The Economic and Environmental Sustainability of Additive Manufacturing for Tooling: A Case Study on Using Laser Powder Bed Fusion for Making Injection Molding Tool Inserts

Abstract

Abstract Laser powder bed fusion (L-PBF) can make injection molding tools with conformal cooling channels that can reduce plastic part warpage and production cycle times. In this study, we define the design space in which L-PBF tools are economically and environmentally beneficial compared to traditional toolmaking methods. We develop mechanistic production cost, lead time, and cradle-to-grave life cycle assessment models of the cumulative energy demand (CED) and greenhouse gas (GHG) emissions associated with injection molding (IM) tool inserts made from tool steel using a Renishaw AM500Q L-PBF machine versus conventional 3-axis machining of equivalent beryllium copper (BeCu) inserts. These models are applied to a set of seven tool inserts used to make glass fiber reinforced plastic engine intake filter housings. The models are informed using insert build time and electrical power measurements on the L-PBF machine. Across all the inserts, using L-PBF was found to be slower, costlier, and more energy and emissions intensive than conventional mold making. However, benefits from reduced IM cycle times and plastic part rejection rates when using the L-PBF inserts can lead to whole life cycle improvements. We calculate how the breakeven plastic part production volumes (above which L-PBF inserts are faster, cheaper, and more environmentally benign over the life cycle) change for varying cycle time and part reject rate improvements. Assuming the L-PBF inserts result in 15% and 2.5% reductions in cycle time and part rejects respectively, then the breakeven production volumes are 60,000 parts for lead time, 4,000 parts for CED and GHG emissions, and greater than the likely mold lifespan (100,000 parts) for cost.