Interview: Cadillac Discuss the Development of its 2016 Altair Enlighten Award Winning Entry, the CT6

7th December 2016

Following on from our interviews with Aloca (Arconic) and ContiTech on their success in the 2016 Altair Enlighten Award, we’re pleased to bring you insights from this year’s winner of the full vehicle category – Cadillac.

We recently visited their facility in Michigan, US, to record this conversation with Fernando Krambeck, the Program Engineering Manager for the Cadillac CT6. During the interview, Fernando takes us through Cadillac’s lightweighting strategy for the flagship car, detailing some of the challenges involved in creating a mixed material vehicle. You can watch the interview below.

 

For those without the ability to listen to sound on your machines, here’s a transcript of the interview.

 


 

Fernando Krambeck, program engineering manager for the Cadillac CT6

The CT6 team was honored to receive the Enlightened Award. It was a true honor to be recognized for all the efforts that we put into developing this car, to light weighting, and the fact that our peers and organizations are recognizing it was truly an honor to us and everyone that’s worked on this program.

The CT6 does use about 64% aluminum in its body in white overall usage. I really don’t have a vehicle to compare it to, because this is really a first entry in the segment. But to put that into perspective, we’re about four inches longer than the Cadillac CTS, and 20 kilograms lighter in mass.

Our estimation is we would be about 97 kilograms heavier if we were to use traditional metal. Most other vehicles we have within GM are starting to jump into aluminum, from aluminum hoods to castings. This is the first venture into really using it extensively throughout the entire vehicle.

This material brought a lot of challenges to us as we developed this car. From everything from joining same materials to mixed materials to formability, the formability attributes of aluminum vs. steel, as well as optimization of geometry to get stiffness and performance characteristics.

So developing the entire vehicle in such an aluminum-intensive material drove a lot of challenges in terms of determining whether or not we wanted stampings of aluminum or extrusions or castings, and how to really optimize performance to each one of the attributes of the different technologies available.

And then we also had to battle the joining technology. Whether or not we had access for a traditional aluminum to aluminum spot weld, or whether or not we had to go to a flow drill screw or a self-piercing rivet. Or whether or not we wanted to use MIG welding. So basically, we had to tailor each individual joint to the material selection, to the performance requirement for that joint, and leveraging CAE in every other attribute to try and optimize how we could develop this car to be the most mass efficient we could.

We used multiple different types of analysis to try and develop this vehicle. We used about 13 high pressure die casts. So we used certain types of analysis just to develop the overall optimal pattern within that casting. Define where the ribs need to be, how to define the structure, and how to best utilize that technology, geometrically, to meet all the attributes that we are looking for.

We’ve also used more traditional CAE approaches to develop some of the other stampings to develop what the gauges would be, what the aluminums would be, whether or not we wanted to use aluminum or whether we wanted to use high strength steel.

So we used all different types of analysis, depending on the application and depending on the location of the car.

We had several manufacturing concerns when we were developing the car. One of the main ones is really isolation. When you start getting to mixed materials and mixing aluminums with steel, you really need to focus on isolation, but yet maintaining integrity of joints. So as a result, we’ve used over 250 meters of structural adhesive and sealers to act as isolation between metal and aluminum. And to maintain all the structural bonds that we want.

We also had different areas where you couldn’t use traditional wells or flow drill screws or SPRs. And we had to do MIG welding. So we had to try and incorporate all the different joining technologies on this car to meet all the different requirements based on the panels, geometry, and applications.

As we continue to lightweight vehicles, we’re going to use two approaches. We’re going to one, use lightweight materials anywhere and everywhere we can.

But we’re also going to look at where we can minimize the use of material. Where can we thin gauge, where could we remove materials from castings, where can we thin interior varnish pieces, but still meet customer expectations. So as we go forward, really, it’s going to be a balance between both. Eliminating material where we don’t need it, and then using the right material where we can to get the best mass.

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