Trouble with a rail (Lofting kind)

[vex]

So... I seem to be running in to issues with setting up this rail for my loft. This rail was setup by extruding loft "profile 1" and then projecting on the surface from another sketch (from the x-z-plane). The extruded profile is tangent where necessary and *should* in my opinion provide no issues. But lo and behold it does.

 

 

[vex]

Some additional pictures.

[laughingcreek]

does it fail if you omit the circled rail?  If not, check that rail with a curvature comb to see if it is still G1 at that point.  sometimes when projecting across a G1 edge the line can degrade to G0.  you can fix by making profile for the extrude smooth instead of just tangent (maybe)

[vex]

No, the lofting doesn't fail if that rail is omitted, but it does cause a bulge which I find unsuitable. Unfortunately using the smooth constraint doesn't seem to help either. But the curvature there does abruptly change there for some reason. Not quite sure I understand why it does if I'm honest.

[vex]

I've been playing around with your idea: Instead of using a smooth constraint I redid that portion of the extrusion by using a spline and manually forcing the tangents at those locations in a similar fashion. This seems to work well in getting rid of the original error (G1 to G0). Now I'm subject to the 'Rail can not be tangent to profile' error--which is again strange to me as none of the rails are tangent to any of the profiles.

To add even more weirdness to this issue, when I do the curvature analysis on it again I still have a discontinuity there but Fusion has no problem chaining the rail now.

It also is now possible to select one of the rails on the surface, just not both... I think this error is the inability for Fusion to solve the half circle of the loft profile to the straight line. Anyone from Autodesk care to weigh in?

[laughingcreek]

maybe attach your file?

[vex]

http://a360.co/2wLPq43

Provided.

Yes, I know it's not very well organized and I'm sorry. *Puts on flame suit*

[laughingcreek]

sharing doesn't seem to be working.  can you attach it instead.  here's how to export from fuson-

[laughingcreek]

and, don't knwo what happened to pic, trying again-

[laughingcreek]

still not there, I guess there area some troubles over at the AD servers.

go to file-export.  export as a f3d file, make sure save to computer is checked, and attach to post

[vex]

Well, here's a screen cast of what I'm on about. I'm wondering if this is a bug within Fusion.

[vex]

Has anyone else had similar troubles? It'd be great if an Autodesk tech could take a look and tell me if I'm doing something foolish.

[PaulMunford]

Hi @vex

I'm not sure what shape you are trying to create, so it's a little difficult to give a definitive answer. I've attached a file with a possible solution for you to take a look at.

Here are some tips that have helped me out.

• A Loft is a four sided surface fitted to the input geometry.
• A Patch is a four side surface Trimmed to the input geometry.
• Lofts are more successful when the input geometry is four sided.
• Patches can be applied to any number of bounding geometries.
• To use a Loft with no-four sided bounding geometry - overbuild your lift and trim back.
• Lofts are more successful when the input profile contains the same number of geometries as the output profile (and the same with rails).
• Loft rails and profiles must intersect.
• Loft rails containing multiple geometries should be tangent continuous.

Does that help?

Paul

[vex]

Hey Paul,

Thanks for taking a stab at this. The design is for duct routing on my project car. There are some unique constraints that I'm stuck with, so actually getting the ducts the way I want/need them is constrained about trying to fit two other ducts, heat exchangers, and the various intake areas; all the while trying ensure that the profile increases as it traverses to the exchanger. Did I also mention there's only finite room for everything?

lol, I sure now how to choose the projects, huh?

[TrippyLighting]

I am pretty certain this was already answered in the other thread you started with the same geometry 

[samuel.templeUCPAE]

Due to the limitations, we have closed the following ticket:

FUS-37167

Thank you to everyone's incredibly helpful input in this thread.

[laughingcreek]

---

@samuel.templeUCPAE wrote:

Due to the limitations, we have closed the following ticket:

FUS-37167...

@samuel.templeUCPAE -That's sort of random.  what was that ticket for?

[samuel.templeUCPAE]

The ticket had been raised and mentioned in:
 https://forums.autodesk.com/t5/fusion-360-support/lofting-rail-issue-possible-bug/m-p/7555801/highli...

It was to investigate whether there was a bug causing the loft to not work or if it was due to limitations of the system. 

These two forum posts were very similar and were using the same model.