Thanks for the comments, especially ones that contributed to my original question.
There's a number of people, particularly in the US using using 3d printed stuff like carabiners for lifting bear bags, lowering gear etc.
Here's a little vid of a tensioner, I think the advantage is that you can resize for different rope diameters etc.
I know there's other material, more traditional ones that work well but I find it interesting to think that it's starting to be possible for people to design and make stuff for themselves, even if that's just for experimenting etc.
As Pete said, (
@ESpy) there's lots of different materials ot print from, those with carbon fiber etc have very good strength to weight ratios and there's a lot of hobby printers that can handle it, even if it does wear out the nozzles faster.
I don't want a debate on the rights and wrongs of 3d printing, just a conversation about what works, what doesn't and the experiences of people that have used it or like stuff made from it.
@gra_farmer this might interest you.
a few little bits in this video