Abstract: Extruders for 3D printing machines are disclosed, which are configured to print with fragile metallic filament substrates. The extruders include two rotating elements, each of which is at least partially cylindrical, with the two rotating elements being positioned parallel to each other (with a first of the rotating elements being configured to rotate in a first direction and a second of the rotating elements being configured to rotate in a second opposite direction). The extruders are operably connected to a transmission, which is configured to drive rotation of the rotating elements in the first direction and the second opposite direction. The extruders further include a metallic filament contact zone located in a cylindrical area of each of the two rotating elements, along with a flexible coating that at least partially covers the metallic filament contact zone. The flexible coating is configured to be removed and replaced by an operator of the 3D printing machine.

Abstract: Methods and devices for automatically cleaning a print head within a three-dimensional (3D) printer are disclosed. The methods generally include operating a measurement system (of a 3D printer) to measure an amount of material delivered to a print head of the 3D printer (on a per unit of time basis); detecting a disturbance in the material being delivered to the print head; and retracting the material and then re-introducing the material to the print head. The methods include having a first drive system and a second drive system being used to retract the material and, once the print head is cleaned, to re-introduce the material to the print head with increasing speed from zero to a pre-defined end point speed.