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      06-21-2012, 07:15 AM   #57
mapezzul
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Quote:
Originally Posted by swamp2 View Post
You have this quite backwards.

Particularly with carbon fiber, as opposed to other composites such as glass fibers or others, material costs are almost for sure going to dominate total body manufacturing cost.

See the following from a pretty good MIT PhD thesis from 2006. Although you could certainly argue/debate/refute some specifics, the overall result that costs are material driven are clear and the ratio is not close nor small. Reference: fuchs.pdf. This is assuming 100k units/year which is right in line with the M3's target volume. It is key to note that the author assumes CF prices of right about $10/lb. Even if BMW reached their goal of $5/lb my conclusion is still valid but it is much closer to break even. Surprise, surprise... This observation dovetails very nicely with this $5/lb goal stated by BMW&SGL. Similar results should follow for components as well as long as aerospace type manufacturing methods are not used. The results may or may not follow for radically different manufacturing methods such as pultrusion or filament winding, etc. that might be used for non BIW type shapes. My gut tells me though that the same conclusion would still follow.

One other relevant data point is that McLaren can now manufacture the MP4-12C composite body in just 4 hours. Your thoughts may be guided by examples like an F1 car taking 3000 hours to manufacture or a MB SLR McLaren at 500 hours.

Lastly this work fully validates my "back of the envelope" estimates that it would cost around $1000 to save around 300 lb although this work seems to puts the 300 lb estimate closer to 500 lb, but again this is at the higher $10/lb figure. I'll easily take 50% or so accuracy for 5 minutes of work vs. perhaps 80% accuracy for many years of work (on a PhD...)
Considering the whole side of an i3 life module can be supported by an index finger (I would bet it weighs in at max 30 lbs.) so what is that $150 per side? That's dirt cheap. A pound of CF is a lot of material compared to a pound of cold pressed steal (looking at you fat F10). If you look at your study they in 2006 were using this "Carbon Fiber: $11.05/kg" (which is $5/lb) and I can tell you BMW is way way under that for the CF.

What I was told by BMW was that the biggest difference aside from producing cheaper material bc of energy costs in savings was the less time and energy required to produce the parts with their molding/resin process, making them much much cheaper. Requires less equipment, less heat, less electric less of everything and makes the operating costs less of an issue. They are also using the cut fabric scraps (non chopped) for other parts- basically they cut everything like a giant jigsaw so true scraps are minimum and they get the most out the CF fabric as possible.

At the end of the day things are going to happen, they have made huge gains and the future products will be the better for it. I can't wait!
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Last edited by mapezzul; 06-21-2012 at 01:25 PM..
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