Page 388 - Design for Six Sigma a Roadmap for Product Development
P. 388

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.
   383   384   385   386   387   388   389   390   391   392   393