Annealing of Fused Filament Fabricated Nylon 6 with Elevated Isostatic Pressure

Fused filament fabrication (FFF) is the most common form of 3D-printing used today. It combines ease-of-use with broad material options that allow for a wide spectrum of applications. Parts made this way are still considered only prototypes due to their relatively weak strength as compared to traditional manufacturing methods. Two factors leading to a decrease in strength are the interior voids and poor bonding roads. A chamber was created to implement pressurized annealing cycles on nylon 6 co-polymer parts to decrease interior voids and increase road bonding. A designed experiment was used to determine main effect parameter estimates for five factors: annealing time, temperature and pressure, cooling rate, and pressurized cooling. The results showed that with 800 psig of applied pressure during annealing, a significant closing of voids is possible. Annealing in a confined environment led to no noticeable part distortions. The increased density of the parts did not lead to increased yield strength in tension or bending and ultimately made the parts much more brittle. There was found to be a small increase in crystallinity and tensile modulus with small effect sizes. The impact energy absorption capability of the parts was also decreased. After the screening experiment, a validation study was then done to assess the annealing process in the absence of pressure and confining medium. These tests showed significant increase in part performance in both tension and flexion. These in air annealed parts did suffer from increased part distortion. These first look results of elevated isostatic pressure annealing indicate that pressurized annealing may be a viable post-processing technique for FFF parts. Great care needs to be taken when exposing parts to elevated pressure. The annealing process has been further verified to be an avenue to stronger FFF parts