Page 186 - Design for Six Sigma for Service (Six SIGMA Operational Methods)

158 Chapter Seven

Example 7.6 illustrates this step-by-step process.

Example 7.6: Cigarette Lighter FAST Diagram
Figure 7.11 shows a typical cigarette lighter. Before constructing the FAST
diagram, assume that we have compiled the function list illustrated in Table 7.10.
First, we pick up the basic function “produce flame” and ask the Why and
How questions as illustrated by Fig. 7.12. The basic function of a cigarette
lighter is to produce a flame. By answering the question, Why produce a
flame? we get the higher-order function “ignite cigarette.” By answering the
question, how do we produce a flame? we get the lower-order function “ignite
fuel.” We then can ask a further question, How do we ignite the fuel? By
answering this question, we find that we need two lower-order functions to be
performed, “produce spark” and “release fuel.” These two functions are of
equal importance; therefore, we add these two functions in the FAST diagram,
as illustrated in Fig. 7.13.

Now we could continue to ask Why and How questions to find lower-order
functions for the “release fuel” and “produce spark” functions, and continue
this process. We would end up with the diagram illustrated by Fig. 7.14. The
functions picked in the figure form the primary path of the FAST diagram of the
cigarette lighter.

There are still many functions in the function list that cannot be fitted into
the primary path. By asking the When question, we can fit the rest of the
functions into the FAST diagram. The final FAST diagram is illustrated by
Fig. 7.15.

7.2.6 Cost-Function Relationship
The completion of the FAST diagram makes it possible to complete the
cost-function work sheet. The cost-function work sheet lists all
functions versus all parts of a product or actions of a system, procedure,
or administrative activity. The objective is to convert product cost to
function cost.

Figure 7.11 A Cigarette Lighter