X-axis rods now have a scratch in them - how?  

New Member

Hello all,

So I got my MK3S not long after the lockdown started, and after running through some rather intensive jobs I've developed a scratch along the x-axis upper rod, 90mm long from the centre going left.

So - what do I do now?

As it's now damaged it's obviously not going to get any better and the rod itself will need changing - and the bearings too I suspect. I suppose what I'm asking is how the scratch got there and how do I prevent it in the future. Could a print that detached itself from the bed and started pressing upwards into the nozzle have done it?

Posted : 20/05/2020 1:11 pm
Noble Member

Highly unlikely. Your bearings are dry and the hardened steel balls inside will have scored the rods. This is classic un-lubricated bearings. It’s probably Prusa’s biggest mechanical failing, they seem to think that the packing grease on the bearings is a proper lubricant when it is not. 

when you get some replacement rods and new bearings make sure To clean the packing grease out using ipa and then to pack them with a decent grease. You will get much more life out of them and far less issues over the long term. 

In the short term until then you could try applying a thin oil and working The axis back and forth to work the oil past the seals and onto the balls inside. This should be done regularly as the oil will tend to evaporate.  Once you have lubricated the old bearing you could also try rotating the rod so that the score isn’t in line with the ball bearings.  That will give them a smooth surface to roll along. 

Posted : 20/05/2020 4:04 pm
New Member


Thanks for the input - I didn't think the lifting print would affect it (PLA going into a hot nozzle merely results in messy nozzle *fnar*).

I've just read the Set Your Bearing Straight blog post as well so I know what I've got to do... and that's go shopping (yay upgrades!)


Posted : 20/05/2020 10:02 pm
Noble Member

I would recommend to lubricate everything and keep printing. I have also rod scratches on my printers and they perform pretty well on daily base. Just keep in mind that rods is a consumable product like a nozzle and everything else on the printer. The print quality will degrade over time and it's up to you decide when to replace each part. I'm printing a lot and even my MK2(s) have original rods/bearings.

PS: You could even rotate a rod a little bit, so the bearings are not touching this surface and keep using it.

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Posted : 20/05/2020 11:00 pm
JK Proto
Active Member

I have this exact same problem. I contacted support and got new rods and bearings, but after just a few hours of printing the new rod was scratched up.

bearings are fully packed with grease and the bearings aren't too tight. 

Posted : 26/12/2020 12:11 pm

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