Efficiency Of Machining Process Research Articles

Application Potential of Fuzzy and Regression in Optimization of MRR and Surface Roughness during Machining of C45 Steel

In the machining industry, coolant has an important role due to their lubrication, cooling and chip removal functions. Using coolant can improve machining process efficiency, tool life, surface quality and it can reduce cutting forces and vibrations. However, health and environmental problems are encountered with the use of coolants. Hence, there has been a high demand for deep cryogenic treatment to reduce these harmful effects. For this purpose, −196 °C LN2 gas is used to improve machining performance. This study focuses on the prediction of surface roughness and material removal rate with cryogenically treated M2 HSS tool using fuzzy logic and regression model. The turning experiments are conducted according to Taguchi's L9 orthogonal array. Surface roughness and material removal rate during machining of C45 steel with HSS tool are measured. Cutting speed, feed rate, and depth of cut are considered as machining parameters. A model depended on a regression model is established and the results obtained from the regression model are compared with the results based on fuzzy logic and experiment. The effectiveness of regression models and fuzzy logic has been determined by analyzing the correlation coefficient and by comparing experimental results. Regression model gives closer values to experimentally measured values than fuzzy logic. It has been concluded that regression-based modeling can be used to predict the surface roughness successfully.

Investigation on the Effects of Nanoparticles on Cutting Fluid Properties and Tribological Characteristics

The application of cutting fluid is required to enable efficient machining processes. Depending on the process, additives are used to adjust the performance of the cutting fluid. This paper presents the strong influence of nanoparticles and microparticles on the cutting fluid properties as well as the tribological behavior. The effects of the particle size, the concentration and the base fluid were investigated for two different metal oxides, Al2O3 and ZrO2, as well as silica. While most nanoparticles achieved an improved lubricity, the opposite was found for Al2O3.

One-step machining of hierarchical micro-nano structures on Al-Mg alloy as superamphiphobic substrate for amplified SERS trace detection

Ultra-trace detection from polluted solution makes great contribution to environmental monitoring, food safety and medical analysis. However, its common difficulty arises in concentrating analytes on easily accessible substrate for highly amplified detection intensity. Herein, a superhydrophobic Al-Mg alloy surface focusing on droplet condensation and analyte detection is fabricated by an environment-friendly, efficient and low-cost machining process for surface enhanced Raman scattering (SERS) analyses. The micro-scale craters covered with nano-scale terrace-like structures have been prepared by one-step wire electrical discharge machining (WEDM). Meanwhile, wet abilities of hierarchical structures have been investigated after stearic acid modification. Results show that the as-prepared surface exhibits excellent repellent ability to water and oil drops. The resultant superamphiphobic surface also displays a 3-fold higher SERS intensity over hydrophilic Al-Mg alloy substrate. The corresponding SERS signals also show well signal reproducibility. This work sheds positive insights into fabricating accessible and efficient active substrates for SERS detection and extending potential applications of Al-Mg alloys in ultra-trace analysis in the future.

Application of deep visualization in CNN-based tool condition monitoring for end milling

Abstract Cutting tool is one of the major components to largely influence the overall machining process efficiency. There has been a significant amount of research conducted in developing tool condition monitoring systems with the application of various sensory systems and artificial intelligence techniques for processing and predicting tool wear. Although artificial intelligent techniques have shown significant results in tool condition prediction, the fundamental methodology adopted by these techniques for predicting tool condition still needs to be investigated. This study aims in applying and investigating deep learning techniques for tool condition monitoring in end milling process based on spectrogram features of audible sound collected during the machining process and employing a deep visualization technique to gain the knowledge on inner workings of the deep learning models in the tool wear prediction. Specifically, this study applies Convolutional Neural Networks (CNN) to develop a tool condition monitoring model and performs hyper-parameter tuning to improve prediction accuracy. In addition, the class saliency extraction technique has been used by this study to generate the saliency maps to visualize the specific features utilized by the CNN model for a given spectrogram of audio signal. Furthermore, the study examines the saliency maps of different tool condition levels to understand the intuition of proposed CNN model in selecting the specific localized features of spectrogram for accurate prediction.

Computer aided Genetic Algorithm based Optimization of Electrical Discharge Drilling in Titanium alloy (Grade-5) Sheet

Abstract Precise and micro holes in the different advanced materials such as Ti and their alloys is a very challenging task due to unfavourable characteristics of these materials by conventional machining. These problems may be minimised upto some extent by using new class of machining processes such as advanced machining processes. In the category of advanced machining processes, the electrical discharge drilling is the efficient and cost effective machining process for the machining of these materials. But some quality characteristics such as hole circularity, hole taper and hole dilation are the main problem associated during the machining of these materials by using electrical discharge machining. These may be minimized by selecting the optimum process parameter levels. In this study, the experiments have been conducted by using L27 orthogonal array. The discharge current, pulse on time, pulse off time and dielectric pressure have been selected as input process parameters and hole circularity, hole taper and hole dilation as output parameters. The multi regression models for hole circularity, hole dilation and hole taper have been developed by using the experimental data. The statistical analysis for the developed models shows that the models are reliable and adequate and may be used for predicting these quality characteristics satisfactorily. These quality characteristics have been optimized by using computer aided genetic algorithm based optimization method. For the optimization, the multi regression models for circularity, dilation and taper have been considered as objective function. The multi-objective optimization result obtained by computer aided genetic algorithm based optimization method, show improvements in all of the quality characteristics.

Multi-objective optimization and life cycle assessment of eco-friendly cryogenic N2 assisted turning of Ti-6Al-4V

Modern manufacturing industries thrive for energy efficient, clean and sustainable machining processes. However, achieving these objectives becomes difficult especially in machining Ti-6Al-4V as it retains its properties at high temperature. Cryogenic liquid nitrogen (LN2) is a clean machining environment that has potential to improve the machinability performance for Ti-6Al-4V. LN2 promotes sustainability and facilitates low carbon emission. Orientation and number of employed LN2 jets influence the cutting energy, quality and productivity. Moreover, a balance between energy consumption and quality-productivity is required for sustainable production. In this respect, this research work studies the cutting force, specific energy, temperature, surface quality (i.e. surface roughness), and material removal rate under the impingement of LN2 as mono-jet and dual-jets. This study has three parts: evaluation of the role of factors on the output parameters, optimization of parameters, and lastly the life cycle assessment (LCA) of cryogenic LN2 assisted machining. Owing to irreconcilable nature of single-objective optimization, multi-response optimization was conducted using Grey-Taguchi integrated approach. It was found that LN2 dual-jets were most effective in reducing the specific energy consumption and temperature, and improving surface quality. This can be attributed to the faster and effective heat removal by LN2 from the critical interfaces. Other optimum parameters were cutting speed of 140 m/min and feed rate of 0.16 mm/rev. It was found that LCA showed that there is a clear relation between cooling strategy and environmental aspects such as resources, energy, human health, and biodiversity, etc. that directly affects the machining performance of Ti-6Al-4V alloy.

Fiber laser cutting of CFRP laminates with single- and multi-pass strategy: A feasibility study

Experimental data is presented relating to hole quality and feasibility studies when using continuous wave (CW) fiber laser to cut CFRP laminates (6.0 mm diameter hole) with single- and multi-pass strategy. The effect of typical processing parameters including laser power and cutting speed on thermal defect was also investigated. The statistical significance of individual cutting parameters was determined using main effects plot together with ANOVA analysis. Three methods were proposed to characterize HAZ based on the feature of thermal defect. According to statistical analysis, both cutting speed and laser power were significant with respect to HAZ (recorded at hole exit). The minimal value of HAZ was recorded with laser power of 650 W and cutting speed of 1100 mm/min. Energy per unit length (El) should be set above 40 J/mm to ensure cutting through CFRP laminates using fiber laser in high efficient machining process. Multi-pass strategy was investigated without setting pause/break time between each pass in order to increase cutting efficiency. Results showed limited improvement in terms of the level of HAZ even with cutting speed up to 10,000 mm/min, while machining time was significantly reduced to cut 6.0 mm diameter hole compared with single-pass strategy. For machining small holes with diameter down to 2.0 mm, high power fiber laser was not preferred due to severe thermal defect observed at hole entry and exit.

Parametric Optimization of WEDM in Machining HSS (8X200)

Nontraditional machining processes are used for machining too hard, brittle and strong conductive materials. The aim of this research is to achieve an economic and efficient machining process in machining HSS by using wire cut machine. Experimental investigations were conducted on WEDM with using different machining parameters such as (pulse duration (μs), pulse interval (μs), Servo feed and Servo voltage (V)). The experiments were designed according to DOE, which is done by using Taguchi design parameter method to investigate the optimum machining parameters, which gives the best values for MRR and CS in order to achieve an economic and efficient machining process. The results obtained from the experimental work show that the optimum values of MRR and CS are obtained with the best values of Servo voltage (V), pulse duration (μs), pulse interval (μs), Servo feed and which they are presented with (A1, B3, C2 and D3) which they are equal to (20 v, 120 μs, 35 μs, and 450 mm/min).

A cloud-terminal-based cyber-physical system architecture for energy efficient machining process optimization

An innovative cloud-terminal-based cyber-physical system (CTCPS) architecture is presented to support energy efficient machining process optimization. The CTCPS consists of four levels: machine level, control level, data level and decision support level. The machine level and control level are composed of all kinds of terminals related to machining process and mainly responsible for monitoring machines and controlling machines to execute the optimal solutions. The data level and decision support level are deployed in cloud for data storage, management and analysis and optimization. Experiments on the practical case shows that the CTCPS is promising and has significant potential of implementation in practice.

Machining of AISI D2 Tool Steel with Multiple Hole Electrodes by EDM Process

In recent years, with the increasing of technology the demand for machining processes is increasing for the newly developed materials. The conventional machining processes are not adequate to meet the accuracy of the machining of these materials. The non-conventional machining processes of electrical discharge machining is one of the most efficient machining processes is being widely used to machining of high accuracy products of various industries. The optimum selection of process parameters is very important in machining processes as that of an electrical discharge machining as they determine surface quality and dimensional precision of the obtained parts, even though time consumption rate is higher for machining of large dimension features. In this work, D2 high carbon and chromium tool steel has been machined using electrical discharge machining with the multiple hole electrode technique. The D2 steel has several applications such as forming dies, extrusion dies and thread rolling. But the machining of this tool steel is very hard because of it shard alloyed elements of V, Cr and Mo which enhance its strength and wear properties. However, the machining is possible by using electrical discharge machining process and the present study implemented a new technique to reduce the machining time using a multiple hole copper electrode. In this technique, while machining with multiple holes electrode, fin like projections are obtained, which can be removed easily by chipping. Then the finishing is done by using solid electrode. The machining time is reduced to around 50% while using multiple hole electrode technique for electrical discharge machining.

A Special Tool for Making a Detail of the T-groove

The paper deals with the design of a special machining tool for efficient production of detail on the T-groove of the clamping part. The introductory part of the paper is focused on introducing the Czech company. The practical part of the paper deals with the analysis of the existing state of machining of the clamping body and of the production of the T-groove detail and proposes an innovative solution in the form of more efficient machining process (partial production modification), which consists in the development and production of a special tool with replaceable inserts. The main reason for this partial modification is a significant reduction in unit machine time in the production of the T-groove detail on clamp body parts. Part of the contribution is in the process of streamlining the innovation made in the form of changes to the manufacturing process and the design of the cutting conditions required to produce the T-groove detail on the clamp body parts. The contribution is completed by a technical and economic evaluation, which is related to the analysis and comparison of both proposed production variants in terms of machine times, tool consumption / replaceable inserts and total production costs for the T-groove detail production on the clamp body parts.

Effect of Abrasive Waterjet Machining Parameters on Hybrid AA6061-B4C- CNT Composites

In general, Metal Matrix Composites (MMC)are very hard to machine using conventional machining due to complexity towards elevated temperature and tool wear issues. Abrasive water jet machining is a very efficient machining process which overcomes tool wear issues and cutting temperature issues. In this research study,AA6061-B4C- CNT was machined using Abrasive Waterjet Machining under different process parameters such as mesh size, abrasive flow rate, pressure and traverse speed. Boron carbide was used as reinforcement and Carbon Nanotube (CNT) was used as a solid lubricant. Two different composition of boron carbide (5, 15 vol%) and CNT (5, 15vol%) with residual volume percentage of aluminium as a core material were fabricated using stir casting method. The Machining approach is based on the Taguchi L9 orthogonal array design to enhance the Abrasive waterjet process parameters effectively. Then the multiple responses were investigated such as kerf taper geometries (θ), surface roughness (Ra) and material removal rate (MRR). The features of different machined surface regions were studied using Scanning electron microscopy (SEM). The investigational results indicate that increasing reinforcement improves the kerf taper angle under the significant parameter of traverse speed and decreasing the reinforcement leads to the lower surface roughness under significant parameter of pressure and traverse speed. It was observed that increasing reinforcement increasing the Material Removal Rate under the significant contribution of reducing mesh size of abrasive particles and inclined velocity.

Machinability studies of aerospace steel using hot end milling

Hot Machining (HM), a hard part machining technology, has gained popularity due to its simplicity and economical solutions. It is possible to machine any material in the hardened state and can achieve the required surface finish without employing additional processes. Several HM systems have been emerged as most efficient machining processes and provided solutions for critical aerospace materials, super alloys, ceramics and composites. The aim of this paper is to investigate the effect of critical process parameters on the machinability of hardened EN24 steel using hot machining process. The material removal rate and surface finish are considered as responses as they are true measures of machinability of any material. Literature shows that little work has been carried out for EN24 steels using hot milling process. The experiments are conducted on 4-axis CNC Machining Centre, using Taguchi’s orthogonal arrays to select separate set of parameters for material removal as well as better surface finish. This report provides the details of experimentation, analysis of results and recommends the appropriate combination of process parameters to achieve better machinability in terms of surface finish and improved material removal.

Influence of different metal working fluids when micro machining cp-titanium with 50 µm diameter micro end mills

The increasing demand for micro structures and micro parts requires precise and efficient machining processes. One suitable process for the production of these structures is micro milling. Via micro milling it is possible to manufacture products with high geometric diversity and structures in a large spectrum of different materials. However, a limiting factor of the micro milling process is the high abrasive wear at the cutting edges of the micro end mills. This can be explained by size-effects, especially the high cutting edge radius to chip thickness-ratio (rß/h-ratio). High rß/h-ratios result in a high amount of ploughing as the cutting edge cannot be considered as sharp. This in turn leads to a further increase of wear of the cutting edge and ultimately in increased temperatures in the contact area, favoring the formation of built-up edges. Both, the wear of the cutting edges and the built-up edge formation have negative effects on the process results and reduce the capability as well as the efficiency of the whole process. A further reduction of the cutting edge radius is not possible because of the grain size of the cemented carbide used.One way to reduce friction and heat generation in machining processes is the use of metal working fluids. In micro milling, the wetting behavior of these fluids plays a more decisive role as in conventional machining due to the size of the structures and the surface tension of the fluid. In this paper, different fluids (isopropanol, sodium dodecylsulfate and cutting oil) with high wetting capability will be applied at minimum quantity lubrication and the results are compared to dry machining of cp-titanium. With this research, the quality of micro milled surfaces can be optimized regarding e.g. surface roughness or burr formation enabling the production of parts with an even higher functionality.

High Efficient Electrical Discharge Machining by Servo Voltage Adaptive Control

Gap distance determines the amount of effective discharging pulses in the gap; the larger the distance is the fewer amounts of effective discharging pulses are and vice versa. To achieve a high efficient machining process, it is required to increase the discharging ratio up to a certain limit beyond that arcing pulses will dominate the gap burning work-piece surface. It is easy for pulse to penetrate the gap in a condition of heavy chips accumulation in the gap and the consequence is that discharging ratio grows rapidly. In this case the gap distance which is determined by servo voltage should be enlarged to increase the difficulty of pulse penetrating in the gap. On the contrary, if the chips accumulation is light, the gap distance should be narrowed so that the penetration of gap by pulse voltage becomes easy with the consequence of discharging ratio filled with a large amount of effective discharging pulses rising. The adaptive control system is suitable for the requirement. In this paper, servo voltage is a control variable in the developed adaptive control system to drive the discharging ratio following a value which is also adapted to the machining condition in machining so that the discharging ratio will not surpass the discharging ratio limit. Based on real-time estimation of EDM process model parameters, a two-step ahead of prediction control strategy was employed to compute the control variable. By comparing open-loop machining with the machining assisted by the proposed control system, it can be found that this control system balanced the machining rate and machining stability quite well and achieved much larger machining rate than open-looped one. Moreover, the machining rate of the system is much faster than that of open-loop machining in precision machining.

Stability Analysis of Radial Turning Process for Superalloys

Abstract Stability detection in machining processes is an essential component for the design of efficient machining processes. Automatic methods are able to determine when instability is happening and prevent possible machine failures. In this work a variety of methods are proposed for detecting stability anomalies based on the measured forces in the radial turning process of superalloys. Two different methods are proposed to determine instabilities. Each one is tested on real data obtained in the machining of Waspalloy, Haynes 282 and Inconel 718. Experimental data, in both Conventional and High Pressure Coolant (HPC) environments, are set in four different states depending on materials grain size and Hardness (LGA, LGS, SGA and SGS). Results reveal that PCA method is useful for visualization of the process and detection of anomalies in online processes.

The influence of cryogenic supercritical carbon dioxide cooling on tool wear during machining high thermal conductivity steel

In the recent years, there have been increasingly tremendous demands for lightweight automotive parts, in the quest for better energy efficiency. These parts are produced using Ultra High Strength Steel (UHSS), for reasons of high strength and rigidity. However, for the parts blank to have increased strength and hardness, the forming process has to be carried out under elevated temperatures, achieved through preheating and quenching. In addition, to ensure an effective quenching, High Thermal Conductivity Steel (HTCS), having a high thermal conductivity and a high wear resistance, is used as the forming die, possibly resulting in impaired machinability. Therefore, an effective coolant-lubrication technique is required to ensure improved productivity. A cryogenic cooling technique, such as, the use of supercritical carbon dioxide (SCCO2) was reviewed in the machining processes. SCCO2 was selected over the more commonly used liquid nitrogen (LN2), as the cryogenic substance, due to its low gas expansion value, thus ensuring lower environmental hazards to the workers. In short, the non-toxic SCCO2 promotes a healthier, safer and more sustainable working environment. In this study, a milling process of HTCS was performed, where the effectiveness of SCCO2 coolant was compared with that of Near Dry Machining and Dry Machining techniques, in terms of cutting temperature, cutting force, tool wear and wear mechanism. Two methods of SCCO2 cooling conditions were analyzed, with and without lubricant. Both of the cooling conditions were applied under three different input chamber pressures. In comparison with Dry Machining, SCCO2 with lubricant was found to have significantly improved the cutting force and cutting temperature, up to 60% and 55% respectively. In comparison with Dry Machining and Near Dry Machining, meanwhile, the cutting tool life increased to 150% and 87%, respectively. More importantly, it was observed that, adhesion, attrition and abrasion were the dominant wear mechanisms, when HTCS was milled under various coolant-lubricant conditions. The overall results revealed that, cryogenic cooling, using carbon dioxide gas under supercritical state, was the best option for a better control and improvement of tool wear. The prolonged tool life will ensure a highly sustainable production, with less tool wastage and more efficient machining process. From the environmental point of view, the use of SCCO2 as a cryogenic substance is advantageous, as it fulfills the increasing demands for a cleaner manufacturing of HTCS.

A new machining strategy for roughing deep pockets of magnesium-rare earth alloys

Plunge milling is an efficient machining process for roughing deep pockets. Its efficiency is mainly due to low radial forces on the cutter. This leads to reduced bendings and vibrations that allow one to improve cutting parameter values. The machining time can then be reduced with respect to machining processes with constant Z-level. Recently, another machining process has been introduced, called ”balancing of the transversal cutting force” (BotTCF), that is also characterized by a suitable distribution of forces on the cutter. It has been applied only to finishing operations on complex surfaces. In this paper, we present two main contributions. First, we extend the BotTCF concept to roughing open deep pockets and semi-open pockets opened from side to side. This is mainly based on successive parallel ramping trajectories, defined by an optimal angle which ensures a good balancing of the transversal cutting forces. This can be applied to 3-axis and 5-axis computer numerical control (CNC) machine tools. Second, we propose a new, hybrid methodology for roughing semi-open pockets (not opened from side to side) and closed pockets. It is based on the combination of ramping trajectories with BotTCF and plunge milling. The proposed methodology is developed for three-axis machining and can be extended to five-axis machining. Based on an identical criterion (identical maximum force acting on the cutters), we perform a fair machining-time comparison of plunge milling with the proposed hybrid method applied on a closed deep pocket: a simplified aeronautical housing made of magnesium-rare earth alloy. Results show a significant gain in machining time when the hybrid method is applied.

Nozzle design for combined use of MQL and cryogenic gas in machining

Nowadays, the need for not only technically but also environmentally efficient machining processes is increasing. In this context, the reduction of oil emulsion type coolants used during machining of aeronautical engine components supposes a great challenge. In this paper, a novel approach based on the design, optimization and validation of a nozzle adaptor combining cryogenic technology and minimum quantity lubrication systems is proposed. The proposed work also deals with the aim of obtaining a cost-effective process. Thus, CO2 flow and velocity was optimized in this line. Theoretically-based analysis were performed and compared with computational fluid dynamics (CFD) simulations and with real experimental tests as well. Once optimizing these key factors, two nozzle adaptors were designed and simulated by CFD. Different geometries were tested looking for the most efficient design. Finally, to obtain a feasible industrial product, the developed nozzle was tested as a CryoMQL demonstrator comparing with other lubricoolant techniques during milling Inconel 718. Results show a successful balance between technical and environmental issues using this technology when milling aeronautical alloys.

Process Oriented Choice of Lubricant Pressure and Volume Flow to Increase Machining Process Efficiency

In machining processes, the choice of a suitable pressure and thus volume flow of lubricant supply in drilling is rather performed with respect to process stability than energy efficiency leading to energetically inefficient processes.In this paper, results regarding the cooling and resource efficiency of lubricant supply in a drilling process of TiAl6V4 are presented. The main principle is to calculate the evacuated heat energy from the cutting zone based on a calorimetrical approach. The pressure as well as the lubricant supply channel diameter have been varied. For these efficiency calculations, the cutting energy, the heat energy evacuated by the lubricant as well as the hydraulic energy were considered. The wear development as well as the chip evacuation were additionally investigated. Based on these investigations, it is shown that high pressure and volume flow lead to reduced tool wear, but not necessarily increase energy efficiency.