GM says its use of selective laser sintering (SLS) and stereolithography (SLA) have allowed its designers to quickly and inexpensively go from computer models to one-off parts for wind-tunnel testing, for example, so more iterations can be tested in less time. In this case, aerodynamics engineers can put a current production vehicle into the wind-tunnel and quickly swap out RP bumper covers, grilles, spoilers, and mirrors between test runs.
GM points out that 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, while today, 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.
Before the parts are actually prototyped, the computer models are tested for proper airflow using 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.
GM Aerodynamic Development Engineer Suzanne Cody said rapid prototyping also helps improve the accuracy of the one-third scale models that are used for early aerodynamic testing, long before a full-size model or vehicle is built, noting that air-flow through the engine compartment and underneath the car is critical to both cooling the engine and lowering drag.
The automaker has also used rapid prototype parts to speed up test track and on-road evaluations, noting that 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. Some of the most publicly visible application 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, with three body styles fabricated for the EN-V from 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.