Process Notes on a Drawing
Process Notes on a Drawing
(OP)
Here's a question:
Is it "acceptable" to put a note on a part-drawing stating that the part (part A) can be made from another part (part B) controlled by another different part-drawing.
I think we are trying to keep process notes like this out of drawings, and let Manufacturing decide if they want to use another part to make a part, but in this case Manufacturing wants the drawing to specify that it is OK to do so.
I'm worried that we open ourselves up to a document control nightmare where we have to change the drawing for part A if we change part B in some way....
Opinions?
Is it "acceptable" to put a note on a part-drawing stating that the part (part A) can be made from another part (part B) controlled by another different part-drawing.
I think we are trying to keep process notes like this out of drawings, and let Manufacturing decide if they want to use another part to make a part, but in this case Manufacturing wants the drawing to specify that it is OK to do so.
I'm worried that we open ourselves up to a document control nightmare where we have to change the drawing for part A if we change part B in some way....
Opinions?





RE: Process Notes on a Drawing
It is common for casting, where you have a drawing for the raw casting, and a finished part drawing to define the machining and such.
Seems to fall in a grey area. Is it really process information, or is it material information?
RE: Process Notes on a Drawing
Common on machinings/castings either where different items are made from the same blank or even where the forged/cast part has its own drawing to aid documenation etc.
I've seen it done in at least one case where there was a part that could be made either by modifying an existing machined part or by making it from scratch. This was in the UK though.
We also used to do it a lot for specials & the like.
Depending on how you word it I don't see that you are specifying manufacturing methods which is discouraged (ASME Y14.5 1.4(e)). If you say "MAY BE MADE FROM PART XXXX" I don't see a problem. In fact it's kind of like when you give options on the base material, either different grades or even "MAY BE MACHINED FROM STOCK OR FORGED BLANK" which I once used.
KENAT, probably the least qualified checker you'll ever meet...
RE: Process Notes on a Drawing
Chris
SolidWorks 07 4.0/PDMWorks 07
AutoCAD 06
ctopher's home (updated 10-07-07)
ctopher's blog
RE: Process Notes on a Drawing
Well, the change to part B shouldn't affect function, form or fit and should be fully backward & forward compatible, or it would have to be a new number anyway.
So while it may be a possibility I'd guess it to be unlikely.
It's no more of a nightmare than having to update assembly drawings when a part is changed.
KENAT, probably the least qualified checker you'll ever meet...
RE: Process Notes on a Drawing
The note that is desired is "may be made from part B" which is a little different from saying, "may be made from a blank". The concern I have is keeping up with all these such kind of cross-references which are not formalized in our configuration management system.
-Damon
RE: Process Notes on a Drawing
As regards the config control issue, like I said most issues should be covered by the fact that to keep the same part number and only be a rev the change must be backward & forward compatible.
Things like finishing can cause problems as usually change in finish (e.g. Cad plate to zinc) is considered back & forward compatible but sometimes for compliance reasons isn't really.
However, if in doubt do you have some kind of production permit or waiver system? You could perhaps have one which says "PART XXXX REV A MAY BE MADE FROM PART YYYY REV C" using revs to differentiate is normally bad practic but for a waiver may be OK and avoids the configuration issue to some extent.
KENAT, probably the least qualified checker you'll ever meet...
RE: Process Notes on a Drawing
Chris
SolidWorks 07 4.0/PDMWorks 07
AutoCAD 06
ctopher's home (updated 10-07-07)
ctopher's blog
RE: Process Notes on a Drawing
What's "M/D XXXX, OPT"? OPT is optical or optimium to 14.38, OPTL is optional, am I being dumb?
(Minor pedantic point "/" has pretty much been dropped from standard abbreviations in ASME 14.38a-2002 and 'MADE FROM' isn't in there anyway.)
I did just remember that in the case I remember it being done for full scale production the drawing that it could be made from was effectively obsoleted. The drawing was done in this way to allow the 100s in the field to be modified to equivalent standard.
KENAT, probably the least qualified checker you'll ever meet...
RE: Process Notes on a Drawing
"Art without engineering is dreaming; Engineering without art is calculating."
Have you read FAQ731-376: Eng-Tips.com Forum Policies to make the best use of Eng-Tips Forums?
RE: Process Notes on a Drawing
Or something, I'm no ERP expert.
KENAT, probably the least qualified checker you'll ever meet...
RE: Process Notes on a Drawing
A material or part can be called out, then another also called out as optional.
Chris
SolidWorks 07 4.0/PDMWorks 07
AutoCAD 06
ctopher's home (updated 10-07-07)
ctopher's blog
RE: Process Notes on a Drawing
RE: Process Notes on a Drawing
Also in one government system I worked, the convention was that updating the 'where used' didn't require a rev if it was the only change. Made it a bit less hassle. From what I've seen having it as a note may not be great.
We had a similar debate when we had 2 different drawings for the same item but on different products but that had different customers (both government but different departments). Manufacturing understandably wanted only one drawing/part number. In design we knew we couldnt' do this because the drawing packs had to be independant for contract reasons.
Older drawings would have the note "THIS PART IDENTICAL TO XXX-YYY" or similar. Trouble was when the new rules came in on things like VOC, Cad plate etc one customer wanted their drawings updated while the other wanted to wait. The two parts were no longer identical/interchangeable but the customer who didn't want them changed for treatment also didn't want to pay to have the note saying "THIS PART IDENTICAL TO XXX-YYY" removed. Ahhh!
KENAT, probably the least qualified checker you'll ever meet...
RE: Process Notes on a Drawing
If your drawing shows all the dimensions of your part, it is an adequate control, without your process note. If part A passes inspection, you do not care how they did it. You should not provide manufacturing instructions.
If production determines that part B is identical to part with A with the exception of some easily added features, they have no obligation to tell you about it. You simply do not need to know!
The danger of a note like this is that someone will modify part B so that it cannot be modified to part A. As KENAT points out, modifications like this are bad practise. You should not change form, fit and function of existing parts. How much do you trust your fellow designers? How much control do you have over part B?
Another possibility is that you deliberately designed parts A and B to be identical, with the exception of a couple of features added to A. The last time I did this, I indicated my design intent by generating one tabulated drawing. One view showed all the common features. The other view showed the features that applied only to part A.
You could call up part B as the required material for part A. The drawing for A would show the modifications required to bring part B to part A specifications. This is a good solution if you want to rule out any possibility of fabricating part A from scratch. Otherwise, it is a bad idea.
JHG
RE: Process Notes on a Drawing
RE: Process Notes on a Drawing
Matt
CAD Engineer/ECN Analyst
Silicon Valley, CA
sw.fcsuper.com
Co-moderator of Solidworks Yahoo! Group
RE: Process Notes on a Drawing
Drawoh, I agree with you, I think it is dangerous to make such a note on the drawing, although I have seen it done many times.
The end result of this was: We had a meeting between production and design engineering where we explained that design engineering didn't care how the part was made so long as it met the critical characteristics defined by the drawing. If production wants to change those in order to make the part easier to build or allow some production process that wouldn't currently be allowed because of the current drawing, design engineering would consider to change the drawing. But design engineering can't add a note which references a production process using another part which is not part of the design BOM. So production will do whatever they need to do, the part (part A) will be approved solely on the basis of the Part A drawing/ critical characteristics, and I feel much better!
Thank you all!
RE: Process Notes on a Drawing
Based on how you describe it in your last post then it sounds like you made the right decision.
KENAT, probably the least qualified checker you'll ever meet...
RE: Process Notes on a Drawing
PN xxxxxxx-xxx shall be considerd a make from alternate part.
Ideally make from alternate part rough machined part or casting ( excess mtrl ) fab/machined for hi-use finished parts. Also may be designated as MRP raw mrtl enabling in house machine shop to fab blanks as req'd.
Ray Doyle
SolidWorks 99-07
RE: Process Notes on a Drawing
NOTE: May be made from (Part A) Rev. (#)
Then, if "Part A" is changed and made unsuitable for producing "Part B", the drawing for "Part B" is still correct, assuming that the revision level for "Part A" was changed when the part was made unsuitable. If "Part A" is changed but still suitable for making "Part B", then perhaps you need to update the drawing for "Part B", but even if it isn't changed to say "May be made from (Part A) Rev. (# or #)", it still isn't INCORRECT. If the note for part B isn't updated, the machinist may be able to determine if the new revision of Part A is suitable anyways. In an ideal world, the machinist may even catch the fact and ask you to update the drawing, though I know some places communication between machinists and engineers is limited or non-existant...
-- MechEng2005
RE: Process Notes on a Drawing
or - "SIMILAR TO PART 'B'"? this would allow them to find part 'B' and evaluate it's applicability as a 'make from' part.
RE: Process Notes on a Drawing
To keep the same part number the change that causes the rev change must be backward/forward compatible.
Often the rev of parts is not marked on them even if the part number is, since they should be interchangeable.
Using rev letters to essentially define different parts is generally considered bad practice.
KENAT, probably the least qualified checker you'll ever meet...
RE: Process Notes on a Drawing
RE: Process Notes on a Drawing
Using revision numbers to identify parts generally is frowned upon.
Take that case that we share my part XXXX-RevB, and it meets all our requirements. I move holes and revise the part to RevC to suit some other parts I have modified. Surprise!
Note that the RevB drawing is obsolete, and no longer available for you to get fabricated.
Again, we share my part YYYY-RevB and again, it meets all of our requirements. This time, I discover that I have misspelled DISCOMBOOBERATE on page three, and I revise the drawing to RevC. How do you decide whether the part still works for you or not? This is especially awkward if I am the sort of person who does not fill in revision blocks.
This is nasty and complicated. Do not change form, fit and function.
JHG