Assembly in the manufacturing process consists of putting together all the component parts and subassemblies of a give[n] product. Assembly includes fastening, performing inspections and functional tests, labeling, separating good assemblies from bad, and packaging and/or preparing them for final use.
Assembly is unique compared to the methods of manufacturing such as machining, grinding, and welding in that most of these processes involve only a few disciplines and possibly only one. Most of these nonassembly operations cannot be performed without the aid of equipment, thus the development of automated methods has been necessary rather than optional. Assembly, on the other hand, may involve…one machine, many of fastening methods such as riveting, welding, screwdriving and adhesive application. Automatic parts selection, probing, gaging, functional test, labeling and packaging are also involved .
 Graham, G.A. "Automation Encyclopedia." King, R.E., ed. Dearborn, Mich.: Society of Manufacturing Engineers, 1988.