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In many applications in the metalworking industries, mass production of parts with holes possessing critical finish requirements for precision assembly operations demands tolerances in the working range of IT7 to IT5. However, this may not be achieved with regular twist drills, and further finishing processes such as reaming is normally required. To perform reaming, the workpiece needs to be previously drilled, so that two different cutting tools are needed and twice as much time is needed to machine compared with workpieces that need to be drilled, which in turn affects productivity and competitiveness. Therefore, any investment in the production of tools and techniques aiming to reduce the machining time of close tolerance holes, and lower tool wear rates and at a lower cost, will receive special attention from the machining sector. In this context, this paper presents technical and economic analyses of two manufacturing systems in drilling (drilling specially designed drill and regular drill with reamers) of compacted graphite iron (CGI) workpieces. The technical analysis was based on the tool wear mechanism, hole quality, and machining time, whereas the economic analysis was on total machining cost for use of specially designed drill and regular drills followed by reamers. Results showed lower wear on the specially designed drills compared with reamers. Also, the finish and dimensional deviations were similar to those obtained with reamers. Up to 40% of reduction in the machining time was achieved by using the specially designed drill, which resulted in a 57% reduction of the total cost. [ABSTRACT FROM AUTHOR]

Large quantities of coolant–lubricants are still widely used in the metal working industry, generating high consumption and discard costs and impacting the environment. This paper presents the evaluation of the performances of the various machining environments (dry, conventional wet and MQL technique) applied in hard turning of the AISI 4140 high-strength low alloy steel with coated mixed ceramic (CC6050) in terms of surface roughness, cutting force components, and tool wear. For this purpose, a number of machining experiments based on statistical four-factor (cutting speed, feed rate, depth of cut, and cutting radius) and hybrid-level factorial experiment designs uncompleted with a statistical analysis of variance were performed. The results indicate that the resulting cutting force obtained with the MQL machining process significantly improved when compared with other machining processes. For example: FRMQL ≈ 1.08 FRdry and FRwet ≈ 1.37 FRdry. Then, the RSM was utilized to define the optimal machining parameters. Finally, the ranges for best cutting conditions are proposed for serial industrial production. [ABSTRACT FROM AUTHOR]

It is possible to create value with less environmental impact through the adoption of Lean and Green manufacturing concepts and tools. This paper proposes a Lean-Green model based on the application of the Single Minute Exchange of Die (SMED) combined with Carbon Footprint (CF) to analyze eco-efficiency of a machining center in a case study in Brazil. The novelty of this paper was the proposal of a Lean-Green model based on ecoefficiency indicators to measure performance of production systems toward a cleaner production. The developed Lean-Green model should be used by companies with low-capacity of production due to restrictions of machine availability. The case study was organized in five different scenarios by varying machine tools, workers and workpieces. First, the SMED tool was applied in the setup activities and gains of reduced idle times were up to 88%. CF results were reduced up to 81% after applying the SMED tool on each scenario. Lastly, an eco-efficiency set of indicators were used to combine results of SMED and CF, and results of eco-efficiency were 3% higher even with higher CF values after converting setup saved time into productive time. To achieve such results simple improvements were performed in the machining center, through the standardization of work and the study of time and methods for setup activities, showing that the proposed Lean-Green model could be also adopted by other companies to create value with less impact. [ABSTRACT FROM AUTHOR]

In the beginning, metalworking fluids consisted of simple oils applied with brushes to lubricate and cool the machine tool. As cutting operations became more severe, metalworking fluid formulation became more complex. There are now several types of metalworking fluids in the market and the most common can be broadly categorized as cutting oils or water-miscible fluids. In this paper, attention is focused on recent research work on formulation and application of vegetable oil-based metalworking fluids in turning process. In addition, the performances of various vegetable oil-based metalworking fluids based on some process parameters such as thrust force, surface roughness, temperature developed at the tool chip interface, and tool wear during turning process using different tool materials were highlighted. [ABSTRACT FROM AUTHOR]

In the modern metalworking industry, production moulds often have complex geometry, with undercut regions, small corner radii, sharp edges, deep cavities, or large cores. Conventional manufacturing process chains to machine these complex features are often lengthy and inefficient due to multiple steps. This article presents current results obtained through industry projects and experimental work using 5-axis high-speed machining with high-end CAD/CAM systems to improve process efficiency. Cost optimisation and lead time shortening can be clearly shown. This is of particular importance for South African manufacturing companies, where multi-axis HSC technology - although not totally unknown - is significantly under-used. [ABSTRACT FROM AUTHOR]

This paper analyses the relationship between the cutting forces and length, according to experimental results obtained in lights alloys, in particular UNS A97050-T7, UNS A92024-T3, during the dry drilling. The tests have been performed with several cutting speed, 83 m/min, 60 m/min and 50 m/min. Box-Cox transformations have allowed finding a fitted model and determining a significant relationship between maximum cutting forces, for each hole, and cutting length. Thus, it is possible to establish prediction limits for new observations of cutting forces, at 95% confidence level. [ABSTRACT FROM AUTHOR]

Aerosol mapping was used to assess particle number and mass concentration in an engine machining and assembly facility in the winter and spring. Number and mass concentration maps were constructed from data collected with two mobile sampling carts, each equipped with a condensation particle counter (10 nm < diameter < 1 μm) and an optical particle counter (300 nm < diameter < 20 μm). Number concentrations inside the facility ranged from 15 to 150 times greater than that outside the facility and were highly dependent on season. The greatest number concentration (>1 000 000 particles cm−3) occurred in winter in an area where mass concentration was low (<0.10 mg m−3). The increased number of particles was attributed to the exhaust of direct-fire, natural-gas burners used to heat the supply air. The greatest mass concentrations were found around metalworking operations that were poorly enclosed. The larger particles that dominated particle mass in this area were accompanied by ultrafine particles, probably generated through evaporation and subsequent condensation of metalworking fluid components. Repeat mapping events demonstrated that these ultrafine particles persist in workplace air over long time periods. [ABSTRACT FROM AUTHOR]

The utilization of cutting fluids in metalworking industries causes health issues and environmental impacts. Owing to eco-friendly apprehensions and rising regulations over pollution and contamination, the need for a greener approach is increasing to diminish the employment of cutting fluids and dwindle the ecological impact. Therefore, special attention should be focused on clean and sustainable machining processes. Foremost, the optimal setting for multiple response problems in the manufacturing sectors must be acknowledged to reduce energy consumption. Even though machining industries established mist lubrication with vegetable oil and cryogenics as a substitute for mineral oils-based flooding, its meager lubrication and cooling property at elevated speed lead to a hunt for a new hybrid approach that offers adequate cooling/lubrication (C/L). Moreover, as of now, no information concerning the effects of hybrid cooling on milling of Nimonic-80A is existing. In this holistic investigation, machining of Nimonic-80A under hybrid C/L was compared with other cooling strategies (flood, MQL, and cryogenic) to determine the viability of employing cryogenics and hybrid cooling method. Complex Proportional Assessment (COPRAS) technique was applied to select the optimum cutting conditions to get the ideal surface trait. Besides improving the surface quality, the hybrid condition is treated as a trendsetter which is in legitimate agreement with the latest global swing for sustainable means of production. The optimization result indicated that machining at a cutting speed of 60 m/min and a feed rate of 0.04 mm/rev under the hybrid cooling strategy provides the optimal value, that controls the energy requirement. Pugh matrix method has been deployed to establish the sustainability assessment among the distinct cooling conditions. The research verdict illustrates the suitability of the hybrid cooling strategy and explains the process of going green. [ABSTRACT FROM AUTHOR]