Increased Visual Quality through Robust Split-Line Design

Licentiate thesis, 2005

In the early phases of the product development process, the initial product geometry can be a non-divided shape, just a shell. This initial product geometry has to be divided into individual parts in order to manufacture and fulfil the functionality of the product. In the case of automobiles, these parts can be fenders, doors, hoods, etc. The design of the parts is influenced by several aspects, like design language, geometrical dimensioning, crash safety, wind resistance, etc. The decisions regarding how to divide and design the parts are made in multidisciplinary teams. The final appearance of the spatial relations between the parts, i.e. the split-lines, in an assembly affects the quality appearance of the product. This in turn influences the sales of the product. By supporting the product development process with methods, tools and guidelines, the quality of the final solution will improve. The focus of the presented research has been on how to split the initial product geometry in order to achieve a geometrically and visually robust solution. In other terms, it has been on how the split-line shall be designed and placed in order to achieve as geometrically and visually robust solution as possible. Geometrical robustness aims at the dimensional and functional aspects of the product. Visual robustness is more concerned with the aesthetic aspects of the product. A geometrically and visually robust solution suppresses part and assembly variation. This leads to a decreased geometrical output variation, the variation between parts the customer sees. A geometrically robust solution often results in a visually robust solution. A geometrically sensitive solution, on the other hand, can be made visually acceptable in some cases by controlling the position and the direction of the split-line. Different areas are more or less sensitive for the eye. The research results have contributed to an enhanced knowledge and a supporting tool in the area of geometrical and visual robustness. The tool supports the division of initial product geometry with respect to geometrical robustness. The enhanced knowledge enlightens how different assembly aspects influence the final result when assembling. There is also a contribution concerning customers’ and the industry’s attitude regarding the visual quality appearance of split-lines. It concerns more the aesthetic aspects of the split-line design. The conclusion of the presented research project is that the division of the initial product geometry, in order to achieve a geometrically and visually robust solution, is influenced by many aspects. These aspects can sometimes be antagonists and there have to be a compromise between them. Also, the tool presented does calculate and visualize robust areas between two geometries to be split and this result can hopefully be used as a support in the product development process. The customer’s consider high visual quality of split-lines as important and that narrow split-lines is of importance for the perceived quality but there is other factors that is influencing the quality appearance of split-lines. By using the presented tool and by using the knowledge, gained from this research project, the chances of creating products with high visual quality will increase with decreased cost and time for the product development process.