[v2] Prusa i3 MK3 Y-axis belt tensioner

This is a remix of the y-axis idler mount from the Prusa i3 Bear Upgrade that fits on the stock Prusa i3 MK3 frame.

Installation

1. Remove the LCD assembly from the front plate
2. Remove the front plate and existing idler mount from the printer
3. Screw the new y idler mount onto the front plate using the top and bottom holes
4. Drill through the middle hole using a 3mm (or 1/8in) bit to make a new mounting hole in the front plate (deburr if necessary)
5. Remove the mount and place the final installation hardware
   1. Install regular hex nuts into the bottom and middle holes
   2. Install a nylock nut (nylon side towards the front plate) into the top hole
6. Being careful not to lose the nylock nut, pass screws through the front plate into the mount using the bottom and middle holes
7. Attach the tensioner to the idler mount using an M3×25mm screw and nylock nut
8. If you have a MK3S(+), replace the tensioner under the bed with a MK3 belt clamp

Installation for v1 is similar, but alignment is more difficult and you need to insert the nylock nut into the slot on top.

v2 Update

• Loosen nut tolerances
• Tensioner nut is now held in place by the frame; no need to push it in from the top

Note: the images are of v1, but the process for v2 is similar.

Required Parts

Printing Instructions

Print with 3 or 4 perimeters and at least 20% infill using a 0.4mm nozzle. Although it works either way, I recommend printing this model upside down to put the nice surface finish on top.