|
|
This Month's Theme is
Function Types
Next month's theme will be "Use of Failure Mechanisms in FMEA"
Every month in FMEA Corner, join Carl Carlson, a noted expert in the field of FMEAs and facilitation, as he addresses a different FMEA theme (based on his book Effective FMEAs) and answers your questions.
Questions and answers are a great way to learn about FMEAs, for both experienced and less experienced FMEA practitioners. Please feel free to ask any question about any aspect of FMEAs. Send your questions to Carl.Carlson@EffectiveFMEAs.com, and your contact information will be kept anonymous. All questions will be answered, even if they are not featured in the FMEA Corner.
func·tion [fuhngk-shuh n, noun]
The FMEA definition of "function" is "what the item or process is intended to
do, usually to a given standard of performance or requirement."
types [tahyp, noun]
The Merriam-Webster Dictionary defines "type" as "a particular kind, class,
or group."
What are function types?
"Function types" are the different kinds or groups of functions that are used in an FMEA. Basic functions fulfill the purpose of a product or manufacturing process. Interface functions should be included when they are within the scope of the analysis. Additional functions may be added regarding safety, ergonomics, product appeal, laws and regulations, product installation, portability, storage, etc.
Checklist of function types
Here is a checklist of the various types of functions to help ensure that no primary functions are missed when performing an FMEA. Choose the types of functions that apply to the given analysis.
- Basic functions (the primary purpose of a product or manufacturing or assembly operation)
- Interface functions (from the FMEA block diagram or FMEA interface matrix)
- Safety functions (during manufacture or use)
- Reliability functions (life of the product)
- Product-appeal functions
- Ergonomic functions
- Human-interaction functions
- Legal and regulatory functions
- Functions relating to product installation
- Packaging and shipping functions
- Fluid-retention functions
- Service functions
- Storage functions
- Design for manufacturing or assembly functions
FMEA Tip of the Month
Not all of the function types apply to every FMEA. FMEA procedure includes identifying the primary functions of the item or process, and the function types can help to ensure that the FMEA team does not miss any of the primary functions.
Application of "Function Types" in Xfmea
Some practitioners add a column called "Function Types" in their FMEA worksheet, in order to document the type of function. Xfmea can easily support this user-defined field.
In order to add a user-defined field to the Function properties, choose Project > Configurable Settings > Interface Style. In the Edit Interface Style window, click on Functions (under the FMEA heading). Then, select one of the text type user-defined fields in the Properties column and change the "Display Name" to "Function Type." Remember to click Yes in the Enabled column, and OK.
Below is an example of a column called "Function Type" that was added to the all-terrain bicycle system FMEA. The illustration is generated from Xfmea’s report generation tool.
Problem
Do functions relating to error proofing belong in a Design FMEA or a Process FMEA? What function types would these be? [Show/Hide Answers]
Answer: Error proofing can apply to a product design or a manufacturing process.
It is possible to change the product design so that errors in manufacturing or assembly processing are reduced or eliminated.
Example: A wiring connector is designed so that it can only be assembled in the correct orientation.
In this example, a function of the wiring connector might be "the wiring connector has a design feature that makes it impossible to assemble in the wrong orientation."
This function belongs in the Design FMEA, and the function type would be "Design for manufacturing or assembly functions."
The manufacturing or assembly process can be changed so that processing errors are reduced or eliminated.
Example: Wires that are assembled in a wiring harness are color-coded to ensure the correct wires are assembled.
In this example, a function of the wiring harness assembly might be "operator easily assembles the color-coded wires into the wiring harness."
This function belongs in the Process FMEA, and the function type would be "Ergonomics."
Something
I’ve always wanted to know about FMEAs
The important thing is not to stop questioning. - Albert Einstein
A HotWire reader submitted the following question to Carl Carlson. To submit your own question about any aspect of FMEA theory or application, e-mail Carl at Carl.Carlson@EffectiveFMEAs.com.
Could you tell me exactly what the legal and regulatory items that must appear in an FMEA are? I have something in the Process FMEA, but it is worded generally. I would like to see if it should be worded more specifically.
Is it true that the Severity for Legal and Regulatory is “9”?
Carl: Thanks for your questions.
One of the function types is "legal and regulatory functions." These often can be found in technical specifications or other documents that contain product requirements. They can be included in the Functions column of the FMEA, and analyzed the same as other functions in the FMEA.
In my experience, it is best to avoid "generic" legal and regulatory functions. They should be based on the specific legal and regulatory requirements of the item being analyzed. For example, there may be air emissions regulations that are associated with spray-coating aircraft during manufacturing. When analyzing the spray-coating process, one of the functions could be "meets air-emission regulatory requirements based on document XYZ."
Regarding your question about "severity for legal and regulatory," if you are using the AIAG reference manual or SAE J1739 standard, the severity scale criteria includes "noncompliance with government regulations" without warning (10) or with warning (9).
About the Author
Carl S. Carlson is a consultant and instructor in the areas of FMEA, reliability program planning and other reliability engineering disciplines. He has 35 years of experience in reliability testing, engineering and management positions, and is currently supporting clients from a wide variety of industries, including clients of HBM Prenscia. Previously, he worked at General Motors, most recently senior manager for the Advanced Reliability Group. His responsibilities included FMEAs for North American operations, developing and implementing advanced reliability methods and managing teams of reliability engineers. Previous to General Motors, he worked as a Research and Development Engineer for Litton Systems, Inertial Navigation Division. Mr. Carlson co-chaired the cross-industry team that developed the commercial FMEA standard (SAE J1739, 2002 version), participated in the development of SAE JA 1000/1 Reliability Program Standard Implementation Guide, served for five years as Vice Chair for the SAE's G-11 Reliability Division and was a four-year member of the Reliability and Maintainability Symposium (RAMS) Advisory Board. He holds a B.S. in Mechanical Engineering from the University of Michigan and completed the 2-course Reliability Engineering sequence from the University of Maryland's Masters in Reliability Engineering program. He is a Senior Member of ASQ and a Certified Reliability Engineer.
Selected material for
FMEA Corner articles is excerpted from the book Effective FMEAs, published by John Wiley & Sons, ©2012.
Information about the book Effective FMEAs, along with useful FMEA aids, links and checklists can be found on www.effectivefmeas.com.
Carl Carlson can be reached at carl.carlson@effectivefmeas.com.
