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Copyright 2007 ~ Mark Polczynski All Rights Reserved ENMA 282: FMEA - 11 Failure Mode and Effects Analysis Part 1.

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Presentation on theme: "Copyright 2007 ~ Mark Polczynski All Rights Reserved ENMA 282: FMEA - 11 Failure Mode and Effects Analysis Part 1."— Presentation transcript:

1 Copyright 2007 ~ Mark Polczynski All Rights Reserved ENMA 282: FMEA - 11 Failure Mode and Effects Analysis Part 1

2 Copyright 2007 ~ Mark Polczynski All Rights Reserved ENMA 282: FMEA - 12 Two sources used for charts, graphs, etc. in this lecture… 21 Reference Numbers See also: Reliability and Information Center’s FMECA document.FMECA

3 Copyright 2007 ~ Mark Polczynski All Rights Reserved ENMA 282: FMEA - 13 FMEA: Failure Mode and Effect Analysis – What Is It? A systematic method Of analyzing and ranking the risks Associated with various failure modes (existing and potential), Prioritizing them for remedial action, Then acting on the highest ranked items, Re-evaluating all risks, And returning to the prioritization step in a continuous loop Until marginal results set in. 1

4 Copyright 2007 ~ Mark Polczynski All Rights Reserved ENMA 282: FMEA - 14 Action Results Component Description Component Function Failure Mode Failure Mode Effects Severity Ranking Failure Cause Occurrence Ranking Current Controls Detection Ranking Risk Priority Number Recommended Corrective Action Responsibility & Completion Date Action Taken New Severity Ranking New Occurrence Ranking New Detection Ranking New Risk Priority Number FMEA Process The “Standard” FMEA FMEA is a process and a document. Typically consists of two sections: One completed as part of the formal FMEA process, The other recording actions taken and results obtained. 1

5 Copyright 2007 ~ Mark Polczynski All Rights Reserved ENMA 282: FMEA - 15 Why are we studying FMEA? It is a widely-applied “standard” quality process. When properly-applied, has demonstrated good results. Tons of supporting literature, tools, techniques, software, etc. Good way to “teach reliability” – Gateway to a variety of important quality/reliability-related topics. For example…

6 Copyright 2007 ~ Mark Polczynski All Rights Reserved ENMA 282: FMEA - 16 FMEA and Continuous Improvement FMEA can be a major element of a systematic continuous improvement loop – but is worthless without the rest of the loop. FMEA should be part of a comprehensive quality system. Each block should have systematic processes and documentation. FMEA can support this need. Analyze: What’s the problem? Plan: What should we do? Verify: Did it help? Act: Do it! FMEA

7 Copyright 2007 ~ Mark Polczynski All Rights Reserved ENMA 282: FMEA - 17 FMEA: Failure Mode and Effect Analysis – A systematic method Of analyzing and ranking the risks Associated with various failure modes (existing and potential), Prioritizing them for remedial action, Then acting on the highest ranked items, Re-evaluating all risks, And returning to the prioritization step in a continuous loop Until marginal results set in. Standardized process and documentation Need a basis for scoring How do we anticipate? Need a basis for scoring FMEA just sets direction Continuous Improvement process You define

8 Copyright 2007 ~ Mark Polczynski All Rights Reserved ENMA 282: FMEA - 18 FMEA: Standardized Process and Documentation Originated in the US Army in 1949, and became Mi-Std-1629 – Basically ignored until NASA applied FMEA to Apollo space program. Became common in aerospace industry - primary application was for missions where you couldn’t repair failures. Ford began to apply FMEA in By 1988, the “Big Three” US auto makers were using FMEA. In 1994, GM, Ford, and Daimler- Chrysler adopted QS-9000, the automotive version of ISO-9000, which mandates use of FMEA by automotive suppliers. In 1985, the International Electrotechnical Commission adopted IEC The Society of Automotive Engineers (SAE) has created the ARP 5580 FMEA standard, which is applicable for commercial and military systems.

9 Copyright 2007 ~ Mark Polczynski All Rights Reserved ENMA 282: FMEA - 19 Overview of FMEA Types The most common types of FMEA are: DFMEA: Design FMEA, applied primarily during product design, PFMEA: Process FMEA, applied to product manufacturing processes, You may also see reference to:: System FMEA: Sometimes called the Concept FMEA - used early in the concept/design stage. Service FMEA: Applied to services provided for “customers”. Finally, there is the: FMECA: Criticality analysis – extends the basic FMEA focus to include the effects of failures.

10 Copyright 2007 ~ Mark Polczynski All Rights Reserved ENMA 282: FMEA Overview of FMEA Types FMEAs can also be classified as: Functional FMEA: Focuses on functions vs. components, Interface FMEA: Focuses on interconnections between components, Detailed FMEA: Focuses on characteristics of a particular implementation, usually starting at the component level. We will first examine a Detailed DFMEA, the most common type. Here is a simple example of how to construct he DFMEA…

11 Copyright 2007 ~ Mark Polczynski All Rights Reserved ENMA 282: FMEA Step 1: Obtain Bill of Material (BOM) 1 Detailed DFMEA typically starts with a Bill of Materials, which is the source for completing the “Component Description” portion of the DFMEA document.

12 Copyright 2007 ~ Mark Polczynski All Rights Reserved ENMA 282: FMEA Action Results Component Description Component Function Failure Mode Failure Mode Effects Severity Ranking Failure Cause Occurrence Ranking Current Controls Detection Ranking Risk Priority Number Recommended Corrective Action Responsibility & Completion Date Action Taken New Severity Ranking New Occurrence Ranking New Detection Ranking New Risk Priority Number FMEA Process Each line item in the BOM goes here

13 Copyright 2007 ~ Mark Polczynski All Rights Reserved ENMA 282: FMEA Action Results Component Description Component Function Failure Mode Failure Mode Effects Severity Ranking Failure Cause Occurrence Ranking Current Controls Detection Ranking Risk Priority Number Recommended Corrective Action Responsibility & Completion Date Action Taken New Severity Ranking New Occurrence Ranking New Detection Ranking New Risk Priority Number FMEA Process Step 2: Describe what each component does. Components may have multiple functions. Different functions may have different failure modes, so… Enter each function as a different line in the FMEA. Example: Component Description – - Fries Holder Component Functions – - Holds fries - Advertising

14 Copyright 2007 ~ Mark Polczynski All Rights Reserved ENMA 282: FMEA Action Results Component Description Component Function Failure Mode Failure Mode Effects Severity Ranking Failure Cause Occurrence Ranking Current Controls Detection Ranking Risk Priority Number Recommended Corrective Action Responsibility & Completion Date Action Taken New Severity Ranking New Occurrence Ranking New Detection Ranking New Risk Priority Number FMEA Process Step 3: For each function, describe how the component can fail. Functions may have multiple failure modes. Enter each failure mode as a different line in the FMEA. Example: Fries Holder failures – - Holds fries - Holder falls apart - Holder won’t open - Advertising - Printing smeared - Poor color registration

15 Copyright 2007 ~ Mark Polczynski All Rights Reserved ENMA 282: FMEA Action Results Component Description Component Function Failure Mode Failure Mode Effects Severity Ranking Failure Cause Occurrence Ranking Current Controls Detection Ranking Risk Priority Number Recommended Corrective Action Responsibility & Completion Date Action Taken New Severity Ranking New Occurrence Ranking New Detection Ranking New Risk Priority Number FMEA Process Step 4: For each failure mode, describe the effects. Failure modes may have multiple effects. Enter each failure effect as a different line in the FMEA. Example: Failure mode effects – - Holds fries - Holder falls apart - Fries fall out - Bag saturates with grease - Customer car seat stained - Holder won’t open - etc… - Advertising - Printing smeared - Customer can’t read advertising - Poor color registration - etc…

16 Copyright 2007 ~ Mark Polczynski All Rights Reserved ENMA 282: FMEA Note on Failure Mode Effects: Failure mode effects can be - Local Effects: For DFMEA, effects primarily at lowest level of BOM Next Higher Effects: Effects primarily at next level of BOM End Effects: Effects primarily at top of BOM

17 Copyright 2007 ~ Mark Polczynski All Rights Reserved ENMA 282: FMEA Note on Failure Mode Effects: It can be beneficial to note the Failure Mode Effect Level in the FMEA. Thinking in terms of levels can expose additional effects, this produces a more comprehensive FMEA. For the preceding example: Fries Fall Out might be a Local Effect (Level 2), Bag Saturated with Grease might be a Next Higher Effect (Level 1), Customer Car Seat Stained might be an End Effect (Level 0). Note that the bag for holding the burger and fries was missed in this BOM!

18 Copyright 2007 ~ Mark Polczynski All Rights Reserved ENMA 282: FMEA Action Results Component Description Component Function Failure Mode Failure Mode Effects Severity Ranking Failure Cause Occurrence Ranking Current Controls Detection Ranking Risk Priority Number Recommended Corrective Action Responsibility & Completion Date Action Taken New Severity Ranking New Occurrence Ranking New Detection Ranking New Risk Priority Number FMEA Process Step 5: For each failure mode to failure mode effect pair, describe the cause of failure. It is possible to have multiple causes per failure mode. Enter each failure cause as a different line in the FMEA. Example: Failure causes – - Holds fries - Holder falls apart - Fries fall out - Improper gluing - Improper forming of holder - Bag saturated with grease - Fries saturated with grease - Bag absorbs grease - Customer car seat stained - Grease is not water soluble - Seat absorbs grease

19 Copyright 2007 ~ Mark Polczynski All Rights Reserved ENMA 282: FMEA Action Results Component Description Component Function Failure Mode Failure Mode Effects Severity Ranking Failure Cause Occurrence Ranking Current Controls Detection Ranking Risk Priority Number Recommended Corrective Action Responsibility & Completion Date Action Taken New Severity Ranking New Occurrence Ranking New Detection Ranking New Risk Priority Number FMEA Process Step 6: Current Controls are the various means by which the Failure Mode Effect, and/or the Failure Mode Cause is detected. This can be a person, a test, a review plan, etc. There may be multiple or no current controls for various conditions. Example: Current Controls – - Holds fries - Holder falls apart - Fries fall out - Improper gluing - Mfr. glue station operator - Restaurant fryer operator

20 Copyright 2007 ~ Mark Polczynski All Rights Reserved ENMA 282: FMEA Action Results Component Description Component Function Failure Mode Failure Mode Effects Severity Ranking Failure Cause Occurrence Ranking Current Controls Detection Ranking Risk Priority Number Recommended Corrective Action Responsibility & Completion Date Action Taken New Severity Ranking New Occurrence Ranking New Detection Ranking New Risk Priority Number FMEA Process So, where are we at now? We have covered several qualitative items associated with the detailed DFMEA.

21 Copyright 2007 ~ Mark Polczynski All Rights Reserved ENMA 282: FMEA Action Results Component Description Component Function Failure Mode Failure Mode Effects Severity Ranking Failure Cause Occurrence Ranking Current Controls Detection Ranking Risk Priority Number Recommended Corrective Action Responsibility & Completion Date Action Taken New Severity Ranking New Occurrence Ranking New Detection Ranking New Risk Priority Number FMEA Process So, where are we at now? Now we will examine some semi-quantitative elements. They are semi-quantitative because they use numbers, but the numbers are typically subjective intuitive estimates, vs. hard data.

22 Copyright 2007 ~ Mark Polczynski All Rights Reserved ENMA 282: FMEA Semi-Quantitative Elements of the DFMEA: Using the tables on the following slides or their equivalents, assign: Severity Ranking: Rank the severity of each Failure Mode in the FMEA. Occurrence Ranking: Rank the probability of occurrence of each Failure Cause in the FMEA. Detection Ranking: Rank the probability that each Current Control will detect each Failure Mode, Failure Mode Effect and Failure Cause. Risk Priority Number: RPN = Severity x Occurrence x Detection Rankings are all 1-10, so RPN is

23 Copyright 2007 ~ Mark Polczynski All Rights Reserved ENMA 282: FMEA RankDescriptionCriteria 10Highly Hazardous Without warning - Product is unsafe for customer use, or violates government regulation. 9Hazardous With Warning - Product is unsafe for customer use, or violates government regulation. 8Very High Product's primary function fails. 7High Product's primary function is impaired. 6Moderate Product's primary function is unaffected, secondary function fails. 5Low Product's primary function is unaffected, secondary function is impaired. 4Very Low Product is non-conformant, some customer dissatisfaction expected. 3Minor Product is non-conformant, some customer dissatisfaction may occur. 2Very Minor Product is non-conformant, customer dissatisfaction is unlikely. 1None No effect. Rankings for DFMEA Severity (for each Failure Mode) 1

24 Copyright 2007 ~ Mark Polczynski All Rights Reserved ENMA 282: FMEA RankingDescriptionFailure Rate 10Very High: Failure is a Continuous Problem P 20% 9P 10% 8High: Frequent Failures P 5% 7P 2% 6Moderate: Sporadic Failures P 1% 5P 0.2% 4P 0.04% 3Low: Relatively few Failures P % 2P % 1Remote: Failure is unlikelyP % Rankings for FMEA Occurrence (for each Failure Mode) 1

25 Copyright 2007 ~ Mark Polczynski All Rights Reserved ENMA 282: FMEA Rankings for FMEA Detection RankDescriptionCriteria 10Non- Detectable No known Controls available. Failure mode or its Cause is undetectable 9Very RemoteVery Remote Likelihood that Current Controls will detect Failure Mode or its Cause 8RemoteRemote Likelihood that the Current Controls will detect Failure Mode or its Cause 7Very LowVery Low Likelihood that Current Controls will detect Failure Mode or its Cause 6LowLow Likelihood that Current Controls will detect the Failure Mode or its Cause 5ModerateModerate Likelihood that Current Controls will detect the Failure Mode or its Cause 4Moderately High Moderately High Likelihood that current Controls will detect Failure Mode or its Cause 3HighHigh Likelihood that Current Controls will detect Failure Mode or its Cause 2Very HighVery High Likelihood that Current Controls will detect Failure Mode or its Cause 1Highly Detectable The Current Control will almost certainly detect the potential Cause of the Failure or its Failure Mode 1

26 Copyright 2007 ~ Mark Polczynski All Rights Reserved ENMA 282: FMEA Example: Fries holder function – - Holds fries - Holder falls apart - Fries fall out - Improper gluing - Mfr. glue station operator - Restaurant fryer operator - Bag saturated with grease - Fries saturated with grease - etc… - Bag absorbs grease - etc… - Customer car seat stained - Grease is not water soluble - etc… - Seat absorbs grease - etc… - etc… Function Failure Mode Failure Mode Effect Failure Cause Current Control Severity Ranking of Failure Mode Effect: Fries fall out = Very High = 8 Occurrence Ranking of Failure Cause: Improper gluing = Moderate = 5 Detection Ranking of Current Control: Mfr. Glue station operator = High = 3 RPN = 8 x 5 x 3 = 120 Example RPN Calculation:

27 Copyright 2007 ~ Mark Polczynski All Rights Reserved ENMA 282: FMEA Action Results Component Description Component Function Failure Mode Failure Mode Effects Severity Ranking Failure Cause Occurrence Ranking Current Controls Detection Ranking Risk Priority Number Recommended Corrective Action Responsibility & Completion Date Action Taken New Severity Ranking New Occurrence Ranking New Detection Ranking New Risk Priority Number FMEA Process So, where are we at now? We have described Failure Modes, Failure Mode Effects, Failure Causes, and Current Controls. We have assigned values to Severity Ranking, Occurrence Ranking, and Detection Ranking. We have calculated the Risk Priority Number.

28 Copyright 2007 ~ Mark Polczynski All Rights Reserved ENMA 282: FMEA Action Results Component Description Component Function Failure Mode Failure Mode Effects Severity Ranking Failure Cause Occurrence Ranking Current Controls Detection Ranking Risk Priority Number Recommended Corrective Action Responsibility & Completion Date Action Taken New Severity Ranking New Occurrence Ranking New Detection Ranking New Risk Priority Number FMEA Process So, where are we at now? The next logical step is to define Recommended Actions and assign Responsibilities and Completion Dates. But there are now a large number of line items in the FMEA. So we use the RPNs to prioritize the list, and just focus on the most critical issues. Then apply Continuous Improvement.

29 Copyright 2007 ~ Mark Polczynski All Rights Reserved ENMA 282: FMEA Selecting Items for Corrective Action Given a ranked list of items, the most common way to select the most important items is to perform a Pareto Analysis: For a set of cause and effect relationships, 80% of the effects are due to 20% of the causes. This is an observation that appears to apply to a large range of applications. But it is not really a Law of Nature (like e = mc 2 ). There are two ways to apply this approach…

30 Copyright 2007 ~ Mark Polczynski All Rights Reserved ENMA 282: FMEA Method 1: Apply rule to number of items 0.2 x 15 = 3 Method 2: Apply rule to the ranking Items above 80%

31 Copyright 2007 ~ Mark Polczynski All Rights Reserved ENMA 282: FMEA Another Way to Prioritize: According to some reliability gurus, the “detection” part of the RPN calculation is immaterial. If you focus on severity and occurrence, you tend to “build quality in”, whereas including detectiion tends to “inspect quality in”. So for this approach, you might use a Risk Level Chart – Which graphically shows the highest risk elements.

32 Copyright 2007 ~ Mark Polczynski All Rights Reserved ENMA 282: FMEA What’s the Problem with FMEAs? As multiple functions, failure modes, failure effects, failure causes, and current controls for each component branch out, it is clear that an FMEA can rapidly spiral out of control. Nevertheless, each branch must be followed to its logical end if the FMEA is to serve its purpose. The SAE ARP 5580 recommends a solution to this. You can group together line items that exhibit identical Failure Mode Effects. This allows you to rationally address the myriad problems and actions indicated by the FMEA. In other words…

33 Copyright 2007 ~ Mark Polczynski All Rights Reserved ENMA 282: FMEA Example: Failure mode effects – - Holds fries - Holder falls apart - Fries fall out - Bag saturated with grease - Customer car seat stained - Holder won’t open - … - Advertising - Printing smeared - Customer can’t read advertising - Poor color registration - Customer can’t read advertising After the FMEA document is complete, do a sort on: “Failure Mode Effects” This groups all the “Customer can’t read advertising” together, And “Fries fall out” together, etc… This aids in creating rational problem solving plans. Other approach might be to sort by Failure Cause or Failure Mode. To facilitate this sorting and grouping approach, people have created pre-defined vocabularies describing failure modes, effects, and causes, i.e., “Customer”, not “Customers”.

34 Copyright 2007 ~ Mark Polczynski All Rights Reserved ENMA 282: FMEA What’s Another Problem with FMEAs? The process of clearly, concisely, and exhaustively identifying all functions, failure modes, failure mode effects, failure causes, and current controls can be quite difficult. Especially if you start this process in the early phases of design (which you should), before this type of information is more readily available. Relying on unstructured brainstorming to come up with this information is, in itself, not a highly-reliable process. Later, we will discuss some structured, systematic tools, techniques, and processes to aid in performing these tasks.

35 Copyright 2007 ~ Mark Polczynski All Rights Reserved ENMA 282: FMEA Action Results Component Description Component Function Failure Mode Failure Mode Effects Severity Ranking Failure Cause Occurrence Ranking Current Controls Detection Ranking Risk Priority Number Recommended Corrective Action Responsibility & Completion Date Action Taken New Severity Ranking New Occurrence Ranking New Detection Ranking New Risk Priority Number FMEA Process So, where are we at now? Having selected items for corrective action, Results of actions are recorded, And new RPNs are calculated. Then, Pareto Analysis is performed again, and new Corrective Actions are identified. Analyze: What’s the problem? Plan: What should we do? Verify: Did it help? Act: Do it!

36 Copyright 2007 ~ Mark Polczynski All Rights Reserved ENMA 282: FMEA In the Reliability literature, you can find generic lists of Corrective Actions for different application areas… 2

37 Copyright 2007 ~ Mark Polczynski All Rights Reserved ENMA 282: FMEA Summary of DFMEA Steps: 1.Obtain Component descriptions from bill of materials. 2.Component Function: Describe all functions of each component. 3.Describe how each component can fail to perform each function (failure mode). 4.Describe all effects of each failure mode. 5.For each failure mode/effect pair, describe all causes. 6.For each failure mode effect and/or cause, describe the current means of detecting the condition. 7.Assign ranking numbers to Severity/Occurrence/Detection, and calculate RPN. 8.Prioritize conditions. Sort by Failure Mode Effects, Failure Cause or Failure Mode as needed to clarify major failure areas. 9.Determine Recommended Corrective Action. 10.Assign Responsibility and Completion Date. 11.Review Actions Taken. 12.Re-Assess Severity/Occurrence/ Detection rankings and re-calculate RPN 13.Repeat as needed.

38 Copyright 2007 ~ Mark Polczynski All Rights Reserved ENMA 282: FMEA FMEA: Failure Mode and Effect Analysis – A systematic method Of analyzing and ranking the risks Associated with various failure modes (existing and potential), Prioritizing them for remedial action, Then acting on the highest ranked items, Re-evaluating all risks, And returning to the prioritization step in a continuous loop Until marginal results set in. Standardized process and documentation Need a basis for scoring How do we anticipate? Need a basis for scoring FMEA just sets direction Continuous Improvement process You define

39 Copyright 2007 ~ Mark Polczynski All Rights Reserved ENMA 282: FMEA What Next?! So, that’s the basic detailed DFMEA In the next lecture on FMEA, we will talk about some modifications to this basic approach. Here’s one final note on FMEA..

40 Copyright 2007 ~ Mark Polczynski All Rights Reserved ENMA 282: FMEA Semi-Quantitative Elements of the DFMEA: Using the tables on the following slides or their equivalents, assign: Severity Ranking: Rank the severity of each Failure Mode in the FMEA. Occurrence Ranking: Rank the probability of occurrence of each Failure Cause in the FMEA. Detection Ranking: Rank the probability that each Current Control will detect each Failure Mode, Failure Mode Effect and Failure Cause. Risk Priority Number: RPN = Severity x Occurrence x Detection We needed to assign numerical values to calculate RPN, but aren’t these numbers pretty poorly defined?

41 Copyright 2007 ~ Mark Polczynski All Rights Reserved ENMA 282: FMEA FMEA: Failure Mode and Effect Analysis – A systematic method Of analyzing and ranking the risks Associated with various failure modes (existing and potential), Prioritizing them for remedial action, Then acting on the highest ranked items, Re-evaluating all risks, And returning to the prioritization step in a continuous loop Until marginal results set in. Well, note that initially, these numbers are all relative… …since they just serve to identify the most risky elements which you will address first.

42 Copyright 2007 ~ Mark Polczynski All Rights Reserved ENMA 282: FMEA FMEA: Failure Mode and Effect Analysis – A systematic method Of analyzing and ranking the risks Associated with various failure modes (existing and potential), Prioritizing them for remedial action, Then acting on the highest ranked items, Re-evaluating all risks, And returning to the prioritization step in a continuous loop Until marginal results set in. The difficulty comes later when you need to know when to stop making improvements. Hopefully, by that time you will have more confidence in your quantitative assessments.


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