AIAG FMEA (Failure Mode & Effects Analysis)
Fourth Edition
Welcome to the Quality Associates International FMEA Fourth Edition web page. The purpose of these pages is to review changes to the new FMEA Handbook and to introduce prescriptive approaches to make your FMEA process meet the new TS16949 requirements for FMEA and APQP.
The Web page is not intended to be a substitute to the AIAG FMEA Fourth Edition, but is intended to quickly convey the very important changes of the Fourth Edition FMEA guideline document.
The Fourth Edition FMEA document is a great leap forward in the FMEA understanding and should be acquired and reviewed in detail. QAI is a member organization of AIAG and we provide more prescriptive methods and processes to implement the FMEA process efficiently.
Changes compared to the third edition:
- Addition of prework activity
- Boundary Diagram
- P or Parameter Diagram
- Top Down Approach (system, subsystem, and component)
- De-emphasis on the RPN
- New formats for FMEA
- New Ranking Tables
- Tools Linkage
Boundary Diagram
FMEA 4th Edition Boundary Diagram
The addition of the Boundary Diagram as a prework document for Design FMEA brings the emphasis of interfaces of systems/components that are not directly under the influence of the FMEA team’s scope. Interfaces that are not defined and/or managed can become cause or contributors of causes.
Typically the scope of the FMEA is found inside the boundary. QAI has used the Boundary Diagram for 10 years when executing robust engineering and FMEA development. Our process uses 4 types of arrows depicting 4 types of interfaces.
- physical
- energy transfer
- material exchange
- data exchange
For more information on developing Boundary Diagrams, contact QAI at (248) 280-4800 for upcoming training & workshop offerings.
P or Parameter Diagram
The Parameter Diagram is a tool first used for electronics design looking to understand the signal to noise ratio “S/N”. In FMEA, the Parameter Diagram is used to understand the inputs (signal) and outputs (ideal functions or responses) and to list other inputs that may have an impact on the design. Other inputs and outputs are as follows:
FMEA 4th Edition Parameter Diagram
- Control Factors – things the design engineers can control or manipulate to obtain the desired output.
- Error States – outputs that are undesirable either technically (failure modes) or customer focused (effects of failure).
- Noise Factors – noises are things that may be present but are not controllably by the engineer. Therefore he/she must consider them and their impact on the design output.
- Design change may be considered to protect a design against one or more noise factors (Robust Design).
- Noise Factors Include:
- PC to PC Variation – variation where change in output can be measured (within blue print expectations)
- Hint: these may be Special Characteristics
- System Interface – other systems which may impact performance of the design
- Degradation Over Time – where at first it is ok but eventually performance degrades due to exposure of wear
- Customer Misuse – unique ways customers use the design which is not one of our expected functions or ideal functions, but failure to recognize the use may lead to failure
- Environment – factors of environment like salt, temperature, and humidity which may also affect the design performance
- PC to PC Variation – variation where change in output can be measured (within blue print expectations)
Top Down Approach to FMEA
FMEA Top Down Approach
A top down approach is recommended starting at system where failure mode causes become indications of what subsystems or components need to be addressed (causes at system level). This infers that Design FMEA for every component may not be necessary. Risk based direction makes FMEA more efficient.
De-Emphasis on “RPN” Risk Priority Number
The Risk Priority Number has been used to determine actions required. This has always been a problem as it drives “bad behavior”. Clearly actions should be directed at:
- Severity First (9, 10)
- Occurrence Second (Criticality)
- Detection Third (High Detection)
The statement is made that clearly removed RPN as a threshold action based number. Page 57 clearly states the RPN’s importance in actions. QAI has paraphrased this statement many years ago. Our statement, which is compatible to the AIAG statement is: “There is no RPN threshold. There is no number above which a team must take an action or below which a team is excused from taking an action”.
New Formats for FMEA
FMEA Fourth Edition Design Form
AIAG has provided several new formats for FMEA Development. The older formats are still acceptable, as software that is used currently many be very expensive. More interesting is a format which moves the Design or Process controls “prevention” to the left of the Occurrence Ranking. This is a very good format, as prevention affects the occurrence ranking which had previously been to the left of the column.
For more information on this topic contact QAI at (248) 280-4800 or visit our quality blog.
New Ranking Tables
The ranking tables have been clarified especially the detection tables for both design and process FMEA. Please feel free to download the reference cards offered by QAI. There is no charge to download the process and/or design FMEA reference cards, but you must be a registered member of the web site to access the downloads. Register as a member today - it's FREE!
Free download! Blank 4th Edition Design FMEA Form
Free download! Blank 4th Edition Process FMEA Form
Tools Linkage
Characteristics Matrix Level 1 Summation
The Fourth Edition FMEA guidelines define links between tools such as DFMEA to PFMEA and DFMEA, PFMEA and DVP&R Design Verification Plan & Report to the Control Plan (CP). It is left to the reader to determine the specific link between these documents. QAI is very prescriptive as to these links. Our methodology is in line with the guidelines:
- DFMEA effects and severity must be used in PFMEA development if there are Special Characteristics. We recommend a characteristics Matrix to assist in linkage between the DFMEA and PFMEA.
The process flow diagram and process parameters may be listed on the vertical where they are matrixed against design parameters or characteristics and the severity from the DMEA is list on the horizontal.
Links between characteristics and process steps/parameters are transferred to the PFMEA form. The characteristics become a failure mode and the parameters at that process step become causes of failure when they contribute to not making the characteristic correctly.
FMEA Fourth Edition Online Training
Our FMEA Online Training has been updated to include the latest changes from the AIAG FMEA 4th Edition manual. Our new and improved FMEA WBT is now available for purchase. Learn more about our Fourth Edition FMEA Online Training course.
There are many other examples of changes in the FMEA Fourth Edition, but the biggest items have been reviewed here. If you have any comments or wish to open a discussion please visit our Quality Blog.
Feel free to contact us for our latest information and/or schedule an appointment, facilitation or training session. Our telephone number is (248) 280-4800 or you can fill out a brief form online to have a qualified representative contact you.
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