How to get the upper X% of an object and remove the rest I have been messing around with my 3D printer quite a bit and nowadays my prints usually work out well. I sometimes still have failed prints though, and in this case a 5 hour print failed just a bit over half of a print. I wish to simply reuse the bottom part which was printed (so my time wasn't a complete waste), and just print the upper part.

That's why my question is how I can remove a certain known percentage of the full 3D object, so I can export the remaining part with the same scale as the original and simply glue them together after. In this example, I estimate a good 200/375 layers (of 0.3mm, first one 0.35mm) were finished, so 53.333..%
One way is with a boolean modifier.


Add a plane (&#8679; ShiftA> Mesh > Plane) and make it large enough to exceed the bounds of the target object.
Add a boolean modifier to the target object and specify the plane as the second object:



Also ensure the boolean operation is set to Difference or Intersect.
This plane can be moved around and the mesh will be cut and filled accordingly. By using the dimensions of the target object, it's not difficult numerically place the plane in order to remove e.g. 75% of the object:


Which side of the mesh is removed can be controlled by flipping the normal of the mesh (&#9096; Ctrl&#8679; ShiftN) in Edit mode (&#8633; Tab), or by switching between Difference and Intersect boolean operations.