Has anyone tried coating the contact surface of standard metal ball bearings like 608ZZ with something like nylon, teflon, polyethylene etc to reduce the wear when running them on aluminum profiles as linear slides?
How would you bond it? Or, are you talking about the lubricants that contain Teflon?
Zz have shields on both side. Also if you place material over balls you will increase the sphere radius.
If you reduce the friction will the ball bearing roll? Or will it slide?
I don’t think that can be a good idea 
@Carlton_Dodd that’s exactly what I am wondering. Nope, not lubricants. A solid coat.
Just throwing the question out there if anyone has done it, it’d be interesting to know how.
Buffing the surface and epoxy? Gluing? Friction welding? Melting? Anodizing? Spraying?
@Christian_Filippi
I think @korpx is referring to the outside surface, when the bearing itself is used as a wheel.
@Christian_Filippi ah, no not coating the individual balls. Coating the outside of the bearing so to speak. To reduce the wear when rolling the bearings along the aluminum.
A usage scenario like this for example https://www.buildyourcnc.com/images/linear%20bearings.jpg
@korpx
Might be easier to bond Teflon strips to the aluminum profile.
@Carlton_Dodd yes that’s one way to do it. But I find it interesting to do it the other way around, to prepare the bearing and roll away on any profile. Why make it easy eh… 
My bad, sorry
btw, if you have too slippery surfaces i think that the bearing is more invited to slide instead of rolling.
You don’t want to reduce the friction on the outside of the bearing. Let the rolling part do the rolling job. If it slips, there’s a potential for wear or vibration…a bearing will out perform a bushing nearly every time. (And a sliding bearing is approximating a bushing. )
@Mike_Miller if your comment was for me I do not want to reduce friction. I want to minimize the wear on the aluminum from the steel bearing.
Note that my question does not come from having a problematic machine. My printer use delrin wheels on Makerslide and works just fine with that.
I am simply investigating possibilities for alternative linear slides, with this specific setup - steel bearings rolling on aluminum profile.
Gotcha. At the loads we’re seeing, there shouldn’t be a lot of wear, but I see your point. Lets face it, 3d printers don’t generate high loads, or comparatively high cycle counts. Not compared to, say, the wheel bearing in a car (1/4 of two tons for 100,000 miles).
@korpx
Not the direction you were going, but how about a replaceable sacrificial strip on the aluminum? I was thinking something like vinyl shelf paper, cut to fit. It would probably quiet the movement a bit as well.
I’ve found isolating the motor generally does more for quieting a system, assuming all the other moving parts are well lubricated. You’d also want to ensure the sacrificial layer doesn’t add noise to the system, either by changing the geometry (being squished) or by picking up contaminants (I have an Elliptical excercise machine that HATES dust bunnies. )
Still, there’s plenty to be learned here. I had an experiment with aluminum sliding on a layer of teflon tape on aluminum. It worked…reasonably…until I introduced any kind of lubrication.
Got rolls of paper? I work at a place that prints mail on giant rolls of paper, so I have plenty. You may be able to wrap the aluminum extrusion with paper just over 1 time. Make sure the tape/glue that you use to hold the paper on the aluminum extrusion is on the opposite side from the bearings. Christmas paper may be a good source of paper for that. Just be mindful that if the paper bunches or rips, it could cause trouble. By the way, I have never tried this.
@Mike_Miller I agree the loads aren’t huge though I do expect wear pretty quickly especially in cases where a heavy direct extruder and X carriage is thrown around at respectable accelerations. Steel is hard and aluminum is soft that’s for sure.
@Carlton_Dodd and @NathanielStenzel thanks for the suggestions. I don’t want to go the “put something on the extrusion”-route just yet. I am pretty fixed on the idea of experimenting with the rollers rather than the surface they roll on.
Delrin wheels with ball bearing hubs work beautifully on aluminum, but I am pretty fixed on finding a more DIY route to a similar linear slide idea. Rollers you can make yourself without a precision lathe and special tooling.
@korpx rubber tubing?
Try to find polyurethane tubing with the ID smaller than the bearing OD and press the bearing into it. Another option is to use heat-shrink tubing.
@Mark_Fuller I was thinking about suggesting heat shrink tubing, but then I considered the idea that it might be unevenly shrank resulting in oddities in the movement.
Come to think of it, rubber tubing might degrade into sticky goo if you use the wrong type.
At any rate, using a tubing and then cutting it so it did not have alot of excess on each side (but you will surely want it grabbing the sides of the outer part of the bearing) would be a good idea. I figure it would let you buy a tube of whatever cut it after sticking it on the end and continue for however many bearings you want really cheaply. I guess the question is, would it pinch and then cut/deform during the operation of the machine?
@Mark_Fuller , yes @Shauki is using some rather exotic bearings in teflon tubing on his Quadrap where the shape of the bearing alone keep the tubing in place;
https://plus.google.com/103855138756399157123/posts/Dn2jvQiZuHQ
However some sort of coating would give you a wider choice of bearings.