Systems Engineering

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Systems Engineering Risk Analysis with FMEA

• Special Topics
• Fishbone Chart
• FMEA

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Risk/Failure Models

• At the project level.
• At the system or device level.
• Common methods include Fishbone analysis or FMEA
• FMEA Failure Modes and Effects Analysis

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Fishbone Chart

• Cause and Effect Analysis
• Create an Ishikawa or Fishbone Chart
• Head is Problem Skeleton are the Causes
• Typical categories, 5Ms E
• Man
• Machine
• Material
• Method
• Measurement
• Environment

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Industrial Monitoring Sensor
Create a Fishbone Chart for Sensor Not Working
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Analysis Tool FMEA

• Failure Mode and Effects Analysis
• FMEA is an enhanced Cause and Effect Analysis.
  (the 5Ms plus E)
• Do Fishbone Chart for Industrial Sensor.
• Apply FMEA to a Design or Processes at many
  levels.
• Systems often have many SPFs single points of
  failure.

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Design Tool FMEA

• The Concept of FMEA
• People Make Mistakes
• Products and Processes Fail
• Anticipate these errors and eliminate them with
  design or process changes !!

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FMEA Example
How many ways can a floppy disk be inserted ??
What design features make this possible??
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FMEA Steps-The traditional approach

1. Team activity
2. Select component, system, process step, etc.
3. Identify possible failure modes.
4. Identify causes of failure modes.
5. Identify effects of failures.
6. Estimate (1-10 ranking)
7. Occurrence how often (1not, 10often)
8. Severity how bad (1not, 10severe)
9. Detection how easy (1easy, 10difficult)
10. Calculate RPN risk priority number

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FMEA RPN example
Rules for OSD Values Threshold for Action
Varies Thresholds 55-100 (?)
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From National Instruments
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From National Instruments
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Detection in Design or Manufacturing
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Many versions of this chart
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Occurrence and Severity

• O and S are often the two critical factors and
  some analysis just looks at these two.

From Dieter
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Industrial Monitoring Sensor
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FMEA Summary

• Combines ideas of Cause and Effect chart,
  mistake proofing, and risk.
• Useful to identify and prioritize possible
  failure modes and fixes.
• Possible Fixes
• High reliability components,
• De-rate components,
• Redundancy,
• Change the design.

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FMEA- A Requirements Approach

• FMEA often starts with
• Identify possible failure modes.
• How? guess, experience, brainstorm, etc.
• Consider
• Requirements are what the system is supposed to
  do.
• Counter-requirements (not being met) are failure
  modes.
• Use counter-requirements to populate the FMEA
  table.

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Design FMEA Example
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Design FMEACoyote Hoist
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Class Discussion Process FMEA

• You are responsible for developing a process to
  stuff several hundred envelopes for a charity
  group.
• Each envelope is to contain three separate flyers
  and a cover sheet with the recipients name on it.
  After folding, the name must show in the cutout
  in the envelope. The final step is to seal and
  place stamps on the envelope for mailing.
• Develop a PFMEA for this process.

Process FMEA
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