No abstract

The effect of cutting tool geometry has long been an issue in understanding mechanics of turning. Tool geometry has significant influence on chip formation, heat generation, tool wear, surface finish and surface integrity during turning. This article presents a survey on variation in tool geometry i.e. tool nose radius, rake angle, groove on the rake face, variable edge geometry, wiper geometry and curvilinear edge tools and their effect on tool wear, surface roughness and surface integrity of the machined surface. Further modeling and simulation approaches on tool geometry including one approach developed in a recent study, on variable micro-geometry tools, is discussed in brief.

Steel parts that carry critical loads in everything from automotive drive trains and jet engines to industrial bearings and metal-forming machinery are normally produced by a series of processes, including time-consuming and costly grinding and polishing operations. Due to the advent of super-hard materials such as polycrystalline cubic boron nitride (PCBN) cutting tools and improved machine tool designs, hard turning has become an attractive alternative to grinding for steel parts. The potential of hard turning to eliminate the costs associated with additional finishing processes in conventional machining is appealing to industry. The objective of this paper, is to survey the recent research progress in hard turning with CBN tools in regard of tool wear, surface issues and chip formation. A significant pool of CBN turning studies has been surveyed in an attempt to achieve better understanding of tool wear, chip formation, surface finish, white layer formation, micro-hardness variation and residual stress on the basis of varying CBN content, binder, tool edge geometry, cooling methods and cutting parameters. Further important modeling techniques based on finite element, soft computing and other mathematical approaches used in CBN turning are reviewed. In conclusion, a summary of the CBN turning and modeling techniques is outlined and the scope of future work is presented.

The present study is an attempt to model the tool wear and surface roughness, through response surface methodology (RSM) during hard turning of AISI-H11 steel with TiN-coated—mixed ceramic inserts. The effect of machining parameters — i.e. cutting speed, feed rate, depth of cut, and workpiece hardness — on the response factors, viz. flank wear and surface roughness, have been investigated by applying analysis of variance (ANOVA) and through factor interaction graphs in the RSM. The non-linear quadratic models best fit the experimental data points. The desirability function approach has been used for multiple response factors optimization. The confirmation experiments carried out to check the validity of developed models predicted response factors within 5 per cent error. The feed rate, depth of cut, and workpiece hardness are observed to have a statistically significant impact on the flank wear, whereas feed rate and workpiece hardness are the significant factors affecting the surface roughness. The tool wear was monitored with a toolmaker's microscope, and wear characterization of some of the representative inserts was carried out using scanning electron microscope/energy dispersive X-ray (SEM-EDX) analysis. The tool appears to be worn out by abrasion, notch wear, and chipping of the tool surface owing to rubbing and impingement of hard particles in the work material and also by adhesion wear.

The benefits of cutting fluids in machining are well known, but their use is accompanied by health and environment hazards. Moreover, strict environmental regulations make the manufacturers to switch over to dry turning, which is not feasible during machining of sticky material like stainless steel and Inconel etc. Therefore, the use of minimal quantities of lubricant (MQL) can be regarded as an alternative solution and a step towards green machining. In the present investigation an attempt has been made to explore the potential of MQL turning of stainless steel with coated carbide cutting tool. Turning under MQL conditions has shown superior results (in terms of flank wear and machined surface roughness) over wet and dry turning. Signal to noise (S/N) ratio as per Taguchi design revealed speed and MQL as significant parameters for minimizing flank wear and surface roughness, whereas feed can be set within range. The optimum combination of parameters are cutting speed (58 m/min), feed rate (0.06 mm/rev.) and MQL flow rate (100 mL/h) for flank wear and cutting speed (23 m/min), feed rate (0.07 mm/rev.) and MQL flow rate (150 mL/h) for surface roughness. Taguchi optimized conditions were validated through multiple response optimization using desirability function.