Software cant slice multi part models correctly

[PrintorMahn]

Hi there, I've been using S3D at uni and i like it and am thinking of buying my own licence but have been having trouble getting the software to print the kinds of things I use a printer for.

when a model is made of multiple objects it just fails to prepare the model correctly, it generates interiors and holes and the "Merge all outlines" tool either fixes the holes but adds random surface planes, or just doesn't change anything.

the first pictures are this http://www.thingiverse.com/thing:441087 model with base settings
the next is with "Merge all outlines" and you can see it plugs the nose hole and adds base floors to the eye sockets for some reason.

te last two is this model http://www.thingiverse.com/thing:758165 and regardless of what is selected, the overlapping internal parts make it go haywire and generate holes.



Cura slices them fine but lacks manual supports and the level of customization so I'd really like to use S3D, but I just cant get it to work with multi part models

any thoughts?

[CompoundCarl]

The software expects a real valid water-tight 3D model. If you have multiple self-intersecting parts in your STL file, then you need to fix that first before you try to slice. They have a nice built-in option that can help with this. Just go to Mesh > Separate Connected Surfaces. That way, each separate 3D solid in your STL file will be broken out into it's own item on the models list. Then it will slice correctly.

Here's a nice video about this option if you haven't used it before: https://www.youtube.com/watch?v=g1V-5aA03dQ

[PrintorMahn]

Wow, thanks that is exactly the right thing, that fixed it perfectly for all of the models I can find.

You can probably guess, that I"m a student, so that said; if you don't mind my asking, why does it work?

[CompoundCarl]

I'm not sure what to say besides what I already wrote above..

Your model had lots of self-intersecting overlapping meshes inside it. The software expects a file that is a true water-tight solid (i.e. cannot include non-manifold and self-intersecting surfaces). So by splitting apart the mesh into separate connected bodies, you are now providing each model as a valid water-tight solid instead of one giant jumbled mess.

[dkightley]

Allow me to try and provide a simplified explanation as to what Carl is saying.....

Lets take a couple of intersecting cubes:

These two cubes have been drawn as separate meshes. Export the two meshes together into an .stl file and then import into S3D and they look the same:

That is until you slice them:

What is happening is that where the two cubes intersect, the wall of one cube is interpreted as the wall of the other cube...and vice versa, resulting in each cube having a chunk missing and there being an included void. If this was to be printed, it may hold together...but would break apart very easily.

Now, by using the option Separate Connected Surfaces, the one object with two meshes is separated into two objects, each with a single mesh. The slicer in S3d sees these as two separate meshes and combines them before commencing the slicing......ending up with one solid object. See next post for image....

[dkightley]

See text in preceding post......

[PrintorMahn]

Riiiiight I understand now, thank you.
So other software like cura just does that automatically and i guess would mean you wouldn't have the option to print something with specific internal voids, like what S3D creates.