Packing and Tearing Apart Linear Bearings for Anything (Prusa i3 Mk3)
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- Опубликовано: 21 окт 2020
- Curious what's inside a LM8UU bearing assembly? Ever wonder how to pack grease in those (or weren't aware you should)?
With the Prusa i3 Mk3 MMU2 unit removed I've decided to install the Mk3S modifications and install new properly grease packed bearings. I'm also taking off the IGUS RJ4JP-01-08 linear bushings that have been holding on the Z axis to see if they've worn.
Going through the process I noticed that the Z axis rods tolerances are a bit off. From what should be 8mm to around 7.85mm~7.95mm. Which does explain the noise from the rattly un-greased bearings that prompted the IGUS replacements in the first place. 
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I found this video to be quite 'handy'. Thanks!
I like this style of video.
Thanks!
Thank you! I enjoy doing the components and parts videos, I'll make sure to keep some in the mix.
For the IGUS, i saw a video, from a guy who use them in other systems, and he found out, they are great, but only after the 1st ones were in for a while, and THEN you put in the 2nd IGUS ones. He said, the plastic from the IGUS has to go around the rods first and fill all the microgaps which are in the rods and make the rods smoother, then the IGUS keep way longer and are way better. I havent tried it out, because since i have now the squashballs on my prusa i am really happy how silent they are, but before they were REALLY loud, and i talk about the Mitsumi bearings :-)
I haven't noted Igus mentioning anything along those lines. I'd imagine they would like to sell an extra set of bushings or two and wouldn't hesitate to note that being the case for iffy rods. Unless I missed it.
I guess if someone showed a test that had plastic embedded in a hardened metal rod I'd buy it. Not sure what scale that'd be at, interesting though.
There is definitely some truth to this. The Igus do leave a bit of material on the rods, even with their own anodized aluminum they recommend to pair with igus. They even state this in their official presentations. The question is whether you need a second pair, or only if they wore to the point the tolerances are not acceptable anymore.
I noticed that for the Y the tolerances don't matter much; gravity is in your favor and everything can kind of self align given the right interdistance between the rods. Yes it might drop a few microns after months of operation, but you can fix that with Z-offset. For X it's a different matter though, there you have gravity acting a moment force on the extruder+bearings, and so you're gonna run into binding quicker regardless as it hangs into the two rods.
WTF.... i was just thinking how this guys style reminded me of "This old Tony" and BAM!!! Starts talking about Tony. lol.
Thanks! Think I had been watching him work on the minilalathe at the time.
I'm replacing the bearings on my Y axis because they're having some tolerance problems, but the only thing that I'm really having trouble with on the X and Z axes is noise. Would I need to remove the bearings from the X and Z carriages, or can I just pack them while they're still in the carriages?
As long as you didn't need to clean them as well (and it was possible with the design) you could unseat the end of the rod they're riding on and pack them there.
If you do that remember to line up the balls correctly on the rod when you're putting them back on (edit: when you're securing them). The alignment of the races matters with the LM8 bearings.
Here's a handy post on reprap with an illustration: reprap.org/forum/read.php?1,310880
I like the video, I have some bearings on my Ender 5 Pro, LMK10LUU bearings very similar to those. Wanted to know if you could make a video on rebuilding one of those bearing you took apart? I'm curious as well on the sizes on those small ball bearings as well since there cheap amazon ones, I'm wondering what would the proper sizes to get.
Absolutely. I still have the one I disassembled in a drawer.
We can't do anything like a proper precision test if I do manage to get it back together. But we can see if it's functional!
Is the rod you are using to pack the grease the one that came with the mk3? I’m receiving my kit tomorrow and it sounds like it’s best soak them in ipa then repack them with superlube. I’ve never messed with bearings before.
The rod I used was from an Epson dot matrix printer. I would've used the rods from the i3 if it wasn't already assembled.
Is there a way to actually remove the seal with out breaking it? I packed mine with the wrong grease and now I need a way to dissolve it or remove the seal. they have been bathing in 99.9 IPA but I did pack them really full of grease
Removing the seal on the metal and rubber seal bearings almost always destroys it. It'll certainly destroy the seal. Best bet is to find a solvent that'll only effect the grease if you're not taking it apart for academic reasons. Or agitate the Alcohol in a safe manner.
Hey thanks for this video! Question for you: I'm using some Nyogel 767A damping gel on some linear bearings in a mod for a computer flight sim throttle (TWCS Throttle). Do you think a high-viscosity damping grease would be too much for the small gaps in a bushing like this? I'm hoping it won't be too much damping and am just trying to do as much research as I can before trying it myself.
As long as the grease is okay on the metal and seals I'd give it a quick try in the application to see of it provides the right amount of resistance.
I've used somewhat thick Molybdenum in LM8UUs before (in a different application) and that worked without any issues.
Two years late comment here - while I don’t think Nyogel 767A would…you know, corrode anything, it is so incredibly thick that I’d be surprised if it doesn’t negatively affect operation of the bearings.
It is thick to the point of being difficult to squeeze out of the tube haha. It is awesome for damping those throttles and sticks though, that’s for sure.
I use Superlube 21030 for these bearings/smooth rods. AFAIK, that is what Prusa recommends.
Ah, a good synth grease. I picked up a similar Mobile1 branded blend since the video for similar applications.
I usually like the tubs for using in the automotive work as well so I'll at least use some of it in a reasonable time-frame.
@@PCBurn I just did a little digging as far as these bushings/bearings go.
Following a link on Misumi's own page for the "LMU8 Linear Ball Bearing", they recommend this specifically: Alvania Grease S2 by Showa Shell Sekiyu. Lithium soap-based.
Can get a 180KG barrel of the stuff! haha. Now that's a lifetime supply.
[This is the brand Prusa currently uses...or at least have been using starting with the i3 MK3S+. I got name-brand Misumi with my MK3S+].
@@tiestofalljays ah, yea. Probably a fancy spec implementation of white lithium grease. They'd know!
Is it possible to make open bearing from this closed one ? If I just cut out one section where the small balls rolling ?
Not open through the sleeve, no.
@@PCBurn I will give a try
The ones I had come with my Prusa had roller type bearings in them, not ball bearings. Would it be worth replacing them do you think?
Like a V-slot roller bearing? I'm not sure I can envision that and don't recall a Prusa model with them.
@@PCBurn It's a mk3s, bunch of tiny cylinder bearings instead of ball bearings. Still look like the ones you have from the outside though
@@lio1234234 according to Prusa they use a Misumi LM8UU linear bearing. That'd be a standard recirculating linear bearing with balls.
Misumi rods and bearings are high quality. Can't imagine why you would replace new ones.
There is this stuff that comes in a gray tube called "superlube". It blows that Lucas stuff away.
That's a PTFE fortified grease. Might be a bit stiff for the application, or maybe it'd work well. I was avoiding the PTFE bearing lubricants (for the small recirculating balls) as I find them a bit waxy.
I found out, since i use squash balls under my Prusa Mk3S+, i only can hear the fan and a liiiittle bit the mechanic, but to type on the keyboard while my prusa is 30cm beside me working in normal mode, is louder than the printer. The squashballs with 2 yellow dots on it, are REALLY awesome to silent the printer. And before the printer was sooo loud that i thought i the bearings are not working and so on. But now they printer is really silent. You should try it out.
Eh, these were unlubricated as I made a bad assumption they were ready to go as shipped.
Unlubricated bearings are noisy. And wear! So I was remedying that.
Is that AVE lingo I hear?!
Thanks for the great video, you've earned a new subscriber!
Thanks!
And probably. A bit of the phrasing I've always used and more's likely slipped into my vocabulary.
I need to clean my bearings because they were packed with the wrong type of grease. Can you recommend a cleaner I can use that won't harm the rubber seals?
I usually agitate them in a high percentage alcohol. It'd depend on what the seals are; it works fine on mine.
@@PCBurn Well they were packed with Permatex White Lithium Grease which I think was the wrong stuff to use. I want to replace it with Superlube but I've put some of the grease in a cup with 91% alcohol and it been in there a while and still looks like its ok. YIKES.. think I can clean them with WD 40 then put them in a alcohol bath to get rid of the WD 40. I just don't want to harm the rubber seal.
Oh. they are the bearings from my Mk3s+
You'd have to put the bearings in and agitate them. I wouldn't use a solvent that dissolves silicone myself, like WD40, but the end seals are probably fairly resistant. Should be okay if you wash it off well with alcohol prior to lubricating.
Good 🦸♂️
When I saw the video clip I thought you packed an igus bearing into a metal bearing housing
There is an Igus bearing with a removable metal sleeve that's a drop-in replacement.
It did occur to me to put a metal sleeve on one of the less expensive Igus parts... I haven't yet!
13:38 there is a BEAR Mod which is redesigned already for this part
If you mean the ones by Pekcitron they require a frame alteration.
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