Hi, I have built a direct extruder similar to this (http://www.thingiverse.com/thing:147705/#files), but I am using a j-head extruder and PLA filament. My problem is that, when I start with the extrusion, this makes fine the first two extrusion commands, but then the extruder motor starts to vibrate and it does not extrude. the sensation is as the motor does not have enough force, but I have seen other direct extruders with the same motor NEMA 17 and they works fine. I have modified extrusion speed, extruder motor (NEMA 17 3.4kg/cm2 and 4.8kg/cm2) and pololus driver adjustment, but I have no success. Please some help! Thank you very much! https://reprap.org/forum/read.php?1,294397,294397#msg-294397 Mon, 16 Mar 2026 01:20:51 -0400 Phorum 5.2.23 https://reprap.org/forum/read.php?1,294397,295504#msg-295504 https://reprap.org/forum/read.php?1,294397,295504#msg-295504 NEMA17 extruder that i designed paired with a Mk IV J-head to print with 3mm ABS routinely. When the j-head is working well, it can extrude at up to 150 mm feed/min. The trick is to use a small diameter filament drive. I use an 8 mm bolt that has been knurled with a v-groove mounted on the motor shaft which should be equivalent to the MK8.]]> brnrd General Wed, 15 Jan 2014 21:19:46 -0500 https://reprap.org/forum/read.php?1,294397,295322#msg-295322 https://reprap.org/forum/read.php?1,294397,295322#msg-295322 Ohmarinus General Wed, 15 Jan 2014 16:22:21 -0500 https://reprap.org/forum/read.php?1,294397,295035#msg-295035 https://reprap.org/forum/read.php?1,294397,295035#msg-295035
thank you very much for your answers. I just read this post from [www.thingiverse.com], which is probably the problem: the strengh is not enough:

Hi,
I am even not going to test 3mm filament with Nema17 :).
My rationale is that: average max torque of nema17 motors if ~0.45Nm, even with small drive gear with 7mm diameter we would have max theoretical torqe ~13KG. From my experience with 3mm filament and geared extruders torque ~20KG is needed, so when we substract gear train inefficiencies,..., and friction ~10% (because of direct drive extruder has no such gearbox:) ) we will have ~18KG. So it is why I have designed Nema23 version, you can easly get 0.6Nm which is not so heavy ~ 0,6kg, which fullfill such requirement.]]> aj.moreno General Wed, 15 Jan 2014 07:29:00 -0500 https://reprap.org/forum/read.php?1,294397,294458#msg-294458 https://reprap.org/forum/read.php?1,294397,294458#msg-294458 lazzymonk General Tue, 14 Jan 2014 06:47:46 -0500 https://reprap.org/forum/read.php?1,294397,294453#msg-294453 https://reprap.org/forum/read.php?1,294397,294453#msg-294453 thejollygrimreaper General Tue, 14 Jan 2014 06:40:27 -0500 https://reprap.org/forum/read.php?1,294397,294397#msg-294397 https://reprap.org/forum/read.php?1,294397,294397#msg-294397
I have built a direct extruder similar to this (http://www.thingiverse.com/thing:147705/#files), but I am using a j-head extruder and PLA filament. My problem is that, when I start with the extrusion, this makes fine the first two extrusion commands, but then the extruder motor starts to vibrate and it does not extrude. the sensation is as the motor does not have enough force, but I have seen other direct extruders with the same motor NEMA 17 and they works fine. I have modified extrusion speed, extruder motor (NEMA 17 3.4kg/cm2 and 4.8kg/cm2) and pololus driver adjustment, but I have no success.

Please some help! Thank you very much!]]> aj.moreno General Tue, 14 Jan 2014 05:16:06 -0500