A design-specific approach to design-for-assembly (DFA) for complex mechanical assemblies

DFA issues of complex assemblies are addressed. Complex assemblies have very high parts-counts, offer limited redesign options, and their assembly is an assembly of subassemblies. Conventional DFA is inadequate for complex assemblies as it omits the combinatorial aspects of assembly such as assembly sequence choice and partitioning of subassemblies. Here, assembly sequence analysis (ASA) is used as a basis for complex-assembly DFA. Searches for favorable subassembly partitioning and assembly sequences minimize assembly difficulty as measured by kinematic degrees of freedom secured in assembly moves, while logical constraints that part geometry imposes on sequence choice are satisfied. Findings are: ASA can expose assembly issues and pinpoint DFA redesign candidates; limitations on redesign favor designing function-defining parts first; logically-characterized issues dominate the quantitatively-characterized issues when choosing sequences or partitioning; once the former issues are addressed, a quantitative sequence choice criterion often duplicates historic assembly sequence choices; and a quantitative sequence choice criterion favors sequential over branched assembly lines.