Multi-material additive manufacturing via fused deposition modeling 3D printing: A systematic review on the material feeding mechanism

The rapid advancements in fused deposition modeling (FDM) 3D printing methods have unlocked new opportunities in multi-material additive manufacturing (AM). This technique offers a viable solution for creating high-performance, multi-functional graded materials, parts, and tooling. Despite the extensive efforts invested in exploring the potential of the FDM-type multi-material additive approach, there is a noticeable lack of discussion specifically centered around the material feeding mechanism of this extrusion-based 3D printing method. This work provides a systematic review on the current studies related to the multi-material FDM 3D printing. It is found that the interlayer adhesion quality of different feedstock materials is a first and foremost feature in determining the strength of the entire print. To this end, we particularly focus on analyzing the feeding system of multiple materials and the strategy for material alternation. From our analytical evaluations, it is noticed that the single-nozzle/multi-feed and multi-nozzle/multi-feed FDM printers present unique pros. and cons., respectively. Inspired by multi-material applications of direct ink writing extrusion-based 3D printing, we also suggest to choose a suitable method based on the material rheology and thermal properties of the constituent materials. This can be a chance to gain further benefits from the multi-material AM.