3D Printed 15mm Belt Tensioner for Pro

Back in August, there was this thread about some 3D printed belt tensioner solutions. I was looking to make something like this at the time, but I didn’t have a 3D printer. 6-months later and I now have a 3D printer and decided to give it a go.

I wanted something like the designs in that thread but I wanted a design that prevented the plastic tensioner from deforming due to the tension, and kept the belt very close to the aluminum rail. I’ve got one I’m pretty happy with so far, though it needs a little tweaking.

The size of it fits into the small space but is beefy enough to withstand the pressure. By putting a guide along the top of the front plate, the tensioner doesn’t want to warp due to the pulling forces of the screw or the belt. I need to modify the model a little bit and add an additional 1/16” to the part that sits on top of the black end plate (there’s a green shim in the photos).

It seems to tune well and pretty stable so far. Looks like it fits in with the machine. Looking forward to seeing how it does over time.


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I had a request for the files, so here they are:

CNC Belt Tensioning Bracket - Clamp Body - Version 2.stl (122.3 KB)
CNC Belt Tensioning Bracket - Main Body - Version 2.stl (621.4 KB)

I printed the bracket right-side up, and the clamp upside down.
I was concerned about it possibly warping so i think i did a 50% infill…

For hardware, you’ll just need 3 M5X20 SS bolts and one 5MM SS Nut. The screw that holds it to the machine is the screw that tensions it.

There are no modifications to the machine necessary. This simply replaces the front belt clamps.
(Looking back at the above photos, I’m noticing that the one in the pictures above was a first-version that was a little off and required a thin shim. The version in the file is a second version that was adjusted to correct for this.)

I hadn’t previously mentioned this, but I also made one of these tensioners for the X-Axis belt:

Caveat: II never did a version 2 on this one. I had planned to but never got around to it. It requires a shim, and it has a bit more play than I’m proud of, but it’s also worked well enough for my needs and I’ve not ever had to fuss with it.

Same general design as the front tensioners. I don’t recall what hardware… I used whatever screws I had at the time lol as you can see in the photo. It’s not pretty but oh well.

Here’s the files for the Y-Axis
CNC Y Belt Tensioning Bracket.stl (319.8 KB)
CNC Y Belt Tensioning Bracket Clamp.stl (120.2 KB)

Lastly, this… it’s a plywood guide designed to hold two 1/4" straight bits exactly 500mm apart. It’s so nice for consistent tensioning using the “twang frequency” method. No file posted for this but simple enough to draw in CC.
I was having doubts about consistent belt tension so i was testsing frequently for a bit, and having this helped make it super fast to do so.

I hope these have been helpful! Please let me know if you print the design. Would love to see them!

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Thanks. I will have to get these files to a buddy of mine who has a 3D Printer. I have not invested in that yet.

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