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Core Lean Concepts and Predictability
Many of the core Lean concepts have predictability as their ultimate goal. Take 5S, for example. The concept of “a place for everything and everything in its place” is rooted in making operations predictable. When an operator doesn’t have to chase down parts or tools, the time a process takes becomes more stable and consistent. That consistency of cycle time, in turn, lets processes operate without a buffer of parts between them to compensate for the lack of predictable deliveries.
Likewise, kanban cards make the resupply process more predictable. Jidoka makes machine output more predictable. When a machine stops, operators learn about it more quickly, and there are no surprises in the form of piles of bad parts.
Heijunka, or level loading, keeps teams from seeing unpredictable spikes in demand.
Predictability is grossly underrated in its importance to team members. While people often like variety in their jobs, that does not translate to chaos. When people have an expectation about what will happen, they like when it happens. If something unusual occurs, whether an unexpected surge in demand, or a machine breaking down, the additional work it frequently causes makes life difficult.
Problem Solving and Predictability
Predictability is also a key concept for root cause analysis. If you get the root cause right, you should be able to predict the outcome if you make a change to the input. If you can’t predict the change, you are incorrect in your analysis.
Don’t confuse variation with unpredictability. Variation is normal random spread. You can actually predict how many events happen at each point of the curve if you know its characteristics. Unpredictability corresponds to the outliers that don’t fit the historical variation.
Changes in systems often cause unpredictability in output. Whenever you make a change, monitor the output to see its effect.
Don’t underestimate the harmful effects of unpredictability on morale. People like variety in their jobs, but they don’t tend to like surprises, especially ones that cause more work.