Low Profile Adjustable Y Belt Holder

For my new Prusa MK3 Bear build I wanted an adjustable y belt tensioner. I wasn't really happy with any of the existing ones.

https://www.thingiverse.com/thing:2995737 would have been my first choice but go and try to find a good quality 16T idler. (Seriously - let me know!) The one thing I am not sure about is that while it levels the force vectors, it also increases the lever (at least for the front direction). So I am not sure moving to a 16T idler is really even that desirable. Maybe worth creating a 20T idler version of this.

Next runner up was https://www.thingiverse.com/thing:3069061 which also inspired my design.I didn't like that I'd had to cut the belt length to fit and getting to the adjustment screw is as hard as it can get. Plus the killer argument against: it just didn't have enough clearance to the belt.

https://www.thingiverse.com/thing:2904281 is not a bad idea. The rotating nut of the adjustment screw isn't the greatest design though. And it is quite bulky. But for now it's my plan B if my design doesn't prove good enough in the long run.

I am by no means entirely happy with my design - but it seems to improve upon the issues I've seen. It keeps the 20T idler as is. It has the same small form factor as the original Prusa design. You don't have to cut your belt to length. It has (just enough) clearance. And the adjustment screw is (still not great but) a little more accessible as it's on the other side where there is more space between the belts.

I still see a few possible improvements. The screw-on plate could interlock with the lower part to improve stability. But I think I give this a try first before I make it more complicated.

There are two versions. If you have your printer dialed in perfectly the bridging version might work for you. I've instead printed the non-bridging version and just used super glue to get a perfect top. It's also a good idea to put a little glue on the square nut so it doesn't pop out so easily when not under tension. The hex nut has a one layer bridge that needs to be drilled through. That way it prints without support. It's a good idea to re-drill the holes as post processing step anyway.

1x M3 hex nut

1x M3 12mm countersink screw

1x M3 square nut

1x M3 35-45mm screw (depending on how much adjustment range you want, 45mm is the max or you hit the motor)

super glue

3mm drill

Sorry for using the GPL but I use the Prusa code as a starting point.

Print Settings

Printer Brand:

Prusa

Printer:

Prusa Mk2

Rafts:

No

Supports:

No

Resolution:

0.2

Infill:

30%