The Analysis and Comparison of Cup-Holder and Ashtray Designs Using the Principle of Axiomatic Design 2004-01-0809

The location of cup-holders and ashtray on vehicle instrument panel can affect instrument panel appearance as well as cup-holder and ashtray functionality. Axiomatic Design was used to analyze and compare the designs of cup-holders and ashtray for three 1999 model-year full-size pickup trucks. The customer domain was mapped into the functional domain by specifying customer needs in terms of functional requirements (FRs) and constraints (Cs). Design parameters (DP) were identified in the physical domain for each functional requirement. Design matrices were then defined to characterize the product design [1].

The ashtray and cup-holders are treated as one sub-system of the instrument panel. There are two functional requirements in this sub-system at the highest level: storing ash/garbage and holding cups. The corresponding DPs are: ashtray assembly and cup-holder assembly. Through zigzagging to decompose to the next level, one of the designs was found to be coupled. At this level, the free space required for holding cups was found to affect the opening of the ashtray. When the cup-holders are holding cups, the ashtray can not be opened. This coupled design is obviously a bad design because the functions of cup-holders and ashtray can not be achieved at the same time but customers sometimes do need to use both functions at the same time. Other designs are not coupled and therefore are better designs.

It is obvious the designers for this coupled design have not applied Axiomatic Design principles. Therefore, the design is a bad design and it lowers the customer satisfaction.

The analysis and comparison were based on only two basic main functions of the ashtray and cup-holder subsystem: storing ash/garbage and holding cups. In fact, there are many more functional requirements for this subsystem: providing flexibility to different cup sizes, providing stability for cups, providing the stability for the whole cup-holder assembly and ashtray assembly, and providing ease of access to driver and passenger and so on. We are not discussing those details in this paper.