Up to now the moulded carrier and the hollow elastomer seal were manufactured separately and assembled together in a separate process. Previously hollow chamber seals could only be realised by a dedicated extrusion process. This complete procedure is subsituted now by the PIT process within the same tool used for moulding the carrier. This is a two-component process, which chemically bonds an EPDM-bulb seal with a PP-carrier eliminating any risk of the parts becoming detached.

Two-component processes are up to now not known for hollow chamber seals, but only for solid flat lip seals. Unfortunately these cannot achieve either the geometric accuracy or the resistive forces of hollow chamber seals. Due to ever increasing demands in the engine compartments these properties are becoming more and more important for acoustic and thermal shielding as well as keeping rain water out of critical components.

The reliability of these functions depends not only on the seal profile itself, but also on its adhesion to the carrier in the case of a cowl grille for example. A common problem is to ensure a robust fixing for a separate seal. The two-component PIT process eliminates this disadvantage as well as the costs for logistics and assembly of the single parts. This assembly step typically costs more than the savings provided by a separate extrusion process.

"The two-component PIT-cowl grille eliminates assembly and quality costs. Instead of higher parts costs the bottom line shows savings of 10%", says Matteo Piazzi, product manager at Röchling Automotive. "Material and weight savings of 30% come on top. Rising raw material costs thus improve our competitiveness further."

The seal can be manufactured in lengths of up to 1.5 m with constant wall thickness and complex three dimensional shapes fulfilling most design requirements. In addition wall thickness can be varied to suit different sealing or force requirements along the length of the seal. This has advantages for pedestrian protection and hood flutter avoidance. Performance is also improved when complex shapes have to be followed because the seal can follow tighter radii than an extruded seal. The seal compensates for vehicle tolerances of up to 10 mm in line with closing pressure. The seal can be made longer, shorter or equal to the length of the carrier. It can even comprise T- or V-shaped junctions.

After the hard component of the cowl grille (the carrier) is moulded a slider opens to allow the seal cavity to be filled with elastomer material. A projectile then forces the majority of the still liquid elastomer out leaving an accurate elastomer wall behind. The ejected material is recycled for use in the next cycle thus minimising waste. The still warm carrier chemically bonds with the sealant. Piazzi emphasises: "The chemical cohesion lays the foundation for the high durability and long term stability of the two-component part which has been proven by both lab testing and vehicle testing." As both these materials are thermoplastic they can be recycled with no need for any disassembly process.

"Superior quality of the two-component bonding and the hollow chamber sealing - without a cost penalty: These are the advantages of the PIT-cowl grille of Röchling", concludes R&D director Ludwig Huber. This new process has been tried and tested in production in a high volume application on the new Ford C-Max. It also won first place of the US awards of the Society of Plastics Engineers in the body exterior category.