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 Total
Productive Maintenance (TPM) is the maintenance sub-system of Lean
Manufacturing. TPM improves
manufacturing performance by reducing cost, improving quality and
increasing productivity.
As with other parts of Lean, TPM
borrows
tools and techniques from other disciplines as well as
previously
developed and proven maintenance techniques. The combination,
integrated as a system and further integrated with the larger Lean
system, produces results far beyond the individual techniques; i.e.,
the system is more than the sum of its parts.
Losses & Cost Avoidance
In one sense, everything in maintenance
is waste since none of it directly contributes
to the customer's needs and wants. While a perfect factory with
perfect equipment would need zero maintenance effort, real factories
and real equipment need maintenance to function. Without
it, they create further waste in lost time and defects.
The
objective of TPM is to minimize the total waste or, in TPM terms,
loss.
Maintenance-related losses come in many
forms. Accounting systems show some costs (losses) but others
remain hidden as in figure 1. For example, the exact cost of maintenance labor
and parts is easy to track. The cost of a defective part is somewhat
easy to track but the "commotion cost" of the defect is nearly
impossible to track and usually much greater. For an example, see:
The True Cost of Defective Quality.
Figure 2 Optimizing
Maintenance Cost
 The trick is to find the
balance between
direct maintenance expenditures and the hidden costs while ensuring
that maintenance resources are effectively used. Analytically and
quantitatively, this is very difficult. From this author's
experience and observation, however, few (if any) factories spend
too much on maintenance. Most operate far to the left on the total
Cost Curve of figure 2. Well-managed maintenance is nearly
always a good investment.
The Origins of TPM
The demands for predictable machine
performance in Lean Manufacturing led to the development of TPM. Early on, the people at
Toyota must have realized that many quality problems and setup
problems originated in poor maintenance. Total Quality Techniques, Statistical Process Control (SPC) and problem solving teams
transferred well to maintenance issues. Reliability Centered
Maintenance (RCM) also contributed. Reliability Centered Maintenance
developed from the military's development of Reliability theory
which, in turn, came from statistical theory. Statistical theory
also contributed to the development of SPC. The use of problem
solving teams came from Eric Trist's
Socio-Technical Systems as well as
from Reg Revans'
Action Learning. Figure 3
is a simplified
summary of TPM's development.
Results
Some
years ago I was Maintenance Superintendant in a large, 100-year-old
steel foundry. We employed most of the principles, tools and
techniques of TPM long before they had names. The results were
excellent. For example, our average
downtime on overhead cranes went from about 17% to 2.5%.
Other major equipment showed comparable results. Here are
some other results reported by industry:
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MRC Bearings reduced
unplanned downtime by 98% in one cell and 99% in another - all
within one year.
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Monsanto runs their
three-year old TPM start-up plant at 97% on-stream time while
most other units run between 85% and 90%.
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3M reduced their maintenance
cost by 60% within three years.
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DuPont reduced off-quality
by 69% and improved capacity by 29% in three years.
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Harley-Davidson estimates
that the ROI from TPM has been ten-fold to the cost of
implementation.
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Kodak reported a $5 million
investment in TPM that resulted in a $16 million increase in
profits.
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Figure 1 Maintenance
Losses
Figure 3 Origins of Total
Productive Maintenance
TPM In A Nutshell
(Click to Enlarge)
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