topic Re: Wrap flat surface around curved lines or loft with sheet bending constraints in Fusion Design, Validate & Document Forum

Wrap flat surface around curved lines or loft with sheet bending constraints

Anonymous — Thu, 30 Jan 2020 23:51:52 GMT

Given two curved lines in parallel planes, and flat sheet (for example paper or 1 mm veneer in my case), I need to wrap that sheet around those curved lines. Sheet wrapping without creases forces constraint that distance on surface between any two points remains the same in plain and wrapped surface.

Loft can be used to make surface that connects those lines, (I tried some options as beginner) but loft creates surface that can't be made from sheet of paper because loft surface violates sheet wrapping constraint that distance on surface between any two points remains the same in plain and wrapped surface. If you look at surface generated with Loft from front (left upper corner below), then you can see curved silhouette on sides, which should be straight if it could be made from sheet of paper.

To be sure I printed surface on 3D printer and used paper sheet to wrap it around such lines, and it can be done for sure. Red line below to show curved silhouette which is wrong, green line shows that wrapped sheet create stright sillhouette line.

Could anybody suggest best way or best workaround how to achieve such kind of sheet wrapping around two curved lines in Fusion 360?

Fusion 360 test project is available here - sample test project

Re: Wrap flat surface around curved lines or loft with sheet bending constraints

wmhazzard — Fri, 31 Jan 2020 03:54:14 GMT

You could try adding a couple more guide rails between the curves to eliminate any compound curve.

Re: Wrap flat surface around curved lines or loft with sheet bending constraints

Anonymous — Fri, 31 Jan 2020 23:22:15 GMT

I found correct terminology - I'm looking for developable surface or ruled surface feature in Fusion 360. I'm looking whether there is a way how to automatically make such surface between two curved lines in Fusion 360.

I suspect it is not possible manually calculate / make correct guard rails for loft that would result in developable or ruled surface.

Re: Wrap flat surface around curved lines or loft with sheet bending constraints

TheCADWhisperer — Sat, 01 Feb 2020 12:49:01 GMT

File>Export and then Attach your *.f3d file here.

Are you a student?

Do you have access to Autodesk Inventor Professional with Lofted Flange sheet metal functionality?

How close of tolerance do you need?

Will Autodesk MeshMixer - Unwrap functionality be close enough?

Re: Wrap flat surface around curved lines or loft with sheet bending constraints

Anonymous — Sat, 01 Feb 2020 16:42:59 GMT

> File>Export and then Attach your *.f3d file here.

File attached. It is simple minimal sample project as I real project has parameterized design to explore different parameters in search of final design.

> Are you a student? Do you have access to Autodesk Inventor Professional with Lofted Flange sheet metal functionality?

No, I'm hobbyist. Currently started to experiment with 3D printing and design from bent plywood (glueing veneer sheets) on my own. Wanted to learn and usee some 3D CAD program, which wouldn't cost an arm and a leg if I would need to buy commercial license at some point. Fusion 360 fits the requirements except creation of developable surfaces. Inventor loftend flange sheet metal feature sounds like means to create developable surfaces, but subscription fees are not for hobbyists for sure 🙂

> How close of tolerance do you need?

1mm paper should bend into surface without problems. I'm not sure how it transslatees to tolerances. I guess sub milimiter.

> Will Autodesk MeshMixer - Unwrap functionality be close enough?

I guess, if there is no way how to do what I need in Fusion 360, then anything will go.

Thank you

Re: Wrap flat surface around curved lines or loft with sheet bending constraints

TheCADWhisperer — Sat, 01 Feb 2020 17:15:45 GMT

You can UnWrap your surface in free Autodesk Meshmixer and then bring back into Fusion 360.

Re: Wrap flat surface around curved lines or loft with sheet bending constraints

Anonymous — Sat, 01 Feb 2020 17:50:19 GMT

Thanks. I will try Meshmixer. Unwrapping is nice to have to see exactly what ar dimensions of input materials, although bounding box can be roughly estimated manually (bend plywood after glueing is processed and extra material removed anyway).

Now I'm down to question - does loft feature in Fusion 360 always creates 'C' and 'O' shaped developable surfaces if closed or unclosed 'C' or 'O' shaped lines on both ends are defined? Such developable surface exists for sure, but is loft creating such surface? That would be perfect if that would be the case with loft under conditions above.

Re: Wrap flat surface around curved lines or loft with sheet bending constraints

TheCADWhisperer — Sat, 01 Feb 2020 17:55:22 GMT

Fusion 360 Sheet Metal - Flat Pattern is limited to Planar geometry with Cylindrical or Conical bends.

No warped/twisted faces, even if they are developable.

Part of the reason is the function calculates Bend Allowance.

A sheet of metal compresses on the inside of a bend and stretches on the outside of the bend.

The neutral plane (no compression or stretching) is usually not at the midplane of the thickness.

Fairly easy to calculate for cylindrical/conical bends.

Re: Wrap flat surface around curved lines or loft with sheet bending constraints

Anonymous — Sat, 01 Feb 2020 18:14:33 GMT

I understand that there are limitation to sheet metall in Fusion 360. My use case with bent plywood starts from splines on end form (minimal constrains) and then creating developable surface between them. So, to rephrase my question:

Given curved lines on both ends of 'C' or 'O' like surface, does loft (with connected profile types) creates developable surface (which exists for sure).

As understand correctly, developable surface should have zero Gaussian curvature, which unfortunatelly is not the case:

I guess I answered my question - loft feature in Fusion 360 doesn't create developable surfaces. It is possible to do that with Autodesk Inventor Professional and its Lofted Flange sheet metal functionality.

Any workarounds or creative ideas with Fussion 360 or other tools? Probably guide rails for loft, but I can't imagine how to manually calculate them, so not really an option for parametrized design.

Re: Wrap flat surface around curved lines or loft with sheet bending constraints

TheCADWhisperer — Sat, 01 Feb 2020 19:26:07 GMT

I don't think with plywood your tolerances are going to be so tight that you can't get a good enough flat pattern (Unwrap) washing through Meshmixer. It is really very easy to go through Meshmixer and back to Fusion.

Bottom line, you are not going to get a Flat Pattern in the current version of Fusion 360.

Re: Wrap flat surface around curved lines or loft with sheet bending constraints

Anonymous — Sat, 01 Feb 2020 22:16:52 GMT

There are some option when creating loft, it would be perfect to have option checkbox 'developable surface' when creating loft surface. But I guess not today and not tomorow, if at all 🙂

Thank you again for your answers and help.