【转帖】1 rfcecn, multiple revisions

yang686526

1 rfc/ecn, multiple revisions
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
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none of the above.
advance a drawing revision level when that drawing, and that drawing only, is changed.  period.
it depends on how your assembly drawing bom looks.  if the bom lists revisions, then the assembly drawing should change to reflect this.  also, if fit/function of assembly is dependent on component revs (regardless of whether component revs are mentioned in bom), then the assembly drawing should be updated.
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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mintjulep, so are you saying you only put the revision on the part drawing, and do not put a revision on the assembly that is affected by that revision?  not that you are wrong, but i disagree with that practice.  our drawing packets can be anywhere from 5 sheets to 60 sheets.  if a sub-level revision is made, then the top-level is revised to note that change.  if part 1 is revised, then the assemblies that have part 1 within it are revised.   
quote:
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.
  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
i think that unless the two rev'd parts are changed in a way that modifies the form, fit, or function of the assembly or are changed in a way that they require retooling or alternate positioning within the parent assembly, that the revision of the assembly should stay the same.
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.
i agree with mechct on this.
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parts and assemblies are different, they have their own revs. part dwgs and it's part have same revs, assy dwgs and it's assy have same rev.
chris
sr. mechanical designer, cad
solidworks 05 sp3.1 / pdmworks 05
mechct, you have a good point.  we use solidworks, and pdmworks is our pdm.  i have had to check out 3 drawings in the past to update the assembly drawing revs.  if we only had to rev the part, then every drawing that has that part would be revved and updated just by checking in that 1 single part.  
i have brought that point up with qc in the past before; maybe i'll have to press that issue again.
flores
i agree with mechct
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
we have a rule that all non-interchangeable changes require a revision level change for the purpose of supply chain management.
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?
   i agree with mintjulep and mechct on this one.  the rule written out explicitly in dod-100 is that you do not revise a drawing to change form, fit or function.  any changes to the part require a new part number.  you do not call up drawing revision numbers on the parts lists.
   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.
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