Output vs. Takt Time

The team’s challenge is to reach steady output of 180 units per hour.

Their starting condition was about 150 per hour. Their equipment and process is theoretically capable of making the 180 per hour with no problem.

They calculated their takt time (20 seconds) and established a planned cycle time of 17 seconds.

Some time later, they are stuck. Their output has improved to the high 160s, but those last 10-12 units per hour are proving elusive.

This is the point when I saw their coaching cycle.

Looking at their history, they had set a series of target conditions based on output per hour. Their experiments and countermeasures had been focused on reducing stoppages, usually on the order of several minutes.

“Does anybody have a calculator?”

“Divide 3600 seconds by 180, what do you get?”

“20 seconds.”

“Do you agree that if your line could reliably produce one module every 20 seconds that you would have no trouble reaching 180 modules per hour?”

Yes, they agreed.

“So what is stopping you from doing that?”

They showed me the average cycle times for each piece step in the process, and most were at or under 15 seconds. But averages only tell a small part of the story. They don’t show the cumulative effect of short stoppages and delays that can cascade through the entire line.

The team had done a lot of very good work eliminating the longer delays. But now their target condition had to shift to stability around their planned cycle time.

Performance vs Process Metrics

This little exercise shows the difference between a process metric and the performance metric.

Units-per-hour is a performance metric. It is measured after the fact, and tells the cumulative effect of everything going on in the process. In this case, they were able to make a lot of progress just looking at major stoppages..

Stability around the planned cycle time or takt time (you may use different words, that’s OK) is a process metric.

It shows you what is happening right now. THIS unit was just held up for 7 seconds. The next three were OK, then a 10 second delay. It’s those small issues that add up to missing the targeted output.

The team’s next target condition is now to stabilize around their planned cycle time.

Since they averaged their measurements, their next step is to (1) take the base data they used to calculate the averages and pull the individual points back out into a run chart and (2) to get out their stopwatches and go down and actually observe and time what is really going on.

I expect that information to help them clarify their target condition, pick off a source of intermittent delay, and start closing the remaining gap.

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