Hidden Negative Consequences

“Stop the line if there is a problem” is a common mantra of lean manufacturing. But it is harder than first imagined to actually implement.

The management mindset that “production must continue, no matter what” is usually the first obstacle. But even when that is overcome, I have seen two independent cases where peer social pressure between the workers discouraged anyone from signaling a problem. The result was that only problems that could not be ignored would come to anyone’s attention – exactly the opposite of the intention.

Both of these operations had calculated takt time using every available minute in the day. (Shift Length – Breaks etc.) Further, they had a fairly primitive implementation of andon and escalation: The line stop time would usually be tacked onto the end of the shift as overtime. (The alternative, in these instances, is to fall behind on production, and it has to be made up sometime.)

So why were people reluctant to call for help? Peer pressure. Anyone engaging the system was forcing overtime for everyone else.

Countermeasure?

On an automobile line, the initial help call does not stop the line immediately. The Team Leader has a limited time to clear the problem and keep the line from stopping. If the problem is not cleared in time, the problem stops the line, not the person who called attention to it. This is subtle, but important. And it gives everyone an incentive to work fast to understand and clear the problem – especially if they know it takes longer to clear the problem if it escapes down-line and more parts get added on top.

There are a number of ways to organize your problem escalation process, but try to remember that the primary issue is human psychology, not technology.

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