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

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

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. 

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

@neophyl

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!)

Cheers!

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

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.

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

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. 

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

@neophyl

How would I go about rotating the rod? or are saying rotate the bearing? I just got my printer used and after a 2 print I noticed this scratch on the top x rod about 3 inches long...I put a little tool cleaner on the scratch and tried to see if it would just wipe off but no it is scratched. So do this I would remove the screws from the back of the assembly and that will loosen the rods? or the bearings. Just looking for guidance and are you suggesting replacing them right away?

Thanks Michael

RE:

Hi there,

I bought my second Prusa MK3S+ printer and after 20 printing hours a deep scratch appeared on the bottom-right of the lower rod of x-axis.
Well, I thought that it was caused by a bearing malfunction, wrote to Prusa support and they sent a new rod and bearing. 
After several printing hours the same scratch appeared at the same place!
I'm an engineer and after thinking for a while about this problem I decided to measure the distance between the rods from left side and right side. I just wanted to know are the rods parallel. And the measurements proved my fears - the rods were not parallel. The distance between them at the right side was ~ 0.24 mm wider than the left side. OMG!

So, I printed new X-axis parts from here https://www.printables.com/model/57217-i3-mk3s-printable-parts%2Fcomments/files and the problem has gone!

My advice is:  Check if the rods are parallel. If the scratch appear on the same place, I bet they are not parallel. Print new parts.

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

I had an "X" rod wear issue too, my rods were parallel though and my upper rod was the one affected. In my case the 2 linear bearings weren't concentric. I detailed my solution here.  --->  https://forum.prusa3d.com/forum/postid/528880/