Revision Control

[snow1440xx]

Question hoping someone can help me with.

I have an assembly. Say one component of the assembly I revised the drawing and added 1" length to it. This component is shown in the assembly drawing. Do I need to REVISE the assembly drawing OR just edit it and update that component to the correct length with out a revision since it does not affect form fit or function?
I've always revised every drawing no matter what, but a colleague disagrees. What would be the reasoning behind it?
Thanks

 

[ewh]

IMO, if you change the assembly drawing in this manner, it should definitely be revised, as it is affecting form. A good PDM system would force you to do so.

 

[Heckler]

Does it change Fit, Form or Function (F^3) of the assembly? I think you already know the answer to that question.....I would revise the assembly drawing.

Best Regards,

Heckler
Sr. Mechanical Engineer
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Never argue with an idiot. They'll bring you down to their level and beat you with experience every time.

 

[drawoh]

snow1440xx,

If the one inch added to your component affects the form, fit and function of the assembly, do not revise the assembly. Save the results as a new assembly.

JHG

 

[MintJulep]

What exactly do you think that "form" means?

You changed the length of a part, you changed its form.

NEVER change a drawing without changing the rev level. NEVER.

 

[snow1440xx]

yea I realized after I posted it does affect form, prob fit too in my situation.
thanks for the replies..

 

[ctopher]

I do as the others.

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

 

[needahandle]

The answers are (of course) correct, however reality has a way of creeping in....

We design vehicles with ~30k individual components, and assembly levels up to 50 deep. If we followed this rule to the letter, we would be revising the top-most numbers several times a day. With the high cost of changes (fielded vehicles, customer approval, etc.), we have business rules that limit us from going 'up the tree'. Our PDM makes sure we always have the latest versions loaded while we are working, and any time we revise an assembly, we 'catch-up' all of the view updates that have taken place. Obviously a component part number change must be reflected in an assembly immediately (or it didn't change, did it?).

 

[ewh]

Many companies cover themselves in this situation by issuing change orders that are not necessarily incorporated until enough have accumulated. Copies are attached to the drawings affected whenever those drawings are issued. To blindly change assemblies with no means of tracking the change is asking for problems down the road.

 

[KENAT]

This can vary slightly depending on if you are doing just 2D or if you have some kind of parametric 3D modelling system.

Certainly I would think just changing it without going up a rev is incorrect in either case and would get you a slap on the wrist from configuration control.

Back when working 2D we'd only actually update the assembly drawing if you could see the difference in the views. ie a lot of the time if we just changed say a washer thickness or length of fastener or the material of a part then we wouldn't update the Assembly drawing itself. We would however update the separate parts list for hardware or the drawing list (which listed the revs of all the different drawings in the pack) for drawn items.

For parametric 3D depending how you have it set up you may not have a choice but to update it there and then or wait untill you have several changes and do it then relying on some kind of advance change control process till you get to incorporate it (as ewh).

I think others have covered this but from what I've seen/know usually revision is for a change not affecting form, fit, function etc. If these are changed and typically the part is no longer both forward and backward compatible then a new part number is normally given (sometimes a - number). In your case sounds like the piece part should be a new number but depending how your assembly goes together it may only be a rev. But looks like you realised this on your second post.

 

[drawoh]

needahandle,

If you are designing vehicles with 30K+ parts and a depth of fifty assembly levels, you need to follow the rules above.

The whole point of not changing form fit and function is that revisions do not affect subsequent levels of assembly. You can correct drawing errors, fix assembly problems, reduce cost and make things more reliable, and not affect the next parts list down.

When you do affect the assemblies further down the tree, the trickle effect stops when you hit an assembly whose form fit and function is not affected.

JHG

 

[mechgunner]

I think drawoh hit the spot, a change to fit, form or function means a PART number change not a rev change, rev changes are normally made to track any small changes to ensure traceability.

A clean house is a sign of a broken computer.

 

[ctopher]

I also agree.

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

 

[MechNorth]

Yup. Me too.



Jim Sykes, P.Eng, GDTP-S
Profile Services
CAD-Documentation-GD&T-Product Development

http://www.profileservices.ca

 

[ImnotfromMars]

How does the person bulding the assembly know to use the 1" longer component?

Robert

 

[ctopher]

It could be listed as optional on the BOM, or listed on a separate assy.

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

 

[mechgunner]

ImnotfromMars

This is why revision and part number change control need to follow SOPs, the new (possibly) part that is an inch longer will have a different component part number than the original, the extra inch also affects the fit form function of the final assembly so this should take a new part number.

If a new part number is generated than a new BoM for that assembly part number would also be generated, thus calling for the correct component (1 inch longer).

As stated by ewh, you can use temporary documentation (ECN ECO deviation etc) to attach to the original BoM, this tells planning etc to call for the new component.


A clean house is a sign of a broken computer.