T.U.B.E - The Ultimate Bowden Extruder

thingiverse

The idea behind this remote direct drive extruder is to use the filament itself to simultaneously push and pull the extruder gear. I tried to keep all the qualities of a bowden extruder (deported weight) without the weakness (filament compression). For this to work, two gears are required: the motorized and the follower. The follower is placed above the hotend on the carriage and the motorized is placed away on the printer frame. This one is pulling the filament that is already inserted through the follower, making it rotating. The filament then goes out of the motorized before being reinserted the other side of the motorized and pushed through the already rotating follower gear. Like a direct drive, a gear, the follower, is pushing the filament just above the hotend so it should in theory have the same behavior than a classic pseudo direct drive extruder with a small length of ptfe. Contrary to a classic bowden where more and more filament is inserted until maximum compression in the tube, the length of filament can only stay constant between the two gears. The length of filament on the pushed side can not compress in the ptfe tube because it is retained by the length of filament on the pulled side that is way more difficult to elongate. The motorized and the follower are basically the MK8 extruder upgraded with the following benefits: - Spring compression adjustable: - Dual grip with a single gear - The filament is gripped on two sides of the same gear so the grip is doubled in the limit of the input torque - No backlash - Spring is not linked to the ground but on the two opposite sides of the drive gear: - If the gear is off-center the spring compression will remain constant and levers will just follow the excentration. A cheap gear can then be used because the off-center defect is always reduced to zero. - I also adapted the following belted 2:1 reduction drive that helps smoothing the extrusion. It would be even better whith one of those Moons nema 17: https://www.thingiverse.com/thing:3001234 This the TUBE extruder. It is also convenient because it relies a lot on ptfe tube like classic bowden. It would not work without it keeping a constant filament length in the extruder.