Multi-material fused filament fabrication: an expedited methodology to assess the affinity between different materials

The impact of 3D printing and how it is present in everyday life is unquestionable. Provided with almost total freedom of design and a vast list of materials, 3D printing has attracted enormous interest, being the fused filament fabrication (FFF) technique one of the main drivers. Given the vast range of compatible materials, FFF potential is being further developed towards multi-material prints. Still, one of the main challenges in such multi-material print is to predict the affinity between different materials in advance. This paper explores an expedited method to evaluate if two different materials can work together. The method is based on polymer joining using a hot plate welding process. Different filament materials welded together are compared with hybrid parts printed by FFF with the same filaments. The results are benchmarked to find out if the performance under welding follows the same pattern as in 3D multi-material printing. Therefore, the present study encompasses different combinations of rigid (Polycarbonate, PC, and Polyamide, PA) and flexible (thermoplastic elastomers, NinjaFlex, FilaFlex, and TPC 45) materials and also pairs of each one of these materials. The results showed that there is a loss of performance of the single material welded or multi-material printed samples when compared to their corresponding monolithic counterparts. Moreover, the results also showed a similar performance profile for multi-material samples obtained through welding and 3D printing. The technique here proposed proved to be an expedited method to assess material's relative affinity, a critical feature to guarantee their adequacy for use in FFF multi-material printing.