Page 273 - The Handbook for Quality Management a Complete Guide to Operational Excellence

260 C o n t i n u o u s I m p r o v e m e n t e f f e c t i v e C h a n g e M a n a g e m e n t 261

Process A B C D
Scrap rate 8% 3% 5% 7%

(Pyzdek and Keller, 2010)

Table 12.3 Example Process Scrap Rates

begin with projects that reduced the scrap produced by Worker A. In fact,
assuming the optimum product mix, Worker A has about 25 percent slack
time, so the scrap loss can be made up without shutting down Worker B,
who is the constraint. The TOC would suggest that the scrap loss of
Worker B and the downstream processes C and D be addressed first, the
precise opposite of what Pareto analysis recommends.
Of course, before making a decision as to which projects to finance,
cost/benefit analyses are still necessary, and the probability of the project
succeeding must be estimated. But by using the TOC you will at least know
where to look first for opportunities.

Using Constraint Information to Focus Six Sigma Projects
Applying the TOC strategy described earlier tells us where in the process
to focus. Adding CTX information (see Table 12.4) can help tell us which

Project
Type Discussion
CTQ Any unit produced by the constraint is especially valuable
because if it is lost as scrap additional constraint time must be
used to replace it or rework it. Since constraint time determines
throughput (net profit of the entire system), the loss far exceeds
what appears on scrap and rework reports. CTQ projects at the
constraint are the highest priority.
CTS CTS projects can reduce the time it takes the constraint to
produce a unit, which means that the constraint can produce
more units. This directly impacts throughput. CTS projects at the
constraint are the highest priority.
CTC Since the constraint determines throughput, the unavailability of
the constraint causes lost throughput of the entire system. This
makes the cost of constraint downtime extremely high. The cost of
operating the constraint is usually minuscule by comparison. Also,
CTC projects can have an adverse impact on quality or schedule.
Thus, CTC projects at the constraint are low priority.

(Pyzdek and Keller, 2010)
Table 12.4 Throughput Priority of CTX Projects That Affect the Constraint

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