Preventive Maintenance Principles

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: ¾ Roger Nuffer ¾ David Villareal ¾ Marcus Hunsaker

¾ Intel Employees: ¾ Jonathan Matthews ¾ David Latham ¾ Eli Sorenson ¾ Danny 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 principreventive maintenance schedule

¾ Awareness of specific challenges to implementing preventive maintenance

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

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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)

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()

Drop Page Fields Here

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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 Sim ulation

Ave

rage

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ngth

# o

f Lot

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1 - 10h mean, 2 CV

Avg Queuelength

Day

Scenar

Data from a simulation run at Intel Fab 11X.

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83 88 93

()


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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


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84 91 102 125 148 160 173 196 209 225 238 273 279 287

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116 138 230 261


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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

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4 - 2h mean, 3 CV

Drop Page Fie ds Here

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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 lotcycle time! ¾

¾ Regardless of the mean, performing PMs inconsistentlyis functionally equivalent to consistently having muchlonger 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 forBritish aircraft maintenance

¾ Background theory: unscheduled downtime shouldbe a random phenomenon

¾ If all unscheduled downtime events are plotted withrespect to the last PM, there should not be anypattern evident

¾ A pattern of increased unscheduled downtimeimmediately following PM’s is a “WaddingtonEffect”



Information from a presentation given at Intel Fab 11X.

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The “Waddington Effect”

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0.5 1 1.5 2 2.5 3 3.5 4 4.5

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"Waddington Effect" Report - Trend of Unscheduled Downtime Frequency Following PMs for the last 12 work weeks

Days since End of Last PM

# of

Uns

ched

uled

Dow

n Ev

ents

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

preventive maintenancein 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

organizationalperformance


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 bestlong-term strategy to maintain equipment

¾ PM scheduling and strategy are keys to maximizing outputwhile reducing work-in-process inventory

¾ Due to short-term cost increases and local optimums, there arebarriers to implementing a preventive maintenance strategy atsome 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: 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


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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 maintenance Concluding 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


Documents

Preventive Maintenance Principles