Reference sets in NX 7.5 1

[NL8]

Has anybody come across the problem the reference sets used for parts in an assembly are different from one parent refrence set to the next. I just dropped an assembly into a nother assembly, constrained as needed, then realized that I wanted the Model refernce set instead of the Entire Part reference set. When I made the change the parts inside the assembly I was changing randomly decided to change their own reference sets. My coworkers tell me that this is not uncommon and that the fix is to reset the part reference sets in context with the top level assembly. But when you start talking hundreds of parts this gets beyond tedious. Ideas?

Joe Hasik, CSWP

 

[JohnRBaker]

This is just ANOTHER reason why we have always recommended that you avoid, whenever absolutely possible, the creation of Reference Sets in an Assembly file.

Reference Sets act as 'filters' and were never really intended to be used to 'filter' anything other than the objects which you would normally find when creating the models which represent your 'piece parts'. This was a scheme which would allow you to hide everything except that 'piece part' model when this item was to be used as a 'finished' part in your Product model, or Assembly. Therefore if you create a 'Model' Reference Set in an Assembly and then use that Reference Set when you add this Assembly as a Component (i.e. as a sub-assembly) in the next higher assembly, only those Components which you explicitly included (and however THEY were defined, Reference Set wise) that is how it will be seen at that next level up Assembly. If you had NOT created Reference Sets in what were Assembly files or if you had only used the 'Entire Part' Reference Set when adding these Assemblies as Components to higher level Assemblies, there would be NO surprises now in what was or what was not expected to be included in your final Assembly.

John R. Baker, P.E.
Product 'Evangelist'
Product Design Solutions
Siemens PLM Software Inc.
Industry Sector
Cypress, CA

http://www.siemens.com/plm

http://www.plmworld.org/museum/

To an Engineer, the glass is twice as big as it needs to be.

 

[looslib]

Unless you have strict guidelines on what is in reference sets AND a strict naming convention, reference sets at the assembly level will cause problems like you encountered. You also have mating conditions which are tied to the geometry/planes in a reference set that chnage when you replace a reference set in an assembly.
Reference sets were originally used to filter out construction geometry back in the wireframe days so you would only get your finished part entities in your assembly. When UG moved to solid modeling, we (old users) continued to use reference sets to filter out things we didn't want at the assembly level. As the development team got smarter, they realized that some things aren't needed at the assembly level and so the 'entire part' reference set automatically excluded them, like datum planes and axis.
I have always had a hard time getting the designers I work with to use a standard naming convention for reference sets and not go creating any named sets they want. It really blew up at my last company where we decided to enforce the corporate standards and all of a sudden assemblies were failing to open with the proper components. Once they understood what was going on, things straightened out, but I did spend a few weeks 'repairing' released assemblies.
I try to use 2 reference sets. One is named MODEL, which can now be created automacilly by the system consisting of only the solid geometry. Entire Part and Model ususally contain the same pieces. The second one I like is called DATUM which has the same geometry of the MODEL plus any datums needed to mate the assembly to the next higher level. There is now, I believe, a simplified reference set that is or can be created automtically, too.


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

Ben Loosli

 

[rc0213]

If you have a large assembly, a suggestion is to create subassemblies, and then only add the subassemblies' reference sets you want to show at top assembly. So, my suggestion is start using subassemblies and try to set up the process as the manufacturing floor would do it for your company.

But, that is tedious, not as tedious as doing it all at the top assembly like you are trying to do. You do not want to create an edited assembly, that creates issues as the others have mentioned.

An example of when you might want to create new reference sets are like in automotives and you do articulation of a part, you show it in different positions under a few situations.

 

[looslib]

Showing the same part in the same 'place', but orientated differently would be what arrangements are for, not reference sets.
Reference sets are for excluding things at the assembly level of items in the component file.
If you are doing this with reference sets, then you have to have multiple orientations of copied geometry at the component level for each reference set. YUCK!

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

Ben Loosli

 

[JohnRBaker]

Ben is right, if you're using Reference Sets to create different configurations of the same sub-assembly of parts you are creating a lot of extra work for yourself which will haunt you for years everything time someone opens this assembly, both in terms of the extra complexity which will have to be managed and which could result in what to the user will appear to be unpredictable behavior or mistakes in your files. Also this could result in more memory being required to open your assembly than would normally be the case as parts are being duplicated unnecessarily.

Note an arrangement can be used to control both the content and position of components in a sub-assembly is the recommended way to define variations of a single sub-assembly which may need to be used in several different configurations. Reference Sets are NOT recommended for this type of task. They should be limited to ONLY those parts where actual geometry is being created, NOT where piece parts are being 'assembled' into sub-assemblies which will then be added to a larger product model assembly.

John R. Baker, P.E.
Product 'Evangelist'
Product Design Solutions
Siemens PLM Software Inc.
Industry Sector
Cypress, CA

http://www.siemens.com/plm

http://www.plmworld.org/museum/

To an Engineer, the glass is twice as big as it needs to be.