Product development and improvement.

Understanding the intended purpose of a product and the study of existing designs is central to the design of successful products through the development of an appropriate set of key requirements that the design will be judged against, known as the product design specification (PDS).

• Products can sometimes appear to be ‘good designs’ as they are aesthetically pleasing. Their function, however, may not be as good.
• We need, therefore, to use a product design specification (PDS) to avoid superficial judgements based on appearance only.
• The 1963 Robin Day PP chair can be regarded as a ‘good design’, since it successfully achieved its main PDS criteria including:
○ easy to mass produce (injection moulding, tube bending and welding)
○ economical to purchase
○ stackable
○ tough and hardwearing (use of low carbon steel and PP with textured surface to improve serviceability and disguise shrinkage marks)
○ attractive (contoured shape and use of various colours)
○ sufficiently comfortable for institutional use.
• As well as the PDS, the guidelines of designers – such as Dieter Rams’ ‘ten principles of good design’ – may be appropriate (see Part 2, Chapter 3).
• Product analysis of existing designs is another important way of improving a PDS.

An acronym sometimes used to remember specification criteria is ACCESS FM:

• Aesthetics
• Cost
• Customer
• Environment
• Safety
• Size
• Function
• Materials

Designer Stuart Pugh developed a more comprehensive range of PDS criteria known as ‘Pugh’s plates’, shown in a simplified form in Figure 22.1.

• Implementation of the PDS is central to ensuring high quality and fitness for purpose.
• Objective, quantitative (measurable) tests provide a consistent judgement of effectiveness.

Figure 22.1 Simplified form of ‘Pugh’s plates’ PDS criteria

Life span:
Time before replacement

Safety:
Including applicable standards and legislation

Testing:
Methods of measuring success

Aesthetics:
Including shape and form requirements

Performance:
Expectations for function

Manufacturing:
Materials and labour

• Suitability for accurate, repeatable production is a key feature of successful design concepts.
• This can be facilitated by the use of simple geometric forms to reduce complex machining.
• Accurate, fully dimensioned drawings ensure the effective combination of components.
• Dimensional accuracy of design development must match production facilities available.
• Project CAD files have greater accuracy than manufacturing processes can usually achieve.

• Design constantly evolves due to our ability to implement new technology and materials.
• Current designs are therefore temporary and seen as flawed when new possibilities become practicable.
• Designers try to improve on what came before and learn from mistakes.
• Critical assessment of current products benefits from consumer experience to inform the development of further products.

These are important factors relating to the critical analysis of products:

• Direct interaction with the product is essential to assess its effectiveness.
• Carry out a detailed task analysis, directly assessing the product’s capability at each stage.
• Break down the tasks into individual stages for a more thorough analysis of the product.
• Ergonomics needs to be analysed by carefully considering user interaction with the product.
• Aesthetic analysis must be objective, factual and avoid generalisations like ‘it looks good’.
• The use of geometric or natural forms and the influence of designers and design movements should be acknowledged.
• Consider materials, the suitability of their properties and reasons for compromises.
• Study the link between materials, methods of manufacture and the scale of production.
• Assess the suitability of methods used to make and assemble all the product components.
• Consider the product’s environmental impact at all stages of its existence.

• User-centred design (UCD) means design focused around the end user.
• End user involvement at the development stage makes the success of products more likely.
• Tests with potential users in real-world situations facilitate objective product evaluations.

• Task analysis is useful when analysing a product.
• Potential users need to be monitored while they perform specific tasks with a product to identify issues with existing products or prototypes in development.

Figure 22.3 Direct interaction to assess the effectiveness of an ergonomic mouse

• Initial 2D or 3D sketch modelling facilitates early client feedback, mainly on aesthetics.

• These facilitate testing of aspects such as mechanisms and the intended form of a product.
• Compliant materials such as styrofoam and clay allow simple, hand tool shaping of 3D forms.
• Mechanical elements require more resistant material to test reactions to forces.

• These demonstrate the aesthetic form of the design concept.
• They are usually made from different materials to the final product due to the expense of producing moulds and formers suitable for the actual materials.

• These are particularly intended for testing mechanisms and technical principles.
• Appearance is not a high priority as various materials, components and temporary fixings are required to carry out the necessary adjustments to achieve optimum performance.

• Block models can be 3D ‘printed’ from CAD model files thanks to this technological development.
• Thermosetting polymers and resins are examples of the materials that can be used.
• CAD models and subsequent rapid prototypes facilitate the short timescale testing of a series of design iterations that can also be used to obtain focus group feedback.

• Time constraints and access to potentially expensive software and rapid prototyping facilities can govern the choice of modelling methods to be used.
• Virtual modelling, such as FEA and CFD (covered in Chapter 21), facilitates tooling simulations and prediction of production problems, to make savings in the longer term.