#73 Decoding the DNA of the Toyota Production System
This post is a summary of a four year study (subscription required) conducted by Steven Spear and H. Kent Bowen to decode the Toyota Production System (TPS). Few manufacturers have managed to imitate Toyota's success even though Toyota has been extraordinarily open about its practices. Why?
The authors argue that other companies have copied the tools and practices that are visible in the plant visits - but not the system. Toyota views its operations as a continuous series of controlled experiments. Whenever Toyota defines a specification, it is establishing a hypothesis that is then tested through action. This approach the scientific method is ingrained in the workers.
Four principles or rules that govern the TPS:
Rule 1 - How to work?
All work shall be highly specified as to content, sequence, timing, and outcome.
Rule 2 - How employees must interact with each other?
Every customer supplier connection must be direct, and there must be an unambiguous yes-or-no way to send requests and receive responses.
Rule 3 - How production lines are constructed?
The pathway for every product and service must be simple and direct.
Rule 4 - How people learn to improve?
Any improvement must be made in accordance with the scientific method, under the guidance of a teacher, at the lowest possible level in the organization.
How to work?
Rigid specification ensures high quality and eliminates variability. Companies that don't specify work as rigidly have to deal with variability in output, lower quality, lower productivity and higher costs.
Toyota has a unique approach to teaching and learning. They allow their workers to discover the rules as a consequence of solving problems. A supervisor who wants to teach a worker the rules will come over to the work site and ask the worker the below questions:
How do you do this work?
How do you know you are doing this work correctly?
How do you know that the outcome is free of defects?
What do you do if you have a problem?
All the rules are taught in a similar Socratic fashion of iterative questioning and problem solving.
How employees interact?
This rule ensures that there is no ambiguity in deciding who provides what to whom and when. When a worker makes a request for parts, there is no confusion about the supplier, the number of units required, or the timing of delivery. Once again this reduces the possibility of variance. This holds true for service requests as well. Workers are encouraged to request for help - designated supervisor must respond and resolve the problem within the worker's cycle time.
Other companies encourage their employees to resolve problems on their own before asking for help. This approach, sometimes lead workers to hide problems and they remain unresolved. Problems mount up and gets solved only when they become big enough - by which time valuable information about the real cause of the problem may have been lost.
How production lines are constructed?
Toyota ensures that there are no forks or loops to convolute the flow in any of Toyota's supple chains. Goods and services do not flow to the next available person or machine but to a specific person or machine. Requiring that every pathway be specified will ensure that an experiment will occur each time the path is used. For example, if workers found themselves wanting to divert production - they would conclude that their actual demand or capacity didn't match their expectation.
How people learn to improve?
For people to consistently make effective changes, they must know how to change and who is responsible for making the changes.
Toyota trains and coaches employees on the scientific method -"If we make the following specific changes, we expect to achieve this specific outcome."
Frontline workers make the improvements to their own jobs, and their supervisors provide direction and assistance as teachers. If something is wrong with the way a worker connects with a particular supplier within the same assembly area, the two of them make improvements with the assistance of the common supervisor.
Aside: Toyota does not use the word solution, they are referred to as countermeasures - as solution would imply a permanent resolution to a problem. This is the reason Toyota does not consider tools or practices such as Kanban or andon cords as fundamental to TPS. As changes are being made at the lowest level in response to problems faced, different organizational structures coexist in the same plant.