Disclosed are embodiments of a three-dimensional (3D) printer for building 3D objects with layer based, additive manufacturing techniques. The hot end can be moved in a horizontal plane parallel a planar printing surface of the printing bed while the printing bed can be moved perpendicular to the planar printing surface to print a 3D object. The hot end can be part of an extrusion guide assembly. The 3D printer can auto-level the printing bed.