Design Management Group

Prototyping

Prototyping has been described by Tom Kelley of IDEO design consultants as 'the shorthand of innovation'. Effective prototyping is arguably one of the most critical skills in product design.

Prototypes serve three main purposes:

Reducing market and commercial risks

• Testing the market response to novel features and concepts
• Comparing design alternatives with users and key stakeholders
• Gaining early feedback on the 'soft' aspects of the design mix, including usability and appearance

Reducing technical risks

• Early testing of novel technical solutions
• Evaluation of the critical performance characteristics of a new product
• Resolving manufacturing issues

Building team confidence and buy-in

• Supporting brainstorming and creative exercises
• Enables the studying and refining of difficult features
• Demonstrate the viability of new principles
• Communicating concepts and alternatives within the team

Types of prototype

Prototypes can take many forms, from very simple mock-ups or visualisations to demonstrate a principle, through to sophisticated pre-production products and detailed analytical simulations. Different types of prototypes can be utilised for different purposes, as outlined in the table below.

Prototype fidelity vs cost

The fidelity of a prototype can be defined as how accurately the prototype represents either functionality (or performance), appearance, producibility or usability. A model with high fidelity will closely mimic the characteristics of the final production item. There is clearly a trade off between fidelity and cost. Typically, the greater the fidelity, the higher the cost. For example, a simple card model of a casting may have low fidelity compared with a full FEA model but it is also significantly quicker and cheaper to produce. Examples of fidelity vs cost are illustrated in the table below.

Rapid Prototyping (RP)

Since the introduction of Stereo-lithography in the late 1980s, RP has come of age. Representative parts and tools can be produced almost instantly directly from CAD data. RP provides speed, accuracy, and the ability to produce components with complex geometry which would otherwise require expensive tooling. This has provided new opportunities for designers to test ideas and concepts increasingly quickly. There are three core techniques:

Stereolithography

The original and most popular RP process. The model is built up in layers in a bath of photo-curable epoxy resin, which is solidified by laser. Produces accurate, strong and translucent parts.

3D Plotting

Utilises a print head to either fuse a powder or deposit molten material (wax, ABS) in layers to build up a component, section by section. The process can be viewed as similar to ink jet printing with the ability to build in the vertical direction. Especially suitable for small intricate parts.

Laminated object modelling (or Adhesive RP)

Layers of either ceramic, paper or plastic sheet are bonded together, with each layer being cut to the required sectional profile with a laser. Completed models have a wood like feel and can be used as either tooling or concept models.

Further information

• Baxter M, (1999), Product design: practical methods for the systematic development of new products, Stanley Thornes, UK
• Kelley T, (2001), The art of innovation, Harper Collins Business, London
• Thackara J, (1997), Winners: how today's successful companies innovate by design, Gower Publishing, UK
• Ulrich & Eppinger, (2000), Product design and development, McGraw Hill, USA