I am trying to model a nose cone/end surface with G3 surface conditions (as shown in the image below/file of model attached). I am using PTC Creo 7.0/Style.
I'm trying to achieve a G3 surface condition on all 3 domed sides and a normal constraint around the bottom perimeter.
So far I am only able to achieve a G3 condition on the central curve/surface and a normal condition around the bottom perimeter. When I try to increase the two surface conditions either side of the central plane from a G2 to G3, I get the following error message:
"The cross curves are not connected with the same continuity as the connection"
I'm not sure what I am missing here? It would be great if you guys could take a look and tell me what I am missing?
If you are designing a nosecone for engineering purposes you will be better off using curve from equation and revolving it. If this is an academic exercise in CAD then ignore this comment.
Look at the curvature plots of your curve connections.
The curves used to define the surface must be connected with a degree of connection equal or greater than the surface connection you need. The curves are not connected with G3 continuity so you will not be able to create a surface with G3 on that boundary.
Thanks, yes, I understand the concept of the difference between a G2 and G3. I used Alias for a while and still use NX. Alias uses this graphic, very simple to understand:
I'm just not sure what the "cross curves" error is actually referring to, no where else is the term "cross curve" used in Creo? I searched the help section for "Cross Curves" and nothing comes up?
If is helps, I can upload the latest file I have worked on. The files is constructed in the following way:
- All splines with 7 degrees
- All spline to surface connections G3 surface continuity connections.
Result: Only G2 is possible for the resulting surface.
Just built the same geom in the same way in NX and it works fine.
Getting closer, but still not quite there 🤔...
Now trying to build the whole thing in ISDX (style), which really seems like the only way to do it because trying to manage either a G2 or G3 curve as a conventional sketch in Creo is made so difficult to control and manipulate.
All splines 7 degree. The trim doesn't actually appear to be the issue...
As you can see, all surface conditions now G3, accept the final surface condition which is G2. Doesn't seem to matter which order I attempt (using this method - trim/top hat) the final surface condition maxes out at G2. This is probably absolutely fine for 95% of what I do, but would still nice to achieve a perfect G3...if that is even possible 🙂
Any thoughts?
