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

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 similar to 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.