Jan 16, 2018 | By Benedict

Researchers from Harvard’s John A. Paulson School of Engineering and Applied Sciences have developed a 3D printing method that allows unprecedented control of short fibers embedded in polymer matrices. They call their method “rotational 3D printing.”

Rotational 3D printing can produce stronger parts with a high level of damage tolerance

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.

Jennifer A. Lewis acted as senior researcher on the 3D printing study

“Being able to locally control fiber orientation within engineered composites has been a grand challenge,” said Lewis, who thinks the new 3D printing process takes researchers a step closer to replicating the kind of balanced, effective structures found in nature: wood, bone, teeth, etc. “We can now pattern materials in a hierarchical manner, akin to the way that nature builds.”

This nature-inspired 3D printing process can be used to achieve “optimal or near-optimal” fiber arrangements in every area of a 3D printed part, which means higher strength and stiffness using less material. Moreover, the researchers think their process is more effective than using magnetic or electric fields to orient fibers, instead controlling the flow of the 3D printing ink directly.

Perhaps most interestingly from an additive manufacturing perspective, the SEAS researchers say that rotational 3D printing is not tied exclusively to any form of material deposition. That means existing 3D printing processes like FDM, direct ink writing, and even large-scale thermoplastic additive manufacturing could be augmented with rotating nozzles to create stronger, more damage-resistant parts.

The new technique also lets users print engineered materials that can be spatially programmed to achieve “specific performance goals.” Locally optimizing the orientation of fibers can, for example, increase the damage tolerance at critical locations of the part—areas that are most likely to undergo high levels of stress in their specified end-use application.

Jordan Raney, one of the researchers involved in the project and now Assistant Professor of Mechanical Engineering and Applied Mechanics at the University of Pennsylvania, thinks this localization is one of the most important aspects to rotational 3D printing. “One of the exciting things about this work is that it offers a new avenue to produce complex microstructures, and to controllably vary the microstructure from region to region," Raney said. "More control over structure means more control over the resulting properties.”

A research paper documenting the findings has been published in the journal PNAS. Other contributors include Brett Compton, now Assistant Professor in Mechanical Engineering at the University of Tennessee, Knoxville, and visiting PhD student Jochen Mueller from ETH Zurich.

 

 

Posted in 3D Printing Application

 

 

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DaveT wrote at 1/18/2018 2:34:02 AM:

You used space for two graphics. Neither one gave any insight into what the process does nor why it is good.



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