22 ◾ Removing the Barriers to Efﬁcient Manufacturing
The implications of equipment breakdowns are universally understood.
For example, here is an actual vision statement that was used on a multimil-
lion-dollar maintenance initiative by a large corporation:
Our Machines Don’t Break Down
If only that were true. Instead, many of us struggle daily to keep our
machines running from one production batch to the next, hoping to get
through with a minimum number of interruptions, all of which introduce
variability. If you want to get beyond this, you simply must make the pro-
cess more reliable, and the ﬁrst step is a comprehensive maintenance plan.
To start with some basics, there are three well-known maintenance strategies:
1. Preventive maintenance (PM): This consists of replacing parts at estab-
lished intervals that are shorter than expected failure intervals and per-
forming recurring services like lubrication and adjustment. The strategy is
to plan the jobs and then perform the work during scheduled downtimes.
2. Predictive maintenance (PdM): PdM consists of monitoring the condi-
tion of the process while it is running and then planning the indicated
repairs to be performed during scheduled downtimes (or sooner if the
3. Total productive or operator-assisted maintenance (TPM): Operators are
trained to perform limited maintenance tasks to prevent small problems
from becoming bigger, like making adjustments and replacing consum-
able parts. They also assist technicians during maintenance downtimes
or whenever needed.
We will need all three.
Preventive maintenance (PM) is the maintenance most familiar to us.
Obviously, there are recurring maintenance tasks that must be done at
speciﬁc intervals to prevent failures and extend the life of any type of
equipment. Filters have ﬁnite lifetimes, lubricants break down with heat or
become contaminated, and some machine parts wear from the moment they
are placed in service and will only last a certain number of hours. Failure to
do the required PM tasks will have signiﬁcant consequences.