This paper presents the results of an explorative study on the strategies and tactics applied by the mechanical designer during the later phases of the design process. The method chosen for this study is experiment-based, which is appropriate for an in-depth examination of the designer's activities. Six experiments have been run based on three dimensions: 1) the carrying out of basic design tasks consisting of the designer's strategies and tactics; 2) use of rules, principles and guidelines; and 3) consideration of additional factors. The analysis of the experiments is based on the verbal protocol analysis method.Although the designers individually showed different approaches, the strategies adopted by the experts presented a similar pattern. Some powerful tactics but also some weaknesses have been identified: the experts reasoned very early in the process in terms of concrete parts and components and thus rapidly solved interface problems; on the other hand, the evaluation and check activities were often considered as secondary.

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Generative product design systems used in the context of mass customization are required to generate diverse solutions quickly and reliably without necessitating modification or tuning during use. When such systems are employed to allow for the mass customization of product form, they must be able to handle mass production and engineering constraints that can be time-consuming to evaluate and difficult to fulfill. These issues are related to how the constraints are handled in the generative design system. This article evaluates two promising sequential constraint-handling techniques and the often used weighted sum technique with regard to convergence time, convergence rate, and diversity of the design solutions. The application used for this purpose was a design system aimed at generating a table with an advanced form: a Voronoi diagram based structure. The design problem was constrained in terms of production as well as stability, requiring a time-consuming finite element evaluation. Regarding convergence time and rate, one of the sequential constraint-handling techniques performed significantly better than the weighted sum technique. Nevertheless, the weighted sum technique presented respectable results and therefore remains a relevant technique. Regarding diversity, none of the techniques could generate diverse solutions in a single search run. In contrast, the solutions from different searches were always diverse. Solution diversity is thus gained at the cost of more runs, but no evaluation of the diversity of the solutions is needed. This result is important, because a diversity evaluation function would otherwise have to be developed for every new type of design. Efficient handling of complex constraints is an important step toward mass customization of nontrivial product forms.

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Complex product form generation methods have rarely been used within the field of industrial design. The difficulty in their use is mainly linked to constraintssuch as functionality, production and cost -that apply to most products. By coupling a mathematically described morphology to an optimisation system, it may be possible to generate a complex product form, compliant with engineering and production constraints. In this paper we apply this general approach to the designing of a bookshelf whose structure is based on Voronoi diagrams. The algorithm behind the developed application used here is based on a prior work submitted elsewhere [1], adapted to the bookshelf problem. This second example of product form generation, which includes specific constraints, confirms the relevance of the general approach. The handling of complex morphologies is not straightforward. Consequently, an explorative study on that theme has been performed. A user interface has been developed that allows for designing a bookshelf based on Voronoi diagrams. The user interface was subsequently tested by peer designers. The results suggest that user attitudes diverge: one faction preferred maximum freedom of creation, that is, maximum control of the form creation process; the other faction wanted the application to generate a bookshelf based on their functional needs (e.g. adapt to the number and types of objects to be stored) and would ask for a "surprise me" effect for the final solution. IntroductionAlthough complex -mathematical or nature-inspired -form generation methods have long been employed in the field of architecture [2, p. 137], this has rarely been the case in industrial design. One barrier for such development in the latter discipline is the multitude of constraints linked to A. Nordin et al.2 the form-giving of products; surfaces are often functional, the artefacts are produced in several exemplars -meaning that the product form must be modified to suit production systems; cost control is consequently important; finally, engineering constraints must also be respected. Another obstacle may be the lack of educational initiation in industrial design.However, the situation is beginning to evolve; the ongoing digitalisation of the entire product design activity simplifies access to form generation tools whilst digital fabrication facilitates the production of physical prototypes. This digitalisation should allow for a much tighter integration of industrial design, engineering and production. Last but not least, one can sense an evolution of the by and large static relationship between the consumer and the product. There is an increasing desire to participate in the designing of products and the potential experiences consumers will share with them. As put forward by Friebe and Ramge [3], the upsurge of independent fashion labels, crowdsourcing initiatives or co-working spaces indicates the demand for consumer empowerment. This need for co-creation, implemented already in textile [4] but also in more advanced consumer goods busines...