Cycle Time

Cycle time is the most measurable thing in lean and also the most misunderstood. Most shops think they know their cycle times. They have ERP numbers that say a part takes nine minutes to mill. When somebody actually times the work with a stopwatch, the real cycle is usually fifteen minutes once setup, reaching, repositioning, and small inspections get counted. That gap, between the cycle time on paper and the cycle time on the floor, is where most flow problems hide.

"Cycle is what a stopwatch knows. Anything else is a guess dressed in software."

How cycle time works

Cycle time is measured at one process, on one operator, for one full unit of work. The clock starts when the operator picks up or begins on a part. It stops when they hand off the finished piece and reach for the next one. That total includes everything the operator actually does: the value-added work (cutting, bending, fastening, assembling), the necessary work (reaching, repositioning, quick visual checks), and any micro-waste that sits inside the operation (looking for a tool, fixing a small mis-feed).

Five to ten observations is usually enough to spot a stable average. The numbers will vary. The variation itself is data: a station with a tight spread is consistent; a station with a wide spread has hidden problems. Lean shops record both the average and the spread. Both feed into how the cell gets balanced.

Cycle time then becomes the input to everything else. Capacity per shift is available time divided by cycle time. The bottleneck of a value stream is the operation with the longest cycle. Whether the line can keep up with demand is a comparison between cycle time and takt time. Whether a pull system will work is partly a question of whether cycle times across stations are close enough to each other to flow without buffering between them. None of that math works if cycle time is a guess.

Where cycle time fits on the shop floor

Picture a small contract manufacturer running plastic injection mold parts for three customers. The shop has six presses. The owner thinks press four is the bottleneck because it runs the longest jobs. A morning of cycle-time measurement says otherwise. Press four runs a 90-second cycle on its biggest job, which sounds long but matches the takt the shop needs. Press two, the smallest press, runs at 45 seconds but has so many tool changes that effective cycle is closer to 80 seconds. Press six, the newest press, is running a 60-second cycle on a 30-second job because the operator was trained to baby the machine.

That single morning of stopwatch work tells the owner where the actual bottleneck is (press two, because of changeover, not press four) and where the spare capacity is hiding (press six, because of operator habit). No software discovered any of that. A stopwatch did. The owner moves one operator and one job, and the shop's effective output goes up by twelve percent the next week.

Common mistakes with cycle time

• Trusting the ERP number. ERP cycle times are usually whatever was entered at quote time. Real cycle time is whatever the stopwatch says today.
• Timing only the value-added portion. Reach, reposition, quick inspection, and tool grab are all cycle. Excluding them hides the gap between paper and reality.
• Averaging without spread. A cycle that varies from four to ten minutes is a different problem than a cycle that varies from six to seven. Track both.
• Optimizing the wrong station. A faster cycle at a non-bottleneck just produces parts the next station cannot absorb, growing work in process.
• Confusing cycle with takt. Cycle is what your process does. Takt is what demand wants. Treating them as one number means you cannot see capacity problems.

Cycle time and related Lean tools

Cycle time is the building block under most flow metrics. Takt time is the customer-driven pace cycle has to live underneath. Lead time is the customer-facing total, of which cycle time is a small fraction. Throughput time is the elapsed time across all cycles in a stream. Process cycle efficiency, the ratio of value-added time to total lead time, is the metric that exposes how much of the lead time is actually cycle work and how much is just waiting.