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Process fmea breakfast


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Breakfast session introducing FMEA

Published in: Business

Process fmea breakfast

  1. 1. Failure Mode and Effects Analysis Lawrence Hallett!
  2. 2. Origin Failure mode and effect analysis (FMEA) was one of the first systematic techniques for failure analysis. It was developed by reliability engineers in the 1950s to study problems that might arise from malfunctions of military systems
  3. 3. Most COMMON Types of FMEA's Design (Potential) Failure Modes and Effects Analysis-DFMEA • Focus is on potential design- related failures and their causes. ! Process (Potential) Failures Modes and Effects Analysis-PFMEA • Focuses is on potential process failures and their causes.
  4. 4. PFMEA's ! ● Focus is on potential process –related failures and their causes. ▪Main drive is to understand the process through the identification of as many potential failures as possible. o e.g. Incorrect material used ● PFMEA typically assumes that the design is sound. ● Development of Recommended Actions is targeted at eliminating the Root Cause of the potential failures.
  5. 5. PFMEA's benefits •Identifies Process Functions and Req’s! •Identifies potential failure modes! •Assesses effect of failure! •Identifies causes of failures! •Identifies process controls! •Identifies confirmed Critical Characteristics! •Provides an objective base for action
  6. 6. PFMEA's - who prepares it •A team effort - including! •Manufacturing/production! •Engineering! •Design ! •Quality! •Test! ! •However it is a moving feast
  7. 7. PFMEA Three Parts: ● Process Flow Diagram (PFD) ● Process Failure Mode and Effects Analysis (PFMEA) ● Process Control Plan (PCP)
  8. 8. DFMEA/PFMEA Information Interrelationships DFMEA Design FMEA Process Flow Diagram PFMEA Process FMEA Boundary (Block) Diagram, P- Diagram, Etc. Design Verification Plan & Report (DVP&R) Process Control Plan
  9. 9. Pencil Assembly Using a simple mechanical pencil -conduct a Process FMEA
  10. 10. Process Function/Requirements
  11. 11. Process Flow Diagrams ● The Process Flow Diagram provides a logical (visual) depiction of the process that is being analyzed.
  12. 12. PFD Example
  13. 13. PFD Feeds PFMEA
 Identify the Function(s) ● Function is a description of what the Process does to meet the requirements ➢Related to process specification and product characteristics ➢Comes from the PFD operation description column ● Functions can be described as: ➢Do this operation… ➢To this part or material… ➢With this tooling or equipment…
  14. 14. Potential Failure Mode
  15. 15. Potential Failure Modes Often missed
  16. 16. Potential Effect of Failure
  17. 17. Example Failure Modes Effect of Failure Case assembled but not to the correct height Fails height check causing rework(3) if not detected Connector corrosion leading to intermittence premature part failure(8)
  18. 18. Potential Effects of Failure
  19. 19. Severity Ranking
  20. 20. Severity
  21. 21. Potential Cause of Failure
  22. 22. Cause of Failure
  23. 23. Developing Causes Always assume a direct correlation between cause and failure i.e if the cause occurs then the failure mode occurs
  24. 24. Occurrence
  25. 25. Occurrence Evaluation Criteria Probability of Likely Failure Rates Over Design Life Ranking Failure SUGGESTED OCCURRENCE EVALUATION CRITERIA Very High: Persistent failures High: Frequent failures Moderate: Occasional failures Low: Relatively few failures Remote: Failure is unlikely ≥ 100 per thousand vehicles/items 50 per thousand vehicles/items 20 per thousand vehicles/items 10 per thousand vehicles/items 5 per thousand vehicles/items 2 per thousand vehicles/items 1 per thousand vehicles/items 0.5 per thousand vehicles/items 0.1 per thousand vehicles/items ≤ 0.01 per thousand vehicles/items 10 9 8 7 6 5 4 3 2 1
  26. 26. Current controls
  27. 27. Current Controls 2 types of controls Prevention Prevent the Cause/mechanism or failure mode/effect from occurring or reduce their rate of occurrence ! Detection Detect the cause/mechanism and lead to corrective action
  28. 28. How to identify process controls
  29. 29. Current Controls
  30. 30. Detection ranking
  31. 31. Detection Rankings
  32. 32. Risk Priority Number
  33. 33. Analysis Of Risk ▪ RPN / RISK PRIORITY NUMBER ▪ What Is Risk? ▪ Probability of danger ▪ Severity/Occurrence/Cause
  34. 34. Evaluation by RPN Only ▪ Case 1 o S=5 O=5 D=2 RPN = 50 ▪ Case 2 o S=3 O=3 D=6 RPN = 54 ▪ Case 3 o S=2 O=10, D=10 = 200 ▪ Case 4 o S=9 O=2 D=3 = 54 WHICH ONE IS WORSE?
  35. 35. Example ▪ Extreme Safety/Regulatory Risk o =9 & 10 Severity ▪ High Risk to Customer Satisfaction o Sev. > or = to 5 and Occ > or = 4 ▪ Consider Detection only as a measure of Test Capability.
  36. 36. Actions taken
  37. 37. Actions
  38. 38. Re-rating RPN After Actions Have Occurred
  39. 39. Re-rating RPN After Actions Have Occurred ▪ Severity typically stays the same. ▪ Occurrence is the primary item to reduce / focus on. ▪ Detection is reduced only as a last resort. ▪ Do not plan to REDUCE RPN with detection actions!!! o 100% inspection is only 80% effective! o Reducing RPN with detection does not eliminate failure mode, or reduce probability of causes o Detection of 10 is not bad if occurrence is 1
  40. 40. Outputs