R-RIM Door Panels, New single-material Solutions

03 May 2001

The development of new technologies and the use of ever more performing materials have enabled the car industry to free itself of design constraints and come up with more sophisticated, advanced solutions. Over the past few years, car interior and exterior have gone through design transformations made possible by the presence of new materials and engineering solutions capable of satisfying the most diverse design needs.

Safety and aesthetic considerations contributed to the success of the S-RIM technology for the production of car door panels. Today, the same considerations are best satisfied by the use of R-RIM, a technology which was heavily used by FIAT in the past but never caught on with other auto-makers due to structural limits in the manufactured piece.

The R-RIM technology was developed in the 1980’s by Cannon Tecnos and Strapazzini (Lear Group) and was used, until a few years ago, to manufacture door panels for Lancia cars (FIAT Group). A PVC or ABS skin was reinforced through a closed-mould injection of fibreglass-filled polyurethane. Compared to other door panel manufacturing processes, like sheet or injection moulding, R-RIM and S-RIM moulding allow for significant design freedom. When compared to S-RIM, R-RIM shows higher cycle time due to the closed-mould injection technique and ensures high surface quality in the piece with no wettability of the reinforcing fibres. By contrast, the degree of shock resistance of R-RIM door panels is much lower than that of S-RIM panels due to the use of short fibres. This aspect, which had an impact on the overall safety and crashworthiness of the vehicle, is the reason why until today S-RIM has been preferred to R-RIM.

Yet, the evolution of car design and the introduction of lateral airbags on contemporary vehicles have helped R-RIM make a comeback.

Low shock resistance has turned from drawback to asset. Indeed, latest-generation vehicles feature side protection bars built into the doors so that door panels no longer need to serve simultaneously an aesthetic, functional and protective purpose. In fact, door panels are now required to smash easily on impact to allow lateral airbags to burst out and perform their protective action. R-RIM has therefore been reconsidered as the most appropriate solution to this requirement: several European auto-makers are now using this technology to produce door panels for their new car models.

In addition to PVC or TPO skins, polyurethane skins are going to be used, thus creating single-material panels. Cannon Tecnos has recently developed, in co-operation with a major raw material supplier, a new moulding technology to produce polyurethane skins less than 1 mm in thickness. Until today, the only production process used to make polyurethane skins has consisted of spraying polyurethane in the mould, resulting in high cycle time and skins of irregular thickness. The new moulding process overcomes both these limits.

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