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Item numbers on Assembly Drawings

Question asked by Pete Yodis on Oct 2, 2013
Latest reply on Oct 29, 2014 by Brian McEwen

I am throwing this out there for discussion....  This is related to whether you show BOMs on Drawings and how you manage your BOMs with ERP and Drawings (and there could be implications with EPDM).  I am interested in hearing what other folks do...


A little history on ourselves -  We moved away from showing the BOMs on assembly drawings about 7-8 years ago to reduce the amount of double entry for our designers managing a BOM table on drawings and a BOM in ERP.  I was not completely on board with the implementation, because SolidWorks implications were not being fully considered.  Most of the struggle atht he time was with editing tables in AutoCAD and then re-entering the data in ERP.  As a result, on all of our drawings we now just show the item number and do not show a BOM table.  The item number shown on the drawing has to match the Item number in ERP.  This gets "fun" for larger SolidWorks assembly drawings that go through multiple changes.  We have developed methods for keeping the Item numbers the same between ERP and SolidWorks assembly drawings.  As a trend, a single source of BOM is where companies are headed and keeping that master BOM in ERP seems like the best place for it to reside when you have CAD and ERP.  Frank B. Watts in his book, Engineering Documentation Control Handbook (2nd edition), agrees with an approach like this as a company grows and shows the trend in the future will be toward this method of a single BOM being mainatined in ERP (or PLM/PDM linked to ERP if you like).  I would agree with that approach, but it still makes item number management in SolidWorks drawings a pain. 


This got me thinking about item numbers on drawings in general.  What is the point... It seems to be just a pointer to get you to some other controlled table so that you can find a unique identifier (part number)... hmmm seems to be jumping around a little bit and creating an extra step.  As part of the work order packet our production folks here print the BOM from ERP and print the drawing for assembly builds on the shop floor.  The assembly folks look at the drawing and find the ballooned item number, only to then look on the BOM and find that item number so they can get a part number.  The item numbers seem like the extra step... It seems to me that maybe item numbers are a carry over from a bygone era when drawings were hand drawn and BOMs were maintained on drawings.  Item numbers allowed easier changes to the BOM table without editing the drawing (when it was tedious to do by hand drawing).  Is there really a need for item numbers in a modern world?


I am currently thinking out (with other's help here) why it wouldn't make sense just to show the part number of ballooned items on an assembly drawing and not the item number.  This would be much more efficient than having to consult another piece of information just to get what you are looking for.  Our assemblers would just see that unique identifier (part number) right on the drawing next to the item they are looking for.  I would advocate that the BOM in ERP be sorted to be in numberical order for easy reading and description location once the part number is seen on the drawing... or do show the BOM table on a SolidWorks drawing, but show it without item numbers and sorted by part number numerically.  This seems more efficient to me and would make looking at SolidWorks assembly drawing a nice thing.  Plus, we wouldn't have to go through the rigamarole of making item numbers match.


Does anyone operate this way?  Can they see flaws with this approach?  Are item numbers really needed?  Let me know if I need to clarify.


Thanks in Advance