Toyota’s tools and techniques become more understandable, and effective, when we view them in the context of striving to achieve a target condition by working step by step through obstacles. These tools and techniques are subordinate to the routine of Toyota’s improvement kata, not independent of that routine, and our failure to see this perhaps explains some of the limited success we have had in trying to copy them.
Simply introducing kanban cards or andon boards doesn’t mean you’ve implemented the Toyota Production System, for they remain nothing more then mere tools.
—Teruyuki Minoura, President and CEO 1998–2002, Toyota Motor Manufacturing North America
If your primary objective is to “make products,” then many of Toyota’s techniques—which by their nature limit your ability to work around problems—actually make little sense. To “make products” you want to be able to jump quickly to another machine if one breaks down (kanban makes this more difficult), to change to a different production schedule when there is a parts shortage (heijunka makes this more difficult), and so on.
Toyota uses many of its tools, such as takt time, 1x1 flow, heijunka (leveling), and kanban, as target conditions in order to better see problems and obstacles. There is possibly an even more deep-seated and subtle reason for our missing this intention and for our limited success, so far, in utilizing those tools.
Take the example of takt time, where we monitor process output per shift or day, and thereby fail to recognize how much a process’s individual output cycles fluctuate. Perhaps we tend not to think about the individual process cycles because we have learned to manage by outcomes (rather than improving in small steps every day), tend to work with implementation lists (rather than target conditions), and feel we do not have the time to observe such detail. However, with many processes it only takes 20 minutes or so with a stopwatch to see if the process is fluctuating in or out of control. Despite such ease of analysis, I find very few companies where this is done. Why?
As discussed in What Defines a Company That Thrives Long Term, there is a human tendency to desire and even artificially create a sense of certainty. It is conceivable that the point here is not that we do not see the problems in our processes, but rather that we do not want to see them because that would undermine the sense of certainty we have about how our factory is working. It would mean that some of our assumptions, some things we have worked for and are attached to, may not be true.
In hindsight it seems somewhat foolish to have thought that simply implementing a kanban system or leveling scheme, for example, would result in significant and continuous improvement. The production processes themselves are still performing with essentially the same attributes as before. (There may be small, onetime improvements due to better organizing or paying closer attention.) We can now see that it is not actually the leveling pattern or kanban routine by itself that generates the improvement, but the step by step pursuit of conditions required to make those techniques work as intended. It is the striving for target conditions via the routine of the improvement kata that characterizes what we have been calling “lean manufacturing.”
An interesting side note is that since Toyota is pursuing the one contiguous flow ideal, then any solution, tool, or practice that does not yet equal that ideal can be thought of as a temporary countermeasure. For example, I am sometimes asked for a formula to calculate how many kanban cards one needs in a pull system loop. Viewed in the light of moving toward the ideal state, having exactly the right number of kanban is not important at the start. You just need enough inventory, or kanban, to hold the system together while striving to continually improve processes and reduce the necessary number of kanban over time. To want to know the precisely correct number of kanban at the start suggests that we are thinking in static rather than continuous improvement terms.