1 RFC/ECN, multiple revisions
1 RFC/ECN, multiple revisions
(OP)
Let's say there are 2 revisions that need to be made in a sub-assembly on 2 different parts, should there be 2 top-level revision numbers or just one to reflect the part-level revisions? Hopefully that wasn't too confusing, so here is an example:
Scenario 1
Assembly Rev. B (notice Rev)
Part 1 Rev. A
Part 2 Rev. A
OR
Scenario 2
Assembly Rev. A (notice Rev)
Part 1 Rev. A
Part 2 Rev. A
I would believe that if Part 1 and Part 2 are on the same ECN/RFC, then the top-level revision should be Rev A, just tell them to see the affected ECN/RFC. Another here believes that for each part that is revised, the top level Rev should be the next consecutive Rev.
Note that this scenario is only if there are multiple revisions on the same day, at the same time. I know it would be different if a revision was made to a part, and later on another revision was made to another part.
Flores
Scenario 1
Assembly Rev. B (notice Rev)
Part 1 Rev. A
Part 2 Rev. A
OR
Scenario 2
Assembly Rev. A (notice Rev)
Part 1 Rev. A
Part 2 Rev. A
I would believe that if Part 1 and Part 2 are on the same ECN/RFC, then the top-level revision should be Rev A, just tell them to see the affected ECN/RFC. Another here believes that for each part that is revised, the top level Rev should be the next consecutive Rev.
Note that this scenario is only if there are multiple revisions on the same day, at the same time. I know it would be different if a revision was made to a part, and later on another revision was made to another part.
Flores





RE: 1 RFC/ECN, multiple revisions
Advance a drawing revision level when that drawing, and that drawing only, is changed. Period.
RE: 1 RFC/ECN, multiple revisions
If multiple components change, the assembly is still revised only one level, so long as all revised components are noted as changed. The assembly is changing one time.
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RE: 1 RFC/ECN, multiple revisions
That's the way I am used to, but our QC believes otherwise. The BOM's do not have a Rev field in it, but our titleblocks do.
Flores
RE: 1 RFC/ECN, multiple revisions
Look at it this way... If you have a part that changes slightly (thus bumping the rev on that part) and it's used on 172 different assemblies are you going to go and rev each one of those assemblies? I wouldn't. Unless it was a major change that would affect how those assemblies were used or how other parts within those assemblies were used.
RE: 1 RFC/ECN, multiple revisions
"I think there is a world market for maybe five computers."
Thomas Watson, chairman of IBM, 1943.
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RE: 1 RFC/ECN, multiple revisions
Chris
Sr. Mechanical Designer, CAD
SolidWorks 05 SP3.1 / PDMWorks 05
ctopher's home site (updated 06-21-05)
FAQ559-1100
FAQ559-716
RE: 1 RFC/ECN, multiple revisions
I have brought that point up with QC in the past before; maybe I'll have to press that issue again.
Flores
RE: 1 RFC/ECN, multiple revisions
No reason to rev an assy if a part changes, unless it is a notable design change shown in the assy.
Chris
Sr. Mechanical Designer, CAD
SolidWorks 05 SP3.1 / PDMWorks 05
ctopher's home site (updated 06-21-05)
FAQ559-1100
FAQ559-716
RE: 1 RFC/ECN, multiple revisions
Definitions:
Non-Interchangeable means for one reason or another (physical incompatibility, differences in performance or durability, internal differences in serviceable components, cosmetic appearance or simply for follow-up purposes) the revised and existing versions cannot be mixed and unique identification is required.
Interchangeable means that stock of the revised part can be mixed with existing stock of the same part and that either version can be used indiscriminately for production and/or service.
Are the top assemblies Interchangeable per the definition above?
RE: 1 RFC/ECN, multiple revisions
The consequence of this policy is that a revision correcting a spelling mistake on a fabrication drawing has no effect on the next assembly.
A change to form, fit and function affects the part number on the assembly drawing, and consequently, triggers a revision.
JHG
RE: 1 RFC/ECN, multiple revisions
On another part, a 14 ga. sheetmetal part flexed under weight, so we are bumping it up to 12 ga. Even though the part is interchangeable, because of liability issues we couldn't use the thinner gauge.
Flores
RE: 1 RFC/ECN, multiple revisions
One of our last product packages has something like 500+ sheets. Many of them share parts. I'd hate to "change" all those drawings, if one part "rev'd up"...
Wes C.
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RE: 1 RFC/ECN, multiple revisions
There was one other aspect to your question.
If I am making two unrelated changes to an assembly at the same time, I do one revision. It will call up both ECN/ECO/ECR numbers. My assumption is that no assemblies will be manufactured with one change and not the other.
This might be affected by the way your PLM software works, and there might be a company policy at your end.
JHG
RE: 1 RFC/ECN, multiple revisions
One is to carry a revision level to the part/assy. The revision level is tracked for each part. One can rev up a part (due to form, fit, function) and the assy would stay at the same rev level. The configuration of the assy is tracked thru the planning department. The engineer must disposition existing parts and their assy (ie: scrap rework, etc). A spelling type error would rev up the drawing sheet but the parts/assy does not change. This system is great for engineers because it cuts back on the paperwork.
The other system is one more widely used (my opinion). This system adds a dash number if a form, fit, function change is made. This forces the engineer to rev up the assy by making another assy dash number. This system causes more paperwork for the engineer, but it controls the configuration better (my opinion).
The big question is what is form, fit, function. This is a debatable subject for many part/assy changes. Perhaps someone can help shed some light on this?
Hopefully this makes sense.
RE: 1 RFC/ECN, multiple revisions
No, I'm saying that if a drawing changes, you advance its rev.
If a part drawing changes, advance its rev.
If the change to that part drawing forces a change in an assembly drawing, advance the assembly drawing's rev.
If two part drawings (of the same assembly) change, advance each drawings rev.
If the changes to those two parts force a change in their associated assembly drawing, advance the assembly drawing's rev by one. The assembly drawing only changed once.
Not all changes to a part force the assembly drawing to change. For example, a change of material or plating without any dimensional changes would likely not reqire an assembly drawing change (unless your BOM lists such details), as the change is essentially "invisible" to the assembly drawing's purpose in life - which is to show how to put things together.
A change of a part dimension most likely will force a change in the assembly drawing.