Regular maintenance: Bearings, Fans, Extruder driver gear, Electronics & PEI.
In general, there are only a few parts you will need to care of, as a precaution is the best way how to prevent future failures. We highly suggest taking regular care of these parts as suggested in the 3D Handbook or below.
Every couple hundred hours, the smooth rods should be cleaned with a paper towel. Then apply a little bit of general purpose machine oil on the smooth rods and move the axis back and forth a couple of times. This cleans the dirt and increases longevity.
If you feel the axis is not running smoothly anymore, bearings can be taken out and greased on the inside (they need to be removed from axis because the plastic lip will prevent the grease from getting inside). Super-lube, or any other multi-purpose grease, will do.
Both fans should be checked and cleaned every couple hundred hours; dust or plastic build-up can decrease their efficiency or even damage them. Computer cleaner spray will get the dust away and tweezers can be used for little plastic strands.
Additional information for Noctua fans used on Original Prusa i3 MK3 and MK2.5
Both extruder and part cooling fans measure current RPM (Revolutions Per Minute). Because of that, they can detect any problem that will cause the fan to slow down, like a piece of filament getting stuck in it. If you get a fan error, check that it can rotate freely; clear any debris that may be stuck in it.
The nozzle cooling fan is made by Noctua. These premium fans are known for their superb quietness and exceptional performance.
You can turn off the monitoring in the LCD menu - Settings - Check fans for example if you replaced one of the fans with a replacement not supporting RPM sensing.
Extruder driver gear
The hobbed drive gear on the extruder motor shaft can have a build-up of filament shavings in the grooves and cause under-extrusion. A small brass brush is an ideal tool to clean the grooves, but a regular toothpick will do the job as well. Check and clean from the access window on both sides of the extruder assembly. Clean what you can, then rotate the gear and repeat. Nothing needs to be disassembled. Clean when you see signs of missing plastic in the objects, e.g. missing lines of extrusion.
PEI print surface preparation
PEI can lose its adhesive powers after a couple hundred hours. Wipe it thoroughly with acetone when you see models getting loose to restore the adhesion. You can find more information how to take care of the PEI surface in PEI print surface preparation.
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