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Engineering the Chrysler Neon via CAD-CAM

Computer aided design technology and use of advanced composites broke new ground in designing and prototyping with the all-new 1995 Dodge and Plymouth Neon. The Small Car Platform Team expanded an existing engineering technology by using a unique application: carbon fiber body panels were cut from computer-based tooling very early in the program to produce the first body prototypes.


Chrysler's use of computers in engineering was advanced by just about any standards. Indeed, word is that much of the Dassault CATIA package was created with Chrysler assistance; as with computerized spark control and electronic ignition, Chrysler was a pioneer in computer aided design. Its own CAD/CAM system had been launched in 1983, and was used to create the Reliant and Aries; but they had been doing computer aided design and analysis since the 1950s.

"On previous projects, stamped body panels would not be available until the 50 week point (from production) in a program," said Robert Dynes, executive engineer - Body-in-White and Exterior for the platform team. "To really appreciate the scope of what that means, consider that previously anyone working on a system that interacted with the body of the car in any way -- say a headlamp assembly or door seal - - had to work from renderings and blue prints to design and develop the part. There was no way of checking for accuracy or possible problems until only one year from production when an accurate body representation was available."

Adding lead time for engineers working on associated systems without adding to overall lead time was coupled with a major step forward in tooling and manufacturing with the use of Computer Aided Three-Dimensional Interactive Application (CATIA).

The software package, produced by Dassault, a French aerospace company, allows designers to create representations of solid components on a computer screen -- precisely simulating everything from an object's weight to its points of inertia to its structural soundness.

Older CAD/CAM languages allowed objects to be developed and manipulated on screen; these representations were based on "wire" graphs which formed the shape of the system or part. While it was possible to mathematically prove a design from points on the graph, it was not possible to accurately represent a true surface.

"This was because the space in between the graphed lines could not be represented, thus you were never dealing in true surfaces," Dynes said. CATIA is able to mathematically fill in the space between the graphed lines, giving representation of an accurate surface.

"As good as our traditional CAD/CAM software performed, it was possible to take a design from computer to a clay model and discover that the surface was not linear," said frank Havasi, manager of the Neon Body-in-White program. "With CATIA not only can we make a perfect surface, we can even check the linear form of the surface using simulated light reflections.

"That's a for cry from when our designers would take a wood model, which was developed from a clay model, and eye the surface for imperfections using a piece of sandpaper to smooth out the flows. It was from that wood surface that you would get the tooling," he added.

The CATIA-produced carbon-fiber panels used on Neon were so accurate at the 100-week before production point in the program, that they were actually used to check the hard tooling that was set up by manufacturing to build the metal-bodied prototypes.

"This was without question the first program that we've worked on in Chrysler where we didn't have one tooling crash," Havasi said. "Imagine getting through clay models, wood models, tooling blue prints, and eventually hard tooling, only to find there is a flaw in the tooling which mandates starting all over again - including all of the costs. It's something we simply could not afford under our new way of developing vehicles with the least amount of money required."


In addition to avoiding tooling crashes, the panels could also be set into the pilot plant to test automated systems, such as computer robotics. This helped to eliminate early snags in the manufacturing process that would otherwise not have been foreseen.

The use of carbon-fiber also allowed for quick changes to the design of the vehicle at later stages of the program without major cost implications. "for instance, we made a major change to the headlight shape fairly late in the program," Havasi said. "With the use of CATIA and carbon-fiber, the change was made with relative ease without slowing down the program.


CATIA stores every aspect of the Neon design numerically and generates a computerized model with all of its specifications held in a central database, available to all engineers working on the program. These specifications are then sent to both in-house and external suppliers via computer for tooling development.

"We aren't exaggerating when we say that no paper was transferred between design, engineering and the tooling suppliers," Dynes said.

All of the information is available simultaneously to all members of the team. This takes out untold amounts of time, effort and error known in the older system of transferring blue prints and renderings, Dynes said. He added this eliminated a lot of guess work early on and vehicle build quality early in the process was outstanding.

"The problems we're dealing with in the plant are issues that, frankly, we wouldn't have been attending to until well after the launch," Dynes said. "In other words, problems so minor they are more process oriented and not readily apparent to the consumer.

Information provided by Chrysler Corporation (except second paragraph).

Also see: details of the Neon design process

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