Z Belt Tensioner No Hardware Required Elegoo Neptune 4 Pro/Plus/Max

No need to run to the store or browse amazon for this one - just some glue and filament hold it together. Smooth operation. Easy and quick upgrade. Long lasting. No belt wear. Increases belt's grip on pulley gears. Clips to the top rail. You may have noticed the rumbling layer lines in the pics. This is caused by using polyholes in the slicer. You can leave it disabled if it bothers you.

UPDATE 05/12/25 (newest):

The files preceded with “ZBT” are the most recent.

Improvements:

• quieter
• more durable
• concave barrel - gently hugs belt 
• larger barrel - slightly more tension

UPDATE (old):

I noticed that one of my tensioners wasn't rolling so I updated the geometry of both files slightly to make it “more rollier.” Works great. I printed the clip in PLA and the barrel in PETG this time. The same print recommendations still apply. The “rollier.zip” folder contains both files. Have fun.

It may save you some time and heartache to read this entire description before starting.

PLA works good and lasts. PETG is a little smoother. If using an enclosure definitely use PETG or something else with better heat resistance.

You'll need to print 2x Clip.stl and 1x Barrel.stl to make one tensioner. I like to use two tensioners as pictured and print four clips at once and then two barrels.

The Barrel is printed in vase mode so follow the below print settings closely or it won't print correctly.

Important Print Settings:

I'm using OrcaSlicer, PETG, and a 4mm nozzle.

FOR THE BARREL ONLY:

Layer height: 0.16

LINE WIDTH:

Default 0.8

First layer 0.8

Outer wall 0.8

Arc fitting: Check

Elephant foot compensation: 0

Raft layers: 1

Spiral vase: Check (may be under the Plate settings)

If you're printing 2 or more barrels on one plate use Print sequence: By object

If you're experiencing droopy/melting walls in vase mode try reducing print speed and/or increase max fan speed and layer time in filament settings.

I've included a .3mf for reference.

Assembly:

Cut two pieces of filament 22-24mm long for each tensioner. Rub a small amount of super glue on one half of the filament and insert it into one of the clip halves as shown in the pictures. Be sparing and careful with your glue here - try not to glue your GD fingers to the desk! It helps to have the clip sitting on a hard surface so you can push the filament all the way down without over-shooting it. Once both pieces of filament are in one side of the clip put a little more glue on the exposed halves of filament. Get the filament ends just barely started into the holes on the other half of the clip BUT DON'T PUSH THEM TOGETHER! You have to get the Barrel into position before you snap the two halves together. Bob's your uncle. Hopefully the barrel isn't permanently glued to your shirt.

If you like “No Hardware Required” upgrades check this out: 

PROXIMITY_45 - An alternative printhead shroud for Neptune 4 printers.