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If part changes rev is the assemblies change rev as well???

thread768-238523

If part changes rev is the assemblies change rev as well???

If part changes rev is the assemblies change rev as well???

(OP)
Hello all,

I've been looking all over the forum regarding this question and probably I wasn't looking hard enough, because I couldn't find a satisfactory answer.

To give you some background...
There is no MRP or PDM system in place. The files are saved with a different revision at the end (123R1 to 123R2). Sequential numbers, with no meaning.
We are implementing a new part numbering scheme at the company, with some intelligence to the numbers and we are striving to go to a MRP and PDME.
My question is: if you change a rev to a part used in 200 assemblies, are these 200 assemblies changes rev as well??? (part is not changing form, fit or function).
 From PDME stand point, if you change the part and you open an assembly where that part is used, PDM will detect a change in the assembly and will want to bump the rev.
My problem is that you will get to a point that you will loose track of where you used part 123R1 and 123R2 or this is not relevant at all...

Thank you!

C
Replies continue below

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RE: If part changes rev is the assemblies change rev as well???

Only if component revision levels are recorded in your assy Parts List (which is a good reason not to record component revision levels in your assy Parts List). winky smile
Otherwise, I don't think it would be necessary, especially if your PDME tracks it for you.

"Good to know you got shoes to wear when you find the floor." - Robert Hunter
 

RE: If part changes rev is the assemblies change rev as well???

Problems with assemblies not finding parts that have changed is one reason not to include the revision as part of the file name. If you use the system you have indicated that uses the rev in the file name, you will need to resave the assembly files with each part rev to enable the assembly to see the new part. This is not a change to the assembly documetation, just to the file itself. This may get a bit confusing and also might be a large expense for little or no gain.

Peter Stockhausen
Senior Design Analyst (Checker)
Infotech Aerospace Services

RE: If part changes rev is the assemblies change rev as well???

(OP)
Thanks' for your input.
But if you have PDME managing the files and you open the assembly with the latest revision to all the parts, then even if you don't change the assembly, wouldn't PDM see that assembly as modified?
 

RE: If part changes rev is the assemblies change rev as well???

From a drawing/documentation point of view no a revision is not needed, if the assembly does need to go up a rev then arguably the piece part should probably have been given a new part number.

From a CAD point of view, this is I believe why some systems have a distinction between revision and version, version ticks up every time it's saved (or it may be every time it's checked in, can't recall) but revisions are 'hard changes' implemented by the user.

As Pete says, it may be appropriate to leave the rev out of the file name (especially for models rather than drawings) and rely on file properties/meta data of the files.

Also, while it's not your question as such - I'd think twice before going from a dumb numbering system to a smart one.  General concensus is that dumb numbering schemes are more robust and cause less problems than intelligent ones.  There are several threads about this on this site and I think even a link to a formal report about it.

KENAT,

Have you reminded yourself of FAQ731-376: Eng-Tips.com Forum Policies recently, or taken a look at posting policies: http://eng-tips.com/market.cfm?

RE: If part changes rev is the assemblies change rev as well???

When you start to use a PDM system, you will be checking files in and out of the system vault.  When you check them back in with changes, the PDM system will flag them and bump the revs.  You will not have to modify your file names with the revision level.  If the copies you check out have not changed the PDM system will not see a change, no revs will be bumped.

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

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RE: If part changes rev is the assemblies change rev as well???

Whether or not an assembly revision needs to be bumped is often a case-by-case decision. If the change to the part was something insignificant to your application, say paint, then no, but if the change was to something significant, like a dimension, then yes, you may want to be able to differentiate which units where built with which parts and so you should bump the assembly revision (and, of course, record or mark the assembly revision).

What is considered a "significant" change, however, depends highly on your application. For example, if a change is paint only changes the color, this is probably not significant, but if a paint change implements a paint with a flame retardant additive, then that is most definitely significant.

Typically these are the types of questions that a Change Control Board (CCB) would consider before allowing a change to be processed. CCB systems and MRP systems should go hand-in-hand.

RE: If part changes rev is the assemblies change rev as well???

A part only gets revised if it meets the Form, Fit and Function rule, otherwise it should be a new part number.
For the next higher assembly, we used to revise them up until the difference could not be seen graphically. Adding a hole in a bracket, would change the NHA, no matter what was shown. The next assembly would be revised only if the new hole changed any of the drawing views.
 

"Wildfires are dangerous, hard to control, and economically catastrophic."

Ben Loosli

RE: If part changes rev is the assemblies change rev as well???

The obsession with 'form, fit & function' can be misleading.  The important thing is usually whether it's both backward and forward compatible - i.e. completely interchangeable.

ASME Y14.100-2004 paragraph 6.8.1 explains in detail.  I don't think it uses the 'form, fit, function' definition anywhere.

KENAT,

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