THIS COLUMN IS A DICHOTOMY. It's about management of change in critical cleaning work where change can be fatal, or the key to success.

The Father of it All
Vilfredo Pareto (July 15, 1848 - August 19, 1923) made several important contributions to economics, sociology, and moral philosophy, especially in the study ofincome distribution and in the analysis of individuals' choices.

The 80/20 rule is often named for him because of his observation that 80% of the property in Italy was owned by 20% of the population. Said another way, the 80/20 assumption is that most of the results in any situation are determined by a small number of causes.

"S" Isn't for Superior
Most of us who practice critical cleaning have been long aware of the 80/20rule, and wish it didn't apply to us. But, it seems to do so.

An example is Figure 1 which is a smoothed view of actual data about the effect of ultrasonic power level on cleaning effectiveness. This S-shaped curve isfamiliar because of at least three aspects:

• -With only a small amount of applied power, the rate of change (cleanliness improvement) is quite high; if only one could always operate in this circumstance.
• -At very high power levels, the rate of change (cleanliness improvement) asymptotically approaches zero. Doubling the applied power level won't double cleaning quality.
• -At an intermediate power level (750 to 1,000 watts in Figure 1), about 80% of the soil removal is accomplished.

Vilfredo Pareto’s Legacy
This illustrates the 80/20 rule (the Pareto Principle or Pareto's Law). AssumingMurphy's Law is held in check, this means, for example, roughly:

-20% of input errors cause 80% of the defects,
-20% of the business units will produce 80% of revenue,
-80% of decisions come from 20% of meeting time,
-80% of customercomplaints from 20% of products, and only 20% of the time and effort will get parts 80% clean.

It's About Time
It is human nature to compensate; to shorten cleaning cycle time when performancelags the production schedule or to lengthen it when quality lags standard.

If you substitute elapsed time (cycle time) for power level in Figure 1, the effect will be the same; i.e. doubling the cycle time for cleaning operations will have the same effect as doubling the applied ultrasonic power level—verylittle.

The Needs of Critical Cleaning
But, while there may be a nominal effect on cleanliness by implementing such actions, they may be sufficient to change the operation at the "Six Sigma" level. That's not a nominal change! Managing critical cleaning is about management of small changes. That's the level of change remainingafter the Pareto Principle has been applied.