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The 0.8mm filament experiment

Posted by o_lampe 
The 0.8mm filament experiment
March 27, 2018 09:22AM
Hi everyone,
as we know, the step from 3mm to 1.75mm filament changed 3DP a lot. I always thought, it could get even better with thinner filament. Mostly reducing extruder weight is the goal in this experiment.
I started to make my own 0.8mm filament, simply by extruding 1.75 filament through a 0.6mm nozzle, while the printhead made continuous circles.

Why 0.8mm? It fits nicely in 1mm ID PTFE tube and I could easily modify a 0.4mm nozzle with a brass tube of 2x0.5mm.
So I took a MK8 direct drive extruder, pushed the 1mm ID PTFE tube into the standard 2mm ID PTFE tube of the heatbrake.
The drive gear had way too much pressure and almost bit through the filament, so I took a smaller drive gear and added two layers of shrinktube. I also had to replace the grooved idler gear with a flat one.
A NEMA17 1.7A motor had no problem at all to extrude at 15mm/s. The cross section is 5.4 times smaller, so I guess the required torque can be 5.4 times smaller, too? I ordered a NEMA17 20mm pancake ( weight 140 gram ) with 13Ncm holding torque. ( a bit different to the pancake E3d uses for their Titan extruder. )
It will surely do the job, but I'm tempted to try an even smaller stepper, like the 14HR05-05A ( weight 50 gram ) with 7Ncm. Maybe add a 3:1 gear, like a tiny Titan. It would then be ~100gram lighter.

I already tried to extrude with a modified 28BYJ stepper, but it was a little bit too weak at 500mA.

I'll post a video of filament making later. Here it is

Edited 3 time(s). Last edit at 03/27/2018 09:46AM by o_lampe.
Re: The 0.8mm filament experiment
April 03, 2018 11:08PM
The short body NEMA17 arrived and I tested it, extruding in free air.
I tried to slice an XYZcalibration cube with 0.8mm filament setting, but Slic3r came up with an error message. So I had to cheat by using 5.4 times more e-steps.
It worked quite well at first, but after a few minutes the shrink tube on the drive gear ripped apart and the filament got chewed by the sharp teeth of the drive gear again. I have to make my own drive gear, maybe start with a brass pinion gear with less sharp teeth and grind a small hob into.

Is anyone here, able to produce decent drive gears ( and an M6 nozzle with 1mm melting chamber diameter, too) ? Please PM me smiling smiley
Re: The 0.8mm filament experiment
April 05, 2018 12:51AM
I took a Dremel cutter wheel and cut a groove in the brass drive wheel while it was spinning.
Now I have the right amount of bite without the teeth chewing through the filament.

Now it's time to mount it in my Prusa i3 and actually print something.
It's still too big to fit on a Delta effector, but one step at a time . I could reduce motor current to 600mA at 200% printspeed ( 1000mA max. ), before it skipped steps. I'm sure the 14HR05-05 stepper ( 50gram ) with 11Ncm will do fine with a little gearing or smaller drive gear.
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