Hart-Smith, L., "Design for Assembly (DFA) - The Key to Making Parts-Count Reduction Profitable," SAE Technical Paper 1999-01-2281, 1999, doi:10.4271/1999-01-2281.
This paper explains, via specific examples, that no one-to-one correlation exists between design for assembly and parts-count reduction. It explains how overall cost reductions cannot be maximized if the cost of each and every step in a process is minimized separately, as it occurs. A distinction is drawn between goals and the metrics used to measure satisfaction of the goals, and concern is expressed at how frequently one now sees the metric usurping the function of the original goal - to the extent that satisfying the metric can result in directly violating what once was the goal. Illustrations are provided of how, and when, parts consolidation can be of overall benefit. Other examples reveal how parts-count reduction has been counterproductive. A better metric, interface control, is recommended as an alternative. The point is made that, when the superior choice of action is not self evident, the design-for-assembly (DFA) process will identify the best approaches, for both design and manufacturing, -provided that the DFA process is carried through to completion, and NOT merely to the limits of involvement for each individual department! The real goals are identified as minimization of total costs of manufacturing, acquisition, operation, and the like, better performance than competitive products, or of maximizing profits. Goals at this level, alone, can be universal, and not all can be satisfied simultaneously. The techniques of achieving these goals, of which parts-count reduction is only one, are never universal. They are sub-level goals and need to be recognized as such if they are not to do more harm than good.