BoM Hierarchy and Hardware 2

[scrototee]

Hello,

My company is currently consolidating scattered CAD data into SolidWorks WPDM.
With this, arises an opportunity to organize the Feature Trees into multi-level BoMs which export into our ERP system.

There is hardware that bolts one sub-assembly to another.
Question is, is it appropriate for this hardware to appear at the top-level assembly? Or should the hardware 'belong' to one of the subassemblies?
The complication is that we require assembly documents for sub-assemblies, which would then require descriptions of features that are out of scope.

Thanks,
scrototee

 

[KENAT]

What drawing standards do you work to - not that most have much detail on assy drawings.

Generally the hardware should be specified at the assembly level at which it is used.

If "subassembly B" is mounted to "subassembly C" to create "assembly A" by 5X M5*20 Phillips Pan Head Screws then those screws should be in the parts list for assembly A.

From what I've seen rarely does anything good come from having loose hardware - or for that matter hardware that has to be removed and then reinstalled at the next assy level - as part of subassembly.

(Kits are another matter, upgrade or replacement kits etc. may well logically consist of the relevant sub assy plus mounting hardware plus a few spares of the mounting hardware.)

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[scrototee]

Of the few loosely implemented standards, we ansi y14.5M, which as you know, only specifies gd&t and such. I would like to see what y14.100 can offer.

I agree with 'subassy B' mates with 'subassy C' to create 'assy a' which contains the hardware under 'assy a'
However, with our instruments, it would be:
'Sub A', 'Sub B', 'Sub C', 'Sub D', ... , 'Sub n'
bolt together to make top-level 'Assembly K'

There is an awful lot of hardware / brackets / misc machined parts that report to the top-level node of the assembly.
Have you seen this to be a successful way of doing this?

 

[ewh]

They make airplanes that way...

“Know the rules well, so you can break them effectively.”
-Dalai Lama XIV

 

[KENAT]

If I understand you correctly it's the only successful way I've seen of doing this.

As ewh implies certainly most drawing packages for military equipment in the US & UK gets done that way.

You could of course introduce intermediary levels of assy, but I know ERP fans and the like are obsessed with flat BOM structures. However it can be easier to document things this way.

Posting guidelines faq731-376

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

 

[ewh]

There is an awful lot of hardware / brackets / misc machined parts that report to the top-level node of the assembly.

Yes, top level assemblies can be very complex. Not everything lends itself to modular build. This hardware will still need to be referenced in the assy into which it goes, regardless of where in the BOM hierarchy it is located, so you may as well help out the assemblers and specify it where it is used.
As KENAT notes, it seldom works well having loose hardware travel around with a part.

“Know the rules well, so you can break them effectively.”
-Dalai Lama XIV