Z axis losing steps, belt tension issue

Ok, I’m having issues with the z axis. The drive belt is loose and that seems to be the cause of unstable z axis movement. So looking for a method of adjusting the tension but there is no take up adjuster on the backplate. Outside of opening the hole into more of a key way is there another method in use for this. Really don’t want to buy a new back plate with the adjuster as I’m hoping to get one of the new z axis units when they become available hopefully soon. If you look at the photo, the circled item is missing on mine

.

Let us know about this at support@carbide3d.com and we’ll send you a Z-axis tension bolt.

If you’re making a run to a hardware store it’s an M4 SHCS ~25mm long.

Does the nut part screw on to the backplate?

My plate has no hole there. How does the nut attach?

However, if you have an older machine, then there is no M4 Z-axis belt tension screw — this was a modification in I believe summer 2016 — to tension the belts on older machines you use a sliding motor mount.

Best way to do this is to put the motor as low as possible and tighten everything up as much as possible, then get a luggage scale, loosen the motor slightly, pull up on the belts for ~18–20 pounds of force and secure one corner — repeat for each corner slightly increasing the tension.