Another Extruder Problem

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superhornet59
Posts: 60
Joined: Wed Apr 03, 2013 1:58 am

Another Extruder Problem

Post by superhornet59 »

Does anyone else have an issue with the tensioner bearing not spinning? Likely because it's tightening against a part of extru_base_pt2 instead of only the filament? It creates a whacky situation where if I under-tighten the extruder, the hobbed wheel can't bite in properly and grinds, but if I overtighten, the friction of the filament against the stuck bearing becomes too high and it won't extrude either. Very delicate balance that regularly gets thrown off mid print. I have a feeling it's because of warp in the extruder components, wouldn't be the first time. Anyone else notice this?

dognotdog
Posts: 181
Joined: Tue Sep 04, 2012 9:22 pm

Post by dognotdog »

It's a tight fit, if the bearing can't move freely, make room for it. Maybe offseting it with a washer could help? I had to file off some material from the 1.5 extruder arm in my setup.

superhornet59
Posts: 60
Joined: Wed Apr 03, 2013 1:58 am

Post by superhornet59 »

I ended up reprinting extru_base_pt2 again while 'manually assisting' the extruder. It took around 3 hours.. WOW my arm was tired! The tab which the tensioner spring-washers rest against cracked. Must have been from fatigue, I don't often apply much tension (because of that bearing friction problem). One thing I do notice is that when the filament is 'grabbed' by the hobbed wheel, the bearing is immediately pushed away to make room for it.. but it isn't pushed away linearly. It actually forms an angle with the hobbed wheel.. this moment of force (which just looking at the tensioner arm is obviously higher than it should) is what likely caused that tab to fail, and once it failed, extrusion became very inconsistent until it stopped, especially once the bearing really started getting stuck (distortion got so bad that the rear part of the tensioner arm started coming into contact with the larger part of the hobbed wheel!!)

I've solved it temporarily. In any case I'm posting this so if it's a common problem it will snowball and will be addressed in the future. Personally I think in the next Felix the 'pull' type tensioner should be replaced for the industry standard 'type-2 lever' tensioner such as the one you employed in your direct dual extruder, it can also better cope with: moderate part warping, larger moments at the bearing, and overtightening. With the extruder being the weakest point on the Felix, I'm really surprised this hasn't been done yet.

dognotdog
Posts: 181
Joined: Tue Sep 04, 2012 9:22 pm

Post by dognotdog »

My design has the disadvantage of the adjustment bolts being accessible only from the "back", as more airflow is needed to keep the extruders cool when they're idle.

Maybe with the new, ribbed, hot-end, cooling will be easier. Though my design could also be adapted for a single extruder with better accessibility. I found the arms moved much better than the felix design, giving me more confidence that uneven filament could be handled better.

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