These ingredients are described below.
1. Cycle time is determined by the required amount
Usually, factory managers use equipment capacity and/or
manpower resources as a basis for determining the cycle
time or pitch. That is a big mistake. If, for instance, we
know that our equipment can handle a 20-second pitch,
but our client orders are not enough to cover the resulting
amount of production volume, we are going to have
a product glut. Conversely, if we select a pitch that is
too slow to keep up with client orders, we will have a
product shortage.
Obviously, the right thing to do is make client orders the
basis for setting the cycle time or pitch.
2. Production is “pulled” by downstream processes
Unlike the flow of rivers, the impetus for the production
flow should not be upstream processes “pushing”
the work-in-process to downstream processes, but rather
downstream processes “pulling” the work-in-process from
upstream processes. In other words, the worker at the next
process is truly the customer in that he or she goes to the
“store” (the previous process) and “buys” what is needed.
This effectively prevents unneeded work-in-process from
being passed downstream.
3. Implement flow manufacturing
Just-In-Time production is impossible as long as work-inprocess
is grouped into lots, which we call “shish-kabob”
production. Instead, work-in-process must move in single
units all along the “flow manufacturing” line.
4. Use kanban and conveyors between appropriate processes
Flow manufacturing stands at the very core of Just-InTime
production and is therefore essential to the JIT production
system. However, the current level of technology
for certain processes that involve heat treatment or gilding
still require the lot production method (or subcon-tracting). It is therefore appropriate to use kanban and
conveyors between these processes.
5. Level production is a prerequisite
In order to make all of the factory’s processes flow as
level as possible, we need to have a thoroughly even distribution
of product models and volumes. Once we have
leveled the assembly lines, we can synchronize them
and level them with the subassembly lines, and finally
the parts processing lines.
Lesson 9. The Amount of Cost Reduction Achieved
Is Proportionate to the Amount of Effort Invested
When Economical Lot Sizes Are Not Economical
As mentioned earlier, pressing and forging processes require
metal dies. Drilling processes need bits, and cutting processes
need blades. As for the assembly processes, they
need to deal with multiple components. None of these facts
pose any problems as long as the factory produces only one
product model. But single-product factories are an endangered
species.
In today’s manufacturing world, factories must always be
switching their production from one product model to the
next. Naturally, this means that metal dies must be changed
at pressing and forging processes. Drill bits and blades need
to be changed at drilling and cutting processes. And component
sets need to be changed at assembly processes. We use
the term “changeover” in reference to all of these types of
equipment set-up work.
Not surprisingly, workers tend to dislike changeover and
would much prefer to avoid product model changes by sticking
with single-model large-lot production. Large lots are
naturally more popular at factories than small ones. But
anyone responsible for managing the company’s operating
capital will be quick to point out that there must be limits to