Q&A with GM Expert on the Company’s Lightweighting Initiatives

Lightweighting World recently spoke with Charlie Klein, executive director, global CO2 and energy center for General Motors. The automaker has made significant strides in its nearly fleet-wide move to develop lighter vehicles, with several new models having an average weight reduction of 350 pounds per vehicle. We wanted to learn a lot more about the company’s impressive lightweighting initiatives and what’s driving them.

LIGHTWEIGHTING WORLD: How did lightweighting of GM automobiles begin? Was it a top-down decision, or was it born in GM design and engineering labs? What drove that significant weight reduction in mass-production auto manufacturing, when many in the industry still view lightweighting as too expensive for big manufacturing numbers?

CHARLIE KLEIN, GM: The drive for lightweight was born out of the drive for vehicle efficiency and with a keen focus on the customer. Our engineering leadership set the tone and expectation for excellence. GM engineering leadership built our strategy around what we call efficient fundamentals that are the backbone of vehicle programs. These efficient fundamentals include component optimization, advanced propulsion technologies, aerodynamic refinement and focused lightweighting. While each individually contributes to the overall vehicle efficiency and drivability, they are more impactful when combined and working synergistically. A lighter, more aerodynamic vehicle can be propelled by a smaller, more efficient engine than a heavier vehicle, for example. A lighter vehicle can use lighter-weight components. In addition to improved efficiency, efficient fundamentals also result in improved vehicle dynamics and drivability.

LW: In the automotive industry, lightweighting is a relatively new trend and competing priorities that impact it. From an organizational standpoint, what challenges do lightweighting initiatives bring to GM?

KLEIN: Lightweighting has become a cultural priority in engineering at General Motors. We have a saying, “Every engineer, every part, every gram matters.” Our engineers understand that every gram needs to earn its way into a vehicle. They all understand that their efforts are an important part of a larger system that, in the end, must deliver on the promise to our customers.

 LW: While there is no silver bullet for lightweighting success, what is the most important aspect of lightweight vehicle manufacturing going forward? Increased use of mixed materials? Design and simulation of lightweight components? Tooling and production? All of the above?

Cadillac will use an advanced mixed-material approach for the lightweight body structure of the upcoming CT6 range-topping sedan. The structure is aluminum intensive, but the new Cadillac also includes 13 different materials customized for each area of the car to simultaneously advance driving dynamics, fuel economy and cabin quietness. Sixty-four percent of the CT6 body structure is aluminum, including all exterior body panels – and the mixed material approach saved 90 kg (198 pounds) over a predominately steel construction.

KLEIN: A clearly defined vehicle mission is the most important aspect of lightweighting. Having a clear understanding of the goals and objectives of the vehicle, based on a clear understanding of the customer, enables engineers to apply the best methods to reducing vehicle mass. With those goals identified, engineers can correctly employ design and simulation tools to create an efficient topology and identify the right materials in the right gauges in the right locations to achieve the vehicle performance targets for efficiency and safety. A mixture of steel types may make more sense for a high-volume and more mainstream vehicle like the Chevrolet Malibu. A more exotic combination of materials such as aluminum, carbon and steel may be better suited in a performance vehicle, like the Corvette.

LW: What is GM’s goal with its sustainability initiative? Meeting increasingly strict government fuel standards, emissions reduction, consumer demands and environmental considerations? All of the above?

KLEIN: We have a responsibility to our customers and our communities, and these are all important to us. General Motors has remained committed to improved fuel economy for our customers and a better environment for everyone. Nothing showcases our commitment more than our leadership in electric vehicles and the Chevrolet Bolt EV—the first EV for everyone with 238 miles of range on a single charge and a net price of less than $30,000. The Bolt EV is a clear demonstration of our commitment to innovation that builds jobs and customers for life. When it comes to General Motors’ environmental commitment, we’re focused on our products, our plants and our actions. Addressing climate change in an effective and sustainable manner requires a holistic approach involving all sectors of the economy.

LW: Granted, government regulations and emissions-reduction strategies of automotive manufacturers are a global trend. Here in the U.S., if the CAFE standards are reduced as a goal of the Trump administration, will GM continue to move forward with its vehicle lightweighting program at the same rate?

KLEIN: Yes. Lightweighting is more than just meeting regulations. It is about building better vehicles.

LW: Are there significant differences in GM’s lightweighting strategies from country to country, continent to continent? If so, can you elaborate?

KLEIN: No. GM is a global company, and many of our models are used in global markets. What’s more, highly efficient vehicles have attributes that customers in all markets appreciate and benefit from—fuel economy, driving dynamics and many others.

LW: The Cadillac CT6, in production since early last year, is GM’s first complete vehicle with a body made from mixed materials—incorporating several grades of steel, sheet aluminum, sheet and castings, aluminum extrusions and magnesium. Does GM see the mixed-materials approach as the most important lightweighting trend for future years?

Cadillac will use the auto industry’s most comprehensive and advanced mixed-material manufacturing techniques to build its all-new CT6 top-of-range sedan, allowing creation of a top-of-range large luxury sedan with the agility and efficiency of a smaller vehicle. Techniques include material joining processes such as patented aluminum spot welding, shown here.

KLEIN: There is no a single strategy or technology when it comes to lightweighting. Identifying the right materials in the right place is the most important aspect of lightweighting now and in the future. Using the right analytical tools and spending time upfront before building a single part is critically important to lightweighting. For example, GM engineers spent millions of computational hours designing the new Chevrolet Equinox. The new vehicle uses a wide range of steel and is both 400 pounds lighter than the outgoing model and 30-percent stiffer, providing better driving dynamics.

LW: The process of building the CT6 sedan is a precursor to GM’s next-generation full-size pickups coming in late 2018 or earlier. Can you share with Lightweighting World readers some of the weight-reduction strategies that are going into the new pickup truck lineup?

KLEIN: I cannot make any comments about a future product lineup, but I can say that the same strategies and principles make sense regardless of vehicle segment.

LW: How is GM adapting the production machinery that the company already has invested in for lightweighting and mixed-materials applications?

KLEIN We are looking for opportunities to use the same machinery for various types of materials. For example, most welding in automotive today centers around resistance spot welding (RSW). By inventing new processes, we are now able to RSW steel to steel, aluminum to aluminum or aluminum to steel, using the same RSW tools. This saves considerable time and capital necessary to switch lines to some other process.

LW: Tell us about GM’s crash-safety program and how lightweighting of components is affecting it.

KLEIN: Our commitment to outstanding safety performance is unchanged by our work in lightweighting. In fact, it is complementary. We use advanced simulation and optimization tools to develop structural topology that protects the occupants while doing so in a highly efficient manner. For us, we look for AND solutions, not OR solutions. That is what great engineering is about—finding solutions that meet multiple dimensions and requirement for the customer—not ones that require them to make tradeoffs or give something up.

LW: Is there one material that GM designers and engineers see as an increasing player in lightweight-vehicle development?

KLEIN: No. We continue to investigate a wide range of materials, from carbon and composites, to advanced high-strength steels, aluminum and magnesium. And the respective industry groups continue to invest in the advancement of their material properties, which provides us even greater choice of applications.

 

 

 

 

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