UPDATE: As per several requests I've made a mirrored form of the 30 mm and 40 mm ducts. They are labeled as "Mirrored" and mount the 40 mm duct on the left side of the E3D hot end.
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Here is a revision to my E3D v5 hotend duct (http://www.thingiverse.com/thing:254004) for a MakerGear M2. Even though this is made for the M2, several folks have told me they’ve been able to implement this on other brands of printers, most notably Robo 3D printers. If there are others that this works on please let me know and if there are specific changes you would like to make this design work better for your printer, don’t hesitate to post a request.
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I recently made a duct for the E3D v6 (http://www.thingiverse.com/thing:494430) and made a number of design improvements. For those people that haven’t made the upgrade to the E3D v6, I translated the design improvements to my v5 duct design.
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The extruder is for 1.75mm filament and I’ve made two versions of the extruder, one to fit 2.0 mm I.D. PTFE (at the top) and one to fit 3.0 mm I.D. PTFE. The reason for the later is because 3.0 mm I.D. PTFE tubing allows kinked filament to pass through this more readily. I’ve uploaded a version of each with and without supports / pads. Most of the supports and pads peel away easily or can be crushed and plucked off with a pair of needle nose pliers. Cleanup should be pretty quick and easy. I suggest that you pass a 2.0 mm diameter circular file down the length of the filament shaft of the extruder. Sometimes there are minor blockages that can lead to filament jams. This design was inspired by both rsilvers’ M2 extruder design (http://www.thingiverse.com/thing:267137) and cmenard’s adaptation for the E3D v6 (http://www.thingiverse.com/thing:349859). I’ve tried to fit the extruder to the hot end such that it seats very precisely and does not require much force but you need to come at it at the right angle. It holds the hotend very firmly (better than the E3D v6 extruder, which I’m currently revamping to fit better).
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I’ve also reduced the size of the restraining block on top of the 30 mm fan duct. This takes the geometry of the E3D v5 extruder I designed into account. I’ve posted ducts with labels on top so you can better keep track of your nozzle diameter if you have multiple hotends.
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I hope this works as well for you as it does for me. I immediately noticed a significant improvement in the smoothness of my shells and the consistency of extrusion. Please comment if you have any design suggestions or requested fixes.