Two Major Classes of Mechanical Assembly 1. Methods that allow for disassembly Example: threaded fasteners 2. Methods that create a permanent joint Example: rivets Ease of assembly -can be accomplished with relative ease by unskilled workers using a minimum of special tooling and in a relatively short time Ease of disassembly -at least for the methods that permit disassembly Some disassembly is required for most products so maintenance and repair can be performed one of the method is Methods for manual operations: All time systems are based on the premise that variations in the time taken to carry out the same operation are small for different workers with proper experience. in assembly, situational method method fragments are used