Extruder Jamming in Hotend

I purchased my Mini just before the Mini 2 came out, then left in the box for 4 months more. I’ve printing constantly since then using PLA from Esun and Push. For the last 3 weeks I’ve been having a problem with my filament jamming just above the nozzle. At then end of a print job, the filament is too large to re-enter the nozzle. I’ve had to unload the filament, trim the expanded portion, and then AFTER auto-leveling, when the nozzle is almost to temperature I can re-load the material as the Mini begins printing.

When I try to print something without doing this, the hob grinds out the material instead of forcing in into the nozzle. I’ve tried all matter of heat settings to no avail. My fans are all working properly, and my air ducts are clear.

I am at a loss after trying everything I could find in other posts. Since the air ducts look like some of fan housing mods already, I have not replaced them. Nor have I tried a new nozzle, although I have several E3D nozzles available.

What next?

We run a lot of PLA on several machines. Generally, heat creep jams are due to a room that is too warm or a failing heatsink fan. If your room is warmer that the mid 70s F, try cooling it down a bit. If the room is cool enough, try replacing the fan. Sometimes these fans appear to be working well but are failing and not moving enough air. If you have the older extruder with a small radial fan, that is likely the problem. Those fans are barely sufficient for PLA when they are operating at peak performance. You can print parts to convert the toolhead to a 40 x 10 or 40 x 20 fan.

I leave filament oiling as a last resort but it does help in some cases, especially with PLA prints.

Thanks, Nopick, for your response. My room is usually about 73 degrees, so I might need to cool it down a bit. I already have 40mm fans, but they’re not too expensive. I’ll replace both of mine just to sure.

If it is a fan problem, it would be the fan blowing on the hotend heatsink.

You should be fine at 73F. If your fan is moving a good amount of air, the tension is correct on the filament idler and your filament is within spec, you might try extruding some filament oiled with canola oil. It generally isn’t necessary but does help sometimes.