Ninjaflex Geared Ultimaker 2 Feeder

[dmolina 4]

I've made this post to discuss the pros and cons of the present design, to improve the already working and reliable design and get an even better mechanism!

Ninjaflex Geared Ultimaker 2 Feeder

I'd be glad to hear your ideas!

[chin 6]

Interesting idea, we're currently trying to outfit our UM2 with the |Robert| UM2 Feeder but this is also a very nice solution.

Did you print the feeder housing with CF20?

[dmolina 4]

Yes, thanks, I've adapt on previous work (here).

Everything in the picture is printed in CF20, except the wheels that are Ninjaflex. I've had good results printing the body in ABS, it seems that the gears slide better over it. CF20 gears over CF20 body creates sort of an additional friction. Printing the gears in ABS was somewhat problematic, because it expands more at the bottom of the print and makes uneven gears, that's why I went for CF20 in the first place. I'm confident though that with the right setting it can be done right.

[Labern 775]

How long have you been using it for? Have you found àny wear on the ninja flex?

[dmolina 4]

I've been using it for about a month, there is a little wear on the edges of the zigzag pattern, not enough to affect performance so far.

[Labern 775]

I'm just wondering if any of that can make its way through the bowden tube. I'm a bit tired so so not sure if I'm thinking right but with the driven rollers having a bigger circumference, wouldn't they try to feed more then the drive wheel?

[dmolina 4]

Ow, I don't know if you tried to download it and took a look at the models, but there is an axle gear that goes into the stepper motor shaft (that I had forgotten to upload, it's there now!), so no, they can't feed in different rates whatsoever.

[slyowl 4]

We've been working on a similar concept at Open Bionics. The aim is to prevent the filament stripping if it jams, so we avoided using metal gears in tandem.

Our first design used gears that were too small, and skipped before it could extrude. The metal gears here were inspired by yours - but it worked much better without!

The different diameters of the metal and ninjaflex gears mean you have to be careful how you design the gears, as you need the perimeter moving at the same rate. I think you got away with it because your two gears on the stepper have the same diameter - ours didn't!

Note the "stacked" extra gears - this was an attempt to increase the friction. It worked, but modifying the ninjaflex wheel diameter and surface pattern (sanding it?) is simpler and probably less prone to failure.

Our revised design uses much better gears, which can all be whatever size we like (no metal gears!). We had to lower the e_steps, because of the increased diameter. It works nicely, and the stepper skips before the filament slides or gears skip - proving the principle works. However, the filament tends to move up and down the wheel, and pops out the top, or gets caught in the gears. We haven't made the changes yet, but propose to have interlocking ninjaflex teeth above and below the wheel, to stop the filament getting out. There would still be the PLA gears to transfer the force! We think that having guide holes for the filament just before and just after the wheels would also help. Experiments with butting the top/bottom of the wheels up to a flat surface failed, as the ninjaflex deformed and filament got stuck between the wheel and surface...

Have you had issues with the filament moving around? Perhaps the metal gears keep it nice and central...

For this layout, we could stack the gears the other side of the stepper, which would only use 5 gears, instead of 6.

[dmolina 4]

Hey slyowl,

I'm well over 2 months using the extruder now, it's working great, the filament goes straight into the contact ninjaflex wheels, the guiding in the present design works fine.

My guess is the ratio of your gears don't match somehow, that is, one set moves faster than the other, than the filament doesn't move straight up as it should. I'm really guessing here though, maybe a video of it working would help visualize what is happening.

Well, from my experience, the more wheels you got, the harder it is to make it run smoothly. I've spent many days with the 4 contact wheels until I arrived at the present working version.