The document discusses various hardware and mechanical components of 3D printers. It mentions bed leveling techniques like contact strain gauges and inductive bed leveling that help compensate for an uneven print bed surface. It also discusses features like filament runout sensors, power loss recovery, and multi-material printing capabilities through the use of single or multiple nozzles, hotends, and extruders. Finally, it brings up 3D printers that have more than 3 degrees of freedom (DOF) of movement and tool changers for different print heads or nozzles.