loft bad geometry - why?

[fratiman.vladut]

Hi!

I'm a new user of Fusion 360 and I'm trying to reproduce an object as an exercise.
When I try to use the loft command, I have 2 rails that give me the error mentioned in the title.
I do not understand why. The two rails were obtained using the intersection curve command. Maybe that's the problem.

[jhackney1972]

I used all 4 rails in the loft without error.  I also used 2 reference rails and 2 spline rails in loft without error.  The 4 rail loft is attached.

[g-andresen · Accepted solution]

Hi,

watch the screencast and follow the timeline

günther

[fratiman.vladut]

It's still not clear why it works for you and it doesn't for me. I downloaded the attached file and checked, as seen in the attached screencast.

Thanks for the reply!

https://autode.sk/3sSvont 

[fratiman.vladut]

Thanks!

After clearing the projections, I was able to use the loft command.
However, I can't create a single body, as jhackney1972 got.

I also can't combine the two bodies obtained.

[jhackney1972 · Accepted solution]

I did not correct the sketching error, as you have already been shown how to do that, I just created the loft.

You have my model so I will only attach a Screencast of my process.

[fratiman.vladut]

Indeed, I followed exactly the steps indicated and the command creates the correct body.
Now the question is: why does it work when you first select the circle profile and then the ellipse profile and it doesn't work in reverse order when first select the ellipse profile and then the circle profile?
Does the command work for you when you first select the ellipse profile?
Because it's very strange. Does the order in which the two profiles are selected in the loft command matter?

[TrippyLighting]

If I create a section cut, the profile doe not look smooth but rather indented. Is that really the geometry you were looking for ?

Creating this lofted object without that artifact is a bit more complex> I've attempted tis using surface lofts, but it might well work with a soli loft as well.

[fratiman.vladut]

You're right, I didn't notice this problem.
It can be solved using only the rails obtained by the "intersection curve" command for the loft control.
I've seen what you've worked on, but I think it's a little too much work using surfaces. It also seems a little intuitive, at least to me.
I appreciate your time. Thanks!

[TrippyLighting]

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@fratiman.vladut wrote:

It can be solved using only the rails obtained by the "intersection curve" command for the loft control.

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I would not consider that a solution, but a compromise that attempts to balances time, lack of modeling skill and desired outcome.

That's not a compromise I can accept in my own work, thus I always strive and to a degree have achieved a level of skill so I don't have to make such compromises quite that often 😉

[fratiman.vladut]

The main problem is another. As I wrote earlier, it is strange that if I reverse the order of profile selection, in one case it works, in another it does not.
I have not yet received an explanation for this problem.
Regarding the compromises, the shape is an organic one, as long as there are no breaks of curvature, I don't think it can be said that it is good or bad in one way or another. It is a simple shape, not something geometrically precise.
How rigorous everyone wants to be is his business. I repeat, this is not a component that requires dimensional accuracy, it is a furniture handle in my house.

So, back to what is important: why do I reverse the loft command when I reverse the order of profile selection?

[TrippyLighting]

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@fratiman.vladut wrote:

The main problem is another. As I wrote earlier, it is strange that if I reverse the order of profile selection, in one case it works, in another it does not.
...

So, back to what is important: why do I reverse the loft command when I reverse the order of profile selection?

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I do not have a good explanation for that.  Sometimes it simply works. 

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@fratiman.vladut wrote:

...
How rigorous everyone wants to be is his business. ...

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Fair point!

I did successfully demonstrate - or so I hope - how you can achieve the geometry with all of the rails in your original model. At least, hopefully it helps to see another technique.