This tool will quickly and accurately tension the belts for all axes. It uses weight to produce the tension, so you don't need to measure the tension in Hz, but rather in grams.

It's work in progress. I'm waiting for the tests and results from the community. After I get some feedback, I'll finalize the design to something more nice looking.

I tested different weights - 6, 5 and 4 lbs. With 6 lbs, I could hear the bearings of the stepper motors, so I'm currently testing something between 4 and 5 lbs.

Assembly Instructions:

1. Print with PETG. (PLA may hold the weight too, but I haven't tested that.) Use some other color than black, so you won't accidentally leave the tensioner there after calibration.
2. Assemble the tensioner. You need 2 M5x30mm screws, and two M5 nuts. (You can also use M4 and M3, but you need to add washers.)
3. Add weight. Start with 4 lbs (1.81 kilograms - measure the weight on kitchen scale, include the weight of the tensioner). Use lead balls. There's space for about 5 lbs of lead balls, you can add there sand and steel balls, but lead is much more compact.

Calibration Instructions:

1. Move the effector/print head, to the top. Now chose the one axis/side of the printer that you will calibrate.
2. Permanently remove the old belt tensioners - unscrew the screw with the knob, and remove the spring.
3. Permanently remove the bottom plate of the old tensioner, unscrew those two screws, remove everything, so only the top plate stays.
4. Loosen two screws on the top plate by one revolution. Try to move the plate up and down, it should move freely - you should see that the belt is loose.
5. Put the belt tensioner on the top plate.
6. Tighten those two screws back.
7. Repeat the whole process on the second and third axis/side.
8. Now you can test the tension with your hand, it should feel equal on each side.

After you're done, don't forget to remove the tensioner before you start printing. You might need to adjust z offset slightly while printing. So run some test print. In my case, after belt tension calibration, the nozzle was a bit higher.

Please publish here your print and share your results - your ideal tension/weight.