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Recent improvements to the BAAM machine include a smaller print bead size, resulting in a smoother surface finish on printed pieces. (Click on arrow at top right of this photo to see a photo of the 3-D-printed Shelby Cobra.)

Shelby Cobra puts sporty face on 3-D printing technology

Oak Ridge National Laboratory (ORNL) put a very pretty and sporty face on its 3-D printing technology at the 2015 North American International Auto Show in Detroit, showing off a replica of a classic Shelby Cobra made via the rapidly propagating technology.

The approximately 1400-lb (600-kg) vehicle contains 500 lb (200 kg) of printed parts made of 20% carbon fiber.

The car was printed at the U.S. Department of Energy’s ORNL facility, which houses a so-called BAAM (Big Area Additive Manufacturing) machine that can produce lightweight and strong composite parts greater than 1 m³ (35 ft³) in size.

The team took six weeks to design, manufacture, and assemble the Shelby, including 24 h of print time. The new BAAM system, jointly developed by ORNL and Cincinnati Inc., can print components 500 to 1000 times faster than today’s industrial additive machines. ORNL researchers say the speed of next-generation additive manufacturing offers new opportunities for the automotive industry, especially in prototyping vehicles.

“You can print out a working vehicle in a matter of days or weeks,” said Lonnie Love, Leader of ORNL's Manufacturing Systems Research group. “You can test it for form, fit, and function. Your ability to innovate quickly has radically changed. There’s a whole industry that could be built up around rapid innovation in transportation.”

The BAAM machine is still in the prototype stage, according to Cincinnati Inc. Recent improvements to it include a smaller print bead size, resulting in a smoother surface finish on the printed pieces. It uses a wide variety of thermoplastics and fiber-reinforced thermoplastics.

For the Shelby, subsequent work by Knoxville-based TruDesign produced a Class A automotive finish for the NAIAS showpiece.

The manufacturing and transportation researchers at Oak Ridge plan to use the 3-D printed Shelby as a laboratory on wheels. The car is designed to “plug and play” components such as battery and fuel-cell technologies, hybrid system designs, power electronics, and wireless charging systems, allowing researchers to easily and quickly test out new ideas.

The Shelby project builds on the successful completion of the Strati, a fully 3-D printed vehicle created through a collaboration between Local Motors and ORNL. The BAAM machine was used to make many of the various parts, including structural ones, for the Strati, which was designed as part of a contest held by Local Motors and built on site at November’s International Manufacturing Technology Show in Chicago.

Sabic Innovative Plastics supplied the carbon-fiber-reinforced ABS plastic. Renault donated the powertrain from the Twizzy, and some of the mechanical parts were “leveraged” from the same car. Siemens provided the Solid Edge software for the structural design elements and Fifteen52 provided customer wheels.

The linear-motor-driven BAAM machine currently has work envelope of 2 x 4 x 0.87 m (6.6 x 13.1 x 2.9 ft) and an extrusion rate of about 38 lb/h (17 kg/h). It prints polymer components up to 10 times larger than currently producible. Plans are to increase the work envelope to 2.4 x 6 m (8 x 20 ft) and, with Sabic, to increase the extrusion rate to 100 lb/h (50 kg/h). Another priority is increasing Z-axis travel (the working height for the part being built), according to Cincinnati Inc.

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