Effects of thermal process parameters on mechanical interlayer strength for additively manufactured Ultem 9085

The effects of the envelope temperature on the microstructure and mechanical strength of Ultem 9085 fused deposition modeling (FDM) components were studied. A customized build chamber was developed for a commercial 3D printer in order to control the envelope temperature during printing. Test specimens were printed in the vertical direction because their mechanical strength exhibited the greatest dependence on inter-layer adhesion and neck development. A delay was introduced between two layers in each specimen in order to create a weak region where the neck was not expected to fully develop. However, none of the specimens failed in this region. Mechanical testing revealed that neck growth was highly dependent on the envelope temperature, and the strength was shown to vary significantly ($>$20%) based on the envelope temperature. The variability of the mechanical strength also decreased as the envelope temperature increased. Thermal imaging revealed that the cooling rate of the specimens was consistent regardless of the envelope temperature. Fracture analysis confirmed that higher envelope temperatures improved the amount of neck growth and inter-layer adhesion in the specimens. This study showed that increasing the envelope temperature created parts with higher strengths and improved consistencies.