A design brief is the statement a client gives to a designer outlining what they want their product to be like, eg 'Design a drinks bottle holder for use while riding a bicycle'. The designer could also produce a brief on behalf of the client, as the client might have a problem but not know how to proceed.
A design specification is a list of criteria a product needs to address. Using the brief as a starting point for research, a specification can be written when more facts are known. Information needs to be found through research to help produce early design solutions and improvements.
If the criteria are measurable, it makes it easier to later measure how effective the design ideas are, eg 'How much will the design cost to produce?'
Design specifications should include:
A manufacturing specification is created after the design is finalised and should contain enough information to enable a third party to manufacture the design. This begins with a detailed drawing with dimensions often produced using Computer Aided Design (CAD) software. A parts list should then be prepared, detailing the materials that will be used to manufacture each component of the design and how they will be finished.
Once these are in place, a flowchart can be produced describing the order of production, including quality assurance, quality control and tolerance. Machinery should also be referenced together with relevant safety considerations. Finally, before manufacture can begin, a Gantt chart can be prepared that will consider the timescale allowed for the construction of the prototype.