GM's meticulous approach to weight savings
WARREN (Michigan)
A few years ago, Ford made a big splash with its F-150 pickup truck made primarily of aluminum. Ford was banking on a weight reduction of nearly 700 pounds while keeping an eye on its competitors who were watching what was going on at the Blue Oval while working on their own configurations to reduce the weight of their vehicles.
This materials battle was aimed at improving fuel economy while meeting all future requirements of certain markets. Some strict rules are dictated by these companies' largest markets, namely China and the United States. In order to comply with these fuel efficiency and emissions rules, automakers need to move more towards fully electric or hybrid vehicles. However, before they can make this shift, each vehicle must be lighter.
General Motors' strategy is different from Ford's, with a mix of aluminum, high-strength steel, magnesium and carbon fiber to reduce weight. To showcase its approach, the automaker invited a group of journalists to its technical center in Warren, Michigan, to talk to their specialists.
"There is no single material solution," said Charles Klein, director of the CO2 Strategy and Energy Center. We use the best material for each component."
This philosophy of the importance of every gram of a manufactured part is fully embraced. GM pays attention to the smallest details and is constantly looking for alternatives that focus on dollars per kilogram saved.
The Detroit-based brand can already boast (and has) a combined weight reduction of nearly 2,400 pounds for all seven of its new vehicles compared to previous models, which averages out to 300 pounds per new vehicle. All of these weight reductions contribute to lower carbon dioxide emissions in addition to improved driving dynamics and safety and a quieter ride.
As impressive as it sounds, GM got these weight reductions before the new tricks we discovered in Warren were implemented. Let's take a look at some of GM's plans in the works.
Spot welding of aluminum to steel
Welding aluminum with aluminum has taken several years of work and GM is only months away from implementing a patent-pending aluminum-to-steel spot welding process. This is a system that typically results in premature failure of the weld, which comes in the form of a shiny, metallic substance or aluminum oxides.
However, GM says it has been working on this internal process for the past two years and is ready to use it on its future vehicles, starting with the construction of seatbacks in its Cadillac CT6, followed by a steel support rod to be placed inside its aluminum hood.
"It's mostly about creating tools and understanding the physics," says Blair Carlson, group manager of the research and development sector's lightweight materials processing lab.
You really have to understand the physics to fully grasp this concept and GM has not fully disclosed what it does. However, the process is related to electrode geometry, a single weld and a weld schedule, all within existing infrastructure and without the use of special tools. Through its use of physics, GM is able to reduce the number of rivets used, which not only helps to reduce costs, but more importantly, weight. Currently, 196 parts have been eliminated from the CT6 and this number will only decrease with this technique.
The interest of other automakers in licensing GM's technology is a testament to the automaker's achievements. There have been preliminary discussions with others, but nothing has been concluded yet.
Magnesium to the rescue
Other interesting elements include magnesium, a more expensive lightweight metal already used in the tailgate of the 2017 Chrysler Pacifica minivan.
Compared to high-strength steel, magnesium offers an additional 30% weight reduction, surpassed only by carbon fiber, which is also being studied for high-end GM wheels. But again, the addition of magnesium is a matter of cost-benefit balance with the right materials in the right place in each vehicle.
On display was a car door inner panel and a doorstop, both made entirely of injection molded magnesium. Let's talk about the door, because the traditional steel door has seven pieces assembled, while the magnesium version has only one. The magnesium version not only saves production time, requiring only 90 seconds of manufacturing, it also cuts the weight of the door in half, from 8.9 to 4.6 kg.
When asked how long it takes to make a steel door, Anil Sachdev, manager of the research and development sector's light metals lab group, couldn't even answer and simply pointed out the number of bolts and welds required to make a single steel door.
Anil Sachdev went on to explain that GM was always looking for new ways to do things. For example, magnesium could be used in seats, steering wheels, or elsewhere, depending on what they discovered.
Conclusion
One thing is for sure, if a material can decrease the weight of a vehicle and improve it in any way and do it in a cost effective manner, we will see new GM products. With the expected redesign of many of its vehicles by 2020, GM will surely use many of these techniques related to material blending to decrease overall weight along with its fuel economy data.
