Page 34 - How To Implement Lean Manufacturing

Lean Manufacturing and the Toyota Pr oduction System 15

or quick changeovers. With SMED technology, the need to oversize the machinery is
dramatically reduced. In addition, the need to hold inventory is also reduced. SMED
technology was developed and refined by Toyota. Shigeo Shingo not only designed
much of it, he published several books on the subject and is considered the architect of
SMED technology. SMED is a staple in the Lean toolbox.

Transportation of Goods
How parts, finished goods, and subassemblies are transported in the plant in the Mass-
Prod seldom looks like a Lean facility. Nearly all materials are “pushed” and huge
volumes of WIP build up between processing steps, taking up space and greatly inflating
both inventory and operating costs. More and more, even in a MassProd facility, raw
materials are being handled like in a Lean facility—Lean in the sense that kanban cards
are used for raw materials replenishment. However, there the similarities end. In the
MassProd system, often kanban cards are used but the entire kanban system is not
employed. Rather, kanban rules are seldom followed; the most egregious errors being:
• The failure to reduce the number of kanban to achieve process improvement
• The willingness to transport defective products
These two rules are always followed in a Lean plant, along with the other four rules
of kanban (see Chap. 3 for a discussion of kanban). However, in MassProd, seldom is
kanban used for subassemblies and for finished goods. Rather the demand is scheduled
and the volume is pushed through the system until it shows up at the storehouse. Huge
volumes of inventory accumulate in the process, and the lead time is both long and
unknown. The Lean solution is again a huge paradigm shift. In Lean, a pull system is
used as described above. and inventory is volume, time, and location controlled. In
addition, kanban was an invention of the TPS and they use it not only for raw materials,
finished goods, and subassemblies, but for such items as tools as well.

Handling Product Demand and Supply Variations
How finished product demand and supply variations are handled in a MassProd facility
is a function of the scheduling. As demands change or production rates vary, the
scheduler tries to manipulate the planning program to respond. This is a terribly inef-
fective solution that leads to not only a lot of overtime, a lot of expediting, a large num-
ber of late shipments but very large inventories as well. In addition, it leads to very high
levels of uncertainty and stress. Adjusting to these demand and supply variations in
this manner is not only ineffective, it is frequently impossible. The planning model is
designed to be updated weekly or sometimes daily, for example, but the production
volume is changing hourly or by the minute, thus there is no way the planning model
can be responsive enough to the actual production line needs.
In the Lean solution, the effort to respond to demand and production variations is
accounted for by two factors. First, the variation in the processes is considered a huge
problem and so is attacked from that standpoint. Stable processes are a foundational
issue in Lean, and are taken care of early in the initiative. As a result, variations are
dramatically reduced through good process management. Second, the variations that
remain are managed by segregating the inventory into logical categories and responding
to inventory withdrawals with problem solving when appropriate. These inventory
segregations are: