Thermoplastic vulcanizates (TPVs) are known for giving a resilient, soft touch to automotive interiors.
But the molding of new console liners and cupholder inserts for 2003 Ford Expeditions and Lincoln Navigators posed difficulties for designers. Tools for conventional TPVs wouldn't let air escape from the mold, forming voids in the parts. In addition, some of the more complex console liners were tough to remove from the mold cores.
A new 75 Shore A TPV, Respond SX70, from Solvay Engineered Polymers, Auburn Hills, Mich. (www.solvay.com), helped solve Ford's mold-fill and release problems for console liners and cupholder parts. The material also meets Ford's low-fogging and soft-touch specs. Its flow properties and low affinity for water absorption reportedly gives parts better-looking, more-consistent matte surfaces, and needs no premold drying. It easily colors, so there's no problem meeting Ford's JA6A black color spec.
For the two most complex console liners, however, parts and tooling needed changing. These liners have divided sections for CDs, cassette tapes, and a remote control for the entertainment system. Ford pinpointed key design details that hampered mold fill and part removal. Ribs separating compartments were originally designed to act as internal runners for the material during molding. "The flow properties of the TPV materials, along with the orientation and original dimensions of the dividers trapped air in sections of the mold," explains CAE specialist Andrew Johnson. Solvay worked with the molder, Visteon Carplastic, Monterrey, Mexico (www.visteon.com), to redesign the parts and the mold: reducing rib height, redirecting slots, and altering divider wall thicknesses. They also changed gating locations, redirecting flow so air no longer gets trapped inside parts. A final tool modification was adding air-injection to help get parts out of the mold quickly.
The console bin liner and cupholder inserts for the Ford Expedition and Lincoln Navigator are reportedly the first automotive parts to use Respond TPV from Solvay Engineered Polymers. The materials mold easier and let parts pop out of the mold quicker than previous TPVs.