Parametric optimization and modeling of the fused filament fabrication (FFF) manufacturing using recycled polyethylene terephthalate (PET) from water bottles

Most earlier studies on distributed recycling additive manufacturing (DRAM) have focused on using recycle-bots—waste plastic extruders—to produce raw materials for fused fluid fabrication (FFF). In the present study, an innovative recycling method designed explicitly for post-consumer water bottles was introduced and evaluated for its effectiveness in producing high-quality PET filament. The PET material was thoroughly characterized before and after filament production and following the 3D printing process. This approach successfully preserved the crystallinity of PET and prevented its thermal degradation. Key parameters, including infill density, printing speed, and layer thickness, were investigated using Taguchi’s method in conjunction with Grey Relational Analysis (GRA) to optimize the printing of recycled PET. This methodology aimed to maximize Young’s modulus and tensile strength while minimizing printing time and material usage. The results highlighted a trade-off between mechanical performance and printing efficiency. The best mechanical properties were achieved with a layer thickness of 0.1 mm and 100% infill density, yielding a tensile strength of 30 MPa and a Young’s modulus of 2311 MPa—values comparable to commercially available recycled PET and PLA filaments.