Thyssen Umformtechnik Leichtbau Entwicklungs GmbH (TULE) has designed and built the roof and side wall modules for DaimlerChrysler?s "Alu-Sprinter?. The van concept vehicle that DaimlerChrysler is presenting at IAA Nutzfahrzeuge offers 200 kilograms more payload and 12% more cargo space than the comparable steel Sprinter. TULE is contributing to this with weight reductions of 40 percent for the roof and 45 percent for the side panels.

The Brackwede plant of Thyssen Umformtechnik + Guss GmbH is also involved in the production of the standard Sprinter van, making sheet metal stampings for roof, side panels, doors, fenders and large parts of the floor. The job facing the development engineers of sister company TULE in Ludwigsfelde was to adapt the design of side panel and roof so as to make optimum use of the weight advantages of aluminum while minimizing the cost disadvantages.

The most important change versus the standard Sprinter is that the roof and side panels get their stiffness and strength from a spaceframe made of aluminum extrusions onto which molded aluminum body panels are mounted. This design saves investment costs for press tooling and is therefore particularly suitable for low-volume production. In the production Sprinter the support structure consists of a few large steel panels which have to be produced in large and costly dies.

The skin for the roof and side wall of the Alu-Sprinter consists of six relatively small aluminum panels that can be molded using much cheaper dies. Also, together with the DaimlerChrysler designers TULE developed shapes for the panels which can be produced with little forming effort. The upper skin panels of the side wall are made of sandwich sheets with a plastic interlay which are even lighter than conventional aluminum sheets.

The spaceframe design, which can be easily adapted to vehicles of different length, wheel base and height, also has a positive impact on cargo space: The side wall of the Alu-Sprinter is only 45 millimeters thick, around 20 millimeters thinner than on the production version. TULE?s engineers achieved this effect by using molded sheet fasteners to connect the extrusions in the spaceframe rather than laying them over one another at the points of intersection. An additional benefit is that seat-track rails are let into the extrusions, allowing shelves, clothes rails, nets or belts to be installed using standard fastening elements.

TULE has minimized production costs by standardizing most of the parts and assemblies used: the same type of extrusion is used for both the vertical and horizontal braces of the spaceframe. Simple fastening techniques such as riveting, clinching and adhesive bonding keep assembly costs down. The tooling for the panels can be easily adapted to the production of vehicles with different lengths and wheel bases.

Thyssen Umformtechnik Leichtbau Entwicklungs-GmbH and the Brackwede plant of Thyssen Umformtechnik + Guss are part of the business unit Body of ThyssenKrupp Automotive.