Last week we went through the key points of Step 3, Function Analysis, of the (draft) 2018 AIAG-VDA FMEA process and highlighted how it differs from the 4th Edition of the AIAG Manual. Some key points we have learned so far are:

  1. In Step 2, Structure Analysis, each System Element is analyzed separately using three columns to gain a more thorough understanding of the product (DFMEA) or process (PFMEA).
  2. In Step 3, Function Analysis, each System Element was analyzed separately in terms of its function and corresponding requirements.
  3. The Function Analysis sets the stage for a comprehensive analysis of failures (Step 4, Failure Analysis) by describing what the product or process should be doing and what (or how) functionality is enabled.

Failure Analysis is Based on the Function Analysis

Step 3 marks the completion of System Analysis and Step 4 begins the second half of the FMEA, Failure Analysis and Risk Mitigation. This half of the FMEA is comprised of three steps: Failure Analysis, Risk Analysis and Optimization.  The information developed and gathered in the first three stages will serve as the foundation to complete the FMEA.

Step 4: Failure Analysis
The purpose of the Failure Analysis Step is to identify failure causes, failure modes and failures effects with their corresponding relationships to establish the basis for risk assessment.
The new (draft) standard introduces the concept of a “Failure Chain” used to visualize failures as part of three links of a chain comprised of the Failure Effect (FE), Failure Mode (FM) and Failure Cause (FC).
  1. The Focus Element is the middle link; the Failure Mode (FM) is associated with the Focus Element.
  2. The Lower Level is the third link; it represents the Failure Cause (FC)and answers the question: “Why is the Failure Mode happening?”
  3. The Upper Level represents the first link; it signifies the Failure Effect (FE) and answers the question: “What happens in the event of a Failure Mode?”
Layout of a DFMEA Steps 2, 3 and 4 on the FMEA Worksheet. The steps are shown stacked since it would be difficult to clearly show them laying side-by-side as they typically are.  CLICK on the graphic to see it in the actual spreadsheet layout side-by-side. (The concept behind the PFMEA and FMEA-MSR are the same.) The color coding shows how each of the columns in the Structure Analysis and Function Analysis are related to the associated column in the Failure Analysis. The example provided is from the example in the (draft) 2018 AIAG-VDA FMEA Handbook.

Step 4: Failure Analysis in the FMEA Worksheet

  1. Failure Effects (FE)

    1. A Failure Effect is the consequence of a Failure Mode.  Describe the effects on the next step of the manufacturing process, the end user and regulatory requirements.  There may be several FEs.
    2. Rate the Severity of the FE on a 10-point scale.

  2. Failure Modes (FM)

    1. A Failure Mode represents any manner in which an item (the Focus Element) could fail to meets its intended function.
    2. For DFMEA studies, assume that the design will be manufactured to the design intent.  Potential errors in the manufacturing process are analyzed by the corresponding PFMEA.

  3. Failure Causes (FC)

    1. A Failure Cause (FC) is an indication of why a Failure Mode (FM) could occur.  The consequence of the FC is the FM.
    2. Identify every potential cause of each FM.
This is a conceptualized graphic showing the relationship between the columns in DFMEA Steps 2, 3 and 4 on the FMEA Worksheet. CLICK on the graphic to enlarge. (The concept behind the PFMEA and FMEA-MSR are the same.) The color coding shows how each column in the Structure Analysis and Function Analysis are related to the associated column in the Failure Analysis. The example provided is from the example in the (draft) 2018 AIAG-VDA FMEA Handbook.

The Failure Analysis is the input for the next step, Risk Analysis.
Conceptually, Step 4 is very similar for each type of FMEA – DFMEAs, PFMEAs and FMEA-MSRs. So, rather than go into specific difference between each, this week we are keeping at a higher level and talking about the Failure Analysis Step in general for all three types of FMEAs.
2018 AIAG-VDA FMEA: Step 4: Failure analysis

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