Disentanglement Effects on the Welding Behaviour of Polymer Melts during the Fused-Filament-Fabrication Method for Additive Manufacturing

摘要

Although 3D printing has the potential to transform manufacturing processes,the strength of printed parts often does not rival that oftraditionally-manufactured parts. The fused-filament fabrication methodinvolves melting a thermoplastic, followed by layer-by-layer extrusion of themolten viscoelastic material to fabricate a three-dimensional object. Thestrength of the welds between layers is controlled by interdiffusion andentanglement of the melt across the interface. However, diffusion slows down asthe printed layer cools towards the glass transition temperature. Diffusion isalso affected by high shear rates in the nozzle, which significantly deform anddisentangle the polymer microstructure prior to welding. In this paper, wemodel non-isothermal polymer relaxation, entanglement recovery, and diffusionprocesses that occur post-extrusion to investigate the effects that typicalprinting conditions and amorphous (non-crystalline) polymer rheology have onthe ultimate weld structure. Although we find the weld thickness to be of theorder of the polymer size, the structure of the weld is anisotropic andrelatively disentangled; reduced mechanical strength at the weld is attributedto this lower degree of entanglement.