US Patent 11745422 3D printing apparatus and method

An embodiment fused deposition modeling (FDM) type 3D printing apparatus includes a printing bed having a space for printing out an output on an upper surface thereof and a nozzle unit provided on the printing bed and configured to extrude a molten output material and print the molten output material out to the printing bed, the nozzle unit including a primary nozzle tip configured to primarily extrude the molten output material and a secondary nozzle tip selectively coupled to the primary nozzle tip and configured to secondarily extrude the molten output material.