“It wasn’t just that they showed us how to use the machine, they pulled together the whole ecosystem needed to make it successful,” and functionality of that machine,’ said Austin Schmidt, co-founder of Additive Engineering Solutions. That system has helped large-format polymer 3D printing transition from a lab curiosity into a market force that is changing the face of manufacturing as a whole. It was incubated at the Department of Energy’s Manufacturing Demonstration Facility at Oak Ridge National Laboratory.
The spark came in 2014 when ORNL and Cincinnati Incorporated publicly demonstrated their Big Area Additive Manufacturing BAAM system by 3D printing a car live on stage at the International Manufacturing Technology Show. Schmidt was at that time an engineer for Caterpillar and recognized more than just a demonstration: he recognized the power to create very large polymeric parts on a scalable basis. His own research team’s subsequent MDF project-a 2,000-pound bulldozer frame mock-up-demonstrated value for assembly verification, but the research-focused mission of MDF is not production. It is into this need gap for AES-the need for large-format prints while no such company provided the printing service-that AES has established its foothold.
The challenge was getting a BAAM printer. Cincinnati’s BAAM, scaled down from their high-speed laser cutters, replaced the laser head with a polymer extruder and included the “Slicer” software from ORNL. Slicer translates CAD files into layered tool paths that control the X-Y motion of the gantry and the Z-axis movements of the build table. For AES, mastery of Slicer meant more than running jobs; it was actually crucial in their work because they typically worked at sizes that could take tens of hours and hundreds of kilograms of material for a single component.
Large-format polymer extrusion presents special thermal challenges. “Goldilocks” conditions-with layers needing to be hot enough to merge but not so hot that they distort-are particularly critical on large-scale prints. Too slow nozzle movements across large-scale prints cools down the lower-layer material before its return, causing delamination. If the temperature is too high, the print will sag. The engineering team at AES countered these thermal challenges by angling the nozzle to 45 degrees, cutting down path lengths and thereby overcoming thermal time delay. This opened up new design spaces, like enabling bowl shapes that hitherto remained in theoretical states but introduced challenges in keeping away from probable collisions of print and bed, and geometries brought up enhanced functionalities of slicers.
The BAAM printer itself is an example of scaled-up extrusion engineering. In earlier models, printing took place at rates of 10 pounds per hour, but ORNL’s modification of the screw extruder enabled speeds of 40 pounds per hour, later scaled up to 100 pounds per hour with optimized pellet feed. Pellet extrusion not only allows for increased speeds but also reduces materials costs, since pellets from industrial thermoplastic materials cost only pennies per cubic inch compared with filament.
This also allows for composite materials like carbon-fiber reinforced polymers, which ORNL demonstrated eliminated issues with internal stress within large-scale printed parts. The optimization of tool paths is equally important. In large-format sizer printers, a balance between deposition rate, bead size, and path length has to be maintained to avoid thermal cycles. In a BAAM process, because of the high-speed motion ability of the gantry, reaching up to 200 inches per second, extrusion control should also be considered to avoid over- or under-deposition of materials.
Example reference designs are provided by the Sizer group at ORNL to optimize path planning and preserve bead overlaps, which results in better interlayer adhesion and surface finish without significant delays. Being in a monthly partnership with ORNL places AES among the leaders in such advances. Adding four out of only fifteen BAAM 3D printers in the world makes it the natural choice for the aerospace, defense, and construction sectors. In the defense applications, large-format polymer 3D printing can enable oversized parts to be made directly in the country by mirroring the use of expeditionary 3D printers by the military.
Nozzle technology continues to advance as a front-tier area. Some ideas out of lab research involving multimaterial extrusion, like coextrusion dies-which can allow interfilament bonding-or static mixers, which can make microlayered composites-may find applications on the scale that the BAAM system requires, providing varied properties for very large objects. Furthering the mission statement put forth by AES would be to print large, yes, but also better, faster, and more functional.
AES is a prime example of how a lab discovery becomes a staple in the factory, especially upon entrance into a new factory capacity with a market that is finally mature enough to realize the potential of this technology. The shift from MDF’s unique lab prints to the current ubiquitous large format AM market also speaks to the technological prowess entailed in scaling additive manufacturing from a lab curiosity into a genuine production process.
