Plastic not steel

A steel lattice has been replaced by a moulded structural retainer in a new instrument panel for the Dodge Dakota

A fully integrated structural instrument panel developed for the 1997 Dodge Dakota in the US incorporates several novel design techniques. Not only is the panel a departure from the more traditional steel lattice, being based instead on a structural retainer moulded from Pulse PC/ABS from Dow, the three piece structure was also vibration welded.

Spearheaded by Chrysler, the development was a collaborative effort between the company and two of its major suppliers, Textron Automotive and Dow Automotive.

Climate control has been improved over earlier models, including 30% better defroster performance, double demister flow, and a better fit than conventional instrument panels. Buzz squeak and rattle has also been reduced.

A centre panel provides the primary structure of the instrument panel. All component parts are referenced to this part, which encompasses the driver side lower centre close-out panel and the passenger side glove box surround. The passenger side air bag mounts directly to the side without steel reinforcement.

The front panel mounts to the body-in-white and forms the backbone of the structure. It is the first part forward in the vehicle and consists of a door-to-door sweep of the climate control ducting with various moulded-in features. When the front and centre panels are joined, they form a two-piece, air-tight monococque construction for structure and stiffness which is greater than that of conventional steel IP construction.

The centre/front panel combination also serves as the air distribution duct connecting the exhaust opening in the HVAC unit and the air outlets on the rear face of the instrument panel. Fresh air for the windscreen defrost is delivered through manifolds and outlets formed by the assembled mouldings. The cross section is optimised to provide continuous distribution of structural stiffness along the duct while maintaining the airflow.

The rear panel is vibration welded to the centre panel assembly. The panel also mounts the cluster, climate control head, radio, demister adapter, air flow distribution deflectors and trim plate. Some surfaces on the panel required weld beads at 45 degrees compound angles.

The glove box assembly, moulded with Pulse resin, went from a three-piece to a two-piece design, saving the cost of an entire tool. The glove box bin and ribbed inner structure are moulded in a single piece with a hinge. The assembly also has moulded-in hinges for attachment to the instrument panel, further minimising assembly steps.

Steel plates and roll-up end brackets were located to assist in directing the load to the upper structural duct that distributes the load to the body in white. An upper pad and trim panels complete the structural IP assembly.

In terms of meeting Chrysler’s goals, the new instrument panel has enabled a weight reduction of about 6lb/vehicle and 50% fewer parts.

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