Replacement bearings recommendation  

Re: Replacement bearings recommendation

Kiss works well with the zip ties. I can vouch for that, Across the MK1 and MK2 builds. Bearings will wear, I would replace with the same. They are cheap and work well and in my experience last as long as you lubricate them every 6 months or so.:)

Re: Replacement bearings recommendation

I must have got lucky- I picked up both the RJZM-02-08 and the companion rods IGUS carries for them and cannot detect any slop at all. Perhaps thats the key. Dont do it half way.

I also have the rods from igus and there definitely is slop - but (also according to the rep) there must be some slop by design. So I am not sure what's up with your bearings and rods 🙂

Re: Replacement bearings recommendation

Kiss works well with the zip ties. I can vouch for that, Across the MK1 and MK2 builds. Bearings will wear, I would replace with the same. They are cheap and work well and in my experience last as long as you lubricate them every 6 months or so.:)

You mean the original bearing that come with it?
Sure they work, but I guess we are all hear to reduce the noise.

Re: Replacement bearings recommendation

I must have got lucky- I picked up both the RJZM-02-08 and the companion rods IGUS carries for them and cannot detect any slop at all. Perhaps thats the key. Dont do it half way.

With calipers, I can confirm that the ID of my bearings are 8.07, which is the 70 microns allowed by the specs. The specs do allow for manufacturing variations in the bearings, so it's possible that you received bearings with tighter tolerances due to manufacturing variations.

With your bearings, can you wiggle them at all when they're on rods? For comparison, my Misumi bearings do not wiggle at all when put on Misumi rods.

Re: Replacement bearings recommendation

From the specs, it seems that the all-Igus solution (RJZM-x-08 / AWMP-08) fit is about D9/h8, a free running clearance fit (there is slop). The all-Misumi solution is about K6/g6, an interference fit (there is no slop). This is confirmed by experience reports. I think that they should be both valid fits for their materials and applications, since they're manufactured from top notch companies. Probably the Misumi solution is better overall, if you don't consider the noise reduction of the Igus solution. Since there are no clear reports of quality difference, I would simply say to go Misumi if you don't mind the noise, and Igus otherwise. They are both decent upgrades to stock bearings - and neither will solve the problems of a cheap zip-tie based printer assembly.

http://www.misumi-europe.com/en/catalog/pdf/fa/2014/P1_0303-0304_F04_EN.pdf
http://theoreticalmachinist.com/IsoTolZoneCalc
http://www.amesweb.info/FitTolerance/FitTolerance.aspx

Re: Replacement bearings recommendation

I must have got lucky- I picked up both the RJZM-02-08 and the companion rods IGUS carries for them and cannot detect any slop at all. Perhaps thats the key. Dont do it half way.

With calipers, I can confirm that the ID of my bearings are 8.07, which is the 70 microns allowed by the specs. The specs do allow for manufacturing variations in the bearings, so it's possible that you received bearings with tighter tolerances due to manufacturing variations.

With your bearings, can you wiggle them at all when they're on rods? For comparison, my Misumi bearings do not wiggle at all when put on Misumi rods.

I can also confirm the ID of the batch I got is averaging 8.015 to 8.022+- 0.010, except for the last 2 of 8 that are closer to 8.036 and 8.042. There is a small amount in the last two thats noticeable. I'm not complaining since it was just the Y carriage I was working with.

Re: Replacement bearings recommendation

@torsten.c I get very little noise. I always print in quiet mode. No issues with prints. From day one. Just my kit build experience.

Re: Replacement bearings recommendation

EDIT2: I note that the RJ4JP-01-08 bearings might actually have a tighter tolerance than the RJZM-02-08 bearings according to the specs. The RJ4JP-01-08 bearings supposedly allow up to 40 microns of slop, while RJZM-02-08 bearings allow up to 70 microns of slop.

I received an RJ4JP-01-08 bearing today. With calipers, I can see that the ID for the RJ4JP-01-08 bearing is 8.04mm, while the ID for my RJZM-01-08 bearings is 8.07mm. Both measurements agree with the specifications laid out on the IGUS website.

When placed on rods, the RJ4JP-01-08 bearing wiggles significantly less than my RJZM-01-08 bearings (though there is a non-zero amount of wiggle).

So in my experience, the RJ4JP-01-08 bearing does have a tighter tolerance than the RJZM-01-08/RJZM-02-08 bearings.

Re: Replacement bearings recommendation

I finished assembling my printer today. I used the stock bearings, and luckily it is very quiet. I also have a Lulzbot Taz 5 and the Prusa is much quieter than it. I think I will hold off on any kind of bearing upgrades.

Re: Replacement bearings recommendation

I'm using RJ4JP on my kit (ordered the bushings before receiving the kit, so I did not used the default ones at all), so far it's working well, the noise is now coming from the fan and the steppers. Tolerances look quite good as well.

Re: Replacement bearings recommendation

I wanted to update my X,Y,Z-axis rods lengths to achieve quieter and smoother performance. My understanding is the rods and bearings are the thing to replace. So far after researching today i think I found a decent choice for replacement bearings and rods. Can the community confirm my BOM before I hit the purchase button.

https://us.misumi-ec.com/vona2/detail/110300026540/?ProductCode=LMU8
https://us.misumi-ec.com/vona2/detail/110302634310/?ProductCode=SFJ8-320
https://us.misumi-ec.com/vona2/detail/110302634310/?ProductCode=SFJ8-330
https://us.misumi-ec.com/vona2/detail/110302634310/?ProductCode=SFJ8-370

If my research is correct the appropriate lengths rods are:
Smallest smooth rod: 8mm x 320mm
Middle smooth rod: 8mm x 330mm
Longest smooth rod: 8mm x 370mm

Re: Replacement bearings recommendation

I did the PSFU8- rods and the LMU-N8 bearings. No regrets so far.

Re: Replacement bearings recommendation

I had the PSFU8- rods and the LMU-N8 in the cart, then I spoke with the engineers and he mentioned the PSFU is a h5 tolerance and "You need a g6 tolerance to use with Misumi linear ball bushings". I figure he knows what hes talking about. Hows the play, give, slop, etc on the PSFU8- rods and the LMU-N8? are the bearings and rod supposed to be tight or have a little glide to them?

Re: Replacement bearings recommendation

Also can you confirm the lengths? Thanks

Smallest smooth rod: 8mm x 320mm
Middle smooth rod: 8mm x 330mm
Longest smooth rod: 8mm x 370mm

Re: Replacement bearings recommendation

david.s30: did you order the Misumi rods indicated in your previous post? I am thinking of getting those rods along with the LMU-N8 bearings.

Re: Replacement bearings recommendation

After a long email conversation with an Engineer at Misumi, I ended up getting LMU8 G6 Linear Bearings and SFJ8 h6 Linear shafts.

I struggled because it seems everyone is getting the LMU-N8 and PSFU8 rods as mentioned by other people an they are working. I'm no expert but after talking to the Engineer he said the LMU-N8 Linear Bearings are an G6 tolerance and the PSFU8 rods are an h5 tolerance according to iso standings. He said they would work but "Our linear bushings can work with an h5 shaft. However, there will be some that are too tight to the nominal value, so that the bushing will not slide on the shaft properly."
LMU-8 is with a seal and LMU-N8 is without the seal. I'm not sure how the seal will affect the linear motion, but my environment could be prone to dust so I wanted the Linear bearing sealed. I figured I would trust the engineer and give it a try, if the linear motion isn't as smooth and quiet as the original Linear bearing and rod, I can just use the LMU-8 Linear Bearing and order a PSFU8 rod and bite the cost of the rods. I also never got any firm confirmation from any source on the correct Linear Shafts sizes, so Im praying my research is correct sizes. I'm supposed to get my Prusa on 2/21 and will probably build it on 2/25, so ill let the forum know how it goes.

So my complete order was
12 x LMU-8 Linear bearings
2 x SFJ8-320 Linear Shaft
2 x SFJ8-370 Linear Shaft
2 x SFJ8-330 Linear Shaft
About $140 US.

For reference Lowercase letters are for shafts (h5) while uppercase for holes (G6).

Re: Replacement bearings recommendation

Just to confirm your statements:
http://uk.misumi-ec.com/pdf/fa/2014/P1_0303-0304_F04_EN.pdf

LMU8 / SFJ8 is indeed the most effective solution (although not the most "silent" or "cheap").

Re: Replacement bearings recommendation

Excellent. Please let us know how it went, especially the lengths of the rods. My Prusa will probably come sometime in April, so I have enough time to do research and order the parts.

Re: Replacement bearings recommendation

Has anyone tried Matthew's O-ring suggestion (pg7) on Drylin bearings? I like the O-ring idea because they insulate the bearing from the plate.

Ken

Re: Replacement bearings recommendation

Hi david.s30

Have you built your printer yet? Did the Misumi rods work?

Thank you,
Ales