Synopsis.docx

R V COLLEGE OF ENGINEERING Bengaluru - 560059 Autonomous Institution Affiliated to Visvesvaraya Technological University, Belagavi

Synopsis for Project

Investigations on the effect of titanium coated tungsten carbide drill bit in electrochemical discharge machining of glass Submitted by

Under the

A SAI SRINIVAS

1RV17MPD09

of Jinka Ranganayakulu Assistant Professor Department of Mechanical Engineering R.V College of Engineering Bengaluru 560059

In partial fulfilment for the award of degree of Master of Technology in Product Design and Manufacturing Mechanical Engineering 2018-19

Guidance

Synopsis Title of the Project Investigations on the effect of titanium coated tungsten carbide drill bit in electrochemical discharge machining of glass

Introduction Hard brittle materials such as glasses, engineering ceramics, and single crystals have favorable characteristics – wear resistance, chemical resistance, a high melting point, and high strength. Such materials are used in many industrial applications. Nevertheless, these excellent materials are generally expensive. Also, most non-conventional machining processes, such as electrochemical machining (ECM), electro discharge machining (EDM), etc., cannot be utilized for the machining of electrically non-conducting materials. Electrochemical discharge machining (ECDM) is such a process, that can be employed to machine electrically nonconducting materials using the electrochemical discharge phenomenon. When two electrodes of very different sizes are separated by a few millimeters and dipped into an electrolyte solution, beyond a certain value of applied voltage, electric sparks appear across the electrode– electrolyte interface on the smaller electrode and the cell current drops. This is known as the electrochemical discharge (ECD) phenomenon. If the machining utilizes the ECD phenomenon, then it is called ECDM. It is a hybrid technique, the combination of ECM and EDM processes

Preliminary Literature Review Weidong Tang et al. [1] has found that the side-insulated tool electrode achieves a smaller hole diameter and better surface integrity without an obvious heat affected zone at the hole entrance. Also, side-insulated electrode has an advantage in enhancing shape accuracy by reducing the taper angle of the micro hole. When the machining depth is 600 μm, the side-insulated electrode achieves a much smaller hole taper angle (3.3°) than the traditional tool electrode does (6.4°). Cheng-Kuang Yang et al. [2] studied the wettability and machining characteristics of different tool electrode materials and their impact on gas film formation. Their machining performance and extent of wear under gravity-feed micro-hole drilling are also examined. Tungsten carbide showed the best machining stability and least tool wear followed by tungsten and stainless steel and the break down voltage was found between 26-30V during ECDM process. Differences in tool material also results in variations in machining speed. Significant tool wear is observed after repeated gravity-feed machining of 50 micro-holes. Lijo Paul and Donald Antony [3] has found that smaller diameter tools has shown higher MRR with lower ROC. S. Saranya et al. [4] have compared a spherical tool tip and cylindrical tool tip their

investigations show that a tool with a spherical tip provides a profile with a reduced entrance diameter and the overcut can be considerably reduced by controlling the tool feed-rate.

Chak and Rao [5] have carried out experimental study with spring fed cylindrical tools under gravity feed mechanism with mixed electrolyte. They have reported that abrasive rotary tool increased the machinability and MRR due to abrasive particles present in machining. Yang et al. [6] also studied the tool geometry effect with a spherical end tool electrode (diameter 150 μm) and cylindrical tool electrode (diameter 100 μm). Experimental results showed that the curve surface on the spherical tool electrode reduced the contact area between the electrode and the workpiece, thus facilitating the flow of electrolyte to the electrode end. This enabled rapid formation of gas film, resulting in efficient micro-hole drilling. Comparison between machining depth of 500 μm achieved by conventional cylindrical tool and spherical tool electrode are carried out. The results showed that machining time was reduced by 83%. Xuan Doan Cao et al. [7] has shown that the grinding process under PCD tools reduces the surface roughness of ECDM structures from a few tens of a μm to 0.05 μm Ra, and the total machining time of the hybrid process is less than a third compared to that under a conventional grinding process. Chak and Rao [8] have also carried out ECDM machining with mixed electrolyte of NAOH and KOH on aluminum oxide workpiece material. It was found that the conductivity of the electrolyte was higher with mixed electrolyte. This provided higher heating in machining area. But beyond the saturation limit conductivity was found to same with higher concentration. In the present paper machining is carried out on silicon wafers with mixed electrolyte of NaOH and KOH with varying electrolyte concentration from 5% to 15 % wt. fraction in order to improve the material removal rate in the process. Rajendra Kumar Arya et al. [9] has developed a fresh electrolyte injection method through a tubular electrode with precisely controlled electrolyte flow rate (EFR) into the machining zone during ECDM. His investigation reveals that the injected fresh electrolyte enhances the machining performance over conventional ECDM process. Also, the EFR is found to be dependent on provided thermal energy inside the machining zone. Tarlochan Singh et al. [10] has developed an ECDM with the pressurized feeding system was successfully used for the fabrication of micro-holes on borosilicate glass up to 1537 μm depth. The developed pressurized feeding system presents 207.4% improvement in machining depth. Ashwin Varghese, Lijo Paul [11] investigated on Polypropylene (PP) materials with graphite particle powder mixed electrolyte in ECDM Process in order to improve the machining. It is found that multiple discharging effects were created on the work piece surface due to conducting graphite particles in electrolyte. Yi Xu et al. [12] experiments demonstrated that Counter resistance method has better repeatability over conventional gravity-feed method. He also found that proper control of varied forces exerted on tool electrode can enhance the micromachining performance. He also observed that accumulation of bubbles near the hole entrance slowed electrolyte replenishment, which is the main reason accounting for the tool bending. Wuthrich et al. [13] investigated on, various tool feeding mechanism, voltage, tool shape and force affecting the machining process. They have conducted consecutive machining at constant voltage and constant tool diameter. They found that the process becomes similar, approaching a repeatable situation because of steady-state distribution of the local temperature.

M L Harugade et al. [14] has studied the effect of different electrolyte solutions like H2SO4, KOH, NaCl, NaOH and found that the acidic electrolyte solution (H2SO4) shows intermittent and disturbed spark which result in excessive erosion of electrode and damage to the workpiece. The salty electrolyte solution (NaCl) shows remarkable wear of tool however no damage to work-piece is recorded. The basic electrolyte solution (NaOH, KOH) shows negligible wear, constant spark and better surface finish of work-piece. Yang et al. [15] investigated the effect of various electrolytes on the time of micromachining of borosilicate experimentally. Their results showed that machining time in Hydroxide salts (NaOH and KOH) is less compared to Chloride salts (NaCl and KCl). Baoyang Jiang et al. [16] A FEA model was deployed in ABAQUS to simulate material removal process in ECDM. In which material removal is treated as a heat transfer problem with assumptions (1) material is removed by thermal melting (2) sparks bring inlet heat to the workpiece. Material is considered to be removed once temperature reaches the melting point of glass. Mudimallana Goud and Apurbba Kumar Sharma [17] has developed a 3D FEM simulation model to study the variation of temperature distribution in the workpiece and the variation of MRR with respect to change in the input parameters like applied voltage and electrolyte concentration. The simulation was carried out for two different materials—soda lime glass and alumina (Al2O3). Jalali et al. [18] developed a thermal analytical model to better understand the material removal mechanism in gravity feed micro-hole ECDM drilling. They considered a hybrid mechanism combining local heating and chemical etching for ECDM machining and compared it with experimental data. Their study was focused on the hydrodynamic regime of ECDM drilling. The estimation of the machining temperature was around 600°C as a result of the comparison between model and experiment. Ranganayakulu et al. [19] experimental results show that the material removal mechanism in ECDM is non-linear – the volume of material removed decreases with increasing machining depth. A soft computing approach called adaptive neuro fuzzy inference system (ANFIS) is adapted to model the non-linear material removal rate. He also found that voltage had predominant effect on MRR than electrolyte concentration and tool feed rate. Lijo and Somashekhar [20] had conducted Response Surface Modeling (RSM) of ECDM process with pulsating DC to understand the effect of various process parameters on micro hole and micro channel machining to study the output response Material Removal Rate (MRR), Tool Wear Rate (TWR), Heat Affected Zone (HAZ) and Radius of Over Cut (ROC). They found that that the temperature of the electrolyte affects the machining process. MRR decreases at higher depth due to lower spark energy which was due to unavailability of electrolyte. Lijo and Somashekhar [21] have also carried out multi objective optimization with grey relational analysis. They have made micro channels with optimized values. Reported that heat affected zone in micro channels can be reduced with low duty factor during machining process. Lijo et al. [22] also reported that higher frequency at low duty factor will increase MRR with reduction in HAZ. Duty factor is found to be a predominant factor affecting the machining characteristics.

Jain et al. [23] predicted the material removal rate in the ECDM drilling by modelling the problem as a 3D unsteady state heat conduction problem. They adopted the heat source of the spark as a prismatic column with squared cross section. They solved the mentioned problem with the finite element method to compute the temperature distribution and the material which attains equal 3 to or above the melting/softening temperature of the soda lime glass workpiece (Tm/s=850°C) that is assumed to be removed. In the best situation (machining voltage 65V), the compatibility of the model with the experimental data was about 35%. The assumed shape for the heat source could be one of the error sources of the model because this shape is far from a real-life situation. Phipon and Pradhan [24] used Genetic Algorithm (GA) using MATLAB software to optimize process parameters to minimize ROC and HAZ on silicon nitride ceramics in ECDM process. It was also observed from GA analysis that, higher voltage results in larger ROC and medium electrolyte concentration provide a low ROC. Hajian et al. [25] investigated the effect of the magnetic field on the surface quality and the depth of microchannels produced by ECDM milling. According to their results, in lower electrolyte concentration, the magnetic field increases the bubble motion and enhances the conductivity of electrolyte. Hajian et al. [26] has observed a decrease in the bending force by increasing the electrolyte concentration and elevating the applied voltage. In addition, the significant effect of a magnetic field on the reduction of bending force in the lower concentration of electrolyte (15 wt.%) was observed.

Problem Statement From the literature it was found that minimum amount of research was carried out with coated twist drill tool bit. Hence present work is mainly focusing on, to investigate the influence of titanium coated tungsten carbide twist drill bit on machining performance in terms of material removal rate, tool wear rate, heat affected zone and over cut in machining of borosilicate glass.

Objective of the Project   

To investigate the influence of coated tools on machining performance and compare with the non-coated tools. To optimize processes parameters like voltage, electrolyte concentration, duty factor and tool rotation. To develop and simulate a model for tool wear rate.

Methodology Literature Review

Choosing Parameters and their Levels

Experimental Layout

Performing Experiments

Analysis of Results

Tool Wear Simulation

Comparison of Results with Simulation

Conclusion

1. Choosing parameters from speed, feed, voltage, current, duty factor, tool diameter (Since it is not easy to study many parameters at once few parameters will be chosen for study rest of the parameters will remain constant for all experiments) 2. Finding out number of levels for each parameter 3. Using design of experiments to generate experimental layout 4. Performing the experiments 5. Measure the response parameters and compare effects with respect to coated and uncoated tool (response parameters are radial overcut (ROC), material removal rate (MRR), tool wear rate (TWR), HAZ thickness 6. Using Minitab to perform ANOVA to find significance of various parameters 7. Tool wear simulation and comparison with the experiments conducted Materials, Tools & Equipment 1. ECDM machine 2. Tungsten carbide tool 3. Workpiece Software Requirements 1. Minitab 17 2. MATLAB 3. Autodesk Inventor 2019 4. Autodesk NASTRAN In-CAD

Timeline

References [1] Weidong Tang, Xiaoming Kang and Wansheng Zhao, Enhancement of electrochemical discharge machining accuracy and surface integrity using side-insulated tool electrode with diamond coating, IOP Publishing, J. Micromech. Microeng. 27 (2017) 065013 (11pp) [2] Yang CK. (2010). Effect of surface roughness of tool electrode materials in ECDM performance. International Journal of Machine Tools & Manufacture 50: pp. 1088–1096. https://doi.org/10.1016/j.ijmachtools.2010.08.006 [3] Lijo Paul and Donald Antony, Effect of tool diameter in ECDM process with powder mixed Electrolyte, IOP Conf. Series: Materials Science and Engineering 396 (2018) 012070 doi:10.1088/1757-899X/396/1/012070 [4] S. Saranya, A. Ravi Sankar, Effect of Tool Shape and Tool Feed Rate on the Machined Profile of a Quartz Substrate Using an Electrochemical Discharge Machining Process, Proceedings of the 2015 2nd International Symposium on Physics and Technology of Sensors, 8-10th March, 2015, Pune, India [5] Chak S K, Rao P V. Trepanning of Al2O3 by electro-chemical discharge machining (ECDM) process using abrasive electrode with pulsed DC supply. International Journal of Machine Tools and Manufacturing 2007; pp. 2061-2070. [6] Yang, C., Ho, S., Yan, B.H., 2001. Micro hole machining of borosilicate glass through electrochemical discharge machining (ECDM), Key Engineering Materials. Trans Tech Publications pp. 149-166. [7] Xuan Doan CaoBo, Hyun KimBo Hyun Kim, Chong Nam Chu, Hybrid Micromachining of Glass Using ECDM and Micro Grinding, January 2012, International Journal of Precision Engineering and Manufacturing, DOI: 10.1007/s12541-013-0001-6 [8] Chak S K, Rao P V. The drilling of Al2O3 using a pulsed DC supply with a rotary abrasive electrode by the electrochemical discharge process. International Journal of Advanced Manufacturing Technology 2008; 39, pp. 633-641. [9] Rajendra Kumar Arya, Akshay Dvivedi, Journal of Materials Processing Technology https://doi.org/10.1016/j.jmatprotec.2018.10.035 [10] Tarlochan Singh & Akshay Dvivedi (2018) On pressurized feeding approach for effective control on working gap in ECDM, Materials and Manufacturing Processes, 33:4, pp. 462473, DOI: 10.1080/10426914.2017.1339319 [11] Ashwin Varghese, Lijo Paul, Effect of Powder Mixed Electrolyte in ECDM Process, Materials Today: Proceedings Volume 5, Issue 5, Part 2, 2018, Pages 11864-11869 [12] Yi Xu, Jihong Chen, Baoyang Jiang, Jun Ni, Journal of Materials Processing Technology 2018, https://doi.org/10.1016/j.jmatprotec.2018.02.023 [13] Wüthrich R, Spaelter U, Wu Y and Bleuler H. A Systematic Characterization Method for Gravity Feed Micro Hole Drilling in Glass with Spark Assisted Chemical Engraving (SACE). J of Micromechanics and Microengineering 2006; 16: pp. 1891-1896.

[14] M.L.Harugade, M.V.K., N.V.Harude, Effect of electrolyte solution on material removal rate in Electro Chemical Discharge Machining. Journal of Mechanical and Civil Engineering: pp. 1-8. [15] Cheng C-P, K-L W, Mai C-C, Yang C-K, Hsu Y-S, Yan B-H (2010) Study of gas film quality in electrochemical discharge machining. Int J Mach Tools Manuf 50(8): pp. 689–697 [16] Baoyang Jiang, Shuhuai Lan, and Jun Ni, Investigation of micro-drilling assisted electrochemical discharge machining, IWMF2014, 9th International Workshop on Micro factories October 5-8, 2014, Honolulu, U.S.A, pp. 1-8 [17] Mudimallana Goud and Apurbba Kumar Sharma, A three-dimensional finite element simulation approach to analyse material removal in electrochemical discharge machining, Proceedings of the Institution of Mechanical Engineers Part C Journal of Mechanical Engineering Science 1989-1996 (vols 203-210) March 2016 [18] Jalali M, Maillard P, Wüthrich R. Toward a better understanding of glass gravity-feed micro-hole drilling with electrochemical discharges. Journal of Micromechanics and Microengineering. 2009, pp. 19:045. [20] Lijo P, Somashekhar S H. Response Surface Modelling of Micro Holes in Electrochemical Discharge Machining Process, Procedia Engineering 2013; Vol. 64, p.1395 –1404. [21] Lijo P, Somashekhar S H. Characterization of Micro Channels in Electrochemical Discharge Machining Process, Applied Mechanics and Materials 2014, pp. 490-491. [22] Lijo P, Somashekhar S H. Evaluation of Process Parameters of ECDM using Grey Relational Analysis. Procedia Materials Science 2014, pp. 2273-2282. [23] Jain V, Dixit P, Pandey P, On the analysis of the electrochemical spark machining process. International Journal of Machine Tools and Manufacture. 1999, pp. 65-86. [24] Ruben Phipon and Pradhan B B. Optimization of electro-chemical discharge machining process using genetic algorithm. IOSR J of Engineering 2012, pp. 106-115. [25] Hajian, M., Razfar, M.R., Movahed, S., 2016. An experimental study on the effect of magnetic field orientations and electrolyte concentrations on ECDM milling performance of glass. Precision Engineering 45, pp. 322-331 [26] Hajian, M., Razfar, M.R. & Etefagh, A.H. Experimental study of tool bending force and feed rate in ECDM milling, The International Journal of Advanced Manufacturing Technology (2017), 91, pp. 1671-1677. https://doi.org/10.1007/s00170-016-9860-1