Part quantities on schematics or sub assemblies?

[draftsmandon]

Our company is making a change and I was wondering what other companies have done and some pros and cons to each way of doing this. Currently we quantify parts on the schematic BOM and also call them out on the installation or sub assembly BOM but give them a quantity of "0". For example a pump or a valve is currently quantified on the schematic BOM, but called out as an item in the installation BOM with a quantity of "0". We want to eliminate the "0" quantities and make "actual" quantities on the installation drawing BOMs and eliminate the call out on the schematic BOMs altogether. Do other companines quantify components on schematics or installations? If not on schematics, then how do you note the expected performance of a component on the schematic for design analysis and trouble shooting?

 

[MintJulep]

I've seen part quantities listed on schematics, but I've never known those Bills of Material to be the controlling documents used by purchasing.

Usually they are considered a "parts catalog" - something for the customer to use when ordering spares.

 

[MikeHalloran]

It was hard to get used to at first, but one outfit of my acquaintance put numbered balloons on the drawing field... and the bill of material _only_ in the MRP system's computer.



Mike Halloran
Pembroke Pines, FL, USA

 

[ctopher]

I agree with the others. To list as "0" and indicated how you do BOMS now is extra effort and not efficient and can be confusing to others.

Chris
SolidWorks/PDMWorks 08 2.0
AutoCAD 06/08
ctopher's home (updated 10-07-07)

 

[KENAT]

Yeah, we kind of have the opposite. Parts list (with qty) and balloons on the drawing. The schematic is typically the last sheet of the drawing and just has the components names/part numbers. There's no real link from the schematic to the parts list, for instance purely mechanical items (such as a bracket) aren't usually shown just electrical or pneumatic components/ routings etc. Where applicable the schematic, or portions of it, are indicated as reference only.

Not sure if ours is the best way, but yours definitely seems like it could be a pain.


KENAT, probably the least qualified checker you'll ever meet...

 

[ewh]

I've always seen it done in the manner KENAT uses.

Believe it if you need it or leave it if you dare. - [small]Robert Hunter[/small]

 

[MikeHalloran]

If the line printer had a relatively fresh ribbon, you got a nice printout of what you needed... and there was no possibility of phase errors between drawing and database.



Mike Halloran
Pembroke Pines, FL, USA

 

[KENAT]

So there was an 'item number' field in the MRP system, and this always matched the drawing?

If so what MRP system, cause ours, at least the way we use it, don't accomplish anything near this.

KENAT, probably the least qualified checker you'll ever meet...

 

[MikeHalloran]

Right; the MRP system knew the item number, the drawing number, and the revision level, and could spit out flat or indented b/ms, wire lists, whatever you wanted.

It ran on an AS/400, and may have been slightly customized for us, but I had the impression that it was basically a commercial product. Unfortunately, I don't know who sold it or what it was called. I'm pretty sure it's been replaced with something graphical, and slower. It was state of the art, 20 years ago.

I thought all the AS/400s had been discarded as junk a decade ago, but at my new job, we have one that is treated with great reverence, for reasons that elude me. The software we're using was apparently patched and adapted from some old POS software

( I mean that both ways, one much more strongly. I don't think I have ever seen an uglier or more bug-ridden kluge anywhere, and I have used and written a lot of ugly kluges. )



Mike Halloran
Pembroke Pines, FL, USA

 

[KENAT]

Our MRP (Stops All Production) can do the BOMs etc but not with item number. It has part/drawing number, rev, description etc but not item number.

Given that our CAD will automatically change the item number depending how you sort the parts list/as you add or delete items I don't see how our MRP could easily keep up, especially as we have no PDM/PLM or real config control discipline.

KENAT, probably the least qualified checker you'll ever meet...

 

[fcsuper]

Three companies I've worked at placed all control of the BOMs in the PLM ([un]Agile or customized MGF/Pro). To avoid double specification (in order to decrease the chance of error between two separate systems that have the same information), no drawings are allowed on BOMs on them. I've gone from being leary of this to now considering this method to be superior, at least from an enterprise-wide perspective.

Matt Lorono
CAD Engineer/ECN Analyst
Silicon Valley, CA
Lorono's SolidWorks Resources
Co-moderator of Solidworks Yahoo! Group
and Mechnical.Engineering Yahoo! Group

 

[draftsmandon]

fcsuper,

Are you saying that none of the drawings have BOMs?

We order parts directly from the drawings so what ever is on the BOM goes into our purchasing system. This is the reason that we would call out parts on all drawings with references, or "0" quantities on some drawings, and hard quantities on another.

Mintjulep's system seems to call out items on the schematic BOMs, but these are not fed into the purchasing system for order. That wouldn't work for our system since every drawing goes into our purchasing system.

Kenat's system seems to be similar to Mintjulep's but when you say "just has the components names/part numbers" do you mean in note form or what?

Our system may be closer to MikeHolloran's except that our drawing's have BOMs and they get fed into the purchasing system exactly as entered.

Thanks for all of the comments, more comments are appreciated. If I'm hearing everyone correctly, it sounds like we are making a smart move to quantify materials on only one drawing.

 

[KENAT]

"just has the components names/part numbers" On the schematic where the component/cable is shown I suppose you'd call it a note but in practice it's just written next to the 'block' or 'line' representing the part.

I'm not sure if we're really standardized on how it's done. Just looked at one and all the cables just have PN with the designator/identifier (e.g. for the connectors J1, J2, J3 etc)at each end and in some cases the name (or part of it) is given at one end next to the designator. Most of the parts being connected only have their name/description not PN.

However, I wouldn't necessarily follow this exact method as best practice. Drawings were a mess when I first started here a couple of years ago and we haven't yet addressed all areas, cable schematics being low on the list.

Just realized, you're talking about 'installations'. We build actual machines and have more or less complete drawings of all assemblys (at least in theory) so what I put may not directly apply to your situation.

KENAT, probably the least qualified checker you'll ever meet...

 

[fcsuper]

Yes, under the systems I've been in, NO drawings have BOMs (except inseparable assemblies, but those do not refer to any parts off the drawing). All application data in controlled by the PLM. Purchasing relies on this. When they send out an assembly, they automatically attach the BOM from the PLM.

Matt Lorono
CAD Engineer/ECN Analyst
Silicon Valley, CA
Lorono's SolidWorks Resources
Co-moderator of Solidworks Yahoo! Group
and Mechnical.Engineering Yahoo! Group