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Effects of Pulse Duration and Current on EDM Process of Allegheny Ludlum D2 Tool Steel
Abstract
The purpose of this paper is to study the effect of current on performance of EDM process of Allegheny Ludlum D2 Tool Steel (UNS T30402). The effect of varying the machining parameters on the machining responses such as material removal rate (MRR), electrode wear rate (EWR), and surface roughness (Ra) have been investigated. In this study, circular shape of copper was used as an electrode with surface area of 100mm². The experiments were repeated for three different values of pulse duration (100µs, 200µs and 400µs) with combination of three different values of discharge current (12A, 16A and 24A). It was found that the pulse duration and current give significant effect on MRR, EWR and Ra. An increase in the pulse durations causes an increase in the MRR and Ra, but a decrease in the EWR. Meanwhile, the effect of currents on EDM performance shows that the increasing currents led to an increase in the MRR, EWR and Ra.
In this study, the electro discharge machinability of spark plasma sintered ceramics such as AlN and SiAlON, which achieves almost the same electrical conductivity level with the addition of GPLs, were comparatively investigated depending on anisotropic thermal and electrical conductivity. The lower thermal conductivity of both materials in the through-plane direction than in-plane direction led to higher surface roughness and material removal rates in the through-plane direction machining. Similarly, the lower thermal conductivity of GPLs-SiAlON than GLPs-AlN in both machining directions resulted in rougher machined surfaces and relatively higher material removal rate values. Due to the generation of the strong spark, higher material removal rate but lower surface quality obtained at high pulse current compared to low pulse current. Microstructures and EDS-SEM analyzes showed that melting + evaporation and oxidation + decomposition were effective material removal mechanisms. Through-plane direction processing was suitable when a high material removal rate was required, while in-plane direction processing could be preferred for good machining surface quality.
In this paper, the cutting of Tungsten Carbide ceramic using electro-discharge machining (EDM) with a graphite electrode by using Taguchi methodology has been reported. The Taguchi method is used to formulate the experimental layout, to analyse the effect of each parameter on the machining characteristics, and to predict the optimal choice for each EDM parameter such as peak current, voltage, pulse duration and interval time. It is found that these parameters have a significant influence on machining characteristic such as metal removal rate (MRR), electrode wear rate (EWR) and surface roughness (SR). The analysis of the Taguchi method reveals that, in general the peak current significantly affects the EWR and SR, while, the pulse duration mainly affects the MRR. Experimental results are provided to verify this approach.
Metal matrix composites (MMCs) contain certain amount of secondary reinforcement, which makes it difficult to machine with conventional cutting tools and methods. The present study analyses the effect of electric discharge machining (EDM) parameters namely polarity, current, electrode material, pulse duration, and rotation of electrode on metal removal rate (MRR), tool wear rate (TWR) and surface roughness (SR) value in EDM of Al-SiC MMCs with 20 and 25 vol.% SiC. Irrespective of the electrode material, polarity of the electrode and volume percentage of SiC, the MRR increased with increase in discharge current and for a specific current it decreased with increase in pulse duration. Increase in the volume percentage of SiC had an inverse effect on MRR, and positive effect on TWR and surface finish. Increasing the speed of the rotating electrode resulted in a positive effect with MRR, TWR and better SR than at stationary. Optimum parameters for EDM drilling were also developed to summarize the effect of machining characteristics such as MRR, TWR and SR.
In the present study an analysis has been done to evaluate the electrode wear along the cross-section of an electrode compared
to the same along its length during EDM of aluminum and mild steel using copper and brass electrodes. In an overall performance
comparison of copper and brass electrodes, we found that electrode wear increases with an increase in both current and voltage,
but wear along the cross-section of the electrode is more compared to the same along its length. This is due to easier heat
transfer along the length compared to the same along the cross-section of the electrode. It was also found that the wear ratio
increases with an increase in current. That means, though a higher current causes more removal of work material and the electrode,
comparatively more material is removed from the electrode. The highest wear ratio was found during machining of steel using
a brass electrode. The low thermal conductivity of brass electrodes causes less heat loss, and its low melting point results
in fast melting of the electrode material. At the same time, low thermal conductivity of steel results in poor heat absorption,
and its high melting temperature causes poor removal of work material. These factors result in the highest wear ratio during
machining of steel using a brass electrode. The highest material removal rate was observed during machining of aluminum using
brass electrodes. Comparatively low thermal conductivity of brass as an electrode material does not allow the absorption of
much heat energy, and most of the heat is utilized in the removal of material from aluminum workpiece at a low melting point.
But during machining of steel using copper electrodes, a comparatively smaller quantity of heat is absorbed by the work material
due to its low thermal conductivity. As a result material removal rate becomes very low.
In this paper, parameter optimization of the electrical discharge machining process to Ti–6Al–4V alloy considering multiple
performance characteristics using the Taguchi method and grey relational analysis is reported. Performance characteristics
including the electrode wear ratio, material removal rate and surface roughness are chosen to evaluate the machining effects.
The process parameters selected in this study are discharge current, open voltage, pulse duration and duty factor. Experiments
based on the appropriate orthogonal array are conducted first. The normalised experimental results of the performance characteristics
are then introduced to calculate the coefficient and grades according to grey relational analysis. The optimised process parameters
simultaneously leading to a lower electrode wear ratio, higher material removal rate and better surface roughness are then
verified through a confirmation experiment. The validation experiments show an improved electrode wear ratio of 15%, material
removal rate of 12% and surface roughness of 19% when the Taguchi method and grey relational analysis are used.
KeywordsEDM-Ti–6Al–4V alloy-Taguchi method-Grey relational analysis
Electrical discharge machining (EDM) is widely used in the production of dies. This paper describes an investigation into the optimisation of the process which uses the effect of carbon which has migrated from the dielectric to tungsten–copper electrodes. This work has led to the development of a two-stage EDM machining process where different EDM settings are used for the two stages of the process giving a significantly improved material removal rate for a given tool wear ratio.
The micro-EDM process is one of the basic technologies capable of producing miniature, complex and three-dimensional features down to five micrometres size. As of today, the efforts of modelling the micro-EDM process are extremely limited, although its applications have been identified. As micro-EDM is a variant of the EDM process, and both are spark erosion processes in principle, an understanding of EDM process modelling is essential for the future modelling of the micro-EDM process. This paper presents an extensive review of modelling efforts in the field of EDM processes and proposes directions for the modelling of the micro-EDM process.
An article published in this journal by Sahin and Motorcu[1] developed a surface roughness model based on the response surface method, multiplicative-logarithmically linearized approach for determination of the cutting parameters in turning of AISI 1040 carbon steel. Their published results for the surface roughness show that it appears Sahin and Motorcu[1] have obtained wrong constants (C, m, n, p), thereby resulting in incorrect solutions for the surface roughness prediction model. This note works through the solutions to show how Sahin and Motorcu[1] incorrectly handled the published prediction model constants to their solution. The established predictive model shows that the surface roughness increases with the increase of feed rate but decreases with cutting speed and depth of cut.
Investigations of EDM operations by means of thermo mathematical models
- R Snoyes
- F Van Dijck