Page 388 - Design for Six Sigma a Roadmap for Product Development
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358 Chapter Ten
The functional requirements are
FR 1 : open beverage bottle
FR 2 : open beverage can
The DPs are
DP 1 : beverage opener side
DP 2 : can opener side
The design mapping is depicted in
{ } [ ]{ }
0
FR 1
DP 1
FR 2 0
DP 2
By definition, the two functional requirements are independent or
uncoupled per axiom 1 (Chap. 8). A simple device that satisfies these
FRs can be made by stamping a sheetmetal as shown in Fig. 10.1. Note
that a single device can be made without a functional coupling and
hosted in the same part physically. Functional coupling, a design vul-
nerability, should not be confused with physical coupling. In addition,
since the complexity of the product is reduced, it is also in line with
axiom 2. The following steps are recommended:
■ Choose the appropriate materials for fabrication ease.
■ Apply the layered assembly principles and factors such as parts han-
dling and feeding, orientation, identification, positioning, allowable
tolerances, and mating.
■ Use the appropriate DFM and DMA tools. Since DFM and DFA are
interlinked, they can be used sequentially according to the roadmap in
Fig. 10.2 as suggested by Huang (1996), who called the roadmap the
“DFMA” approach.
10.2.1 The DFMA approach
With DFMA, significant improvement tends to arise from simplicity
thinking, specifically reducing the number of standalone parts. The
Boothroyd-Dewhurst DFA methodology gives the following three crite-
ria against which each part must be examined as it is added to the
assembly (Huang 1996):
1. During operation of the product, does the part move relative to all
other parts already assembled?
2. Must the part be a different material than, or be isolated from, all
other parts already assembled? Only fundamental reasons con-
cerned with material properties are acceptable.