Design fmea
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This document provides guidance on conducting a Design Failure Mode and Effects Analysis (DFMEA). It begins with defining the purpose of a FMEA and what it involves. It then discusses current DFMEA practices and concerns. The remainder of the document offers detailed instructions on performing a DFMEA, including how to construct a process flow diagram, interface matrix, evaluate potential failure modes and their effects/severity, occurrence, detection, and risk priority numbers. It provides examples and criteria for properly analyzing risk and prioritizing corrective actions. The overall summary is that the document aims to refine the approach to DFMEAs by outlining the full process and key considerations for effectively conducting a thorough design risk assessment.
Design fmea
- 1. DFMEA
- 2. Purpose To deepen understanding and refine your current approach to Design FMEA’s.
- 3. Definition of FMEA A Failure Mode and Effect Analysis uses a disciplined technique to identify and help eliminate product and process potential failure modes. o By ID of potential failures o Assessing the risks caused by failure modes and Identify corrective actions o Prioritizing corrective actions o Carry out corrective actions
- 7. 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
- 8. Potential Key Product Characteristics Development DetectPrevent R P N D E T O C C S E V Action Taken Action Results Response & Target Complete Date Recommended Actions R P N D e t e c Current Controls O c c u r Potential Cause(s)/ Mechanism(s) Of Failure C l a s s S e v Potential Effect(s) of Failure Potential Failure Mode Item / Process Step DetectPrevent R P N D E T O C C S E V Action Taken Action Results Response & Target Complete Date Recommended Actions R P N D e t e c Current Design Controls O c c u r Potential Cause(s)/ Mechanism(s) Of Failure C l a s s S e v Potential Effect(s) of Failure Potential Failure Mode Item / Process Step Function DFMEA Requirements Documents ! •Regulatory •Dimensional •Cosmetic ! Req. Spec. Document Drawings Warranty History Robustness Tools ! Boundary Diagram P-Diagram Interface Matrix 10 9 8 7 6 5 4 3 2 1 1 2 3 4 5 6 7 8 9 10 S E V E R I T Y O C C U R R E N C E POTENTIAL CRITICAL CHARACTERISTICS Safety/Regulatory POTENTIAL SIGNIFICANT CHARACTERISTICS Customer Dissatisfaction Special Characteristics Matrix ANOYANCE ZONE ALL OTHER CHARACTERISTICS Appropriate actions / controls already in place Cascade Technical Requirements Into Special Product Characteristics
- 10. Pencil Assembly
- 11. Block-Diagram
- 12. Step 2 P-diagram
- 13. Step 2 P-diagram
- 14. P-Diagram (Parameter diagram) Example of a P-DIAGRAM
- 15. Interface matrix
- 16. Interface matrix
- 24. Severity Column DetectPrevent R P N D E T O C C S E V Action Taken Action Results Response & Traget Complete Date Recommended Actions R P N D e t e c Current Process Controls O c c u r Potential Cause(s)/ Mechanism(s) Of Failure C l a s s S e v Potential Effect(s) of Failure Potential Failure Mode Item / Process Step DetectPrevent R P N D E T O C C S E V Action Taken Action Results Response & Traget Complete Date Recommended Actions R P N D e t e c Current Process Controls O c c u r Potential Cause(s)/ Mechanism(s) Of Failure C l a s s S e v Potential Effect(s) of Failure Potential Failure Mode Item / Process Step Function Severity Column
- 25. AUTOMOTIVE EXAMPLE SEVERITY EVALUATION CRITERIA Hazardous- with warning Very High High Very high severity ranking when a potential failure mode affects safe vehicle operation and/or involves noncompliance with government regulation without warning Low Very Low Minor Very Minor None Very high severity ranking when a potential failure mode affects safe vehicle operation and/or involves noncompliance with government regulation with warning Vehicle/item inoperable (loss of primary function). Vehicle/item operable but at a reduced level of performance. Customer very dissatisfied. Vehicle/item operable but Comfort/Convenience item(s) inoperable. Customer dissatisfied. Vehicle/item operable but Comfort/Convenience item(s) operable at a reduced level of performance. Customer somewhat dissatisfied. Fit & Finish/Squeak & Rattle item does not conform. Defect noticed by most customers (greater than 75%). Fit & Finish/Squeak & Rattle item does not conform. Defect noticed by 50% of customers. Fit & Finish/Squeak & Rattle item does not conform. Defect noticed by discriminating customers (less than 25%). No discernable effect. 10 8 7 6 3 2 1 Hazardous- without warning Moderate 4 5 EFFECT CRITERIA: Severity of Effect RNK. SEVERITY EVALUATION CRITERIA 9
- 26. FMEA General ● For High Severity 9/10
- 29. Occurrence Column DetectPrevent R P N D E T O C C S E V Action Taken Action Results Response & Traget Complete Date Recommended Actions R P N D e t e c Current Process Controls O c c u r Potential Cause(s)/ Mechanism(s) Of Failure C l a s s S e v Potential Effect(s) of Failure Potential Failure Mode Item / Process Step DetectPrevent R P N D E T O C C S E V Action Taken Action Results Response & Traget Complete Date Recommended Actions R P N D e t e c Current Process Controls O c c u r Potential Cause(s)/ Mechanism(s) Of Failure C l a s s S e v Potential Effect(s) of Failure Potential Failure Mode Item / Process Step Function Occurrence Column
- 30. Occurrence Evaluation Criteria *Note: Zero (0) rankings for Severity, Occurrence or Detection are not allowed 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
- 31. Example of Significant/ Critical Threshold *Used by permission of Ford Motor Company 10 9 8 7 6 5 4 3 2 1 1 2 3 4 5 6 7 8 9 10 S E V E R I T Y O C C U R R E N C E POTENTIAL CRITICAL CHARACTERISTICS Safety/Regulatory POTENTIAL SIGNIFICANT CHARACTERISTICS Customer Dissatisfaction ALL OTHER CHARACTERISTICS Appropriate actions / controls already in place Special Characteristics Matrix ANOYANCE ZONE
- 32. Design Verification (Current Design Controls) ▪ Think of Design Control in two ways; Prevention and Detection. List them separately. ▪ To save time, add any new (untried) prevention/ detection ideas to the document under Recommended Actions column. o Prevention is specifically related to reduction or elimination of a cause. o Detection is how well the test or series of tests may find the design flaw – Causes – Failure Mode
- 35. Detection Rating Absolute Uncertainty Very Remote Remote Very Low Low Moderate Moderately High High Very High Almost Certain 10 9 8 7 6 5 4 3 2 1 Design Control will not and/or cannot detect a potential cause/ mechanism and subsequent failure mode; or there is no Design Control. Very Remote chance the Design Control will detect a potential cause/ mechanism and subsequent failure mode. Remote chance the Design Control will detect a potential cause/ mechanism and subsequent failure mode. Very Low chance the Design Control will detect a potential cause/mechanism and subsequent failure mode. Low chance the Design Control will detect a potential cause/mechanism and subsequent failure mode. Moderate chance the Design Control will detect a potential cause/ mechanism and subsequent failure mode. Moderately High chance the Design Control will detect a potential cause/ mechanism and subsequent failure mode. Very High chance the Design Control will detect a potential cause/ mechanism and subsequent failure mode. High chance the Design Control will detect a potential cause/ mechanism and subsequent failure mode. Design Controls will almost certainly detect a potential cause/ mechanism and subsequent failure mode. DETECTION SUGGESTED DETECTION EVALATION CRITERIA CRITERIA RNK.
- 36. Analysis Of Risk ▪ RPN / RISK PRIORITY NUMBER ▪ What Is Risk? ▪ Probability of danger ▪ Severity/Occurrence/Cause
- 37. 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?
- 38. 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.
- 39. Example of Significant/ Critical Threshold *Used by permission of Ford Motor Company 10 9 8 7 6 5 4 3 2 1 1 2 3 4 5 6 7 8 9 10 S E V E R I T Y O C C U R R E N C E POTENTIAL CRITICAL CHARACTERISTICS Safety/Regulatory POTENTIAL SIGNIFICANT CHARACTERISTICS Customer Dissatisfaction ALL OTHER CHARACTERISTICS Appropriate actions / controls already in place Special Characteristics Matrix ANOYANCE ZONE
- 40. Actions Item Function System Subsystem Component: Model Year/Vehicle (s): Core Team: Your Company Name Here Potential Failure Mode and Effects Analysis (Design FMEA) Design Responsibility: Key Date: FMEA Number: Page of Prepared by: FMEA Date (Orig.): (Rev.): Potential Failure Mode Potential Effect (s) of Failure s e v c l a s s Potential Cause (s)/ Mechanism (s) Failure o c c u r Current Design Controls D e t e c R. P. N. Recommended Action(s) Responsibility & Target Completion Date Actions Taken s e v o c c D e t R. P. N. A c t i o n R e s u l t s
- 41. Actions EXAMPLE: Project: Date Of Meeting: Issue Number Issue Status/ Open Date Issue Champion Action Number Action Date Action Person Resp. Team Completion Date 143
- 42. Re-rating RPN After Actions Have Occurred Item Function System Subsystem Component: Model Year/Vehicle (s): Core Team: Your Company Name Here Potential Failure Mode and Effects Analysis (Design FMEA) Design Responsibility: Key Date: FMEA Number: Page of Prepared by: FMEA Date (Orig.): (Rev.): Potential Failure Mode Potential Effect (s) of Failure S e v C l a s s Potential Cause (s)/ Mechanism (s) Failure O c c u r Current Design Controls D e t e c R. P. N. Recommended Action(s) Responsibility & Target Completion Date Actions Taken S e v O c c D e t R. P. N. A c t i o n R e s u l t s
- 43. 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
- 44. FMEA in a continuous flow process ●Steel Making example: ! ▪ Design FMEA was performed on a Crankshaft to determine the best material for the product being considered. This was a critical application. ! ▪ Key features such as Geometry, Strength, Duty Cycle, were described to the Steel producer.