Pursuing the dream of 3-D printing an entire car chassis

ATLANTA — Oak Ridge National Laboratory is pushing the bounds of 3-D printing — working with an Ohio machinery company to print a full-size car chassis from carbon-fiber reinforced plastics this fall at the International Manufacturing Technology Show.

ORNL, which runs a Carbon Fiber Technology Facility in Oak Ridge, Tenn., is working with Cincinnati Inc., a maker of laser cutting and other equipment in Harrison, Ohio, and Local Motors, a Phoenix-based company that develops low-volume specialty cars selected through collaborative design.

Local Motors is running a 3-D Printed Car Design Challenge. The winner will strongly influence the final car design that will be printed at IMTS, and win a $5,000 prize and a trip to the trade show.

Cincinnati Inc. is building a large machine to do the printing, by converting the gantry on one of its laser cutting machines into a 3-D printer, according to Vlastimil Kunc, of the research development staff for deposition science and technology at Oak Ridge's Materials Science and Technology Division. Cincinnati and ORNL signed a partnership agreement in March to develop the super-sized additive manufacturing equipment.

The car chassis machine will include printing, high-speed cutting and pellet feeding. Cincinnati, which makes metal fabrication equipment and powdered metal compacting presses, have dubbed the effort “Big Area Additive Manufacturing” — or BAAM.

Kunc talked about 3-D printing of carbon fiber composites at ORNL's display at the JEC Americas show in Atlanta, May 13-15. Two small 3-D printers ran in the booth, where Oak Ridge fed lengths of carbon fiber directly into one of the machines, showing fused deposition modeling of small, finished reinforced ABS parts.

The demonstration at IMTS, in Chicago's McCormick Place Sept. 8-13, will be much larger. That machine will print one-piece car chassis using pellets of carbon fiber using fused deposition modeling. Kunc said. The exact resin has not been picked yet, he said.

Kunc said pellets are well suited for making large commercial parts using 3-D printing, better than lengths of fibers. “You don't have to pay big money for spools. You can take pellets just like for injection molding or extrusion,” he said.

Local Motors wants to make a car from 100 percent carbon-fiber reinforced material. Carbon-fiber reinforced chassis have been used on race cars, made from forming composites in traditional molding processes. 3-D printing is a hot topic — and making a chassis directly from additive manufacturing would be an attention-grabbing feat, especially at a major trade show.

Proof of interest in 3-D printing came at JEC Americas, as Kunc and John Lindahl, a research assistant, talked to a steady stream of people at the Oak Ridge National Laboratory's small display.

As Lindahl fed the carbon fiber into the little printer, it built up demonstration parts — including a small-scale model of one of the car chassis.

“I believe this may be the first time someone is demonstrating 3-D printing with carbon-fiber reinforced polymer, using fused deposition modeling, at a conference,” Kunc said in Atlanta. “We have a small printer that we have modified to be able to print carbon reinforced polymer, so right now we are printing with 13 percent fiber reinforced ABS.”

He said ORNL is experimenting with filaments that have up to 40 percent carbon fiber.

Fused deposition modeling builds up parts layer by layer using thermoplastics. The process is not new, but Kunc said use of carbon fiber for a part is a breakthrough.

“What we're showing now is that you can convert discontinuous carbon fiber onto the filament, and use fused deposition modeling to produce.”

ORNL wants to make the process more robust, to do direct manufacturing.

“We are trying to move fused deposition modeling from a prototyping technique, to a manufacturing technique that could actually be used to make product. So we are trying to improve the properties of the final part,” Kunc said. “The introduction of the carbon fiber allows us to have five to seven times the stiffness, and up to three times the strength, compared to the unreinforced plastics in FDM.”