Poor extrusion after extruder jam repair
I've been a Prusa 'maker' for well over 10 years now, first with a MK3S+ and now with a MK4 (with Core upgrade on order). When I upgraded from MK3S+ to MK4, I gave my MK3S+ to a nearby relative. My relative managed to jam the extruder, so I have it back in the shop. I had to disassemble the extruder assembly to clear the jam, but that (eventually) was successful. I put everything back together and ran the calibration wizard successfully, and got the Z-axis offset set properly. However, when I tried to print a 10mm calibration cube, the first layer went fine but after that filament extrusion tapered off to nothing.
Eventually I got to the point where I was just using 'Settings -> Move axis -> Extruder to advance the filament, and I could see that filament was being extruded much more slowly than normal (like about 1mm/sec or less). Thinking this was a grubwheel tension problem, I increased the tension while commanding additional extrusion, but it still stayed slower than normal regardless of tension setting.
Then I unloaded the filament and inspected it. I could see where the grubwheel had abraded the filament, so I got the sense there was something else in the chain causing the problem. As another test I used the 'Load Filament' command to start the load, and then repeatedly said 'No' to the 'was enough filament extruded' question. As I did this I adjusted the grubwheel tension up and down looking for a setting that produced the expected filament extrusion rate, but nothing worked. All the way from no tension to full tension causing 'clicking' noises the extrusion rate was very slow.
Any ideas what I'm doing wrong here, or ideas for how to troubleshoot this further?
TIA
Open the idler and brush/blow out the filament dust.
While it's open take 50cm or so of filament, heat the nozzle to 10°C above the print temperature of the highest melting point filament that you use and, bypassing the Bowden gears, manually push the filament down through the hot end; slowly at first and accelerating to as fast as it will go finishing by pulling it back out as fast as you can - no pause.
Follow this with a conventional cold pull and you should clear any partial blockage.
https://help.prusa3d.com/article/cold-pull-mk3-s-mk2-5-s-mk3-5-s_2075
Cheerio,
RE: Poor extrusion after extruder jam repair
Thanks for the help! Your 'cold-pull prep' worked great and so did the cold pull. I have avoided 'cold pulls' like the plague all these years, thinking "that's just got to be a good way to REALLY screw up a 3D printer", but I have to admit I was wrong. Better late than never I guess 😋
RE: Poor extrusion after extruder jam repair
Here's the 10mm cal cube after the cold pull
