Unfold Complex Surface

[Anonymous]

Can anyone help here? I'm trying to create a flat pattern on the attached windsail. Surfaces have been generated using MODEL commands & a thicken offset command of 1mm. I've then converted to sheetmetal & set the default thickness. I know Inventor can have issues with parts created outside of the Sheetmetal environment!

Does anybody know of perhaps any add-ins or third party software that could possibly handle this?

i'm using Inventor 2018 btw. Thanks in advance Glen

[Anonymous]

You have a 3D surface that can't be produced in a "normal" sheetmetal shop. Standard sheetmetal knows how to work with deformation along straight lines. To achieve your surface you need plastic deformation in more than one direction simultaneously. Think of a cooking pot. It can be produced out of sheet with deepdrawing. This in turn will need some intermediate steps depending on heigth versus diameter, material, thickness. All this is specialised stuff and out of scope for simple sheetmetal.

[JDMather]

@johnsonshiue

I made some changes to the original file and saved as stl.

I then imported the stl file into MeshMixer and selected Unwrap - but I did not get any results.

Can you create a Screencast recording demonstrating how to use the MeshMixer unwrap tool?

[johnsonshiue]

Hi JD,

I am not an expert on Mesh Mixer but I know the basics. I think the null op has something to do with grouping. The sail body was exported from a solid, instead of a surface. As a result, there are a few faces exported. Unwrap works best on a per surface basis. Try this.

Options 1:

1) After import to Mesh Mixer. go to Edit -> Generate Face Groups. It will sort of divide the faces.

2) Unwrap.

Option 2:

1) In Inventor, open the part.

2) Create a zero-offset surface on one side.

3) Make the solid body invisible.

4) Export the surface as mesh.

5) Import i to Mesh Mixer.

6) Unwrap.

Please let me know if both options work for you.

Many thanks!

[Anonymous]

Many thanks for the advise, this is the first I've heard of MeshMixer!

So I've exported as STL from Inventor & imported into MM, following your instructions I've produced a pattern of a sort?

I just now need to (a) Produce a solid on the flat pattern? & (b) produce a dwg or dxf of the profile for printing purposes.

I'm nearly there! Much appreciated!

[WHolzwarth · Accepted solution]

I think, conversion is not straightforward. Even the flattened shape still is a mesh, having lots of tiny faces.

Thanks for Jeffrey and Johnson, hinting at Meshmixer; I wasn't aware of the Unwrap feature there.

That's what I did for conversion:

- Saving as OBJ in Meshmixer

- Uploading the OBJ into Fusion 360

- Export from there as STEP

- Import of STEP into Inventor, surface Body1. still with lots of facets

- Silhouette Curve for outlines

- Patching outlines and holes to single surface

2018 IPT attached

[Anonymous]

That's brilliant, thanks so much for this solution WP  (appreciate all the helpful suggestions & support here)

I've learnt something that's going to be quite useful to me!

[JDMather · Accepted solution]

I made a video to document a workflow using Inventor and MeshMixer.

[Anonymous]

This most appreciated JD, thanks for taking the time to show this!

[JDMather · Accepted solution]

Once you get the flat into Inventor - you can right click on face to save as dxf file.

I also experimented in MeshMixer on simplifying the mesh to make the number of projections easier - but I don't know much about MeshMixer - so I did not show that in the video.

[Anonymous]

nice work! I wrote this Unwrap tool in Meshmixer, glad to see someone finding a use for it 😃

If you just want to print the flattened borders, Meshmixer can also export SVG: http://www.mmmanual.com/export-svg/

There are also various svg-to-dxf converters out there.

[pavmed]

Hi! 

Can I ask for some internals regarding Unwrap tool?

As we all know it's impossible to unwrap arbitrary surface to flat without any distortions.

What distortions are tolerated by unwrap? 

Or in other words - what it tries to preserve w/o distortion?

AFAIK there're 3 types of projections (i.e. algorythms that allows us to have flat image of non-flat object) -

1. equdistant

2. equiareal

3. equiangular

What is implemented in MM Unwrap tool?

And thank you for this tool!!

[pavmed]

@Anonymous Hi

Forgot to tag you in my previous comment 🙂

[Anonymous]

(all this is possibly incorrect because I haven't worked at Autodesk for several years and the Unwrap tool may have been modified)

the Unwrap tool doesn't use projections, it solves a nonlinear numerical optimization problem (basically a PDE) over the mesh triangles to find a flattened version that minimizes a distortion metric. So, it doesn't precisely preserve any of the properties you mention, like say a spherical projection would. There are generally no guarantees on distortion bounds with these kinds of methods.

There are various algorithms for doing this, each one has different properties. If I remember correctly, there are several implemented in the Unwrap tool. The conformal one is trying to preserve angles, and the rigid one is kind of trying to preserve lengths (preserving areas is usually kind of meaningless because you can do arbitrary shearing of a triangle and still get the same area). You could try googling "As Rigid As Possible Mesh Parameterization", you should find an academic research paper that will give you a sense of what these things mean.

[Anonymous]

Thank you for your work making this software. I wish it was more open to work with AutoCAD but A coworker and I worked through turning the edges of the flattened shapes back into lines. Thanks all for your contributions on this post. I hope Autodesk can incorporate tools like this into many of it's software packages.

[Anonymous]

I follow you video intensely.  For some reason I can't Project Geometry.  

Thanks for your time making this video.  I achieved the flattened pattern as intended.

Tony

[JDMather]

You must have the AutodeskMeshEnabler installed.

If you have trouble getting it - post back.

Correction - you do not need MeshEnabler for this.

Simply start a new 2D sketch on the XY plane.

I had a little trouble with two coincident points in the sketch not meeting up and had to use Stitch of surfaces.

(See Attached.)

[jacques]

Well, I tried this, input was a shape measuring roughly 1.2mX0.6m and I got back a flat shape measuring roughly 68mX25m... not exactly a solution to the problem...

[JDMather]

Sounds like you did not properly handle Units.

Attach your file here and end all doubt.

(BTW - this is an old thread, there is now an easier way.)

[jacques]

If there is an easier way, I would be glad to hear it. Meanwhile, here is the original part and the end result.