From Polylithic to Monolithic: The Design of a Lightweight, Stiffened, Non-Rotational, Deep-Drawn Automotive Product

The transition from polylithic (composed of many parts) to monolithic (one part) design in automotive components presents an opportunity for a reduction in part count, weight, processing routes, and production time without compromising performance. The traditional design approaches for rooftop tents assemble various sheet metal and extrusions together using different joining processes such as welding, adhesive bonding, bolting, and riveting. This is often associated with disadvantages, such as increased weight, high production time, and leaking joints. This research, therefore, presents the development of a monolithic, lightweight, stiffened, non-rotational automotive rooftop tent that is manufactured via the deep-drawing process. An onsite company case study was conducted to analyze the polylithic product and its production process to determine its limitations. This was followed by the design of a lightweight, non-rotational monolithic product whose purpose is to eliminate the identified disadvantages. The stiffness geometries were developed to enhance the overall structural integrity without adding unnecessary weight. The Analytic Hierarchy Process (AHP) was used to analyze and evaluate alternative layouts against criteria such as complexity, tool design, symmetry, rigidity, and cost. Simulations conducted using NX 2024 software confirmed the effectiveness of this design. The results show that the monolithic rooftop tent has a comparable stiffness performance between the lightweight, monolithic rooftop tent and the heavy, polylithic rooftop tent. At the same time, the part count was reduced from twenty-three (23) single parts (polylithic) to a one (1) part (monolithic) rooftop tent, the weight was reduced by 15.6 kg, which translates to a 30% weight reduction without compromising the performance, processing routes were reduced from eight (8) to three (3), production time was reduced by 120 min, and leaking was eliminated. It can, therefore, be concluded that the design and manufacturing of monolithic rooftop tents leads to a lighter and stronger product.