Showing papers on "Machining published in 2017"

Additive Technology: Update on Current Materials and Applications in Dentistry

Abstract: Additive manufacturing or 3D printing is becoming an alternative to subtractive manufacturing or milling in the area of computer-aided manufacturing. Research on material for use in additive manufacturing is ongoing, and a wide variety of materials are being used or developed for use in dentistry. Some materials, however, such as cobalt chromium, still lack sufficient research to allow definite conclusions about the suitability of their use in clinical dental practice. Despite this, due to the wide variety of machines that use additive manufacturing, there is much more flexibility in the build material and geometry when building structures compared with subtractive manufacturing. Overall additive manufacturing produces little material waste and is energy efficient when compared to subtractive manufacturing, due to passivity and the additive layering nature of the build process. Such features make the technique suitable to be used with fabricating structures out of hard to handle materials such as cobalt chromium. The main limitations of this technology include the appearance of steps due to layering of material and difficulty in fabricating certain material generally used in dentistry for use in 3D printing such as ceramics. The current pace of technological development, however, promises exciting possibilities.

Experimental investigations in powder mixed electric discharge machining of Ti–35Nb–7Ta–5Zrβ-titanium alloy

Abstract: The present research is the first type of study in which the application of powder mixed electrical discharge machining (PMEDM) for the machining of β-phase titanium (β-Ti) alloy has been proposed....

A review identifying the effectiveness of minimum quantity lubrication (MQL) during conventional machining

Abstract: Government legislation and public opinion are the main drivers behind the movement of manufacturing companies towards sustainable production. Fundamentally, companies want to avoid future financial penalties and the industry is therefore under pressure to adapt new techniques and practices in order to become environmentally friendly. The cost efficiency of metal cutting operations is highly dependent on accuracy, excellent surface finish and minimized tool wear and, to this end, has traditionally made abundant use of cutting fluid in machining operations. However, these cutting fluids have been a major contributor to environmental and health issues. In recent years, an enormous effort to eradicate these adverse effects has been made with one important focus being the implementation of minimum quantity lubrication (MQL). In the present work, the authors have reviewed the current state of the art in MQL with a particular focus on drilling, turning, milling and grinding machining operations. Overall, it is concluded that MQL has huge potential as a substitute for conventional flood cooling.

Machinability of natural fiber reinforced composites: a review

Abstract: In the recent years with greater emphasis on the environmental and sustainability aspects of engineering materials, natural fiber reinforced composites (NFRCs) are gaining more importance because of their numerous advantages. Several researchers have developed NFRCs using various natural fibers as well as matrix materials. However, real-world applications of NFRCs require some secondary operations in order to complete the assembly of the components or parts. Very few researchers have discussed issues related to the machinability of these NFRCs. In this paper, for the first time, a comprehensive literature review on machining of NFRCs is discussed with focus on drilling operation. The paper also reviews the studies on milling and turning of NFRCs. The distinct feature of this review is that it identifies the factors that affect the quality of the machined feature and provides general recommendations for the selection of process parameters so as to generate better quality holes during drilling. In addition, the review also discusses the challenges that hinder machining of NFRCs which is a significant contribution to the field of NFRCs.

Optimization of surface roughness and cutting temperature in high-pressure coolant-assisted hard turning using Taguchi method

Abstract: In this article, the effects of material hardness and high-pressure coolant jet over dry machining are evaluated in respect of surface roughness and cutting temperature using Taguchi L36 orthogonal array. The experimental data was analyzed using empirical cumulative distribution function and box plot with respect to material hardness and machining environment. Afterward, optimization of the quality responses is performed using signal-to-noise ratio. As part of Taguchi optimization, the “smaller is better” was adopted as optimization principle; the design of experiment was used for parameters orientation, and the analysis of variance was used for determining the effects of control factors. For the present experimental studies, three types of hardened steels (40 HRC, 48 HRC, and 56 HRC) were turned by coated carbide insert at industrial speed–feed combinations under both dry and high-pressure coolant jet. Depth of cut, being a less significant parameter, was kept fixed. The high-pressure coolant jet was found successful in reducing cutting temperature, surface roughness, and tool wear. The statistical analysis showed that work material hardness is the most significant factor for both cutting temperature and surface roughness. However, for surface roughness, other variables exerted somewhat similar contribution, while in determining the cutting temperature, the environment demonstrated crucial role. The confirmation tests showed 15.85 and 0.28 % error in predicting surface roughness and cutting temperature, respectively.

Distortion caused by residual stresses in machining aeronautical aluminum alloy parts: recent advances

Abstract: The distortion in machining aeronautical aluminum alloy parts (AAAPs) is one of the serious challenges in the aviation industry, and the residual stresses produced in multimanufacturing steps are the main cause. In order to get a comprehensive understanding of the problems about residual stresses and distortion in machining AAAPs, the state-of-the-art in several aspects including the generation reasons of residual stresses, the factors influencing distortion during machining, the measurement methods of residual stresses, the prediction and controlling methods of distortion are summarized in this paper. The generation mechanism of the bulk residual stress inner materials and the machining-induced residual stresses, as well as the factors affecting two kinds of residual stresses are stated. Also, the influences of residual stresses and machining process conditions on distortion are analyzed. Furthermore, the common residual stress measurement methods and its application scope are summarized. Significantly, the differences, advantages, and disadvantages of various prediction methods are analyzed. The methods of controlling distortion before and after machining are summarized. Finally, the paper gives out further research on the distortion in machining AAAPs in aeronautical manufacturing.

Thermal analysis during turning of AZ31 magnesium alloy under dry and cryogenic conditions

Abstract: In this study, the effect of both cryogenic and dry machining of AZ31 magnesium alloy on temperature and surface roughness was examined. Cryogenic machining experiments were conducted by applying liquid nitrogen at the cutting zone. The cutting parameters (cutting speed, depth of cut, and feed rate) were varied, and their effect on the results was identified. It was found that the cryogenic machining was able to reduce the maximum temperature at the machined surface to about 60% as compared with dry machining. A finite element model was developed to predict the temperature distribution at the machined surface. The simulated results showed good agreement with the experimental data. After analyzing the temperature distribution, the model also suggested that the cryogenic-assisted machining removes heat at a faster rate as to that of the dry machining. An arithmetic model using the response surface method was also developed to predict the maximum temperature at the surface during cryogenic and dry machining. The analysis pointed out that the maximum temperature was greatly affected by the cutting speed followed by feed rate and depth of cut. Cryogenic machining leads to better surface finish with up to 56% reduction in surface roughness compared with dry machining.

Moth-flame optimization algorithm to determine optimal machining parameters in manufacturing processes

Abstract: In this research, a newly developed moth-flame optimization algorithm (MFO) is presented for solving optimization problems in manufacturing industry. A well-known milling optimization problem is solved to emphasize the effectiveness of the MFO in the optimization of manufacturing problems. In the optimization problem solved in this paper, the main aim is to maximize the profit rate for multi-tool milling operations considering difficult constraints. The results demonstrate that the MFO is an effective optimization method for the solution of manufacturing optimization problems.

Powder bed fusion processes: An overview

Abstract: Additive manufacturing is a manufacturing process in which functional parts can be made by adding materials without using special tooling, jigs or fixtures. It provides tremendous advantages compared with traditional subtractive manufacturing processes, such as shorter lead times, less waste, the ability to make more complex parts and a cost independent of complexity. Powder bed fusion processes in laser-based additive manufacturing have received significant attention in the research and development of advanced engineering materials because of their higher cooling rate and better surface finish compared with other additive manufacturing processes. This chapter summarizes the recent research in the laser-based powder bed fusion process. It covers the characteristics of the process and melt pool; microstructural features including texture, residual stress and defects; and characteristics of mechanical properties of metallic parts processed by the laser-based powder bed fusion process.

Advanced Machining Processes

Abstract: This chapter provides comprehensive knowledge regarding both well-established achievements in manufacturing and new trends in improving machining processes, taking into account physical, design and technological aspects. The background of machining advancements is outlined, including all components of the machining system and typical machining operations such as turning, milling and drilling and different construction materials. In particular, this short survey covers such machining techniques as high-speed machining/cutting (HSM/HSC), hard part machining, dry and near-dry machining (MQL), high-performance machining (HPM), multitasking/complete machining, and assisted and hybrid machining. In all these cases, the focus was directed towards the physical fundamentals, design of machine tools, cutting tools and selection of machining conditions. All machining techniques discussed are supported by new research works, original investigations and practical implementations. In particular, these six subchapters are supplemented by the present machining knowledge edited by the CIRP community and newly published reference books.

Current Trends of Additive Manufacturing in the Aerospace Industry

Abstract: Additive Manufacturing offers unmatched flexibility in terms of part geometry, material composition and lead-time. It is moving towards revolutionizing the aerospace manufacturing sector through production of highly complex, lightweight parts with reduced material waste. It can also be employed for repair of complex components such as engine blades/vanes, combustion chamber, etc. Complex geometry thin walled aircraft engine components and structures, difficulty in machining of materials are other main factors forcing aerospace sector to adopt the use of additive manufacturing technology. In this paper an attempt has been made to explore the additive manufacturing research and development activities in aerospace industry.