Combining Design for Compliant and Multi-material AM for Conceiving More Sustainable Products

Compliant mechanisms are systems that, using a single body, are able to perform functions typical of a traditional assembly with hinges, bars, and connecting parts. Since many structures in nature are designed in a logic of compliant mechanisms, it is reasonable to assume the enormous advantages, also in terms of sustainability, of this way of designing in engineering. To date, one of the main barriers to their diffusion is the lack of tools that can suggest the right topologies to the designer (pointers to geometrical effects), but also easy tools for their appropriate dimensioning and simulation. In contrast, additive manufacturing, thanks to its high compatibility with complex shapes and the recent ability to print multi-material parts, is bringing them back into the spotlight. The aim of this paper is to show the potential of DfC—Design for Compliant for the conception of more sustainable products, by presenting an exemplary case in which a comparison was made between the environmental impact of a traditional multi-part door lock made using standard manufacturing processes and a compliant system capable of replacing the former. To achieve even better results, the DfC-inspired concept was printed by multi-material additive manufacturing, using a combination of two different polymeric materials with very different Young’s modulus to simulate different local behavior, both rigid and elastic. This substitution resulted in a reduction of CO2 equivalent impact around 50%.