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Failure Mode and Effects Analysis
FMEA Fundamentals
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Objective Understand FMEA is a risk assessment tool
Present an overview of FMEA Review history of the tool Introduce terms, structure, types of FMEA’s Present a road map for construction To get a little practice with this tool.
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Failure Modes Effects Analysis is …
A systematic approach used to examine potential failures and prevent their occurrence. The analysis generates a relative risk ranking to each failure mode.
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History of FMEA Developed in the 60’s by NASA to identify single point failures on the Apollo project. SPF = any single piece of equipment that, if it fails, can bring your entire operation to a halt. (managed with redundancy) US Navy adopted it in the 70’s for weapons programs. In the 80’s, the automotive industry implemented FMEA and required its suppliers to do the same.
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Overview Applied during the early stages of product, process, or design. FMEA begins by defining the functions a part or process is supposed to perform. (Flowchart) Brainstorming is used to identify failure modes This process helps predict problems and provides a method to rank most likely failure modes.
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Potential Effect of failure
The Simple Form Process Step Failure mode Potential Effect of failure Sev Potential cause Occ Current control Det RPN Recommended action
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FMEA Terms Failure Mode Any way in which a process could fail to perform a required function or fail to meet a measurable expectation Effect Consequence of a failure. Ranked by severity. Severity The level of seriousness of the effect of a failure. A “10” represents most severe. A “1” represents least severe.
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FMEA Terms Cause Source of a failure mode; means by which a particular element of the process results in a failure mode. Ranked by probability of occurrence. Occurrence The likelihood that a particular cause will happen and result in that particular failure. A “10” is near certainty. A “1” is a remote chance of occurrence.
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Current Controls All means of detecting the cause or the failure mode before it reaches the customer. Detection Our ability to detect a failure. A “10” implies the current control will not detect a failure. A “1” suggests detection is nearly certain.
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FMEA Terms Risk Priority Number Results from the multiplication of the three rankings. (SxOxD) Ranges from 1 to Failure modes with high RPN’s indicate a high risk of failure. Recommended Actions Those corrective actions identified and implemented to reduce the most serious risks.
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FMEA Process Inputs Outputs Drawing and specifications
Other customer requirements Process technical procedures Warranty or nonconformance history History or hysteria Outputs Risk Priority Number (RPN) = severity x occurrence x detection List of actions to prevent causes or to detect failures History of actions taken and future activity
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Types of FMEA’s Design Process Equipment
Performed on design criteria focusing on how each requirement can fail. Goal is to maximize design quality, reliability, cost and maintainability Process Performed on each step of a process and how it can fail. Equipment A special PFMEA focusing on equipment failure
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FMEA can … Objective evaluation of readiness
Helps manufacturing in process and test development Documents risks Assess resources, tooling, and maintenance
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Recommended Actions Corrective action should focus on those highest concerns as ranked by the RPN. The intent is to reduce the occurrence, severity and/or detection rankings Improving detection control is typically expensive. Emphasis should be placed on preventing, rather than detecting, defects.
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FMEA is appropriate when …
New products or processes are being designed Existing designs and processes are being changed Existing designs or processes will be used in new applications or environments Completing a root cause analysis or improvement project, to prevent recurrence of the problem Update an FMEA - as information changes, as high priority failure modes are addressed
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FMEA fails, when … One person is assigned to do the FMEA alone.
The SOD (rating scales) are not customized so that they are meaningful to your company. The design or process expert is either not included on the FMEA team or is allowed to dominate the FMEA team. Members of the FMEA team have not been trained and become frustrated with the process. The FMEA team gets bogged down with the minute details . Rushing through the generation of potential failure modes in a hurry to move on to the next step of the FMEA, possibly overlooking significant but obscure failure modes. Listing practically the same effect for every failure mode Stopping once the RPNs are calculated Not reevaluating when new failures occur.
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Severity Criteria
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Occurrence Criteria
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Detection Criteria
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FMEA Practice Let’s make a cup of coffee Customer wants: Watch for:
French press Medium roast (mild but not overly bitter) 12 ounces … now Watch for: Multiple effects for one failure mode Multiple failure modes with a common effect Multiple causes of a failure mode
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Potential Effect of failure
French Press Coffee Process Step Failure mode Potential Effect of failure Sev Potential cause Occ Current control Det RPN Recommended action Obtain beans Grind beans obtain water boil water Steap grounds Filter mother liquor
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Practice Break into groups Handouts Discuss Questions?
SOD rating charts A4 with FORM Discuss Questions?
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Roadmap Identify the cross-functional team
Define customer needs and expectations Review the process or design, list functions Brainstorm potential failure modes Analyze potential failure modes (severity of effect, occurrence of causes, ability to control detection) Calculate RPN’s (risk priority numbers) Identify actions to reduce high RPN’s Execute on actions Recalculate RPN’s and update FMEA
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Process Failure Causes
Poor control procedures Improper equipment maintenance Bad recipe Fatigue Lack of safety Hardware failure Failure to enforce controls Environment Stress connections Poor FMEA’s Omitted processing Processing errors Errors setting up work pieces Missing parts Wrong parts Processing wrong work piece Mis-operation Adjustment error Equipment not set up properly Tools or fixtures improperly prepared
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Questions to Help Identify Causes
Can any equipment failures contribute to this effect? Material faults? Human errors? Methods and procedures? Software performance? Maintenance errors or the absence of maintenance? Inaccuracies or malfunction of the measurement device? Environment - chemicals, dust, vibration, temperature, humidity, shock? Use the 6M’s to help brainstorm and organize potential causes of failures. Man Machine Method Measurement Material Mother Nature (Mileau)
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Almost all errors are caused by humans
Source Forgetfulness Errors due to misunderstanding Errors in identification Errors made by amateurs Willful errors Inadvertent errors Errors due to slowness Lack of standards Surprise errors Intentional errors Response Establish a routine Training for behavior modification Standardizing procedures Training engagement and attentiveness Training skill building, Basic education, life experience Discipline
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Process Control Examples
Standardized work instructions or procedures Fixtures and jigs Mechanical interfaces Mechanical counters Mechanical sensors Electrical/electronic sensors Job sheets or process routings Bar coding with software integration and control Marking Training and educational safeguards Visual checks Gage studies Preventive maintenance Automation (real time control) Statistical Process Control (SPC) Post-process inspection or testing
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Typical Process Documents
Visual aides Work instructions Inspection instructions Inspection records SPC records Equipment operating instructions Training records Traceability records
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In Summary FMEA is another tool when a team has knowledge of a process
It documents “known” failures and fixes It can be an excellent training tool Questions?
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