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Surfacing Help: Style Surface Boundary Conditions

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Surfacing Help: Style Surface Boundary Conditions

I've been working more on this shroud (http://communities.ptc.com/thread/56128) and now I'm trying to figure out how to control the boundary conditions of a style surface.

The boundary conditions at my edges where I have control curves are good (i.e. they are curvature continuous and normal to the plane, but in between control curves the surface does not keep that condition.

SNAG-0384.png

This becomes obvious when I thicken the surface with a normal offset. If the surface were normal, the part of the edge would be coincident with the horizontal red line (surface edge).

All of my edged except for those on the inner circle have edge control arrows. Why don't the arcs?

8-21-2014+12-24-40+PM.png

1 ACCEPTED SOLUTION

Accepted Solutions

Re: Surfacing Help: Style Surface Boundary Conditions

Ok, making progress.

First thing I found (and my first mistake) was thinking that the wireframe curves would be sufficient for defining the curvature was wrong.

Second, I found that the surfaces (even if the part won't actually have those physical surfaces) adjacent to the smooth (G2) surfaces must be defined. In my case, these were the two cylindrical surfaces that represent the final smooth airflow direction and the 'rim' type surfaces perpendicular to the airflow.

SNAG-1007.png

With those surfaces, I could then go and define the end points of my styles curves to be Continous.

SNAG-1003.png

Then I could go and make connections between the style surfaces and my reference continuos surfaces by selecting the broken line indicators.

SNAG-1004.png

If more than one surface was possible, then you would get a prompt like this (asking if the red surface was the correct surface to connect to).

SNAG-1005.png

Once those connections were made, then I could set those connections to be surface continous (they defaulted to tangent).

Still have some investigation to do and cleanup, but this looks like a solid solution.

SNAG-1006.png

23 REPLIES 23

Re: Surfacing Help: Style Surface Boundary Conditions

Hi,

Use cylindrical surface instead of the arc curve to be able to set the boundary condition for the compound surface you are making.

If your curves don't have curvature continuous connections with the adjanced surfaces then the surface you are making won't be curvature continuous either.

Re: Surfacing Help: Style Surface Boundary Conditions

Not quite sure what you are meaning. I've attached the file so you can take a look.

The center circle is just that, a circle. The guide curves are style curves; planar, 3rd order, two points only with end point conditions of either horizontal or vertical.

Re: Surfacing Help: Style Surface Boundary Conditions

Ok, making progress.

First thing I found (and my first mistake) was thinking that the wireframe curves would be sufficient for defining the curvature was wrong.

Second, I found that the surfaces (even if the part won't actually have those physical surfaces) adjacent to the smooth (G2) surfaces must be defined. In my case, these were the two cylindrical surfaces that represent the final smooth airflow direction and the 'rim' type surfaces perpendicular to the airflow.

SNAG-1007.png

With those surfaces, I could then go and define the end points of my styles curves to be Continous.

SNAG-1003.png

Then I could go and make connections between the style surfaces and my reference continuos surfaces by selecting the broken line indicators.

SNAG-1004.png

If more than one surface was possible, then you would get a prompt like this (asking if the red surface was the correct surface to connect to).

SNAG-1005.png

Once those connections were made, then I could set those connections to be surface continous (they defaulted to tangent).

Still have some investigation to do and cleanup, but this looks like a solid solution.

SNAG-1006.png

Re: Surfacing Help: Style Surface Boundary Conditions

Be careful with mirrors. I am seeing some interpretation going on when you mirror with some assumptions. not every feature truly mirrors! I noticed this when I used curvature analysis but it was clear with the knot analysis...

shroud.PNG

the left is a mirror of the right where a C2 curvature was chanded to a simple arc.

This is actually a fairly disturbing development. the left side is the mirrored feature.

shroud_II.PNG

Both sides are treated equally. there is no reason for this to have developed differently. Each mirrored feature was investigated for commonality.

Re: Surfacing Help: Style Surface Boundary Conditions

Mirror the quilt instead of the features. Much more robust.

Re: Surfacing Help: Style Surface Boundary Conditions

Wow! THAT is very disturbing! Hey, PTC, I EXPECT things to mirror perfectly. I EXPECT pattern geometry to work perfectly. I do NOT expect this kind of garbage from what is priced as premium CAD software.

I've seen funny things, and geometry not working right, but never expected it to be this bad. Thanks for the in depth analysis Antonius! PTC should be paying you for developing their software for them......

Re: Surfacing Help: Style Surface Boundary Conditions

This is scary indeed. I remember arguing the very opposite problem to this one with helical sweeps...

Thank you for the tip, Tom. I never knew you had the option to select only the quilt without its definition. Of course, smart is the default selection filter.

However, the right edge is a C2 blend giving the course rooster tail. Notice how it still softens this edge closer to radius. PTC is known for its surfacing prowess but my recent experiences say that it does a lot of fudging. Not as bad as the mirror of the geometry, but still something to note for those relying on curvature blends.

This is the same mirror with a quilt. Mirror is highlighted in green.

shroud_III.PNG

Re: Surfacing Help: Style Surface Boundary Conditions

I've opened a tech support call on this. I would expect them to issue an SPR. If they do, I will post the details here.

Re: Surfacing Help: Style Surface Boundary Conditions

You would think that the programmers would make this analysis instead of having to have the users do this.

Antonius - How much do you get paid from PTC for all the bugging, error fixing work arounds and miscellaneous things that you do?