BMW Group sought help from two suppliers to reduce the weight of one of the Mini Countryman's biggest structural parts.
The result: an instrument panel carrier made using a foamed structural plastic, shaving 15 percent from its weight.
Now the suppliers wonder if the process can produce other high-quality interior parts.
BMW partnered for the Countryman project with interior systems producer International Automotive Components Group and chemical supplier Saudi Basic Industries Corp.
"We add value when we are involved upfront and we're able to influence design, process and material selection," Scott Fallon, Sabic's global automotive business leader, told Automotive News.
IAC's contribution was Coreback, an injection molding process that allows a chemical foaming agent to be added to the resin during molding. The result is a product that has stiffness, reduced weight and greater flexibility in design.
Sabic joined the team as IAC's close partner, said Frank Schumann, IAC's manager of the advanced material and process group Europe.
"Sabic has been one of our major partners for instrument panels for years," Schumann said. "We brought our engineering competencies and they brought the hardware side."
Battling warpage
Sabic used computer-aided engineering to create a process that used a specialized chemical foaming agent in existing injection molding machines. The process provided a major cost advantage, Fallon said.
"Types of mechanical foaming require more designated equipment, but in this case we can use existing injection molding machines," Fallon said. "It also helps with physical performance by getting better impact and stiffness."
Instrument panel carriers are typically molded to be 2.5 to 2.8 millimeters thick. With Coreback, the chemical foaming agent is injected into a cavity 1.8 millimeters thick. During processing, a chemical foaming agent is added to the resin, then the mold is opened to a maximum of 4 millimeters to generate a foam layer in the middle. That then creates what IAC terms "industry leading stiffness-to-weight performance."
The suppliers still faced a common injection molding problem: warpage.
Sabic's computer-aided engineering enabled the supplier to create and test virtual foam prototypes, cutting prototyping costs.
"This enabled building the mold correctly the first time," Fallon said.
Cosmetics
Schumann considers injection molding a large structural component with little warpage to be a major advancement. Now, he said, IAC and Sabic's task is a cosmetic one. The partners want to use the process to produce visible vehicle interior parts rather than unseen structural parts.
That will mean perfecting the foaming agent to higher quality standards. The foam products tend to streak, which doesn't matter in structural parts but is unacceptable in visible components.
If they can perfect the foam-based parts' appearance, they see weight-saving possibilities in vehicle interiors.
"All these plastic parts all around your car could be made much lighter, stiffer and safer with this kind of technology," Schumann said. "So it's finding the sweet spot of the process in how to mold plastic parts with a streak-free surface."
At NPE2018, Sabic will exhibit in booth S19001.
