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I just printed another track at 0.3mm layer height. It seems to work fine. I think 0.2 will be safer. (I think i printed at 0.35 or 0.4mm thats why it didn't work). YES! it works acceptably with the lower friction track, but I will go back those bearing you recommended and swap them out to rule out any factor of failer. I really want to make this work with printing TPU.
So I am currently printing the sheep file with TPU. The situation has improved a lot but 1 out 5 time the filament still escape the spool.
I think the cause are as follows:
1) unload speed is too fast the rewind mechanism haven't got the time to rewind result excess filament shooting out everywhere.
Solution --> I added additional weight to combat this i'll see if the problem persist, like in my mention in my post, the adding weight can other problem with unloading too much.
Solution 2 --> Tweak the "unloading speed" in slicer so it will unload slower, as a result the filament will tension on the rewind mechanism while unloading back into the selector. I might try 50mm/s as a start, but if you have any unloading speed parameter as a starting point let me know.
I will report back after i try it in my next print. :)
Solution 3 --> It's possible to add a plate guard that attaches to the button of the frame that butts against the spool prevent the excess filament from escaping the spool in case the rewind mechanism can't catch up with the speed which the filament unload. In my opinion, this is the last option if all else fail because I don't feel this address the inherent problem. I can probably laser cut a guard plate at work this week if other attempts fail.
Another note: so far this mechanism works flawlessly with my PLA filament :)