Page 272 - The Handbook for Quality Management a Complete Guide to Operational Excellence

258 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 259

The market demand for Q is 50 units per week and Q sells for
$100 per unit. Assume that A, B, C, and D are workers who have
different non-interchangeable skills and that each worker is available
for only 2,400 minutes per week (8 hours per day, 5 days per week).
For simplicity, assume that there is no variation, waste, etc. in the
process. Assume this process has a constraint, Worker B. This fact
has profound implications for selecting Six Sigma projects.
2. Decide how to exploit the system’s constraint(s). Look for projects
that minimize waste of the constraint. For example, if the con-
straint is (feeding) the market demand (i.e., a capacity constraint),
then we look for projects that provide 100 percent on-time delivery.
Let’s not waste anything! If the constraint is a machine, or process
step, as in this example, focus on reducing set-up time, eliminating
errors or scrap, and keeping the process step running as much as
possible.
3. Subordinate everything else to the above decision. Choose projects
to maximize throughput of the constraint. After completing step 2,
choose projects to eliminate waste from downstream processes;
once the constraint has been utilized to create something we don’t
want to lose it due to some downstream blunder. Then choose proj-
ects to ensure that the constraint is always supplied with adequate
non-defective resources from upstream processes. We pursue
upstream processes last because by definition they have slack
resources, so small amounts of waste upstream that are detected
before reaching the con straint are less damaging to throughput.
4. Elevate the system’s constraint(s). Elevate means “Lift the restric-
tion.” This is step #4, not step #2! Often the projects pursued in
steps 2 and 3 will eliminate the constraint. If the constraint contin-
ues to exist after performing steps 2 and 3, look for projects that
provide additional resources to the constraint. These might
involve, for example, purchasing additional equipment or hiring
additional workers with a particular skill.
5. If, in the previous steps, a constraint has been broken, go back to
step 1. There is a tendency for thinking to become conditioned to
the existence of the constraint. A kind of mental inertia sets in. If
the constraint has been lifted, then you must rethink the entire
process from scratch. Returning to step 1 takes you back to the
beginning of the cycle.

Comparison of TOC with Traditional Approaches
It can be shown that the throughput-based approach is superior to the
traditional approaches to project selection. For example, consider the data
in Table 12.3. If you were to apply Pareto analysis to scrap rates you would

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