X-axis bearings failure and scored rods again
The only problem that I ever have with my Mk3+ is the top x-axis bearings fail and score the rods. BTW: I am careful not to overtighten the bolts.
This time when I replace them, I am planning to replace all of the printed x axis and extruder parts just in case a problem with any of the original printed parts is causing this.
I have noticed that Prusa do not appear to sell genuine Misumi bearings anymore so I am looking at buying direct from Misumi. Does anyone know if I need the LMU8 or LM8UU bearings - and what is the difference? Also, would anyone know the part numbers for the genuine Misumi rods?
Thanks in advance.
RE: X-axis bearings failure and scored rods again
Are you lubricating the bearings at all? Lots of controversy re lube or don’t lube and best practices. Search the forums for some tips and lively debates.
It appears that Prusa is only carrying the less expensive LM8UU bearings in their parts store.
You can purchase original Misumi LM8U bearings direct from Misumi here:
https://us.misumi-ec.com/vona2/detail/110300026540/?HissuCode=LMU8
You can configure replacement rods on the Misumi site or purchase from the Prusa parts store.
Hope you find what you need.
Cheers
RE: X-axis bearings failure and scored rods again
Sorry I should have said that I have been packing the bearings with suitable grease prior to installation each time. Misumi do also sell LM8UU bearings and I was wondering what the difference is?
RE: X-axis bearings failure and scored rods again
I didn’t find the LM8UU bearings on the Misumi site. They sell for $1 dollar and change in the Prusa parts store, Amazon, etc.
The LM8U bearings sell for $8 dollars and change and are supposed to be higher grade although I don’t find specific comparisons when doing a quick search.
If you’re having the same issue repeatedly, I would try a different bearing set to what you’ve been using. Be sure not to over tighten the screws in the back of the extruder housing as that will pinch the bearings and cause premature wear.
Let us know how you make out.
Cheers
RE: X-axis bearings failure and scored rods again
You might find this link of interest:
https://prusacommunity.com/set-your-bearing-straight/
Cheers
RE: X-axis bearings failure and scored rods again
I would **STILL** like to know this Big Burning Question (and yes, I've read just about everything on the topic posted over the past few years).
What, specifically, is the lubricating material that comes on the Prusa-supplied bearings? (Or more specifically, what, specifically, was the lubricating material that came on the Prusa-supplied bearings ca. January 2020?)
Is it:
1. The 'shipping lubricant' that comes on many Mitsumi bearings?
2. Some other lubricant that Prusa ordered to be supplied with the bearings?
3. Some other lubricant that Prusa installed on the bearings?
4. Something else?
I have yet to hear the answer to this question directly from anyone at Prusa. I've heard statements dancing around the answer, but nothing that directly answers the question posed above.
RE: X-axis bearings failure and scored rods again
@jsw - I’m with you on this question. I’ve read plenty ‘unofficial’ info and followed the lively debates here on the forums, and elsewhere, all with no official position offered by Prusa, at least to my knowledge.
Im not sure we’ll ever get an official clarification one way or the other. The answer to this mystery is the chimera of the Prusa printer world and it almost seems they want to keep it that way.
At the end of the day, like so much in the 3D printing universe, I think folks have to find what works for them and then keep doing that. Of course the frustrations (and often expense) that goes along with the search for ‘what just works’ can be maddening and time consuming.
I try to keep up with regular maintenance on my printer and I’m currently utilizing different methods of lubrication for the X and Y axes to see if one is clearly ‘better’ than the other over time. I’ll post more on this when I have something concrete to share.
In the meantime, happy printing and happy holidays!
Cheers
RE: X-axis bearings failure and scored rods again
The Prusa Powers That Be appear to be suspiciously silent WRT what that goo that comes on the bearings actually is.
My conclusion is that whatever it is, the Prusa folks have determined that it is more than adequate to lubricate and protect the bearings over their expected lifetime under the load presented to them by the printer.
They (Prusa) have thousands of these machines printing in their 'farm', and if there were bearing lubrication or failure issues, they would know about them.
The machine I have just passed 21,000 print hours. It's still printing just fine, with no scoring of the rods, no bearing noise, and no perceptible 'play', friction, or 'slop' on the axes.
Every so often I put a drop of lightweight synthetic machine oil on the rods. Every so many so oftens I'll rub a dab of Superlube on the rods.
RE: X-axis bearings failure and scored rods again
RE: X-axis bearings failure and scored rods again
I don't think they are wrong. The lubricant supplied, at least in my case, has been more than adequate.
I think they may be shy to admit that they are indeed supplying the bearings with a lubricant that is intended to be temporary, even though it's proven itself to be adequate for the purpose at hand.
RE: X-axis bearings failure and scored rods again
That's the point; Prusa isn't doing anything with the bearings. When you buy a kit from Prusa, they come sealed in the same Misumi packaging, packed in the same light oil as when you buy the bearings separate elsewhere. Misumi has said that this oil is intended as a preservative, and not a lubricant. At least as far as the kits go, all Prusa does with the bearings is put them in the box along with the rest of the parts. I know this to be the case, because I bought the Prusa kit, and then within a couple of months after that, I bought the same Misumi bearings from a different supplier. They all came sealed in the same packaging, with the same preservative oil.
Whether or not this will cause any problems in service, or if Prusa is lubricating the bearings they use in the assembled units are different questions. The OP's issues with the bearings and rods don't appear to be due to lack of having been lubricated. I think he may be on the right track as far as replacing some of the printed parts goes.
RE: X-axis bearings failure and scored rods again
@brad-2 -
FWIW, when you do the re-assembly of the extruder housing, be sure not to over-tighten the 2 zip ties in step 49.
https://help.prusa3d.com/guide/5-e-axis-assembly_169235
I’m not sure if you can tighten the zip ties enough to distort the bearings, but if it’s possible, such a condition could lead to premature bearing failure and a scratched upper rod.
Cheers
RE: X-axis bearings failure and scored rods again
I do tend to tighten the zip ties up as much as I can but make sure that the backplate is not screwed too tight. Next time I will be more careful with the zip ties.
I am in the process of ordering genuine Misumi bearings and rods directly from Misumi and when I install these I will make sure that I do not align the two bearings exactly the same so that the ball positions are offset slightly on the rod too.
RE: X-axis bearings failure and scored rods again
Sounds like a plan. Please let us know your results.
Cheers