Z stepper Timing pulley tension arm

this arm is mounted to your printer in conjunction with a GT2 belt and GT2 toothed pulleys
to help keep the x gantry from sagging.

you can get all the parts you need from robodig or aliexpress.
use some string to measure an approximate length for the closed loop GT2 Belt that you need , it is better to have it slightly oversize than too tight as the tension arm will bring evertyhing to tension.