Parametric Spline

[bfleck]

What are peoples thoughts on how to create a parametric spline that is related to other arcs and curves. I believe the splines should be created in a sketch along with the arcs and curves. Attached is a sample shape that I want to replicate and make parametric.

 

[jerry1423]

What I do with splines is I put the points in a sketch. Then I exit the sketch and use a studio spline and associate it to those points.

 

[Xwheelguy]

Creating splines in a sketch is fine until you get into continuity between the spline and the adjacent curves.

I think Jerry has a good workflow described above, and that can be applied to Studio Spline by poles as well, although I usually let the poles move freely and adjust by hand while referencing a curvature comb of the spline.

Tim Flater
Senior Designer
Enkei America, Inc.

http://www.enkei.com

Some people are like slinkies....they don't really have a purpose, but they still bring a smile to your face when you push them down the stairs.

 

[hudson888]

In NX-3 we found that studio splines had a tendency to wander off the curve plane when edited manually in model space. I have noticed that in NX-5 this is more controllable and see little need to even have the points in a sketch. The explanation for this is that the continuity poles first and second from either end in cases of G1 and G2 respectively are in my opinion not best constrained by sketch points. I would have thought that you'll find it easier and probably better to just build the splines in model space as studio splines.

Best Regards

Hudson

 

[Dave K]

I wish the spline tool within sketcher, had the G1, G2 constraints, that the Studio Spline outside of sketcher has.

-Dave
Everything should be designed as simple as possible, but not simpler.

 

[hudson888]

It does but they're not associative in the same way. So when you attempt to edit the spline you basically ditch the continuity 90% of times when you touch it, or if you alter the inputs it also does not follow.

As long as the version in model space works as well as it does I doubt that there really is all that much missing functionality.

Best regards

Hudson

 

[cowski]

How about a 'bridge curve'?

I have not tried these within a sketch, but I know they work well outside of one. If you are not familiar with bridge curves, they are associative to other string entities (lines, arcs, even other splines) and let you define tangency or curvature continuity at the ends. There are even shape controls that let you tweak the shape of the middle section of the curve.

 

[hudson888]

Matter of fact if you are working with a sketch as your basic curve construct then you'll be dead planar which means you could use a conical bridge. That's something which as far as I know isn't available in the sketcher.

Regards

Hudson

 

[Xwheelguy]

hudson,

I think the wandering has been fixed with Studio Spline, for the most part. The curve plane tool on the dialog seems to actually work a bit better now in NX5. However, I could be mistaken, as I did run into this anomaly a few times, but not enough to warrant in-depth testing. Creating a new spline usually fixed any issues.

Tim Flater
Senior Designer
Enkei America, Inc.

http://www.enkei.com

Some people are like slinkies....they don't really have a purpose, but they still bring a smile to your face when you push them down the stairs.

 

[bfleck]

Thanks guys.
I dont want to get a whole discussion going again about ProE, but I am too familar with ProE's creation ability and associativity of a spline within the sketch environment. What I dont understand is why you would create arcs and curves in a sketch then use another feature to create the spline or bridging curve outside of the sketch. This starts to add complexitiy to a model tree, plus I like to keep things grouped together.
Im gonna look at the bridge curve now.

 

[hudson888]

Bfleck,

Bridge curve and associative splines both live in the tree and are completely history based. The reason they don't live exclusively in the sketcher would be that they can be defined in 3D space, i.e. non-planar as well, so while having the same functionality in the sketcher would be good, but also a double up.

There are so many non-sketch based uses for these curves that require 3D, as to make the non-sketcher version the essential progenitor of any other and more limited functionality that would only work in 2D.

for what it's worth the studio spline is more capable but the bridge curve often easier. They both have their place and the geometry may not be identical since the methods do vary how and where inputs are constrained.

best regards

Hudson

 

[JohnRBaker]

The REAL reason that Smart Splines/Curves or Bridge Curves can't be created INSIDE a Sketch is because they are features themselves and a Sketch can NOT contain features. There is is NO history INSIDE the sketch. All Sketch constraints are solved simultaneously and this is incompatible with the idea of history-based features. Therefore you have to separate them. Granted, the Sketch itself can be included in a history tree, but not what happens inside the Sketch.

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

http://www.siemens.com/plm

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

 

[bfleck]

John,
Thanks for telling us the underlying reason. It is back to the old issue of 'unlearning the old and learning the new'. Thats why I wanted to see experienced peoples thoughts.