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What information to put on measurement Dimensional Results

GunLake

Involved In Discussions
#1
Hi,
Just wondering what info you guys put on your dimensional Results? I have never put reference only or basic dimensions on mine and so far no issues from any customers. So just wondering what everyone else does.
 

optomist1

A Sea of Statistics
Trusted
#2
industry, your customer requirements?? generally it would seem that more info is better than less info; P/N, dwg rev...etc, etc, how else would you nail down the specifics and traceability?? I maybe be missing something here. Also are /i assume you are referring to PPAP DIM, and or "Annual Layout"...usually 10 pieces.
 

GunLake

Involved In Discussions
#3
industry, your customer requirements?? generally it would seem that more info is better than less info; P/N, dwg rev...etc, etc, how else would you nail down the specifics and traceability?? I maybe be missing something here. Also are /i assume you are referring to PPAP DIM, and or "Annual Layout"...usually 10 pieces.
Yeah PPAP, I put Part Number, Rev, Etc. But what i normally don't is the reference only dimensions, I was thinking about it today and couldn't find any information on it and never had issues, So just kind of curious what everyone else was doing. I think thats just how i was trained but i can't remember. Been doing it that way for 6 years at my old job and now the past 6 months at my new.
 
#4
I have always shown the basic dimensions, and entered them in as the dimension shown on the print. Reference dimensions, on the other hand, are something I try and stay away from - since they are REFERENCE only, then they are not constrained by the print tolerances, but try and convince your customer of that.
 

Emmyd

Involved In Discussions
#5
Depends on what your customer requires. We have one customer who only wants items that require a judgement and several customers that expect to see every dimension that is on the print laid out on the layout. That is a fun one, because trying to explain to design engineers and "GD&T guru" why you don't want impossible to measure dimensions on the print. They don't even know their own company's requirements.

I know that Ford used to require all callouts on a print be fully laid out as well.
 

John Predmore

Involved In Discussions
#6
It is good practice for a FAI to bubble and list basic dimensions, even if the measurement result is N/A. First article inspection is a risk reduction activity. If the CMM operator or the machinist read the print wrong or programmed the wrong dimension in their machine or overlooked a quality check, this is one opportunity to discover the error.

I occasionally see measurements of basic dimensions reported on a First Article Inspection, for example the X and Y dimension to the center of a certain hole. I know measuring X and Y dimension are not required in a pure GD&T sense, I know it is not a violation to include those. I figure the machinist drilling the hole wants to know where the actual hole is relative to his datums, instead of how far from ideal position. The machinist or the engineer is the person who sets up the machine. If he wants those dimensions from the CMM operator, I am not going to insist they do not belong on the PPAP document.

A reference dimension is a dimension which is defined somewhere else, either in a different view, a different drawing, or maybe a catalog for an off-the-shelf component, and as such, the reference dimension may not be bound by the generic print tolerance block. The reference dimension is generally included as a courtesy to the drawing user. It is not wrong to measure it, it is not wrong to include it. Just as it is convenient to have the dimension show on a drawing as a reference, it may be convenient to have a measurement of the reference dimension on the dimensional report in the context of all the other measured dimensions. I might comment that measurement is not required, in an attempt to educate the supplier or save him some work, but the time savings is not worth an argument.
 
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