During the first six months after the publication of its first edition in June 2019, the AIAG & VDA FMEA Handbook gained popularity in the global automotive industry. Both U.S. and European OEMs have started to require the AIAG VDA approach to failure mode and effects analysis (FMEA) in their programs. Like the AIAG Guidebook, fourth edition, the handbook provides guidance, instruction, and illustrative examples of the requisite analytical techniques. The activities and analyses historically involved in FMEA have been formalized as discrete steps in the handbook.

 The seven-step approach described in the handbook and outlined here guides the development of design, process, and supplemental monitoring and system response of FMEA through the sequencing (and the iteration) of described activities.

Step 1: Planning and preparation

Develop a failure mode and effects analysis (FMEA) project plan, including the identification of:
• The intent or purpose of developing the design or process FMEA
• The timing required to support critical product and manufacturing engineering decisions
• The multidisciplinary team of knowledgeable participants
• The tasks that will be required in FMEA development, beginning with the definition of the scope and level of the product or process to be analyzed, the product interfaces to be included, a decision whether a baseline/foundation/core FMEA will be used as a starting point for analysis
• The tools that will be used, e.g., adherence to which FMEA guidelines or “standards,” which software—spreadsheet or dedicated FMEA

Step 2: Structure analysis

Depict the product or process to be analyzed using an appropriate graphical or visual method.
• One new aspect of the handbook approach is the analysis of the “focus element” not as a standalone product but relative to product at the next higher level and the next lower level. The relationships among the system, subsystem, and components may be complex and challenging to analyze, especially without FMEA software.
• A boundary diagram or tree-structure diagram indicating the elements of the system or subsystem, the interfaces among elements, the interfaces between the target product and external elements would be employed in the design FMEA.
• A process flowchart or process tree structure that indicates the step-by-step process involved in manufacturing or assembling the target product or focus element, the specific work elements that make up each process step, and the higher-level process “item” would be used in depicting a process FMEA.

Step 3: Function analysis

Identify the functions to be performed and the requirements or criteria by which their performance is evaluated, for both design and process FMEA development.
• The handbook approach facilitates the flow-down and traceability of functions and requirements, from product level to level, including from customer to supplier.
• For the design FMEA (DFMEA), functions and requirements are identified by the focus element, the next lower level functions and characteristics, and the higher-level item that the focus element enables. Functions may be developed in tabular form or as a function-analysis tree structure. This function tree is usually developed in conjunction with the tree structure.
• For the process FMEA (PFMEA), the functions that each step of the manufacturing or assembly process must achieve on producing the product or focus element are identified. These are the functions (i.e., characteristics to be achieved) that are required at the next lower level, work-element level, and at the next higher level; the functions to be achieved overall; and the collective sequence of manufacturing or assembly steps. The depiction of step-by-step (i.e., workstation by workstation) achievement of each function and next lower level characteristic(s) is readily shown in a process flowchart.

Step 4: Failure analysis

Identify failure modes, effects of failure, and causes of failure.

The failure analysis step described in the AIAG & VDA FMEA Handbook is significantly different from the analysis of failure described in the AIAG FMEA Guidebook, fourth edition. (See figure 1.) The handbook instead promotes the use of a “failure chain” of the failure mode at the focus level, the effect of failure at the next higher level, and the cause of failure at the next lower level.

Figure 1: Failure analysis step from the AIAG & VDA FMEA Handbook, first edition, 2019

In the design FMEA, the definition of multiple types of failure modes—e.g., loss of function, degradation of function, intermittency of function, partial functioning, and unintended functionality—is the same for DFMEA in both the handbook and the AIAG Guideline. Failure modes apply to the failure of the focus element product to meet requirements.

Effects of failure are evaluated for impact on the next-higher level of product.

Causes of failure, per the handbook, are typically assigned to the components that make up the focus level of the product. Causes of failure at the focus-element level are only cursorily mentioned.

Given that most design related causes of failure occur at the interfaces between elements, the handbook’s emphasis on failures at the component level, does not appropriately address a very significant issue.

Some dedicated FMEA software systems, notably the Omnex AqUA Pro software, acknowledge the important need to include the analysis of integration and interface failures at the focus-element level. DFMEA improvement should be focused on causes of failure that are within the control of the FMEA team, vs. just assigning causes to the supplier or to a lower-level product.

Additionally, the handbook illustrates the relationship among different levels of product: system, subsystem, components, and feature characteristics, failure effects, failure modes, and failure causes cascade from one product level to the next. (See figure 2 below.)

Figure 2: Relationship among different levels of product, from the AIAG & VDA FMEA Handbook, first edition, 2019

The process FMEA also uses the failure chain as a model for failure analysis.

Failure mode, again using the various aspects of failure (e.g., loss of function, degradation of function, intermittent function, partial function, and so forth) is evaluated at the focus element.

Cause of failure at the next-lower work element level are also defined.

Effect of failure on the end-user, the plant personnel, and the production operation at the next-higher level are separately identified. Note: The effect of failure on the end-user is communicated from the design to the process FMEA. The PFMEA relies on this information to comprehensively address effect.

In both the DFMEA and PFMEA, the severity of the effect of failure is rated on a 10-point scale.

Step 5: Risk analysis

Estimate the level of design or process risk by assigning severity of effect, occurrence of the cause, and detection of the cause of failure.
• As in the AIAG Guidebook, fourth edition, the AIAG & VDA FMEA Handbook employs 10-point rating scales to evaluate severity, occurrence, and detection.
• The recommended method of combining these three indices into a single composite value is no longer the risk priority number. In the handbook the action priority matrix, a three-axis reference table, is used to assign a relative high, medium, or low need for action.
• The occurrence rating of the cause of failure is based on the current use of prevention-oriented DFMEA or PFMEA controls as well as the historical incidence of the causes of failure, e.g., field failures, warranty, customer issues, in-plant test and inspection failures (PFMEA); and design verification or validation failures (DFMEA).
• The detection ranking of the cause of failure is predicated on the effectiveness and capability of the detection control to assess the cause of failure, and during the product development timeline (DFMEA) or the process (e.g., within station, subsequent station, end of line) when the cause of failure is detected. Per the handbook, detection-oriented design and process controls are focused on failure mode in addition to cause of failure.

Supplemental Step 5A: Link special characteristics to functions and requirements
• The Omnex FMEA development process formally includes the identification of special characteristics and the linkage of FMEA from level to level and between design and manufacturing
• Identify potential special characteristics in the DFMEA, based on severity ratings and potential performance safety concerns.
• Transfer identified, potential special characteristics from the DFMEA to the PFMEA to underline the criticality and importance of process controls.
• Further identify special characteristics in the PFMEA based on the manufacturing or assembly organization’s station-by-station, and work element by element, process capabilities, and in-plant failures.

Step 6: Optimization

Based on risk evaluation, determine which aspects of the design and process require risk mitigating actions, and define those actions.
• Identified actions require the assignment of a person responsible for completion, a target date, status of each  action, assessment of the effectiveness of actions, and re-rating of completed actions.
• Organizations may choose to use the suggested action priority matrix ratings of FMEA line items, or use company-specific values as criteria for establishing the need for further actions.
• Collaboration among the FMEA team, suppliers, customers, and company management is often needed to develop appropriate actions to reduce risks.

Step 7: Results and documentation

Summarize, highlight, communicate, and document the findings, risk reductions, and remaining residual product and process risk
• Develop a comprehensive report that includes the final risk status of the product or process
• Document and bring closure to the original FMEA goals, including whether the purpose of the FMEA was achieved, the high-risk failures that were addressed, and those that remain open
• Actively involve management in the review of findings

Supplemental step 7A: Document linkages
• The Omnex FMEA development process includes formal linkage of critical quality documents to design and process FMEA.
• Link content of design FMEA, and prevention and detection design controls, with the design verification plan and report
• Link the content of process FMEA, and prevention and detection process controls, with the process control plan, which subsequentially links with operator work instructions.

Omnex continues to incorporate innovations to FMEA. Most recently it has developed a methodology for identifying and including multipoint failures in the design FMEA. Using this approach, the DFMEA would serve as a repository for potential faults and failures resulting from the simultaneous and sequential causes, in addition to the traditional single causes. Additionally, the multipoint FMEA allows the FMEA, failure mode effects and diagnostic analysis (FMEDA), and fault-tree analysis to link; this is especially important to mechatronic and electronic designs.

Omnex has written white papers and conducted free webinars on these additional tools and topics and the AIAG VDA FMEA. Visit Omnex’s Resource center or contact Omnex at info@omnex.com.