prusa i3 carriage adapter bulldog xl extruder 3d printer extruders 1440 1440a 30mm fan mount shroud 40mm fa 40x40 40x40mm 40x40x10 5v servo 6v abs active cooling air duct bed leveling bridge bridging cable cabletie cableties ties cad draft 1 e3d e3dv5 e3dv6 shoud fits hotend elastic band snap mechanism extrusion extrution fanduct faster file files fit future proof proofed proofing upgrades gear geared gears iteration 2 3 learcnc lm8luu lm8uu m3 15 maglev mechanical micro mini module modules system mounting plate part parts power increase printed probe prusa3 prusai3 rework reprap reprapdiscount rubber servoless stutter sldprt solidworks speed spring stl sub sub-micro submicro tgy tgy-1440a turnigy upright x-carriage xcarriage