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Achieving a G3 surface condition - Help


Hi there,

I am trying to model a nose cone/end surface with G3 surface conditions (as shown in the image below/ZIP file of model attached). I am using PTC Creo 7.0.

I have sketched a number of reference lines to control the length/width/depth of my cone. I have then modeled all of the spines in style with G3 end conditions (including the internal influencing spline).

When I generate the surface in style I am able to generate G2 surface conditions, but when I try to apply a G3 condition I get the following error message:

"The cross curves are not connected with the same continuity as the connection"

I am not sure what this error message is referring to or how I should be modelling this feature to achieve a G3 surface?

If you can help me out, I would really appreciate it!

Nose Cone.png


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So I thought I'd share where I am up to, see below and file attached.

By adding ribbon reference surfaces (yellow) and changing where I place my cut on the first 4 sided surface, I can achieve the following:

- G3 surface condition on the initial 4 sided arch surface
- G3 surface condition on the left and right hand side of the nose surface
- G2 surface condition on the top of the top of the nose surface (driven by central guide curve)
- No surface condition on the bottom of the nose surface (driven by central guide curve)

So I think my trim method has resolved part of the issue, but my central guide curve is still causing a problem. The zebra stripes and curvature combs now look nice across the entire surface, so maybe I am trying to over constrain the surface, I am not sure?

It would be great to hear from you guys! :)

Nose Cone 2.png


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Attached is the equivalent G2 nose cone. So simple...I'm not sure why the G3 version is so much more difficult to achieve?


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