I want to 3d print a model I made using mineways. The print fails because the model is hollow though and I need to fill it. There is a post asking for something similar to what I am asking but I want to keep the color of my statue too. I wanted to voxel remesh my object but when I do it comes out solid green.
You cannot 3D print non-manifold geometry. Go into Edit Mode and then menu Select > Select All by Trait > Non Manifold. It will select all non-manifold edges which you have to fix. There are around 100 edges in your model that are non-manifold.
An object being hollow is not the issue. For as long as your mesh is airtight, it will get printed as a pure solid (wasting a lot of material) like the Default Cube on the left unless you have explicitly modeled it to have hollowness like in the below example on the right where you can see it in x-ray mode having thickness inside. Just make sure the Face Normals are facing in the correction direction as seen in the cross-sectional view. So your first option would be to create an interior so it has some thickness which can also save you alot of material when printing.
The other option is to separate the 2 cubes by giving them their own separate edge which isn't shared. What you can do is select the shared vertex and go into menu Mesh > Split > Faces & Edges by Vertices. This will create 6 vertices overlapping each other. To visualize how that looks like I have explicitly moved them apart. You need to join the encircled vertices back together. Just be careful that you don't accidentally merge the 2 resulting merged vertices back together when you do a AM > Merge By Distance operation.
Unfortunately, it looks like you also have internal faces which is also non-manifold. Read more about non-manifold geometry here.
