This is v2. It uses square nuts and other screw lengths.That is why I made it it's own thing.
This is still a remix of a very smart part.
Printing the idlers standing up makes them very sturdy because force from pulleys are not between layers.
See original part from brunofporto for more information of why this design is superior. Much better explanation than I can give.
This part is a remix to fasten the idler on two sides of the 3030 frame and will take a 10mm rod.
The idea is to use square nuts instead of usual hexagonal nuts. Square nuts are bigger and don't turn inside the hole, making it tighter. The middle hole uses a nyloc, nylon locking hexagonal nut.
It now needs a 50mm M3 screw in the middle, holding the idlers. This makes it sturdier. There is still 6mm of room to fit a nyloc nut and not overtighterning.
You can also use a tap to tap the 3mm holes or drill them to easily fit the m3 screw.
You need to make a regular part and one mirrored on Z axis for each idler setup.
The part without groove fits over hidden L brackets inside the 3030 corners, usually on top while the one with groove is for the bottom where there usually are no inserts.