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Inconsistent feed  

Inconsistent feed

Been using this machine for a while with some smaller issues here and there that I've been able to figure out. This one has me a little stumped. The filament will feed well and then will just have a hiccup of under extrusion then continue. Sometimes picking up the underextruded filament then dragging that over the rest of the print.

Issue started when changing filament from hatchbox petg to creality pla, thought the filament was just junk, but the issue is present when I switched back to petg. I have had issues with using a clogged nozzle before, but this is different. 

So far I have: cleaned the nozzle, cleaned the bed thoroughly, went through the extruder gears, checked the ptfe tube in the cold end, checked if there was gear slip on the shaft, extruder shaft shutter, confirmed hot end temp with a ir temp gun, and tried different nozzles.

Might be some other things I'm leaving out, but I've tried everything that I think would solve it. Hoping someone here has had something similar or more knowledge than me to help out.

Apologies for the potato photo, but you can see the issue on the last line of the first layer z-cal print and the transition to the infill section.

Thanks for your time

Posted : 15/02/2024 4:15 pm
Reputable Member
RE: Inconsistent feed

Sound like you may have introduced a clog, a cold pull may be in order.



Prusa I3 Mk2 kit upgraded to Mk2.5s, Ender3 with many mods, Prusa Mini kit with Bondtech heat break, Prusa I3 Mk3s+ kit

Posted : 22/02/2024 1:55 am
RE: Inconsistent feed

Hey, just had the same kind of issue and been troubleshooting it for the last two days on a MK3s+. In my case I think there were two causes:

1. the grub screw that holds the extruder gear in place on the motor shaft had come loose and the alignment of the extruder gear with respect to the filament was off and it was not able to push the filament into the hotend. To fix that I had to loosen up the pre-tensioner screw with spring to open the idler door and look inside at the gear and filament. Then go to Settings > move axis > Extruder and rotate it until you see the grub screw. Align the gear centered on the filament and  make sure to tighten the grub screw on the flat side of the shaft in that position.

2. It seems somehow the spring of the pre-tensioner screw has been weakened (no idea how) so that I had to tighten it really hard to make sure the gear pulls the filament and push it continuously into the hotend. Only after tightening it very hard it is working again, which is weird.

Not sure if this is the right way to do it but for now it seems to work again. It's kind of weird that the pre-tensioner kind of lost it's initial tension. It was really weak and was not able to push the filament into the hotend which lead exactly to what you showed in the image.

If anyone from Prusa or other experts read this, can you confirm that this is the right way to deal with it? Is this something that happens often (the spring losing its tension)? Should I get a new one?

Thanks for any advice


Posted : 22/02/2024 10:59 pm