Linear Rail bearings fell out - now not smooth
I never tested the linear rail prior to install - meaning i never slid the carraige from left to right to see how smooth it was. during assembly i installed it backwards which allowed the carraige to fall off of the rail and a bunch of the ball bearings fell out. i cleaned them, lubricated them, and added them back in. Now i feel that carraige vibrates a bit and isn't as smooth as i imagined it would be.
is this normal? i'm still assembling and now i'm considering buying this part again just in case but first i want to ask here if that is normal. how smooth is that carraige supposed to be? if its supposed to be smooth as glass when sliding across the rail should i buy a new one or try to reassemble the carraige again?
Best Answer by miroslav.h4:
The carriage must never fall off the rail!! If you look at a store with these rails, look carefully at the separate carriage when it is off the rail. It is always mounted on a piece of plastic in the shape of a rail, it is never loose! And it is mounted in such a way that the plastic slides onto the rail as if it were one piece with it and the carriage moves onto the rail from that piece of plastic. If you manage to drop the carriage off the rail and some balls fall out, you basically have no way of putting the balls back in properly and the whole assembly will be useless because it will no longer work as it should. The only option is to buy this assembly new as a spare part. The question remains whether Prusa offers it. If not, you will have to look at the sellers of these rails to see if they have it in the required length and width (which is the main information for ordering). Perhaps a foreign seller could sell you a separate carriage that you can carefully mount on the original rail.
RE: Linear Rail bearings fell out - now not smooth
The left-right rail is a THK bearing and they're usually not the same if the bearings come out. Some usually get lost and the count gets messed up between the two sides. That's why they use safety plugs and have warnings in the build document. I'm not saying it can't be put back together and work correctly, but the odds are not good. It should be very smooth and have zero play. It also needs to be lubed only with the specified Kluber GL-261 grease, not Prusa grease or any other lube.
RE: Linear Rail bearings fell out - now not smooth
I would contact Prusa and they may send you a new bearing.
RE: Linear Rail bearings fell out - now not smooth
The carriage must never fall off the rail!! If you look at a store with these rails, look carefully at the separate carriage when it is off the rail. It is always mounted on a piece of plastic in the shape of a rail, it is never loose! And it is mounted in such a way that the plastic slides onto the rail as if it were one piece with it and the carriage moves onto the rail from that piece of plastic. If you manage to drop the carriage off the rail and some balls fall out, you basically have no way of putting the balls back in properly and the whole assembly will be useless because it will no longer work as it should. The only option is to buy this assembly new as a spare part. The question remains whether Prusa offers it. If not, you will have to look at the sellers of these rails to see if they have it in the required length and width (which is the main information for ordering). Perhaps a foreign seller could sell you a separate carriage that you can carefully mount on the original rail.
RE:
>> i cleaned them, lubricated them, and added them back in.
Not necessarily wrong because standard procedure in a Voron build (not sure whether the Prusa rail behaves the same). Maybe check the respective videos. On Voron it's even mandatory as theirs usually ship with storage wax (not lubricant) and need to be cleaned and greased. See Voron build vides.
If you did already re-assemble but it doesn't run smoothly, check for any lost balls. Generally, there are printed tools for securing the carriage when it slides off the rail (need correct size).
RE: Linear Rail bearings fell out - now not smooth
The replacement linear rail is here:
https://www.prusa3d.com/cs/produkt/linear-rail-corexy-2/
RE: Linear Rail bearings fell out - now not smooth
Not too cheap, but maybe the best answer. Human beings assembled those rails at the THK factory, so we know it's possible, but we don't know what secret sauce they used. For example, they might have used selected ball bearing sizes to get the right preload. Worst case, they might have used different selections on each side, and you'd need high resolution micrometers to tell them apart. I know the ball count matters. One too many or one two few might be an issue. There's certainly no law against trying to get it back together, but there could be unknowns working against you.
RE: Linear Rail bearings fell out - now not smooth
First of all, you need to know that in professional production at the company, special single-purpose fixtures and tools are used that you don't have at home. That's why it can be produced accurately and repeatedly in large quantities. I'll give you an example: when I was learning, I managed to "disassemble" a relatively complex switch and put it back together for almost a week, and during this work I wondered how the manufacturer does it. And coincidentally, after some time, I joined a company that produced these things. And of course, what I put together at home for several days, the same thing at the company was assembled by an employee in about 20 seconds!
RE:
First of all, you need to know that in professional production at the company, special single-purpose fixtures and tools are used that you don't have at home. That's why it can be produced accurately and repeatedly in large quantities. I'll give you an example: when I was learning, I managed to "disassemble" a relatively complex switch and put it back together for almost a week, and during this work I wondered how the manufacturer does it. And coincidentally, after some time, I joined a company that produced these things. And of course, what I put together at home for several days, the same thing at the company was assembled by an employee in about 20 seconds!
A great example of this is the Curta. It required very specialized tools and jigs to do any maintenance on it and it couldn't be done by a casual user. When I took mine apart out of curiosity, it was impossible for me to reassemble. Fortunately I found an enthusiast in Switzerland (of course) who had the original tools and assembly jigs and was able to put it back together for me.
RE: Linear Rail bearings fell out - now not smooth
I have seen rail carts sold by themselves. Search online for the correct size.
RE:
I never found any ball bearings laying around but I did note that the two sides weren't stacked evenly with ball bearings so some were lost when I popped that carriage block off of the rail.
I bought a new linear rail carriage and it slides WAY smoother than how my other one did. Im glad I got it.