Speaking of (hobby) 3d printing and loads, why don't I see printed parts combined with extruded aluminium profiles (rectangular tubes or T-shaped), threaded steel rods and some nuts+washers more often? Those reinforcement elements are cheap as dirt and should be almost as easy to work with as legos when you can guide all the difficult connections with bespoke printed adapters. What am I missing? (I have zero experience with 3d printing, I barely get beyond kneading a pack of Sugru...)
I work in robotics and this is very common for prototyping and also common for grad student projects. Here in Japan, Misumi will machine things like that to length and add whatever features you need, or even configure an entire assembly (eg a 6 sided box) and get all the parts delivered. I don’t recall the name of similar sites in other countries but they exist.
Other easy things to get a good result is use nuts or inserts instead of threaded holes when you can, and try to keep printed plastic parts in compression, not tension.
I think not enough people use sheet metal. Doing as you described plus sheet metal to put some material on the outside of the cross section not only looks professional, it adds a lot of stiffness. And for aluminum sheet 0.5mm or 1.0mm thick you can literally cut it with a knife and straight edge, and use a couple of pieces of wood or even books to make surprisingly nice bends. For thicker or more complex parts, it’s pretty easy/cheap to make or buy a decent brake, and also pretty cheap to get parts made from sites like I described above.
I think a lot of 3D printer hobbyists turned to 3D printing once it got good enough because we don't have space or easy access to even cut things or have a stash of parts. You're right, I can get a M6 x 1200mm stainless steel rod for AUD$5. But then to cut it accurately would need a few more tools. So you kinda try and limit things to what you have. And you can do quite a few useful things with just 3D printed piece and the odd screw here and there.
