Pivot-Lever One-Piece Gripping One-Screw Tensioner
Scableable belt tensioner works with a range of belt sizes, in multiple orientations and belt positions.
Sawtooth teeth on both sides of channel help grip the belt (belt can be installed with teeth facing in or out). As tension increases on the belt, it pulls the flexible arm into the larger fixed arm, pinching the belt for even better grip.
ABS is probably better than PLA as the flexibility will help it grip the belt better.
Requires only one screw, one nut, and one cable tie.
Print and install an 8-32 screw and nut (6-32 will also work). Only put the screw a little bit into the nut for now.
Feed the belt loose end through the S-curve and wrap it flat against the teeth on the back of the tensioner.
Wrap a cable tie around the tensioner (use the slots in the side) and over the loose end of the belt.
Pinch the flexible arm and the belt loose end into the fixed arm as you tighten the cable tie. Pull it as tight as you can. Smaller belts need more cable tie tension to avoid slippage.
Make sure the pivot is resting against a flat area of the printer body and adjust the screw to increase tension.