The printed object was a forming tool, not an aircraft door. Thermoplastic aircraft doors are shaped by stamping hot plastic between two metal dies. ORNL and Boeing developed a 3D-printed metal mold to explore how to manufacture that tooling.
Conventional molds of this kind are made through machining, casting, forging, and drilling. The team explored whether a thermally controlled stamp form die could be easier, faster, and less costly to 3D print.
Wire deposition
The project explored wire-arc additive manufacturing (WAAM) using ORNL's Arc-1 system. Its robotic arm and welding torch melt metal wire and build up a part layer by layer. Arc-1 can feed multiple wires simultaneously and print with more than one metal.
The Boeing die used mild steel in its structural regions for strength and stiffness. Stainless steel was deposited at the mold surface for corrosion resistance, dimensional stability, and a durable working interface. The two steels served different regions of the same tool.
A channel shaped around the die
Heating and cooling fluids normally run through long, straight holes drilled in these molds. Here, 3D printing built curving channels that closely follow the mold shape. ORNL says those channels help heat and cool the part more efficiently and improve mold performance. The internal fluid path, as well as the deposited metal, was part of the manufacturing design.
Warping during printing
As deposited metal cooled, residual stresses twisted the mold and caused dimensional drift. The team added temporary ribs to the back and refined the design with simulations to compensate for warping during printing. After 32 simulation iterations, the produced mold was within a few millimeters of its intended shape.
The printed mold then went to Baker Industries in Michigan for annealing to remove internal stress. The ribs were cut away, and Baker Industries completed the remaining fabrication work to meet Boeing's requirements. ORNL states that not every part of the final tool was 3D printed.
ORNL reported a mold 6 feet tall and 4 feet wide, weighing nearly 2 tons in the source's unspecified ton unit. The molten steel was deposited over eight weeks. Annealing, rib removal, and remaining fabrication followed the printing.
Sources:
- https://www.ornl.gov/news/partnership-between-ornl-boeing-advances-manufacturing-aircraft-parts
- https://www.ornl.gov/technology/202305421
- https://www.nasa.gov/directorates/armd/aavp/hicam/about-hicam/
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