Instanced 3D curve blend in NX8.5

[PrintScaffold]

Greetings all!

The point is to make this pattern fully parametric, so that I could control number of instances just entering the number in Expressions. Is it possible to create a 3D blend between two sketches so that it is smooth and continuous (recognisable as 'tangent curve' by selection intent filter) and instance them using Pattern Feature? I managed to model everything but this blend. Circular Blend Curve won't work because it won't trim the input curves - at least I coulnd not get it trim them.

Example file attached.

Industry creates wealth!

 

[jerry1423]

Can you show a picture of the sketch?
We are running NX7.5 here.

 

[PrintScaffold]

Hi!

Thanks for the response, but I'm interested in the Pattern Feature tool which is absent fron NX7.5.

Industry creates wealth!

 

[PrintScaffold]

But of course, here comes the sketch.

I have already solved this task using the bridge curve, but maybe John could add something here?

Industry creates wealth!

 

[PrintScaffold]

Update: I thought that I solved it, but the blend is not recognised as 'tangent curve'.

Industry creates wealth!

 

[JohnRBaker]

Actually that was going to be my suggestion as well, using a Bridge Curve. I was working on a solution earlier but then forgot to file the model when I shut down to go home (my bad).

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.

 

[SvenBom]

Maybe a silly question, but still I have to ask.
I guess that you want to create a Circular Blend Curve between sketches 8 and 9.
And then, I supose, you want to sweep sketches 5 and 6 over this new curve (sketch 8, 9 and circular blend).

If this is the case, why do you need to trim the input curves? You can still turn on the options Stop at Intersection and Follow Fillet. With those two options you don't have to trim the input curves.

The only problem I have on your model is, that not even Circular Blend is giving me the tangnet transition. It is tangent only to one curve and not to both. So I am still searching how to make this transition tangent.

 

[cowski]

SvenBom is correct that the Follow Fillet option should work in this case; however, it doesn't give the expected result. Perhaps this is something to take up with GTAC.

Attached are two ways to do this using 1)circular blend curve and trim curve and 2)a bridge curve.



www.nxjournaling.com

 

[JohnRBaker]

I think you will find that it's mathematically impossible to create an ARC segment (i.e. fillet) that is tangent to two curves NOT lying in the same plane. The new 'Circular Blend Curve' function attempts to approximate an 'arc' tangent to two 3D curves but again there are limitations in that one end will always be tangent while the other may or may not be depending on exactly what the curves are and their spatial relationship to each other.

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.

 

[cowski]

John,
No one said anything about creating an arc segment.

Use the Circular Blend Curve command to create a smooth, blended curve between two 3D curves or edge chains. The blend curve is tangent to the two input curves and looks like a circular fillet if projected onto a plane normal to the selected vector direction.

(emphasis mine)

The circular blend curve is a spline that closely approximates an arc when projected onto a certain plane. According the the help file it should create a curve that is tangent to 2 input curves; if it does not, then it is not working as designed and should be shown to GTAC.

www.nxjournaling.com

 

[JohnRBaker]

The first sentence in my response was strictly to set the stage, as it were, for the explanation of what the 'Circular Blend Function' was designed to do. Note that I've also read the NX Help files and I too saw the comment about creating a curve 'tangent' to both input curves, but in all the testing that I've done, except in very limited cases, I always got what NX recognized as being a 'tangent condition' at only one end of the added curve. However, feel free to contact GTAC and open an IR and have them investigate this and see what development's response is (in fact I might do the same thing now that you've brought it up and reminded me of my past experiences with this function).

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.

 

[PrintScaffold]

Hello gentlemen! Thanks for all comments!

John, I'd be greateful if you could report it yourself and get back to all us with the response.

Industry creates wealth!

 

[cowski]

John can report it, and probably already has; but if this functionality affects your workflow, you should report it too. Reports from customers carry more weight; and the more customers that report it, the more likely it is to get fixed/enhanced.

www.nxjournaling.com

 

[PrintScaffold]

I didn't do all the tests as of yet, but bridge curve solution seems to be doing the job. If not, then there are some other methods to consider. Of course, if CBC issue becomes really painful, I'll report it to GTAC. I'm not shy of doing this.

Industry creates wealth!

 

[JohnRBaker]

OK, if you haven't talked to GTAC yet, don't waste your time.

The issue is NOT with the 'Circular Blend Curve'. It's doing exactly what the documentation says and what you'd expect, it's creating, in this case, a spline that is tangent to both of the 3D curves, not all that different than if you had used a Bridge Curve just that with the 'Circular Blend Curve' if you look along a certain axis (which the user can control how this axis is determined), the curve will appear to be a fillet, i.e. 'arc segement'. It's working as designed, and more importantly, exactly how you would expect it to.

No, the issue is with the 'Selection Intent' rules, and even there, NX is working as documented. The issue is that while the 'Curve Rule' reads 'Tangent Curves', the modifier that we were trying to use that did not require that the two 3D curves be trimmed to match the ends of the 'Circular Blend Curve', the option titled 'Follow Fillet', only works with actual arcs/circles, and that's stated, probably not as clearly as it could have been in the Help files, but it's DEFINTELY CLEARLY stated in the 'bubble-help' that appears when you hover over the icon as shown below:

Now to verify that the 'Selection Intent' function was working 'as documented' I tried using a G3 continuos, about as 'tangent' a condition as you can get, 'Bridge Curve' instead of the 'Circular Blend Curve', and 'Follow Fillet' still didn't recognize it as a 'fillet'. But if the curves were trimmed so that their end points matched then the normal 'Tangent Curves' Selection Intent 'Curve Rule' workied just fine.

Anyway, sorry for contributing to the confusion as I should have looked into this sooner before we went off thinking that somehow the 'Circular Blend Curve' function was the culprit.

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.

 

[PrintScaffold]

Thank you, John! You're brilliant, as always.

What blending method would you recommend to get reliable results when it comes to the tangent or possibily connected curve filter?

Also, I believe in NX9 there is a new tool to blend 3D curves directly (haven't yet tested it). Would it help us in this situation?

Industry creates wealth!

 

[SvenBom]

One more question for JohnRBaker.
If the Follow Fillet Works only on actual arcs and circles, what does it work partially on the model, that PrintScaffold has provided?
I also have attached the movie, to better explain, what my question is.
In the movie, you can see, that if I select the curve from sketch(9), Follow fillet recognizes my Circular Blend Curve. But, if I select the curve from sketch (8), it doesn't recognize. And it doesn't matter, how I have defined Circular Blend Curve (CBC). I have tried with sketch (8) being the first curve or the second in CBC. I have changed the Shape Control and Curve Fit settings, etc.
Is it simply a mathematical problem? But I think, that I could changed the tangency curve at least. So that in one option, CBC would be tangent to sketch(8) and not to sketch (9). Not that it will help a lot.
Any explanation would be appreciated.

 

[JohnRBaker]

I've seen that behavior before and can't explain it either. The only thing that I can think of is that on occasion, even if the end points are not coincident, the actual Curve Rule of 'Tangent Curves' takes over, just that it cannot be made reliable enough to be counted on in all situations.

As for the first question, I would trim the ends and make sure that the 'tangent' curves are continuous as that appears to provide the most reliable curve 'chaining' behavior.

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.