This is an upgraded y-belt-tentioner for the Anet A6 3d printer. The difference to other belt tentioners is, that this version has the belt bearing at the same hight as the original piece and the stepper motor. This feature makes the belt parallel if you use a y-belt-holder like this https://www.thingiverse.com/thing:2347849.
I only changed the two frame pieces to fit my requirements. The backplate and the screw are from the belt tentioner from OdomLinx.
The frame piece version 2 is a bit more rigid than version 1. The downside is, that you have to drill out the mounting holes to remove the support material. If you're not careful enough, you can make the holes to wide.
Picture 1: Frame V2 fully assembled
Picture 2: Tentioner in printer
Picture 3: Frame V1
Picture 4: Frame V2
Picture 5: Comparison with original piece
Picture 6: Chamfered hole (only on left frame)
Support 15-20% for the holes.