Y-axis belt tensioner

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UPDATE 24.03.2022

There is a revised version @ https://www.prusaprinters.org/prints/154337-y-axis-belt-tensioner-revised

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For a long time I used the y-axis belt tensioner designed by Boogie (respect, man): https://www.prusaprinters.org/prints/57663-y-axis-belt-tensioner
This is a greatly designed part, but it is a little bit tricky to adjust the four screws equally.

So, I  ponder the question “What if…?”

This is how I started to draw and passed through various configurations, until I got the optimal design (surly it can be improved, but it is up to you guys).

Now the description:

Tools needed:

• Tension Meter for the GT2 belts of i3 MK3S+ or Prusa MINI+ from here: https://www.prusaprinters.org/prints/46639-tension-meter-for-the-gt2-belts-of-i3-mk3s-or-prus/comments or something like this.
• Ball head Allan key (from your printer’s tools bag).

For the assembly you’ll need additional 3xM3 hexagonal nuts and 2xM3x18 mm screws. All of them can be found in your printer’s spear parts bag.

But, safety first! Turn off the printer and unplug the power cord.

Detach the display and put it aside.

Dismount the y-belt-idler and get the pulley.

Turn the printer on one side with the PSU down.

Take apart the y-belt-tensioner and detach the timing belt.

Mount the pulley on its holder, using one of the 18 mm screw and a hexagonal nut.

This is what you should get.

Take the tensioner mount and inserts two of the hexagonal nuts on the front side.

Insert the last hex nut in to the opening on the back side. You may use a nylock nut if you want.

Important: When mounting the parts on the printer, the triangular marks must be pointed upwards.

Slide the pulley holder into the mount.

Secure it with the second 18 mm M3 screw.

Put the printer on its feet. Mount the assembled belt tensioner on the printer’s frame. Pay attention to the triangular marks.

Now we are on the final steps. Put again the device on its PSU side. Shorten the timing belt 30 mm (approx. 1.2”). I cut off mine. The essential is that the belt isn’t obstructs the movement of the bed carriage all the way. I didn’t try if it is possible to shorten the belt from the side of the Y-axis stepper motor. Attach the belt to the original y-belt-tensioner and mount it back to its place. It’s time to use the tension meter. 

Place it on the GT2 timing belt and use the original belt tensioner to adjust the meter on its minimal position. Tighten all the screws.

Be sure that the old belt tensioner doesn’t hit the pulley and check all parts and screws one more time. Straighten the printer

Use your new timing belt tensioner…

… and the tension meter, to fine tune the belt, so the arrow points between min and max positions.

Mount back the display and reattach the interface cables.

Power up the printer. Wait for the OK message.

Now it’s time to run XYZ calibration…

… and a final belt test.

That’s all folks! Enjoy your new GT2 timing belt tensioner!

If you decide to print it, all feedback will be hugely appreciated.

And don’t forget ❤⭐