Edge blend, symmetrical part, 1 side works...one doesn't. Grrrr.

[Jaydenn]

Ok, so I have a perfectly symmetrical part and I need to apply a blend on each side of the part(naturally...).

Now, I personally modeled the part so I know that it is in fact PERFECTLY symmetrical.

When I apply the blend(9mm), I can get it to work on one side without any issues at all. Any size. Always works.

The opposite side doesn't blend. the only way it blends is if I make the blend very small(2mm).

Any suggestions as to why?
or any suggestion on How I could do this?

I included a pic to give you an idea of the geometry in question.

J

 

[JohnRBaker]

Without the actual part, there is very little that can be said about what might the issues be or if there's a solution.

However, that being said, since you state that it's symmetrical, if it's symmetrical about a plane, why not model only HALF the part (the part where the blend works) and mirror it to get the other half?

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.

 

[ingallspw]

That was going to be my suggestion as well.

Is the part too sensitive for you to upload here and let others give it a shot?

Keegan

 

[Jaydenn]

Alas, I cannot upload the model. It is sensitive as Keegan put it.

I was more or less just curious how it's possible that a mathmaticaly symmetrical model works on one side and not the other. seems very strange to me.

Mirroring the part is a great idea. Never even occured to me!!!

Anyhow, as I was typing this, and playing with my model, I managed to get the blend to work.
I broke the fillet into 2 seperate blends. One of the blends has a strategic trim plane that basically wipes out some of the tricky areas leaving behind a more simple edge for the second blend.
Works for me.

J

 

[JohnRBaker]

Contrary to what might seem logical, mathematically symmetrical models aren't. And this can be especially true when it comes to things like blends.

After all, consider the modeling coordinate system (CSYS and WCS). When working on the 'other side' of a symmetrical model, the modeling coordinate system is not reversed, it's still the same as it was when working on the original side, therefore the mathematical routines have to accommodate that situation, and so while the model may appear to be mathematically symmetrical, the math that is used to create new features is NOT since it has to work relative to the un-reversed (non-symmetrical) modeling coordinate system.

Now granted, we work very hard to create modeling functions which takes this into account, but there will still be situations which could not be anticipated and so could prove to be problematic. Now in cases like this, even if you do eventually manage to find a workaround or something, it would still be a value to contact GTAC and submit your examples since this is the only way that we can improve the software so as to account for these as-yet undiscovered special cases, which we do use to help create more reliable and robust modeling functions in future versions of NX.

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.