Something Lacking in the TPS House

People point out from time to time that there is something lacking in the TPS house used to explain the Toyota Production System. Typically it is represented with the two pillars of just in time and jidoka, with a foundation of kaizen, standardized work and heijnka. Although the wording differs from version to version, developing people and their creativity is in the center of the house.
“What about _ ?” People ask, with the _ being “fill in your favorite Lean tool or principle here.”
An article in Reliable Plant magazine points out the importance of Total Productive Maintenance for a Lean manufacturing system, and positions it at the foundation of the house. It’s a good article, making relevant points and offering different approaches taken by Toyota and Denso towards equipment stability.
But asking “Where does my favorite Lean, Six Sigma, TOC or other tool fit into the TPS house?” may be the wrong question. The goal should not be to fill the TPS house with as many tools and systems as possible (we are guilty of this also) but rather to extend the metaphor of the house to better understand the overall philosophy and management system at Toyota. Trying to fit more improvement tools or more of the non-production system prerequisites (sense of urgency, leadership, accountability, supplier partnerships, etc.) into the house itself just confuses people.
Perhaps a better way would be to zoom out from the house and look around, above and beneath it. Before we focus too much on the TPS house, we should seek a broader understanding by asking:
What about the foundation beneath the house (philosophy of management)?
What about the trees and yard around it (the environment)?
What about the neighborhood (community)?
What about the street and driveway to the house (marketing and sales channels)?
What about the utilities coming to the house (supplier)?
What kind of people live in that house (employees)?
Where is the garage, and the tool shed (by whom and how is the system maintained)?
What about the weather (socio-political environment around the business)?
When was the house built, for what reason, and by whom?” (history).
The answers to these questions may not provide practical everyday improvement tools, or solutions to problems. However these things all have had an impact on how the Toyota system came together in practice over the past half century, and they will have an impact on how you implement the Toyota Production System.

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