geared extruder over MK8 design

I've been working on an extruder design, and I've been wondering about the current extruder designs and what the benefits or short comings are in each as it relates to output power, and the ability to feed filament.

My focus is on the MK8 design, and the use of a standard NEMA17 motor. But I question the torque that set up has, as other designs use a geared setup, which
I assumed was for adding torque and reducing speed for control. but I have not heard anyone say the MK8 design lacks the power to feed.

Just wondering what opinions people have on the different designs and what would be the drawbacks in using a standard NEMA17 might have?

See [forums.reprap.org] for my take on this. In summary, for 1.75mm filament you want either a direct drive extruder with a long Nema 17 motor run close to its rated current, or a short Nema 17 motor with gearing between 3:1 and 5:1.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

I tried using a MK8 setup with 3mm filament and found it a struggle with the short motor that came with it. I toyed with the idea of using a bigger motor but wasn't keen on the extra weight, so I went with a geared design instead. I'm hoping I can scale it down to use nema 14 motors and still have enough power, but we'll see if that works out when the motors arrive. I do like being able to swap out the hot end and be up and running with either 3mm or 1.75mm filament fairly quickly. I'm hoping to build up a collection of quick change hotends with different nozzle sizes, and then I'll always have a spare handy if one gets blocked too.

Guess I could have included that it is for 1.75 only, and it will be a bowden setup,so torque may be more of an issue. But then I'm not worried about the weight, so a longer motor is not a concern
Thanks dc42..that is good info.

I'll ask again later

Edited 2 time(s). Last edit at 03/10/2016 04:34AM by MechaBits.