inspired by: https://www.youmagine.com/designs/um2-feeder-on-um1
for use with: https://www.youmagine.com/designs/alternative-um2-feeder-version-two

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UPDATE (v4.0):
for this version, which is even more silent than version 2.0, you only need 4 fan dampeners like those: http://www.amazon.com/GELID-Solutions-Silicone-Vibration-Dampening/dp/B003Q5GI2U

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UPDATE (v2.0):
i updated the design and uploaded a new model with dampers (you need three dampers 15x15mm  - M4 and three screws PH2 M4x10mm), works pretty good so far ;). i also added a picture that compares the noise before the dampers where installed and afterwards, it doesn't look much but it is and it also is way more silent than the original feeder.
i recommend a 1.2mm walls and infill around 25%, no support is needed since it is integrated at the model files (only true for damped version)

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Since the original version didn't fit for me, i redesgined the um2 feeder adapter for the um original.
This one was a perfect fit at mine - it's also super rigid as you can see at the following video (printed with 0.8 shell, 30% infill, "support everywhere"!!!):

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I reach up to ~12mm³/s without any underextrusion (see picture above).

update: since I now calibrated my feeder I reach now up to 18mm³/s , didn't tried more so far...

The E-steps per mm for an Mk8 drigear should be around 365 as I read, since I am still waiting for my 400steps/rev. motor I cannot confirm that. At the original stepper it is much lower (but the original motor does not work for high quality prints - 1.8° steps are just too unprecise!).

update: the stepper arrived and 340 works very fine for me! (see here for more information: http://reprap.org/wiki/Triffid_Hunter%27s_Calibration_Guide/de)

update2: i was still extruding way too much! 302 is perfect now, to calibrate for the first time do the following:
- pop the bowden tube out the hotend
- preheat PLA (to activate the extruder motor)
- extrude a bit until you can mark the filament at the bowden end
- let it extrude 10mm
- mark again and measure as accurate as you can
- new E-steps = old E-steps * (10/measured mm)

I also recommend some rubber washers between motor and the adapter to further minimize noise (it is very quiet compared to the original!). you can also use a selfmade silicone-damper as me:

https://www.youmagine.com/designs/nema-17-silicon-damper-stencil

As an UMO-user you will not have an clamp for the feeder, I suggest that one:
http://www.thingiverse.com/thing:46318