We have described basic structure-property-processing relationships that enable us to deliver a new generation of inexpensive 3D printable parts with robust thermomechanical properties which are first thermoplastically processed and subsequently covalently crosslinked. We focused on shape memory systems with glass transitions useable for biomedical applications, but believe this paradigm can be extended to a host of other systems that do not necessarily exhibit shape memory properties. We demonstrated a 1.7x increase in toughness relative to the non-crosslinked control for PLA sensitized with 10 wt% TAIC and irradiated at 60 oC which was 3D printed in the horizontal orientation. This increase in toughness came from an increase in both ultimate tensile strength and strain capacity and led to a dramatic reduction in anisotropy for the 3D printed parts. Furthermore, we demonstrated temperature windows at which to conduct the radiation crosslinking relative to Tg to balance kinetics with free radical generation and promote higher degrees of crosslinking. We know of no previous inquiry which studies the radiation crosslinking temperature relative to Tg for shape memory polymers, let alone for 3D printed systems. We have demonstrated a new paradigm for FFF 3D printing which has potential uses for medical devices, dental devices, oil and gas applications, defense applications and as-of-yet unknown uses as 3D printing continues to pervade though everyday society.