Spline control, curvature continuity, "simple" corner round

[carbinefong]

I am using Creo 4.0 and I just want to make a simple curvature continuous round.  I used to have to do this manually without the advanced surfacing package, but I was glad to see curvature continuous constraints built into Creo 4.  However, with those constraints and tangency constraints, this spline shown IS NOT SYMMETRIC.  I tried to constrain the control points and use a control polygon, but none of it yields a symmetric spline!  What is going on?!  I'm downloading Creo 2 now to see if I can get my simple spline back.

"simple" curvature continuous spline round

[BHOoi]

Hi, I am on Creo 2 and the 2-point spline is symmetrical as shown below:

[carbinefong]

Thx, but I need at least one control point in the middle of the spline to approximate a simple round.

[BHOoi]

This is with a control point at its mid span:

It looks symmterical but actually it is not. I mirrored the cure and it does not overlap exactly to the original one:

[carbinefong]

wow thanks for doing this.  I used to constrain the control points as much as I could and I assumed it was symmetric.  The newest version of Creo 2 doesn't allow constraints on the control points anymore. what build are you running?  

[BHOoi]

M240

[BHOoi]

Instead of sketching out the section, possible to make use of the options in round feture?

[carbinefong]

that's not a good idea when it's a primary surface.  can't have a round that low on the feature tree because they break all the time.  need to draw it right in, and need to be able to control it.

[BHOoi]

what about modeling half of the curve and mirror it .

[carbinefong]

Unfortunately the mirroring of splines has been a problem with proE for a long time.  To do it effectively, I would have to go outside the curve and mirror the spline in a separate curve with a mirror feature, and I wouldn't be able to guarantee curvature continuity across that mirrored feature--only tangency.

After a few weeks trying to do the same things in Solidworks, I have to say that their spline mirroring and spline control features are actually better.  I can actually very easily make this same spline symmetric about that 45 degree centerline.  

[BHOoi]

Hi, I tried this workaround and it may work for you as well. I use a contruction curve(an arc in this case) for curvature reference before mirroring.

The curvature is then mainatin across the mirro plane and symmetrical. I attached the creo2 file for your reference too.

[TomD.inPDX]

Available Curve Controls

This is a 3-point curve.  It is not bound tangent, rather it is optionally dimensioned to be tangent.

By doing this, it also gives me access to the curvature dimensions.

And I can fix the center vertex orientation by dimension.

The most problematic thing about curves with 3 points is that you have to know that each end is exactly the same length.  Position along the curve is not managed anywhere that I can find.

My results here are Creo 2.  Somehow I am not holding my breath that anything real was done between Creo 2 and Creo 4 on these antiquated curve features.  Just wanted to show you there are some hidden features!