Defeaturing 2

[marine59]

In a 3D solid model assembled of 3D parts mated with random locations of Global and Work coordinate systems:

is there a
1) straight-forward
OR
2) POSSIBLE

method to get rid of "blends"
"fillets"
"chamfers"
"mates"

installed by a well-meaning but non_FEA_knowledgeable designer?

 

[JohnRBaker]

I don't see how Assembly Mates would be an issue since they are not geometric and can easily be deleted/supressed. As for minor features which will only make your meshes more complex than they need to be, you can use Simplify Body to remove topology (if you're using NX 5.0.2.2, Delete Face replaces Simiplify Body) if they are features that can be deleted/supressed.


John R. Baker, P.E.
Product 'Evangelist'
NX Product Line
SIEMENS PLM Software Inc.
Cypress, CA

http://www.siemens.com/plm

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

 

[marine59]

If your goal were to:
modify (defeature, remove blends, convert solid==>sheet bodies, hide unnecessary complexities) an assembly of .prts for ANSYS meshing it is much more convenient to

1) modify each part singly
2) import it FROM ANSYS (on top of previous parts)
3) create a component with a name
4) hide it in ANSYS with the others
5) leave behind solids which will be modeled as shells, bars, masses, ....
6) mesh each component (transferred .prt) separately
7) connect as/where necessary

which doesn't work, because the parts were created with part-significant coordinate systems and mated in shifted, rotated positions (which COULD have been done as translations, etc BEFORE assembly) and the process above brings them all in as if the Absolute CS's were the same.

Mating creates an orientation which must be replicated by translations, rotations before suppressing = deleting the mates in the assembly.

The alternative is the much slower, messier process of importing/exporting the parts as an assembly, (now undifferentiated parts). This preserves the orientations of the mates as long as the surfaces... are still there. The parts arrive at the ANSYS end as a semiconnected and unidentified set of volumes (not if sheet bodies), areas, lines, and points. For the meshing to make sense, the stuff must be re-assembled into components manually.

You can't take out the mates without re-positioning & re-orienting each mated part to the common ACS.
Having the mates prevents individual part export/import.

Big,Big difference in prep and meshing time.

Gerry Starkeson
UG2-UG16 ...... NX4

 

[cowski]

You could export all the parts you need for analysis to a parasolid file. When you import the parasolid file to a new UG file, all the parts will be at the assembled location. Defeature your parts individually before you do this as you won't have features to suppress/unsupress in the parasolid form.

If it fits your workflow better, you could also export the parts individually from the assembly. When you reassemble the parts they will all be in assembly position.

There is also a trick to fairly easily reposition the part to the assembled position, but is a bit more involved and may cause problems if the part is used in different positions in multiple assemblies. I can pass that along if you are interested.

 

[marine59]

Thanks very much, cowski.

...export...parts...need for analysis to a parasolid file
*Been there, done that, didn't work:
*access to parasolids locked out for 2 weeks (newbieacct)
*parasolids created would not import into ANSYS ????
don't have time this week to work on parasolids

...could also export parts individually from the assembly. When you reassemble the parts they will all be in assembly position....
If you mean parasolid parts, I can't (now)see above
If you mean parasolid parts imported to "new UG file"
I'll try it now

****trick to fairly easily reposition:

I haven't found one; I'm interested in your "trick"
I don't have any multi-use UG parts remaining
(point masses, bars/links for fasteners)
Thanks,
Gerry Starkeson
shakily straddling the UG16 - NX4 gap

 

[cowski]

As for the repositioning components see thread561-139588 Hellbent's first post gives the procedure. Also there is some good discussion on the pros and cons of doing this.

 

[hudson888]

I thought that this had been asked and answered about half way through. The steps to do what you want are many, but easy and straightforward. To some extent though it has to be said that if models aren't designed for simplicity and ease of analysis then some work will have to be done. There is no substitute for communicating your needs to the designers in advance.

1. It is likely that in the majority of cases you would do well to defeature by suppressing blends in the individual components. It will just be quicker that way. In some models it may be convenient to simply wind back the model (using "make current feature") to a point before the blends are applied.

2. Another way to defeature that may be on a par with supressing the blends would be to use simplify body.

3. Without knowing your situation it bears mentioning that NX has a quite useful midsurface function that may provide more suitable geometry to mesh for sheet metal or other thin shelled type structures.

4. If you must risk editing the models in an assembly then why not clone the assembly first. Look under Assemblies>Cloning. F1 for help. I'd definitely use this in the situation that you describe.

5. If you absolutely need a single file populated with dumb solid, (without using parasolid), then try export part, turn on the "All Objects" selection filter and perhaps turn on "Remove parameters" then select what you need to export and dump it in a new file or an otherwise empty one. Turning on all objects allows you to select the solids from within an assembly. You will also need to display the reference sets that contain solids (not reps).

6. You could delete the mating conditions, and would had followed step 5, (cloning will maintain mating). Why you would want to do so eludes me at this stage. Please enlighten us if we're wrong.

Hope this helps,

Hudson

P.S. If your system manager is placing restrictions upon you when you have legitimate need of them you should be able to make a reasonable case that it is affecting your ability to do your job to best effect.