MK2 Idler / Ninjaflex doesn't feed
I had some problems printing some very flexible materials like NinaFlex. When I looked more closely at the idler, i saw that the axis of the ball bearing is 1 mm higher than the axis on the extruder motor. Because the hinge screw of the idler is also one of the fixing screws of the motor with a distance between the screws of 31 mm, it should be exactly half of that distance, 15.5 mm. Measured off the STL of the part, it is actually 16.4 mm. This offset tilts the filament squeeze axis and I think this is why the filament get squeezed past the tube of the hotend. I copied the design and fixed that, but haven't tried it out.
Part download: https://www.thingiverse.com/thing:2559899
Re: MK2 Idler / Ninjaflex doesn't feed
And have you proceeded using the recommandations from the Prusa manual, that for printing soft flexible materials you should loose the idler screws so its not pushed by the springs?
Re: MK2 Idler / Ninjaflex doesn't feed
Yes, of course. I did try several settings for the spring load, but i didn't got it entirely reliable. Oftentimes it feeds ok for half the print and then it jammed, thus ruining the print. I have all the parts ready to upgrade the printed parts of my x-carriage to Mk2S and while doing that, I can make two pictures from "behind", showing the issue of sproket and ball bearing position better.
Re: MK2 Idler / Ninjaflex doesn't feed
I am now updating the X-Axis to MK2S, so i disassembled it. Thus, I could make a picture from the idler, reverse view. You cannot see it on the first glance, but the axis on the original black one is slightly to high. It is easily calculatable from the distance of the motor mounting screws and measurements of the 3D-model. The new red one is made with the exact measures. Also, the pulley was slightly misaligned in Y-direction and I fixed this too. I'll update after I have printed some NinjaFlex in the future.