The Al Davis Memorial Torch in Allegiant Stadium in Las Vegas is the world’s largest 3D-printed structure. The freestanding torch is made from 226 blocks of carbon fiber-reinforced polycarbonate thermoplastic printed by Dimensional Innovations (DI), a Kansas-based design, build and technology firm, on a Thermwood large scale additive manufacturing (LSAM) machine.
Built in homage to the former NFL coach and owner of the Las Vegas Raiders, the torch stands 93 feet tall. As a focal point of Allegiant Stadium, the torch not only needed to grab the attention of 65,000-plus fans who pack the stadium; it had to be structurally sound.
Experts at the Thermwood LSAM Research Laboratory in the Composites Manufacturing and Simulation Center (CMSC) at Purdue University created a digital twin of the structure and conducted a finite element analysis.
“The Thermwood machine is exceptionally good, but that doesn’t mean that every part will print successfully,” says Eduardo Barocio, director of additive manufacturing at CMSC. “We performed stress analysis to assess whether the torch would hold its own weight and could carry wind loads when the retractable side windows of the stadium are open.”
Backed by Purdue’s structural analysis, DI fabricated the 350-pound CFRTP blocks.
“We were printing two slightly oversized blocks in eight hours, letting them cool and then using LSAM’s five-axis capabilities to trim them back to final surfaces with precision,” says Brandon Wood, vice president of engineering and R&D at Dimensional Innovations. “LSAM allowed us to print in bosses [raised features that aid assembly and reinforce the structure] and support geometry and joinery details that we then used for fixturing, handling and install.”
After production, the blocks were sanded, coated and clad in 1,148 aerospace-grade aluminum panels.
“The torch was Dimensional Innovations’ complete creativity,” says Byron Pipes, executive director of CMSC. “We were a partner who walked along with them.”
A Partnership Between Industry and Academia
The Al Davis Memorial Torch serves as a high-profile example of the work done by the LSAM Research Laboratory, which opened as a collaboration between Thermwood Corp. and Purdue University in 2021.
“The lab provides a space where we can mutually learn from one another, improve 3D printing technology and collaborate on projects to further the field,” says Scott Vaal, program manager at Thermwood Corp. “Ultimately, our customers benefit because we are stretching the boundaries of large-scale additive manufacturing.”
The LSAM Research Laboratory is equipped with a LSAM 105 large-format, extrusion-based 3D printer and five-axis LSAM additive trimmer from Thermwood. The system can print and trim parts up to 5 x 10 x 4 feet, at print rates up to 200 pounds per hour. In addition, the lab also has state-of-the art simulation tools and diagnostic equipment.
“Before a customer prints, we use our simulation tools to predict whether the part is going to deform excessively,” says Barocio. “And, if so, we come up with different strategies – changes in print strategies, process conditions or materials – to overcome these problems.”
Purdue’s virtual twinning and simulation capabilities were instrumental in the development of the Al Davis Memorial Torch. Prior to the opening of the LSAM Research Lab, Thermwood brought the Composites Manufacturing and Simulation Center into the project.
Dimensional Innovations 3D printed 226 CFTRP blocks for the Al Davis Memorial Torch, such as those shown here, weighing 350 pounds each. Photo Credit: © Dimension Innovations
A 3D-printed mockup tool for an airplane engine air inlet duct. Photo Credit: Thermwood LSAM Research Laboratory at Purdue University
“We had begun testing the waters and came up with a viable way to print the torch, but then we had to move from a small test print to a 93-foot-tall structure needed to support itself,” says Vaal. “We didn’t have the manpower or expertise to perform the finite element analysis.”
Based on its simulations, Purdue recommended a change from acrylonitrile butadiene styrene (ABS), the initial material selected for the torch. “We switched to polycarbonate because it had all the extra strength and the flame retardance characteristics required,” says Vaal.
Targeting Autoclave Tools for Aerospace
The LSAM Research Laboratory isn’t merely a partnership between Thermwood and Purdue. It serves a broad market through its Composites Additive Manufacturing & Simulation Consortium (CAMS).
The industrial consortium comprises material suppliers such as Techmer PM, as well as OEMs, including Boeing, Lockheed Martin and Bell Helicopter. Members have access to educational materials, training, technical support and Additive3D™, a physics-based simulation workflow developed by Purdue with Dassault Systèmes.
Many CAMS members are in the aerospace industry, so staff at the LSAM Research Lab created a demonstration part to highlight capabilities of virtual twin simulations and additive manufacturing for autoclave tooling.
“If companies produce a part on a 3D-printed tool and the shape is wrong, they often blame the tool first,” says Barocio. “But shape changes come from both the tool and the part.”
The lab designed an LSAM demonstrator tool for mockup of an airplane engine air inlet duct. The part is prone to spring back, no matter what tooling is used, according to Barocio.
“We compensated for the anisotropic shape change of the tool and then conducted a full simulation considering the part and the tool and how their shapes change as the part is processed in an autoclave,” says Barocio.
FEA process simulation inputs included fiber orientation, boundary conditions and material models. The virtual twin demonstrator predicted residual stresses, deformation, crystallinity, interlayer bonding and more. It considered what happens if you add a heat treatment and when the part is machined to its final shape.
“Additive3D is the unifying element behind all of these predictions,” says Barocio. “We integrate everything into a fine element framework to predict the effect of manufacturing on the print process.”
Expanding into Energy Applications
Purdue is also working on applications in wind energy. Last fall, the U.S. Department of Energy awarded nearly $3 million to CMSC and industry partners Thermwood, TPI Composites, Dassault Systèmes, Dimensional Innovations and Techmer PM.
Equipment at the Thermwood LSAM Research Laboratory includes, from left, an LSAM 105, five-access CNC router and a Composites Additive Manufacturing Research Instrument (CAMRI) built by Purdue that can 3D print parts up to 20 x 20 x 20 inches. Photo Credit: Thermwood LSAM Research Laboratory at Purdue University
“Our goal is to leverage expertise developed on the torch project and apply it to modular large-scale additive tooling for wind blade manufacturing,” says Barocio.
Wind blades are typically fabricated using vacuum-assisted resin transfer molding, and much of the work relies on low-cost labor abroad. Barocio and his colleagues hope to develop a foundation for automated manufacturing of tooling for large-scale wind blades that can accommodate continuous changes in blade geometry and scale.
The program aims to:
- Enable direct printing of tooling using custom material formulations with enhanced chemical resistance that require no additional coatings.
- Develop a modular tooling design for wind blades longer than 80 meters, providing vacuum integrity and local heating.
- Account for shape compensation through predictive simulation of the additive manufacturing process and the mold performance.
The goal is to reduce the time required to manufacture and assemble wind blade tooling by at least 40%, enhance tool performance by at least 15% and lower the cost of manufacturing a wind blade tool by at least 35%. The team hopes this leads to more cost-efficient production and broader adoption of wind power in the U.S.
Future Focus on Hybrid Materials and AI
As the Thermwood LSAM Research Laboratory looks to the future, it’s expanding into new territory. For instance, the lab is pursuing methods that enable high-rate 3D printing of semi-structural composites.
“If you look at the landscape of 3D printing, on one end of the spectrum is large-scale additive, where you can print non-structural materials at hundreds of pounds per hour,” says Barocio. “On the other side you can print materials with structural properties at a fraction of a pound per hour for high-end products.”
There are niches for both, adds Barocio, but there’s a big gap between the two. The LSAM Research Lab is developing a printing process that uses a hybrid of continuous and discontinuous fibers to “potentially print at rates similar to a short fiber system, but not quite at the property levels of continuous fibers,” he says.
In addition, the lab wants to harness the power of machine learning and artificial intelligence to increase simulation speed, which often takes just as much time as 3D printing.
“We want to use physics-informed machine learning to accelerate simulation predictions and get data in a short time frame – hours or minutes,” says Barocio.
That would further the Thermwood LSAM Research Laboratory’s mission.
“Our overarching goal,” says Barocio, “is to augment confidence in large-scale additive technology and to enable first-time right printing.”
Susan Keen Flynn is managing editor of Composites Manufacturing magazine. Email comments to sflynn@keenconcepts.net.
LSAM: The Only Option
The Al Davis Memorial Torch is a testament to the possibilities of large-scale additive manufacturing (LSAM). It was “the only option,” admits Brandon Wood, vice president of engineering and R&D at Dimensional Innovations, the Kansas-based firm that manufactured the structure.
“We were at the point of turning down the RFP altogether because we had exhausted all our ideas for building the torch utilizing our traditional fabrication processes,” says Wood.
The company’s Innovation Lab, which had been closely following Thermwood Corp.’s journey into LSAM equipment, decided to pitch the idea of 3D printing the torch. They traveled to Indiana for a demonstration of Thermwood’s LSAM machine.
“We printed a set of four sample parts that allowed us to experiment with joinery and surface finish and think through what our final block geometry would look like,” says Wood.
The DI team was sold on the technology and acquired a 5 x 10 x 20-foot LSAM printer from Thermwood, which allowed the company to achieve the desired dual curve geometry.
“Rationalizing the torch shape into faceted panels was a non-starter, stamping metal panels was prohibitively expensive as each tool would be unique and used only once, and subtractive machining was not far behind in expense and never would have hit the timeline,” says Wood. “LSAM allowed us to use a hybrid additive/subtractive approach for near-net manufacturing to create the 226 separate blocks that make up the torch.”
