Preventive Maintenance Principles

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

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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.)



Part II: Concepts


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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



Part II: Concepts


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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



Part II: Concepts


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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 II: Concepts


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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 II: Concepts


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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.)



Part II: Concepts


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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



Part II: Concepts


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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 II: Concepts


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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


400 350 300 250


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



Part II: Concepts


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Part V: Conclusion


Avg Queuelength 450


400 350 300 250


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



Part II: Concepts


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Part V: Conclusion


450

Avg Queuelength


400 350 300 250


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



Part II: Concepts


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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 II: Concepts


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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 II: Concepts


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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 II: Concepts


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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



Part II: Concepts


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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



Part II: Concepts


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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

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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



Part II: Concepts


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Part V: Conclusion