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BMW looks to steel-and-aluminum joining to shave weight

Steel News - Published on Wed, 13 Sep 2017

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Repairerdriven News reported that BMW this summer shared some of the new lightweighting innovations that helped the OEM cut weight from the next-generation 5 Series and offered a glimpse of future tactics. Some of the methods discussed by BMW head of lightweight design and vehicle weight Mr Florian Schek during the Center for Automotive Research’s Management Briefing Seminars might affect collision repair, particularly BMW’s exploration of joining steel to aluminum.

Mr Schek said that one example was the rear side member on the 7 and 5 Series, which consolidated 18 parts into a single aluminum cast element and saves 24 pounds. He said “That’s a part of the architecture.”

He added “BMW also looked to cut mass out of the outer shell weight with aluminum and in the cases where already had used the metal, we tried to optimize it more.”

The OEM switched from crimping and bonding all-aluminum doors to laser-welding aluminum outers to steel inners, cutting at least 13 pounds out of the car, according to Schek.

Asked about the repairability of the door skin once crimping and bonding the door skin was replaced by laser welding (a shop can do one, but not the other), Schek said he wasn’t an expert on BMW collision repair but he thought a door in a collision would be “completely exchanged.”

Replacing a door skin “doesn’t make any sense because of the labor cost,” Schek said. It seemed to make more sense just to install a new factory door, he said.

Schek said that in the future, BMW would like to make the outer shell of its architecture aluminum, but the inner frame might have to remain steel to achieve the proper crash safety. He said “That means you need to combine the aluminum and the steel.”

BMW might have to develop a new process of adhesives and roll forming to crimp and glue the outer around the inner steel subframe, according to Schek. (Generally, aluminum and steel can’t touch, or else one risks galvanic corrosion.) The problem comes with integrating it into a factory, as the assembly line would have to handle both the older format and the new lightweighted design, he said.

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Posted By : Nanda Koijam on Wed, 13 Sep 2017
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