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Journal ArticleDOI

Effect of micro double helical grooved tools on performance of electric discharge drilling of Ti-6Al-4V:

20 Feb 2021-Vol. 235, Iss: 11, pp 1832-1847

Abstract: Machining of complex features and holes on superalloys is a topic of both industrial and academic interest. Though the demand for high aspect ratio holes on Ti-6Al-4V is high in aerospace, biomedic...
Topics: Machining (57%), Electric discharge (52%)
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Journal ArticleDOI
Vinod Yadav1, Vijay Kumar Jain1, P.M. Dixit1Institutions (1)
Abstract: The high temperature gradients generated at the gap during electrical discharge machining (EDM) result in large localized thermal stresses in a small heat-affected zone. These thermal stresses can lead to micro-cracks, decrease in strength and fatigue life and possibly catastrophic failure. A finite element model has been developed to estimate the temperature field and thermal stresses due to Gaussian distributed heat flux of a spark during EDM. First, the developed code calculates the temperature in the workpiece and then the thermal stress field is estimated using this temperature field. The effects of various process variables (current and duty cycle) on temperature distribution and thermal stress distribution have been reported. The results of the analysis show high temperature gradient zones and the regions of large stresses where, sometimes, they exceed the material yield strength.

215 citations


"Effect of micro double helical groo..." refers methods in this paper

  • ...The high density thermal electric discharges in EDM cause the formation of recast layers and these thermal stress fields can also be predicted by making use of FEM models.(4) Studies are also driven in the direction of investigation of the relationship between accuracy and...

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Journal ArticleDOI
Shrikrishna N. Joshi1, S. S. Pande2Institutions (2)
01 Mar 2011
TL;DR: The proposed integrated (FEM-ANN-GA) approach was found efficient and robust as the suggested optimum process parameters were found to give the expected optimum performance of the EDM process.
Abstract: This paper reports an intelligent approach for process modeling and optimization of electric discharge machining (EDM). Physics based process modeling using finite element method (FEM) has been integrated with the soft computing techniques like artificial neural networks (ANN) and genetic algorithm (GA) to improve prediction accuracy of the model with less dependency on the experimental data. A two-dimensional axi-symmetric numerical (FEM) model of single spark EDM process has been developed based on more realistic assumptions such as Gaussian distribution of heat flux, time and energy dependent spark radius, etc. to predict the shape of crater, material removal rate (MRR) and tool wear rate (TWR). The model is validated using the reported analytical and experimental results. A comprehensive ANN based process model is proposed to establish relation between input process conditions (current, discharge voltage, duty cycle and discharge duration) and the process responses (crater size, MRR and TWR) .The ANN model was trained, tested and tuned by using the data generated from the numerical (FEM) model. It was found to accurately predict EDM process responses for chosen process conditions. The developed ANN process model was used in conjunction with the evolutionary non-dominated sorting genetic algorithm II (NSGA-II) to select optimal process parameters for roughing and finishing operations of EDM. Experimental studies were carried out to verify the process performance for the optimum machining conditions suggested by our approach. The proposed integrated (FEM-ANN-GA) approach was found efficient and robust as the suggested optimum process parameters were found to give the expected optimum performance of the EDM process.

110 citations


"Effect of micro double helical groo..." refers methods in this paper

  • ...An intelligent and integrated Finite Element Method – Artificial Neural Network – Genetic Algorithm (FEM-ANN-GA) approach to optimize the die-sinking EDM process was developed with a mean prediction error of 7%.(3) The high density thermal electric discharges in EDM cause the formation of recast layers and these thermal stress fields can also be predicted by making use of FEM models....

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Journal ArticleDOI
Abstract: In this study, the feasibility of fabricating micro-holes in the high nickel alloy using micro-electro-discharge machining (micro-EDM) was investigated. The high nickel alloy is a material with high magnetic permeability. It can be used to shield MEMS prevent interference of the magnetic field. Micro-systems can be assembled and micro-wires can be connected through micro-holes that are drilled in the workpiece. In this way, the internal electronic system can communicate with external system without magnetic wave disturbance. However, since the high nickel alloy is tough and can easily cause cutting tool wear, it is difficult to fabricate micro-holes by the conventional machining methods. In this work, a two-stage cylindrical cutting tool of high hardness was first fashioned. The tool was precisely shaped with a first stage (i.e., tip) having a smaller diameter, and a helically grooved second stage with a larger diameter by the wire electro-discharge grinding (WEDG) process. The first stage of the tool electrode was then used to drill a micro-hole in a plate using micro-EDM process. To improve the roughness of micro-holes, the second stage with helical groove was used for in situ grind machining with SiC particles. Our experimental results show that by optimizing EDM machining parameters, i.e., discharge current of 500 mA, pulse duration of around 4 μs, etc., favorable diameter variation between the entrances and the exits (DVEE), good material removal rate (MRR) and good electrode wear rate (EWR) could be obtained. The addition of the in situ grind machining leads to precise contours, and the surface roughness of micro-holes is reduced to 0.85 μm Rmax, as revealed by SEM photographs.

109 citations


"Effect of micro double helical groo..." refers methods or result in this paper

  • ...This is in agreement with the findings of Liu et al.18 wherein a helical grooved electrode with added Silicon Carbide particles is used to obtain an improved surface finish....

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  • ...In EDM though the heat affected zone is less the formation of the recast layer is one of the major drawbacks as it leads to poor surface quality and microcracks.(18) To calculate the area of the spread of the recast layer, the SEM image of the hole was imported into ImageJ software and pixel to mm conversion was done by setting the scale....

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  • ...This is in alignment with basic principles seen in most of the literature in this field and particularly with the observations of Liu et al.18 where it is reported that the use of a helical tool for grinding a machined hole leads to good surface finish....

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  • ...This is in agreement with the findings of Liu et al.(18) wherein a helical grooved electrode with added Silicon Carbide particles is used to obtain an improved surface finish....

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  • ...This is in alignment with basic principles seen in most of the literature in this field and particularly with the observations of Liu et al.(18) where it is reported that the use of a helical tool for grinding a machined hole leads to good surface finish....

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Journal ArticleDOI
Jung Chou Hung1, Jui Kuan Lin2, Biing Hwa Yan1, Hung Sung Liu1  +1 moreInstitutions (2)
Abstract: This paper presents a novel process using micro-electro-discharge- machining (micro-EDM) combined with ultrasonic vibration by a helical micro-tool electrode to drill and finish micro-holes. During the machining processes, a micro-tool is directly fabricated by wire electro-discharge grinding (WEDG) using micro-EDM combined with various methods for machining the micro-hole and by ultrasonic vibration to finish the hole wall. In this work, circular micro-holes are machined in a high nickel alloy by cylindrical and helical electrodes. Using a helical micro-tool electrode for micro-EDM combined with ultrasonic vibration (HE-MEDM-UV) can substantially reduce the EDM gap, taper and machining time for deep micro-hole drilling. In addition, using a helical micro-tool with micro ultrasonic vibration finishing (HE-MUVF), good surface quality and less taper of the hole wall can be obtained by applying a suitable electrode step variation, rotational speed and ultrasonic amplitude with a machining time of approximately 25 min. According to scanning electron microscopy (SEM) micrographs and atomic force microscopy (AFM) measurement, HE-MUVF can indeed improve the surface roughness from 1.345 µm Rmax before finishing to 0.58 µm Rmax after HE-MUVF. This result demonstrates that using HE-MEDM-UV combined with MUVF can yield micro-holes of precise shape and smooth surface.

78 citations


"Effect of micro double helical groo..." refers methods in this paper

  • ...This concept was also observed by Hung et al.(13) while performing step turning, the machining time was substantially reduced by using a single helical electrode....

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  • ...Making use of a helical tool for micro-EDM combined with ultrasonic vibration can substantially reduce the EDM gap, variation between the entrance and exit of the hole and the machining time.(13) A novel process for fabrication of micro end mills with low-speed Wire Electric Discharge Machining (WEDM) has been developed and its feasibility for producing micro milling tools with multiple helical cutting edges has been demonstrated....

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  • ...This concept was also observed by Hung et al.13 while performing step turning, the machining time was substantially reduced by using a single helical electrode....

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Journal ArticleDOI
Lei Li1, Lin Gu1, Xue-Cheng Xi1, Wansheng Zhao1Institutions (1)
Abstract: The existing applications of electrical discharge machining (EDM) for bulk material removal are restricted by their comparatively low material removal rates. The bunched-electrode EDM proposed in this study, using the powerful multi-hole inner flushing, is an effective way of being released from this restriction. This paper investigates the mechanism by which flushing (flushing modes and flushing parameters) influences machining performance indices, i.e., material removal rate and tool wear rate, using experiments and simulations. Based on an investigation conducted, compared with traditional solid electrode with mono-hole inner flushing, a bunched electrode with multi-hole inner flushing endures higher peak current and results in larger material removal rate and higher relative tool wear ratio because of a more effective flushing process. By properly choosing inlet velocity and electrode effective-area ratio, a higher material removal rate is achieved and relative tool wear ratio is kept at a lower level.

73 citations


"Effect of micro double helical groo..." refers methods in this paper

  • ...Another comparative CFD analysis shows that the velocity increases drastically in the radial direction with a high peripheral debris concentration of 611 particles/m(2) for a mono holed electrode but for bunched electrodes the velocity field is smooth with a lower debris concentration of three particles/m(2).(16) In this work, the process of EDD is selected as it is one of the most economic and feasible ways to machine holes on superalloys and the same being an unconventional machining process produces only insignificant machining forces....

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