I personally love innovation, especially creative innovation which contributes to the benefit of all drivers. Let me explain.
BMW has been working on trying to lower the center of gravity of their M cars with some innovative ways. Therefore they wanted to replace the roof of the vehicle (being the highest point of it by lowering the center of gravity) with a lightweight but strong component. The obvious choice was aluminum but it’s not exactly the strongest material for that.
Then they figured carbon fiber has been used in motorsport extensively and in some ultra high end vehicle manufacturing but it’s cumbersome to make and gets expensive. Then their engineering department got the assignment to develop the carbon fiber roof structure for the BMW M3 CSL in 2003 .
You need to know carbon fiber manufacturing is expensive because it’s a long tedious process. Multiple steps, a lots of time, a lot of energy required, which makes it a rather slow process and expensive to boot .
BMW came up with a clever solution: What if we combine some of the processes? This way we can reduce the time and effort required to make the lightweight but 5 times as strong as steel carbon fiber roof for the application. Carbon fiber usually comes in large woven rolls and pre-pregged for ease of use. Then it gets applied to a mold in 5 to 6 layers each in a different direction and then it gets flooded with epoxy resin.
Next step is having all wrapped in a cloth which would soak up the excess resin and then the whole thing get wrapped in a plastic bag with suction ports attached to it. After that, it is put under vacuum, placed into an autoclave and gets baked for hours on end under pressure.
This entire process is essential to make strong but light carbon fiber components. The suction is required to remove any potential air bubbles and the entire thing is put under pressure in the autoclave for best results.
Once again, BMW came up with a clever idea. They made 2 molds, a positive and a negative mold and put 6 layers of carbon cloth sheets over each other but not pre-preg just dry sheets in different directions. Then squeeze the the sheets of carbon fiber between the mold and inject the resin. Then they bake the whole thing in a single but efficient process. They get the CFRP (carbon fiber reinforced plastic) which gets done in 20 minutes or less. Therefore this can be done efficiently and quickly with phenomenal results for the application fully automated.
The ready to install panel gets trimmed and cut with a high pressure water jet to make it precisely shaped and ready to glue in place in a very efficient manner.
Once they perfected this process we came to the next chapter. The i3 and the i8 BMWs’ life structures gets developed with the same process. According to BMW they saved 50% energy and 70% water for the equivalent sheet metal body panels.
Remember the initial process was developed for the 2003 BMW M3 CSL, therefore BMW took 10 years to get into the partnership with SGL and build up a supply chain with every step on the way to ensure a near zero CO2 output for a full environmentally friendly process.
They actually build with SGL a carbon fiber manufacturing plant in by the largest electric dam at Moses lake, the Grand Coulee Dam.
Carbon fiber strain is an extremely expensive process where you have to bake the high quality polimer at an airless space under very high heat to convert the molecules into carbon fiber.
The actual strains are woven into a cloth in at Wackesdorf Innovation Park and then shipped to Leipzig for final manufacturing and assembly.
The Leipzig plant was the first ever solar and wind only powered plant in the world. You could walk around without ear protection in there as well.
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