topic Re: Rectangle to round transition - how to extend the round a but further in Fusion Design, Validate & Document Forum

Rectangle to round transition - how to extend the round a but further

andrewsownemailPPGVB — Wed, 10 Jun 2026 00:30:38 GMT

I am using a lofted flange (sheetmetal) to create a rectangle to round transition. I want to extend the round up a by 10mm to give some extra material which will lap underneath the round spigot that will be spot welded on top (the lap then gets swaged).

I can't figure how to do this. I have tried all sorts, including creating a solid spigot (same material thickness) and trying to use the edge of this cylinder for the round profile of the lofted flange. AI said this was the way ‌‌ but it won't let me select this edge for the lofted flange.

The easiest solution I have worked out for a one off is to modify the flat pattern using offset like below. I had problems with this too, but that is another story. However I am trying to setup a template with parameters so all I need to change is the rectangle size, round diameter, and the height of the transition.

I could always simply increase the height by say 10 mm, and then reduce the diameter of the round. This would be more simple to calculate accurately if if was a square to round. But because the rectangle with short sides and long sides creates different angles, this is not so simple to work out. I did this on the last one, but got it slightly wrong, so the diameter of the round was too big. But ideally I would like to automate adding the extra using parameters if possible.

Re: Rectangle to round transition - how to extend the round a but further

TheCADWhisperer — Wed, 10 Jun 2026 00:36:11 GMT

@andrewsownemailPPGVB

Not possible without deformation unwrap.

Re: Rectangle to round transition - how to extend the round a but further

kacper.suchomski — Wed, 10 Jun 2026 00:51:08 GMT

Look at this:

(view in My Videos)

Re: Rectangle to round transition - how to extend the round a but further

johnsonshiue — Wed, 10 Jun 2026 18:05:34 GMT

Hi! I am wondering if Die Form option will work better in this case. Please take a look at the attached file.

Many thanks!

Re: Rectangle to round transition - how to extend the round a but further

andrewsownemailPPGVB — Wed, 10 Jun 2026 22:11:19 GMT

Thank you Kacper! This looks good, and appears to work well. I will go with this and let you know how it comes out this time.

The only thing that breaks the parametric side of it, is when I changed the circle diameter, I need to redraw the ellipse. on the projected round shape. And then reselect the ellipse as the top profile of the loft. Re-creating the loft then breaks the references for the flanges at the bottom of the rectangle.

Hopefully I am on the right track to working around that with this?...

To create a parametric ellipse that references projected geometry, you must use the Project tool with links enabled, capture the dimensions in the Parameters dialog, and build an ellipse driven by sketch constraints rather than just drawing it freely.

Re: Rectangle to round transition - how to extend the round a but further

andrewsownemailPPGVB — Wed, 10 Jun 2026 22:17:18 GMT

Hi Johnson, no this won't work as I am folding in a press brake. Besides it doesn't solve the actual problem like Kacper did of correcting the diameter of the circle as the height increased.

Re: Rectangle to round transition - how to extend the round a but further

andrewsownemailPPGVB — Wed, 10 Jun 2026 22:20:37 GMT

Is this a plugin or add on for Fusion?

What do you think of Kacper's solution then?

Re: Rectangle to round transition - how to extend the round a but further

TheCADWhisperer — Thu, 11 Jun 2026 08:07:05 GMT

@andrewsownemailPPGVB wrote:
What do you think of Kacper's solution then?

@andrewsownemailPPGVB

Attach your new file here based on @kacper.suchomski solution.

Re: Rectangle to round transition - how to extend the round a but further

andrewsownemailPPGVB — Mon, 15 Jun 2026 01:23:07 GMT

File attached. It wouldn't upload for some reason the other day/

I have found that if I change the size of the rectangle or the round (which therefore changes the shape of the ellipse):

The projected shape created from the top of the temporary surface loft body adjusts accordingly, but I have to redraw the ellipse.
As mentioned, a new ellipse means that a new loft profile needs to be selected, and then new flanges on the bottom, and also recreate the 20mm extrude for the lap to join each half.
Hopefully, I can eliminate having to redo these steps after a change in size.

Re: Rectangle to round transition - how to extend the round a but further

TheCADWhisperer — Mon, 15 Jun 2026 03:15:05 GMT

@andrewsownemailPPGVB wrote:
I want to extend the round up a by 10mm to give some extra material which will lap underneath the round spigot that will be spot welded on top (the lap then gets swaged).

This is the way that I interpreted the problem description. See Attached.

I did part of it (quick and dirty) for demonstration.

If this is the Design Intent - would still have to clean up the Flanges.

Re: Rectangle to round transition - how to extend the round a but further

kacper.suchomski — Tue, 16 Jun 2026 18:31:01 GMT

@andrewsownemailPPGVB wrote:

I have found that if I change the size of the rectangle or the round (which therefore changes the shape of the ellipse):

The projected shape created from the top of the temporary surface loft body adjusts accordingly, but I have to redraw the ellipse.

No, that's not true. What is true is that you shouldn't finish working on a sketch until it's fully constrained.

If you apply the appropriate constraints to the ellipse, there won't be any problems with updating – this is the advantage of parametric programs over direct modelers.

(view in My Videos)

Re: Rectangle to round transition - how to extend the round a but further

andrew2085 — Mon, 22 Jun 2026 16:07:35 GMT

You also need to watch out for when the round part is wider than one or both of the sides. Then the diameter of the 10mm extension gets larger, not smaller. You can handle all cases with a few equations to get the diameter of the 10mm extension.

Re: Rectangle to round transition - how to extend the round a but further

pkomatlapalli — Fri, 26 Jun 2026 15:58:28 GMT

Hi @andrewsownemailPPGVB ,

We would like to follow up on this issue. You have received responses from the following community members TheCADWhisperer , kacper.suchomski , johnsonshiue and andrew2085. Did any of these responses help resolve your issue?

If so, please click the "Accepted Solution" button. This helps other community members who may encounter the same issue in the future find the solution more easily.

Re: Rectangle to round transition - how to extend the round a but further

MichaelT_123 — Sat, 27 Jun 2026 04:16:57 GMT

Hi Mr AndrewSowneMailPPGVB,

Some time ago, I replied to the:

https://forums.autodesk.com/t5/fusion-design-validate-document/need-advice-to-sketch-squircle/m-p/11262861

You will find there "the smoothest transition(s) between circle and square" possible.

The rectangle will require an additional scaling step.

The math is quite simple; thus, for many (or even most, considering F360 users), it should be easy to implement.

Regards

MichaelT

Re: Rectangle to round transition - how to extend the round a but further

andrewsownemailPPGVB — Mon, 29 Jun 2026 05:41:05 GMT

Sorry, I only found out the result end of last week after we completed it. Kacper's solution worked a treat. I scored a 10 mm line down from the top and the edge of our round spigot matched it near enough perfectly! So thank you again Kacper.

On a side note, I never realised before that all the bends are slightly different angles on a rectangle to round transition. It takes a bit of time doing all the bends at different angles. Could probably get away with doing them all the same angle on a lighter piece but this was in .95 mm galv so we did it properly.

Re: Rectangle to round transition - how to extend the round a but further

andrewsownemailPPGVB — Mon, 29 Jun 2026 05:45:25 GMT

Yes I thought that would be possible. I haven't worked much with formulas in the parameters in Fusion yet, but will figure this out.

I had already done some experimenting with sides or the rectangle being larger or smaller than the round, and it did break the formulas I had in there.
Like 180°-D6 needed to be changed to 180°+D6 or something along those lines.

Re: Rectangle to round transition - how to extend the round a but further

MichaelT_123 — Tue, 30 Jun 2026 11:22:58 GMT

Hi Mr AndrewSowneMailPPGVB,

... for the sake of curiosity, I ran "flattening" on the squircle object as in:

https://forums.autodesk.com/t5/fusion-design-validate-document/need-advice-to-sketch-squircle/m-p/11...

The basic outcomes are in the attached file.

The "flattenings" were applied to two bodies: one representing a "progressive squircle" (n∈<2,10>)

and the other a loft between a circular base and a "squarish" square with parameter n=10.

Attached files:

Squircle_Fusculator_C.png 5K_mono ( 4MB) https://a360.co/4bjJkhk

Squircle_Fusculator_C.f3d F360 model (66MB) https://a360.co/4aNE6dN

Regards

MichaelT