It is a fact of life that 3D printed parts from an FDM (fused deposition modeling) printer have weaknesses where the layers join. Some of this is due to voids and imperfect layer bonding, ...

The mantle is about 1,800 miles (2,900 kilometers) thick and appears to be divided into two layers: the upper mantle and the lower mantle. The boundary between the two lies about 465 miles (750 ...