Large Assembly Model Management in NX

[Recon1775]

Unfortunately I know this will be a large debatable subject, but the more the merrier...
I was hoping some folks could convey their experience using NX in large assembly model management situations.
How they control the overall size (memory pull) without sacrificing the detail (BOM info, geometry display, mass properties, etc.) required at the large top assembly model.

I know there are the functions like Reference Sets and Arrangements and along those there are settings at the level of NX that would refer to those when opening an assembly.
My hope is to understand the various different processes people have come up with when managing large assemblies in NX and building those assemblies, so that various users can interact with it while keeping the memory size down so computer resources are not overwhelmed.

NX seems to have various functions to control these issues, but being a new user it's hard to see at the moment the best way to use them in tandem.

While reviewing how reference sets work I'm imagining that components can be built as a full up assembly and when assembled to the next Top Assembly those components could be reduced by building a reference set in that component which would be a simplification of it. Then at the top assembly the NX session would be set to pull those reference sets first before moving to Model or Entire part.
With that how are model mass properties carried for that component at the top level assembly. With the reference set version displayed will you get the mass properties of the full assembly or do you need to set the full model reference set before running a mass props analysis?

I've seen various folks try building representation models with underscore names to represent the full model, but that seems to break the link to the full model if they decided to cut the references back to it and now someone is creating a new model with a different name or part number, which would make for a difficult BOM structure.

Any step by step advise anyone could provide would be a blessing! Thanks!

 

[SDETERS]

look into assembly component grouping. This way when an user wants to open this huge assembly they only want open the parts associated with this area of the assembly. All other parts remain left unloaded. For Example imagine an assembly line assembly with 50 different stations. You would have 50 different assembly components groups. So a user will open the assembly and select station 1 and all of the parts would load that went into this station. All of the parts remain unloaded. Now you can load the parts if you need them.

This requires the advanced assembly licenses. But it works very nice. This does require some upkeep to the assembly

Also look into bookmarks. I do not fully understand these but I think this is more visual than anything else.

Make sure you load your assembly as lightweight also.

 

[paulbarryturner]

NX has the ability to handle very large assemblies if you follow a few rules.

Here is one approach that I have used in the past to manage assemblies with thousands of parts (up to tens of thousands). Presumably if you have many parts you have many users working on these.

Use Reference Sets, especially Model. In the part files ensure that only solid bodies are on the Model Reference Set. Then in the assemblies ensure that component parts also open on Model reference set.

Then in the Assembly Load Option turn on Partial Loading.

This approach ensures that even though you are opening many files you are not loading any of them fully because 1) none are opened as Entire Part and 2) Partial Loading only loads the lightweight version of the solid bodies.



Paul Turner
CAD & Process Engineer
Mastip Technology

 

[Recon1775]

So question on the lightweight versions.
Is the lightweight an automatically generated version of the model or does the creator of the model have to define what a lightweight version is?

The reason I ask is because I'm used to Pro-E where I had to create envelope models of the components that hung in the place of full up components, but the envelopes were linked representations of the complete assembly and they carried the complete BOM list (via work parts in the PLM system) and mass properties linked from the complete assembly model of the component. So I as thinking that's what reference sets were used for and a way to remove unnecessary features like internal components, that aren't needed at the higher assembly level.

 

[PrintScaffold]

Partial Loading only loads the lightweight version of the solid bodies.

Are you sure? Partial Loading loads part files without update info, saving about 30% of memory (as Siemens documentation claims).
What loads lightweight versions is "Use Lightweight Representations" option.

http://www.cadroad.com

 

[PrintScaffold]

The reason I ask is because I'm used to Pro-E where I had to create envelope models of the components that hung in the place of full up components, but the envelopes were linked representations of the complete assembly and they carried the complete BOM list (via work parts in the PLM system) and mass properties linked from the complete assembly model of the component.

You have set of tools in NX that do exactly that - create linked simplified representations.
What kind of representation of components you load along with your assembly does not affect the weight calculation, because weight is stored in the part file itself and is managed via reference sets and component groups.

http://www.cadroad.com

 

[Recon1775]

So the part/assembly mass props remains the same no matter what reference set is chosen for display while existing in the next higher assembly model?
That definitely would make it easy to work with.

When you create a linked Simplified representation do you assign that to a particular Reference set or does that automatically become the lightweight version based on some feature identifier?

Thank you all for your help with this!

 

[PrintScaffold]

Keep in mind that we are speaking about Advanced Weight Management: Analysis > Advanced Mass Properties > Advanced Weight Management.
Weight calculated that way is stored inside the part file and works on a principle of cache.
If you are measuring bodies directly using Analysys > Measure Bodies, it is completely different story, because, like it says, you are measutring whatever bodies you have loaded.
Back to the advanced weight management, when you calculate assembly weight, it is taken from each file and added together. This way, it does no matter what reference set you have loaded. You may exclude certain components from weight calculation using component groups. On a part level, you may exclude certain bodies from weight calculation using reference sets.
On the whole, weight management is a complex issue and is one not to be taken lightly. Study the documentation and thoroughly test your workflows. But if everything is done correctly, you will have absolutely accurate weight of the top assembly.

http://www.cadroad.com

 

[Recon1775]

Sounds good. I'll dig through the NX docs and get familiar with the two different mass props functions.

For the lightweight versions of the models, when you create a linked Simplified representation do you assign that to a particular Reference set or does that automatically become the lightweight version based on some feature identifier?