Detail design is where the components and sub-assemblies are designed. Many companies use CAD to create models and working detail and assembly drawings. Drawings are produced in accordance with detailed calculations and preliminary design work. This stage corresponds to the development in the Research and Development function.
Decisions affecting the details of the manufacturing process to be used will also be made here, e.g. to what dimensions will the product be build, what tolerances can be allowed on the size of the components? In industry around three-quarters of the total design activity is occupied by detail design; unless the product design specification and concept design stages have been properly implemented, this time may easily be wasted.
At the end of the detailed design phase, a complete documentation package for the product, process or procedure will have been made, comprising engineering drawings, manuals, assembly information, production test plans, and materials specifications as well as marketing plans, distribution plans, documents detailing sources of supply, sales plans and financial plans.