OK, this is a “sagging” issue. The filament is falling, as there is nothing beneath it to support it. This is a result of a combination of cooling issues and overextrusion, creating too much material that has no support under it.
For PLA, you need to have active cooling.
You can also increase the cooling setting on your slicer software. That is, increase the pause between each layer, so each layer has more time to cool before the next layer is printed. This allows the print to have better support on it.
Also, print 4 marvins at the same time, or add it to another print you are doing. More printing time per layer = less sag.
Finally, it appears you are slightly over extruding. Measure your filament, make sure it is the set correctly. Extrude slightly less filament.
The reason many folks on this board have suggested multiple marvin prints at the same time is that effectively slows down the time between each layer, allowing the previous layer to cool and fully crystalize before the next layer is printed.
This is why I suggested you print it along with another item you are printing, or to print several of them.
It is a tried a true solution that has solved marvin issues in the past, and is a common solution when printing small parts. Inactive cooling.
I have tried 180 but not with the bed off. 180 for the PLA I am using is lower than it likes. The loop at the top will crumble if touched, like it crystalized. It doesn’t react this way when printed at a higher temp.
From what I can tell this issue is caused by the way the nozzle is coming off the print when the slicing is going on. I currently have an army of marvins laughing at me. Every print better than the other but ultimately i think this is an issue resolved in the slicer
