International Journal of Machining and Machinability of Materials (17 papers in press)

Regular Issues

• 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 H.A. 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.
  DOI: 10.1504/IJMMM.2019.10023081
   
  
• 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.
  DOI: 10.1504/IJMMM.2019.10023737
   
  
• 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.
  DOI: 10.1504/IJMMM.2019.10022891
   
  
• 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
  Keywords: SPEDM; Surface Finish; Microhardness; Recast Layer; White Layer; OHNS steel.
  
  
• Hybrid Taguchi-GRA-PCA Approach for Multi-Response Optimization of Turning Process Parameters under HPC Condition  
  by Prianka B. Zaman, S. Saha, N.R. Dhar 
  Abstract: Process parameter optimization is important in manufacturing. An effective and efficient manufacturing process offers low temperature, low force and high material removal rate without compromising the product quality. An experimental investigation designed by Taguchis orthogonal array for turning AISI 1060 steel by uncoated carbide insert under High-Pressure Coolant (HPC) condition. Since all these aforementioned responses are mutually conflicting, simultaneous multi-response optimization is required to acquire a trade-off among the responses. Standalone Taguchi method is not sufficient for multi-response optimization. Grey Relational Analysis (GRA) can be coupled with Taguchi method to overcome this complexity, where overall process performance index Grey Relational Grade (GRG) is calculated and used for the optimization of the process by using Taguchi's S/N ratio. Principal Component Analysis (PCA) can be utilized to determine the individual importance of each response, which facilitate accurate computation of overall GRG. The effect of process parameters on GRG was analyzed using Analysis of Variance (ANOVA). Validation by confirmation test was also performed.
  Keywords: Multi-response optimization (MRO); Taguchi method; grey relational analysis (GRA); principal component analysis (PCA); high-pressure coolant (HPC).
  
  
• Increasing productivity in hard turning of steels using CVD-coated carbide  
  by Armansyah Ginting, Issam Bencheikh, Mohammed Nouari 
  Abstract: An effort to achieve high Material Removal Rate (MRR) that could be gained by a triple-layer TiN/Al2O3/TiCN CVD-coated carbide tool in hard turning of steels AISI 1045 (42
  Keywords: flank wear; metal removal rate; surface roughness; triple-layer coating; volume of material removal.
  
  
• Forming and finishing surface by sequential electrochemical-electrodischarge machining of precision magnetic optics parts  
  by Oleksandr Plakhotnyi, Vasyl Osypenko 
  Abstract: A method for calculating the formation of a hyperbolic ruled surface with wire electri-cal discharge machining is proposed, considering errors caused by the deflection of wire electrode. The given approach of calculation of technological parameters for further electrochemical dimensional processing with a wire electrode is presented in order to increase reproduction accuracy and improve surface quality. The obtained accuracy and qualitative parameters of manufactured parts satisfy rigorous requirements for magnet pole tips of quadrupole lenses of nuclear microprobes. The latest combined technology of sequential electrodischarge and electrochemical processing with wire electrode in the production of precision parts of magnetic optics, which is given in the article, will be useful to specialists working with processing technologies and precision engineering.
  Keywords: wire electrical discharge machining; WEDM; electrochemical machining; ECM; EDM/ECM combined process; ECM finishing; wire electrodes; surface shape accuracy; surface quality; surface science.
  
  
• Influence of process parameters on the ultrasonic assisted edge trimming of aerospace CFRP laminates using MQL  
  by Mohamed O. Helmy, Mohamed El-Hofy, Hassan El-Hofy 
  Abstract: The use of carbon fibre reinforced plastic (CFRP) composites is increasing rapidly especially in applications demanding high performance such as aerospace structural components. Edge trimming of CFRP parts is essential for controlling the dimensional tolerances and/or the product quality to meet the industrial standards or specification. This article investigates the ultrasonic-assisted edge-trimming of multidirectional CFRP laminates when minimum quantity lubricant (MQL) was employed for the first time. Statistical analysis was conducted to assess the effect of process parameters on the performance characteristics. Cutting speed, feed rate, and radial depth of cut were selected as process parameters while the performance characteristics were cutting forces, bouncing-back, material removal rate (MRR), and surface integrity in terms of surface roughness (Ra, Rz) as well as delamination. The most significant process parameter affecting each performance characteristic was determined using ANOVA test. Regression equations were also developed to predict the magnitude of bouncing back and MRR.
  Keywords: Carbon fibre reinforced plastic; CFRP; Edge trimming; Ultrasonic; MQL.
  
  
• Studies on surface quality of stainless-steel implant material while machining with WEDM process  
  by Sivakumar S, M. Adam Khan, Muralidharan B 
  Abstract: In this research work machinability studies on stainless steel (SS 107.12) implant by wire electrical discharge machining (WEDM) process was studied. The effect of heat affected zone (HAZ), mechanical load experienced and chemical effects after implantation are the significant factors influencing the degradation of machined surface. The metallurgical behaviour of the machined implant is investigated in detail. The experiments are conducted based on design of experiments by considering the input factors like pulse on time, pulse off time and voltage. The influencing responses measured are material removal rate and surface roughness. Further the machined samples are subjected to metallurgical characterisation, using scanning electron microscope (SEM), spectroscopic (EDS) analysis and atomic force microscope (AFM). From the results it is observed that, increase in voltage has produced better surface finish and reduced the Material removal rate (MRR).
  Keywords: implant; steel; WEDM; SEM image; EDS; MRR; Ra.
  
  
• Investigations on machinability and machining stability of turning super duplex stainless steel  
  by Subhash N, Jagadeesha T, Mohit Law 
  Abstract: Super duplex stainless steels (SDSS) combine austenite and ferrite in near equal proportions along with other alloying elements giving these steels excellent mechanical and chemical properties and making them of much use across industries. The same characteristics that give SDSS advantageous properties impair their machinability and make cutting of SDSS prone to unstable process-induced chatter vibrations. The focus of this paper is to hence investigate the machinability and machining stability of dry turning SDSS. Based on systematic experimental characterization, we identify cutting force coefficients that characterize machinability and observe these coefficients to be relatively speed independent. We further observe surface characteristics to improve with cutting speeds. Using identified coefficients and measured dynamics, we predict the stability behaviour. Experimental validation confirms that the nose radius on cutting tools plays a significant role in improving the chatter vibration-free turning of SDSS. Our findings can instruct high-performance strategies for turning of SDSS.
  Keywords: Super duplex stainless steel; machinability; cutting force coefficients; dynamics; stability.