BS Standard - correct approach for sheetmetal assembly drawing?

[marvincooper]

Can anyone tell me, is there a BS standard for the layout of sheetmetal assemblies?

I have always treated a welded assembly, or a sheetmetal + studs/rivet nuts assembly, as the same as any other type of assembly. I would show an exploded view, projections and a BOM with balloons.

I recently presented this type of drawing to a new client and was told to remove the exploded view and treat the welded assy as a part. This meant I had to show and dimension separate parts all on the assembly views in their assembled state. While this has reduced the number of separate drawings (their justification), it has decreased clarity and I wonder if it breaches any ISO standard? They claim to be hot on standards (BS:8888) so it would be good to make sure I am not going against the book.


Any advice appreciated.
Thanks
Marv.

 

[KENAT]

BS8888 is the compendium for all the relevant iso drawing standards so if specified, it should probably be in there.

Exploded views traditionally weren't often used, and arguably don't meet the requirements for assembly drawings in the US as they don't show the assy in the 'finished orientation'. I vaguely recall similar at my last place in the UK but not sure which spec if any said it.

As to the welded assy, at my place in the UK they were normally treated similarly to any other type of assy. One exception being that I seem to recall for lengths of stock tube or similar they may not have unique drawings and instead be specified on the item (parts) list, with additional info on the drawing if need be.

The customers approach may be legitimate however, essentially a detailed/inseperable assembly. Do they still put a item/parts list with it?

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[marvincooper]

I have a copy of BS8888 and it mentions assembly drawings but does not define when an assembly drawing should be used. I had always assumed that anything comprising more than one constituent part would be an assembly. I have only just heard the term "inseperable assembly" and don't know if this is a valid term when working within BS8888.

The customers's example drawings that I have seen don't seem to conform to any standard and do not have parts lists for sheetmetal assemblies.

To my mind it is simpler and less open to interpretation and error to treat all assemblies, inseperable or otherwise, as just that - assemblies. With a BOM, and seperate drawings or drawing sheets for each constituent part.

My approach has been to have seperate drawing sheets for each part, so that separate drawing numbers are not required for parts that only exisit within the context of a welded assy.

My concern is that neither I nor my client can point to a standard and say with confidence that there is a correct approach.

If there is no standard covering this issue then i am happy to go with whatever my clent wants, I am just worried at the moment that they might beat me up in the future for not following a standard.

 

[marvincooper]

I just looked at BS8888 again and the only relevant reference I can find is in section 5.3 regarding Combined Drawings.

It states that:

"A combined drawing should display an assembly, item list and constituent details, drawn seperately but all on the same drawing."

I guess this covers inseperable assemblies, what do you think? It depends on your definition of the word "assembly".

 

[KENAT]

The one thing that's throwing me is the parts list, even an inseparable assembly that's fully detailed on one drawing should still I think have a parts/item list.

I just looked at the relevant US document ASME Y14.24-1999 and for an inseparable assembly (which is essentially what it sounds like they want to do) it doesn't explicitly say it has to have a parts list, although the example drawing has reference to a separate parts list.

So, at least to US stds, what they are proposing may be legal - so long as they do it properly. In the US system individual pieces may be detailed in the assembled state, have unique identifiers and a few other things.

However, the section you found of BS8888 seems to explicitly state you must detail the parts individually - even if on the same drawing - and that you must have an item list.

Unless there is mention elsewhere of 'inseparable assemblies' or equivalent, then it would appear your customer is not following BS8888 to the letter.

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