Ok guys so I just got my lm6uu bearings in and they don’t all feel smooth on the smooth rod. Some feel really nice but half don’t feel really good and I can feel some very slight binding.
So is this normal for new bearings?
Do I need to just break them in?
I have noticed if there is some pressure put on the bearing it tends to slide smoother. Sometimes.
@Wayne_Friedt that’s what I was thinking. I put a little pressure and they felt slightly better. What should I do? I know it’s not the rods because some bearings work perfect.
Do you think they need to be broken in?
Related: I just rebuilt my Simple and the linear bearings feel stiff / jumpy. I’m fearing a piece of dirt or something has got into the races - is there a way to clean them? or am I out of luck?
@Griffin_Paquette I coat the balls inside with some sowing machine oil and run em. I see a lot of people use that white lithium grease which i think should work well as well but that is not available here so i use the oil.
I have a ton of lithium grease so I’ll try that.
In my experience, the way to handle this with most the LMxUU bearings is to pack them with grease first. Hold one finger over the end, push a heavy grease into the other. Then, continuing to hold your finger over the end insert the rod. This should push the grease into the bearing holder.
I make sure all the rods I send out are pit free but if there is any rust on your rods there will be small pits. A little metal polish will help with small amounts of rust.
To relate though, yes once you load the rods and travel them along the axis several times they will smooth out much more.
@Wayne_Friedt and @Brandon_Satterfield I really appreciate the help. I haven’t used these types of bearings before and I kinda expected them to be glassy smooth off the bat I will definitely do the grease method and I will put a load on them as well.
Thanks again!
Griffin
About loading - post assembly experience supports the idea loading helps. I am not seeing any artifacts or hearing any binding/straining while printing - so the bearings are certainly working “good enough”. I guess time will tell if they are damaged or not…
I think part of the problem is a lack of practical experience. I ordered another pack of 10 for my delta as I thought the bearings were causing issues…turned out two of the three pullies had seized and that all the linear bearings (which had been a little stiff on first installation) were as good as or better than the new replacements.
Lubrication, as mentioned, is key…the delta would go for a good long while then some part would get stiff and throw the print quality way off. Six linear bearings, 3 pullies, and 12 ballpoints later and it’s back to smooth walls and quiet movement.
So @Mike_Miller you agree that they will break in?
Yup, but do pack them first…there’s no telling what the low bidder uses in there during manufacture. 
Very true. I guess you get what you pay for. I’ll pack them first thing when I start working on it again. And I’ll report back. Thanks @Mike_Miller
Pack 'em, then run them for 2-10 hours and recheck. Replace the ones that are still stiff. You’ve STILL saved 80% over reputable bearings. 
@Mike_Miller do you think that’s bad for the motors atall?
Well, there are degrees of stiffness. 
but those motors are stout and designed to handle loads a lot higher than we typically see.
None of them take tons of force. I don’t feel like any are binding like crazy and I put the best 8 on my smartrap so I think they should be fine. Fingers crossed!
Just to report back. The white lithium grease worked PERFECT!! Thanks guys. They are running very smooth now!
Remember how it works now. In a few months you’ll be wondering if it always made that weird vibratey noise…only to have it go away when you retention or lubricate something.