revision standards - change of a BOM that is not shown on a print

[rmetzger]

We have a number of older assembly prints that do not list a BOM on the print (listing the BOM for ease of visibility is our current standard) but instead track the BOM in software unrelated to the CAD system. It is our understanding that if the BOM changes for an assembly, the revision of its controlling drawing should change even though the BOM is not listed on the drawing itself (the BOM change noted in the rev block). Is this thinking correct and if so / not can someone point me to the standard where it may be listed?

thanks

 

[KENAT]

Do you work to ASME?

ASME Y14.35M may have something as it is "Revision of Engineering Drawing And Associate Documents", ASME Y14.34M-1996 "Associated Lists" might have some guidance too.

Associated documents need not be revised for the sole purpose of maintaining a common revision level

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[dgallup]

We do not put BoM's on most of our assembly drawings because they are for families of parts. The differences between instances are so minute you could never see it on the drawings anyways. The Bom's are all kept in an antique green screen MRP system that does not link to anything. We do not revise the drawings when one of the BoM's changes.

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[ctopher]

We show BOM's on drawing for tooling and if a customer requires it per contract.
Otherwise, it's separate. Either way we don't show revs of each part on the BOM (unless it's configuration controlled by the customer).

Chris, CSWA
SolidWorks '15
SolidWorks Legion

 

[rmetzger]

dgallup,

How are the approvals for the BOM changes managed; is this part of your MRP system? Our system requires documentation of approvals for changes indicating that they have been reviewed and approved by engineering and quality; this takes place via electronic signatures on prints. Short of a print change, there is no evidence of the change approval having taken place (via our system).

 

[dgallup]

We have an electronic ECR system but it has no actual connection to the MRP or CAD systems, it depends on people doing what they say they did. So engineering has to approve the change but then some one has to go in and manually change the ERP system. Not the best approach nor one I would recommend but we have a lot of unrelated product lines that came from different places designed in different CAD systems and the MRP system from hell so no one has ever suggested trying to link all these systems.

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[jassco]

Hi, rmetzger:

Below are my two comments:

1. Definition of your current print is incomplete if you don't have a BOM for an assembly drawing;
2. You can't change the "BOM" if it does not exist in your drawing.

But you can do whatever you want to do since it appears that you do not follow any standards. I think it is mandatory to have a design BOM for an assembly. You can have a different manufacturing BOM, but the design BOM should be on the print.

For your revision, I think you need to do the followings:

1. Add missing BOM;
2. List actual changes to the BOM.

Best regards,

Alex

 

[KENAT]

jassco, per ASME stds, and the standards I used to work to in the UK having a separate Parts List or Item List is allowed.

It is not mandatory for this information to be on the assembly drawing itself.

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[jassco]

Hi, KENAT:

If you make a BOM of an assembly as a separate list, then the list is considered an associated document.

One can't change a BOM on a print document if the BOM does not reside on the print in the first place.

Best regards,

Alex

 

[ctopher]

KENAT is correct.
You have the option to show the BOM on the drawing, or have it as a separate doc (PL or BOM).

Chris, CSWA
SolidWorks '15
SolidWorks Legion

 

[KENAT]

jassco, maybe I misunderstood either you or the OP.

(b)separate parts list: a parts list prepared as a document separate from the engineering drawing to which it is associated and one that may be revised independently of the drawings. See Figs. 10A and 10.

Figure 10 A is a separate parts list, figure 10 B is a print from 'Digital Data' i.e. ERP system.

Posting guidelines faq731-376

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(probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​

 

[jassco]

Yes, if OP makes his BOM a separate BOM, then he needs to revise BOM document. He can't revise his assembly drawing as there is nothing to revise on that drawing.

Best regards,

Alex

 

[ctopher]

jassco,
I agree. I also misread your previous statement.

Chris, CSWA
SolidWorks '15
SolidWorks Legion

 

[MikeHalloran]

Actually, where BOM is independent of ďrawing, it would make sense to maintain a revision level for the drawing alone, and to reference it in the separate BOM.

Mike Halloran
Pembroke Pines, FL, USA

 

[dgallup]

That is not very efficient as there can be many drawing revisions that have no effect on the BoM. Revising the BoM just because a drawing issue level changed is a lot of extra work.

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[KENAT]

Back in days of yore, in the UK the MOD system I worked to used separate Item Lists & Assembly Drawings. The revision of each was recorded on the 'Drawing List' for the product. Only high level assemblies typically had their own drawing list, so the drawing list contained rev level for all assy drawings, item lists & piece part drawings.

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(probably not aimed specifically at you)
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[tbuelna]

The use of SPL's is common. And as the relevant sections of the ASME Y14 standards noted by KENAT describe, it is not necessary in every situation to issue a drawing revision when a change is made to an SPL. ECNs can be published that affect only the SPL and nothing contained on the drawing itself. But that does not mean the data defined in the SPL, along with any outstanding ECN's, can conflict with what is described on the drawing. In every case, the drawing and SPL, along with any un-incorporated ECN's, must be in full agreement.