Preventive Maintenance
Principles
SPL 7.2
Scott Couzens, LFM ’06
Scott Hiroshige, LFM ‘06
Erik Smith, LFM ’03 – Intel Corporation
Presentation for:
ESD.60 – Lean/Six Sigma Systems
MIT Leaders for Manufacturing Program (LFM)
Summer 2004
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 inputs from the
faculty and from the technical instructor, Chris Musso, are reflected in some of the text or in an appendix
Special Thanks to:
¾ Intel Employees:
¾ Jonathan Matthews
¾ David Latham
¾ Eli Sorenson
¾ Danny Miller
¾ DNS Employees:
¾ Roger Nuffer
¾ David Villareal
¾ Marcus Hunsaker
© [LFM Students] – ESD.60 Lean/Six Sigma Systems, LFM, MIT
Part I: Introduction
Part II: Concepts
Part III: Application
6/9/04 -- 2
Part IV: Disconnects
Part V: Conclusion
Overview
¾ Session Design (20-30 min.)
¾ Learning Objectives
¾ Familiarity with the different
types of maintenance
activities
¾ Appreciation of the benefits of
preventive maintenance
¾ Understanding of lean
principles for designing a
preventive maintenance
schedule
¾ Awareness of specific
challenges to implementing
preventive maintenance
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.)
© [LFM Students] – ESD.60 Lean/Six Sigma Systems, LFM, MIT
Part I: Introduction
Part II: Concepts
Part III: Application
6/9/04 -- 3
Part IV: Disconnects
Part V: Conclusion
Types of Maintenance
¾ Breakdown Maintenance:
¾ Waiting until equipment fails before repairing or servicing it
¾ Preventive Maintenance (PM):
¾ (Time-based or run-based) Periodically inspecting, servicing,
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
© [LFM Students] – ESD.60 Lean/Six Sigma Systems, LFM, MIT
Part I: Introduction
Part II: Concepts
Part III: Application
6/9/04 -- 4
Part IV: Disconnects
Part V: Conclusion
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
http://www.prenhall.com/divisions/bp/app/russellcd/PROTECT/CHAPTERS/CHAP15/HEAD01.HTM
© [LFM Students] – ESD.60 Lean/Six Sigma Systems, LFM, MIT
Part I: Introduction
Part II: Concepts
Part III: Application
6/9/04 -- 5
Part IV: Disconnects
Part V: Conclusion
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
Source: Business Dynamics: Systems Thinking and Modeling for a Complex World,
Sterman, John D., 2000.
© [LFM Students] – ESD.60 Lean/Six Sigma Systems, LFM, MIT
Part I: Introduction
Part II: Concepts
Part III: Application
6/9/04 -- 6
Part IV: Disconnects
Part V: Conclusion
The Manufacturing Game Results
¾ Teams who follow a cost-minimization strategy (reactive
maintenance policies) are able to keep costs low for a
while. However, as defects build up they find their
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.
Source: Business Dynamics: Systems Thinking and Modeling for a Complex World,
Sterman, John D., 2000.
© [LFM Students] – ESD.60 Lean/Six Sigma Systems, LFM, MIT
Part I: Introduction
Part II: Concepts
Part III: Application
6/9/04 -- 7
Part IV: Disconnects
Part V: Conclusion
When Does PM Make Sense?
¾ PM makes sense when the cost of doing PM is less than the
cost of NOT doing PM.
PM makes sense if CDoingPM < CNotDoingPM
¾ CDoingPM =
f(hours of not running equipment, loss in employee
morale from doing PM instead of “real work”, materials
and man-hours consumed in PM, potential for making
things worse, etc.)
¾ CNotDoingPM = f(cost of losing/reworking a failed batch (unless PM
makes no difference in preventing the failure), materials
and man-hours spent repairing equipment, loss of
equipment lifetime, loss in employee morale from NOT
doing PM, reduced employee familiarity with equipment,
etc.)
© [LFM Students] – ESD.60 Lean/Six Sigma Systems, LFM, MIT
Part I: Introduction
Part II: Concepts
Part III: Application
6/9/04 -- 8
Part IV: Disconnects
Part V: Conclusion
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
© [LFM Students] – ESD.60 Lean/Six Sigma Systems, LFM, MIT
Part I: Introduction
Part II: Concepts
Part III: Application
6/9/04 -- 9
Part IV: Disconnects
Part V: Conclusion
PM Durations: Simulation 1
¾ Simulation of equipment with a 10 hour average PM duration, std dev 20
hours (85% availability)
Drop Page Fields Here
Trend of Queues for the Toolset
Avg Queuelength
450
Average QueueLength (# of Lots)
400
350
300
250
Scenario
1 - 10h mean, 2 CV
200
150
100
50
0
83 88 99 109114119125133139147152157162167172177182187192198203211216221226231236241246267
Days into Sim ulation
Day
Data from a simulation run at Intel Fab 11X.
© [LFM Students] – ESD.60 Lean/Six Sigma Systems, LFM, MIT
Part I: Introduction
Part II: Concepts
Part III: Application
6/9/04 -- 10
Part IV: Disconnects
Part V: Conclusion
PM Durations: Simulation 2
¾ Simulation of equipment with a 5 hour average PM duration, std dev 10
hours (85% availability)
Drop Page Fields Here
Trend of Queues for a Toolset
Avg Queuelength
450
Average QueueLength (# of Lots)
400
350
300
250
Scenario
2 - 5h mean, 2 CV
200
150
100
50
0
83
88
93
98 103 108 113 118 125 137 155 164 194 201 213 228 233 244 259 264 277 285
Days into Sim ulation
Day
Data from a simulation run at Intel Fab 11X.
© [LFM Students] – ESD.60 Lean/Six Sigma Systems, LFM, MIT
Part I: Introduction
Part II: Concepts
Part III: Application
6/9/04 -- 11
Part IV: Disconnects
Part V: Conclusion
PM Durations: Simulation 3
¾ Simulation of equipment with a 2 hour average PM duration, std dev 4
hours (85% availability)
Drop Page Fields Here
Trend of Queues for a Toolset
Avg Queuelength
450
Average QueueLength (# of Lots)
400
350
300
250
Scenario
3 - 2h mean, 2 CV
200
150
100
50
0
84
91
102 116
125
138
148 160
173
196
209 225
230
238
261
273 279
287
Days into Sim ulation
Day
Data from a simulation run at Intel Fab 11X.
© [LFM Students] – ESD.60 Lean/Six Sigma Systems, LFM, MIT
Part I: Introduction
Part II: Concepts
Part III: Application
6/9/04 -- 12
Part IV: Disconnects
Part V: Conclusion
PM Durations: Simulation 4
¾ Simulation of equipment with a 2 hour average PM duration, std dev 6
hours (85% availability)
Drop Page Fields Here
Trend of Queues for a Toolset
450
Avg Queuelength
Average QueueLength (# of Lots)
400
350
300
250
Scenario
4 - 2h mean, 3 CV
200
150
100
50
0
84 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
Days into Simulation
Day
Data from a simulation run at Intel Fab 11X.
© [LFM Students] – ESD.60 Lean/Six Sigma Systems, LFM, MIT
Part I: Introduction
Part II: Concepts
Part III: Application
6/9/04 -- 13
Part IV: Disconnects
Part V: Conclusion
PM Durations: Why they matter
¾ For the exact same availability on a piece of equipment:
Simulation
Avg QueueLength
StdDev QueueLength
1) µ=10h, σ=20h
56
63
2) µ=5h, σ=10h
38
52
3) µ=2h, σ=4h
8
8
4) µ=2h, σ=6h
56
57
¾ Shorter PM durations mean a difference in days of lot
cycle time!
¾ Each day of factory cycle time = millions of $$
¾ Regardless of the mean, performing PMs inconsistently
is functionally equivalent to consistently having much
longer downtime durations
Data from simulations run at Intel Fab 11X.
© [LFM Students] – ESD.60 Lean/Six Sigma Systems, LFM, MIT
Part I: Introduction
Part II: Concepts
Part III: Application
6/9/04 -- 14
Part IV: Disconnects
Part V: Conclusion
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.
© [LFM Students] – ESD.60 Lean/Six Sigma Systems, LFM, MIT
Part I: Introduction
Part II: Concepts
Part III: Application
6/9/04 -- 15
Part IV: Disconnects
Part V: Conclusion
The “Waddington Effect”
"Waddington Effect" Report - Trend of Unscheduled Downtime
Frequency Following PMs for the last 12 work weeks
70
# of Unsched Downs
# of Unscheduled Down Events
60
50
Event_Type
40
REPAIR
QUAL
30
OUT OF CNTRL
20
10
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
Days since End of Last PM
Days Since PM
¾ Impact of Waddington Effect = 1.4% Availability
Data from a set of production tools at Intel Fab 11X.
© [LFM Students] – ESD.60 Lean/Six Sigma Systems, LFM, MIT
Part I: Introduction
Part II: Concepts
Part III: Application
6/9/04 -- 16
Part IV: Disconnects
Part V: Conclusion
Challenges to Implementing
Preventive Maintenance
¾ Social Factors
¾ Technical Factors
¾ Organizations are
frequently structured in
ways that promote local
optimums (cost, shiftly
output goals, etc.)
¾ Breakdown maintenance
is typically cheaper than
preventive maintenance
in the short-term
¾ The benefits of preventive
maintenance are not
always well understood
¾ Under-trained technicians
can cause more damage
than they prevent
¾ The focus on minimizing
maintenance costs has to
shift to maximizing overall
organizational
performance
© [LFM Students] – ESD.60 Lean/Six Sigma Systems, LFM, MIT
Part I: Introduction
Part II: Concepts
Part III: Application
6/9/04 -- 17
Part IV: Disconnects
Part V: Conclusion
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
© [LFM Students] – ESD.60 Lean/Six Sigma Systems, LFM, MIT
Part I: Introduction
Part II: Concepts
Part III: Application
6/9/04 -- 18
Part IV: Disconnects
Part V: Conclusion
Appendix: Instructor’s Comments and Class
Discussion for 7.2
¾ PM is an important tool for establishing stability
necessary for other lean elements:
¾ Andon, 5s, etc.
¾ How do you escape the crisis management
whirlpool?
¾ Social disconnects:
¾Change the mindset of management, maintenance
group from reaction to prevention
¾May need to be done in steps
© [LFM Students] – ESD.60 Lean/Six Sigma Systems, LFM, MIT
6/9/04 -- 19
Appendix: Instructor’s Guide
Slide
Time
Topic
Additional Talking Points
1-3
2-3 min
Introduction, overview and
learning objectives
• Acknowledge contributors to the presentation
• Provide an overview of the learning objectives
4-5
3-5 min
Key Concepts
• Describe the 3 types of maintenance
• Explain the benefits of preventive maintenance
6-15
7-15 min
Exercises/Activities
• Go through the key learnings of the Manufacturing
Game
• Go through a PM optimization example
• Discuss “Waddington Effect”
16
2-3 min
Disconnects
• Discuss the difficulties of implementing preventive
maintenance in a reactive maintenance culture
17
1-2 min
Concluding comments
• Summarize key points of preventive maintenance
© [LFM Students] – ESD.60 Lean/Six Sigma Systems, LFM, MIT
Part I: Introduction
Part II: Concepts
Part III: Application
6/9/04 -- 20
Part IV: Disconnects
Part V: Conclusion