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Form, Fit, or Function

Form, Fit, or Function

Form, Fit, or Function

Hello to all,
This is my first post here! I wanted to start off by thanking the community for this chance to discuss a few topics that has come up a few times already.

So I have been designing for 17 years now in the fields of Mechanical machine parts and assemblies, MEP, and Architecture disciplines. Just recently the company which I have been with of going on 5 yrs, has been looking at setting up standards for ECO process and revising drawings. We had a large debate on when to revise or create a new P/N for changing parts. I have always worked off the three "F"'s. To my surprise, ANSI does not follow that. My question is "how was I misled this whole time or did the standard change when ASME and ANSI combined?

All of my experience says to revise a drawing if there is a change to the Form, Fit, or Function of a given part. ANSI states if a part is not backward compatible then is gets a new part number not a new revision.

What are the thoughts of this community?

Nathan Gardner
Mechanical Designer / CAD Admin
Wood Carver - Cheese Maker - Goat Farmer

RE: Form, Fit, or Function

If a part is not backwards compatible, then it is considered a new part and should get a new part number. You are correct too, if FFF changes it should always be revised. The caveat is that some FFF changes should require a new part number as well. I also think it matters if you are building one-off products or not. Example: a safety bar that is 32" long, and it is rev'd to 32.5" long. Customer order new bar and complains it doesn't fit. That change should have triggered a new part number.

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