Academic journal article International Journal of Design

Impacts of Geometrical Manufacturing Quality on the Visual Product Experience

Academic journal article International Journal of Design

Impacts of Geometrical Manufacturing Quality on the Visual Product Experience

Article excerpt


When adapting a product design for manufacturability and developing it into detail, the initial design intent may be distorted. Further, once attaining a fully defined product, assigned tolerances and production capacity determine the level of variation affecting each manufactured product, resulting in unit-to-unit differences in colour and geometry. Here, focus is set on visible geometrical deviations resulting from manufacturing and assembly variation. Managing the effects of geometrical variation is not only a matter of selecting the appropriate materials and manufacturing processes and attaining the provided tolerances. The product geometry can induce variation to a varying degree. For instance, the degree to which sheet metal parts on car exteriors suffer from spring-back deflection depends on the part geometry. The part geometry also sets the prerequisites for locator placement, controlling assembly stack-up effects and variation amplification (Söderberg & Lindkvist, 1999). Further, the effects of variation on product experience are appearance-dependent. Geometrical variation is often apparent through the relationships between visible components (i.e., the split-lines), in terms of non-parallelism, misalignment, or uneven gap sizes. Depending on the colour, form, structure, and surfaces of different designs, deviations are varyingly perceptible to the onlooker (Figure 1). This is referred to as a product's visual sensitivity to geometrical variation (Forslund & Söderberg, 2010). Therefore, achieving a geometrically satisfactory product is an iterative process of product adaptation with several trade-offs to be made along the way. It is important to make adequate assessments of the significance of achieving a good geometrical result in relation to an appealing design concept from other perspectives. The actual role of manufacturing quality for the consumer's product experience has however gained relatively little attention (Crilly, Moultrie, & Clarkson, 2004). Product experience has been defined as "the entire set of effects that is elicited by the interaction between a user and a product" and has been classified into aesthetic pleasure, attribution of meaning, and emotional response (Desmet & Hekkert, 2007). It may seem straightforward that reducing the number of perceivable defects in a product ensures an enhanced product experience. It is also close at hand to describe appearance conformance as a type of "expected quality" as described in the Kano model (Kano, Seraku, Takahashi, & Tsuji, 1984).

[Figure omitted, see PDF]

Figure 1. Appearance-dependent visibility of geometrical deviations where product A reveals deviations while B has a forgiving design.

A main problem, however, is that all manufactured components deviate from their intended (nominal) state on a continuous scale where the difference between defect and conforming units are not always evident. All produced units should be seen as afflicted by an amount of "noise" that can influence customers to a varying extent. In relation to recent research on product experience, (see for instance Creusen & Schoormans, 2005; Dagman, Karlsson, & Wikström, 2010; Desmet & Hekkert, 2007; Jordan, 2000; Schifferstein & Hekkert, 2008; Warell, 2008), where the sensory and emotional experience of products has been addressed in depth, descriptions of what dimensions of the product experience that are influenced by this "noise" are relatively scarce.

Monö (1997), describing product design as a process of producer-consumer communication, pointed out that flaws in design and manufacturing could distort the message intended by the designer (see also Crilly, Maier, & Clarkson, 2008; Forslund, Dagman, & Söderberg, 2006). However, apart from distorting a message, it has been claimed that visible manufacturing quality has a special function in communicating functional quality. For instance, Debrosse, Pillet, Maire, and Baudet, (2010), presenting an analysis of the sensory evaluation process in a number of companies, point out that while for some products, such as luxury goods and furniture, "a quasi perfect aesthetics is its own criterion;" for other products, visible deviations can "transmit the global quality level of the whole product" (Debrosse, et al. …

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