Prototyping is interwoven with nearly all product, service, and systems development efforts. A prototype is a pre-production representation of some aspect of a concept or final design. Prototyping often predetermines a large portion of resource deployment in development and influences design project success. This review surveys literature sources in engineering, management, design science, and architecture. The study is focused around design prototyping for early stage design. Insights are synthesized from critical review of the literature: key objectives of prototyping, critical review of major techniques, relationships between techniques, and a strategy matrix to connect objectives to techniques. The review is supported with exemplar prototypes provided from industrial design efforts. Techniques are roughly categorized into those that improve the outcomes of prototyping directly, and those that enable prototyping through lowering of cost and time. Compact descriptions of each technique provide a foundation to compare the potential benefits and drawbacks of each. The review concludes with a summary of key observations, highlighted opportunities in the research, and a vision of the future of prototyping. This review aims to provide a resource for designers as well as set a trajectory for continuing innovation in the scientific research of design prototyping.

Engineering idea generation is a crucial part of new product development, and physical modeling is a widely used tool. Despite the physical models’ popularity in the idea generation process, little is known about their effects on design cognition. The existing literature provides contradicting guidelines about their use in the design process. Product design firms call for the frequent use of physical models, but some studies suggest that physical models induce design fixation. The psychological literature indicates that physical representations, by supporting designers’ mental models of physical phenomena, might lead to more feasible designs. The advantages and disadvantages of physical models as idea generation tools need to be clarified to help designers decide when and where to implement them. Based on prior studies and anecdotal evidence, two hypotheses are tested: (1) physical models supplement designer’s mental models and (2) physical models induce design fixation. Two between-subject idea generation experiments with novice designers are conducted to evaluate these hypotheses. In the first pilot experiment, the participants generate ideas in three conditions: sketching only, building, and building and testing. This study is followed by a second experiment, in which a new condition called constrained sketching is added. In each condition, participants use the representation implied by the name of the condition. The percentage of ideas satisfying all design requirements indicates the physical models’ effect on the designers’ mental models. Novelty and variety are used as metrics for design fixation. The percentage of functional ideas quantified shows significant variation across the sketching and building conditions, whereas novelty and variety show no differences. These results support the argument that physical models supplement novice designer’s mental models. No evidence of fixation is observed, which contradicts the results of the prior observational studies. Hypothesized reasons for the apparently contradictory results are also presented.

Engineering idea generation plays a vital role in the development of novel products. Prior studies have shown that designers fixate to the features of example solutions and replicate these features in their ideas. This type of fixation acts as a major hindrance in idea generation, as it restricts the solution space where designers search for their ideas. Building upon the study by Linsey et al. [2010, “A Study of Design Fixation, Its Mitigation and Perception in Engineering Design Faculty,” ASME Trans. J. Mech. Des., 132, 041003], this study hypothesizes that designers fixate to example features and this fixation can be mitigated using certain defixation materials including alternate representations of the design problem. To investigate this, the experiment conducted by Linsey et al. [2010] with engineering design faculty is replicated with novice designers. Participants generate ideas for a design problem in three groups: one group working with a fixating example, a second group working with the same example along with alternate representations of the design problem and a control group. The obtained results show that both the novice designers and design faculty fixate to the same extent, whereas the defixation materials have differential effect on the two groups. This result indicates that design researchers need to be very careful in developing methods and guidelines that are formulated and tested with studies on novice designers. The effectiveness of such measures may vary with the level of expertise of the designer.

Physical models are very commonly used as tools for engineering idea generation, yet the guidelines in literature about their implementation are conflicting. A prior study has shown that physical models have the potential to supplement designers’ erroneous mental models; whereas a few observational studies have shown that physical models can cause a high degree of fixation under certain circumstances. At the same time, a previous controlled study fails to show the presence of fixation in idea generation with physical models. This study hypothesizes that prior observed fixation in physical modeling is due to Sunk Cost Effect, which is the reluctance to choose a different path of action once significant money, time or effort is invested in present one. Consistent with the prior study, this study also hypothesizes that physical models supplement designers’ mental models. These hypotheses are investigated through a controlled between-subject experiment. The results show that cost of building plays a vital role in fixation and fixation is not likely inherent in physical representations. Results also show that physical models supplement designers’ mental models and lead them to higher quality ideas.

Prototyping may be simultaneously one of the most important and least formally explored areas of design. Over the last few decades, designers and researchers have developed many methodologies for ideation, product architecture, design selection, and many other aspects of the design process. However, there have been relatively few methodologies published regarding the efficient and effective development of prototypes for new products. This research explores a methodology for enhancing the prototyping process. It is founded on extensive literature review of the best practices of engineering prototype development. These findings have been aggregated and form the foundation of a methodology for formulating prototyping strategies. This methodology has then been experimentally evaluated in a controlled design environment, and its effect on the performance of prototypes has been demonstrated. The method consists of a set of guiding questions with corresponding flowcharts and foundational equations that assist the designer to make choices about how to approach the prototyping process in an efficient and effective manner.