Die-sinking EDM Research Articles

A Comparative Study of Machining Parameters on Die-Sinking Electrical Discharge Machining (EDM) using Copper and Aluminium Electrodes on Hard Steels

This paper considers effect of variation in value of Discharge current on different process parameters of Die Sinking EDM. The parameters considered were Material removal rate (MRR), Tool removal rate (TRR), Surface roughness (Ra) and Time (for machining required depth of cut). A total of 32 experiments were conducted on four different hard steels i.e. Die steel D3, En-8, En-19 and Stainless steel (SS-AISI-440C). The Copper and Aluminium electrodes brazed with mild steel were used for machining. The four different values of current i.e. 6A, 9A, 12A and 15A were considered for the study. The experimental results shows the relationship between MRR, TRR, Ra and Time with variation in magnitude of discharge current. This study also illustrates the relationship among different process parameter considered in the study. The results are shown with the help of graphs and tables.

Parametric Analysis of Different Grades of Steel Materials Used in Plastic Industries through Die Sinking EDM Process

In the present research work four different work materials viz. EN24, D2, H13, P20 which are commonly use in plastic industries are considered for machining applying EDM process. Four different control parameters such as pulse on time, pulse off time, gap current, and Spark gap are considered to study the effect on the performance of responses like material removal rate, surface roughness and overcut using a square shape copper tool with lateral flushing. A well design experimental plan is used to reduce the total number of experiment following L9 orthogonal array. Based on Taguchi methodology the significant process parameters affecting the responses are identified applying ANOVA for each material. The effect of the responses with respect to the four control parameters for the four different work materials is compared through linear graphs. A well-known Grey relational analysis is carried out where the weights are calculated using entropy method to full fill the multi criteria decision making process.

Performance and Limitations of the Conventional Electrode Materials for Erosion of High Aspect Ratio Microcavities

The low electrode wear strategy based on a carbonaceous layer formation on electrodes considerably increases resource efficiency in the conventional die-sinking EDM. However, the smallest electrode projection area Ap for using the strategy is limited to 0.1 mm2 and maximum pulse current 3A, possibly due to the pulse re-opening phenomenon. In this work, using a novel generator circuit, pulse re-openings have been restricted up to pulse durations 100μs and a current of 1A. Hence, the performance of conventional electrode materials is evaluated in order to push the limits of the low wear strategy. However, when using graphite and copper infiltrated graphite microelectrodes, bending of the electrodes is observed, especially in the tip region. The simulation of temperature in the microelectrodes suggests abnormal carbonaceous build up process. This explanation is also concurrent to the observation of a process instability resulting in irreproducible electrode wear behaviour. For copper microelectrodes, another phenomenon is observed where overcuts are produced in the eroded cavities. These overcuts are produced by sparks with high discharge voltage. Sliding of the plasma channel from the electrode corners to the side surfaces is proposed to cause such discharges and overcuts. Thus, underlying mechanisms limiting the low wear strategy in micro-EDM are identified.

Electrical Discharge Machining for Complex Cavity with a Porous Electrode

In die-sinking EDM processing of deep complex cavities, gap status is easy to be deteriorated because of the hardness of debris evacuation. To address this problem, a kind of porous material was applied as the tool electrode. The porous material was prepared by the way of high-temperature sintering of copper particles. With a proper sintering parameters setting, a porous electrode, in which copper particles connect with each other tightly, is able to be fabricated according to a graphite mould. The porous electrode also has a high porosity such that liquid flow channels are formed and the distributed multi-hole inner-flushing can be achieved. A complex porous electrode for the machining of a deep, complex, and semi-enclosed cavity was prepared, and the EDM experiment was carried out. The experimental results showed that the roughing machining efficiency was raised significantly, which therefore revealed a strong capability of porous electrode in complex cavity machining.

Parametric optimisation of electrical discharge machining process: a numerical approach

In this work, a thermal model based on finite element method has been proposed to predict the material removal and tool wear in electrical discharge machining process by simulating a single spark discharge. The model is validated by conducting experiments on a die-sinking EDM machine. It is found that numerical model provides reasonably accurate estimation of responses. Parametric analysis is conducted on the proposed model to study the influence of significant process parameters on the responses. Regression analysis is carried out to develop empirical models relating responses with process parameters. Finally, a non-dominated sorting genetic algorithm has been employed to obtain Pareto optimal solution for multi-objective optimisation. The numerical method provides an inexpensive and time saving alternative to study the performance of machining before actual cutting operation.

INVESTIGATION AND OPTIMIZATION OF EDM PERFORMANCE MEASURES USING EMPIRICAL DATA ANALYSIS

In this paper research is aimed to investigate and optimization of EDM performance measures in order to find out best ideal EDM electrode having higher material removal rate, improved surface finish and lower electrode wear rate. For this four EDM electrodes of four different materials (viz. Gr, Cu, Br and Al) are developed by three different manufacturing methodologies. Electrode design is very time consuming process and done interactively using CAD system. In this research work Vertical Milling Machine, Net Shape Casting and Die Sinking EDM do EDM electrodes fabrication. After the electrode Fabrication testing of electrodes is done on Die Sinking EDM. For optimization two different advanced methods of optimization SAW & TOPSIS are used for analysis of EDM performance measures and to predict optimal choice of each EDM electrode. The analysis of both optimization methods reveals Copper is best EDM electrode followed by Brass, Aluminium and Graphite. Experimental results are provided to verify this approach.

A strategy for low electrode wear in meso–micro-EDM

Implementation of die-sinking EDM for precision machining of meso–micro-scale features with surface area smaller than 10mm2 down to 0.1mm2 is mainly restricted by electrode machining and electrode wear. In this work, micro-scale graphite electrodes with a projection area as small as 0.002mm2 and 1mm length have been machined. Process parameter analysis is carried out to analyse the wear behaviour of micro-scale graphite electrodes during erosion. Pulse duration, pause duration and rising current slopes have been found to be the primary parameters affecting the electrode wear. A low electrode wear strategy consisting of the wear neutral pulse packets is developed for erosion of micro-scale cavities and slots using graphite electrodes. Resource efficiency achieved through low electrode wear during roughing enables die-sinking EDM as a potential economic and energy efficient micromachining process.

ジャンプ動作制御による形彫放電加工の安定化

ジャンプ動作制御による形彫放電加工の安定化

Study on Processing of Titanium Aluminide Alloy Using Electrical Discharge Machining

Currently there is a continuous extension of application areas of titanium aluminides but their processing encounters a number of difficulties such as the precision of machining and modifying the properties of the surface layer. In the specialist literature [1, 2, 4, 7] different authors address the processing of these materials by conventional methods. In this context, this paper aims at finding the optimal regimes for the electrical discharge machining (EDM) of titanium aluminides Ti-40Al-5NB-3V and provides the analysis of the process parameters effect on cutting through wire EDM technological characteristics. In the case of wire EDM a relatively good output has been obtained as well as very good roughness of the processed surfaces. On the contrary, when considering the die sinking edm, due to very small output, several experimental measurements were performed on three machines – Sodick, ONA and ELER. Based on the experimental data, it has been established that the best output is to be obtained by reverse polarity machining.

Material Removal Rate, Electrode Wear Rate, and Surface Roughness Evaluation in Die Sinking EDM with Hollow Tool through Response Surface Methodology

Electrical discharge machining is one of the earliest nontraditional machining, extensively used in industry for processing of parts having unusual profiles with reasonable precision. In the present work, an attempt has been made to model material removal rate, electrode wear rate, and surface roughness through response surface methodology in a die sinking EDM process. The optimization was performed in two steps using one factor at a time for preliminary evaluation and a Box-Behnken design involving three variables with three levels for determination of the critical experimental conditions. Pulse on time, pulse off time, and peak current were changed during the tests, while a copper electrode having tubular cross section was employed to machine through holes on EN 353 steel alloy workpiece. The results of analysis of variance indicated that the proposed mathematical models obtained can adequately describe the performances within the limits of factors being studied. The experimental and predicted values were in a good agreement. Surface topography is revealed with the help of scanning electron microscope micrographs.

Wire-EDM Properties of EC-PCD Made up of Boron Doped Diamond Particles

It has been made clear that the EC-PCD composed of boron doped diamond particles improves the performance in the die sinking EDM and wire EDM in comparison with the existing standard PCD (S-PCD). However, the effect of the property improvement could not been evaluated quantitatively in the research reports in the past. Therefore, in this study, wire EDM cutting tests were conducted on the specimens of S-PCD and EC-PCD, in addition to the evaluation of cutting efficiency and cutting PCD surface, a detailed investigation of the cut surface properties of the PCD has been performed under the color 3D laser scanning microscope. In order to investigate effects of a grain size of the source diamond, EDM cutting experiments were conducted on the EC-PCD specimens of 4 different grain sizes. As a result, it was found that the cutting speed was higher in the case of EC-PCD than the case of S-PCD, e.g., by 20% and 40% respectively in the sample of 10μm and 25μm particle size. Also, in the case of the cut S-PCD surface, a groove due to the discharge is formed in the boundary of the tungsten carbide layer and the PCD layer. However, in the case of the cut EC-PCD surface, the groove did not appear in the boundary.

Effect and Optimization of Machine Process Parameters on MRR for EN19 & EN41 Materials Using Taguchi

The present work deals with the comparison of the MRR for EN19 and EN41 material in a die sinking EDM machine. The various input factors like Pulse ON time, Pulse OFF time, Discharge current and voltage were considered as the input processing parameters, while the MRR is considered as the output. Optimization using Taguchi method was performed to predict the best combination of inputs towards maximum output. A comparison was done to obtain the effect of these input parameters over the MRR for both the material, and simultaneously the impact of the carbon percentage over the MRR was investigated. It was found that the Discharge current in case of the EN41 material and EN19 material had a larger impact as compare to other processing parameters on the MRR. A relative study of the carbon composition for both the material was also done.

Dry die-sinking EDM with mouldable graphite–polymer electrode investigation of process parameters and pulse identification methods

In this paper, a new dry die-sinking EDM polishing method using a mouldable polymer composite electrode as tool is presented. This EDM method involves two new concepts, namely: dry die sinking and the polymer composite tool. An experimental investigation was performed on the dry die-sinking EDM process to assess the feasibility of finishing down to 0.2–0.3 μm Sa, and polishing from 0.2 to 0.3 μm Sa down to the finest achievable surface finish. To simplify sample preparation, the methodology involved a reversal of the polishing process. Hence, the surface finish of a 13-mm diameter P20 tool steel disk was taken from a lapped 0.01-μm Sa surface finish up to a rougher steady-state surface finish value, assuming comparable results with conventional rough-to-fine polishing procedures. Several process parameters were evaluated such as: pulse current level I EP, open-circuit voltage V OC, pulse time on T ON, pulse time off T OFF, number of polishing cycles N C and three pulse identification methods, for their effect on sample surface finish micrometre Sa, material removal rate MRR [cubic millimetre per hour] and electrode relative wear rate ERWR.

Die-sink EDM in Meso-Micro Machining

Micro EDM has been identified since more than a decade as suitable process for machining complex shaped structures with high aspect ratio, though only through variations of EDM such as micro EDM milling, micro EDM drilling, coated electrodes etc. In the current paper, we present the research focused on analysing the capability for implementation of die-sink EDM in meso - micro scale machining (structures with surface area smaller than 10mm2 down to 0.05mm2) by concentrating on primary process parameters to obtain high material removal rate, low tool electrode wear with high form accuracy and precision. Graphite electrodes were mill machined in meso-micro scale with high precision and accuracy. Low tool wear technology was developed for using graphite electrodes in meso-micro EDM offering economical and energy efficient solution in meso-micro scale machining.

Performance of Bunched-Electrode in EDM

This paper aims to introduce the performance of bunched-electrode for die-sinking EDM. Bunched-electrode was formed by bunching numerous hollow cell-electrodes together to generate an electrode in which end surface matches the final surface of the mould cavity. FEM analysis and experiments were conducted to demonstrate the feasibility and effectiveness of bunched electrode in ED machining. Experiments show that while machining with bunched-electrode, it is feasible to apply a much higher peak current to achieve higher MRR. Meanwhile, a special phenomenon called shallow radial craters in machining with bunched-electrodes was observed and analyzed. One possible reason may be that the plasma columns in the gap are distorted outwards by strong inner pressure flushing.

Electrode Design for Oscillating EDM

In die-sinking EDM, the electrode is moved only in the Z-axis direction, while in oscillating EDM, electrodes are oscillated in both the X-axis and Y-axis directions to realize high accuracy machining. There are many ways of designing electrodes for oscillating EDM. However, because the form of electrodes and subsequently the oscillating patterns of these electrodes depend on the shapes of the die/mold used, they become complicated when the die/mold shape is complicated, and electrode design takes hours in such cases. This paper therefore proposes a new approach of designing electrodes for oscillating EDM. Some oscillating patterns based on the proposed approach are also analyzed from the viewpoint of usefulness.

Optimization of 6061T6 CNC Boring Process Using the Taguchi Method and Grey Relational Analysis

Optimization of 6061T6 CNC Boring Process Using the Taguchi Method and Grey Relational Analysis

MONITOR AND CONTROL OF DISCHARGE ENERGY DURING EDMING

A pulse energy at 100MHz is verified to be able to determine the normal and abnormal discharge during electrical discharge machining (EDMing). A band pass filter is designed to detect the energy at this frequency, and can verify which discharge pulses are normal and abnormal, respectively. A field programmable gate array (FPGA) is used to implement the discharge detection circuit, including detection of the time of ignition (Td) and discharge high-energy. Function analysis is used to design the proportional (P) Td controller to allow the bounded variation of reference input and the feedback signals. Energy of about 100MHz can be maintained within a specified pulse width by regulating the position of the electrode, including a slight regulation and jump motion. The rate of erosion during the roughing and finishing of a die-sinking EDM is confirmed to demonstrate the improvements obtained by the EDMing.

Die-Sinking EDM Simulation Coupled by Fluid Flow Analysis in Discharge Gap

This paper describes a die-sinking EDM simulation which can simulate the wear of tool electrode with sharp edges and the distribution of debris particles concentration in the machining gap. This simulation is based on the discharge location searching algorithm to reproduce the gap phenomena caused by every pulse discharge. The algorithm is a simple repetition of the routine which is composed of: 1) determining the next discharge location, 2) removing the tool electrode and work piece electrodes, 3) distributing debris particles, and 4) feeding the tool electrode. This algorithm was modified to simulate the removal of surfaces with large inclination, lateral surfaces and edge portions of the tool electrode. Moreover, a method to calculate the debris particles concentration in the gap extended three dimensionally was developed. Thus, the wear of tool electrode with sharp edges was simulated combining the discharge location searching algorithm with the 3D calculation of debris concentration. Simulation results agreed with experimental results especially in the case of using brass as the tool electrode material with which deposition of carbon on the tool electrode is negligibly small.

Modeling and analysis of electrode wear and white layer thickness in die-sinking EDM process through response surface methodology

In this study, an attempt has been made to model electrode wear (EW) and recast layer thickness (WLT) through response surface methodology (RSM) in a die-sinking EDM process. A central composite rotatable design (CCRD) involving three variables with five levels has been employed to establish a mathematical model between input parameters and responses. Pulse on-time, pulse off-time and pulse current were changed during the tests based on the CCRD. The results of analysis of variance (ANOVA) indicated that the proposed mathematical models obtained can adequately describe the performances within the limits of factors being studied. The experimental and predicted values were in a good agreement.