Bearings going bad?
I recently built my printer and have been in the process of tuning profiles/getting used to it. I have had a CR-10 for a couple years, so have just been getting used to the new machine.
After about my 3rd print, I noticed small amount of buildup on my upper rod for my x-axis gantry. It is dark grey, and seems to be filled with very fine metal flecks when viewed with a bright flashlight. I have continued printing (now have roughly 16 hours of printing). attached is a picture after a short (~45 min print) I wiped the buildup off the rod with a clean cloth, and applied a very light coating of super lube on the rod before the print. It looks darker in person. 
Is my linear bearing going bad already? I have seen posts with people having issues with linear bearings, and associating it with rough handling during assembly of the kit, so I treated the steps involving the bearings with extra care during the assembly process. I do not see how they could have been damaged during that.
Any input from the more experienced? I am not used to linear bearings/rods, coming from a cr-10.
Thanks so much,
-Seth
RE: Bearings going bad?
Are there any horizontal scratches visible on the X rod?
It might be worth washing and re-lubing the bearing if the grease inside is contaminated by metal particles. That way you'll see how much was there and also slow down the possible decay.
RE: Bearings going bad?
I had inspected the rod and had not found anything but i just inspected it again and found a scratch on the back side of the rod, about .75mm wide and roughly 10cm long, in the center of the rod. 🙁
RE: Bearings going bad?
That's where the metallic flakes are coming from. Both the bearing that caused the scratch and the rod will need replacing. Welcome to the club:
And you may be interested in looking at this thread.
RE: Bearings going bad?
Wonderful.. didn't even get 20 hrs out of the printer. 😬
What would your recommended route for replacing the parts be? I'm also assuming when I do replace the bearings, to wash them and pack them with super lube before installing? Anything that can be done to help prevent this? Or just luck of the draw?
EDIT: Oops - just saw your link to the other thread.
RE: Bearings going bad?
Wonderful.. didn't even get 20 hrs out of the printer. What would your recommended route for tha...
Contact Prusa support via chat.
RE: Bearings going bad?
Prusa is pushing expectations here. Bearing manufacturers unanimously say to clean and lubricate bearings before installation and use. Prusa bearings ship with a light oil intended as a rust preventative, not a lubricant. Some printer will work for a while, but left unlubricated, expect less than six months before the bearings are too worn and the X abd Y axis are suffering too much play.
The black debris is the grease seal wearing away on the dry rod. The metal flakes are bearing dust and probably some rod dust.
RE: Bearings going bad?
Wonderful.. didn't even get 20 hrs out of the printer. What would your recommended route for tha...
Contact Prusa support via chat.
This. They'll send you new rods and bearings. When it happened to me mine arrived in two days.
RE: Bearings going bad?
Thanks for all the help - I really appreciate it. I'll get on the horn with the support people.
That being said, should I look into just getting misumi bearings if I am going to be taking everything apart to grease the old bearings? Or are things good enough once they are properly lubricated?
RE: Bearings going bad?
You should at least replace the ones that scored the rods, and keep an eye on the others. The blackening of the lube, as noted, is often a sign.
I'm currently actually running Vesconite bushings instead of bearings for my own peace of mind after having had two oversized rods and some bunk bearings. Very quiet, and actually cheaper than Misumis (where it's recommended you get matching rods, for a total of about $100). The Vesconites are made for stock rods. (I'm told the running clearance specification is +/-0.05mm, or 0.002")
https://www.vesconite.com/3d-printer-promo/
Cost (at time of writing) is either $3 or 5 each depending if you go with "Hilube" or "superlube" impregnated. I'm pretty sure that even the hilube ones are fine given the relatively light load of a 3d printer. If you are willing to wait for the slow boat from Johannesburg, shipping is free; otherwise it's $15 for UPS.
I have some videos of them in action in my thread "Anyone tried vesconite yet?"
RE: Bearings going bad?
I replaced my worn OEM bearings with Misumi. They were a definite improvement. But they are now showing wear, even though they were properly greased before installation. Though I wonder if it isn't due to rod wear that happened before I greased everything.
My next purchase will be a set of Misumi rods and bearings.
I may - depending on what experience Vintage has (:-) try the plastic bearings, too.
Applying a light oil on the rod and running the axis back and forth a few times will give you a bit longer. Taking things apart at this point may not be very useful - unless you are bored and need something to do - though, rethinking it, 20 hours isn't that long and it may be worth the effort.
RE: Bearings going bad?
I was super careful building my Mk3 when I got it in December. My LM8UU's from Prusa failed rather quickly, within a month or two. I replaced the bearings with Misumi LMU8's and matching rods from the Zaribo web shop. I'm now at 2047 hours print time total, most of it on the Misumis. I'm re-packing the bearings everytime I take the printer apart with Zeller+Gmelin Divinol Lithogrease 000/150. Meticulously made sure the printer is square and there is little load on the bearings across the whole length of the rods. So far no signs of wear at all, the printer is running precise and quiet.
The reasons I chose a NLGI 000 Lithium grease with a low-viscosity base oil (380 mm²/s) and without solid additives are both theoretical (it's what Misumi recommends plus what comes out of the equations when you plug in 3D printer loads) and practical (I used a NLGI 1-2 Mogul LVT 1-EP before and after thoroughly packing the bearings the balls simply didn't move at all, and were sliding on the rods, scoring them immediately).
At this point I have no plans to switch to bushings. If anything, I'm thinking about an upgrade to SKF LBBR8's. They have twice as many raceways compared to Misumi LMU8's, simply a different league yet.
RE: Bearings going bad?
You should at least replace the ones that scored the rods, and keep an eye on the others. The blackening of the lube, as noted, is often a sign.
I'm currently actually running Vesconite bushings instead of bearings for my own peace of mind after having had two oversized rods and some bunk bearings. Very quiet, and actually cheaper than Misumis (where it's recommended you get matching rods, for a total of about $100). The Vesconites are made for stock rods. (I'm told the running clearance specification is +/-0.05mm, or 0.002")
https://www.vesconite.com/3d-printer-promo/
Cost (at time of writing) is either $3 or 5 each depending if you go with "Hilube" or "superlube" impregnated. I'm pretty sure that even the hilube ones are fine given the relatively light load of a 3d printer. If you are willing to wait for the slow boat from Johannesburg, shipping is free; otherwise it's $15 for UPS.
I have some videos of them in action in my thread "Anyone tried vesconite yet?"
I initially looked into the possibility of running IGUS bearings, but I have seen talk about those not being the proper thing to use, and have too much play, or wear down. Cant remember what the issues exactly were but it seemed that people were generally against them.
Are the Vesconite bushings better suited for the application? I would be interested in seeing the results of them..
I replaced my worn OEM bearings with Misumi. They were a definite improvement. But they are now showing wear, even though they were properly greased before installation. Though I wonder if it isn't due to rod wear that happened before I greased everything.
My next purchase will be a set of Misumi rods and bearings.
I may - depending on what experience Vintage has (:-) try the plastic bearings, too.
Applying a light oil on the rod and running the axis back and forth a few times will give you a bit longer. Taking things apart at this point may not be very useful - unless you are bored and need something to do - though, rethinking it, 20 hours isn't that long and it may be worth the effort.
I was super careful building my Mk3 when I got it in December. My LM8UU's from Prusa failed rather quickly, within a month or two. I replaced the bearings with Misumi LMU8's and matching rods from the Zaribo web shop. I'm now at 2047 hours print time total, most of it on the Misumis. I'm re-packing the bearings everytime I take the printer apart with Zeller+Gmelin Divinol Lithogrease 000/150. Meticulously made sure the printer is square and there is little load on the bearings across the whole length of the rods. So far no signs of wear at all, the printer is running precise and quiet.
The reasons I chose a NLGI 000 Lithium grease with a low-viscosity base oil (380 mm²/s) and without solid additives are both theoretical (it's what Misumi recommends plus what comes out of the equations when you plug in 3D printer loads) and practical (I used a NLGI 1-2 Mogul LVT 1-EP before and after thoroughly packing the bearings the balls simply didn't move at all, and were sliding on the rods, scoring them immediately).
At this point I have no plans to switch to bushings. If anything, I'm thinking about an upgrade to SKF LBBR8's. They have twice as many raceways compared to Misumi LMU8's, simply a different league yet.
I'll be contacting Prusa, and I may end up going with misumi if I don't find any other alternatives if/when my replacements wear out - not sure how i feel about bushings, as I have not done enough research on that yet.
I was also incredibly careful when assembling the printer, since I have heard of the delicate nature of linear bearings, and all the warnings in the manual. Just wish there was a note in there or instructions that would inform the user to lube the bearings before install. Maybe I could have avoided this whole mess.
RE: Bearings going bad?
If it's any consolation I did lubricate mine properly on first assembly and still had failure very early on. It just boils down to questionable tolerances on the parts, I think.
I initially looked into the possibility of running IGUS bearings, but I have seen talk about those not being the proper thing to use, and have too much play, or wear down. Cant remember what the issues exactly were but it seemed that people were generally against them.
Are the Vesconite bushings better suited for the application? I would be interested in seeing the results of them..
Yes. The problem with the IGUS ones is the ones most people get are meant to be press-fit and therefore too loose. There are other offerings from them that come in a metal shell which are supposed to not need a press fit but I too have heard grumblings about the tolerances on those.
The Vesconite ones are direct drop-in with no press fit needed, and made specifically for Prusa printers (the lead designer made them for a Mk2, IIRC).
My experiences are (and will continue to be) documented here:
I am very happy with the performance of the $3 "Hilube" version; the slop I am referring to at the end of the thread (as of this writing) is only observed in the Superlube ($5) variant. I'm currently in contact with Juan and we are investigating; I will follow up what the outcome is.
For the price being what it is my current take is it's a viable contender if you want the benefits of a bushing over a bearing, and a very reasonably priced upgrade over the stock, compared to a full set of high-quality bearings and/or rods. I have only replaced my X and Y; I do not feel a need to do Z as it is under almost no load; the bulk of the load is on the T nuts and lead screws there. The rods and bearings serve only for alignment and stability.
My prints are coming out pretty darn good right now; I am at a point where the primary artifacts I am observing are the actual motor steps (VFAs) on X and Y. Happy to answer any specific questions you might have.
RE: Bearings going bad?
If it's any consolation I did lubricate mine properly on first assembly and still had failure very early on. It just boils down to questionable tolerances on the parts, I think.
Yes, even though Prusa has picked one of the better suppliers of LM8UUs among what horrible ones are out there, there is still a lot of variation of the bearings, of the rods and also there is size differences in printed parts.
RE: Bearings going bad?
SKF LBBR8 bearings have 4 rows contacting the rod, the same as the LMU8. They do have the self aligning feature which might be good for the Prusa frame design.
Misumi LMK8's have 6 rows in contact, but require a sleeve to accommodate the smaller OD. They are what I installed. I can't say they are any better than LMU8's ... since they are already showing wear. But then, as I said earlier, the rods I put the Misumi's on were the original already damaged goods. I looked at the X rods today with a lupe - and they are grooved where I set the original bearings; but look okay where the Misumi's are rolling. Will use a scope on X and Y rods after this part is done.
RE: Bearings going bad?
SKF LBBR8 bearings have 4 rows contacting the rod, the same as the LMU8. They do have the self aligning feature which might be good for the Prusa frame design.
You're right, I was looking at a picture of a bigger diameter and didn't notice the number of rows changes with diameter.
RE: Bearings going bad?
Just updated my Vesconite thread with some additional pics for anyone interested.
RE: Bearings going bad?
Thought I'd give an update on the status of things.
Thanks again for all the continued input/discussion/information!
I contacted Prusa support about the bearings and rods, they asked for a picture and video, and said they'd have new bearings and rods right out to me.
So my current plan is to replace my x-axis hardware, preparing the bearings properly beforehand, and really paying super close attention to how hard I am tightening down the screws on the back of the extruder carriage. I really don't think this was the issue before, but just in case. I am also going to service my Y-axis bearings, wash them, re-lube. If that proves to last then great. if not, I'll be looking towards the Vesconite bushings.
EDIT: I took a picture of the scratch. Hard to capture on camera.
RE: Bearings going bad?
Alright - update time.
I received the new bearings and rods, i washed the bearings, re-lubed them with a bit of superlube, and then reinstalled everything (did this on the x and y axis).
About 12 hours of printing later, I am seeing the same nasty black grease buildup on my upper x-axis rod, and there is already a scratch on the front of the rod.
At this point I am quite disappointed. I was very careful to choose the smoothest running bearings out of the 5 that were sent to me, I was extremely meticulous when installing the bearings and paid attention to orientation, I also took care to not over-pack the bearings with grease and just put enough to lube the bearings, and a light coat on the rods. The x-axis was buttery smooth after I was done.
But again after a very short amount of time printing, already have scratching. I have one extra rod that is good, and two extra bearings, so I could perform the procedure again, but this just doesn't seem right.