I’m sure I read an interview with BMW Head of Design, Chris Bangle recently where he commented that no other manufacturer had cracked the nut of forming concave body panels for their cars.
I’m not an engineering kind of guy, but I can’t quite figure (since I assume the panels are stamped) what the big deal about stamping a concave panel could be.
Any thoughts?
Thanks
M
Have pictures? They shouldn’t be hard, but what are you talking about? There are a lot of variables to stampings.
It could be that they’ve gotten fancy techniques to work on carbon fiber body panels. I doubt that stamping would used in making those.
Doesn’t Mustang use concave panels? And Corvette?
It’s not simply concave panels that are tough - apparently it’s the co-existing convex and concave lines (aka “flame sufacing”) that are dificult.
The bigger mystery is how the panels are formed. Chris says “There is no stamp. It is a nice little BMW secret.” Elsewhere, he lets onto something called “multi axis surfacing” and that he’s especially proud of the “digital” technology behind the wrinkles in a new BMW’s hood. Reading between the lines, BMW is using CATIA (Computer-Aided Three-dimensional Interactive Application - a highly integrated evolution of computer-aided design and manufacturing (CAD/CAM) where “computer aided” isn’t just a tool, but the whole philosophy)
If it’s from BMW it is designed to visit the service department repeatedly.
Oh… are they talking about that funky character line that goes from the base of the B-pillar diagonally forward to the rocker panel near the front wheel well? There’s a little bit of concavity that lines up with some convexity. The Google images I see don’t let me get a gander from every angle, so I don’t know what the difficulty could be. Assuming it’s steel, there could be problems with the draw at those points. For example, you’re trying to stretch the thin metal too far in too many directions. Concavity’s usually not a problem these days because dies can have multiple sub-dies that move on their own axes during a press operation (not a press guy, I can’t think of the name for these dang things right now, but the solve the problem of what goes “in” has to come back “out”, kind of like how the graph of a function can’t come back on itself).
Hemming may be the greater problem. Outer panels are usually the thinnest, lightest stuff you can get (back to the draw problems, actually), but they’re really just skins on a more substantial substructure. The skin is “hemmed” around the substructure (wrapped around at the edges) for appearances and eliminating sharp edges. On the crappy pictures I’ve dug up, it looks like it could be a tricky hemming op near the rocker.
I think the Z4 is their most complicated surface design - here are some shots of it.
http://www.caradisiac.com/media/images/le_mag/mag264/geneve-bmw-z4-coupe-2b.jpg