Fish trap model

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How can you generate form concepts?

“The Fish Trap model (see figure 1) is a method for generating and developing a form concept for a product up to sketch plan. As such, the approach is intended to cover the form-creation phase. The method is prescriptive, meaning that it indicates how a concept should be developed” (Muller, 2001, pp 196). Motivation for the development of this method rose from experiences with students; they were confronted with the difficulty to just start designing and to give direction to their search for design solutions. Methods that may steer this form creation phase were not available.

The Fish-Trap Model in the Product Design Process

The Fish-Trap Model starts at the stage of the design process when a basic structure of the functional components required for the primary function fulfilment is known. According to Muller the starting point in the Fish-Trap Model is an intermediate stage between the function structure and the solutions principle and ends with the stage of the material concept (sketch plan or preliminary design).

The Fish Trap Model process in short

Development of Criteria

Figure 1: The ‘Fish Trap’ Model describing the form-creation phase up to the sketch-design (Muller, 2001)

Design criteria form an important starting point for the exploration of possible concepts. In this model they are derived from a visual exploration and analysis of the context (intended users, usage and the environment). The criteria are developed simultaneously with the development of the concepts (see fig. 1). Muller emphasises the role of visio-spatial thinking, imaging and exploration by sketching that is essential to develop the criteria. Therefore the exploration is done by means of both visualisation techniques such as sketching & collages and three-dimensional sketch models or mock-ups.

A Systematic Process: Levels

The Fish-Trap model is a systematic process of designing a product form. The model is systematic because it forces the designer to explore alternatives on three subsequent levels of increasing detail and meaning: (1) topological level, (2) typological level and (3) morphological level. Exploring alternatives on each of these levels yields three types of concepts: (1) a structural concept, (2) a formal concept and a (2) material concept. On each of these levels, large variations of design alternatives (or variants) are generated, clustered in groups and evaluated. After a selection of the most promising concepts a new generation phase starts on a more detailed level.

Converging, Diverging and Categorisation

In figure 1, “the Fish-Trap Model is depicted in two ways; on the right, according to the normal representation of the process by phases, on the left, through a diagram to visualise the divergence and convergence, and to indicate the occurrence of various solution types at each concept level. Because the last depiction shows a visual analogy with a fish-trap which can be metaphorically understood as ‘to catch’ a final solution, the method is called ‘fish-trap model” (Muller, 2001, pp.197).

The generation of variants is a diverging process and should be done with an open attitude and the curiosity about new possibilities. After creating many possible variants the diverging stage can start; the variants are categorised according to their solution type. Then, one or more representations of a category will be developed into a concept. Those concepts, representing a specific solution type, will be evaluated against the criteria. One or more concepts need to be selected for the next diverging stage on a new, more concrete, level.

Topological Level: The Structural Concept

Figure 2: Structural concept (from student report)

For the development of a structural concept (figure 2) you need to define the basic functional components in advance. These components, or ordering elements, can exist of the technical parts that are needed for the working principle (such as batteries and printed circuit board) or the parts that represent the functions that are needed for product use (such as visual feedback and one-hand control). With the components you can compose as much as possible variants that differ compared to their topology; the spatial ordering of the components. This can for instance result in an ‘open’, a ‘compact’ or a ‘horizontal structural’ variant. In his book Muller presents an overview of possible ways of ordering and the meaning they may articulate (Muller, 2001, pp.122). After this stage of diverging, variants of the same ‘type’ need to be clustered (converging stage) and a representative variant should be developed into a structural concept. Selection of one or more structural concepts will be done by evaluation with the criteria. Important is that the structural concepts need to be ‘put into context’ and evaluated by imagining the possibilities for the interaction with the intended user. By doing so new ways for the product-user interaction may appear.

Typological Level: The Formal Concept

Figure 3: Two formal concepts (from student report)

For the development of a formal concept (figure 3), that has a concrete form of ‘flesh and blood’, we start with one or more selected structural concepts. In this stage we focus on the global form of the concept. A variety of possible geometric constructions lead to different classes of form; form typologies. In order to explore freely the possible form solutions, in the diverging stage, not so much attention should be paid to the form criteria and to production requirements. Though it is useful to explore forms in relation with their possible technical constructions since they will co-define the final form (e.g. scale division of an injection moulded body, open skeleton construction from tubes). Exploration takes place by sketching. In the converging stage the sketches need to be evaluated on their viability (related to construction, integration of components, needed material) and categorised in groups with the same form type. During this stage improvements can still be made, together with textual explanation and comments. Subsequently each form type needs to be evaluated against the criteria. Promising solutions should be further developed into one or more formal concepts, which clearly show the formal features and the typical intended interaction with the intended users. This interaction includes the abstract meaning that the design may elicit (such as ‘cool’, ‘childish’, ‘playful’).

Morphological Level: The Material Concept

Figure 4: Aspect of material concept (from student report)

The development of a material concept (fig. 4) includes the further materialisation of one or more formal concepts. A diverging process of exploration takes place again, looking for solution on a rather detailed level, concerning the morphology of the variants. Manufacturing, assembly, specification of materials, finishing, texture and colours should be explored and in the converging stage defined. And although the number of alternatives may be narrowing down slightly, feedback to the criteria is also in this stage of importance.

Remark: This explanation of the Fish-Trap Model is in short and does not honour the richness of it. Please, read about this model and more in Wim Muller’s book.

References and Further Reading

  • Muller, W. (2001) Order and Meaning in Design, Utrecht: Lemma.
  • Muller, W. (1997, 2nd ed.) Vormgeven: ordening en betekenisgeving, Utrecht: Lemma.
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