Clog between extruder and nozzle lifting assembly

mdana
Posts: 61
Joined: Mon Oct 07, 2019 1:36 am

Clog between extruder and nozzle lifting assembly

Postby mdana » Sun Nov 17, 2019 12:51 am

The right extruder on our Pro2 Plus is completely clogged and leaking plastic (PVA) between the extruder and nozzle lifting assembly. Any idea what could have caused melted plastic to get that far up?
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Jetguy
Posts: 2849
Joined: Tue Mar 22, 2016 1:40 am
Location: In a van, down by the river

Re: Clog between extruder and nozzle lifting assembly

Postby Jetguy » Sun Nov 17, 2019 12:24 pm

https://forum.raise3d.com/viewtopic.php ... rea#p33254
The answer is hotend, and specifically the size of the heatsink cooling the critical cold end side of the thermal barrier AKA throat tube. The key elements of the design is a sharp transition from cold unmelted filament to hot melted filament is all based on the throat tube and the heatsink ability to shed and transfer heat to the air via the heatsink.
The Pro2 has a very small heatsink compared to the N2 style V2 hotend. My immediate theory and question the instant the very first pictures showed this was if users get jams- this is likely the first place I would suspect the cause. Again, low temp filaments like PLA (and PVA) are extremely sensitive to temp of the filament path. The plastic loses mechanical strength and becomes soft like a wet noodle. It will find a space where it can deform. While we have yet to see the inside of the moving nozzle mechanism, obviously there has to be some room for the hotend to slide up and down and the filament path may have gaps or diameter changes. This may explain why people have seen stuck nozzle raising and lowering, why you are getting jams- if this area even gets warm or that fan is not effective, again, I think you would be surprised to know how low of a glass transition temp PLA has and how it does not even have to be hot for this problem to occur.

Again, 4 fins VS 8 fins, smaller total fin size VS much larger fin size, single fan cooling 2 hotends VS independent 30mm fans cooing each hotend. Lack of cooling exit area VS intake area (common rule is exit should be 2X larger than intake).


which is why other fellow Pro2 owners figured this out went and did either alternate hotends or water cooled heatbreaks.
https://forum.raise3d.com/viewtopic.php ... led#p37739

mdana
Posts: 61
Joined: Mon Oct 07, 2019 1:36 am

Re: Clog between extruder and nozzle lifting assembly

Postby mdana » Mon Nov 18, 2019 12:41 am

Yeah, I’m considering a couple different options. The easiest would be improving the cooling with upgraded blower style fans or something similar. I would like to switch to mosquito or E3D hot ends, but would like to come up with a better mount that doesn’t use a locking collar. Really didn’t think we would have to sink so much time and effort into this printer just to print PLA successfully.


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