Product Design
5. The Design Process
In general, the formal process of design is remarkably similar across a range of products and design disciplines from architecture to product design to fashion. According to Pugh (1991: 6) Walsh et. al. (1992: 52) and Cross (1989: 21) the product design process generally involves the following steps:
- Examination of market needs
- Problem/need analysis and the Design Brief
- Product Design Specification
- Concept development and prototyping
- Embodiment design
- Detailed design
- Design for manufacture
- Design review and evaluation
- Post production design and improvement
Examination of market needs
Market-led design is the process of transforming customers needs into saleable products. The customers can be people, institutions or other companies. The needs of customers are often multiple and complex. Market-led design contrasts with technology-led design, in which the driving force behind product development is a new technology, and production-led, where design is based on the production equipment available.
The main aim of market-led design is to produce products which are suited to the needs of their users and to avoid the costly mistake of designing a product for which there is no demand. Establishing the needs of customers is the most difficult aspect of market led design, since customers do not always know what they want. Knowledge about markets comes from a wide variety of sources: legislation, patents, copyrights, reports, proceedings and trade journals, competitor products, statistical data, and through surveys and interviews with customers and users (Pugh, 1991: 29-43).
Problem/need analysis and the design brief
The problem/ need analysis stage of the design process is where the designer, or marketing department analyses and collects information about existing products and markets, and the need or problem which the product will be aimed at satisfying or solving.
The design brief is a formal document which describes succinctly what is to be designed and for which target markets. It emerges from an analysis of the need or problem. In a company, the brief is usually drawn up by the marketing department or management. The purpose of the brief is to make it clear to the designer, exactly what it is they are designing. The British Standards Association (1988) cited in Walsh et. al. (1992: 198) describe the importance of the design brief in the draft British Standard on Product Design BS7000:
The importance of the design brief cannot be over-emphasised. An inadequate design brief is a dangerous document: it may mean that management does not know what it wants, but it certainly means that the designer is misinformed about what is required....it is regrettable that many designers are obliged to work to briefs that are inadequate - or are even non existent.
In the production of successful designs, it is essential that the requirements of customers are fully researched. At this stage a plan is usually drawn up to establish the time-scale for the design process and the personnel and resources which will be utilised.
Product Design Specification (PDS)
The Product Design Specification (PDS) is a detailed document which sets out the marketing and technical parameters of a product. Marketing specifications describe the target market, price, image and performance requirements of the product. A consideration basic to all good design is the factor of cost. The technical specification is more detailed and describes such aspects of the product as: what the product must do, weight, size, power consumption, location and user environment, ease of use, standards applicable, cost requirements, materials, manufacture, reliability, maintenance, packaging and how the product will be transported: from the factory and in use. The document sets out the parameters within which the product is designed. The document does not limit the design solution, so for instance, the material specification might be; "non-toxic" or of a certain strength/weight ratio - thus ruling out some materials but not excluding others. The document is usually drawn up by several departments within a firm and includes the designer(s) (Pugh, 1990: 44-66).
Concept development
The concept development stage of product design is when the designer develops design concepts and solutions through drawings and mock-ups. The solutions should comply to the requirements of the Product Design Specification. The process of coming up with design concepts will vary between designers and product types. In general, a designer will come up with solutions from the following sources:
- Existing products - produced by the company or competitors
- Existing or new technologies - which are applied or combined in new ways
- From current ideas and trends within design - exhibitions, journals and interaction with other designers and engineers.
- From analysis of patents and trade literature
- Through creative problem solving and application of analytical theories
- Through suggestions from customers and product users as well as the designers own experience .
(Walsh et al, 1992: 207)
Embodiment and detailed design
This leads on to evaluation of the best solutions which are carried on to the embodiment stage. During the embodiment stage, one or more prototypes are produced.
The detailed design stage involves taking the best design solution and optimising every component and aspect of its design. At this stage, market testing is usually carried out in order to find out if there are any design faults or possibilities for improvement.
Design for manufacture, maintenance and reliability
Design for manufacture involves the consideration of how parts and components will be produced and assembled. It is essential that the designer works along with the production staff and is fully aware of the production limitations. The primary goal is to reduce costs but design for manufacture may also be targeted at improving quality or minimising environmental impact during the production process. Design for manufacture has particular significance in the context of developing countries. Many firms in LDCs do not have the resources with which to regularly update plant and equipment so it may be preferable to design around the limitations of existing equipment and utilise (relatively cheaper) labour rather than investing in expensive (possibly imported) plant.
Design for manufacture is closely related to design for reliability and reparability. Designing for reliability involves the determination of the mode failures of a product - how the product is likely to break down. Reliability and durability can be improved by simplifying complex systems (which are usually less reliable) or by changing the design or specification of parts which are likely to fail. Some parts are actually designed to fail or be expendable, but are easily replaceable. This is to avoid having to replace a more expensive component (For example the light bulbs need replacing rather than entire light fittings).
Designing for maintenance and repair requires that the designer take into account how the product will be serviced. The designer considers who will be repairing the product - whether the user or a repair-person, which components are likely to require cleaning or replacement and how access can be gained to these components. This aspect of design is particularly important in LDCs since there may not be a sufficient network of trained repair people—or conversely—maintenance and repair shops may be more concerned about the ability to use standardised parts. Issues of reliability and repair are closely linked to the broader issue of sustainable consumption and the associated political and social choices of appropriate legislation and regulation. This is explored in greater depth in section 8.2.
Design evaluation and review
Design evaluation is a function which is carried out at various stages of the design process. Its purpose is to check that the design solution is in accordance with the original design objectives. The PDS provides the criteria against which the design can be evaluated. Design evaluation is used to eliminate those solutions which do not satisfy the criteria and can also provide a means of deciding between different design solutions. One method of systematically evaluating design solutions is to establish a list of criteria, organised in order of importance. For example: different design solutions are evaluated against the criteria 'that a solution is less costly than an existing product' (Pugh,1991: 74; 77).
Design evaluation may be carried out after the initial concept stage and again after the detailed design stage and finally, before the design is launched on the market. Often design evaluation is carried out by a group of people (for example a team representing different departments in a firm). Group evaluation provides a more subjective means for looking at solutions and may generate new ideas. During the design process it is important that pertinent design decisions, drawings, ideas, results of testing and evaluation are recorded. This is to aid future product development.
The design review is a more general evaluation of the design process - to evaluate whether the design process has been successful and has kept within budget and time-scale. This information is valuable in estimating resources required for future product development.
Post production design and improvement
Post production design and improvement is carried out through feed-back from sales staff, resellers, and the users of a product. The purpose is to correct faults and instigate improvements which were overlooked in the design of the product.