Fused Filament Fabrication (FFF), part of the Material Extrusion (ME) ISO/ASTM 52900 Additive Manufacturing (AM) family, is widely adopted in industry and academia due to its accessibility. However, inherent weaknesses in FFF parts, particularly inter-layer adhesion and void formation, limit structural performance. While previous research has explored nozzle material selection and flow optimization, nozzle geometry remains largely limited to circular, elliptical, square, and occasionally star or hexagonal cross-sections. Circular nozzles produce flattened oval beads that create inter-layer voids where adjacent beads fail to achieve full cross-sectional contact. Square and rectangular nozzles have demonstrated improved tensile strength and impact resistance by reducing void content and increasing inter-filament bond area. However, these geometries introduce challenges: over-extrusion at sharp corners due to fixed nozzle orientation, and parts still fracture along layer lines despite improved contact area. This work introduces a tear-drop puzzle-piece nozzle geometry with rotational control to create programmed interlocking features between extrusion passes and subsequent layers. Unlike static geometries, the tear-drop profile is designed to mechanically interlock when properly oriented, analogous to puzzle pieces fitting together. A custom rotating toolhead, mounted to a conventional FFF gantry system, adjusts nozzle orientation throughout the print to optimize interlocking at each toolpath segment. Mechanical performance is quantified through standardized testing: tensile specimens (ASTM D638) and impact specimens (ASTM D256) are printed and compared against baseline circular and square nozzle prints. Preliminary results demonstrate the feasibility of orientation-controlled interlocking extrusion. This approach extends beyond passive nozzle geometry by introducing programmable interlocking between layers, directly addressing FFF's fundamental weakness in inter-layer bonding.
Learning Objectives:
Upon completion, participants will be able to understand the impact of bead geometry on the final strength of a Material Extrusion part (specifically tensile sample).
Upon completion, participants will be able to understand the impact of nozzle shape on material flow through the hot end and on how closely CAD data can be printed.
Upon completion, participants will understand how to conduct standardized tensile (ASTM D638) and impact (ASTM D256) testing and analyze the mechanical performance results.
