What is happening to this print?

It looks fine in Cura and should have a completely flat bottom. The first attempt looks scarred up and the second is less so but you can see it’s still not printing completely straight lines. I haven’t seen this happen to a print before. Between the first and second attempts, I tried restarting a few times but it had trouble extruding filament. Eventually, it worked. I am using 3mm PLA.

First attempt:

Second attempt:

The fillament didn’t adhere to the bed. With PLA that can be caused by oils or residues on the bed (possibly from a hand on the bed while removing a part), improper temperature, nozzle too high, or a couple of other things. when that happens, it lays the fillament down in a straight line, but then lifts in a ripple pattern away from the bed. That can also be caused by a bed or carriage with a very loose bearing setup that needs adjusted. Occasionally you can also see that with an idler arm tension set too low causing the fillament feed to be intermittnat.

Thanks for your reply. I already tried cleaning the bed, and I’m using the same temperature I always do with the same type of filament. What do you think is a reasonable next step?

what process did you use to clean the bed?

Next step would be checking the Idler tension, cleaning the hobbed bolt, making sure your fillament diameter is set properly in Cura, and then possibly mving the nozzle offset setting in cura closer to the bed.

I wiped the bed down with some isopropyl alcohol, which has worked for me in the past. I’ll check on the other things you suggested and see if they help.

Can’t help but notice that it looks like your nozzle may be too close to the print bed. The skirt (and remaining part outline) in the second pic is almost see through. The first pic give the same impression due to the outer perimeter being so shiny a void of any filament lines.