The state of a cutting tool is an important factor in any metal cutting process as additional costs in terms of scrapped components, machine tool breakage and unscheduled downtime result from worn tool usage. Several methods to develop monitoring devices for observing the wear levels on the cutting tool on-line while engaged in cutting have been attempted. This paper presents a review of some of the methods that have been employed in tool condition monitoring. Particular attention is paid to the manner in which sensor signals from the cutting process have been harnessed and used in the development of tool condition monitoring systems (TCMSs).

Sensor signals for tool-wear monitoring in metal cutting operations—a review of methods

Nickel-based super alloys are gaining more significance, now-a-days, with extensive applications in aerospace, marine, nuclear reactor and chemical industries. Several characteristics including superior mechanical and chemical properties at elevated temperature, high toughness and ductility, high melting point, excellent resistance to corrosion, thermal shocks, thermal fatigue and erosion are primarily responsible for wide domain of application. Nevertheless, machined surface integrity of nickel-based super alloys is a critical aspect which influences functional performance including fatigue life of the component. This review paper presents state-of-the-art on various surface integrity characteristics during machining of nickel-based super alloys. Influence of various cutting parameters, cutting environment, coating, wear and edge geometry of cutting tools on different features of surface integrity has been critically explained. These characteristics encompass surface roughness, defects (surface cavities, metal debris, plucking, smeared material, redeposited material, cracked carbide particles, feed marks, grooves and laps), metallurgical aspects in the form of surface and sub-surface microstructure phase transformation, dynamic recrystallisation and grain refinement and mechanical characteristics such as work hardening and residual stress. Microstructural modification of deformed layer, profile of residual stresses and their influence on fatigue durability have been given significant emphasis. Future research endeavour might focus on development of new grades, advanced processing techniques of the same to ensure their superior stability of microstructure and thermo-mechanical properties along with advanced manufacturing processes like additive manufacturing to achieve highest level of fatigue durability of safety critical components while maintaining acceptable surface integrity and productivity.

State-of-the-art in surface integrity in machining of nickel-based super alloys

Sustainable machining: selection of optimum turning conditions based on minimum energy considerations

This paper presents an overview of the recent advances in high performance cutting of aerospace alloys and composite currently used in aeroengine and aerostructure applications. Progress in cutting tool development and its effect on tool wear and surface integrity characteristics of difficult to machine materials such as nickel based alloys, titanium and composites is presented. Further, advances in cutting technologies are discussed, focusing on the role of hybrid machining processes and cooling strategies (MQL, high pressure coolant, cryogenic) on machining performance. Finally, industrial perspectives are provided in the context of machining specific components where future challenges are discussed.

High performance cutting of advanced aerospace alloys and composite materials

In addition to the steps taken to ensure optimal efficiency in industry, significant effort has been directed towards the green and sustainable manufacturing practices. In this paper, we review conventional and state-of-the-art manufacturing technologies to provide insight into energy consumption at the processing level. In the review, collected energy data were summarized for three manufacturing categories: conventional bulk-forming, subtractive, and additive manufacturing (AM) processes. Additive processes, in particular, are strongly emphasized in the Advanced Manufacturing Initiatives proposed recently by the United States government. Currently, the specific energy consumption (SEC) of additive processes is estimated to be ~100-fold higher than that of conventional bulk-forming processes, with subtractive processes showing intermediate values that varied over a wide range in terms of scale. Although SEC may vary with respect to the details, in general, the research showed a negative correlation with respect to the reciprocal logarithmic form of the productivity. In addition to the literature review presented, we performed case studies for the three manufacturing processes, to provide practical examples of energy consumption. Additionally, our results indicated that AM processes may require more extensive evaluation; i.e., an assessment of the entire manufacturing cycle, for more accurate prediction of the subsequent environmental impact.

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A Comparison of Energy Consumption in Bulk Forming, Subtractive, and Additive Processes: Review and Case Study

In precision hard turning, a remaining problem is to minimise tool wear to maintain the accuracy of geometry and surface finish. Tool wear not only directly reduces the part geometry accuracy but also increases cutting forces drastically. The change in the cutting forces also causes instability in the tool motion, which results in more inaccuracy. PCBN cutting tools are often used in hard turning. However, they are still relatively expensive compared to ordinary carbide cutting tools. In order to attain sufficiently high production rates at minimum cost, increase of knowledge on cutting tool geometry is necessary. This article presents a study of the effect of chamfer angle on tool wear of PCBN cutting tool in the super finishing hard turning. The correlation between cutting force, tool wear and tool life were investigated. The optimised chamfer angle for PCBN cutting tool is suggested. Finally, the distribution of stresses and maximum principal stress working on the tool edge were calculated with the use of finite element method.

Effect of chamfer angle on wear of PCBN cutting tool

An investigation of surface damage in the high speed turning of Inconel 718 with use of whisker reinforced ceramic tools

Inconel 718 is known to be among the most difficult-to-machine materials due to its special properties which cause the short tool life and severe surface damages. The properties, which are responsible for poor machinability, include rapid work hardening during machining; tendency to weld with the tool material at high temperature generated during machining; the tendency to form a built-up edge during machining; and the presence of hard carbides, such as titanium carbide and niobium carbide, in their microstructure. Conventional method of machining Inconel 718 with cemented carbide tool restricts the cutting speed to a maximum 30 m/min due to the lower hot hardness of carbide tool, high temperature strength and low thermal conductivity of Inconel 718. The introduction of new coated carbide tools has increased cutting speed to 100 m/min; nevertheless, the time required to machine this alloy is still considerably high. High speed machining using advanced tool material, such as CBN, is one possible alternative for improving the productivity of this material due to its higher hot hardness in comparison with carbide tool. This paper specifically deals with surface quality generated under high speed finishing turning conditions on age-hardened Inconel 718 with focus on surface roughness, metallographic analysis of surface layer and surface damages produced by machining. Both coated and uncoated CBN tools were used in the tests, and a comparison between surfaces generated by both tools was also discussed.

Study of surface quality in high speed turning of Inconel 718 with uncoated and coated CBN tools

Performance of cutting tool in hard turning is significantly influenced by its microgeometry, such as edge radius. This study presents an experimental exploration to understand the effect of cutting edge radius on machining performance in terms of surface roughness and tool wear. The cutting tools (CBN) with three groups of nominal edge radius, 20, 30, and 40 μm, were used in the study. The cutting edge radii were characterized with an Alicona optical microscope, and variation of the edge radius was evaluated in this study. The machining tests were then conducted to experimentally assess the effect of cutting edge radius on surface quality and tool wear under different machining conditions. Three-level and two-factor experiments were designed in the test. The results in this study suggest that there is noticeable variation in the edge radius on a cutting tool with a certain nominal value of edge radius. The variations tend to be smaller with increase of the nominal value of edge radius. Besides, the results can be drawn that edge radii have a significant influence on surface roughness and tool wear. Considering all factors, the cutting tool with nominal edge radius of 30 μm demonstrate better machining performance among three groups of cutting tool in hard turning of AISI52100 steel.

/pdf/effect-of-cutting-edge-radius-on-surface-roughness-and-tool-3wie6v1ifx.pdf

Effect of cutting edge radius on surface roughness and tool wear in hard turning of AISI 52100 steel

https://lucris.lub.lu.se/ws/files/108798297/4697943.pdf

Jan-Eric Ståhl

Papers

Effect of chamfer angle on wear of PCBN cutting tool

An investigation of surface damage in the high speed turning of Inconel 718 with use of whisker reinforced ceramic tools

Study of surface quality in high speed turning of Inconel 718 with uncoated and coated CBN tools

Effect of cutting edge radius on surface roughness and tool wear in hard turning of AISI 52100 steel

Effect of Cutting Conditions on Machinability of Superalloy Inconel 718 During High Speed Turning with Coated and Uncoated PCBN Tools