Is there a specific name for that problem? What causes this, and is there a way how to solve it? 

Printed with PLA, 2 mm nozzle diameter, 0.2 mm layer height, 20-60 mm/s, 200 °C extruder, 60 °C bed.

[![Top](https://i.stack.imgur.com/aSzrJ.jpg "Top")](https://i.stack.imgur.com/aSzrJ.jpg "Top")

[![Bottom](https://i.stack.imgur.com/nCgam.jpg "Bottom")](https://i.stack.imgur.com/nCgam.jpg "Bottom")