ORNL 3D prints 2-ton steel mold for Boeing aircraft tooling

Oak Ridge National Laboratory (ORNL) worked with Boeing to 3D print a steel mold for stamping thermoplastic aircraft parts, completing the nearly 2-ton tool in eight weeks using wire-arc additive manufacturing.

The mold was a Stamp Form Die measuring six feet tall and four feet wide, and was built to support NASA’s Hi-Rate Composite Aircraft Manufacturing (HiCAM) project, which aims to raise production rates for composite aircraft.

“NASA and its industry partners are working to increase the production rate of composite aircraft to meet the growing demand for air travel and to reduce aircraft weight, which improves fuel efficiency, lowering costs for aircraft operators,” said Richard Young, HiCAM Project Manager at NASA.

ORNL printed the mold using its Arc-1 system, using mild steel in the mold’s structural regions for strength and stiffness, and stainless steel at the mold surface for corrosion resistance and durability. Engineers also designed curving internal channels for heating and cooling fluid, rather than the straight drilled holes typical of conventionally machined tooling, to circulate fluid more efficiently.

“Boeing wanted to explore the possibility of using wire-arc additive manufacturing,” said William Carter, a robotics engineer at ORNL’s Manufacturing Demonstration Facility.

“Multi-material WAAM allows for the realization of completely new designs, combining fine-tuned mechanical performance with time and cost savings,” added Andrzej Nycz, a senior robotics engineer at ORNL.

Compensating for warping

Residual stress from the welding process caused the mold to warp as it cooled. To manage this, the team added temporary support ribs during the build and ran 32 rounds of computer simulation to predict and compensate for the dimensional drift, bringing the finished mold within a few millimeters of its intended shape. 

Once printing was complete, the mold was sent to Baker Industries, a Lincoln Electric subsidiary in Michigan, for annealing to relieve internal stress. The support ribs were then removed and Baker Industries completed the remaining fabrication to meet Boeing’s specifications. ORNL and Lincoln Electric collaborated on the project under a cooperative research and development agreement.

“Baker Industries values its strong partnerships with ORNL and Boeing,” said Evan Bartkiewicz, senior project manager at Baker Industries.

“It is imperative American companies continue to innovate and push technical boundaries to retain our competitive advantage in the global marketplace,” said Michael Matlack, a Boeing Technical Fellow.

Ahmed Arabi Hassen, ORNL’s group leader for Composites Innovation, said the project served as a proof point for the technology beyond aerospace. “We used this as a test case,” Hassen said. “Its success means the technology could be used to make large thermoplastic structures for other sectors of U.S. industry, such as energy and automotive.”