An order waits in a pile after a busy morning. A manager asks the team to move faster. Before changing the schedule, it helps to see which step sets the pace. A station that works quickly can still create a bigger pile if the next one processes orders more slowly.
Count finished work at each step
Imagine a small bakery with one worker shaping rolls, one oven and one packing station. In an hour the team can shape 60 rolls, bake 40 and pack 50. If every order passes through all three steps, demand is steady and rolls are ready to move, the oven limits the simplified line to 40 finished rolls an hour. At that pace, the shaper can prepare more rolls than the oven can take.
The Lean Enterprise Institute uses cycle time for how long a process takes and distinguishes that from wider lead time. In the bakery, track how long a batch occupies the oven and how long a particular order waits before it gets there. The waiting time belongs in the customer’s experience even while the oven itself runs at a steady pace.
Test what would happen if one step got faster
Suppose the shaper gets new tools and can prepare 75 rolls an hour. With the same oven and packer, the line still produces at most 40 finished rolls an hour under the model. Extra shaped rolls may simply wait in front of the oven. If the team instead raises baking capacity to 48 rolls an hour, and the shaper and packer can keep up, the model gives 48 finished rolls per hour.
Raise the oven to 55 and packing now caps output at 50. That is why a useful improvement target can move. Check the output of the whole process after changing the slowest step. An increase in the busiest station’s output can be a clue, while completed orders tell you whether customers are getting more.
Check the measurement against a real day
Observe several periods. A queue can come from orders arriving in a burst, a scheduled break, a changeover or a defect that needs rework. Record those reasons alongside the count. Measure comparable batches and include unusable units separately so extra rejects cannot look like higher output.
A practical first pass is to draw each handoff on a sheet of paper. Write down the units each step completes and where they wait. Choose a small change at the suspected constraint, then check finished orders and waiting time again. If demand is lower than the line can handle, a faster station may create spare time instead of more orders.
Sources & further reading
- Lean Enterprise Institute guide to cycle time
Defines cycle time and related measures of process and lead time.
- Lean Enterprise Institute discussion of the theory of constraints
Explains why improving a constraint affects the throughput of a whole system.