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sputnik

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  1. Thanks I had not seen that thread before. I reassembled my damaged hotend and am feeding the filament from the opposite side now; tracks are now on the concave side and that did probably help with friction as my printer is now printing again. the result is not pretty because of underextrusion, but definitely way better than before on the same model. No idea however if it helps with teflon isolator wear.
  2. i have reading the forum a lot recently because on my printer, the original non-glass-filled isolator failed after 230hrs of printing and a new, glass-filled replacement is already worn out after a printing a single roll of filament (colorfabb blueish white, at 210 degrees). i suspect that apart from the isolator unquestionably being too soft, there is maybe another problem that leads to isolator failure, namely the feeder design: the knurled bolt of the feeder is probably running on the wrong side of the filament. when a spool is loaded normally, the knurled bolt is running on the convex outside of the filament while the opposing smooth bearing is on the concave inside. As the filament has a tendency to curl up in the same was as it had been on the filament spool, it is orienting itself in a way that the track marks left by the knurled bolt will always be on the outward facing convex side of the bowden and - in extension to that - the teflon isolator. Unfortunately, the outward curved side of the bowden tube and same side of the teflon isolator is where all the pressure from the feeder motor goes. My guess is this causes a lot more friction than would be necessary. On Colorfabb filament which i am using the track marks left by the knurled bolt are rough and deep so i think they are what is grinding up my isolator. Additionally, the wear marks on the isolator are just on one side; the other side of the isolator hole still looks like new. So when i get my replacement parts i will try to feed the filament from the other side, so that the track marks are running on the inner, concave non-pressure side and see if that helps. For a permanent solution, one could easily print a "mirrored" feeder and change the rotation direction of the feeder motor. Any thoughts on that?
  3. i stumbled upon this thread while researching my own underextrusion problems; my prints looked pretty much the same as yours, perfect in some places but then random places of underextrusion. larger prints usually failed randomly after 6-10 hours of printing. the extrusion test piece however always printed flawlessly. in my case the problem was the knurled bolt on the feeder. sometimes - depending on where the filament spool sits on the spool holder - the filament was going into the feeder at a slight angle (not exactly vertical but tilted towards the front of the printer); then the filament was only partly riding on the knurled part of the knurled bolt which caused random slippage and underextrusion. the solution was to unmount the feeder and slide the knurled bolt inwards, closer to the stepper motor, for about 2mm, so that it is no longer flush with the feeder stepper motor shaft. perhaps this shaft is too long on my machine. printed the same .gcodes again, no more problems, printer now working flawlessly for 50+ hours
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