This is a great belt tensioner!

I printed it in ABS with 40% infill. After shrinkage it was a bit too tight around the bolt
&
amp; nut, but a perfect fit onto the T5 belt which is the most important.

Thanks for sharing these, they seem like a very clever idea. My X-belt is a little loose, though it seems to print ok. Rather than haul it tighter by hand and risk misaligning my vertical rods, I thought I'd try out your thing to see if a tighter belt made any difference.

I printed up a pair last night, straight from your .stl file. Here are some comments.

I'm wondering why you chose $fn=8 for the nut keeper hole, when hex bolts are six sided? My six-sided M3 nut wouldn't fit in the keeper hole, because of the eight-sided hole. When I tried to pull it through wit
h a bolt, the sides sheared away (PLA is brittle like that - I guess I could have heated it with a hairdryer while forcing it).

The slot for the T5 belt was a little too thin to accept my belt, even though when I measured my belt it's "tBase" and "tFull" values are smaller than those in the opensca
d code.

I found that a 20mm bolt was way too short for the tensioner as printed from the stl. I don't have any 30mm M3 bolts on hand, but I'd guess that would be the minimum length.

I realise that I could just edit the openscad file and generate a bespoke version for my printer, but I thought you
might like some feedback. There are a bunch of mysterious constants in the openscad file that won't scale when I change part dimensions, so there'd be a bit of trial and error (do we call that "product evolution" now :) ) involved.

Your design is very cool. I have great respect for folks like you
who can describe a complicated object in less than a dozen lines of openscad code. Thanks again for sharing your work.