Process Notes on a Drawing

[carloabarth]

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?

 

[MintJulep]

I've certainly seen it done before, especially if you are modifying a purchased item.

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?

 

[KENAT]

I've seen it done before too.

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...

 

[ctopher]

A "made from" is acceptable. But having process notes may cause trouble. Better to leave them and have them on a job traveler of some sort.

Chris
SolidWorks 07 4.0/PDMWorks 07
AutoCAD 06
ctopher's home (updated 10-07-07)
ctopher's blog

 

[KENAT]

As regards your configuration control concern.

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...

 

[carloabarth]

Thanks for the feedback guys.

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

 

[KENAT]

Like I said, I've seen it done the way you just clarified. It may not be ideal but I'd say can sometimes be justified.

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...

 

[ctopher]

I prefer "MADE FROM P/N XXXX" or "M/F XXXX (XXXX=part number)". You can also add "M/D XXXX, OPT".

Chris
SolidWorks 07 4.0/PDMWorks 07
AutoCAD 06
ctopher's home (updated 10-07-07)
ctopher's blog

 

[KENAT]

However Ctopher, saying "MADE FROM P/N XXXX" says that's the only thing it can be made from. My interpretation of the OP is that it can be made from scratch or from an existing part.

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...

 

[MadMango]

You can always add the base part as a raw material in the BOM of the "made from" part in your ERP/PDM system.

"Art without engineering is dreaming; Engineering without art is calculating."

Have you read faq731-376 to make the best use of Eng-Tips Forums?

 

[KENAT]

MadMango, I was thinking the same thing but some systems make this difficult. I'm led to believe that with our implementation of SAP it's difficult to add a BOM to something that's categorized as a piece part.

Or something, I'm no ERP expert.

KENAT, probably the least qualified checker you'll ever meet...

 

[ctopher]

"OPT", I meant optional.
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

 

[btrueblood]

I think the OP is saying he has no ERP/PDM system to keep track of parts/releases/revisions. The drawings themselves are the only documents in the system...been there & done that. As far as I know, it is not illegal in any drawing system to add a general note of the form: "This part is used on assembly ####, and may be used for production of part ###." This type of note is of use to engineers/drafters/checkers who may not remember to check other affected assemblies when parts/drawings are revised. It also leads to a nightmare of drawing revisions when new assemblies using the same parts are created (you have to update this note to add the new assy no. to the list).

 

[KENAT]

So, while I don't think it's the main point of the OP the 'where used thing' is done, in fact I think it used to be done more and was if I recall sometimes a box in the title block or edge of the drawing format.

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...

 

[drawoh]

carloabarth,

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

 

[vigildesign]

Sometimes a better note is: "REF NOTE: PARENT PART NUMBER: XXX-XXX-XXX". Let the machinists decide what to do. If they have a part they can use, they may choose to use it. If they have the CNC code, they may choose to use it. If they have the CMM program, they may choose to use it. It depends on how much time you have. As long as your new print has all the dimensions and not existing part feature dimensions as reference, they should give you what you are asking for on your sent out print.

 

[fcsuper]

Another thread about this topic might help too: [thread404-186498]

Matt
CAD Engineer/ECN Analyst
Silicon Valley, CA
sw.fcsuper.com
Co-moderator of Solidworks Yahoo! Group

 

[carloabarth]

Thank you all for the wonderful feedback. It is great to have a forum like this to exchange ideas and get advice from so many competent people in the field.

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!

 

[KENAT]

carloabarth, I have the feeling I missed something on your original post(s).

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...

 

[121560]

The typ note would read as follows;
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