Flow is a concept that lean teaches about how a product/service moves from beginning to end. When the product/service stops there is a disruption in the flow. This is when inventory starts to build between two steps in the process.
With the functional mentality, people only worry about optimizing each machine, without regard to the flow. The thought is, “I have to run this machine as fast as I can and get as much product out as possible.”
The hard part for people with this mentality to understand is the product/service will only move as fast as the slowest operation. No exceptions. Period.
Take a simple process like doing laundry at home. My dryer is always slower than my washer, so when I have multiple loads of laundry to do nothing moves faster than the time it takes to complete a dryer cycle.
I move a load of laundry from the washer to the dryer and start the dryer. Then I add another load to the washer and start the washer. The washer always finishes at least 15 minutes before the dryer. Instead of taking the laundry out of the washer and piling the wet clothes in a laundry basket, I let them sit in the washer. Knowing the dryer is the slow part of the process, it would do me know good to start another load of laundry in the washer because it still won’t end before all the other loads have finished in the dryer.
This is how we should look at the flow of our processes at work. It does no good to buy equipment or change the process to speed up a part of the process that is not the slowest step. In the end, the product/service is still being completed at the same rate.
What is the dryer in your process?