FMEA Failure Mode Effects Analysis. ASQ/APICS Joint Meeting May 10, 2017

Transcription

1 FMEA Failure Mode Effects Analysis ASQ/APICS Joint Meeting May 10, 2017

2 FMEA (Failure Mode and Effects Analysis) Failure Mode and Effects Analysis Agenda What is it? Motivation FMEA Methods Examples

3 What is an FMEA? Description: Failure modes and effects analysis (FMEA) is a step-by-step approach for identifying all possible failures in a design, a manufacturing or assembly process, or a final product or service. Acronyms FMEA: Failure Modes and Effects Analysis PFMEA: Production DFMEA: Design FMECA: Failure Modes and Effects and Criticality Analysis

4 Failures, Failure Modes, Effects Analysis Failure modes means the ways, or modes, in which something might fail. Failures are any errors or defects, especially ones that affect the customer, and can be potential or actual. Effects analysis refers to studying the consequences, or effects, of those failures.

5 FMEA is a Tool FMEA is a tool that allows you to: Prevent System, Product, and Process problems before they occur Reduce costs by identifying process improvement early in the development cycle Create more robust processes Prioritize actions that reduce risk of failure Evaluate the system, design, and processes from a new vantage point.

6 A Systematic Process FMEA provides a systematic process to: Identify and evaluate potential failure modes potential causes of the failure mode Identify and quantify the impact of potential failures Identify and prioritize actions to reduce or eliminate the potential failure Implement action plan based on assigned responsibilities and completion dates Document the associated activities

7 Motivation for Conducting a FMEA Improves design by discovering unanticipated failures Highlights the impact of the failures Potentially helpful during legal actions Provides a method to characterize product safety Often required (e.g. FDA and DOD procurement) Provide risk assessments required by ISO 9001:2015

8 Types of FMEA

9 When to Use an FMEA When a process, product, or service is being designed or redesigned, after QFD and before the design is finalized, or... When an existing process, product, or service is being applied in a new way, or... Before developing control plans for a new or modified process, or... When improvement goals are planned for an existing process, product, or service, or... When analyzing failures of an existing process, product, or service And periodically throughout the life of the process, product, or service

10 Method to Conduct an FMEA (taken from ASM Handbook Vol. 11) Identify all components or systems at given level of the design hierarchy. List the function of each identified component or system. Identify failure modes for each component/system. Typically there will be several ways in which a component can fail. Determine the effect (both locally and globally) on the system.

11 Method to Conduct an FMEA (taken from ASM Handbook Vol. 11) Classify the failure by its effects on the system operation. Determine the failure s probability of occurrence. Identify how the failure mode can be detected (may point out what needs to be inspected on a regular basis). Identify any compensating provisions or design changes to mitigate the failure effects.

12 DESIGN FMEA (DFMEA) The Design FMEA is used to analyze products before they are released to production. It focuses on potential failure modes of products caused by design deficiencies. Design FMEAs are normally done at three levels system, subsystem, and component levels This type of FMEA is used to analyze hardware, functions or a combination

13 PROCESS FMEA (PFMEA) The Process FMEA is normally used to analyze manufacturing and assembly processes at the system, subsystem or component levels. This type of FMEA focuses on potential failure modes of the process that are caused by manufacturing or assembly process deficiencies.

14 Conducting an FMEA Assemble a cross-functional team with diverse knowledge of the process, product, service, and customer needs Identify the scope of the FMEA Identify the functions of your scope by asking what is the purpose of the system of this product or design? What does our customer expect item to do Complete FMEA for following the 10 steps on next slides

15 10 steps to creating a FMEA 1. List the key process steps in the first column. These may come from the highest ranked items of your C&E matrix. 2. List the potential failure mode for each process step. In other words, figure out how this process step or input could go wrong. 3. List the effects of this failure mode. If the failure mode occurs what does this mean to us and our customer in short what is the effect? 4. Rate how severe this effect is with 1 being not severe at all and 10 being extremely severe. Ensure the team understands and agrees to the scale before you start. Also, make this ranking system your own and don t bother trying to copy it out of a book. 5. Identify the causes of the failure mode/effect and rank it as you did the effects in the occurrence column. This time, as the name implies, we are scoring how likely this cause will occur. So, 1 means it is highly unlikely to ever occur and 10 means we expect it to happen all the time.

16 10 steps to creating a FMEA 6. Identify the controls in place to detect the issue and rank its effectiveness in the detection column. Here a score of 1 would mean we have excellent controls and 10 would mean we have no controls or extremely weak controls. If a SOP is noted here (a weak control in my opinion) you should note the SOP number. 7. Multiply the severity, occurrence, and detection numbers and store this value in the RPN (risk priority number) column. This is the key number that will be used to identify where the team should focus first. If, for example, we had a severity of 10 (very severe), occurrence of 10 (happens all the time), and detection of 10 (cannot detect it) our RPN is This means all hands on deck we have a serious issue! 8. Sort by RPN number and identify most critical issues. The team must decide where to focus first. 9. Assign specific actions with responsible persons. Also, be sure to include the date for when this action is expected to be complete. 10. Once actions have been completed, re-score the occurrence and detection. In most cases we will not change the severity score unless the customer decides this is not an important issue.

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18 What to Do Function comes from Functional Analysis, Functional Decomposition Potential Failure Mode comes from things that have gone wrong in the past, concerns of designers, and brainstorming. Possible considerations are partial function, intermittent function, excess function. Potential Effects are consequences to the design, the user, and the environment. Safety and regulation noncompliance are critical issues.

19 Stove Top Example

20 What to Do Potential Causes of failure should be engineering related such as incorrect material, corrosion, wear and human related such as inexperience, misuse, etc. Current Design Controls are things like inspections, testing, poke yoke, and other design checks that are intended to prevent the problem.

21 Partial Example

22 Partial Example (Cont.)

23 What to Do Assign values to Severity, Occurrence, and Detection using the tables on the next three slides. Determine the Risk Priority Number (Severity* Occurrence * Detection) Develop an action plan Implement an action plan

24 Risk Guidelines Effect Rank Criteria None 1 No effect Very Slight 2 Negligible effect on Performance. Some users may notice. Slight 3 Slight effect on performance. Non vital faults will be noticed by many users Minor 4 Minor effect on performance. User is slightly dissatisfied. Moderate 5 Reduced performance with gradual performance degradation. User dissatisfied. Severe 6 Degraded performance, but safe and usable. User dissatisfied. High Severity 7 Very poor performance. Very dissatisfied user. Very High Severity 8 Inoperable but safe. Extreme Severity 9 Probable failure with hazardous effects. Compliance with regulation is unlikely. Maximum Severity 10 Unpredictable failure with hazardous effects almost certain. Noncompliant with regulations.

25 Occurrence Ranking Occurrence Rank Criteria Extremely Unlikely 1 Less than 0.01 per thousand Remote Likelihood per thousand rate of occurrence Very Low Likelihood per thousand rate of occurrence Low Likelihood 4 1 per thousand rate of occurrence Moderately Low Likelihood 5 2 per thousand rate of occurrence Medium Likelihood 6 5 per thousand rate of occurrence Moderately High Likelihood 7 10 per thousand rate of occurrence Very High Severity 8 20 per thousand rate of occurrence Extreme Severity 9 50 per thousand rate of occurrence Maximum Severity per thousand rate of occurrence

26 Detection Ranking Detection Rank Criteria Extremely Likely 1 Can be corrected prior to prototype/ Controls will almost certainly detect Very High Likelihood 2 Can be corrected prior to design release/very High probability of detection High Likelihood 3 Likely to be corrected/high probability of detection Moderately High Likelihood 4 Design controls are moderately effective Medium Likelihood 5 Design controls have an even chance of working Moderately Low Likelihood 6 Design controls may miss the problem Low Likelihood 7 Design controls are likely to miss the problem Very Low Likelihood 8 Design controls have a poor chance of detection Remote Likelihood 9 Unproven, unreliable design/poor chance for detection Extremely Unlikely 10 No design technique available/controls will not detect

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28 RPN Numbers Neither RPN nor criticality are foolproof methods for determining highest risk and priority for action. Severity, occurrence, and detection are not equally weighted; their scales are not linear; and the mathematics hides some surprises. For example, each of the three scales can have values from 1 to 10, so RPN can range from 1 to 1000 yet there are only 120 possible RPN values. Use RPN and criticality as guides, but also rely on your judgment. Effects with very high severity and any chance of occurrence must be addressed!

29 Taking Actions transforms the FMEA from a paper chase into a valuable tool. taking action, especially to reduce severity and occurrence ratings, you can prevent problems, reduce design and development, and start-up time and cost; improve customer satisfaction; and gain competitive advantage.

30 Related Tools for FMEA Tables, matrices, and checklists Brainstorming, affinity diagrams, and other idea creation tools Flowcharts and other process analysis tools All the cause analysis tools, especially fault tree analysis, Pareto charts, why why, and is is not Control charts, design of experiments Graphs, histograms, scatter diagrams, statistical analysis, and other data collection and analysis tools

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