fluidity bowden 1.75mm direct drive extruder.

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Summary There are many good struder designs out there, but I was unable to find the perfect fit for my needs. My requirements were very specific: I needed a 9mm x 4mm x 4mm thick brushless motor bearing that could handle heavy loads. (http://hobbyking.com/hobbyking/store/__10201__HK_500GT_Ball_Bearing_9_x_4_x_4mm_Align_part_H60103_.html) I required a 10mm fine pitch bowden clamp for tube that would fit snugly onto a 4mm OD tube. (http://www.robotdigg.com/product/348/Heavy-duty+push-fit+bowden+connector+4-01) I needed a long direct drive 400 step per rev low voltage Nema 17 stepper motor with plenty of torque. (http://www.omc-stepperonline.com/9deg-nema-17-bipolar-stepper-44ncm623ozin-17hm191684s-p-12.html) The struder had to be side mounted. I spent the weekend tinkering and finally got it working perfectly. I was thrilled when it printed out a flawless first-time print! To accommodate 1,75mm filament, I minimized clearances around the compression path to enable printing with Ninjaflex and other flexible filaments. Be sure to insert a stiff spring between the base nipple and the swing arm nipple to press the roller and filament against the pinch roller. This uses a 10mm diameter pinch roller - don't over-tighten the grub screw until you've fed some filament through the cavities to hold the pinch roller in place. Note that the swing arm has built-in bridge support, which needs to be removed before installing the bearing. Also, reduce your motor current slightly before fitting the stepper motor with extra length for great torque. To assemble the struder, use: 1 x M3 x 16mm bolt with an M4 nut as a washer 3 x M3 x 8mm bolts 1 x M4 x 10 bolt for the bearing If you can't find a pre-made spring, you can wind one from piano wire. My spring has an outside diameter of 10mm, a wire diameter of 1.24mm, and an uncompressed length of about 19mm.