The energy requirements and environmental impacts of sheet metal forming: An analysis of five forming processes

Abstract Industrial emissions must be dramatically reduced to avoid the potentially dangerous effects of climate change. In order to contribute to the necessary cuts, this article focuses on the energy and material efficiency of sheet metal forming. The processes considered include traditional methods, such as drawing and stretch forming, and newer technologies developed in recent decades such as hydroforming (fluid cell forming), superplastic forming, and incremental sheet forming. In this analysis, we conduct case studies on forming processes at leading US car and aerospace manufacturers. The case studies include electrical power measurements on the forming machines and also consider the impacts of making the dies, sheet metal, and lubricant. Cradle-to-gate energy demands and environmental impacts are modeled in SimaPro using data based on ecoinvent 3.1 database values. The results show that idling consumes significant electricity; however, other than for incremental forming, the impacts of press electricity are small compared to the impacts of making the sheet metal. The case studies inform generalized models for each process that allow per part impacts to be estimated based only on final part material, size (surface area, thickness, and depth), and the number of parts produced over the die-set lifespan. The models are used to investigate the potential to reduce cradle-to-gate energy requirements by using incremental forming instead of drawing to form parts. It is found that there are significant potential savings for small production runs, consistent with part development/prototyping. However, these savings vary depending on the part size and the relative buy-to-fly ratio (material yield) of the two processes. The results of this study highlight that for small production numbers over the die lifespan the impacts of die-making are important. However, as production numbers increase above one hundred parts per die-set, the impacts of making the sheet metal become dominant. It is therefore concluded that researchers interested in reducing the environmental impacts of sheet metal forming concentrate on innovations that would reduce sheet metal blanking and post-forming trimming losses.