Abstract: A switching device for double nozzles of a 3D printer, which includes two transmission blocks, a rotary part and two spring parts. The two transmission blocks are in mirror image structures with each other and are respectively mounted on two nozzle devices; each transmission block is provided with a pressure supporting and transmiting portion, and the pressure supporting and transmiting portion includes a pressing-down stopping portion, a pressure transmiting portion, and a restoring stopping portion which are connected in sequence; the rotary part is connected to the case and is provided with two pressing parts; the two spring parts respectively sleeve the two nozzle devices, and the spring part supports the corresponding transmission block; the rotary part can rotate in a reciprocating manner, the rotary part drives the pressing parts to move on the two pressure supporting and transmiting portions.

Abstract: A throat structure for a 3D printer according to an embodiment includes a cold zone for heat dissipation, a hot zone for heating, and a thermal insulation zone. The cold zone for heat dissipation has a titanium throat outer tube body and a teflon throat inner tube body, and the teflon throat inner tube body is socketed in the titanium throat outer tube body. The hot zone for heating has a heating block connection zone and a nozzle connection zone. The heating block connection zone is located on an external side of the hot zone for heating, and the nozzle connection zone is located at a lower part of the hot zone for heating. The thermal insulation zone is connected to the titanium throat outer tube body such that an area of the hot zone for heating is reduced and a printing material extrusion amount is controlled.