bryan.r
Posts: 49
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Re: Replacement bearings recommendation

Thu Apr 06, 2017 7:35 pm

I will definitely post again when I finish installing and let you know which bearing holder I went with and the difference in the noise/vibration symptoms.

steve.j
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Re: Replacement bearings recommendation

Tue Apr 11, 2017 9:36 am

Guys,

It's hard to source Misumi bearings for shipping to Australia so I am looking for alternatives.

Has anyone tried the VXB bearings?

On the basis of their price I would assume they represent higher quality, but would appreciate hearing form those who have purchased them.

bryan.r
Posts: 49
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Re: Replacement bearings recommendation

Wed Apr 19, 2017 12:02 pm

Well, it took a while to get back on here and post due to work, etc.. - but for anyone who still cares, I finished installing my Misumi bearings and rods. The machine is now definitely quieter than it was with the stock pieces, not silent by any means, but noticeably quieter.
Not being a mechanical engineering expert - just visual comparison of the stock and Misumi bearings seem to be very similar. The difference on the rods was very noticeable though - the surface of the Misumi rods compared to the stock was definitely far more polished/machined.
For the bearing attachment to the Y carriage I first printed and tried to use these, https://www.thingiverse.com/thing:1848700 , but as soon as I would begin screwing the M3 bolt in they would start to have a slight crack/separation running along the layers due to the orientation they must print. The holders print so that the layers run parallel to how the bolt runs. Maybe it was my print settings and/or the filament I used, but I did not feel confident in using these and did not want to be taking it apart again anytime soon. So I went with a much more secure method that I had to fabricate. I used metal pipe straps exactly like the ones in the picture. It was a bit of a pain because there was a lot of trial and error and detail work but it is worth it knowing those Y carriage bearings will not be wiggling around! Which by the way, the zip ties had definitely loosened up/stretched and were allowing the bearings to have movement. I would flatten out each of the metal straps and then cut them off approx where the red lines are and then drill new holes where the green is to line up with the holes in the carriage. I also had to polish/clean them up on the grinding wheel to get rid of any burs, sharp edges, etc.
In the second image(the crude drawing :-) ) I show what this looks like on the carriage with the black being the carriage and bolts, the green being the bearing and the red being the metal strap. This holds them VERY securely. It took a little back and forth tweaking to get the clearance exactly right with the bolt head and/or nuts so that it cleared everything properly but i think it was worth it. Sorry, I do not have a photo with me to post of the finished attachment piece but I'm sure you get the idea. I used M3-0.5 x 22mm bolts and had to do a little grinding on the end of the bolt to make sure everything had plenty of clearance.
Attachments
half_inch_pipe_strap.jpg
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drawing_1.jpg
drawing_1.jpg (5.89 KiB) Viewed 920 times

ales.f
Posts: 15
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Re: Replacement bearings recommendation

Sat Apr 29, 2017 2:18 am

Hello,

I am reporting on my Prusa i2 MK2S build using replacement Misumi rods and bearings. Everything went smoothly. The assembly took me several days, mostly because I was (overly) paranoid about right angles. I measured and remeasured everything after each step using Mitutoyo digital calipers or machinist 1-2-3 steel blocks. The printer has been printing since last weekend, and every print is amazing (I have printed only PLA so far). I expected the printer to kind of work, but did not expect this level of quality. The Misumi materials I used are as follows:

Rods (8 mm outer diameter, 52100 bearing steel, induction hardened, g6 tolerance)

SFJ8-320 (2x)
SFJ8-330 (2x)
SFJ8-370 (2x)

Bearings (8 mm inner diameter, no seal, G6 tolerance):

LMU-N8 (10x)

I have not used the stock bearings and rods at all, so cannot comment on how much quieter, if at all, my printer is. Apparently, the "S" version of the MK2 comes with better bearings and rods. However, in all fairness, I still get vibrations of the bed from time to time. I am reasonably sure that they are caused by the fact that the bed is supported by only three bearings that are close to each other and each of which is relatively short. I am planning to modify the entire printer by embedding it in the Rebelix frame and replacing the single Misumi bearings with their double variants, LMUW-N8 (there is a thread about it in the forum). The double bearing is 45 mm long. Exactly when I will do that remains to be seen. The printer is working fine, so I am hesitant to touch it.

Ales

cristian.s
Posts: 76
Joined: Tue May 31, 2016 7:06 pm
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Re: Replacement bearings recommendation

Wed Jun 07, 2017 8:18 am

Hi guys,

I finally got around to using my MK2S upgrade kit.
However, I used RJZM bearings(drylin the encased ones) for my Y and X axis(used mofified carriage).

I've had issues with the U-bolts: I think I either over or under- tightened them; they are not really made for this larger bearings so it was a tighter fit anyway. Also, since the bearings have a lower tolerance I think than the default ones, I realized my rods weren't that parallel - like 1mm or half a mm off, so I re-adjusted them and they slide better now.

I still get some vibration in my heatbed on fast movements... not sure if it can be avoided.

What I wonder is if it would be better to use the printed bearings holders for the Y-carriage instead of the u-bolts.
Has anyone else gone this path: U-bolts + igus bearings?

Thank you!

simon.r6
Posts: 1
Joined: Fri Apr 14, 2017 3:34 pm
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Re: Replacement bearings recommendation

Fri Jun 23, 2017 3:52 am

I just got my printer kit and wished I would have started with one of the 2 other bearing solutions. I used calipers to put everything together very precisely but I have a bad bearing. Few days of printing and I have a decent grove in one of the rods and a noticeable slip in my prints when the bed is in a certain position. Sounds like this is fairly rare, but at the same time for the cost of the kit and the cost of the bearings...why are they not shipping with a decent solution.
Anyway a $5 part is now going to take me a long time to fix. Takes away from the kid at Christmas feel of getting my first printer.
So if you don't have your printer yet mk2 buy some barings and trust your gut when you test feed them on the rails.

lee.f
Posts: 27
Joined: Mon May 22, 2017 12:44 pm
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Re: Replacement bearings recommendation

Thu Jul 06, 2017 7:30 am

Just fitted some RJ4JP-01-08 igus bearings to my mk2s and now circles come out oval. Any ideas why? Belts and pulleys seems tight.

ian.c9
Posts: 17
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Re: Replacement bearings recommendation

Thu Jul 06, 2017 3:03 pm

I've remixed the MK2S x-carriage so that the RJ4JP bushings fit better - this should avoid any slop and may help fix that:

https://www.thingiverse.com/thing:2421714

harryg
Posts: 9
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Re: Replacement bearings recommendation

Mon Jul 10, 2017 1:46 am

lee.f wrote:
Thu Jul 06, 2017 7:30 am
Just fitted some RJ4JP-01-08 igus bearings to my mk2s and now circles come out oval. Any ideas why? Belts and pulleys seems tight.
Igus bearings are less forgiving than the metal bearings, Y-axis rods must be perfectly parallel and the bearing cannot be over-tightened. But, if they are installed properly, they make the printer very quiet.

lee.f
Posts: 27
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Re: Replacement bearings recommendation

Tue Jul 11, 2017 11:42 pm

ian.c9 wrote:
Thu Jul 06, 2017 3:03 pm
I've remixed the MK2S x-carriage so that the RJ4JP bushings fit better - this should avoid any slop and may help fix that:

https://www.thingiverse.com/thing:2421714
Thanks, currently printing these https://www.thingiverse.com/thing:1846705 if I still get issues, i'll give yours a go :)

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