Lean is supposed to be based on the Toyota Production System (TPS). Therefore, it should follow that success would be measured by what extent any lean effort approaches the success of the TPS. What makes Toyota so successful? Let’s see what Toyota folks and some who’ve studied Toyota up close have to say about what makes the TPS special.
Yasuhiro Monden authored the groundbreaking Toyota Production System: An Integrated Approach to Just-In-Time, 4th Edition . He said this about the TPS, "I think the most important feature of the TPS is the "Just-In-Time" (JIT) concept. This is the concept of a system to make a product that is needed at the right time, in the right quantity. Many books just emphasize kaizen but JIT is the central part of the TPS." (http://lean-manufacturing-japan.com/interviews/toyota-production-system-part1.html)The central part of the TPS. Think about that statement. If the JIT system is the central part of the TPS, shouldn't the goal of any lean implementation be a JIT system?
Taiichi Ohno, Father of the Toyota Production System, said this about JIT. "Just-In-Time is an ideal system in which the items needed arrive at the side of the production line at the time and in the quantity needed." (The Toyota Production System, Ohno, pg. 32)
Toyota’s JIT System began with the pull method. Again, Mr. Ohno…“to realize a system in which the later process picks up requires us to transform the production methods of both the earlier and the later process." (The Toyota Production System, Ohno, pg. 32) In other words, for the later process to pull from the earlier process means all processes must be pulled. The production method matters. In fact, Ohno addressed the use of the pull method w/ suppliers when the production method wasn’t yet changed to the pull method..." if used for picking up parts from outside without first changing the production method within the company, kanban immediately becomes a dangerous weapon." (The Toyota Production System, Ohno, pg. 32).
Lean is not about the Toyota Production System. It’s about tools. And not even necessarily the tools that work for Toyota. This tool emphasis never results in a JIT system. It seems that the pull method is no more important than any other tool when, in reality it's "the central part of the TPS".
Taiichi Ohno had been working on a JIT system for almost 20 years when he came to America...In 1956, I toured U.S. production plants at General Motors, Ford and other machinery companies. But my strongest impression was the extent of the supermarkets prevalence in America...we made a connection between supermarkets and the just-in-time system...From the supermarket we got the idea of viewing the earlier process in a production line as a kind of store." (The Toyota Production System, Ohno, pg. 64)
He took this idea back to Toyota and began working on a pull method as he'd witnessed at U.S. supermarkets that would be suitable for automobile manufacturing. This pull method then led to the development of tools to support it. "Our biggest problem with this system (pull) was how to avoid throwing the earlier process into confusion when a later process picked up large quantities at a time. Eventually, after trial and error, we came up with production leveling". (The Toyota Production System, Ohno, pg. 68). Except standard work, all Toyota tools were developed to support the pull method which was instrumental in their Just-In-Time system.
How important was the Just-In-Time system to Toyota? Here's a clue. In the Publisher's Forward of Ohno's The Toyota Production System, Norman Bodek says "...Mr. Ohno believed just-in-time was a manufacturing advantage for Toyota. And for many years, he would not allow anything to be recorded about it." (The Toyota Production System, Ohno, pg. xi). Bodek goes on "...I think he also feared Americans would discover this powerful tool and use it against the Japanese." It was so important and "powerful" that it was not to be revealed outside.
What keeps lean from being “True Lean” is the lack of interest, focus, or ability to achieve “the central part of TPS” “this powerful tool” and this “manufacturing advantage”… a Just-In-Time system. Here's what Mike Hoseus, co-author of the Shingo Award Winning Toyota Culture and former Toyota executive said about The Toyota Template..."His perspective and focus on 'Just-In-Time' material availability and 'Flow-Pull-and Leveling' are missing components in many failed lean attempts".
At The Toyota Template our standard for success is implementation of the pull method leading to a Just-In-Time system.