One serious problem of Bowden

Hi,

Over four months of running Kossel Mini, it destroyed two Push fits.



Few days ago I installed a heavy duty Push fit and it literally chewed up end of PFA tube, eventually extruder side of tube began to pop out middle of printing.
Out of frustration I applied epoxy on the Push fit and PFA tube hopping it would stop movement of PFA tube.

Does Bowden drive require Push fit or FTA tube replacement often? Or my Bowden setup isn't right.

I find that if I never remove the Bowden tube from the push fit connector, it lasts forever. However, after removing and re-inserting the Bowden tube a few times, the push fit fitting loses its grip and needs to be replaced.

I also had once instance of one of the metal teeth in a push fit connector becoming detached. It got fed into the hot end along with the filament, and wrecked it.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

I can vouch for these Pushfit connectors they hold like I don't know what only downside is they are 1/8 BSpp so need a 9.5 mm diam hole to thread into.

I'm lucky I can get these from a local supplier only 3 miles from home! but www.reprapworld.com sells them as well Pushfit connector for 2 euros each

Doug

mine doesn't let go anymore, is yours too loose?

EDIT: nevermind I cant read

Edited 1 time(s). Last edit at 06/19/2015 06:43PM by greggo.

Two failed in about a year.

Get the ones from e3d. maybe you have to print an adapter for you hotend opening but they clamp down much more effectively and there is only a little ring shaped mark on the tube. Im using the same bowden tube since the V6 came out.

I have never had a push fitting go bad. The tube edge has gone bad on me requiring me to cut out a 4-5mm sliver and reinsert. Why are you guys having such issues? I use the cheapo chinese push fittings and never had a problem.

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My Personal Blog. Build blog.
[engineerd3d.ddns.net]

Modicum V1 sold on e-bay user jaguarking11

The push fits have metal "fins". The bowden is getting weared out over time by the metal fins. The fins cut a circular groove into the bowden. This results in more bending fatigue on the fins. They close more and the force is less along the fin length and more lateral (where it is more damaging). So they eventually break.

The problem is that a lot of these couplings are typically rated to preasures up to about 1 MPa. That corresponds to about 12.6 N of filament push force. But only direct drive extruders are typically around 10 N of filament push force. Geared extruder can go easily to about 40 N. So we are overloading the push fits a lot. And retractions cycle the force. That makes it worse.

Edited 1 time(s). Last edit at 06/26/2015 08:37PM by hercek.