Uploading the example as I have simply seen too many claims that "plastic bushings do not work", when using unsuited designs. This is one bit of folklore with with which I do not agree.

You have to use a design appropriate to the task, and means of fabrication.

I am not inventing anything, here. These are old ideas from examples I saw very long ago (though probably not made of plastic). Too far back to recall the source.

Most 3D FDM printers are simply not accurate enough to fabricate bearings that call for close tolerance. But you can achieve close tolerance in the end with careful design.

There are two design tricks here.

First, there are three lines of contact along the rod. Three points is sufficient to force exact placement of the rod within the bearing. As the two upper points are offset, the weight of the build plate is also forcing exact placement.

Second, the slot/plug in the bottom allows fabrication with less precision. When assembled, a hand clamp (or any substantial weight) forces the plug tightly against the rod. The bolt locks the plug in place, but does not press against the rod. This is how we achieve very tight tolerances, when our method of fabrication is less precise.

Note the design is for a 10mm rod. The test rod (savaged from an old printer) is actually 9.5mm. The bearing works fine as it is tolerant of small difference in dimension.

I soaked these in a light spray oil (something generic from the local hardware store, that also claims to contain Teflon and Silicone). The slightly porous nature of FDM is of advantage, in this case.

Tried both longer and shorter variants. The longer had more static friction, and I do not see any advantage, so uploaded only the shorter.

This example does not fit any specific printer. (I have an i3 clone, but the bearings are adequate, so no immediate need to replace.)

https://cad.onshape.com/documents/1532aaf93656f48208326251/w/292d915ebe3b02fd89b394a2/e/77fbea02fb4da7f0ecdf8ad4