The below settings can be used to fix errors in models that are not properly designed for 3D printing. These models usually look good in the solid view, but if there are faults these are often shown as red areas in the X-ray view.
Union overlapping volumes
If a model contains two volumes that interfere (as if they were placed through each other), this setting allows you to fix that. Union overlapping volumes will recognize these interferences and try to slice it as one volume.
These two cubes overlap and produce invalid geometry by default. From left to right: solid view, x-ray view, “Union overlapping volumes” disabled, and with “Union overlapping volumes” enabled
Remove all holes
Solid models that contain unnecessary holes on the inside can be repaired by enabling the “Remove all holes” setting. Ultimaker Cura then closes the holes for slicing and makes sure the inside is printed correctly.
This cube is hollow and will take longer to print than just making it solid, because of the extra walls. From left to right: solid view, x-ray view, “Remove holes disabled”, and “Remove holes enabled”
When polygons are missing in the shell of the model, Ultimaker Cura won’t be able to slice the model correctly. In this instance, you will see faults in the shell and/or infill in the layers view. By enabling “Extensive stitching” holes in the shell will be closed so that it can be sliced as expected.
Keep disconnected faces
Models that contain holes on corners are ignored by Ultimaker Cura. It’s impossible to know how the missing geometry should look. With this option enabled, Ultimaker Cura connects all neighbouring geometry to close the model.
This model is missing geometry that connects to multiple neighbouring polygons. Without knowing this should be a cube, Ultimaker Cura cannot connect the faces, and therefore produces nothing. From left to right: solid model, x-ray view, and “Keep disconnected faces” enabled
Merged meshes overlap
This setting creates an overlap where merged models meet. The result is a slight over-extrusion on the joining areas, which can improve adhesion between the two parts. Keep this setting low, between 0.0-0.2mm, to prevent too much over-extrusion.
Remove mesh intersection
Ultimaker Cura detects if meshes loaded on the build plate overlap. If they do, Ultimaker Cura partly removes one of the meshes to prevent extruding double on those parts.
Alternate mesh removal
When Ultimaker Cura detects overlapping meshes, it normally removes one of the meshes completely. With this option, the meshes are alternatively printed layer by layer, creating a woven mix of the two.
Continue reading about Special Modes settings.