Sustainable Machining: Tool Life Criterion Based on Work Surface Quality

Abstract

Extending the use of a component without compromising its intended functionality is the neatest approach to enhance sustainability. From this perspective, limiting the working life of a cutting tool based merely on the blunting of its cutting edge to a specific value is highly questionable. The very question that serves as the motivation for this work is, “why should tool life criterion be based on the shape of the tool when all that matters for business is the quality of the part being machined?”. This work puts forward a tool life criterion based on the surface quality of the machined part. The proof of the concept is provided by a series of face-turning experiments performed on a commonly used alloy steel using the following cutting inserts in dry conditions: (1) uncoated carbide; (2) coated carbide; and (3) cubic boron nitride (CBN). It is found that different combinations of tooling and cutting parameters lead to entirely different values of surface roughness at the same level of flank wear, thus raising the possibility of extending the working life of the tools. Overall, the CBN inserts yielded the longest tool life values, especially at high levels of cutting speed. Being more economical in respect of acquisition cost than the CBN inserts and more effective than the uncoated carbide inserts regarding tool life, the coated carbide inserts came out as the most sustainable tooling option. Finally, it is concluded that a tool life criterion based on work surface roughness can yield longer tool life values and make the machining process more sustainable. For the experimental work reported herein, the surface-quality based tool life criterion yielded on average 23% longer tool life. The presented work is novel as it presents a new approach to extend the working life of cutting tools without compromising the other sustainability measures. The outcomes are expected to find applicability in all sectors of the metal cutting industry, which are striving for elongations in tool life and improvements in work surface quality.