In the search for supreme strength and damage tolerance in 3D printed parts, researchers can explore several avenues, each of which can affect the quality of a printed object. Finding the best and most appropriate 3D printing process is one understandably significant part, while selecting a strong yet printable material also plays a large role. The microstructure of a 3D printed object, whether it consists of tiny lattices, for example, is another area that can greatly affect the performance of a printed part.

For a group of researchers at Harvard’s John A. Paulson School of Engineering and Applied Sciences (SEAS), there’s a new variable to factor into consideration, one that could prove the difference between average and high-strength 3D printed parts made using epoxy composites. That new factor is fiber orientation, a variable that can be precisely controlled using the researchers’ newly developed “rotational 3D printing” technique.

In a study led by 3D printing extraordinaire Jennifer A. Lewis, the Hansjorg Wyss Professor of Biologically Inspired Engineering at Harvard SEAS and the brains behind 3D printer company Voxel8, the SEAS researchers have developed a new additive manufacturing process that provides unprecedented control of the arrangement of short fibers embedded in polymer matrices. The outcome of this is the ability to 3D print structural materials that are optimized for strength, stiffness, and damage tolerance.

The key to the exciting “rotational 3D printing” process is the precise choreography of the speed and rotation of a 3D printer nozzle, which allows the researchers to program the arrangement of embedded fibers in polymer matrices. The setup is deceptively simple: a rotational printhead system is equipped with a stepper motor, which serves to adjust the angular velocity of the rotating nozzle as the 3D printing ink is extruded onto the print bed and then onto successive layers.