Concepts and classifications

„Prototype‟ is a wide ranging concept and has specific meanings in different domains, such as computing science, metrology and pathology, etc. In product development, there are two other similar concepts to „prototype‟: „model‟ and „mock-up‟. To avoid confusion, it is necessary to distinguish them in the beginning of this chapter.

In Longman dictionary [1997], „model‟ refers to „a small copy of a building, vehicle, machine etc. ‟, while „mock-up‟ is described as „a full-size model of something that is going to be made or built‟. The „prototype‟ is defined as „the first form of a new design of a car, machine, etc.‟. In addition, Ulrich and Eppinger [1995, p219] defined prototype as “an approximation of the product along one or more dimensions of interest”. From the above definitions, it is found that, a „model‟ is usually smaller than the original while „mock-up‟ is a full-scale representation. Compared to the other two concepts, the concept of „prototype‟ covers a wider range and has no limitations regarding its size: full-

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or limited-scale models. Bond [1996] also stated that the term prototype is all embracing. It varies from simple cardboard and drawing pin models to prototypes made with engineering precision and almost indistinguishable from the intended final product. Furthermore, Ulrich and Eppinger [2003] and Rooden [1999] even suggested that rough sketches should also be viewed as prototypes. Therefore, in this research, prototype is taken as an all-inclusive term. However, each of these three synonyms, prototypes, models and mock-ups, might be used depending on their context in this thesis.

In addition, although dictionaries define prototype as a noun only, the word could also be used as a verb [Ulrich and Eppinger 2003]. Based on the definitions of prototypes, prototyping refers to the activities and process of creating and developing prototypes [Ulrich and Eppinger 2003, Lidwell et al 2010, p194]. Therefore, prototype and prototyping are two concepts that always relate to each other and should not be split.

The purpose of building a prototype (i.e. prototyping) is usually to embody design hypotheses, test the function and feel of the new design and elicit market feedback prior to production of a product [Ulrich and Eppinger 1995, p232, Schrage 1996, Hartmann et al 2006]. For example, industrial designers use prototypes to develop the look and feel of the product (including aesthetics and semantic product statement, ergonomics studies, etc.), electrical engineers use prototypes to validate the variety of states that systems can achieve and change, and mechanical engineers use prototypes to develop the physical behaviour of a product [Otto and Wood 2001, p 845].

During the design and development of a new product, different classes of prototypes will be built sequentially to meet different testing tasks. As Schrage [1996] stated, not all prototypes are the same, either in how they are built, or

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in the role they play in the design process. Several examples of prototype classifications are presented as follows:

First example

Classes Description

Proof-of-concept models which are used to answer specific

questions of feasibility about a product

Industrial design prototypes which demonstrate the look and feel

of the product

Design of experiments (DOE)

experimental prototypes

which are focused physical models where empirical data is sought to parameterize, lay out, or shape aspects of the product

Alpha prototype which is constructed to answer

questions regarding overall layout of

the actual product, including

materials and geometry

Beta prototypes which are the first full-scale functional

prototypes of a product, constructed from the actual materials as the final product

Preproduction prototype which is the final class of physical

models to perform a final part production and assembly assessment using the actual production tooling

45 Second example

Classes description

Early “proof-of-concept” models which help the development team to

demonstrate feasibility

“Form-only” models which can be shown to customers to

evaluate ergonomics and style

Spreadsheet models and

experimental test models

which can be used to set design parameters for robust performance

Table 3: Prototype classifications created by Ulrich and Eppinger [2003]

Third example

Classes description

Crude model enables you to get a better feel for the

basic premise of your invention

Working prototype allows users to try out some or all of

the features of the invention

Final prototype a model that looks and functions

almost like a manufactured product

46 Forth example

Classes description

Concept prototype which is useful for exploring

preliminary design ideas quickly and inexpensively

Throwaway prototype which is useful for collecting

information about the functionality and performance of certain aspects of a system

Evolutionary prototype which is useful when many design

specifications are uncertain or

changing

Table 5: Prototype classifications created by Lidwell et al [2010]

Besides the above methods of classification, all prototypes can also be generally categorized into physical prototypes as opposed to virtual prototypes [Stoll 1999, p131]. A physical prototype refers to a model made from real materials and substances, while a virtual prototype basically means a model created in computer. The research presented in this thesis is conducted based on this classification and aims to explore the characteristics of physical prototypes and virtual prototypes and the relationship between them.