How long has it been since you swapped your hot end tip (nozzle)? If it's been more than six months and you print with any regularity, you are probably due for a new one. As you print, your hot end tip accumulates small amounts of residual filament or "char". This can result in thin or uneven extrusion. One way to resolve this is to use the cold-pull technique or some other method to clear the char.
Eventually, however, your filament will begin to wear out the hole in your nozzle. This expands the diameter of the hole. So, if you are going for high-resolution and dialing your settings to the diameter of your nozzle, you want to be sure to keep your tip fresh.
To swap the tip:
1. Bring your hot end to 175C.
2. Insert a 1.5mm allen wrench into the heat block and loosen the nozzle with an 8mm wrench.
3. Install the replacement nozzle, making sure to thread the nozzle flush against the heat break (threaded piece inside of the heat block).
- Ubis 13S User Manual - Tech specs, fan wiring options, and assembly of all individual components