Re-thinking the maximum efficiency in machining when environmental stress is accounted for

The material processing industry has to deal with material and energy reduction targets, and such a need becomes more and more urgent if future energy and resource consumption predictions are considered. The optimization of machining operations has conventionally been performed by identifying a range of process parameters leading to the maximum efficiency, which has been defined on the basis of maximum productivity and minimum cost criteria. In this paper, aiming to the sustainable development of machining, the maximum process efficiency concept is revisited by including the metrics accounting for the environmental impact. Models for assessing the specific process time, cost, energy requirement and carbon dioxide emissions are detailed, and a trade-off multiple-target optimization solution is proposed. The methodology is applied to a case study, i.e., the turning of a Ti-6Al-4V alloy.