When Boeing embarked on its ambitious plan to make huge structural sections for the Dreamliner 787 aircraft from carbon composites, big questions remained on manufacturability. The biggest composite parts ever made had been hulls for yachts. Not only were the Dreamliner parts larger, they had to meet the cost and speed demands of series production.
Now 3D-printed plastic tools are emerging as a strong alternative to metallic tooling. This is a far different animal from the small 3D-printed tool inserts produced for injection molding.
The aircraft tools can be huge. The assembly tool being built for the new Boeing 777X passenger aircraft is 17.5 feet long, 5.5 feet wide and 1.5 feet tall. It’s comparable in length to a large sport utility vehicle and weighs approximately 1,650 pounds.
Made from carbon fiber and ABS, the tool was developed by researchers at the Department of Energy’s Oak Ridge National Laboratory (ORNL), using a Cincinnati Inc. Big Area Additive Manufacturing (BAAM) machine. Printing time was 30 hours. The proprietary extruder on the BAAM has a feed rate of 80 lbs/hour. Materials tested include ABS, PPS, PEKK and Ultem.
“The existing, more expensive metallic tooling option we currently use comes from a supplier and typically takes three months to manufacture using conventional techniques,” said Leo Christodoulou, Boeing’s director of structures and materials. “Additively manufactured tools, such as the 777X wing trim tool, will save energy, time, labor and production cost and are part of our overall strategy to apply 3D printing technology in key production areas.”
Vlastimil Kunc, leader of ORNL’s polymer materials development team, added: “Using 3D printing, we could design the tool with less material and without compromising its function.”
Boeing is using the tool in its new composite parts’ production facility in St. Louis. The function of the tool is to secure the jet’s composite wing skin for drilling and machining before assembly. First deliveries of the 777X are scheduled for 2020.
Several partners are working with ORNL to develop tools that can be used in autoclaves. Compounder Techmer PM, for example, developed custom formulated high-temperature carbon fiber-reinforced plastics for tools that endure multiple autoclave cure cycles, withstanding temperatures over 355 F and pressures of 90 psi.
The tools were printed on ORNL’s BAAM, machined on a Thermwood 5-axis CNC machining center, and then surface finished by TruDesign.
Other partners include US Naval Air Systems Command (NAVAIR), Boeing, TruDesign, and BASF.
In addition to allowing more design freedom, 3D printed tools are five to 10 times faster and cheaper than metal tools.