Archive for FMEA

Detection Evaluation Criteria

FMEAs help us focus on and understand the impact of potential process or product risks.

  • A systematic methodology is used to rate the risks relative to each other.
  • An RPN, or Risk Priority Number, is calculated for each failure mode and its resulting effect(s).

The RPN is a function of three factors:

  • The Severity of the effect
  • The frequency of Occurrence of the cause of the failure
  • The ability to Detect the failure or effect

Calculating the RPN

  • The RPN = The Severity ranking X the Occurrence ranking X the Detection ranking.
  • The RPN can range from a low of 1 to a high of 1,000.

Taking action

  • Develop an Action Plan to reduce risks with unacceptably high RPNs.

Linking FMEAs to Control Plans

  • Use FMEAs as the basis for Control Plans.
  • Control Plans are a summary of proactive defect prevention and reactive detection techniques.

Occurrence Evaluation Criteria

FMEAs help us focus on and understand the impact of potential process or product risks.

  • A systematic methodology is used to rate the risks relative to each other.
  • An RPN, or Risk Priority Number, is calculated for each failure mode and its resulting effect(s).

The RPN is a function of three factors:

  • The Severity of the effect
  • The frequency of Occurrence of the cause of the failure
  • The ability to Detect the failure or effect

Calculating the RPN

  • The RPN = The Severity ranking X the Occurrence ranking X the Detection ranking.
  • The RPN can range from a low of 1 to a high of 1,000.

Taking action

  • Develop an Action Plan to reduce risks with unacceptably high RPNs.

Linking FMEAs to Control Plans

  • Use FMEAs as the basis for Control Plans.
  • Control Plans are a summary of proactive defect prevention and reactive detection techniques.

Severity Evaluation Criteria

FMEAs help us focus on and understand the impact of potential process or product risks.

  • A systematic methodology is used to rate the risks relative to each other.
  • An RPN, or Risk Priority Number, is calculated for each failure mode and its resulting effect(s).

The RPN is a function of three factors:

  • The Severity of the effect
  • The frequency of Occurrence of the cause of the failure
  • The ability to Detect the failure or effect

Calculating the RPN

  • The RPN = The Severity ranking X the Occurrence ranking X the Detection ranking.
  • The RPN can range from a low of 1 to a high of 1,000.

Taking action

  • Develop an Action Plan to reduce risks with unacceptably high RPNs.

Linking FMEAs to Control Plans

  • Use FMEAs as the basis for Control Plans.
  • Control Plans are a summary of proactive defect prevention and reactive detection techniques.

Prioritizing Risk and Taking Action to Reduce Risk

FMEAs help us focus on and understand the impact of potential process or product risks.

  • A systematic methodology is used to rate the risks relative to each other.
  • An RPN, or Risk Priority Number, is calculated for each failure mode and its resulting effect(s).

The RPN is a function of three factors:

  • The Severity of the effect
  • The frequency of Occurrence of the cause of the failure
  • The ability to Detect the failure or effect

Calculating the RPN

  • The RPN = The Severity ranking X the Occurrence ranking X the Detection ranking.
  • The RPN can range from a low of 1 to a high of 1,000.

Taking action

  • Develop an Action Plan to reduce risks with unacceptably high RPNs.

Linking FMEAs to Control Plans

  • Use FMEAs as the basis for Control Plans.
  • Control Plans are a summary of proactive defect prevention and reactive detection techniques.

AIAG-VDA FMEA-MSRs

FMEA-MSRs focus on how well monitoring systems can identify faults (or failures).

FMEA-MSRs were added as a new, supplementary form of FMEAs with the 2019 version of AIAG-VDA FMEA Handbook.

  • The “MSR” in FMEA-MSRs means “Monitoring and System Response.”
  • FMEA-MSRs are intended to help maintain a safe state and a state of compliance during customer operations.
  • FMEA-MSRs identify possible errors or failures that can occur under normal operating conditions.

A key focus of the analysis is to determine if the system (or the end-user) detects an error when a failure does occur and then, as important, what happens next.

  • FMEA-MSRs focus on how well monitoring systems can identify faults (or failures) and how useful response systems are in maintaining a safe state and a state of regulatory compliance throughout the useful life of the product.

Use of FMEA-MSRs help ensure that safety objectives and related regulatory compliance requirements have been fully considered and met.

  • While DFMEAs focus on detection (and prevention) of potential failures, FMEA-MSRs focus on the efficacy of the monitoring system.
  • The intent of FMEA-MSRs is to validate that diagnostic monitoring and the corresponding system responses work as they are intended. This new type of FMEA brings the ISO 26262 functional safety standard into play.

While FMEA-MSRs are intended primarily as a supplement to DFMEAs, not every design warrants a corresponding FMEA-MSR.

  • If a design does not contain active or passive monitoring and response components, there is no need to conduct an FMEA-MSR.

FMEA-MSRs are conducted using the same basic seven-step team approach as DFMEAs. However, there are a few important and significant differences in how the Focus Element is defined and how risk is evaluated; the major differences are recapped below:

  • Determination of Failure Analysis (Step 4): If the component can detect (i.e. Monitor) a failure, a System Response can either fully mitigate the Effect or reduce the impact (the Severity) of the Effect.

Linking DFMEAs to FMEA-MSRs

  • The Risk Evaluation Criteria: With FMEA-MSRs the Occurrence and Detection ratings are replaced with the Frequency Potential rating and the Monitoring Criteria respectively.
  • The Action Priority Tables: The Action Priority Tables used to assign Priority Levels for each issue of an FMEA-MSR are different than those used for DFMEAs, however the basic methodology used to assign Priority Levels is the same.
  • The format for Step 5: Risk Analysis & Step 6: Optimization: Since FMEA-MSRs use a S-F-M (Severity-Frequency-Monitoring) evaluation of risk rather than the S-O-D factors used in DFMEAs, FMEA Worksheet form used to document FMEA-MSRs is modified accordingly.

AIAG-VDA Seven-Step PFMEA Process

AIAG-VDA Seven-Step FMEA Process

The AIAG-VDA Harmonization Project defined a seven-step process for conducting FMEAs.

  1. Planning and Preparation
  2. Structure Analysis
  3. Function Analysis
  4. Failure Analysis
  5. Risk Analysis
  6. Optimization
  7. Results Documentation

The seven-steps are summarized into three phases:

  • Steps 1 through 3 represent the “System Analysis” phase of an PFMEA study.
  • Steps 4 through 6 represent the “Failure Analysis and Risk Mitigation” phase of an PFMEA study.
  • The third phase, Communication, is Step 7, Results Documentation

Step 1: Planning and Preparation

  • The PFMEA study starts with a purposeful and careful definition of the scope.
  • The management team is responsible for setting the scope of the study.
  • Step 2: Structure Analysis

  • Structure Analysis is used to identify and breakdown the the process into its sequential steps, interfaces and logistical elements.

AIAG-VDA Seven-Step PFMEA Process

  • The Structure Analysis uses the boundaries set by the definition of scope in Step 1 to identify each step, interface and logistical element of the process under study.
  • Structure Analysis consists of three expanded columns whose purpose is to facilitate a thorough understanding of the process. Start with the Focus Element in the “middle column,” then identify the Process of which the Focus Element is a part and finally identify all Process Work Elements of the Focus Element.
  • Step 3: Function Analysis

  • Think of the Function Analysis step as exploring what the product should be doing and what the overall process (and each of its steps) should be doing and how that functionality is facilitated.
  • Using the Structure Analysis developed in Step 2, each element is analyzed separately in terms of its function(s) and corresponding requirement(s).
  • Step 4: Failure Analysis

  • In Step 4, the concept of a “Failure Chain” is used to visualize failures as part of three links of a chain.
  • The Failure Chain is comprised of the Failure Mode (FM), the corresponding Failure Effect (FE) and the Failure Cause (FC).

AIAG-VDA FMEA Failure Chain

  • A Failure Mode represents any manner in which an item (the Focus Element) could fail to meet its intended function.
  • A Failure Effect is the consequence of a Failure Mode.
  • A Failure Cause is an indication of why a Failure Mode could occur.
  • Analyzing failures involves identifying how the Focus Elements detailed during the Structure Analysis may fail to perform intended functions documented by the Function Analysis.
  • A failure mode leads to a failure effect triggered by a failure cause.
  • Determining potential causes is at the heart of a PFMEA.

Step 5: Risk Analysis

  • In Step 5, the Severity, Occurrence and Detection of each failure chain is evaluated
  • An Action Priority Level of “High, Medium or Low,” based on S-O-D evaluations as indicated by the Action Priority Tables.
  • The Action Priority Tables do not establish a “risk priority” but rather a priority level for action needed to reduce the risk of failure to function as intended.
  • Every potential evaluation combination is assigned a High, Medium or Low priority according to the AP Table.
  • If the AP level is High, action to improve prevention and/or detection controls (or justification on why current controls are adequate) MUST be taken.
  • If Medium, action to improve prevention and/or detection controls (or justification on why current controls are adequate) SHOULD be taken.
  • And if Low, action to improve prevention and/or detection controls COULD be taken.

Step 6: Optimization

  • The primary objective of the Optimization step is to develop actions that reduce risk and increase customer satisfaction by improving the process.
  • Most actions will likely involve lowering the likelihood of the occurrence of failure causes or improving detection controls; either approach leads to a more robust process.

Step 7: Results Documentation

  • The results of each FMEA study should be fully documented.
  • An FMEA study is not finished until Step 7 has been completed.

AIAG-VDA Seven-Step DFMEA Process

AIAG-VDA 7-Step FMEA Process

There are seven-steps for conducting an AIAG-VDA DFMEA:

  1. Planning and Preparation
  2. Structure Analysis
  3. Function Analysis
  4. Failure Analysis
  5. Risk Analysis
  6. Optimization
  7. Results Documentation

The seven-steps are summarized into three phases:

  • Steps 1 through 3 represent the “System Analysis” phase of a DFMEA study.
  • Steps 4 through 6 represent the “Failure Analysis and Risk Mitigation” phase of a DFMEA study.
  • The third phase, Communication, is Step 7, Results Documentation

Step 1: Planning and Preparation

  • The DFMEA study starts with a purposeful and careful definition of the scope.
  • The management team is responsible for setting the scope of the study.

Step 2: Structure Analysis

  • Structure Analysis is used to identify and breakdown the design into the system, subsystems, assemblies and component elements for DFMEAs.Structure Analysis step of an AIAG-VDA DFMEA
  • The Structure Analysis uses the boundaries set by the Scope Definition (Step 1) to identify every component of the product (design).
  • Structure Analysis consists of three expanded columns whose purpose is to facilitate a thorough understanding of the process. Start with the Focus Element in the “middle column,” then identify the System of which the Focus Element is a part and finally identify all Components Elements contained within the Focus Element.

Step 3: Function Analysis

  • Think of the Function Analysis step as exploring what the product should be doing and how that functionality is facilitated.
  • Using the Structure Analysis developed in Step 2, each element is analyzed separately in terms of its function(s) and corresponding requirement(s).

Step 4: Failure Analysis

  • In Step 4, the concept of a “Failure Chain” is used to visualize failures as part of three links of a chain.
  • The Failure Chain is comprised of the Failure Mode (FM), the corresponding Failure Effect (FE) and the Failure Cause (FC).AIAG-VDA DFMEA Failure Chain Concept
  • A Failure Mode represents any manner in which an item (the Focus Element) could fail to meet its intended function.
  • A Failure Effect is the consequence of a Failure Mode.
  • A Failure Cause is an indication of why a Failure Mode could occur.
  • Analyzing failures involves identifying how the Focus Elements detailed during the Structure Analysis may fail to perform intended functions documented by the Function Analysis.
  • A failure mode leads to a failure effect triggered by a failure cause.
  • Determining potential causes is at the heart of a DFMEA.

Step 5: Risk Analysis

  • In Step 5, the Severity, Occurrence and Detection of each failure chain is evaluated
  • An Action Priority Level of “High, Medium or Low,” based on S-O-D evaluations as indicated by the Action Priority Tables.
  • The Action Priority Tables do not establish a “risk priority” but rather a priority level for action needed to reduce the risk of failure to function as intended.
  • Every potential evaluation combination is assigned a High, Medium or Low priority according to the AP Table.
  • If the AP level is High, action to improve prevention and/or detection controls (or justification on why current controls are adequate) MUST be taken.
  • If Medium, action to improve prevention and/or detection controls (or justification on why current controls are adequate) SHOULD be taken.
  • And if Low, action to improve prevention and/or detection controls COULD be taken.

Step 6: Optimization

  • The primary objective of the Optimization step is to develop actions that reduce risk and increase customer satisfaction by improving the product.
  • Most actions will likely involve lowering the likelihood of the occurrence of failure causes or improving detection controls; either approach leads to a more robust design.

Step 7: Results Documentation

  • The results of each FMEA study should be fully documented.
  • An FMEA study is not finished until Step 7 has been completed.

AIAG-VDA FMEAs

FMEAs help us focus on and understand the impact of potential process or product risks.

  • A systematic methodology is used to rate the risks relative to each other.
  • An RPN, or Risk Priority Number, is calculated for each failure mode and its resulting effect(s).

The RPN is a function of three factors:

  • The Severity of the effect
  • The frequency of Occurrence of the cause of the failure
  • The ability to Detect the failure or effect

Calculating the RPN

  • The RPN = The Severity ranking X the Occurrence ranking X the Detection ranking.
  • The RPN can range from a low of 1 to a high of 1,000.

Taking action

  • Develop an Action Plan to reduce risks with unacceptably high RPNs.

Linking FMEAs to Control Plans

  • Use FMEAs as the basis for Control Plans.
  • Control Plans are a summary of proactive defect prevention and reactive detection techniques.

Traditional (RPN) FMEAs

We use the phrase “Traditional (RPN) FMEAs” to refer to the way FMEAs have been conducted for over 70 years. A key distinction of these types of FMEAs is that the failure analysis process results in a Risk Priority Number or RPN that is used to prioritize failure modes for improvement and risk reduction efforts.

In 2019, the automotive industry revamped the FMEA process used in their global supply chain. We call these FMEAs AIAG-VDA FMEAs (AIAG and VDA are the American and German Automotive Industry Associations that spearheaded the task force that developed the new approach to FMEAs). A key change with the updated methodology is the elimination of the RPN. In its place are Action Priority Tables. Initially, this type of FMEA is only used in the automotive industry although we expect other industries will adopt the new process.

This section of the FMEA Resource Center, deals with the Traditional (RPN) FMEAs. If interested in the AIAG-VDA FMEA process,

History of FMEAs

History of FMEAs

FMEAs have been used as a risk identification and reduction tool for decades. The approach was developed by the United States Military in the late 1940s and was used for almost 70 years with relatively small evolutionary enhancements. In 2019, substantial changes were introduced as AIAG and VDA “harmonized” their differences for conducting FMEAs.

Background on FMEAs

The first widely known use of FMEAs was by the US Military at the end of the 1940s. The military developed the technique to reduce sources of variation and corresponding potential failures in the production of munitions – and it proved a highly effective tool.

Once it was recognized that project risk was reduced by the military’s use of FMEAs, NASA adopted the methodology as a crucial project planning technique as well. FMEAs proved to be vital to the success of the Apollo (and subsequent) NASA missions. FMEAs are widely used by the civil aviation industry to assess aircraft safety.

The automotive industry was an early adoptee of FMEAs as well. The Ford Motor Company led the way as an internal response to their safety and public relations issues with the Ford Pinto model in the mid-1970s. Other automotive manufacturers in the US, Europe and UK soon followed Ford’s lead.

AIAG was formed in 1982 to get fierce (US) auto industry competitors to collaborate and agree on standardized use of quality improvement tools and practices such as FMEAs, SPC (statistical process control), MSA (measurement system analysis) and related practices.

2019: FMEAs Get a Makeover

The AIAG-VDA FMEA Harmonization Project was a collaboration between OEMs and Tier 1 supplier members of AIAG and VDA.  It represents the culmination of a three-year project revising and improving FMEA methodology.  The result is one common foundation for FMEAs across the global automotive sectors represented by AIAG and VDA.