person. Some people may always finish in 10 seconds while
others struggle and sometimes take longer. Once a worker
has finished assembling a unit in 10 seconds, she should
have nothing to do but start in on the next unit. This is
where conveyors come in handy. They keep the flow moving
at one unit per pitch increment. But when a worker finishes
early, she must wait out the remainder of that pitch increment
until the conveyor brings the next unit. There is nothing she
can do for her neighboring workers during this time.
Although everyone claims to be working precisely at the
pitch time, faster workers have their work slowed down by
slower workers. This kind of “coordinated work” is actually
quite susceptible to “idle time waste.”
The conveyor’s disadvantage is that it tends to hide idle
time waste and its advantage is that it keeps things moving at
the pitch time. This means that no matter how much improved
an individual’s efficiency becomes, that improvement can still
do nothing to raise the line’s overall efficiency. Obviously, it
would be quite valuable to have individual efficiency improvements
reflected in the line’s overall efficiency. But we can see
that there is a clear difference between individual efficiency
and overall efficiency.
If we take the same assembly line, remove the electric
conveyor, and instead have the assembly workers lined up
beside one long workbench, the units will gradually begin to
pile up next to certain workers due to individual differences
in pitch. The piles of work-in-process reveal all those hidden
individual differences in pitch.
If we break up the long workbench into individual workbenches
for each worker, then the piles of work-in-process
become even more obvious.
If we separate the individual workbenches by some distance,
it would leave room for work-in-process to pile up
indefinitely. The line would soon lose all signs of having a
production flow. So you can see why JIT professionals have
so little interest in the “coordinated work” arrangement.
This example also underscores the fact that efficiency
improvement has nothing to do with upstream or downstream
processes and has everything to do with raising
efficiency at individual processes. To do this, sometimes
factories “automate” a task that is being performed either
manually or by a simple machine by installing a high-speed
machine, computer-controlled machine, or other absurdly
expensive machine.
I sympathize with such factories, and there are a lot of
them. In fact, I would say that the vast majority of the world’s
factories are guilty of these kinds of mistakes.
I am not denying that individual improvements in efficiency
can add up to an overall improvement throughout the
company. But the improvements have to start with individual
people, machines, and processes, and only then should they be
developed into improvements in line efficiency, factory-wide
efficiency, and company-wide efficiency, including the sales
and distribution arms. It is very important to maintain this
kind of comprehensive view of efficiency improvement.
Once management installs and activates highly sophisticated
and ultra-expensive machinery on the production line
to improve efficiency at certain processes, it is naturally concerned
about getting its money’s worth. This leads it to press
for higher and higher capacity utilization rates. In the meantime,
the idea of letting client orders determine production
output gets put on the back burner.
In this day and age, the comfortable notion that if a product
is made, it will sell one way or another, no longer holds true.
The smart idea for today is, “Let’s make only what will sell, but
make it more efficiently.” Once we take this perspective, pushing
up capacity utilization for its own sake is clearly a mistake.
Pressing and forging processes are prime targets for managers
who limit their view to process-specific efficiency improvements.
Both of these processes require die changeover, which
tends to take a long time. The managers try to minimize this
time consumption by minimizing the number of necessary
die changes. The way to do that is by making fewer models
in larger lots. Soon the factory is back to the old large-lot
orientation. The problem is the managers’ belief that the fewer
the die changes, the higher the efficiency.
These managers have forgotten that production includes
more than pressing and forging processes. Unless production
is made level throughout all processes, the overall result may
well be a loss in efficiency.
The JIT production system not only includes techniques
for thoroughly eliminating waste, it also includes techniques
for creating and maintaining a level production flow. We need
to stand firmly behind both of these principles.
Lesson 8. Where Muddy Streams Appear,
Floods May Follow
Approach to Waste: Just-In-Time and Cost Reduction
“We’ve found it! Now let’s get rid of it!” Words such as these
are often used by improvement teams that finally pinpoint
a true cause of waste, inconsistency, or irrationality and set
about making the improvement to eliminate it.
The Just-In-Time concept is a very effective tool for eliminating
these three evils. It is especially useful for eradicating waste
in such common manifestations as “overproduction waste,”
“idle time waste,” “conveyance waste,” and “warehouse waste.”
Figure 2.14 illustrates some of the essential ingredients in
any well-organized effort to eliminate waste and cut costs