Over extrusion can caused by:
1) Nozzle worn out
Often replace the normal brass nozzle if you print a lot. We will suggest to change the nozzle and PTFE tube together, since you may need to clean the internal of the heat sink and the aluminium heated block. It could take quite a bit of time, might as well change both in one shot.
Printing abrasive filaments like carbornFil or luminous filament (glow in the dark filament) need to change the normal brass nozzle even more often. You may consider to use harder nozzle if you are printing with abrasive filament.
2) Flowrate too high
Adjust flowrate in slicer and do some test print for better print quality.
3) Nozzle temperature too high
Lower nozzle temperature, set it according to the manufacturer suggested temperature.
4) Filament thickness uneven (Rare)
It is quite are to have filament with such serious uneven thickness. Unless you are using a filament with very bad quality.
5) Nozzle size set wrongly
Check your print profile, make sure nozzle size is set according to what you installed to the 3D printer.
Related article found online:
Share with us in the comment if you are experience the same problem and how you fix it.