Prusa MK3, MK2 X-Axis Belt Tensioner

I had a difficult time getting the belt tension I was looking for when assembling the original MK3 printer. I wanted more adjustment then what is available by rotating the stepper motor when tightening. Once assembled it is also difficult to get back in and tighten the belt on the X-Axis carriage. So I designed a simple plate that mounts to the motor and has slots to allow for tightening the belt. Assemble the plate on to the X-Axis motor with (4x) M3 x 10mm screws, I had these in my Spare Parts Bag. Install (3x) of the square M3 nuts (also in Spare Parts Bag) in the slots then assemble to the mount, leave slightly loose. I used a screw driver between the motor and the frame for leverage to get the belt tight and then fully tightened the 3 screws. I also flipped the pulley on the motor around 180 degrees so the belt was aligned inside the slot.

The 1in model has a 1.0in center hole for the stepper motor instead of 22mm on the original.

I don't believe this works with the new updated MK3 design with built in tensioner, but shouldn't really be needed on that design anyway.

Print instructions

Printed on MK3 with standard PLA with 100% infill and no supports. I had the counterbored holes facing down, and just needed a little cleanup inside them after printing.