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Chrysler brings weight savings inside

By: Rhoda Miel

April 24, 2013

DETROIT — When Chrysler Group LLC designed the interior of its revamped Dodge Dart, it was out to prove its status as a reborn carmaker, with a new emphasis on quality and craftsmanship.

The interior did just that, winning awards for the 2013 Dart's styling cues, and praise for a company under new ownership looking to put the old Chrysler and its 2009 bankruptcy behind it.

Now with the auto industry facing another set of hurdles — this time to meet higher fuel-economy standards rather than a severe fiscal crisis — the company is working to balance styling with cutting weight to improve fuel performance.

For the upcoming 2014 Jeep Cherokee, Chrysler pushed its engineers, designers and suppliers to new performance levels, said Mark Sheldon, who oversees cockpit design for Chrysler, during an April 17 discussion on lightweighting interiors at the Society of Automotive Engineers 2013 World Congress in Detroit.

"Weight reduction must be part of designing a vehicle from the very beginning," Sheldon said.

After creating the Dart, Auburn Hills, Mich.-based Chrysler used reverse engineering to take a second look at the upgraded interior and determine how it could have reduced weight without impacting the overall design.

It considered ways to consolidate parts to reduce overall weight, and questioned where to fine-tune structural requirements. The same beam is used to support the steering column and the instrument panel infrastructure, Sheldon noted, but many of the parts hung from that beam do not need the same level of support. Heating and air conditioning ducts do not have the same structural requirements as a steering wheel, for one example.

The development team used lessons learned from both the original Dart development and the engineering study to determine ways to shave weight from the interior of the Cherokee without sacrificing the overall style, he said.

Working with Sabic Innovative Plastics, Chrysler and the material supplier went through 60 different mold-flow studies before selecting the perfect glass-filled polypropylene for an instrument panel substrate that is only 2 millimeters thick, according to Sheldon.

The company is also considering options such as microcellular foaming and alternative structural materials, although Sheldon noted ultralightweight composites such as carbon fiber are not yet ready for full-scale production.

It will also be important to increase development between every step of the supply chain, he and other interior specialists said. Automakers have renewed their emphasis on in-house design, rather than outsourcing some decisions to suppliers. That move allows the companies to put greater emphasis on styling choices while leveraging weight-saving options across multiple vehicle lines, said Tim Boundy, senior manager and GM technical fellow for Detroit-based General Motors Co.

Automakers also can make alterations to the frame or chassis that suppliers cannot, as long as the teams are working together at an early stage. Boundy noted that about five to six years ago, a seat maker found a potential weight savings of more than 10 pounds — but that company was brought in too late to make those changes without also altering the placement and shape of the fuel tank.

Suppliers, meanwhile, can have more knowledge of individual parts, manufacturing improvements or material selection, making it possible to bring to the industry high-volume production using techniques such as in-line compounding, Sheldon said.

As the North American auto industry moves closer to a goal of improving fuel economy to 54.5 miles per gallon by 2025, carmakers will be taking a wider view of all of their mass-reduction options.

"We're going to have to pick and choose which places will get the most funding and development in terms of weight reduction," Sheldon said.