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2 tight x-axis bearings  

New Member
2 tight x-axis bearings

Good morning all.

I have a question regarding the x-axis bearings, and bearings in general. I received my MK3 kit yesterday and when putting it together I got as far as the x-axis and noticed that one of the bearings was moving very smoothly along the rod. If I turned the rod vertically the bearing would drop under it's own weight. However, the other 2 bearings are tighter and won't move without a bit of a push and stop moving as soon as I stop pushing. They seem to move ok with the extra force and there doesn't appear to be any grinding. One of the tighter bearings does not rotate around the rod very easily, but the other 2 do.

With the looser bearing, there is a tiny amount of play, that isn't there with the tighter bearings. Is it expected that there will be differences in the bearings supplied and will it cause any problems later in the build or when printing?

The y-axis bearings and bed seem to move quite freely without the belt attached and I have tested the z-axis rods/bearings and they seem quite free as well.

As this is my first 3D printer, I'm not entirely sure what to expect. Though the looser bearing is more how I imagined a linear bearing would feel.

Any advice you can offer will be gratefully received.

Many thanks,

Posted : 26/10/2018 1:09 pm
Reputable Member
Re: 2 tight x-axis bearings

There will be some variance in these bearings, as they're not exactly made to NASA specs. 😉

That said, the tight ones may loosen up a tad as they move back & forth a few (dozen?) times and "settle in". I'd be more concerned about the one that has play in it. They may all get that way eventually, and need to be replaced. (I seem to recall that they may need replacement annually, depending on usage. YMMV) If you think you got a bad one, contact CS via chat or email.

See also: Regular maintenance: Bearings, Fans, Extruder driver gear, Electronics & PEI.

That's "MISTER Old Fart" to you!

Posted : 26/10/2018 6:36 pm
Re: 2 tight x-axis bearings

Hi Barry,

Linear bearings are not intended to rotate freely. so the one that does, is probably on the loose side,

have you tried exchanging the bearing /shaft allocation, you might find the loose bearing fits the other shaft better and vice versa

regards Joan

I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK

Posted : 26/10/2018 8:52 pm
Estimable Member
Re: 2 tight x-axis bearings

I recently had to replace X-axis bearings, these obviously take the most abuse, *especially* if you are a noob like me and haven't learned proper technique when replacing/upgrading extruder assembly parts. They are fragile. So yea, anyways, I put the 'best bearings on X, second best on Y, and worst on Z. Best for me is the smoothest ones that have no slack (I haven't ever had one that has any slack though).

I slide the bearing on the rod and rotate it gently, and sure enough at some angle they often scrap, a problem that gets worse quickly and eventually starts ruining prints.

There is also the option of printing your own PLA bearings, and while everyone and their dog will say how that is a bad idea, apparently if you are willing to take the time (a lot of time apparently) to print them correctly, and grease them with lithium, they just might outperform 'real' bearings. I reiterate, it may take a huge investment in time to get them printed right and broken in properly, but if you enjoy such labours, why not try? I've read reports that properly made ones last longer than these metal ones.

Posted : 27/10/2018 3:15 am
Honorable Member
Re: 2 tight x-axis bearings

If I knew what I know now before I assembled the kit. about care and feeding of these linear bearings I would have cleaned the light protective oil out of them and packed them with a proper grease either lithium or synthetic or molibedamn type. I have printed a greaser (several designs are out there in places like Thingiverse) and will do it next August when I give the printer it’s anual major service. Until then I will put a drop of light spindle oil (sewing machine oil or even 3 in 1 oil) on each side of the bearings and then wipe down their rods with a clean cloth as part of the weekly service

Posted : 27/10/2018 3:01 pm
New Member
Topic starter answered:
Re: 2 tight x-axis bearings

Hi All,

Just wanted to post a quick update and thank you all for the advice and feedback. I finally got back to the build yesterday and tried Joan's advice of swapping the rods and bearings around. The bearings are now a much better fit. One is still a bit looser than the others but the play has gone.

I'm a lot more confident that the printer is going together correctly now. I wasn't expecting aerospace precision 🙂 , but the difference between the bearings threw me a little and your replies have got me back on track. They have also given me some pointers to keep the bearings running smoothly in the future.

Hoping to have the build finished tomorrow and be able to start printing.

Thanks again for the responses, they are really appreciated and have saved me a lot of stress.

Kind regards,

Posted : 30/10/2018 11:11 pm