ThyssenKrupp Stahl AG and Nothelfer GmbH, a company from the Technologies segment of the ThyssenKrupp Group, have jointly developed a new modular door concept. It was benchmarked to the rear door of a production car. The new, modular door is 1.2 kilograms lighter than the benchmarked model and costs significantly less to manufacture and assemble. The concept also offers new possibilities in terms of seal assembly and parts logistics.

The door consists of two modules: the outer module is an assembly of outer panel and connecting part. In the connecting part, the functions of hinge reinforcement, side rail reinforcement and side impact protection are combined in one high-strength sheet metal part. The part is made of a tailored blank consisting of the TRIP steel (Transformation Induced Plasticity) H400T in 1 millimeter thickness and the micro-alloyed steel H240M in 1.6 millimeter thickness. The outer panel uses a 0.48 millimeter thick sheet of dual-phase steel H300X. Additional support braces with the connecting part reduce free sheet metal area and ensure the necessary dent resistance of the outer panel. Because the complete assembly lies outside the lowered side window, the complexity involved in forming individual parts is reduced.

The inner panel and the latch component form the inner module. It includes the window frame and holds all the internal components such as lock and window opener. One special feature is a channel which accommodates the door seal without the need for adhesive. This solution is not only cost-effective, it also allows the future use of dirt-repellent paints. Another highlight is that the sheet metal parts of the inner module are joined by laser stitch welding, which offers greater stiffness than conventional resistance spot welding, which is also possible. The modified assembly of the door internal components also means the hole pattern of the inner panel can be optimized to better resist stresses.

The modular approach means that door production and door assembly can be separated. The outer module is assembled to the body in the body-in-white shop and painted with the body. It is disassembled as usual at the beginning of vehicle assembly. The inner module could be made by a supplier, who pre-assembles it with all internal parts and delivers it just-in-time. It is painted in a neutral color to avoid color matching problems. Both modules are bolted together in an automated assembly cell.

The parameters for the development of the modular door were the data of the benchmark model for window frame stiffness, torsion, eigen modes, door lowering, and dent resistance. The project work carried out by the ThyssenKrupp Stahl engineers covered the complete process chain including conception, design, FEM analysis, manufacturability studies and prototype production.

Contact:
ThyssenKrupp Steel AG
Dietmar Stamm
Tel.: +49 203 / 52 - 2 62 67
Fax: +49 203 / 52 - 2 57 07
e-mail: dietmar.stamm@tks.thyssenkrupp.com

Bernd Overmaat
Tel.: +49 203 / 52 - 4 51 85
Fax: +49 203 / 52 - 2 57 07
e-mail: bernd.overmaat@tks.thyssenkrupp.com