Dimensions Before or After Coating? Drawing states ASME Y14.100 and Y14.5 apply

[timmlaww3256]

All,
I have a supplier that has submitted parts made to a third party's drawing. The drawing states that "ASME Y14.100 and Y14.5 applies." These parts have a coating applied IAW NOTE 3 (see below), and the thickness of the coating is not specified. The problem I have is that a typical feature is dimensioned (thickness) at 0.048 +/-0.005", but feature measures at 0.058".

The supplier's position is that the dimensions apply BEFORE coating. It is my position that drawing dimensions apply AFTER coating has been applied. I say the drawing describes an item configuration including all drawing notes. How could NOTE 3 "not count" for dimensioning and tolerancing? I would expect a "Dimensions apply before coating [Note 3]" type statement otherwise. I really need something solid to support my position because my supplier has decided to play "Lawyer-ball" on this issue, and wants proof that I am correct.

Any help is appreciated

Timmlaww

 

[sitapaty]

Re: Dimensions before/after coating (?)

The dimensions are for 'after plating' condition.The supplier should manufacture under sized threads and maintain drg.size after plating.This requires some geometrical calculation on treading diameters and monitor strictly the preplated dimensions.Preplated dimensions are generaly not given on drgs.
-Sitapaty

 

[rob73]

Generally I would agree with you, if a finished part drawing states that a part is coated then the dimensions should reflect the finished sizes, if they do not then this should be implicitly stated using a note.
The dimension in question, is it a machined/manufactured dimension or is it a thickness of plate etc. The later could cause issues as sheets and plates are generally standard sizes so your supplier would have difficulty meeting the drawing dimension using standard material. just a thought.
Rob

 

[jbeckproe]

May I ask what the coating is?

 

[Jim Wynne]

All,
I have a supplier that has submitted parts made to a third party's drawing. The drawing states that "ASME Y14.100 and Y14.5 applies." These parts have a coating applied IAW NOTE 3 (see below), and the thickness of the coating is not specified. The problem I have is that a typical feature is dimensioned (thickness) at 0.048 +/-0.005", but feature measures at 0.058".

The supplier's position is that the dimensions apply BEFORE coating. It is my position that drawing dimensions apply AFTER coating has been applied. I say the drawing describes an item configuration including all drawing notes. How could NOTE 3 "not count" for dimensioning and tolerancing? I would expect a "Dimensions apply before coating [Note 3]" type statement otherwise. I really need something solid to support my position because my supplier has decided to play "Lawyer-ball" on this issue, and wants proof that I am correct.

Any help is appreciated

Timmlaww

I have only a copy of the 1994 version of Y14.5M, and it all it says is that the drawing must state whether dimensioning applies before or after plating/coating. In my own experience, having worked directly in electroplating and in job shops where parts were plated or painted in accordance with customer specifications, the ASSUMPTION is that all dimensions apply to finished parts. My emphasis on "assumption" is that this is one thing that should NEVER be assumed. If the drawing/specifications don't say whether dimensioning applies before or after plating (or whatever) always ask the customer, and always get the answer in writing.

 

[DrM2u]

I really need something solid to support my position because my supplier has decided to play "Lawyer-ball" on this issue, and wants proof that I am correct.

My position is that the customer is the one who specifies if the dimensions are before or after any coating. If you are the customer and your supplier is ISO 9001 registered then the onus is on the supplier to identify your requirements, even those not explicitly stated but important to the product (see Clause 7.2..1.b). Also, in accordance with Clause 7.2.2, the supplier should confirm any requirements that are not documented before accepting the job. Now if in the contract or conditions of purchase you have anything that stipulates that your suppleir must comply with the requirements of ISO 9001 then you have an ace in your pocket. Hope this helps a little.

 

[timmlaww3256]

Thanks for the help everyone!

The base part is injection molded polypropylene.
The coating is a marine/naval paint.
One thing that I have discovered since posting is that the supplier was also contracted to build the tooling, and we have engineering documentation that shows they built the tool slightly smaller than the dimensioned part, explicitly to allow for the coating. It appears that this allowance is insufficient. Since the tooling contract documentation clearly states the intentional dimensional factoring and the reason for it, I'm good.

Great discussion as always, and thanks again to everyone!

Timmlaww

 

[DrM2u]

I am stil not clear who the customer is, but that's for you to know and address.

I have encountered a very similar situation just recently. The organization I am working with is a molder, the customer provided part prints that require the part to be painted, and the molder outsources the painting process to a sub-supplier. The molder was also contracted for making the mold, which is not an uncommon practice. After all, the molder is supposed to be the expert, right?!? The customer was approached about the print dimensional specification and the customer indicated that the dimensions are for the finished part, painted.

Now, the dimensions of the unpainted part can be controlled a little through the molding process. Over-packing the part can cause the dimensions to be a little larger (less shrinkage after molding). Simple logic: over-packing reduces the space between molecules by applying extra pressure to the part for a period of time. When the part cools the molecules have less movement as the material solidifies. Ask the molder to pack the parts less if possible and see if they can reduce the part size. Be aware of other potential side effects, though: non-fill, folds, flow lines, etc.