We all think we know what common sense is, but when we are trying to understand Kaizen and Lean Manufacturing the common way of thinking is exactly what gets in our way. An assembly line that is in laid out in a straight line with lots of material around it "just-in-case" is not conducive to eliminating waste and becoming lean. If we have problems with material, instead of compensating for it by having extra material lying around, we need to deal with the problem. If the material is purchased from a supplier, we need to work with the supplier to insure material that is always reliable.
A straight line assembly line has a number of problems. If there is any kind of carrier on which the assembly must travel, when it reaches the end of the line it must be transported back to the head of the line. If the line has a U-shape, when the carrier reaches the end of the line it is at the head of the line.
Value-adding workers working on the inside of a U-shaped line can easily re-distribute the work their share of the work to balance it, not only by taking or passing work to up and down-stream work stations, but the have the option to turn and do work on the other side of the U, directly behind them.
U-shaped lines are not "common sense" in many operations. The option to form lines this way must be learned.
Common sense often means adding operations that do not add value, creating more waste instead of eliminating waste. In a plant that made circuit breakers, data had to be printed on every unit, including the date code for the date the work was completed. I came across a line that was idle, and I asked why the line was stopped. "We're glad you're here, Bob. Maybe you can get management's attention. We need an additional machine to engrave the plates from which we print the labels on each breaker."
I asked why they did not have a plate on this line. The told me that they did have one, but the date code was yesterday's. The breaker must have the date code of the day it was made.
Why does it not have today's date code? I asked.
It has yesterday's code because the line was scheduled to run yesterday but did not.
Why did it not run yesterday?
It did initially, but we ran into a quality problem where we had to reject a third of a sub-assembly that came from a supplier.
If the sub-assemblies had been to specification, the breaker would have run yesterday. The printing plate would have the correct date code. We would not be waiting around for the correct plate, and we would not need additional plate-making capacity. Thus, another expensive plate-making machine was not needed. What was needed was to work with the supplier to make their sub-assemblies reliable. Buying another plate-making machine compensates for waste we already have by adding waste in the form of capacity that we do not really need.
Common sense of the floor of that factory was that to keep everyone working and the lines working the plate-making capacity had to be expanded.
Applying Lean Manufacturing involves changing the way we think about things. We could say that it involves changing our common sense. We want to always avoid non-value-adding work as much as possible.
Some people think that avoiding non-value-adding work means reducing "indirect" labor. One example of indirect labor is material handling. One kind of common sense says, get rid of material handlers and have production people handle their own material. This tends to increase the amount of waste, not decrease it, because it is very inefficient for people who are adding value all stop and go get material, or move it down-stream. It can be made efficient for one person to support several people who are adding value.
In Treating People As If They Were Robots (March 15, 2010 in this blog) I cite the example of highly skilled assemblers who improved their collective and individual productivity by adding a person to do all the non-value-adding prep work to assembling hydraulic cylinders.
Being successful at pursuing world class and becoming lean involves more than applying a series of techniques. The entire organization needs to think about things differently. The organizations leaders must lead this effort. A leader at a local level can accomplish some changes in thinking, but to change the organization requires leading the thinking of the entire organization in new directions.