Flaten objects

I’m searching for a flattening tool for objects like this:

By now I did this with a Fusion 360 plugin (ExactFlat). That worked pretty good but the licence is way beyond:

ExactFlat for SOLIDWORKS can either be purchased as a perpetual license at a cost of $13,690 USD or it can be leased for a cost of $4,995 USD per year.

With ExactFlat I have to select the inner surface. After that it gets flattened with a couple of clicks.

Is there another way of doing this? I think all the caracter designer do such things on a daily basis.


Export the STEP file and you can probably do a projection in FreeCAD. I’m still new to FreeCAD after Autodesk messed with licensing earlier in the year and threatened to yank STL export from the free versions. Previously I used projections in OpenSCAD to get my flat DXF files for laser cutting.

Joko Engineering does amazing CAD video tutorials for many CAD packages including FreeCAD. Highly recommend checking to see if he did one covering this topic before looking out in the greater WWW.


Maybe the FreeCAD SheetMetal Workbench?

FreeCAD has matured a lot recently, so you want to limit yourself to relatively recent tutorials if you can.

Here’s the beginning of a multi-part series:

Joko’s is a bit older but 0.18 isn’t that old yet.


Good point on looking for more current FreeCAD tutorials.

The OP showed a 3D part and was asking for ways to ‘flatten it’ which sounds like a 2D projection to either make a drawing with dimensions or to use for things like laser cutters or plasma cutting. But I see how you could also look at it as asking how to make it from a flattened sheetmetal.

Need some clarification on what “flaten object” means.

To be clear I have no experience with the SheetMetal workbench.

When I look at the bottom of its wiki page, I see a link to Macro Sheet Metal Unfolder which looks tantalizingly relevant.


The macro can unfold simple sheet-metal-parts. The parts must have everywhere the same material thickness as typical for sheet-metal-parts.


Select a flat face from your part in the 3D-view. Start the macro.

Doesn’t look like it has gotten a lot of attention lately.

As I understand it, if you design the part in FreeCAD SheetMetal Workbench, unfold capability is included. If you import it from somewhere else, I have no idea whether it works. The sheet metal unfolder macro hasn’t been touched and so would probably need to be touched up to work with current FreeCAD (just a guess).

It might be possible to use an imported part like that for external references to first make a native FreeCAD copy with the SheetMetal workbench, and then unfold. Or unfold might even work on the imported part!

OK, the suspense was killing me.

I just opened FreeCAD, created a sketch, put some folds in it in the SheetMetal workbench, exported as a STEP file, then in a new document imported that STEP file, clicked on a surface, and clicked Unfold. I chose ANSI K-factor and instantly I had an unfolded part.

@Kurt_Meister it looks like Unfold in the SheetMetal workbench will do exactly what you want, regardless of whether you design the part in FreeCAD or import a STEP file.


@mcdanlj Very nice find!

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@Kurt_Meister I’m so glad you asked this. It sent me off on a exploratory tangent abusing SheetMetal workbench for modeling plastic boxes. :relaxed:



Thank you @mcdanlj and @dougl for your replies. :slight_smile:

I’ll take a look at FreeCad and report back, whether it worked for me or not.


This part was designed with Fusion 360. No big deal: Just two bends and that’s it (for prototyping I often use acrylic and do the bends with a hot wire bender). And no, I did not use the sheet metal functions. Why? I don’t really know… :wink:

Today I exported the part as a step file and loaded it into FreeCAD. The flatten function worked just perfect and the sketch itself is nicely structured (outlines, cutouts and bend lines). Wow! :slight_smile:

So let’s get back to my initial job:

Unfortunately, this part can not be flattened (it’s not a regular bend). Then I tried to unfold it like this: https://www.reddit.com/r/Fusion360/comments/mle7lc/how_to_flatten_3d_objects_to_2d_for_cutting_and/gtkwnol/?utm_source=reddit&utm_medium=web2x&context=3

But somehow the function “Unwrap mesh” is not available. Hm, I got stuck…

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Heh, just last night I was bending acrylic (hot wire) for a part. I always figure the flat length and then leave extra to account for the bend. I make a wood mandrel to bend the plastic around and then trim the excess.

That said I always leave this thinking that there should be a way to calculate the actual material length with a bend allowance.

I have not tried the sheet metal tools in F360. Does F360 provide a bend allowance for acrylic?

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Looks promising! I just fired up Blender (for the first time ever) and did what the guy explained. It seems to work :slight_smile: How to make a paper model in Blender - YouTube


I think that F360, SolidWorks, and FreeCAD as well as others all use K-factor (the relative offset of the neutral line in the bend) to compute bend allowance and deduction. (It’s usually deduction because you are flattening a desired shape in common workflows.)

As I understand it, K-factor depends on tooling as well as material, so it’s kind of experimental, whether you are bending metal or plastic. Even for metals, you are starting with rules of thumb; 0.44 is commonly used for steel. I saw a reference somewhere to 0.2 for one plastic sheet. Must have been much more ductile than compressible!


Huh. Is it because the curve is a spline, or because the thickness varies?

Wow, nice find! Glad that worked for you!

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Correct, It’s a spline. The thickness is equal.

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