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mk 8 direct drive for 3mm filament

Posted by Govahnator 
mk 8 direct drive for 3mm filament
February 10, 2016 08:10AM
Hi guys,

I know i opened a bulldog extruder thread, but this is about the mk8, so i made another topic wich makes the info more accessible to other people.

A friend of mine suggested to use a mk8 1.75 mm bowden extruder ( already bigger hole on top) to use with 3mm filament, is this a good idea and what kind of pulley do you guys suggest?
I have a NEMA 17 with a Holding Torque of 5.5Kg.cm laying around, would it be enough or do i really need a geared motor?

This solution would cost me 35 euro if i have to buy a geared nema as well, instead of 130 euro for a bulldog xl.

Edited 1 time(s). Last edit at 02/10/2016 08:29AM by Govahnator.
Re: mk 8 direct drive for 3mm filament
February 10, 2016 04:37PM
I happened to have tried this recently. In the mk8 I have the lower part of the hole in the arm for the filament is a bit tight for 3mm filament so I drilled it out a little. With the typical brass gear and the smaller nema17 motor that comes with the average mk8 clone I've been printing tpu and tpe fairly reliably. My attempt to print 3mm pla failed - the stepper motor stalls after a few minutes printing.

I have larger steppers and smaller diameter drive gears to try, but my suspicion is that 3mm pla will need a geared extruder. The smaller drive gears change the geometry and would need a new mount for the hotend with the hole closer to the stepper axis. I haven't tried 3mm abs yet as I don't have anything to store it in after I open the packaging.
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