More on Flow
Mark Rosenthal, who has become one of my key teachers in Lean, recently posted a wonderfully helpful view of flow on the NWLEAN listserve.
Here, he quotes Mr. Chihiro Nakao, one of the closest students of Taiichi Ohno, on the types of flow that should be evident in any operation:
Incoming materials - do people and processes have what they need, when they need it, where they need it, in fit-for-use condition? If they don't, you will see disruption to the using process.
Work-in-process - is there a smooth flow of material THROUGH the process? Does inventory accumulate? Are defects disrupting the flow? Is the amount of work-in-process steady, or does it fluctuate up and down for some reason?
Outgoing materials or finished goods. Is there a steady, level, even pull from the customer process? Are the right things available to the customer at the right times? Are they pulling in large batches (driving the production process to build large batches) - or are they pulling level (so the batch size is driven by problems the producing process can solve).
Information - do people know what they need to, when they need to? Is there too much information? Is information delivered on a pull, JIT? Do people have a way to signal and get an immediate response to problems?
Equipment - does the hardware itself support, or disrupt flow? Or is the process accommodating the machinery? Can the equipment support one-by-one production, of any designated product, in any sequence? Is there continuous positive evidence that it is operating normally? That quality- and operation-critical inputs such as air pressure are within normal limits? That feeds and speeds are normal?
Engineering - I may be wrong, but I usually explain this as the flow of improvements. Do they come continuously, in the form of problem solving of real problems, as they are encountered? Or are improvements done in big batches crammed into a week? Is there clear evidence of continuous problem solving? Nakao-san explains the "flow of engineering" as the "footprints of the engineer on the shop floor." It is, with a little reflection, a pretty good way to put it. Bottom line: Does anyone care, or is the shop left to fend for themselves once the outline of a process is put into place?
Mark, thanks for this wonderful description of flow and how to see it. Thanks for sharing your learning with us all.
I hope this is helpful.