Rubber filament wheels

Hey all, I find that finding the proper filament feed tensions can be problematic depending on whether there is a a lot of retract in the print. To much pressure and stripping occurs. I'm running 2mm @ 40mm/sec retract. I was wondering if anyone has tested hob gears and bearings with a rubber coating instead of teeth. This should lessen the deformation of the filament. What do you brainiacs think?

Thing with much retract involved.
[www.thingiverse.com]

The only time I've experienced stripping was when the pinch roller pressure wasn't high enough. High pressure is needed so the drive gear teeth bite deeply into the filament, thus preventing it from slipping and grinding a divot into the filament. The motor should slip before the filament gets chewed up.

I recently discovered I had the pressure set so high it was crushing the filament, which made it easy to buckle inside the extruder. No stripping occurred.

I printed this with no stripping: [www.thingiverse.com]

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

Thanks DD. I'm using a tensioning arm that I printed. It flexes a bit. I may have to replace the arm with an aluminum one.

I reprinted my tensioner arm and after tightening I was getting some stepper clicking. I noticed that the shaft was moving while applying pressure to the hob. I think it's time for a better motor. Anyone know of a more solidly built Nema 17 motor. Price not important.

Any standard-length NEMA 17 motor should work. I use one like this, direct-drive with a MK7, but this looks a little stronger.

I use a 59Ncm direct drive extruder with a mk8 drive gear. No gearing, on a plastic extruder I designed myself. (similar to the design by Ffleurey on thingiverse, but designed to be smaller and stronger). This motor is probably overkill, most people use smaller especially if they use a geared extruder. I haven't had any problems so far, even on voronoi style prints. The only time my printer ground the filament, was when I had defective filament which had a large 4mm bulge in it, which got caught in the extruder.

Some people have used belts to run the filament instead, which would be a similar system to what you are proposing. Personally, I've not found the need to switch to one of these as my direct drive just works and is fairly compact compared to belt extruders. How much impact does deformed filament have on print quality? I imagine its mostly for efficient travel in the hot end. E3D states that a 1.75mm hot end can take filament from 1.65mm to 1.85, and anything bigger can cause excessive friction (and possibly under-extrusion as a result), but with a decent extruder the impact of large/deformed filament should not be a huge problem.

*EDIT*
some extruder designs that use belts

[plus.google.com]

[forums.reprap.org]

[0x7d.com]

Edited 2 time(s). Last edit at 06/11/2016 09:46AM by Origamib.

Thanks for the thoughts guys. The main problem I'm seeing is that the outer motor bearing allows way to much movement when pressure is applied. I was wanting to find a motor that has very high tolerances in this respect. Maybe with roller bearings. Thanks again.