UP mini 2 Printing fine with ABS, not extruding 20 min into print with PLA

Hi all,
I’m fairly new to 3D printing and have been given the job of running the printer at a small country school (so no access to tech support, other than me lol).

I’ve been teaching myself to use the mini 2 and have come across a problem that only seems to happen when printing with PLA. About 20 minutes into a print it seems the printer stops extruding enough PLA to lay down new layers but the printer keeps going through the motions. It looks to me as if the temp isn’t high enough to melt the plastic. I end up with a wispy spiderweb of layers.

The printer heats up to the 220 deg (I’m using the built in settings for each material and have the Tier Time plastics) but pretty quickly into printing the nozzle temperature shows it has decrease to 90-100 degrees. Not sure if this is accurate or the reason. If I pause the print and resume it, the nozzle heats back up to 220, continues to print fine and then the same thing happens another 20 minutes or so later.

I have been printing with ABS with no problems, I changed back to ABS to test it. It printed perfectly fine but the nozzle temperature did the same thing - according to the software.

Any suggestions?


did you use the layer cooling vent thingy on the extruder?