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Preventive Maintenance
Principles
SPL 7.2
Scott Couzens, LFM ’06
Scott Hiroshige, LFM ‘06
Presentation for:
Summer 2004
i
Erik Smith, LFM ’03 – Intel Corporation
ESD.60 – Lean/Six Sigma Systems
MIT Leaders for Manufacturing Program (LFM)
These materials were developed as part of MIT's ESD.60 course on "Lean/Six Sigma Systems." In some cases,
the materials were produced by the lead instructor, Joel Cutcher-Gershenfeld, and in some cases by student teams
working with LFM alumni/ae. Where the materials were developed by student teams, additional nputs from the
faculty and from the technical instructor, Chris Musso, are reflected in some of the text or in an appendix

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Special Thanks to:
¾ DNS Employees:
¾Roger Nuffer
¾David Villareal
¾Marcus Hunsaker
¾ Intel Employees:
¾Jonathan Matthews
¾David Latham
¾Eli Sorenson
¾Danny Miller
9/04 --LFM Students] – ESD.60 Lean Six Sigma Systems, LFM, MIT
Part I: Introduction Part II: Concepts Part III: Application Part IV: Disconnects Part V: Conclusion

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Overview
¾ Learning Objectives
¾
types of maintenance
activities
¾ Appreciation of the benefits of
preventive maintenance
¾ Understanding of lean
princi
schedule
¾ Awareness of specific
challenges to implementing
¾ Session Design (20-30 min.)
¾ Part I: Introduction and Learning
Objectives (1-2 min.)
¾ Part II: Key Concept or Principle
Defined and Explained (3-5 min.)
¾ Part III: Exercise or Activity
Based on Field Data that
Illustrates the Concept or
Principle (7-10 min.)
¾ Part IV: Common “Disconnects,”
Relevant Measures of Success,
and Potential Action
Assignment(s) to Apply Lessons
Learned (7-10 min.)
¾ Part V: Evaluation and
Concluding Comments (2-3 min.)
Familiarity with the different
ples for designing a

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Types of Maintenance
¾ Breakdown Maintenance:
¾ Waiting until equipment fails before repairing or servicing it
¾ Preventive Maintenance (PM):
¾
cleaning, or replacing parts to prevent sudden failure
¾ (Predictive) On-line monitoring of equipment in order to use
important/expensive parts to the limit of their serviceable life
¾ Corrective or Predictive Maintenance:
¾ Improving equipment and its components so that preventive
maintenance can be carried out reliably
(Time-based or run-based) Periodically inspecting, servicing,

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Benefits of Preventive Maintenance
¾ “…the cost of breakdown maintenance is usually much
greater than preventive maintenance.” 1
¾ Preventive maintenance…
¾ Keeps equipment in good condition to prevent large problems
¾ Extends the useful life of equipment
¾ Finds small problems before they become big ones
¾ Is an excellent training tool for technicians
¾ Helps eliminate rework/scrap and reduces process variability
¾ Keeps equipment safer
¾ Parts stocking levels can be optimized
¾ Greatly reduces unplanned downtime
1
/ l
http://www.prenhall.com divisions/bp/app/russel cd/PROTECT/CHAPTERS/CHAP15/HEAD01.HTM

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The Manufacturing Game
¾ Similar to the Beer Game
¾ Simulates a typical plant with three roles:
¾ Operations Manager
¾ Maintenance Manager
¾ Spare Parts Stores Manager
¾ Each round, participants make decisions such as:
¾ Which equipment to take down for PMs
¾ How to allocate maintenance resources
¾ How many spare parts to order
¾ Revenue, cost, output, uptime, inventory are recorded
i
Source: Business Dynam cs: Systems Thinking and Modeling for a Complex World,
Sterman, John D., 2000.

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The Manufacturing Game Results
¾ Teams who follow a cost-minimization strategy (reactive
maintenance policies) are able to keep costs low for a
uptime falling and costs rising.
¾ Teams who follow a preventive maintenance strategy
initially find higher costs and reduced uptime as
equipment is taken offline for planned maintenance.
Soon, however, these teams begin to greatly outperform
teams following a cost-minimization strategy.
i
while. However, as defects build up they find their
Source: Business Dynam cs: Systems Thinking and Modeling for a Complex World,
Sterman, John D., 2000.

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When Does PM Make Sense?
¾ PM makes sense when the cost of doing PM is less than the
cost of NOT doing PM.
¾ CDoingPM =
and man-hours consumed in PM, potential for making
things worse, etc.)
¾ CNotDoingPM =
makes no difference in preventing the failure), materials
and man-hours spent repairing equipment, loss of
etc.)
PM makes sense if C < C
f(hours of not running equipment, loss in employee
morale from doing PM instead of “real work”, materials
f(cost of losing/reworking a failed batch (unless PM
equipment lifetime, loss in employee morale from NOT
doing PM, reduced employee familiarity with equipment,
DoingPM NotDoingPM

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Optimizing a PM Schedule
¾ Question:
¾ If a certain piece of production equipment requires ~10 hours of
preventive maintenance per week, how should those 10 hours
be scheduled?
¾ Answer:
¾ In a 24x7 manufacturing operation, it is typically better to
perform the ~10 hours of activities in several smaller periods of
time, for instance 5 PM activities that take ~2 hours each
¾ Duration and variability in preventive maintenance are key
factors in whether equipment will be able to maintain a steady
flow of output

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PM Durations: Simulation 1
¾
hours (85% availability)
0
50
100
150
200
250
300
350
400
450
()
Drop Page Fields Here
io
Simulation of equipment with a 10 hour average PM duration, std dev 20
Trend of Queues for the Toolset
83 88 99 109114119125133139147152157162167172177182187192198203211216221226231236241246267
Days into Simulation
AverageQueueLength#ofLots
1 - 10h mean, 2 CV
Avg Queuelength
Day
Scenar
Data from a simulation run at Intel Fab 11X.

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¾
0
50
100
150
200
250
300
350
400
450
83 88 93
()
io
Trend of Queues for a Toolset
98 103 108 113 118 125 137 155 164 194 201 213 228 233 244 259 264 277 285
2 - 5h mean, 2 CV
Avg Queuelength
Day
Scenar

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¾
0
50
100
150
200
250
300
350
400
450
84 91 102 125 148 160 173 196 209 225 238 273 279 287
()
io
116 138 230 261
3 - 2h mean, 2 CV
Avg Queuelength
Day
Scenar

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¾
0
50
84
l
100
150
200
250
300
350
400
450
98 112 117 122 127 133 138 143 148 153 158 163 168 173 178 183 188 193 204 222 242 258 264 275 286 291
AverageQueueLength(#ofLots)
4 - 2h mean, 3 CV
Drop Page Fie ds Here
Avg Queuelength
Day
Scenario

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PM Durations: Why they matter
¾ For the exact same availability on a piece of equipment:
¾ Shorter PM durations mean a difference in days of lot
cycle time!
¾
¾ Regardless of the mean, performing PMs inconsistently
is functionally equivalent to consistently having much
longer downtime durations
57564) µ=2h, σ=6h
883) µ=2h, σ=4h
52382) µ=5h, σ=10h
63561) µ=10h, σ=20h
StdDev QueueLengthAvg QueueLengthSimulation
Each day of factory cycle time = millions of $$
Data from simulations run at Intel Fab 11X.

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The “Waddington Effect”
¾ First observed by C.H. Waddington during WWII for
British aircraft maintenance
¾ Background theory: unscheduled downtime should
be a random phenomenon
¾ If all unscheduled downtime events are plotted with
respect to the last PM, there should not be any
pattern evident
¾ A pattern of increased unscheduled downtime
immediately following PM’s is a “Waddington
Effect”
Information from a presentation given at Intel Fab 11X.

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The “Waddington Effect”
0
10
20
30
40
50
60
70
0.5 1 1.5 2 2.5 3 3.5 4 4.5
¾
"Waddington Effect" Report - Trend of Unscheduled Downtime
Frequency Following PMs for the last 12 work weeks
Days since End of Last PM
#ofUnscheduledDownEvents
REPAIR
QUAL
OUT OF CNTRL
# of Unsched Downs
Days Since PM
Event_Type
Impact of Waddington Effect = 1.4% Availability
Data from a set of production tools at Intel Fab 11X.

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Challenges to Implementing
Preventive Maintenance
¾ Technical Factors
¾ Breakdown maintenance
in the short-term
¾ Under-trained technicians
can cause more damage
¾ Social Factors
¾ Organizations are
output goals, etc.)
¾
always well understood
¾ The focus on minimizing
organizational
performance
is typically cheaper than
than they prevent
frequently structured in
ways that promote local
optimums (cost, shiftly
The benefits of preventive
maintenance are not
maintenance costs has to
shift to maximizing overall

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Concluding Comments
¾ Performing preventive maintenance is almost always the best
long-term strategy to maintain equipment
¾ PM scheduling and strategy are keys to maximizing output
while reducing work-in-process inventory
¾ Due to short-term cost increases and local optimums, there are
barriers to implementing a preventive maintenance strategy at
some plants

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Appendix: Instructor’s Comments and Class
Discussion for 7.2
¾ PM is an important tool for establishing stability
necessary for other lean elements:
¾Andon, 5s, etc.
¾ How do you escape the crisis management
whirlpool?
¾Social disconnects:
¾Change the mindset of management, maintenance
group from reaction to prevention
¾May need to be done in steps

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Appendix: Instructor’s Guide
•1-2 min17
•Disconnects2-3 min16
•
Game
• i
• Discuss “Waddington Effect”
Exercises/Activities6-15
4-5
1-3
Slide
•
•
Key Concepts3-5 min
•
• iveslearning objectives
2-3 min
Additional Talking PointsTopicTime
Summarize key points of preventive maintenanceConcluding comments
Discuss the difficulties of implementing preventive
maintenance in a reactive maintenance culture
Go through the key learnings of the Manufacturing
Go through a PM optim zation example
7-15 min
Describe the 3 types of maintenance
Explain the benefits of preventive maintenance
Acknowledge contributors to the presentation
Provide an overview of the learning object
Introduction, overview and

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