Appropriate belt tension is key for achieving good print quality and needs occasional adjustment due to mechanical vibrations and material fatigue.
Inspired by @Boogie's design, my concept offers a quick and easy X-axis tensioner for Prusa i3 printers with 10 mm Z-axis rods, including:
Prusa i3 MK3.9, MK4, MK3.9S and MK4S
Muscled Prusa i3 MK3, — MK3 upgraded with 10 mm Z-axis rods (see @Alego's example)
❗Note:Although I have thoroughly engineered this design — optimising stiffness, tolerances, and printability over many hours — it is still in beta testing on my personal muscled MK3. I also do not own an MK4 or similar model, so your feedback is highly appreciated to help me improve the design for everyone with this kind of printers.
And if you enjoy it, please don’t forget to like, download, and rate — it helps me earn some Prusameters in return for the time and effort I put into designing, iterating, and prototyping all my free models.
2. Bill of Materials
All versions
Printed Parts
2x M3x20 screws (preferably DIN912)
2x M3 nyloc nuts (preferably DIN985)
2x M3x12 screws (preferably DIN912) instead of the 2x M3x16, used as a stop for both rods in the x-end-idler part.
Supplements for Muscled MK3 compared to MK4
2x M3 square nut (preferably DIN562)
2x M3x16 screw (preferably DIN912)
3. Printing Instructions
PETG (or better like ASA, PCCF, etc. Not PLA)
Layer Height: 0,2 Structural
Min 4 perimeters
No supports
Min 25% infill
Infill Pattern: Cubic or Adaptive Cubic or Gyroid (my goto)
Orientation: Very important for stiffness and printability. Thus strictly follow the pictures or 3mf files.
4. Assembly Instructions
Clean all printed parts and remove any burrs or imperfections.
Follow the Prusa MK4/MK4S manual to assemble the screws, nuts, rods, motor, and idler — everything except the belt and X-end pulley.
Insert the two nyloc nuts into the tensioner part.
Loop the belt around the pulley and insert the pulley into the tensioner using the 3×20 mm dowel pin.
Slide the tensioner into the X-end idler and partially screw in the two M3×20 mm screws from the side, keeping them evenly tightened.
Place the belt around the motor idler.
Adjust belt tension by tightening or loosening the two screws evenly. That’s it!
5. Notes and Disclaimer
Do not use these G-code files on any printer other than the one mentionned. In any case, I strongly recommend opening the 3MF files, adjusting settings for your printer, and slicing the models yourself. The main intent of G-code files is to provide an estimation of pinting time an filament usage.
If you have any doubts or questions, feel free to ask — I’m happy to help. However, I cannot be held responsible for any issues, damages, or injuries that may occur to your printer, your property, or yourself as a result of using this design. Use at your own risk.
Daniel Vitanza
