation and experimental investigation of tool wear rate in dry and near-dry EDM process

Purpose Many engineering applications in this era require new age materials; however, some classic alloys like spring steel are still used in critical applications such as aerospace, defense and automobile. To machine spring steel material, there exist various difficulties such as rapid tool wear rate, the rough surface formation of a workpiece and higher power consumption. The purpose of this paper is to address these issues, various approaches in addition to electrical discharge machines (EDM) are used such as dry EDM (DEDM) and near dry EDM (NDEDM). Design/methodology/approach This study focuses on these two approaches and their comparative analysis with respect to tool wear during machining of spring steel material. For this study, current, gap voltage, cycle time and dielectric medium pressure are considered input variables. This study shows that the near dry EDM approach yields better results. Hence, the thermo-electrical model for this approach is developed using ANSYS workbench, which is further validated by comparing with experimental results. This thermo-electrical model covers spark radius variation and formation of temperature profile due to electric discharge. Transient thermal analysis is used to simulate the electric discharge machining. Findings It is observed from this study that discharge environment parameters such as debris concentration and fluid viscosity largely influences the dielectric fluid pressure value. Experimental results revealed that NDEDM yields better results in comparison with DEDM as it shows a 25% lesser tool wear rate in NDEDM. Originality/value The range of predicted results and the experimental results are in close agreement, authenticating the model.

Comparison of surface characteristics and micro hardness of AISI D2 tool steel and LM13 aluminum alloy machined under dry EDM (green machining) process

In this experimental work, the micro structure and the micro hardness of the surfaces machined under the dry EDM process is analyzed for AISI D2 tool steel and LM13 aluminum alloy. The experiments were conducted using copper tool electrode. Few modifications were made in the tool for conducting the experiments under dry EDM process. Discharge current, pulse on time, voltage, pressure, tool rotational speed and the duty factor were used as the various process parameters and their influence over the micro structure and micro hardness of the machined surfaces were analyzed. Better results were observed in the dry EDM process for AISI D2 tool steel, whereas dry EDM process did not reveal appreciable results for LM13 aluminum alloy.

Modeling of Dry-EDM Plasma Discharge

There is a growing interest in developing the dry EDM process as a sustainable alternative to the conventional liquid dielectric-based EDM process. It is shown that the dry EDM process possesses advantages over the conventional process in terms of thermal damage, recast layer, and tool wear. However, there is a need to increase the productivity of the dry EDM process for its successful adaptation in the industry. This paper presents a model of dry EDM plasma discharge with air as the dielectric medium. The model uses global modeling (‘0D’) approach in which equations of mass balance, energy balance, and plasma expansion are solved simultaneously to obtain a time-dependent description of the plasma in terms of its composition, temperature, diameter, and heat flux to electrodes. The model includes reaction kinetics involving 622 reactions and 55 species to determine the air plasma composition. A single discharge dry EDM operation is successfully simulated using the model, and the effect of discharge current on the plasma is studied. An increase in the discharge current increases the electron density, temperature, and diameter of the plasma linearly, while heat flux to the workpiece increases exponentially. Overall, the model provides an essential tool to study the dry EDM process mechanisms at a fundamental level and devise methods for process improvements.

Dentale Implantatstrukturen aus CrCoMo/Near-dry EDM of CrCoMo dental implant structures

Die Funkenerosion wird in der Dentalindustrie zur Herstellung von hochpräzisem Zahnersatz aus CrCoMo eingesetzt. Dieser Beitrag stellt die Strategie und Technologie der halbtrockenen Funkenerosion von CrCoMo-Dentalbrücken vor. Als Dielektrikum kommt ein Wasser-Luft-Gemisch zum Einsatz, dass durch ein speziell entwickeltes Spülsystem durch die Kupfer-Werkzeugelektrode in die Erodierzone injiziert wird. Um die Effizienz des halbtrockenen Erodierprozesses zu erhöhen, werden die grundlegenden Zusammenhänge zwischen ausgewählten Prozessgrößen experimentell untersucht. Electrical discharge machining (EDM) is used in dental industry for the manufacturing of high-precision dentures from CrCoMo. This article presents the strategy and technology of near-dry EDM of CrCoMo dental bridges. A water-air mixture, which is injected through the copper tool electrode into the erosion zone by a specially developed flushing system is used as dielectric. In order to increase the efficiency of the near-dry EDM process, the basic relationships between the influencing process variables are investigated experimentally.