This is a fully parametric linear bushing. You can change the length, inner and outer diameters, number of "spokes", height of spokes, width of spokes, etc. and Free CAD will automatically update the model accordingly.

The more bushing surface area is in contact with the rod, the more friction you will have. A bushing with "spokes" allows you to decrease friction by reducing the total surface area in contact with the rod. You can modulate this via the BushingLength, SpokeWidth and SpokeCount parameters in the DIMS spreadsheet in the FreeCAD model.

Shorter bushings have less contact, and so less friction. Thinner spokes have less contact and so less friction. Fewer spokes have less contact and so less friction, etc.

However, reducing surface area also reduces the strength of the bushing to outside forces, so you'll have to experiment to find the right balance for your use.

Kingroon

Yes

No

0.1mm

15%

Model should be printed vertically so as to not need supports. However, a heated bed will likely warp the bottom layers. Even a slight warp will mess up the tight fit on a linear rod, so print with a small raft to avoid this.

PLA works fine for experimenting, and maybe even for light use. The constant friction will generate heat which will probably deform them over time and loosen the fit, so other materials might be better for bushings. Nylon comes to mind.

Every thermoplastic material will deform slightly as it cools, so you should experiment to find the bushing diameter that gives you a reasonably tight fit. Not so tight that you can't slide it along the rod, unless you're willing to do this post-processing described below to get a truly tight fit.

If you want a great fit with smooth motion, print the bushing to it's really tight on the rod. So tight that you need to force it on, like lightly tapping it with a hammer. Then secure the rod with a clamp to a desk and heat up the end hanging in the air with a hot air gun (hair dryer will probably do for PLA).

Get it hot enough that it will slightly melt the bushing material, but not so hot that your bushing will completely deform upon contact with the heat. Once the end is nice and hot, slide the bushing across the area at least once, maybe even back and forth depending on how loose a fit you want. The heat will expand the rod's diameter a bit, and will melt the plastic on the "spokes" so once the rod cools, there will be a very tight spacing between the bushing and the rod.

After a little lubrication to fill in that spacing, the bushing should slide nicely but still have very little play.