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Prusa MK4 Maintenance

Regular maintenance checklist for the Original Prusa MK4 (Nextruder). It follows Prusa's own guide: Regular printer maintenance (MK4/S, MK3.9/S).

How often

Interval What
Before every print Some items; see Prusa's guide linked above
Every 200 print hours Axes (rods and bearings), belts, fans and the Nextruder (sections 2 to 8)
Yearly, or every 600 to 800 print hours Electronics check (section 9)

Supplies

  • Prusa Lubricant (Prusa Lubricant Applicator Set)
  • Isopropyl alcohol (IPA) and paper towels
  • Compressed air, small brass brush, tweezers, toothpick
  • Allen keys, needle-nose pliers
  • Acetone (Smooth PEI sheet only)

Do not lubricate the Z-axis lead screws or trapezoid nuts. Do not open the Nextruder gearbox unless Prusa support asks you to; the primary gear and idler bearings need no lubricant.

1. Before you start

  • Note the print hours and firmware version so they can be logged with the maintenance.
  • Unload filament.
  • Clear any maintenance warning on the screen and note what it said (Maintenance warning reference).

2. General cleaning and hotend

  • Brush or vacuum debris from the frame and under the heatbed.
  • Heat the nozzle to 250 °C for 3 to 5 minutes, then scrub old plastic off with a brass brush. Keep the brush off the hotend cables.
  • Let it cool for about 10 minutes, and confirm the temperature on the display before touching it.

3. Hotend thumb screws and nozzle seating (printer off and cold)

  • Hand-tighten the hotend thumb screws (no tools).
  • Confirm the nozzle has no vertical play and the heater block does not rotate.
  • If a Nozzle Adapter is installed, confirm the nozzle is not lowered or loose (Nextruder V6 Nozzle Adapter).

4. Smooth rods and bearings (X, Y, Z)

  • Roll each rod between your fingers to feel for grooves or scratches.
  • Wipe each rod clean with a paper towel.
  • Apply a small amount of Prusa Lubricant and run each axis end to end several times.
  • Only if an axis still feels rough: remove the bearings, clean them with IPA, and regrease the inside with a small amount of Prusa Lubricant. A printable LM8UU bearing greasing adaptor makes this easier.

5. Belts and pulleys

  • Remove debris around the pulleys and belts.
  • Confirm each pulley set screw is tight on the flat of the motor shaft.
  • Pluck the X and Y belts: they should give a low bass note.
  • Measure and adjust tension per Adjusting belt tension (MK4/S, MK3.9/S, MK3.5/S, MK3/S/+), which covers the frequency method used on the MK4. Note the upper, lower and Y readings.

6. Fans

  • Hold each propeller still and blow it out with compressed air. Never blow air into a running or free-spinning fan.
  • Remove plastic threads with tweezers.
  • Never bypass the fan RPM check. A slow fan throws an error on purpose.

7. Nextruder (drive gear area)

8. Print sheets

9. Electronics (yearly, or every 600 to 800 hours)

  • Power off and unplug the printer.
  • Check and reseat the connectors on the xBuddy board, Loveboard, heatbed, PSU and xLCD.
  • Confirm screw-terminal connectors are fully tight.
  • For Molex connectors, press the latch before pulling.

10. Firmware

  • Update to the latest stable MK4 firmware if it is behind (download from Prusa's MK4 firmware page; install from a USB drive).

11. Recalibrate

  • Run Selftest / Calibrations & Tests from the printer menu.
  • Run the Loadcell Test (Control > Calibration & Tests > Loadcell Test). If it fails, see Loadcell troubleshooting; overtightened Nextruder bolts are a common cause.
  • Confirm Input Shaper is enabled and that the slicer uses the Input Shaper profile (Input Shaper article).
  • Print a small test part. The first layer is auto-calibrated by mesh bed leveling through the load cell, so just inspect it.

Afterwards

Record anything you found, what you did about it, and whether follow-up is needed. If the printer is not safe to use, tag it out of service: see Shop Safety: Tagging a Tool Out of Service and Reporting It.

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