I’ve put down my thoughts about how experimentation is one of the central tenants that separate TPS from it’s imitators. This Plan-Do-Check-Act structured approach requires well thought out specifications and a high degree of structure.
Conventionally this structured approach with a reliance on clear concise documentation would indicate a very ridged command/control approach with little flexibility given to the various organizations. At Toyota the opposite is true, organizations are challenged and left to get on with it with little management oversight while the project is unfolding.
To translate this to a production system is straightforward. There may be a number of good ways of doing something, experimentation will find the best. Once this best way is found, it will always be used unless something drives a change.
The operator putting wheel nuts on will put them on in a certain order, over a certain time, using specified tool.
The work is highly specified. The content, timing, sequence and expected outcome are clearly known to the operator, who happens to be responsible for his own quality. In this case the outcome is four wheels installed with twenty wheel nuts to a set torque value.
It sounds really simple, the difference is in the details. In a vast majority of production shops the sequencing of a job is not documented to this level of detail. Typically new operators are shown by experienced employees how they do a particular operation (like fitting the wheels). There is no clear, unambiguous specification to follow. No experimentation has been done to refine the best way and variability still exists, and where you have variability you allow room for errors to happen.
Toyota clearly does things differently. First a new employee is taught the right way to do the job they have been assigned by their immediate supervisor, not the person doing it last. No bad habits are handed down, only the correct sequence. The next part is possibly the biggest difference, each employee is required to be able to answer the following for each of the jobs they are required to do.
- How do you do this work? (Plan)
- How do you know you are doing this work correctly? (Do)
- How do you tell the output is free of defects? (Check)
- What happens if there is a defect? (Act)
This continual questioning of the process and how the operator is doing it brings us back in a full circle to the “Plan-Do-Check-Act” mantra that runs deep through the development cycle. We can see is also at the center of the production processes.
This is also where the moving line becomes so important, at any time anyone familiar with the system can look at the location of the car being put together and know exactly what state of build it should be in. It works just as well for 737 jet liners as it does for a Toyota Yaris.
If the car/jet has hit a certain location in the factory then the seats should be in the process of being installed. If the seats are still sitting on the side of the line waiting for another process to be completed then we have a problem and the line is stopped. The line is not restarted untill the issue is resolved. In the case of the 737 manufacturing, design and industrial engineers are collocated with in yards of the line and their sole job is to solve the issue and restart production.