Sweep with helix giving unexpected results

[chorca]

I've been trying to generate a custom thread for awhile now and I've been running into several roadblocks, currently this one which is really confusing me. Wondering if someone here may be able to help with this issues.

I've extracted a helix from a square coil, created a plane with a sketch on one of the paths and used the two outer sketch lines as a path and guide rail for a sweep command using a simple shape, but for whatever reason, Fusion seems to be uncooperative.

I've also tried using the Sweep tool from the Surface tools, but experienced similar results.

Using Single Path, i'm getting a rotated shape instead of one that stays flat. However, now it seems to somehow be extruding two paths simultaneously, though only one can be controlled?

Using Path + Guide Rail, I'm getting really odd shapes that are not functioning as I'd expect.

I've made a screencast to show the issues. Basically i'm just trying to sweep this profile in a helix using it as a thread, so I want to keep it along the two sketch profiles i'm using as guide rails.

On top of this, i've somehow gotten an orphaned body while playing around with this that shows up but can't be deleted or edited, just turned on or off.

I feel like this might be a bug, or something I've done horribly wrong in trying to generate a helixed profile.

https://knowledge.autodesk.com/community/screencast/16d43c96-b731-4cf4-9ebd-1519bab21085

(also it seems if you post a screencast URL while it's still processing, it acts as if the screencast was not attached)

[chorca]

Apologies, also meant to post the .f3d file.

[chorca]

Aaaaand you can't edit a screencast into a post it seems.

https://knowledge.autodesk.com/community/screencast/16d43c96-b731-4cf4-9ebd-1519bab21085

[davebYYPCU]

Use Path and Surface, for the Path, select the outside top edge of the coil, then hide that body, 

You are not following best practise, Origin not on centre, undefined sketches,

Guide rail does not penetrate the Sweep profile, 

Can not explain body 6.

You may need new geometry for the thread to start higher and go lower than the finished fitting.

File returned....

Might help...

[wmhazzard · Accepted solution]

I changed a couple of things to get your model fixed. First, I prefer a triangle for the coil. I think the major problem was that the plane for your thread sketch was not on the end of the coil, you should have used offset plane instead of plane along path. 

[chorca]

This makes a bit more sense now.. I'd started with a triangular helix but moved to the square as I was trying to figure out where I was going wrong. I didn't think of using the back of the helix as the guide surface, but that seems to be what was causing my helix to stop early before. (before I started messing around and causing even more issues)

I re-created your example in my design and it worked!

I'd read somewhere that the profile needed to be on the path to work properly, so i'd created a plane along the path, but it seems that's not the key.

Thanks for the help, I was stumped for a couple hours on this.

[laughingcreek]

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@wmhazzard wrote:

...you should have used offset plane instead of plane along path. 

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Why do you do you say that?  with an offset plane the profile won't be normal to the path.  That in itself can cause issues with sweeps.

[wmhazzard]

Because the plane along the path is normal to the path, not the face of the coil and the angle difference is due to the pitch angle. The thread profile needs to be along the axis of the cylinder, not normal to the path.

 

[khokeson]

2025 and this still isn't fixed. Sweep a helix and the profile slowly deviates; by 180 degrees it's already skewed.