NORTHVILLE, Mich.—Frameless door systems are gaining increased levels of adoption in the high-end automotive market, driven partly by trends around sustainability and electrification, Cooper-Standard has reported.

While frameless designs have been around for many years, applications were initially restricted to niche, sporty two-door coupes and convertibles before showing up on four-door coupes.

Compact doors that eliminate the traditional upper frame "have been trending in the luxury vehicle market," where they offer a unique, clean look, according to Cooper-Standard.

"The transition between the smooth door glass and b-pillar does not only look aerodynamic, but also offers functionality with reduced wind turbulences and air drag that commonly creates interior cabin noise," the company said.

Cooper-Standard claims to be one of the pioneers of frameless sealing for these new door designs, having "previously equipped many generations of car models with these attractive systems."

Over the past few years, it added, "we have developed and produced close to 50 frameless programs for 16 different automotive brands with many more under development."

As well as aesthetic appeal, frameless sealing systems must meet demanding performance requirements, including water leakage prevention and protection from wind, dust and noise.

These are some of the most complex vehicle sealing systems to produce, said Cooper Standard, adding that "the amount and complexity of different moldings requires a team of experts, detailed planning and perfect execution."

To illustrate the design concepts, Cooper Standard provided the following example for a four-door sedan, with details and supporting diagram (further below):

Mirror booth: Typically made from one extrusion profiles (EPDM rubber and/or TPV) with an injection molded mucket (EPDM rubber or lubricated TPV). Uses either spray coating, flock or co-extruded low friction material on surfaces contacting glass.

Seals mounted on vehicle body: Typically made from multiple EPDM rubber extrusion profiles joined via injection molded EPDM rubber corners. Parts are sprayed with a high abrasion & anti squeak/itch coating. Part is pushed onto flange and/or into retainers for retention.

Seals mounted on vehicle doors: Typically made from one or more extrusion profiles (EPDM rubber and/or TPV) joined via injection molded corners (EPDM rubber or TPV). Parts are sprayed with a high abrasion and anti-squeak/itch coating or use a lubricated TPV material. Parts are attached via plastic "push pins."

Beltline seals: Similar to non frameless vehicle. Typically made from one extrusion profiles (EPDM rubber and/or TPV) and sometimes covered with a cap (painted, SS or AL). Surface contacting window is flocked.

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