Our natural instinct is to try to make things better. Everybody talks about looking for causes. HOWEVER, if we fail to differentiate between assignable and common causes, we can make things worse!
Professor Deming pointed out:
"A process may be stable, yet turn out faulty items and mistakes. To take action on the process in response to production of a faulty item or a mistake is to tamper with the process. The result of tampering is only to increase in the future the production of faulty items and mistakes, and to increase costs - exactly the opposite of what we wish to accomplish."
The Deming Funnel demonstrates how a lack of understanding of variation, makes things worse, despite best efforts. It is essential to be able to understand how to use and interpret Process Behavior Charts (control charts).
It is human nature to try to fix things when they are off target. Mr Bill Smith gave a classic example by tampering with his molding process. He made things worse. Variation INCREASED by "as much as +/-1.5 sigma" off target. Mr Smith demonstrates Mode 2 tampering. If Mr Smith had an understanding of variation, the Six Sigma fiasco might never have been born.
NOT THE SPECIFICATION
Focusing on defect counts and the specification can make things worse. Defects based approaches such as Conformance to Specifications, Six Sigma and Zero Defects are red flags to a lack of understanding of variation. Such methods fail to even attempt to teach an understanding of variation.
Naive statements such as "our engineers never stop until they find every cause" is a red flag to a lack of understanding of variation. Employees need to understand when to look for causes.
STABLE, PREDICTABLE PROCESSES
Good Quality mean's "On target with Minimum Variance". Our aim should be to ensure stable, predictable processes.
MODE 3 TAMPERING
The video shows our Interactive Augmented Reality Funnel Experiment in Mode 3 tampering. In mode 3 an adjustment is made in the opposite direction to that in which the ball rolls. The Funnel is adjusted from the center, target position, rather than from its previous position as in Mode 2.
Mode 3 tampering produces an oscillation of outcomes.
Escalating warfare and arms races are examples of Mode 3 tampering. Both sides react to each other and progressively increase armaments. The war may be a shouting match or a domestic argument, where each side tries to outdo the other. The same thing happens with price wars between stores. No one benefits from this form of tampering.
Mode 3 may be seen in financial circles with over adjustment of interest rates, or government financial controls. It has occurred recently in energy supply.
The outcome of Mode 3 tampering is an explosion, destruction, or in this experiment, the balls falling off the sides of the base sheet on opposite sides. Only external intervention can save the day.
by Dr Tony Burns BE (Hon 1) PhD (Chem Eng)