similar assemblies - revision control

[zappedagain]

When I have similar assemblies, such as two cables that are wired the same with two different lengths, I have one assembly procedure (AP) that describes how to build both. For example, build 33-01 with 10" leads, and 33-02 with 3" leads. Initially this starts out fine, with everything at Revision A (33-01-A, 33-02-A, AP33-A).

When a change comes along it gets a little weird. For example, if the length on 33-02 needs to change to 3.5", the revision will increase for AP33 and 33-02 (AP33-B and 33-02-B, respectively). But what happens with 33-01? Should AP-33-B say to build 33-02-B and 33-01-A? Or should the revision on 33-01 increase to stay in sync with the AP so AP33-B build 33-01-B and 33-02-B?

In the past I've seen confusion when the revision on the AP and the part don't match ("that's a rev B - what, the part or the AP?"). For that reason we would bump the revision on 33-01 even though there were no changes (except the labeling). The ECO would state to use all the 33-01-A up and then start using 33-01-B.

At my present company I'm getting push-back about having a meaningless revision bump due to the cost of ECOs. When we purchase 33-01-B, the contract manufacturer (CM) will need a new set of drawings so they can verify their procedures (and update the labeling process).

Or should 33-01 and 33-02 each get their own assembly procedure? The reason I haven't liked this in the past is that it is error prone; a fix can be made to one and not the other.

I'm sure I'm not the first engineer to have this situation. How do you handle this?

Thanks,

John D

 

[IRstuff]

> I would agree with your company that rev'ing a drawing simply to roll the rev letter is not a productive activity

> Seems to me that this should be part of your ECO approval process checklist, i.e., when AP33-01 come up for ECO approval, the CCB should ask the engineer to identify all relevant revs that are affected and to show that the other revs that are affected also have concurrent ECOs. The ECO itself should have a box that indicates "Affected Drawings."

That would seem to part and parcel to what you would do if you had NHA and NLA designations on an assembly or component drawing.

TTFN

FAQ731-376

 

[zappedagain]

What's NHA and NLA?

 

[mcgyvr]

If they have the same drawing and AP then they both must Rev up at the same time... If that is a problem then change it to a single drawing/AP..
We do the same in that wire assemblies that only vary in length are on the same drawing. If the length changes all the assemblies on that drawing get rev'd up too. At my company thats a simple thing to do..Sounds like your company must have more paperwork/hands that must touch the ECO,etc..

 

[IRstuff]

next Higher assembly, next Lower assembly

The issue with rev numbers may not be problem if the assembly is the final product, but in cases where it's a subcomponent, or there is a significant maintenance system, arbitrary revision changes can cause massive ripple effects down the line. We have a product that is over 20 years old and the maintenance manuals need to revised every time a revision is made, and at the very minimum, the compatibility table needs to be updated, so that you know whether AP33-04 can be used in place AP33-01 and so on.

You can imagine the complexity of field maintenance manuals that have upwards of 50 revisions on some basic components.

TTFN

FAQ731-376

 

[Henneshoe]

I agree that bumping the revision on a part that is not changing is not productive.

We handle this by using a numerical revision on the documents and a alphabetic one on assemblies. This removes the link between the two in peoples minds and they are generally less confused by a Rev A assembly that is built with AP rev 02.

If most of the instructions are the same, then I would not separate the APs for the assemblies. If a step changes that is common to both APs, then it doubles your work to update the procedures.