Page 183 - Design for Six Sigma for Service (Six SIGMA Operational Methods)

Value Engineering 155

Independent
function

When
How
Why
Function Function
(higher order) Function (lower order)
When

Activity

Figure 7.5 Directions in FAST Diagram

All the functions and/or activities along the When direction with a particular
function will happen at the same time. We detect these functions or activities
by asking the question, When a function occurs, what else happens? The
independent functions and supporting functions are listed above the par-
ticular function; the activities will be listed under the particular function.

Common Symbols Along a Primary Path
In a primary path of a FAST diagram, it is possible that several functions have
to be performed simultaneously as the precondition for lower-order
function(s). Sometimes, these functions are related by logical AND, and
sometimes they are related by logical OR. Figs. 7.6 to 7.9 illustrate such cases.

In both Figs. 7.6 and 7.7, the fork is read as “and.” In Fig. 7.6, how do you
build the swim club? By constructing the pool and constructing the club
house. “Construct pool” and “construct club house” are equally important.
In Fig. 7.7, how do you determine compliance deviations? By analyzing the
design and reviewing proposals. However, “analyze design” is more
important than “review proposals.”

Construct
pool
Build Contract
swim club builder
Construct
club house
Figure 7.6 Two Equally Important Functions in AND Relation