Overview for using reliability tools to improve new product development

1. Reliability – Lesson 1
The Basics 1

2. RELIABILITY - LESSON ONE
Overview:
 Application of Reliability in different industries
 Importance of Reliability – Cost Impact
 Bathtub curve
 Predictability vs. Failure Mode Avoidance
 P-Diagram
 Strategies for Improvement
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3. QUOTES
―A man who lacks reliability is utterly useless.‖
Confucius (551-479)
―Engineering is the science of economy, of
conserving the energy, kinetic and potential,
provided and stored up by nature for the use of
man. It is the business of engineering to utilize
this energy to the best advantage, so there may
be the least possible waste.‖
Willard A. Smith (1908)
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4. RELIABILITY - DEFINITION
 Wikipedia - the ability of a system or
component to perform its required functions
under stated conditions for a specified period
of time.
 ASQ – the probability that an item can
perform its intended function for a specified
interval under stated conditions
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5. RELIABILITY - APPLICATIONS
Products:
 Design for Reliability
 Software
Equipment:
 Reliability Centered Maintenance
Medical – Survival rate
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6. RELIABILITY - COMPARISON
Reliability field
Nuclear Aerospace Medical Consumer Products
Reliability Criteria
# units in field 00 000 00000000 00000000
Quality of field records:
Failed units excellent excellent Reasonable>good fair
Unfailed units excellent excellent none none
Units lost to follow-up no no often yes
Noise space simple moderate complicated complicated
Competing risks no no yes yes
Key Reliability redundancy, redundancy, intervention robustness,
Strategy intervention intervention some intervention
Key reliability measure probability probability cure rate and side effects distance from failure modes
Memo: Design improvement yes yes no yes
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7. WHY IS RELIABILITY IMPORTANT ?
 Safety
 Customer Satisfaction
 Warranty Costs
 Reputation
 Repeat Business
 Cost Analysis
 Customer Requirements
 Competitive Advantage
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8. RELIABILITY IMPROVEMENT PROCESS
 Set goals & requirements (customer driven)
 Perform an assessment
 Testing
 Data collection
 Failure reporting, analysis and corrective
action system (FRACAS)
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9. VOCABULARY
 Mean Time to Failure (MTTF)
 Mean Time Between Failures (MTBF)
 Hard Failures – product function ceases
 Soft Failures – degraded to unacceptable level
 Failure rate
 Hardware Breakdown Structure
 FMEA – Failure Modes, Effects & Analysis
 SPC – Statistical Process Control
 DOE – Design of Experiments
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10. LIFE CYCLE COST
 ―It’s unwise to pay too much, but it’s foolish to
spend too little‖— John Rustin
 Present Value vs. Future Value of money
 Acquisition Costs
 Sustaining Costs
 Cost Breakeven
 Include Cradle-to-Grave costs converted to
NPV models
http://www.barringer1.com/pdf/LifeCycleCostSummary.pdf
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11. LIFE CYCLE COST
$30,000
$25,000
$20,000
C
o
$15,000
s Product A
t
Product B
$10,000
$5,000
$0
1 2 3 4 5 6 7 8 9
Years in Service
Product B has a lower acquisition cost but needs repaired more often and at
greater expense 1
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12. RELIABILITY RELATED COSTS
 Prevention activities - intended to ensure that
processes work without fail, such as failure mode
and effects analysis, training and preventive
maintenance
 Appraisal activities - how well processes such as
product and process approvals are actually working
via activities such as inspection and testing
 Failure costs - related to failures that do occur and
are further classified as internal (failure identified
before it reached the customer) or external
(detected after reaching the customer). The time
and expense of reprocessing failed products or
services and investigating failures could fall into
either failure category, depending on when the
event occurs. Warranty costs are decidedly
external failures. 1

13. BATHTUB CURVE
Number
of Infant
failures Mortality
Time
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14. BATHTUB CURVE
Number
of Infant
failures Mortality
Useful Life
Time
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15. BATHTUB CURVE
Number
of Infant Wearout
failures Mortality
Useful Life
Time
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16. RELIABILITY PREDICTABILITY
Reliability is the probability that an item can
perform its intended function for a specified
interval under stated conditions, However:
 We do not have access to all products in the
field, particularly those that have not failed
 We cannot specify a period of time to
measure reliability
 We cannot specify a set of operating
conditions
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17. RELIABILITY IS FAILURE MODE AVOIDANCE
 Reliable products are robust and mistake free
 Failure modes of our products are primarily that
something breaks or performance degrades
 Avoiding failure modes will decrease the
probability of failure
 Reliability prediction is not easy for many
industries
 We need to reduce variation and the sensitivity
to noise (ie. Six Sigma and P-diagram)
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18. P-DIAGRAM
P-Diagram
Noise Factors
1
2
3
Input Signal Ideal Function
System
Error State
Control Factors 1
1 2
2 3
3
4
5
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19. P-DIAGRAM DEFINITIONS
 Ideal Function – primary intended function of
the design
 Input Signal – energy which is put into the
system to make it work
 Error State – undesirable output of the
system
 Control Factors – features that can be
controlled by design or process
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20. NOISE FACTORS
Sources of disturbing influences that can
disrupt ideal function, causing error states
which lead to quality problems
 Product variations
 Changes over time/usage
 Customer duty cycle
 External environment
 System interactions
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21. P-DIAGRAM EXAMPLE
P-Diagram
Self contained jet pack Noise Factors
1. Fuel volatility
2. Wind
3. Temperature
Input Signal Ideal Function
Throttle position System Lifts person off ground
Error State
1. No ignition
Control Factors
1. Material properties 2. Flame too large
2. Design
3. Manufacturing process
4. Assembly process
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22. FMEA
 Bring P-Diagram
 List error states (potential failure modes)
 Ties together P-Diagram and Testing
 Living and changing document
 Discovery, legal document
 Ultimate failure mode avoidance document
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23. TESTING
 Captures the effects of noise factors over useful
life
 Generates a measurable event
 Generates a failure of degradation of the ideal
function
 Generates results which are directly correlated
with real-world performance
 Can be accelerated for reliability improvement
experiments (HALT, HASS)
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24. HIGHLY ACCELERATED LIFE TESTING
HALT testing
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25. STRATEGIES FOR IMPROVEMENT
 Change the design concept
 Make basic current design assumptions
insensitive to the noises (beef up design, use
Design of Experiments, redundancy)
 Reduce or remove the noise factor(s)
 Insert a compensation device
 Send the error state/noise elsewhere else
where it will do less harm (disguise effect)
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26. FRACAS
 Failure Reporting, Analysis and Corrective
Action System
 Prioritizes field failures
 Root Cause Investigation Teams
 Needs input from Team members
 Drives problems to closure
 Documentation in central location
 Closed Loop System
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27. SUMMARY
 Application of Reliability in different industries
 Importance of Reliability – Cost Impact
 Bathtub Curve
 Predictability vs. Failure Mode Avoidance
 P-Diagram
 Strategies for Improvement
2

28. WHERE TO GET MORE INFORMATION
 Reliasoft - http://www.reliasoft.com/
 RIAC -
http://src.alionscience.com/src/training.do
 Hobbs Engineering -
http://www.hobbsengr.com/
 ASQ Reliability Div. - http://asq.org/reliability/
 SRE - http://www.sre.org/
 You’ll find many more on the web….
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29. REFERENCES
 Dr. Tim Davis -“Science, engineering, and
statistics”. Applied Stochastic Models in
Business and Industry, 2006, Vol. 22, Issue 5-
6, pp. 401-430
 Dr. Vasiliy Krivstov
 Dr. Paul Barringer
 Reliasoft
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