Purdue’s Virtual Twin for Additive Manufacturing Is Helping to Refine 3D Printing of Tools for Large Aircraft PartsPurdue’s Virtual Twin for Additive Manufacturing Is Helping to Refine 3D Printing of Tools for Large Aircraft Parts

Collaboration between materials expert Techmer PM and machine maker Thermwood is helping to advance additive manufacturing.

Robert Grace

July 27, 2024

7 Min Read
Techmer & Purdue’s Virtual Twin for Additive Manufacturing 3D Printing of Tools for Large Aircraft Parts
A large tool was designed to mold carbon fiber-reinforced composite air inlet duct components (such as these sample parts) for use on NASA’s X-59 experimental aircraft.Techmer PM

Aircraft and composites manufacturers continue to explore new ways to leverage additive manufacturing (AM) to cut costs, reduce weight, and speed part production. One of the keys to broader adoption: Being able to predict accurately how 3D-printed molds or tooling will perform when subjected to manufacturing conditions. 

To that end, Purdue University’s Composites Manufacturing & Simulation Center (CMSC) is working closely with an engineered-materials specialist and an AM equipment manufacturer to demonstrate first-time-right printing of composites molds for the production of an air inlet duct for a supersonic aircraft.

Thermwood Corp., a maker of large-scale additive manufacturing (LSAM) machines in Dale, IN, and Techmer PM LLC, a materials design specialist in Clinton, TN, are not aiming to produce final parts. Rather, they are aiming to prove the LSAM process with materials suitable for manufacturing of molds required in the aerospace industry. 

The two firms, longtime partners, decided to demonstrate what is possible using an air inlet duct for a supersonic aircraft as a case study. They did so with support from Dr. Eduardo Barocio, Purdue’s director of the Composites Additive Manufacturing and Simulation (CAMS) Consortium, and his colleague Dr. Garam Kim. 

Related:NASA and Protolabs Demonstrate the Value of Generative Design

The aim was to create the large mold (and related trim fixture) needed to produce such a part via large-scale additive manufacturing. 

Choosing polyethersulfone for the tool

“The geometry itself makes it very difficult to 3D print and run through an autoclave,” explained Jason Susnjara, Thermwood executive vice president, in an interview at the recent NPE 2024 plastics expo in Orlando. The resulting 300-lb tool uses Techmer’s Electrafil PESU 1810 grade of polyethersulfone resin. The material needs to withstand autoclave temperatures of 350°F with 80 PSI of pressure.

“We tried PPS (polyphenylene sulfide), which is a semi-crystalline resin,” Susnjara said. “And when you get to a certain size because of the additional crystallization shrinkage, it makes printed parts more susceptible to crack. And we couldn't get around that. So, we went to an amorphous-type material, which is PESU.” 

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Techmer specially formulated PESU 1810 for AM applications, for bead surface smoothness, durability, viscosity, compounding optimization for pellet geometry, enhanced mechanical properties, and, ultimately, superior printability. 

Not only did Thermwood and Purdue print the autoclave tool, but also the trim fixture needed to trim the carbon fiber cured on the printed tool in an autoclave. For that fixture, it used Techmer’s Electrafil ABS 1501

Related:NASA Launches Rocket Created Entirely of 3D Printed Parts

Purdue’s virtual twin ADDITIVE3D software allowed the parties to predict and compensate for the anisotropic shape change of the printed tool when it operates at the autoclave temperature. Additionally, there is spring back on the composite part itself, which was predicted and compensated for in the design of the printed tool.

Producing a CF aerospace-grade composite part 

“The large, 3D-printed tool is designed to form parts made from an aerospace-grade, carbon-fiber-reinforced epoxy composite,” said Jenna Hunt, Techmer’s business development manager for engineered compounds and additive manufacturing. The material contains 60 percent CF-epoxy and the resulting component measures 29.5 in. (75 cm) long by 24.4 in. (62 cm) wide. It weighs just under 3 lb (1.35 kg). The composite part demonstrated here was cured on the printed tool at 350°F and 80 PSI of pressure.

“This application represents a mockup of the NASA X-59's air inlet duct,” Hunt said. “While the manufacturing process is similar to the process demonstrated herein, the specific weight, dimensions, and geometry are not the same of the part used in the actual aircraft.”

The X-59 is NASA’s experimental quiet supersonic aircraft.

“The purpose of this AM demonstration,” Hunt said at NPE, “was primarily focused on the use of predictive simulation tools to get the right part shape produced right the first time following the procedures used in the production of aerospace-grade composites.” This involves shape compensation of both the composite part and the printed tool. 

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Finding value in Purdue’s CAMS Consortium 

Techmer announced on July 11 that it has become the first materials supplier to join Purdue’s CAMS Consortium. Thermwood and several aerospace OEMs are already members. 

The Composites Manufacturing and Simulation Center, home of the CAMS Consortium at Purdue, is world renowned for its expertise in manufacturing, simulation, and characterization of composite materials.

Barocio said the CAMS Consortium will benefit from Techmer’s extensive expertise and technological advancements, particularly in recycling technologies, and how that can be applied to large-scale AM. Techmer and Purdue say they will combine physics and chemistry to create robust, tuned materials optimized for LSAM while providing education, validated simulation tools, materials characterization, and best practices in the industry. 

Techmer says that by joining the CAMS Consortium it aims to further contribute to the confidence in large-scale AM by developing digital material cards for more of their material formulations. These enable simulating the printing process and predicting the performance of the as-manufactured tools with ADDITIVE3D. A digital material card contains extensive test data required to describe the material not only as it is printed, but also once it’s used in the final application.  

“It's not like Techmer just sends information over to the Purdue team and, boom, it automatically creates a material card,” Susnjara noted. “There's a lot of work that goes into it, a lot of science, a lot of studying, a lot of playing with the material, in order to create this material card.” Purdue’s sophisticated simulation software, by factoring in dozens of variables, also enables the creation of “machine cards” for firms such as Thermwood. 

Combining physics with the chemistry 

As for the value to a compounder such as Techmer, Hunt said that working with the CAMS Consortium, “in layman's terms, it's taking our piece, that's the chemistry side of things and it's adding in the physics.”

The simulations are able to predict such factors as residual stress or other things that could happen to a part. For companies printing a large part of several hundred pounds or more, they don’t want to go through that entire process only to have problems with the resulting part that render it useless and waste tens of thousands of dollars. 

Purdue’s simulation software, developed based on a strong scientific foundation, considers many parameters of the process and takes into account all the possible variables. When using qualified material and machine cards, it predicts how much a given, 3D-printed object is going to change in different directions. The manufacturer can then compensate for that and produce the right shape the first time, rather than iterating empirically, which can take significant time and resources. 

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Creating a valuable baseline 

Not all manufacturers use Thermwood LSAM 3D printers, Hunt acknowledged, and the data generated on a Thermwood printer may be different than the data that's generated on a robotic-arm-style printer. But still, she said, Purdue’s resulting simulation data provides “an incredible baseline, and offers the ability to make machine-specific material cards.” 

Hunt notes that Techmer can create or extend any existing material cards to any type of 3D printer, so long as it has a machine card. 

If manufacturers can trust the large-scale AM process, Susnjara said, they can realize at least 50 percent savings on both material and time compared with traditional approaches. “It'll take us two weeks to create this tool; it normally will take them [about] six months.”

Aircraft makers also will want to know how long the tool will last compared to a steel mold. Barocio and his team at Purdue are studying that now. 

“Printed tools can be used for producing tens of parts,” Hunt noted. “This specific demonstration only considered 10 parts and demonstrated the shape stability over multiple autoclave cycles.” 

Thermwood, founded in 1969 by Susnjara’s father, Ken, began life as a thermoformer and as a CNC router manufacturer. But for decades now its focus is on producing and refining large-scale additive manufacturing machines. 

By combining Techmer’s materials formulation expertise with Purdue’s simulation expertise, the company hopes to revolutionize how manufacturers such as aircraft makers can effectively employ 3D printing to confidently produce tooling for manufacturing large, high-performance composite components. 

About the Author

Robert Grace

Robert Grace is a writer, editor, and marketing communications professional who has been active in B2B journalism since 1980. After editing trade publications in London for seven years, he returned to the US in 1989 to help start the weekly Plastics News. Bob was PN’s editor-in-chief for 25 years and also served as its associate publisher and conference director. In May 2014 he founded RC Grace LLC and has developed an active freelance business.

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