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Subcomponent Revisions on Assembly Drawing BOM Table

Subcomponent Revisions on Assembly Drawing BOM Table

Subcomponent Revisions on Assembly Drawing BOM Table

My company is looking at the pros and cons of including a revision column to assembly drawings to reflect the subcomponent revision. On typical projects we have 4-5 levels in our top-level assembly. We are starting to get into using more components on multiple projects. Top-level system revisions aren't a concern to them nor is revising every assembly drawing between subcomponent to top-level drawings.

I'm looking for input as to the pro's and con's of such a system. What type of impact, other than time (because time isn't important o.O), could this type of change make? By what other means could revision information be transfered to vendors (that make assemblies) to show them exactly what has changed?


RE: Subcomponent Revisions on Assembly Drawing BOM Table

If you put revision levels of the detail components on your assembly drawings, you will come to regret it. Unless you revise EVERY drawing whenever the component revision changes.
You will have someone requesting part 435 rev A component for assembly 123, when the latest rev of part 435 is F, just because the 123 drawing says use rev A.

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

Ben Loosli

RE: Subcomponent Revisions on Assembly Drawing BOM Table

I agree with Ben.  Sounds like good job security though, as long as the company can afford it.wink
There should be a document and data control process that forwards changed drawings to whomever would require them.  Listing all component revisions on the top assembly drawings is a nightmare waiting to happen.

RE: Subcomponent Revisions on Assembly Drawing BOM Table

You guys don't have to convince me that it's a bad idea.  I'm aware of the logistics nightmare that this is going to cause.  I just can't get our Director of Engineering to see how cumbersome this is going to be to manage.  I sat for nearly 3 hours with him running scenarios on why this is a horrible idea.  I'm trying to find something other than time to be a draw-back, because they are willing to hire someone else to help with data entry.

RE: Subcomponent Revisions on Assembly Drawing BOM Table

Other than the time required for upkeep, there will be inevitable mistakes and omissions, especially as the assembly tree grows.  Good luck!

RE: Subcomponent Revisions on Assembly Drawing BOM Table

Doing it on the assy drawings sounds a bad idea.

However, if you want to keep track of drawing revisions  as part of the drawing pack, rather than just in some ERP or config control software/database then I have a suggestion.

On government contracts in UK the way this was done was to have a drawing list.

For the top level 'deliverable' (or sometimes major sub assemblies) a drawing list was created   This had a list of drawings of all the parts used to make the relevant assembly (including sub assemblies unless they had their own DL) with their revision listed.

It had the same number as the top level drawing but with DL prefix (or maybe suffix, I can't recall).

You may be able to set this up in Excel (to allow find & replace) or if you have a parametric CAD (such as Solid Edge) there may even be a way to do it more or less automatically, generate a report from the top level assy or something showing revs of all parts.

It will take some time effort but it was the main tool we used for configuration control and while at the time my colleagues and I had concerns, having seen what other places do(including US defense contractors), and the end result, it wasn't that bad.

In terms of letting vendors know what has changed, how about giving them a copy of the ECO or are you ECO not that detailed?

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

RE: Subcomponent Revisions on Assembly Drawing BOM Table

What is driving this is that the Director wants to keep all of the information in one place.  While this is a good idea to try and follow, in reality it will start ballooning into a project in itself to manage.  The perceived value of having everything on the drawing is overclouding the cost in lost man hours to make changes to every drawing.

RE: Subcomponent Revisions on Assembly Drawing BOM Table

Based upon what I learned from plmguy in the past day parts do not have revisions - only drawings and documents have revisions (see thread781-215799: Drawing Revision & Part Revision). If you can convince the Director of this the whole issue goes away. Based upon the initial posting this does not seem likely to happen.

With your current system are the part revision levels the same as the drawing revision levels?
If so, the top level assembly will get a revision every time the drawing for any part used in any sub-assembly has a drawing that gets revised. This could also apply to commercial parts that do not have drawings but do have purchase specifications.

If the Director does not paying for the manhours required to make so many revisions you should point out that if customers are aware of the revision level of the product they purchase from you they will question why there are so many revisions to the product. While there are no design changes to the product it will appear to customers that you are still in the development phase and do not have a final design. If my company was purchasing a product that always had a new revision we would be likely to find an new supplier that appeared to have a stable design.


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