Creating Concept Parts
GM builds one-off parts thanks to rapid prototyping
September 1, 2011
Rapid prototyping accelerates the part-creation process
Whether it’s for a futuristic concept car like the Electric Networked-Vehicle (EN-V) or a contemporary family vehicle like the Acadia Denali®, 3-D rapid prototyping accelerates the creative process and reduces the time and money spent on clay modeling and molding of expensive prototype parts, according to General Motors.
The company’s designers and engineers are able to see and touch their creations faster and at lower cost because of the digital manufacturing capabilities at the GM Design Center in Warren, Mich.
Selective laser sintering (SLS) and stereolithography (SLA) are two of the techniques that 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 computational fluid dynamics software. These pretested parts then can be replaced much more rapidly and with better repeatability than old-style clay models, which have to be resculpted. 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, the company reports.
“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 GM Aerodynamic Development Engineer Suzanne Cody. “Airflow 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 airflow through the engine bay. GM’s 3-D 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 airflow 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 prototyping of parts also speed up test track and on-road evaluations. For example, when 80 preproduction Chevrolet Volts® were being built in mid-2009, several interior parts were fabricated by the rapid prototype 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 GM Branded Component Studio.
Some of the most public applications of rapid prototype components to date have been the EN-V personal urban mobility concepts that were featured at 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 shop in Warren fabricated the bodies and many of the components for the demonstration fleet.
“Three-dimensional 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.”
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