Rapid Prototyping Creates Roadworthy Concept Parts

Rapid Prototyping Creates Roadworthy Concept Parts
EN-V bodies fabricated in 3D Rapid Prototyping Shop at GM Design

WARREN, Mich. - Whether a futuristic concept like the EN-V or a contemporary family hauler like the GMC Acadia Denali, three-dimensional rapid prototyping accelerates the creative process and reduces the time and money spent on clay modeling and molding of expensive prototype parts.
Designers and engineers from General Motors studios and technical centers around the world are able to see and touch their creations faster and at lower cost because of the digital manufacturing capabilities at the GM Design Center.
Selective laser sintering (SLS) and stereolithography (SLA) techniques allow designers to quickly and inexpensively go from computer models to one-off parts for wind-tunnel testing so more iterations can be tested in less time. Aerodynamics engineers can put a current production vehicle into the wind-tunnel and skilled trade technicians can quickly swap body parts like bumper covers, grilles, spoilers and mirrors between test runs.
Before the parts are fabricated in the rapid prototyping shop, the computer models are tested for proper airflow using state-of-the-art computational fluid dynamics software. These pre-tested parts can then be replaced much more rapidly and with better repeatability than old-style clay models can be re-sculpted. More time is spent evaluating the changes than waiting for adjustments to be made. In fact, testing capacity has doubled in the past two years.

"Long before a full-size model or vehicle is built, rapid prototyping helps to improve the accuracy of the one-third scale models that are used for early aerodynamic testing," said Aerodynamic Development Engineer Suzanne Cody. "Air-flow through the engine compartment and underneath the car is critical to both cooling the engine and lowering drag."

In the past, modelers would carve a rough approximation of the front structure and the engine from foam or wood to evaluate the air flow through the engine bay. GM's 3D prototyping lab can generate a fully detailed model including the engine, transmission, brake lines, drive-shafts, exhaust system, suspension and other components under the car.

"The end result is better correlation of air-flow measurements between the model and the full-size car or truck and fewer expensive changes are needed late in the program," said Cody. "With the design of components like cooling systems locked in earlier, fewer prototypes are needed and vehicles can go from concept to production more quickly."

Rapid prototype parts also speed up test track and on-road evaluations. When 80 pre-production Chevrolet Volts were being built in mid-2009, several interior parts were fabricated by the RP shop and installed directly in the test cars.

"In design, we work with conceptual ideas in preproduction. Early part iteration allows us to get hands on to see what works and what doesn't at the point where people actually touch the car," said Checo Pacheco, a lead creative designer in the Branded Component Studio.

Some of the most public applications of RP components to date have been the EN-V personal urban mobility concepts that were featured during the 2010 Shanghai World Expo and the 2011 Consumer Electronics Show. Three body styles were crafted for the EN-V at GM Design studios in Los Angeles; Melbourne, Australia; and Russelsheim, Germany. The RP shop in Warren fabricated the bodies and many of the components for the demonstration fleet.

"3D rapid prototyping is enabling the designers and engineers at Chevrolet, Buick, GMC and Cadillac to stretch the creative envelope," said John Green, superintendent, GM Design Fabrication Operations. "We can bring more attractive, functional and aerodynamic vehicles to market in less time and at lower cost than ever before."