I recently got a Mingda Rock 3 Pro and while I'm loving the printer, my z sync belt was so loose it wasn't doing anything. I'm not sure if the belt stretch or if the previous owner replaced the belt with the wrong size, but I needed something to tighten it up. I designed an adjustable tensioner that uses minimal hardware and doesn't take away any Z height. It needs a 608 bearing and bolts and t nuts to attach it to the machine. The rest is all printed. I added in tolerances to all of the parts so I didn't have to try and add tolerance in the slicer. I printed the main body at 0.2mm resolution with supports and all of the threaded pieces at 0.12mm resolution with no supports. I printed everything with 5 walls to add strength. The holes to attach it to the machine are sized to accept up to M5 bolts.

Creality