Drawing revision versus Part number change 9

[mechengdude]

i'm sure this has been covered before but I couldn't find it......

Can someone point me to a document that defines when one makes a part number change versus a revision change. I have looked in my ASME and Mil-spec references but can't seem to find it.

My take on the situation is that you make a revision change only when form, fit, and function are not impacted. (ie) if the guy on the floor or out in the field can't close his eyes and reach into a bin with both part configurations and use them interchangeably then its a PN change.

Now a slight wrinkle is that I have also used REV letters stamped on parts in the past as a unique identifier. This is in essence a new PN. I would like to use the PN with rev incorporated on all parts but alas no one wants to listen to me.

anyway a specific document that I could reference would be great.

thanks

 

[ewh]

My understanding is the same as yours. Form, fit and/or function changesrequire a new number.
As far as revision levels, it is a good idea to include them in the marking for traceability purposes. S/N's also accomplish this.

 

[swertel]

It's a matter of symantecs.

If you use the revision as part of the identifier, then revision is also part of the part number, thus just the part number. Basically, you never revise prints, you always create new part numbers and then somewhere in your configuration management plan you have a method defined to show interchangeability.

Other people use dash numbers or completely different base numbers. That's fine too. In your case, what's the difference between using a number as your dash value as opposed to using a letter.

For instance.
Base part number 12345.
Part number is 12345-1.
Drawing number is 12345, Rev A.
I make a change to the part that is a form/fit/function change. Therefore, I need a new part number.
P/N 12345-3 with drawing 12345 Rev B. (I won't explain why I use odd number dashes.)

Your method.
Base part number 12345-A.
Part number 12345-A.
Drawing number 12345, Rev A.
make a change to form/fit/function.
P/N 12345-B with drawing 12345, Rev B.
Since 12345-A and 12345-B are different part numbers, they are implied to not be interchangeable at the next assembly unless that assembly specifically states "alternate component". Therefore, you will have to revise EVERY assembly up the ladder to create a new part number that references 12345-B.

Short story, it's a time consuming and expensive mess. Better to not use Revisions as the unique identifier.

--Scott

http://wertel.eng.pro

 

[KENAT]

In UK defence there was documentation, I can't recal the number or much detail though. I think the form you filled in was a 714/715 but this probably means nothing by itself.

My understanding is that for it to be a true rev change the parts have to be completely interchangeable, i.e. forward and backward compatible. Pretty much as you say.

Although I have seen revs put on components/component packaging this wasn't (normally) because they were being treated as a unique identifier as such, more for the reasons ewh gave.

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

 

[Finethread]

In addition to the form, fit and function rule, I always educate people with:

-If the part is not backwards compatable, a part number change is required.

The example I use most often is that most companies do not manage their inventory by revision level. It's ususally first in, first out. Still, there can, and often is, a mix of revision levels in a bin. So, if an order is placed that calls out for 10 widgets, the stockroom pulls 10 widgets from the bin regardless of revision level. This means that in the same order, two different revisions of a particular part can be used.

 

[Gymmeh]

SO basically this is no formal document on how to do revisions and part number changes?

I have been trying to find information like this in writing because my colleague (degreed ME in sales because he screws up everything- and resents me for having more respect from everyone personally/professionally) does not like to listen to me until I show in an ANSI, ASME...etc standard on the topic. His method varies depending on the day, so its really annoying.

I have been trying to stick with something similar to what you guys have said before and sell him in it also. (He tries hard to avoid anything until is show a formal paper to prove I am right.)

05XX original part and drawing
05XX.2 Major change, which affects form or function.
05XX_REV_A, For drawing calling out plasma cut.
05XX_REV_B, For drawing calling out laser cut with 0.013 change in dim’s (Negligible form change, no change in function)

Thanks for you help, please comment.

 

[swertel]

The best spec I have for rev vs part number is the CMII group

http://www.icmhq.com/

Buy their book

http://www.icmhq.com/CMII Book.html

because I don't think the class is cost effective for what you need.

--Scott

http://wertel.eng.pro

 

[ewh]

Revision of Engineering Drawings and Associated Documents Y14.35M-1997

 

[KENAT]

ewh & Gymmeh I'm not sure that 14.35 does explicitly cover this.

It defines form, fit & function but I couldn't see where it says that if changes to form, fit & function mean the part is no longer interchangeable then it cannot be a rev but should be a new PN.

However, being a genius it occured to me to look in ASME Y14.100-2004 and, Bob's your uncle, all is explained in paragraph 6.8.1 Change Requiring New Identification.

It's a fairly long paragraph, with 5 detailed instances that require new PN, or I'd type it out, interchangeability is just one of them.

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

 

[ewh]

Thanks for the heads up, KENAT!

 

[Gymmeh]

Thanks,

Now all i need is another one of those silly ASME books...

 

[KENAT]

Highlights:

6.8 item Identification

The combination of the original design activity PIN and activity identification establishes an identification unique to that item.

6.8.1 Change Requiring New Identification. New PINs shall be assigned when a part or item is changed in such a manner that any of the following conditions occur:
(a) When performance or durability is affected to such an extent that the previous versions must be discarded or modified for reasons of safety or malfunction. …
(b) When the new version of an item is not interchangeable with the previous version.
(c) When a repair part within an item is changed so that is no longer interchangeable with its previous version. …
(d) When the previous version of an item is limited to use in specific articles, or models or articles, and its new version is not so limited. …
(e) When an item is changed in such a way that it necessitates a change to an operation test, self test, or maintenance test computer program. …

PIN Part Identification Number

Most of the … talk about following the PIN change up through the drawing tree until you reach an assembly that’s interchangeable however, you probably should get the standard itself. ASME Y14.100 actually has a surprising amount of stuff in it, it’s not just a list of standards, and if you’re serious about having ‘industry standard’ drawing packs you probably need a copy.


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

 

[KENAT]

Also, nonmandatory appendix D has some information on this, D13.

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

 

[Gymmeh]

KENAT, Thanks again!

Yes, I am not worried about getting a copy, it just takes time... and telling my boss, then reminding him, then telling him again....

 

[plmguy]

MIL-STD-100, "Engineering Drawing Practices" section 406.13, also describes this using essentially the same words (without the copyright issues):

406.13 Change requiring new identification. When a repair part within an item is changed so that it is no longer interchangeable with its previous version, it shall be assigned a new PIN [Part or Identifying Number]. A new PIN shall also be assigned to the next higher assembly for the changed repair part and to all subsequent higher assemblies up to and including the level at which interchangeability is reestablished. The design or procuring activity shall assign new PINs when a part or item is changed in such a manner that any of the following conditions occur:
Condition 1. Performance or durability is affected to such an extent that superseded items must be discarded or modified for reasons of safety or malfunction.
Condition 2. Parts, subassemblies, or complete articles are changed to such an extent that the superseded and superseding items are not interchangeable.
Condition 3. When superseded parts are limited to use in specific articles or models of articles and the superseding parts are not so limited to use.
Condition 4. When an item has been altered, selected, or is a source control item. (see Chapter 200 and ASME Y14.24M)


You can download a free copy of MIL-STD-100G (as well as DOD-STD-100D and many other CM-related standards) at

http://www.product-lifecycle-management.com/legacy-military-standards.htm

- Ed

 

[KENAT]

Nice plmguy,star for you.

I shyed away from the mil-std as a lot of commercial operations don't seem to like even referencing them (at least, my current employer doesn't).

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

 

[plmguy]

Thanks, Kenat!

Inasmuch as many important MIL-STD formed the foundation of subsequent commercial standards, there's a ton of great stuff available. For example, MIL-STD-100 preceded ASME 14.x, MIL-HDBK-61B [draft] is highly correlated to EIA-649, and MIL-STD-2549 is pretty much EIA-836.

If you're not obligated (contractually or due to regulatory agency) to follow specific commercial standards, many of the government standards are a good -- and free! -- source of useful engineering guidance.

One caution: the MIL/DOD/FDA standards were developed long before computerized CM/PLM systems, and some practices that made perfect sense in 1985 are obsolete now (such as tying part numbers and document numbers together). But, with judicious pruning, you can avoid reinventing the engineering data management process. At least most of the issues you'll have are raised, if not always appropriately answered.

- Ed

 

[Gymmeh]

plmguy,

Looking through them, they seem to be a good "kick in the right direction" when you dont have the Industry standards around.
Star Also!

 

[Proximo]

We control designs by their Revision Letter. We release a new product under Rev "-". Once a change is made, if it affects Form, Fit or Function. The Rev jumps to A and the B and so on.

If it's a minor change to the drawing, such as a correction on spelling. This does not affect form, fit or function and we simply use 1, 2, 3. to note any minor changes.

So you can have a product at Rev. Level A3, but the only marking on the product itself is the current Rev. Level which is A.

This method is used by many PDM systems such as Windchill. A part number change is basically a new product offering.

Many times a revision change is an improvement to a current design, but the original design works perfectly fine. In this case you can have two Revisions that can be sold to the customer with no issues. Eventually you will deplete the original design and only the latest Revision will exist.

If a change is made due to a product failure. We will scrap the inventory and replace it with the improved design at the new Revision Level.

This prevents using so many different part numbers and confusing the customer. Every company will have their own method of handling these type of changes and there is no right or wrong way of doing it. Just different methods that can all work as long as you have control over the process.

"Statues have never been raised to critics, only those criticized."