Critical Characteristic Symbol - ASME Y14.100 Standard (Engineering Drawing Practice)

[Marc]

--> Subject: DRAFTING STANDARD Date: Wed, 26 May 1999 12:41:42 -0400
--> From: dkaralash -- parker.com
--> To: Forum_Mail -- qs9000.com
-->
--> I'M LOOKING FOR INFORMATION ON A QS9000 DRAFTING STANDARD THAT
--> GOVERNS THE SYMBOL REPRESENTING A CRITICAL (GO, NO GO) TOLERANCE ON
--> A PART. THE STANDARD IS RELATED TO F.E.M.A. I WOULD APPRECIATE ANY
--> HELP YOU COULD GIVE ME ON THIS, AND WILL SUGGEST YOUR SIGHT TO MY
--> CO-WORKERS IN THE FUTURE.

There is no QS9000 'standard' critical characteristic symbol that I am aware of. Download the FMEA file in the pdf_files directory ( Elsmar Cove Free Files Directory ) and look around page 20 or so for some definitions of critical, safety and other characteristics. Also see Appendix C of QS-9000 for symbols and explainations.

Each company has it's own symbol for a critical characteristic. Ford, GM, Chrysler and probably your company. The requirement is that you recognize critical characteristics of your customers and that you identify them as appropriate in your business. If you get customer prints with critical characteristics and you 'translate' them to your 'format' and you use bowties as your symbol for a critical characteristic then those they marked should be marked with your 'bowtie' (or whatever). There is no standard which tells you any specific symbol that you must use nor is there any such requirement for a specific symbol.

[This message has been edited by Marc Smith (edited 26 May 1999).]

[Wes Bucey]

Critical characteristic drawing symbols are merely a specific "flagnote symbol" which refers to a descriptive note on the drawing.

In general practice, the drawing notes will describe a flagnote symbol specific to that drawing. The flagnote symbol is then added to each characteristic on the drawing to which that specific note applies.

Marc is correct in writing that there is no universal flagnote symbol or descriptive note for the concept: "critical characteristic."

Organizations may devise a set of flagnote symbols and corresponding text for the note which ALL designers and draftspersons within the organization shall use in a consistent manner.

Obviously, organizations come in all sizes, ranging from one person to hundreds of thousands of people. Thus, outside entities may encounter a variety of symbols as well as a variety of specific texts or definitions contained in the note to which the symbol refers. The operative advice is to pay close attention to the drawing notes and be on the lookout for any flagnotes which may signal specific customer requirements.

In actual practice, good customers will make a point of calling attention to flagnote symbols which are important to them when negotiating a contract with a supplier. Alas, most customers are not "good," so the supplier must be very vigilant about such notes during the Contract Review process.

In my experience, there are times when stray symbols are present on some drawings WITHOUT the matching note. The use of a flagnote symbol without the corresponding note is most likely an error and a definite red flag there may be other errors in the drawing. Good practice for suppliers who encounter such stray symbols WITHOUT a corresponding note is to call them to the attention of the customer BEFORE continuing to interpret the drawing.

Most likely, the symbol is important, but the note was inadvertently omitted when the drawing was redrawn with CAD.

Second most likely, a previous revision level withdrew the note, but the checkers in the Configuration Management phase of the process neglected to remove the symbols from the drawing as well.

Least likely, an incompetent designer or draftsman made an assumption that "Everyone" knew what the symbol meant since it was so common in his own organization and purposely left out the corresponding note.

[Marc]

Thanks for the details, Wes!

[D.Scott]

I have often seen just a symbol on the print to designate a "key" or "critical" characteristic requiring SPC. Sometimes the symbol is just rubber stamped on the print. There is, in many cases, no specific note explaining the symbol. Use of the symbol is explained in the customer specific requirements.

Dave

[Wes Bucey]

Originally Posted by D.Scott

I have often seen just a symbol on the print to designate a "key" or "critical" characteristic requiring SPC. Sometimes the symbol is just rubber stamped on the print. There is, in many cases, no specific note explaining the symbol. Use of the symbol is explained in the customer specific requirements.

Dave

Such a practice does not correspond with the ASME Y14.100 Standard (Engineering Drawing Practice) for the use of flagnotes. All notes are required to be on the drawing to which they refer (this can be expanded in that the note only needs to be on Sheet 1 of a multi-page bundle of drawings on one product or assembly, but that requires the bundle not be disassembled and the drawings considered separately.)

Thus if the drawing has a statement "conforms to ASME Y14.100" and does not contain the note explaining a flagnote symbol, it does not conform.