International Journal of Machining and Machinability of Materials (29 papers in press)

Regular Issues

• On the curl and spring behavior of CNC turned beryllium copper chips using computational Image/video analysis  
  by V.S. Sooraj, N. Nidish, A. Nikhil, C. Priyanka 
  Abstract: Characteristic features of spring coiled chips generated during straight turning of Beryllium-Copper alloy have been studied using computational image and video analysis. Geometry and curl-behavior of ductile chips leading to the formation of continuous helical coil structure is investigated theoretically and experimentally. Aiming the predictive generation of such chips for futuristic applications, theoretical relationships are derived to predict the curl radii and helix parameters interms of cutting conditions and tool geometry. Cutting performances are also analyzed at various conditions using the chip compression ratio, incorporating the inter-influence of major and minor cutting edges. A specially designed vibration test of metal chip followed by a computational video analysis is introduced in this work to assess their spring characteristics and stiffness. A simplified spring-beam analogy is applied for modeling the transverse vibration of chips using a clamped-free end condition, frequency of which is analyzed from the videos and correlated to stiffness. Detailed experimental investigation followed by response surface analysis is reported to illustrate the geometrical features of chips at various cutting conditions.
  Keywords: Machining; Beryllium-Copper; Chip; Curl; Spring; Stiffness.
  
  
• An Experimental Investigation of control parameters in 5-axis Hybrid Parallel kinematic Machine in Milling of Aluminium 6061-T3  
  by SURYAM LV, Balakrishna B 
  Abstract: Surface roughness is an important factor in predicting performance of any machining operation. The experiment has been performed in milling a V-shaped pocket on Aluminium 6061-T3 by Exechon parallel kinematic machine using carbide tool. Three different segmented surfaces are selected on V-block and the effect of control parameters were investigated over it. In this research, Taguchi method is used to identify the optimal combination of spindle speed, feed, and depth of cut. To analyze the effect of the control parameters for fine surface finish, Taguchi L9 orthogonal array, signal-to-noise (S/N) ratio and analysis of variance (ANOVA) are employed. Control parameters such as high spindle speed, low feed rate and low depth of cut plays a decisive role in the result of surface roughness. Also, the obtained results from PKM were compared to that of CNC machining, and the surface topologies were examined under optical and scanning electron microscope.
  Keywords: Exechon PKM XT 700S; Surface Roughness; Taguchi Method; s/n ratio; ANOVA.
  
  
• Experimental Investigation on Friction Drilling of Stainless Steel AISI 304  
  by Shayan Dehghan, Mohd Idris Shah Ismail, Mohd Khairol Anuar Mohd Ariffin, B.T. Hang Tuah Baharudin, Amir Parnianifard 
  Abstract: Friction drilling is an unexplored manufacturing process to produce holes in thin-walled sheet metals. In this study, the effects of process parameters in friction drilling of austenite stainless steel investigated experimentally and statistically. It was confirmed, sufficient heat generation, which cause to better bushing shape and height, acceptable drilled-hole diameter and lowest roundness error result from low spindle speed and high feed rate. It was obtained, although effect of feed rate on hole-wall thickness was negligible; spindle speed has significant effect on that which is inverse from spindle speed effect on bushing height. Moreover, micro-hardness reduced gradually away from the drilled-hole edge. Observing on tool shape and wear damage using optical microscope and scanning electron microscope quantifies effects of spindle speed and feed rate on tool performance and tool wear characteristics. Results indicate that better performance of drilling tool obtained from lower spindle speed and high feed rate.
  Keywords: Friction drilling; Difficult-to-machine material; Hardness; Tool wear; Stainless steel.
  
  
• Modeling and Statistical Analysis of Surface Roughness by Taguchi and RSM Techniques In Hard Turning of AISI 52100 Steel With Multilayer Coated Carbide Insert  
  by Venkat Pradeep Allu, Lingaraju D, Ramakrishna S 
  Abstract: The statistical data of surface roughness (Ra, Rz) associated with the machining parameters (cutting speed, tool nose radius, depth of cut and feed) during turning of AISI 52100 steel using multilayer coated carbide inserts was experimentally modeled in this study. Analysis of variance (ANOVA) was employed to ascertain the significance of the cutting parameters whereas Response surface methodology (RSM) depending on Taguchi design of experiments was employed to optimize the factors influencing surface roughness. The models established for approximation of Ra and Rz were 91.02% and 92.42% reliable. The most influencing parameter for Ra was tool nose radius followed by feed with contribution of 33.83% and 32.50% respectively, while the contribution of tool nose radius and feed rate for Rz was 39.21% and 33.46%. The optimum combination obtained through multi response optimization for minimum roughness was 70m/min cutting speed, 0.05mm/rev feed, 0.1mm depth of cut and nose radius of 1.2mm.
  Keywords: Response surface methodology; Variance analysis (ANOVA); AISI 52100; multilayer coated carbide; Surface roughness; Hard turning.
  
  
• Tool Wear Deceleration in Turning of Inconel 625  
  by Mohammad Lotfi, Ali Akhavan Farid, Mehran Jahanbakhsh 
  Abstract: Rapid tool wear is one of the most important problems in rough turning of nickel-based super-alloys. In this study, high material removal rate and low tool wear of PVD-TiAlN coated carbide were considered as objective factors in rough turning of Inconel 625 super-alloy. The tool wear was measured using optical microscopy, and the wear mechanism was analyzed by scanning electron microscope. Built-up edge in some cutting conditions were identified using x-ray spectroscopy. An input-output relationship model was developed using adaptive network based fuzzy inference system. The results indicate that cutting speed and depth of cut with their interaction are the most effective factors on tool wear. Feed rate which had the lowest effect on tool wear propagation can be increased to obtain higher material removal rate. Moreover, the optimized cutting condition was obtained at the lowest cutting speed by the optimization method of simulated annealing algorithm.
  Keywords: Inconel 625; turning; wear; ANFIS; carbide; optimization.
  
  
• A COMPARATIVE STUDY ON THE SURFACE FINISH ACHIEVED DURING FACE MILLING OF AISI 1045 STEEL COMPONENTS USING ECO-FRIENDLY CUTTING FLUIDS IN NEAR DRY CONDITION  
  by Milon Selvam Dennison, Abisha Meji M, Nelson A.J.R, Balakumar S, Prasath K 
  Abstract: This paper elucidates the effect of Near Dry Machining (NDM) on the surface quality achieved during face milling of AISI 1045 steel components using the conventional emulsified mineral oil cutting fluid and emulsified cutting fluid prepared from eco-friendly non-edible unrefined oils such as castor oil, cottonseed oil and neem oil. This work was completed in a FANUC arrangement CNC vertical machining centre (VMC) with three TiN coated carbide inserts of 0.4mm nose radius adjusted into a face milling cutter of 25 mm in diameter. The machining parameters considered in this investigation are number of passes, depth of cut, spindle speed and feed rate. The experiments were planned based on Taguchis L9(34) orthogonal array. The surface roughness of the machined components is measured using a surface roughness tester and subsequently, a mathematical model was developed for the average surface roughness values through regression analysis for all the machining conditions. The significance of the selected machining parameters and their levels of surface roughness are found by analysis of variance (ANOVA). The results revealed that machining under near dry condition using eco-friendly cutting fluids provides better product surface quality than the conventional cutting fluid.
  Keywords: AISI 1045; near dry machining; eco-friendly cutting fluids; face milling; vertical machining center (VMC); Taguchi technique; ANOVA.
  
  
• Effects of density and microstructure on surface integrity of HIP materials  
  by Sun Fujian, Qu Shengguan, Fei Su, Deng Zhaohui 
  Abstract: Ti-6Al-4V materials with different densities were prepared using hot isostatic pressing (HIP) technology. Surface integrities of the HIP materials were studied to analyze the surface integrity changing trend with density and microstructure. Due to the existence of micro-voids of the HIP material micro-hole appeared in the machined workpiece surface, which resulted in the formation of the deeper and greater micro-hole defects with decreasing material density. The serrated chip formation, different nanoindentation hardness of crystalline structures and micro-void existence had a potential to make the plastic deformation of the workpiece surface layer along the cutting direction to be different. Refined β phase and micro-void greatly affected plastic deformation of the workpiece surface layer, and the residual tensile stress was influenced by the microstructure and residual micro-void in machining of the HIP materials prepared with different HIP parameters.
  Keywords: Ti-6Al-4V; Hot isostatic pressing; Density; Microstructure; Surface integrity; Micro-void.
  
  
• Surface modification of ZE41A magnesium alloy using electrical discharge coating with semi sintered electrode  
  by ELAIYARASAN U, SATHEESHKUMAR V, SENTHILKUMAR C 
  Abstract: This present paper highlights the influence of WC/Cu composite powder metallurgy semi sintered electrode on the substrate of ZE41A magnesium alloy through electrical discharge coating (EDC). The effect of predominant process parameters such as compaction load, current and pulse on time during EDC on metal transfer rate (MTR) and Surface roughness (Ra) have been studied. Experiments have been carried out through central composite design (CCD) by response surface methodology (RSM). The developed empirical model is used for analyzing the machining parameters on EDC. The most significant EDC parameters were ascertained using analysis of variance (ANOVA). From the experiment results, it can be revealed that the MTR is higher at low compaction load, high current and pulse on time. Surface roughness diminished at high compaction load, low current and pulse on time. Surface morphology of coated surface has been evaluated using scanning electron microscope (SEM). Presents of elemental analysis has been carried out using energy dispersive spectroscopy (EDS).
  Keywords: ZE41A magnesium alloy; Electrical discharge coating; Response surface methodology; Metal transfer rate; Surface roughness.
  
  
• A comparative study in prediction of surface roughness & flank wear using artificial neural network & response surface methodology method during hard turning in dry and forced air-cooling condition  
  by Sanjib Kr Rajbongshi, Deba Kumar Sarma 
  Abstract: In the present work, a turning operation is performed in a green environment of dry and forced air-cooled condition to avoid the flooded coolant or minimum quantity lubrication. The work piece material considered is hardened AISI D2 steel (48 HRC) and the tool material is tungsten coated carbide tool. Cutting speed (v), feed rate (f) and depth of cut are taken as process parameters and surface roughness, flank wear, cutting force and feed force as performance parameters. Dry turning (DT) is found to be favorable for minimizing surface roughness, cutting force and feed force, while air-cooled turning (ACT) is favorable for reducing flank wear. Artificial neural network (ANN) and response surface methodology (RSM) models have been developed for prediction of surface roughness and flank wear. Regression coefficient (R2), confirmed that ANN model is better as compared to that of RSM model.
  Keywords: DT; ACT; ANN; RSM; Surface roughness; Flank wear; Cutting force; Feed force; Green environment.
  
  
• COMPARATIVE STUDY OF THEORETICAL AND EXPERIMENTAL FORCES IN MICRO DRILLING OF ALUMINUM 6061-T6  
  by M.S. Shunmugam, S. Ravisubramanian 
  Abstract: Micro holes are needed in certain miniature components that find applications in aerospace, automobile and electronic industries. Micro drill used for producing such holes has two cutting elements, namely lip and chisel edge, participating in the material removal. Taking Aluminum 6061-T6 as workmaterial, the thrust and torque are predicted for micro-drilling of 0.5 mm size hole using a mechanistic approach. Appropriate cutting mechanics at different zones namely cutting lip, chisel edge and indentation zones are considered and individual as well as combined effects of edge radius and material strengthening on thrust force and torque have been brought out for the first time. It is shown that the major contributions of chisel edge towards thrust force and cutting lip towards torque are 70.3-91.0 % and 61.7-63.4 % respectively in the selected feed range. Predicted values of thrust force and torque are found to be in good agreement with experimental values obtained in peck drilling trials carried out on an ultra-precision KERN Evo machining centre.
  Keywords: Micro-drilling; Cutting Edge Radius; Material Strengthening; Thrust force and Torque; Mechanistic Approach; Aluminum alloy.
  
  
• Multi-Response Optimization of Machining Aluminum-6061under Eco-friendly Electrostatic Minimum Quantity Lubrication (EMQL) Environment  
  by Muhammad Jamil, Aqib Mashood Khan, Ning He, Liang Li, Wei Zhao, Shoaib Sarfraz 
  Abstract: The emerging grave consequences of conventional coolants on our health, ecology and product quality, scientific research for effective and eco-friendly lubrication technique is advancing in the manufacturing. The eclectic technique Electrostatic Minimum Quantity Lubrication (EMQL) has been underscored as a burgeoning technology to cut down the health and environmental impact associated with the machining. Thus, machining parameters can be optimized by practicing EMQL to boost the overall machinability. The present research confers the adoption of biodegradable vegetable oil in turning of Aluminum-6061 T6 material. A cold mist of compressed air has negatively charged castor oil was employed at tool-workpiece cutting zone by varying the cutting conditions, as per experimental designed accomplished through Response Surface Methodology (RSM). For comprehensive sagacity, a range of cutting speed, feed, depth of cut and EMQL flow rate were considered for this neophyte technique. Material Removal Rate (MRR), tool life, surface roughness and power consumption by the machine tool were adopted as performance measures. An endeavor has been practiced to optimize the mentioned above measures in such a way that multi-criterion could be satisfied simultaneously up to the predicted level. It encouraged to apply the multi-objective optimization dilemma figured out by RSM based Grey Relational Analysis (GRA). By considering the highest proportion of Grey Relational Grade (GRG) as a single desideratum response function, the optimum machining combination provided a trade-off between performance measures. Besides, numerical results showed 15.56% improvement in GRG under multi-objective optimization. The approach mentioned above has been acknowledged as a prolific in a situation where simultaneous optimization of numerous performance measures is essential.
  Keywords: Tool Life; Surface Roughness; Energy Consumption; Sustainable manufacturing; RSM based Grey Relational Analysis(GRA);.
  
  
• Optimization of EDC Parameters using TOPSIS approach  
  by Senthilkumar Chinnamuthu 
  Abstract: Aluminium alloys are extensively used in the aeronautics and automotive industries due to light weight and good specific strength, but it has poor surface property, especially of sliding components under direct contacts with other materials, under high load cause serious damage. For this reason, a novel surface modification technique has been developed to improve the wear resistance of the material with existing electric discharge machining (EDM) process called electric discharge coating (EDC) with sintered electrodes. The process parameters selected for the experimentation are current, pulse-on time and pulse-off time. The modified surface was evaluated by the performance measures such as deposition layer thickness (DLT) and surface roughness (SR). The experimental plan adopts the face-centered central composite design (CCD) using response surface methodology (RSM). The contour plots were generated to study the effect of process parameters as well as their interactions. Surface roughness and DLT is uniform with increase in pulse off time. Lower pulse off time, increases the layer thickness and surface roughness. Different characteristic of deposition layer thickness and surface integrity were evaluated through scanning electron microscope (SEM). The process parameters are optimized based on TOPSIS. From the optimization, the optimal coating combination of parameters are current 10 amps, pulse on time 500μs and pulse off time 500μs and corresponding responses maximum Deposition layer thickness of 112.083μm and minimum surface roughness of 4.55μm respectively.
  Keywords: EDC; surface roughness; deposition layer thickness; Topsis. rnrn.
  
  
• Study on grinding-chemical machining of Al7075  
  by Abdolhamid Azizi, Pooya Bahrami 
  Abstract: Chemical machining (CHM) uses a chemical etchant to remove material from the machining zone. Two of the downsides for this method are time-consuming and low surface quality. Wheel loading and surface burning are also two of the major problem in soft material grinding. By combining the chemical machining and grinding, we introduce a mechano-chemical hybrid machining in which the described problems are resolved. The reason for the prominence of this machining method is demonstrated from two points of view; the first one is machining efficiency and the second one is surface quality. In comparison with chemical machining, the surface roughness (Ra) decreased on average by 100% moreover, material removal rate was ameliorated 600% and a burr-free surface was machined. In the second step, due to pre-machining conducted by chemical etching, the priority of the hybrid process compared to grinding is proved by tacking in to account the wheel loading, grinding ratio and surface quality.
  Keywords: Chemical machining; Surface roughness; Etching; Grinding; Machining; Material removal rate; Loading; Hybrid machining; Grinding ratio; Machining efficiency.
  
  
• Optimization of Spark Erosion Machining Process Parameters using Hybrid Grey Relational Analysis and Artificial Neural Network Model  
  by N. Manikandan, Raju Ramesh, D. Palanisamy, J.S. Binoj 
  Abstract: Haste Alloy C276 is a hard to machine superalloy and extensively used in various engineering applications such as aerospace, nuclear reactor and gas turbine industries. Haste Alloy C-276 possess good strength and lower thermal conductivity which results in decreased tool life and poor machinability by conventional machining methods. Advanced machining processes have developed over a period to fulfill the above mentioned demands and claimed to be an appropriate alternative method to traditional metal removal processes. Electrical Discharge Machining (EDM) is one of the advanced machining process which has been used for machining of hard materials. This present investigation details an investigation on EDM process and development of hybrid Grey ANN model for EDM process. The experiments are designed by Taguchis design of experiments approach and the statistical analysis, Analysis of Variance (ANOVA) has been used to ascertain the importance of process variables on output variables. Grey Relational Analysis (GRA) is employed for obtaining the grey relational grade to represent a multi aspect optimization model. An Artificial Neural Network (ANN) model has been evolved to predict the Grey Relational Grade (GRG). Grey Relational Coefficient (GRC) values are given as input for developing the neural network model. Hybrid Grey and Artificial Neural Network (ANN) model have been developed to predict the desired multiple performance machining characteristics. A comparison has been performed between the experimental and the predicted values.
  Keywords: Electrical Discharge Machining (EDM); Hard Materials; Haste Alloy; Taguchi’s Methodology; Form and Orientation Tolerances; Grey Relational Analysis (GRA); Artificial Neural Network (ANN).
  
  
• Influence of vibration on mechanical polishing micro-structured surface using discrete element method  
  by Guilian Wang 
  Abstract: A model using discrete element method (DEM) was conducted to simulate vibration assisted mechanical polishing micro-structured surface process by particle flow code in 3 dimensions (PFC3D). The effect laws of vibration frequency and amplitude on abrasive grains and polishing force were researched in detail according to the simulation results. The effects of vibration on the particles average motion velocity in one fluidcell were researched, and the simulation results show that average velocity increases with increase of vibration frequency and amplitude on the whole. The effects of vibration on the unbalanced force acting on the workpiece surface were quantified at first. The changes of average unbalanced force obviously increase for low feed rate with increase of frequency and increase approximately linearly with increase of amplitude. It is concluded that vibration with high frequency and great amplitude can significantly increase machining efficiency and improve surface quality in micro-structured surface polishing.
  Keywords: Polishing; vibration; micro-structured surface; discrete element method.
  
  
• Powder Additives Influence on Dielectric Strength of EDM Fluid and Material Removal  
  by Jeavudeen Shiek, Siddhi Jailani H, Murugan Mariappan 
  Abstract: Electrical Discharge Machining (EDM) is used to machine difficult-to-machine materials having high hardness and toughness. One of the recent advancements in the EDM process is the Powder Mixed EDM (PMEDM) process, in which the metallic or abrasive additives in the form of fine powders are added to the dielectric fluid. Powder Mixed EDM (PMEDM) was found to improve machinability in terms of higher material removal rate (MRR) and enhanced tool wear index (TWI), by reducing the breakdown strength of the dielectric. In PMEDM process, machining happens with relatively larger spark gap with enhanced machining characteristics. This paper investigates the influence of powder mixing on the breakdown strength of the liquid dielectric and the gap voltage. Determination of dielectric strength was carried out with a specially designed experimental set-up adhering to ASTM standard D1816 97. Tests were conducted using Silicon carbide, Alumina, Copper and Aluminium powders. The effect of varying the grain size was also studied. An experimental set-up was also designed and realized to measure the influence of powder mixing on the gap voltage and material removal rate in machining titanium alloy. The results have shown significant improvement in Material Removal Rate and Tool Wear Index.
  Keywords: PMEDM; Metallic and abrasive powders; Dielectric strength; Gap Voltage; Material Removal Rate; Tool Wear Index.
  
  
• Machining of thin sections using multi-pass Wire Electrical Discharge Machining process  
  by Deba Kumar Sarma, Meinam Annebushan Singh 
  Abstract: The increasing application of fine metallic sections in various sophisticated areas has led to the growth of advanced machining technique to produce thin metallic sections. Wire electrical discharge machining process can prove to be an effective means to machine such sections. The current work identifies the thin wall machining of H13 tool steel using Taguchis design. An optimal parametric setting is identified using a regression model for lower kerf width (kf) and higher machining rate. The decrease in kf and increase in machining rate is found to be highly dominated by the variation of the input parametric conditions. Machining of thin wall sections is performed to identify the extent of minimum sections that can be machined. A mesh-like structure is observed at fine wall thickness of less than 80
  Keywords: WEDM; multipass; thin wall; recast layer; Taguchi; regression; optimisation.
  
  
• Machining of aluminium based metal matrix composite - a particle swarm optimization approach  
  by Diptikanta Das, Vivek Chakraborty, Bijaya Bijeta Nayak, Chandrika Samal 
  Abstract: Machining performance of 5 wt.% silicon carbide particulate reinforced Al 7075 matrix composite was investigated in terms of cutting tool temperature (T), average surface roughness (Ra) and tool flank wear (VBc) during turning in pollution-free air water spray cooling environment. Metal was removed by multiple layers of TiN coated carbide inserts during turning. Non-linear regression models were developed and their adequacies were verified. Significance of process parameters on the responses was investigated through Analysis of Variance. The responses were optimized individually using Taguchi technique and then simultaneously through Particle Swarm Optimization technique. The proposed multi-objective algorithm outperformed the traditional Taguchi approach and effectively resulted to a group of non-dominated solutions. Pareto optimal fronts were compiled and plotted for T, Ra and VBc, which can be selected according to the production requirements.
  Keywords: Metal matrix composite; Turning; Regression; Analysis of Variance; Particle swarm optimization.
  
  
• Machining of Titanium and Titanium Alloys by Electric Discharge Machining Process: A Review  
  by Vivudh Gupta, Balbir Singh, R.K. Mishra 
  Abstract: Electric Discharge Machining (EDM) process is a non-traditional thermal based machining process which is widely used for the machining of hard materials such as ceramics and super alloys. Titanium (Ti), whose hardness ranges from HRB 70-74, is one such hard material which can be machined by EDM process to create intricate shapes and contours. This review paper presents the contribution of different researchers in machining of Titanium and its alloys by EDM process. Problems encountered during machining of Ti and its alloys are also discussed. New research avenues like introduction of abrasives & powder in dielectric fluid, use of hybrid techniques, introduction of cryogenic treatment, etc to improve the machinability of Ti and its alloys by EDM process are highlighted. Use of modelling and optimization techniques like Taguchi Method, Response Surface Methodology, Artificial Neural Network, Grey Relational Analysis, etc to predict the behaviour of complex process during electric discharge machining of Ti & its alloys is also shown.
  Keywords: titanium; alloys; EDM; machining; Ti6Al4V.
  
  
• Wear of Silicon Carbide Wheel During Grinding of Intermetallic Titanium Aluminide  
  by Nithin Tom Mathew, L. Vijayaraghavan 
  Abstract: An experimental investigation is reported on the wear of silicon carbide wheel and its influence on the wheel topography and grinding behaviour during the surface grinding of high performance intermetallic gamma titianium aluminide. The radial wear of the wheel was characterized by initial transient state followed by a steady state wear regime and finally a steel rise in wear rate. The initial transient region progressed up to a radial wear of 40
  Keywords: wear; grinding; silicon carbide; titanium aluminide; force; surface; integrity.
  DOI: 10.1504/IJMMM.2019.10021469
   
  
• Pulsed laser machining of high-performance engineering and biomedical alloys  
  by Asma Perveen, Adrian Lutey, Luca Romoli, Annamaria Cucinotta, Stefano Selleri 
  Abstract: The exceptional mechanical and thermal properties of high-performance engineering and biomedical alloys lead to difficulties in machining with conventional processes. This work explores nanosecond pulsed laser machining as a flexible alternative to overcome manufacturing-related limitations associated with Ni Hastelloy, Ti-6Al-4V titanium alloy and Stellite 6K. An extensive experimental campaign was performed with a 1064 nm nanosecond pulsed fibre laser, quantifying the ablation threshold, penetration depth and material removal rate as functions of average laser power (2 − 20 W), repetition rate (20 − 80 kHz), scanning velocity (100 − 2000 mm/s) and number of laser passes (1 − 20). The single-pulse ablation threshold was established as 7 J/cm^2 for all tested alloys. Highest material removal rates were achieved with a single laser pass at 1000 mm/s with moderate pulse fluence (18 J/cm^2) and a repetition rate of 80 kHz; however, heat accumulation and weak material ejection led to macroscopic melting effects and unsuccessful machining at low scanning velocity or with a high number of laser passes. Higher pulse fluence and high scanning velocity with a lower repetition rate was instead found to achieve a more stable process due to stronger material ejection and more limited heat accumulation effects. Optimum conditions for machining were therefore achieved for all alloys with 20 W average power, 20 kHz repetition rate and 1000 mm/s scanning velocity due to strong ejection of the liquid phase with high pulse fluence (71 J/cm^2), good process stability and material removal rates in the range 0.08 − 0.17 mm^3/s.
  Keywords: Ni Hastelloy; Ti-6Al-4V; Stellite 6K; Pulsed Laser Machining; Nanosecond Ablation; Non-Conventional Machining; Heat Accumulation; Ablation Threshold; Removal Rate; Penetration Depth; Machining Quality.
  
  
• OPTIMIZATION OF TURNING PARAMETERS FOR MINIMIZING SPECIFIC CUTTING ENERGY WITH USE OF DIFFERENT COOLING/LUBRICATING TECHNIQUES  
  by Djordje Cica, Branislav Sredanovic, Sasa Tesic, Davorin Kramar 
  Abstract: The objective of this paper is optimization of the machining parameters using the Taguchi method to obtain minimum specific cutting energy. Considering the machining parameters such as speed, depth of cut and feed rate, a series of turning experiments were conducted to measure the main cutting force required to calculate specific cutting energy. The experiments were performed on C45E steel bars using coated carbide inserts under different cooling/lubrication conditions, namely, flooded cooling, minimal quantity lubrication and high pressure cooling cutting. The concept of signal-to-noise ratio was employed to find the optimal levels of the process parameters. Analysis of variance was applied to estimate the significance of control factors affecting specific cutting energy. Finally, the results of confirmation experiments with optimal process parameters settings showed that the Taguchi method can be successfully applied in the optimization of process parameters for minimum specific cutting energy.
  Keywords: specific cutting energy; optimization; Taguchi method.
  
  
• Rotary ultrasonic machining of ZrO2-NbC and ZrO2-WC ceramics  
  by Alejandro Sanda, Carmen Sanz 
  Abstract: ZrO2 based ceramics are extremely difficult to manufacture, being rotary ultrasonic machining (RUM) an interesting machining process for these materials. In this work, ZrO2-NbC and ZrO2-WC ceramic composites have been RUM processed and the differences in cutting forces, surface quality and dominant machining mechanisms under different machining operations and conditions have been studied. In ZrO2-NbC the presence of the ductile fracture material removal mode is more evident than in ZrO2-WC, where the brittle fracture mode seems to be dominant. This contributes to a slightly better machinability of ZrO2-NbC compared to ZrO2-WC, what results in slightly higher material removal rates (MRR) and lower surface roughness.
  Keywords: Rotary Ultrasonic Machining (RUM); ZrO2-WC; ZrO2-NbC; Ceramic.
  
  
• Micro milling of polymeric micro injected specimens with randomly oriented Carbon Nanotube fillers  
  by Claudia Pagano, Aldo Attanasio, Lara Rebaioli, Elisabetta Ceretti, Irene Fassi 
  Abstract: The interest in the application of Carbon Nanotube (CNT) composites is recently increasing in several industrial sectors. The main reason for this growing attention is the reinforcing effect of the CNTs. However, the composite use is limited by technological issues concerning the manufacturing processes when small features are required. A multistage process chain could exploit the advantages of suitable processes to enhance the control of the filler orientation. This paper investigates the feasibility of milling micro features on micro injected specimens of POM/CNT and LCP/CNT composites. Design of Experiment is used to study a suitable experimental design to investigate the influence of the material and the process parameters on the machinability and the feature geometry. POM-based composites showed a better machinability and allowed a fabrication of more accurate features, while LCP showed high cutting forces and the presence of diffused burrs, preventing the fabrication of very small features.
  Keywords: Micro machining; micro milling; micro injection moulding; carbon nanotubes; polymer composites.
  
  
• An approach to residual stress measurement in ball-end milling process on Ti-6Al-4V ELI titanium alloy  
  by Jorge Andrés García-Barbosa, Ernesto Córdoba-Nieto 
  Abstract: Evaluation of the residual stress state in a surface, obtained by means of the ball-end milling process, is important to ensure the reliability of the machined product during its life cycle. X-ray diffraction is one of the techniques most commonly used for evaluating residual stresses. A review of the specialized bibliography shows the shortage of a methodology for this type of studies on materials with more than one crystalline phase. In this experimental research for evaluating the state of residual stress in a series of samples machined with a ball-end mill on the Ti-6Al-4V ELI titanium alloy, it was found that they were subject to compressive residual stress. An electropolished surface of the same material was taken as a reference pattern. The X-ray diffraction analyses were carried out on the crystallographic planes {10-12} and {10-13} of the alpha phase of the alloy.
  Keywords: X-ray diffraction; residual stress measurement; residual stress state; surface integrity; ball-end milling; Ti-6Al-4V titanium alloy.
  
  
• Investigations into the influence of tool helix angle during end milling of open straight and curved thin-wall parts  
  by Gururaj Bolar, Shrikrishna Nandkishor Joshi 
  Abstract: In this paper, the influence of cutting tool helix angle on performance parameters viz., milling force, part deflection, surface finish, chip morphology and micro-hardness considering open straight and curvilinear thin-walled parts is analyzed. It was found that end mills with helix angle of 45
  Keywords: thin-wall; helix angle; chip morphology; micro hardness; milling force; surface roughness; built-up-edge; finite element simulation.
  
  
• Fabrication of Cascade Micropattern by Maskless Electrochemical Micromachining  
  by SANDIP KUNAR, B. Bhattacharyya 
  Abstract: Cascade micropattern is the basic complex textured surface, which is generated on different microdevices for various advanved micromanufacturing applications. This paper highlights the experimental analysis into generation of cascade micropatterns on stainless steel (SS 304) by maskless electrochemical micromachining (EMM). The experimental setup consisting of electrode fixtures, EMM cell, power supply unit and electrolyte flow system is indigenously developed for fabrication of cascade micropatterns inexpensively without fabrication of one by one complex microfeature of cascade profile by a single microtool. One textured tool with SU-8 2150 mask can fabricate more than twenty five cascade micropatterns. Influences of EMM parameters such as electrolyte concentration, electrolyte flow rate, pulse frequency and inter electrode gap on depth, width overcut and surface roughness (Ra) is studied during generation of cascade micropattern. An attempt has also been done to analysis the micrographs of generated cascade micropattern for investigating the suitable parameter setting. This investigation will be needful and fruitful for machining of need-based cascade micropatterns on microdevices like micromixers, microactuators, microcoolers, etc.
  Keywords: Maskless EMM; cascade micropattern; reused textured tool; width overcut; depth; surface roughness.
  
  
• Dynamical Analysis for the Motorized Spindles of Machine Tools
  by Nguyen Ngoc Nam , Sam-Sang You, Sang-Do Lee, Pham Dinh Tung  
  Abstract: The spindle dynamics directly affect the cutting forces, and typically the topography of machined surface of workpieces. In this study, the dynamical behaviours of spindle system are considered in details for accuracy monitoring of CNC machines. Firstly, the rotational model has been established for the spindle with the servo motor. Secondly, the phase portraits of the dynamical models are provided by vector field analysis, depicting rotational behaviours for the spindle operations. In addition, the bifurcation analysis shows that the machining process can be dynamically stable and unstable by changing control parameters. Spindle rotational behaviours are described by the cutting forces which have significant influence on overall machining performance. Finally, it is noted that stability analysis of spindle speed is essential to characterize tool behaviours and machining accuracy while avoiding chattering.
  Keywords: Spindle dynamics; cutting forces; dynamical analysis; machining process; bifurcation; nonlinear model.
  
  
• Some Investigations on Surface Quality Indicators for OHNS Die Steel Machined with Suspended Powder EDM Process
  by Nitin Khedkar, Arunkumar Bongale, Satish Kumar, Vijayshri Khedkar, Vinay Kumar D 
  Abstract: The study focuses on the evaluation of surface quality characteristics of oil hardened non shrinking die steel surface machined with suspended powder electrical discharge machining process. Pure copper metal is used as an electrode material, and tungsten powder is used as suspended medium for the purpose. Machining experiments were carried out by varying one parameter at a time. After each test, the machined surface is analyzed for evaluating its surface roughness and microhardness values. It is found that combination of 4 A gap current, 12 µs pulse on span and 7 µs pulse off span will result in optimum surface quality indicators for the SPPEDM process. Also, dry sliding wear experiments were carried out on the machined surface to evaluate the frictional force and coefficient of friction. Spectroscopic analysis and Energy dispersive x-ray diffraction analysis on the machined surface indicate a considerable rise in carbon and tungsten content on the recast white layer of the machined surface. Scanning electron microscopic analysis of the machined surface revealed the presence of compounds of tungsten on the recast white layer. Also, micro-cracks were observed on the machined surface which is due to higher gap current setting during EDM process.
  Keywords: SPEDM, Surface Finish, Microhardness, Recast Layer, White Layer, OHNS steel