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Lean
Resources
Seminars
Planning,
Leading & Managing The Lean Manufacturing Journey
Thus,
then, in Strategy everything is very simple, but not on that account very
easy.
--Carl
von Clauswitz
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A
Mental Model
Taiichi
Ohno and Shigeo Shingo
developed and implemented Lean
Manufacturing at Toyota over a period of 20-30 years. Their
approach provides a mental model for
other implementations.
Ohno
first visualized an ideal production
system, in terms of workflow.
Ohno's ideal system was inspired Eiji Toyoda's observations at Ford Motor
Company. The ideal production system was a series of adjacent workstations that were balanced
and synchronized with no inventory between stations. It delivered
finished product to the customer exactly when needed (Just In Time)
and drew materials, Just In Time.
According
to legend, Ohno asked Shingo and others what prevented the
realization of this ultimate, no-inventory
system. As the reasons |
surfaced,
Ohno requested his deputies to "eliminate
the reasons."
The
resulting elements of Lean Manufacturing aim at eliminating (or at
least reducing) the reasons for inventory. While the real goal is to
eliminate waste, Ohno understood
that inventory
mirrors waste.
This
is an example of what Edward DeBono calls "Lateral
Thinking." By imagining an ideal, but impossible
situation, we can often see more clearly, the path to its
realization.
Ohno
and Shingo did not intend to develop some sort of "Unified
Field Theory" for all manufacturing. They simply wanted to
solve Toyota's specific problems. The
solutions they chose, while broad based, do not necessarily apply in
all situations. Your solutions may be different. |
Using
The Mental Model
First,
imagine the ultimate factory as shown above with your
products and customers. Then ask the following questions:
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What
would be the characteristics of the equipment, people and
layout in this factory?
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What
must be true for this to be possible?
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What
are the root
causes for inventory in our plant?
An
Example
In
many factories a primary "reason
for inventory" involves intertwined issues of equipment
scale, setup, batching,
and workflow. The causal
diagram (below) illustrates.
The
problem starts with equipment that is
larger and faster than required for a single product.
This causes multiple products to run on the same equipment. Two
effects ensue:
1)
Changeovers become necessary.
2)
Different products follow different routes. |
In
addition, large-scale equipment often requires difficult
and time-consuming setups. The combination of
changeover and long setup forces large batches that promote high
inventory. Different routes
force functional layouts with complex flows that also increase
inventory.
High
inventory brings all sorts of waste in material handling,
space and quality (not shown). This diagram is over-simplified. In
reality, it has multiple, subtle
reinforcing loops that exacerbate the problem over time.
At
Toyota, Shingo attacked both root
causes. First, he developed the SMED
system that reduced changeover times and, thus, batch sizes and
inventory. Second, he scaled down the equipment, where possible,
thus enabling Cellular
Manufacturing and its simplified workflow.
SMED
and workcells did not become part of
the Toyota Production System because they had some sort of cosmic
virtue. They were employed because they
reduced inventory and waste in the
Toyota context. |
Causal
Diagram
The
Key Point
Systems
Thinking visualizes causes and effects,
interactions and dynamic behaviors. Both Systems Thinking and
Lateral Thinking are important when developing a Lean
Manufacturing Strategy for your particular plant. This
is where leadership
plays a key role.
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Our
Mental Model is simple; the implications profound. It led
Toyota to setup reduction, workcells and, eventually, the other
tools of Lean Manufacturing. In other situations, it may lead to a
somewhat different set of tools. The moral is:
Our
additional pages detail procedures
for developing your own Strategy
and implementation plan.
Quarterman
Lee |
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