Lofting a Handrail Wreath in Fusion 360

[jakedbirk]

Hello, 

I design, manufacture, and install tangent handrail wreaths from time to time as a part of my job. 

A tangent handrail wreath is a handrail fitting that curves and twists as it ascends the stairway to deal with a turn or radius on a staircase. I linked to an article that describes their purpose and geometry better than I can here.

I am currently attempting to make a wreath with a very simple handrail profile using a derivation of this technique that I learned from Emmanuel at ScaleLegno. 

The desired output of this loft should look li...

Except the notch in the bottom of the profile should be plumb the entire way up, and especially at the ends where the wreath will join straight sections of handrail. 

When I try to loft the profiles with the center arc as a guide rail, I get the following error:

I've tried to add more profiles in the middle to help guide the software: but this has not helped. 

How can I sweep this simple profile along this tangentially connected centerline while keeping the profile "plumb"  along the sweep/loft/wreath? I am quite sure this technique should work well, but it keeps throwing me errors I can't seem to fix. 

I've attached the file. 

In the past, I've tried to use a sheet metal guide surface for a sweep with poor results. So I don't think that would be a good solution to this problem. 

I've attached a .f3d file related to this post.

I run into situations requiring this technique quite often, and would like to continue using F360 as my primary CAD, but can only do so if I find a way to handle this situation. Switching to a software like Rhinoceros would be costly as we've invested a substantial amount of resources into F360 and I generally like it. 

I'm really hoping I can find some help here. 

[davebYYPCU]

I can’t access your file but thanks for adding it.

Loft is finicky, 

break it to 2 easier parts.

Seems like you want a pipe / rod, (Pipe or Sweep a circle / ellipse)

Then cut a vertical groove along bottom dead centre, (Sweep > Cut - a rectangle)

Will save some grief.

Might help….

[jakedbirk]

Hi Dave, 

Thanks for the response. I apologize that you weren't able to open the file and will try to re-upload it in this response.

I tried breaking it into 4 different lofts on just the lower section of this wreath, and they still failed with the same intersection error message. 

For this particular example and rail profile, a pipe sweep would be visually similar, but I plan on using this technique with more complex profiles in the future. 

This example shows a wreath I made in the past with loft, but it's not accurate enough to actually drive production: 

Is there a way for me to impliment this technique in Fusion 360? Or will I have to switch to a more robust 3D modeling system?

[davebYYPCU · Accepted solution]

Probably nothing wrong with the file, because I am away from the computer for another week.

I have reviewed the linked material, and thankfully, converting to 2d in Fusion is not required.

You are joining a section of railing, that has the same profile at each end, so Sweep is the tool to use. (For any profile)

If the Sweep tool is twisting, you need to control it with Sweep, Path, and Guide surface, (parallel profile setting)

referring to the linked references, use the outside cylindrical face as the selected surface.

Might help….

[jeff_strater]

I, also, don't have time just now to look at your design (on vacation...), but, in general, if the profile of the object is constant along its length, Loft is not the right tool.  As @davebYYPCU says, Sweep is probably the tool best suited for this task.  You might need to use one of the more complex versions (loft with rail, or loft with guide surface) to control the twist, if the path is complex.

[TrippyLighting · Accepted solution]

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, decorative fillet@jakedbirk wrote:

Is there a way for me to impliment this technique in Fusion 360? Or will I have to switch to a more robust 3D modeling system?

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If you use less than robust modeling techniques, you'll encounter exactly the same problems in even the most robust CAD system 😉

I would start by fully defining sketches.

I would only use 3D sketches if absolutely necessary. In this case it isn't.

But as shown in the video (and already explained by @davebYYPCU ) the sweep tool is the best tool for this job.

It will take a while for the YouTube video to convert into the High res versions.

[jakedbirk]

This worked beautifully and was super easy to impliment. I really appreciate you taking the time to write this response.

see attached photo.

I apologize for the late response, I've been busy making these things! 

[jakedbirk]

I really appreciate you taking the time to make that video. 

I ended up practicing with all of those different techniques. Adding the surface loft as a guide rail was a good idea, one to keep in the toolbox. 

The sweep with twist is another good thing to keep in mind.