Hybrid material extrusion 3D printing to strengthen interlayer adhesion through hot rolling

Amongst the different categories of additive manufacturing technologies, Fused Deposition Modeling (FDM) has become the most widely adopted owing to its accessibility, low complexity, and high flexibility. Although notable advancements in FDM have been achieved, weak mechanical properties remain a barrier to produce functional components. This limitation is a result of weak interlayer bonding inherent to the layer-by-layer fabrication since the lower layers rapidly cool below glass transition temperature before the next one is deposited. This work presents the installation of a heated roller to compress each layer homogeneously onto the previous one after it has been printed to increase interlayer adhesion. Thermo-mechanical methods are proposed since pressure forces can be used to increase filament surface contact, and heat can be used to enable longer diffusion and neck growth. In this work, the effects of roller pressure, speed, and temperature on bonding strength are analysed through tensile testing, three-point bending, and differential scanning calorimetry. In summary, tensile testing shows a maximum ultimate tensile stress increase of 38.8%, a maximum tensile modulus increase of 19.4%, and a maximum tensile strain increase of 359.6%. Flexural analysis shows a maximum increase in ultimate flexural stress of 13.5%, a maximum increase in flexural modulus of 20.76%, and a maximum increase in flexural strain of 11.9%. Differential scanning calorimetry shows an increase in crystallinity of tested samples from 2.7% to 8.6% Computer tomography scanning indicates a large reduction in porosity and improvement in geometric accuracy. Therefore, this work proposes an inexpensive solution that targets the process of interlayer bond formation to increase the mechanical properties of FDM 3D printed components.