A framework for effective and clean conversion of machining waste into metal powder feedstock for additive manufacturing

Abstract

The dependence on conventional metal cutting technologies to satisfy consumer demands for more customised products and services is contributing to the generation of ever-increasing metallic waste in the form of machining chips (MCs). Metallic MCs are of high value if recycled by sustainable techniques. Conventional recycling by melting the MCs for industrious use is neither economical nor environment friendly. Thus, the advanced technologies for clean recycling of MCs for industrious use are the need of the hour. In this paper, consideration is given to the role of one such advanced recycling technology: ball milling (BM). The efficacy of BM for recycling MCs by converting them into chip powder (CP) is evaluated. The produced chip powder (CP) can be utilized as feedstock powder in various powder bed fusion (PBF) additive manufacturing processes like laser engineered net shaping (LENS) and electron beam melting (EBM) for the manufacturing of near-net shaped products. The consequences of adopting this novel recycling technology on industrial sustainability are not well understood and this exploratory study draws on publicly available data to provide insights into the impacts of BM on sustainability. Benefits of BM are found to exist which include promising results in obtaining 70–90% sphericity with the utilization of 20–30% less energy in comparison to conventional powder production techniques. As an immature technology, there are substantial challenges to these benefits being realised. This paper summarises these advantages, challenges, and discusses the implications of BM as sustainable recycling technology in terms of process parameters on the mechanical, physical, and morphological properties of the CP produced. In addition, a framework is presented which suggests the plausible methodology for recycling MCs into CP from the generation stage to the final utilization stage.