Mk2 Bed Bearing Failure
So i've had my Mk2 for about a month and have been using it relatively often and just suffered a bearing failure, wanted to tell everyone my story as it may help them. I had reused the bearings from my Mk1 kit (was only a few months old) against my better judgement and experience which tells me to never reuse bearings. I had just started a long print that had a tight deadline and suddenly discovered a few ball bearings under the print bed and instantly my heart sank as i knew what had happened.
I looked throughout the area and was only able to find ~10 balls, so i determined that i had not lost full functionality of the bearing and since it was on the side of the print bed with two bearings, it was worth the risk to continue the print. I also checked the rails to ensure they weren't being scratched or galled from the bearing sliding across the surface and did not see any damage, giving me more confidence to continue the print. Oh, did i mention this was a 41 hour print? 😆
Well, last night the print finally finished (successfully!) and this morning i popped my bed off and replaced all three bearings as well as gave them a nice coating of Krytox grease (yes, i believe in overkill...but i had it on hand, so why not?) to prevent this from happening again.
After this experience, I would strongly recommend to others that they lubricate their bearings before use. The oil that comes on the bearings is NOT a lubricant meant for service, it is purely a rust inhibitor to prevent corrosion during storage and shipping. I recommend using an NLGI 2 synthetic grease if you have it on hand.
As far as root cause, i suspect that lack of lubrication and also over-loading contributed to the bearing failure. Josef has previously warned about removing prints from the bed as it can cause damage and i think that is precisely what happened to me. I'm actually going to think about modifying the Y-axis to take larger rods/bearings if possible to reduce the chance of this in the future...
Anyway, here are some pictures from it happening and also some proof that it was a 41 hour print 😉
Re: Mk2 Bed Bearing Failure
Hi Kevin
Environment matters.
This used to happen to me a lot with my first printer (a Chinese clone); but I did have a tendency to lubricate the bearings regularly as well.
Since I started using the Prusa printers (last November) I have always cleaned new bearings with IPA and run them dry. Never had a bearing fail since I adopted that approach and I have both a Mk1 and Mk2 running 24/7 currently with 80+ hour prints.
I should just add that my printing environment is a very dusty office; I clean out my PCs every 2 months. The dust was previously mixing with the lubricant and creating a very abrasive mix.
I am building a third printer (base on the Prusa frame) and am trying PLA printed bearings for that; they do seem to be OK at the moment, but I don't know how long they will last.
Peter
Please note: I do not have any affiliation with Prusa Research. Any advices given are offered in good faith. It is your responsibility to ensure that by following my advice you do not suffer or cause injury, damage…
Re: Mk2 Bed Bearing Failure
Hi Kevin
As Peter says enviromment matters. I suggest you don't use IPA India Pale Ale my favourite beer 🙂 ohhhh dohhh Peter meant Iso Propyl Alcohol lol 😉
One drop of real sewing machine oil applied to the axis rods will lubricate the bearings. But recognise as Peter says depending on your environment, dust may become an issue and lead to bearing failure also. My bearings have been oiled no issues.
Nigel
Life is keeping interested and excited by knowledge and new things.
Re: Mk2 Bed Bearing Failure
Oh yea, environment will definitely have a large impact on the bearing life. I typically wipe down the ends of my rails pretty regularly (whenever i see any build up) to reduce the chance of ingesting anything into the circulating ball paths, but it's good that the bearings also have seals.
I have a feeling that abuse and over-loading were more of contributing factors to my issue since i've been printing PETG which was giving me TONS of trouble to remove from the bed and i was definitely exerting more force than i would've liked to remove them. I'm going to look into modifying the Y-axis rails for sure as i'd like it to be bomb proof if possible 😀
EDIT: Just found out that i can use some SKF LBBR 8-2LS bearings as exact swaps with the LM8UU and get almost double the dynamic load rating on the bearings. Going to try to find a cheap source for these and test them out.
Re: Mk2 Bed Bearing Failure
India Pale Ale
Now more easily available here in Slovenia than Isopropyl Alcohol... 😀 😀 😀
Peter
Please note: I do not have any affiliation with Prusa Research. Any advices given are offered in good faith. It is your responsibility to ensure that by following my advice you do not suffer or cause injury, damage…
Re: Mk2 Bed Bearing Failure
Kevin
I don't think there is much load on these bearings at all, which is one of the reasons why I think printing them with PLA will work quite well.
Any load will only be applied during part removal, and if that is done with care and the correct tools, then that also should be negligible.
Peter
Please note: I do not have any affiliation with Prusa Research. Any advices given are offered in good faith. It is your responsibility to ensure that by following my advice you do not suffer or cause injury, damage…
Re: Mk2 Bed Bearing Failure
Totally agree that any significant loading comes from removing the part and i think thats exactly what happened to me. I'm finding that sometimes the parts stick so well that even with a cool bed they are difficult to remove, even after fiddling with the z-height calibration to get the lines "nice and squishy" to quote our fearless leader 😀
IMO, the small one-time upgrade would be worth it to reduce my worry of causing bed damage when removing prints.
Re: Mk2 Bed Bearing Failure
Kevin
In that case, you may want to invest also in smooth rods with a much larger diameter...
I use a 1" wood chisel with a nice sharp edge to release the parts. As long as it is used flat on the cold bed surface, the parts do come away very easily - with the exception of TPU.
Peter
Please note: I do not have any affiliation with Prusa Research. Any advices given are offered in good faith. It is your responsibility to ensure that by following my advice you do not suffer or cause injury, damage…
Re: Mk2 Bed Bearing Failure
I think you're not supposed to lubricate these bearings as the recirculating balls are supposed to roll across the rods. I strongly recommend against it.
If anything, lubrication may cause problems because it might hinder the rolling/rotation, even if it's just slightly. So if they're not rolling, they're dragging (or floating is the 3rd option). This is similar to inertial problems when you try to change the direction of the bearing too quickly, and the inertia of the balls prevents them from rolling immediately, hence scraping and damage after repeated fast moves. You'd think that the inertia for a small recirculating ball is really small, but it has real consequences when trying to move quickly.
I think PJR is right -- clean them with IPA to make sure there's no crap in them and just run them dry.
Attacking a printer with wood chisels on the other hand... sounds more like a prison tactic.
Two of my Y-axis bearings were defective right from the factory, and since those are the easiest to access, I swapped all of those out with Igus RJ4JP-01-08's. So far so good, although Igus tolerances leave something to be desired. We'll see how long these last.
Re: Mk2 Bed Bearing Failure
although Igus tolerances leave something to be desired
Totally agree with that, although there is apparently some strange reason for the rather large variations in internal diameters which I don't really understand.
I do however now have those bearings on one of my printer's Y axis and they are behaving rather well.
A wood chisel is somewhat sharper than a regular scraper generally mentioned and does significantly less damage to both the part and the bed than the scraper simply because of its sharpness.
Peter
Please note: I do not have any affiliation with Prusa Research. Any advices given are offered in good faith. It is your responsibility to ensure that by following my advice you do not suffer or cause injury, damage…
Re: Mk2 Bed Bearing Failure
A proper sharpened wood chisel makes a great print remover. I can vouch for that and Peters suggestion.
One drop of real sewing machine oil, works for me. Also magnalube on the Z axis helical bearing on my Ultimaker 2+ as provided was needed this week from the noise from the rod/bearing. Now silent. A low dust environment is essential with 3D printers. I have such an environment. Low volume room, controllable.
Rolling on the rods wears the balls and the plastic. Pistons have oil rings to reduce friction and maintain pressure. The same effect helps with a very thin oil on the axis rods. The balls still maintain contact and pressure ie meniscus. The balls rotate in a thin film of oil.
Nigel
Life is keeping interested and excited by knowledge and new things.
Re: Mk2 Bed Bearing Failure
I'm very surprised to hear you endorse running these dry. All bearings roll across a guide surface by nature of how they work (except for "journal" or "plain" bearings which are really bushings) and typically all bearings need lubrication.
Here's an article that discusses the need for proper lubrication, though they do recommend a machine oil for light load applications (which is what we have with the Prusa). Grease may be overkill, but an oil lubricant seems like a no-brained to me.
http://www.thomsonlinear.com/downloads/articles/Linear_Bearing_Maintenance_taen.pdf
Also, i mentioned a drop-in replacement for the stock bearings a few posts back - they're made by SKF and will give you MUCH more dynamic load rating without needing to change your rails at all, might give those a shot over the Igus. They do this by having additional circulating ball paths (6 vs 3 on the LM8s) that more evenly distribute load, allowing it to tolerate more.
Re: Mk2 Bed Bearing Failure
Primum non nocere.
Pistons don't roll like ball bearings.
That article was pretty much... marketing literature. They're talking about bearings going 100km intervals.
The bearings in a 3d printer are under a much lighter load, and probably much shorter overall travel distances.
That means that they may be more dominated by acceleration/deceleration effects from very short, brief changes in directions than by long straight-running effects.
Just because some manufacturer says, "Put oil in it" (or in this case, I don't see any case where Josef has said to lubricate the bearings -- it's all the rest of you who are recommending it) doesn't explain *why* you should, or what the dominant effect of that oil is, or what the tradeoff is that you are implicitly making by adding it.
Sure, sometimes the oil is to reduce friction. Or sometimes it's there more for the purposes carrying heat away from a spot. Or sometimes the only reason it's there is to prevent corrosion or displace water. There is a "why", and I don't believe any of the explanations found here are sufficient (and they certainly won't be found in stock marketing literature).
If that oil winds up picking up contaminants that would have otherwise not remained in the system, that may in itself produce more damage than the extremely small amount of fiction it might have saved.
This may seem like a no brainer to you, but I'm going to go ahead and use my brain on this one...
Re: Mk2 Bed Bearing Failure
I believe that customer support has on one occasion (reported on this forum) suggested the use of vegetable (cooking) oil on the bearings, but that was an instance where there did appear to be some serious build issues.
Personally (and I can only report on my personal experience) I find that running dry significantly prolongs the life of bearings in my dusty environment, having experimented with copper and graphite grease, light machine oil and dry.
Yes when new, the dry bearings are slightly noisier than lubricated ones, but that changes very quickly when the lubricant gets contaminated.
And in any event, I am quite deaf, so the noise is irrelevant...
Peter
Please note: I do not have any affiliation with Prusa Research. Any advices given are offered in good faith. It is your responsibility to ensure that by following my advice you do not suffer or cause injury, damage…
Re: Mk2 Bed Bearing Failure
I uh... don't always listen to support.
Vegetable oil has been known to be problematic against certain types of rubbers. That and it can decompose and go bad.
Since we don't know what kind of rubber seal is employed on these bearings, I would say vegetable oil is a no-no.
Re: Mk2 Bed Bearing Failure
gz1
I only mentioned what was reported on the forum: http://shop.prusa3d.com/forum/original-prusa-i3-mk2-f23/customer-support-t1248.html#p9482
Don't blame the messenger 😉 You already know my opinion (which you agreed with...)
Peter
Please note: I do not have any affiliation with Prusa Research. Any advices given are offered in good faith. It is your responsibility to ensure that by following my advice you do not suffer or cause injury, damage…
Re: Mk2 Bed Bearing Failure
Real sewing machine oil is very light oil used to lubricate the moving parts of a sewing machine as recommended by Sewing machine manufacturers, they even supply some with the sewing machine. The linear bearings as supplied with the Prusa I3 Mk1 and Mk2 are oiled. Why? Because they need it. Enough said.
The ultimate result without oil wiil be the wearing of the plastic ball bearing seats and play, and wear on the rods and ball bearings. We are only talking of one drop of real sewing machine oil once every six months to maintain lubrication on the X and Y axis rods/bearings. I wipe down x and y axis rods regularly. Its called maintenance.
Nigel
Life is keeping interested and excited by knowledge and new things.
Re: Mk2 Bed Bearing Failure
What is the exact composition of sewing machine oil?
Re: Mk2 Bed Bearing Failure
Nigel
Bearings (and all precision metal goods likely to oxidise during a long sea journey from China) are coated in an "oil" that is designed to prevent oxidisation. That "oil" is not a lubricant and should always be removed prior to use. If you then wish to lubricate the part prior to use a light machine oil (such as sewing machine oil) is good for many purposes.
Peter
Please note: I do not have any affiliation with Prusa Research. Any advices given are offered in good faith. It is your responsibility to ensure that by following my advice you do not suffer or cause injury, damage…
Re: Mk2 Bed Bearing Failure
Hello!
I have seen maintenance personnel apply grease on ball rods(but they were used frequently and under heavy stress). Personally I prefer a small amount of grease applied to the rods every now and then. All surplus of grease are wiped off the rods directly after having moved the axis from end to end.
/Henrik