Impact of un-deformed chip thickness on specific energy in mechanical machining processes

Energy demand reduction is a grand challenge for manufacturing sustainability in order to reduce the escalating cost of energy and to cut down on the carbon footprint of manufacturing processes. The direct electrical energy requirements in manufacturing and machining in particular can be modelled from the basic energy required by the machine tool and the energy for actual material removal (tip energy). However, energy centric modelling of manufacturing processes is in its infancy and related material processing data is limited and of low integrity. It has often been assumed that the specific cutting energy is a constant value for particular workpiece materials. This paper is inspired by the mechanistic force modelling and the size effect phenomenon in machining. The aim of this work was to investigate the specific electrical energy demand in machining and model its relationship to thickness of material removed. To this end, specific energy evaluated in cutting tests was empirically modelled. This work is comprehensive in that it covers a wide range of un-deformed chip thickness as well as three workpiece materials. A new and fundamental understanding of the variation of specific energy with chip thickness is reported for the first time. This can be an evidence base for a generic model for the dependence of specific energy on un-deformed chip thickness. This information is vitally important to raise the integrity of energy labelling of machining processes and as a backbone to process optimisation in order to reduce electrical energy demand and promote manufacturing sustainability.