Kaizen is largely a drive toward stability – that is a more consistent operation, producing a more consistent result. The key is the definition of “consistent.”
Overproduction is a way to achieve the illusion of consistency in the face of inherently unstable operations. Your machines are unreliable? Run faster when you can run. Inconsistent quality? Make more stuff so you have enough good ones.
And you know what? If my machines are unreliable, I do run faster. I put in buffers of time and material. I have to, because at the end of the day, I need to satisfy the customer.
The difference is in what I am trying to do, and how I define “stable.”
If I were to define “stable” as “I don’t have to pay attention to this” then my natural reaction will be to bury the problem by building in accommodations – things I “have to do” because “the process isn’t stable.”
Once there are sufficient accommodations in place, I, as a manager, could shift my attention elsewhere.* We all know the downside of this – those problems accumulate, and eventually the system fails completely. But our brains are programmed to assign cause to recent events, even if they were simply the tipping point.
The reflex reaction, then, is to look at something that just happened, assume that was the problem (since everything was “fine” before), and find a short term fix to make it go away.
I see this quite a bit. That is why I am now quite… inquisitive about the ongoing process improvement efforts if I hear a target condition as some level of performance, and “the process is stable” as the current condition.
No problem is a big problem.
*I may very well put in a temporary countermeasure so I don’t have to deal with all of the obstacles and problems at once. It looks the same if you are touring the shop floor. The difference is intent.