Make Solid generates weird strings and pillars + degrades mesh

[Anonymous]

Hello everyone, I'm trying to set-up a mesh that was free for download from the internet, so that I can 3D print it. The issue I find with Ultimaker Cura is that some parts of the mesh are empty, or so they look in Cura. To understand what I mean, just have a look at the leg on the right as compared to the leg on the left. 

I googled to find a solution and found out that Meshmixer has a Make Solid option. Hopefully, this will fill the inside of my mesh for a better 3D printing, I thought. But I dunno if that's what I needed to do and when importing the mesh in Meshmixer and trying to apply the Make Solid tool, I get these awesome problems.

There are the horrible results I get when trying to apply the accurate option. The model degrades to awesome extents.

This is what happens with the "Fast" option selected. Absurdly, the results are better looking but look at those strings all around the hands and the body! Can't understand why this happens. As you can see I tried to play with settings but nothing solved my problem. How can I keep a perfect resolution, no stringing and just fill the inside of my model so that it is 100% solid? 

In the last screenshots, I'll show you how my model really looks like before I try and apply any meshmixer "make solid" tool. 

[Anonymous]

There seems to be something wrong with normal directions of interior shells...

Can you post the link to download that model?

[Anonymous]

Sure thing, man! Thanks for the reply and for your help, here it is: https://www.dropbox.com/s/jtyua1p8ycescxw/Valentine%20WIP%20thicker%202-2-meshlab_netfab_meshlab.stl...

I tried to follow a number of tutorials on how to heal, fix and prepare my mesh for printing using Meshlab and netfab. So, for example, there should be no holes. And I used Blender to make the thinner parts way thicker than the original model. I had to do it for hair and dresses and it worked, at least now every part of the model looks printable in Ultmaker Cura... but I still have those weird infills. That's why I tried to use Make Solid in Meshmixer. 
In any case, this problem made me know about meshmixer. It really looks like an awesome piece of software, will definitely try and learn more about it. 

[Anonymous]

This model comes with 400+ not connected surfaces. Most of them you do not need at all and cause that unexpected behaviour of MakeSolid.

To get rid of not needed stuff:

-Run EDIT/SeparateShells to split the model to its elements.

-Now activate all objects (press Shift and click) you need to describe the outer surface.

-Run EDIT/Combine to join them to one object again.

-Activate all other objects (best to do a multiple selection in the ObjectBrowser) and discard these.

There's still an issue at the gloves and the hands:

- Select some faces on both gloves and hit Y to separate them

- Hide the gloves

- Select the surface of a hand plus a bit of the arm and run Edit/Planecut on that selection to cut off the hand at the wrist (later on: inside the gloves). 

Show the gloves and hide the rest. The gloves are hollow. 

- To split its interior surface from the exterior: Select a ring of faces where the exterior changes to  interior .

- Discard that ring

- Select some faces on the interior part and hit E to expand the selection to connected faces. The result should show only interior faces selected.

- Hit X to discard the interior part.

- Run Inspector to close the hole on each of the gloves.

Now show all again an activate gloves plus the rest and run EDIT/Combine.

MakeSolid should do its job now properly.

A problem will be the blade of the saw in the backpack.

You might need to set a higher MeshDensity and SolidAccuracy than the sliders maximum. You can do this via numerical input at costs of file size and computation time.

or

Separate the blade before doing MakeSolid on the rest. Now activate the solid result plus the blade object and run BooleanUnion.

[Anonymous]

Thanks for the super detailed answer. To try it, I need to learn more about the program... I'm trying to see if it works right now.