parts list debate

[LONDONDERRY]

Greetings-
Perhaps you can clear up a debate I have with an ordney manufacture engineering. I created a assembly drawing with the BOM on the drawing, we lack a PDM system, and on it I have the ITEM, QTY, DESCRIPTION, MATERIAL, VENDOR columns. On the debate I have with the manufacturing eng. is he wants a revision column, and when I list fasteners on the BOM, I use the ANSi designator number, for example ANSI B18.3 - NO 4-40 X 3/8 and in the description column I list HEXAGON SOCKET HEAD CAP SCREW. But this guy wants me to list the part number in the descripion field so it looks like 4-40 X 3/8 SOCKET HEAD CAP SCREW

From my college days of drafting, REV columns are a no no and part number belong in the part number column and not redundat in the desciption fields.

who's correct?

Frank

 

[ewh]

I agree with you, REV columns should not be included in the BOM for several reasons, not the least of which is the effort that will be required to update every assembly a component is used in every time that component changes, just to change a rev letter.
As far as fasteners are concerned, I have not seen it done your way. I have seen the number column used for a mil spec number (for example) or a company specific stock number, while the description column would contain "SCREW, SOCKET HEAD CAP, #4-40 x 3/8". I guess I am not familiar with using the size and class description as a part number.

 

[ctopher]

I agree with ewh.
Leave REV off.

Chris
Systems Analyst, I.S.
SolidWorks 06 4.1/PDMWorks 06
AutoCAD 06
ctopher's home (updated 06-21-06)

 

[looslib]

Leave the REV column off the drawing.
As for description of hardware items, I have seen many different formats. At one company, they wanted the minimum description with our part number. That way if the customer needed a repalcement, they couldn't just go to True Value and buy a 1/4UNC X 1" long screw. They had to come to our distribution network and pay twice as much plus wait 24 hours for shipping.


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

Ben Loosli
Sr IS Technologist
L-3 Communications

 

[cowski]

About the rev issue - the manufacturing engineer has probably seen situations where a revision has caused the part to be incompatible with the assembly. If such a major revision is required, the part should get a new part number. Maybe some mistakes have happened and the manufacturing engineer is trying to avoid them in the future.

That said, I agree that rev number should be left off the assembly drawing. But care should be taken that the revision doesn't cause the part to be incompatible with the rest of the assembly parts.

 

[ewh]

That should be SOP - non-interchangable, new part no.

 

[cowski]

I agree completely, it SHOULD be standard operating procedure. But usually when you are in the revision process you are scrambling to get stuff done and out the door. It is an easy time to make mistakes. Sometimes unintended consequences bite you and a seemingly small change can really mess things up. Having others double check the work is very valuable.

 

[ewh]

I would think that it would be easier to make a mistake in updating rev levels in a bom than ensuring that new part numbers are assigned as needed.

 

[drawoh]

cowski,

I strongly agree about leaving REV off the parts list, however, I have lost this argument where I am. There are too many cowboys in the office. If production cannot trust engineering to not change form, fit or function, they must know the revision number of the drawings.

Ponder for a moment what happens if you must enter the revision number of your sub-assemblies.

JHG

 

[fcsuper]

Also, I'd strongly recommend investing in a PLM to maintain BOMs, change orders and MRP all at once. Under such a system, BOM's are directly under document control and should be left off the drawings altogether. ::hears shuttering engineers:: I know that idea scares some people, but the level of control offered by a PLM is far more powerful and useful than putting BOM's on drawing. yuk.

 

[ewh]

You can also omit the revision level with a good PLM.

 

[drawoh]

fcsuper,

I like leaving parts lists off of drawings anyway. Our stuff gets complicated sometimes, and a parts list with eighty to a hyndred items on it takes over even a E sized drawing. I have only one resource for providing clear pictures in the largest scale possible. The parts list on a separate piece of paper or separate computer file is a useful document on its own.

JHG

 

[KENAT]

How about using Drawing Lists and Item lists per the Def Stan?

A drawing list gives the rev level for each drawing in the relevant top level assembly.

Item list is just the Def Stan name for parts list but was usually a separate document, not on the drawing (does vary though)

Using a DL allows the package to be transferred from company to company without worrying about compatible PLM/MRP systems. However, takes a lot of discipline to keep up to date.

 

[drawoh]

KENAT,

A drawing list with revisions presents the same problem parts lists with revisions does. You have a top level assembly with a bunch of sub-assemblies. On a drawing five sub-assemblies down the tree, someone observes that "discombooberate" is misspelled on sheet_3 and they issue an ECR. You can...

...change each of five assembly drawings and parts lists down the current tree plus a bunch of assembly drawings and parts lists on other systems that use this drawing. Imagine what your top level revision block will look like when each revision, however trivial, cascades down to the root drawing.

...or you can kill them. This is unprofessional and probably violates all sorts of company HR policies.

It is easy, meaningful and useful to log the current revision level of the drawing you just fabricated or assembled to. Trying to maintain this information on your parts lists is a major pain.

JHG

 

[fcsuper]

drawoh,

Actually a partner of mine does just that with his contract work. It does work good.

 

[KENAT]

drawoh,

I worked that system for several years. I didn't say it was always easy and didn't take time. At least the drawing list being a separate document that literally just listed drawing numbers and their rev it minimized the amount of change.

Especially before parametric modelling etc: a change of a sub component drawing several layers down if it didn't cause a visual change requiring assembly drawings to be updated etc then the only other document you had to change was the Drawing List.

It isn't the same as having the rev on the parts list. This would require updating every assembly drawing up through the layers.

Only top level assemblies had Drawing Lists in the system I worked.

In fact maintaining the drawing list was how we achieved configuration control.