NX Filleting - Best Practices 2

[DLH81]

This is a bit of a generic question, but I'm wondering if anyone has developed some best practices for putting in edge blends in NX. I'm using NX 8.5.

I'm asking because it seems that putting in blends is the most finnicky part of creating a model. For example, in creating a complicated casting model, it can take as long or longer to add the fillets in as it did to create the solid model. It seems to depend a lot on the order you put fillets in, or selection filters (single curve, tangent curves, etc.), and probably other factors I'm not aware of. I'm hoping someone might have come up with some general tips on adding edge blends in NX that they might be able to share.

Again, this is also a very generic question because I don't necessarily want a solution to one particular issue, but something to help our modeling practices going forward.

Thanks in advance for any help.

 

[SDETERS]

We usually put most fillets at the end of the model tree. We fully draft and fillet our casting models. So usually the end of our fillets part history is as long as the actual part features with fillets.

 

[looslib]

Use simple sketches to build your model.
Do not make 1 complex sketch when multiple simple ones can be used.
Add holes after the model 'block' is constructed.
Add draft and blends at the end of the model tree.


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

Ben Loosli

 

[JohnRBaker]

While this used to be a lot more critical than it is now, it's still generally a good practice to start with the largest radii blends first and then add the next smaller blend, etc. And while some people will argue this point, if one or more of your sketch profiles could have included an arc representing what could have albeit been created using a Blend after extruding/revolving a simpler sketch profile but this radial feature is prominent and/or is a significant part of the final shape, go ahead and create it as part of the Sketch. This will reduce the 'complexity' of the final model tree and if these 'arc' profiles truly are part of the basic shape of the final solid model, it might be easier to control your 'design intent' by including them in the sketches rather than by trying to impose them on a strictly rectilinear initial model.

One other thing, while it is true that using Face Blands will provide you with some additional options and flexibility, generally speaking, start with Edge Blends whenever possible as they are much easier to understand and use. The only exception to this is when you need a true Three-Face Blend as your only practical solution is creating a Face Blend using the new (starting with NX 7.5) blend Type, 'Three Defining Face Chains'.

John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
Industry Sector
Cypress, CA
Siemens PLM:
UG/NX Museum:

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

 

[SDETERS]

Also We model the inside of the casting and the outside of the casting and then cut the insdie from the outside. I have always struggled with putting the fillets at the end of each inside and outside feature group and then cut the two parts. Or should I make the cut inside from the outside then add all of the fillets at the end.

 

[carlharr]

Interesting, I've just been testing a synchronous move by re-modelling an actual part, bit by bit, to see what was causing the move to fail. The move failed when I re-ordered blends to make them look more like the real part, with largest blend second!

The old rule still applies, largest blends first give a better result.

http://www.jcb.com

NX 7.5 with TC 8.3

 

[uwam2ie]

my experience / best practices also worked in catia and nx
no detail fillets in sketches, prefer edge blend feature
blending at the end of feature tree after holes and drafts,
start with the material adding blends then the material removing blend from large to small
collect blend features with the same size, versus new sets in same feature - feature groups also well arranged
avoid conic and variable blends
... this order will not cover all situations - but the most

 

[uwam2ie]

removing blends with st,
start with the centers of the Y blending situation, at second with path of blends
replace face can help in some situations, remove face/blend not cover

 

[carlharr]

Here is a simplified version of the issue I had, created in 7.5.

If you switch on the features in the first feature group one-by-one, you can see the order I've applied blends, and the subsequent move face (in XC direction) with three faces selected.

If you then switch off the first group and switch on the second, you can see (my version of) the original part, with blends in the "wrong" order. The result isn't visually as nice, but also in this case a move will not work.

As an aside...

Would anyone know a way to achieve the move in the first feature group without carrying out the split body first?

http://www.jcb.com

NX 7.5 with TC 8.3

 

[KhimaniMohiki]

Hi Carl, the aperture not having any faces makes it difficult to move without splitting the body or dividing the face, regardless of the blends. if you make it a solid you can move it a lot easier

Khimani Mohiki
Design Engineer - Aston Martin
NX8.5

 

[carlharr]

Khimani,

Hope you're well. You're correct, thicken first and away it goes! Thanks Carl.

http://www.jcb.com

NX 7.5 with TC 8.3

 

[cowski]

In the 2nd group, there are at least 2 options to get the "move face" to work:
[ul][li]note that blend 10 has adapted around the pocket area, select the 3 transition faces of the blend along with the other selected faces[/li]
[li]change blend 10's "overflow resolution" options to get the same result in the first feature group: turn off the "roll on edges (smooth or sharp)" option and turn on "maintain blend and move sharp edges". The move face command will now work selecting the same faces as in the previous group.[/li][/ul]

In the screenshot below, the extra blend faces have been selected for the move face command:

www.nxjournaling.com

 

[carlharr]

Thanks cowski, learned something new about blending there.

In the un-modified version, I selected the three transition faces as per your description and the move also now works (note I didn't need to select the back face below them). Am not sure if I tried that with the real model, so I will send an image to the engineer.

Thanks, Carl

http://www.jcb.com

NX 7.5 with TC 8.3