Page 60 - The Toyota Way Fieldbook

38 THE TOYOTA WAY FIELDBOOK

trucks being unloaded and then walk to the first process that adds value. The
tour guide gives a detailed explanation of that manufacturing process, mar-
veling at any new technology like machine vision inspection or laser welding.
We walk past piles of inventory, hardly noticing, then take a detailed look at the
next value-added process.
Often, a lean expert will ask to conduct the tour in reverse, starting with the
shipping dock. This is not just a gimmick or a clever trick. Beginning at the end
of the flow allows the lean expert to understand material flow from the cus-
tomer’s perspective. They do not want to know where material is going next,
they want to know where it comes from. Is it being pulled from this process or
is an earlier process pushing it whether it is needed or not? This will be the basis
for the development of the “future state.”
Lean experts will ask questions about the rate of customer demand [takt in the
Toyota Production System (TPS)] and how many days of finished goods inventory
is being held. They go to the final operation that adds value, often an assembly
operation, and ask how the operator knows what to make, in what quantity, and
when to make it. They quickly lose interest in the tour guide’s detailed discussion
of the nifty automated process that is continuously monitored by computer.
The lean experts are looking at the operation from a value stream perspective.
Individual processes need to be stabilized, but the reason for that is to support
the flow needed to give the customers what they want, in the amount they want,
when they want it. Toyota’s Operation Management Consulting Division (OMCD)
was created by Taiichi Ohno to lead major TPS projects and teach TPS by doing.
He wanted a tool to visually represent the flow of material and information and
pull people back from dwelling on individual processes. Ultimately, that led to
what we now call “value stream mapping,” and what Toyota calls the “Material
and Information Flow Diagram.”
Originally, this methodology was passed on within Toyota through the
learning by doing process—mentors trained mentees by assigning them to
work on projects. There was no documentation on how to develop the Material
and Information Flow Diagram, and in fact the name didn’t come until long
after the method was being used. Mike Rother and John Shook changed that by
writing Learning to See (Lean Enterprise Institute, version 1.3, 2004), in which
they teach the methodology by walking the reader through a case study on Acme
Stamping. You learn how to develop a current state map on one piece of paper
that shows your material flow and the information flow that triggers the material
flow, and you can see the waste in your value stream. You calculate the value-
added ratio—the ratio of value-added time to total lead time—then learn how
to develop a future state map: material and information flow based on flow and
pull and building to the customer rate of demand, or the takt time. From there
you develop a detailed action plan and do it.