Comparison of original bearings, Misumi LMU8 and Vesconite polymer bushings  

RE: Comparison of original bearings, Misumi LMU8 and Vesconite polymer bushings

I'd expect there is no published spec. It's very hard to machine plastics, so a 0.05mm (7.99-8.04) range that Flaviu measured is actually quite good. Even the hardened rods aren't just turned, they're ground and polished to achieve the required dimensions, and that's metal, where achieving precision is easier, because it isn't as soft as plastic is.

I think I'll be happy to stay with the Misumi's.

RE: Comparison of original bearings, Misumi LMU8 and Vesconite polymer bushings

FWIW I'm perfectly happy with the print quality I get from the vesconites with my major remaining finish flaws being X/Y nonlinearity, fixed by gearing or 0.9 degree motors. If I had misumi bearings I'd probably use those too, but the bushings are a good contender to improve print quality/rod longevity at a fraction of the cost.

RE: Comparison of original bearings, Misumi LMU8 and Vesconite polymer bushings

A while back when I purchased Misumi bearings there was documentation that listed Superlube as a suitable grease.  I tossed the paperwork with the other packaging.  

Just got off the phone with Misumi tech support, the engineer I was speaking with said even motor oil is good for such a light load; he did not specify weight.  He also said Grade #2 Lithium Grease (suggested a tube from Home Depot), and when asked about synthetic grease he said it was also okay.. I asked about Teflon filled synthetic, he said no problem.  Then he repeated even motor oil is okay. 

Now all I need to do is find a Mobil 1 Rules sticker for my printer.

RE: Comparison of original bearings, Misumi LMU8 and Vesconite polymer bushings

Hello everyone !

I read the complete discussion. It seems that im not the only one wanting to upgrade the linear bearings.

I looked a lot of information in the web before I found this, and I was between the Vesconite and the Misumi. I thought were the best quality for each kind.

My "problem" start because I have the printer (i3 MK3 updated to MK3S) in the same room that I work with my RC Airplanes and other toys. (lucky me I can have this room :). But the issue is that there is always a lot of dust from air, or some Dremel job, or sanding process, etc... So the bearing starts sound like "crunch" ( not too loud, but I can eared them).

The first time, I bought some bearing locally, but they were chinese bad quality. So I bought the Prusa "originals". They look the same as the chinese, I mixed them by mistake and now I cant know what is what, but I think it doesnt matter because they both are crap.

At the beginning of this history I didnt know anything about linear bearings, so I contacted Prusa chat to know how was the best way to lubricate the bearings, and they told be they were autolubricated bearings (maybe the lady was joking). But if I wanted to add something should be lithium grease. So I bought a Lucas Oil White Lithium Grease #2. It seemed to me that was quite thick, but I used it anyway. Now I read that was necessary to clean the bearing before adding the grease (I also found a video in Youtube of a guy who put the new chinese bearings in an ultrasound cleaner and he found they were very dirty...).

So after read you all I will start by measuring the rods very carefully. I hope they are good, but if they arent, what is the exact part number that you bought from Misumi?? (this question is for vojtech-p6 🙂

I read that the Vesconite where less dust affected, but now I undertand that they are not precise as the Misumi. But, do you have any idea about this issue?? other than change the printer to another room that I dont have... 🙁

My conclusion is that if you want less noise and better prints, you have to invest the money in good quality lineal bearings, and good filament, and good quality nozzle. The chain always breaks in the weakest link, so you need to improve this parts. But if you dont want to expend more money, there is no problem, the Prusa does very good prints as it is. 

Best Regards !!

(sorry about my english...)

RE: Comparison of original bearings, Misumi LMU8 and Vesconite polymer bushings

Misumi ships with an oil preservative; and generally this is what most bearing manufactures do.  The bearings Prusa ships are no different.  The oil on the Prusa bearings is rust prevention, period (if Prusa wants to go on written record and say the oil on their bearings is real lubricant, please do so and list the actual OEM part number so we can verify independently).   Lucas #2 was exactly what the Misumi engineer mentioned (he didn't use the name, just the grade 2 tube of white lithium grease available at Home Depot website for $5 (which is Lucas #2 Lithium). 

RE: Comparison of original bearings, Misumi LMU8 and Vesconite polymer bushings

Posted by: cristobal

 But the issue is that there is always a lot of dust from air, or some Dremel job,

You should build an enclosing in my opinion. 🙂 

RE: Comparison of original bearings, Misumi LMU8 and Vesconite polymer bushings

Posted by: cristobal

Hello everyone !

But the issue is that there is always a lot of dust from air, or some Dremel job, or sanding process, etc... So the bearing starts sound like "crunch" ( not too loud, but I can eared them).

Good bearings do have working seals at the ends that protect them from dust. This is not always the case with the chinese clone LM8UUs. Still, check your rods for pits and scratches, it may not be just dust inside.

The first time, I bought some bearing locally, but they were chinese bad quality. So I bought the Prusa "originals". They look the same as the chinese, I mixed them by mistake and now I cant know what is what, but I think it doesnt matter because they both are crap.'

My experience is that the bearings Prusa ships are also a chinese LM8UU clone, but certainly above average of the crap that you can get on Aliexpress or eBay. You can typically recognize them by the lettering on the plastic seals, it seems to slightly differ between chinese clone manufacturers.

At the beginning of this history I didnt know anything about linear bearings, so I contacted Prusa chat to know how was the best way to lubricate the bearings, and they told be they were autolubricated bearings (maybe the lady was joking). But if I wanted to add something should be lithium grease. So I bought a Lucas Oil White Lithium Grease #2. It seemed to me that was quite thick, but I used it anyway.

NLGI 2 is thick, but will work if applied carefully. That is: Do not pack the bearings full of the stuff, just make sure the balls and the seals are nicely covered. Also rub it all over the rods in a thin layer. Packing the bearings full with a NLGI 2 grease will prevent the balls from rolling.

Now I read that was necessary to clean the bearing before adding the grease (I also found a video in Youtube of a guy who put the new chinese bearings in an ultrasound cleaner and he found they were very dirty...).

Cleaning is always good. Particularly when switching lubricants or when the bearings have been in use for a while. I use two baths: first is kerosene/paraffin/lamp oil, the second is isopropylalcohol. The first removes oils, the second removes the lithium soap and other residues. I think It'd be possible to use WD-40 as a substitute for the first bath.

Still, at least the Misumi preservation oil is compatible with lithium greases, so if you buy new Misumi's, no cleaning is required prior to installation. 

So after read you all I will start by measuring the rods very carefully. I hope they are good, but if they arent, what is the exact part number that you bought from Misumi?? (this question is for vojtech-p6 🙂

The Misumi part numbers are PSFJ8-370, PSFJ8-330 and PSFJ8-320. I simply bought a whole set for Mk3 from Zaribo.

My conclusion is that if you want less noise and better prints, you have to invest the money in good quality lineal bearings, and good filament, and good quality nozzle. The chain always breaks in the weakest link, so you need to improve this parts. But if you dont want to expend more money, there is no problem, the Prusa does very good prints as it is. 

Agreed. The Mk3/Mk3S is a great printer out of the box, possibly the best you can get for the money you paid. But if you're willing  to pay more, there are nearly endless possibilities that will bring you improvements. Some little, some bigger.

RE: Comparison of original bearings, Misumi LMU8 and Vesconite polymer bushings

Thanks for the info and replys !

I will keep you informed of my progress.

RE: Comparison of original bearings, Misumi LMU8 and Vesconite polymer bushings

My two cents: Working with a Stock MK3 with original bearings were quite of pain at my office and when I bought one to myself, I've also ordered Vesconite Superlube ones and, despite being expensive (almost €80 a pack of 10), they're very quiet and smooth. They seem a little fragile and "too plastic" but they can handle the workload. Now it's time to measure how much time they'll last.

RE: Comparison of original bearings, Misumi LMU8 and Vesconite polymer bushings

Dear everyone,

I have been for many years racing in the world of  onroad radio control cars where the use of bearings, and especially high speed bearings, are the order of the day. I am seeing that many people add grease to the bearings and this is a serious mistake. Why? I summarize it in these two points:

•  The movement becomes too slow until the grease starts to disappear.
• Dirt grabs more firmly on the bearings and they are more likely to stick/grip.

There are special low friction oils on the market that are specially designed for bearings. An example can be this oil (Please excuse me if you can't put links). Any of the oils from the brands used in the radio control are fully valid.

Please forgive me for my English if I make a spelling mistake.

Best regards.

RE: Comparison of original bearings, Misumi LMU8 and Vesconite polymer bushings

I forgot to mention that I recommend you to buy ABEC (Annular Bearing Engineers Committee) bearings because they must comply with a series of basic standards (Tolerances, noises, dimensions, etc...).

From my point of view, the bearing manufacturer par excellence, besides being expensive, is SKF. However, any bearing brand that follows ABEC standards should not be bad.

On the other hand, if you want bearings that are much smoother in motion and less prone to wear, you can try the hybrid bearings that have internal ceramic balls. They are also about 4 or 5 times more expensive.

Regards

RE: Comparison of original bearings, Misumi LMU8 and Vesconite polymer bushings

Posted by: paffendorf

Dear everyone,

I have been for many years racing in the world of  onroad radio control cars where the use of bearings, and especially high speed bearings, are the order of the day. I am seeing that many people add grease to the bearings and this is a serious mistake. Why? I summarize it in these two points:

•  The movement becomes too slow until the grease starts to disappear.
• Dirt grabs more firmly on the bearings and they are more likely to stick/grip.

There are special low friction oils on the market that are specially designed for bearings. An example can be this oil (Please excuse me if you can't put links). Any of the oils from the brands used in the radio control are fully valid.

Please forgive me for my English if I make a spelling mistake.

Best regards.

 

I'll accept you have experience with bearings for model cars.   But when you say dirt collects, well, that is what grease seals are for. It wipes the dirt away long before the bearings inside the housing see it.  The second is that in RC, the bearings are spinning at very high speeds. The bearings on a printer are 1) under much higher loads; and 2) not spinning nearly as fast.

So you are comparing different use cases.   

The engineers that design linear bearings know what does and does not improve the life expectancy.  Their business depends on it.  They say linear bearings should use Grade 2 grease.  While they do have bearings designed for oil, those bearings need to be in an oil bath, and have holes to allow the oil to circulate freely. 

Oil is especially bad on a linear bushing because it flows down under gravity and will pool in the bottom in the bearing case, leaving the upper rows carrying the load unlubricated. 

I'll keep the grease, thank you.

RE: Comparison of original bearings, Misumi LMU8 and Vesconite polymer bushings

I disagree with what you're saying. The first thing in a radio-controlled car is that you have many more loads on the X-axis and Y-axis for example on the bearings of a wheel. Don't compare a printer that maintains a bed of 400gr with a car of kilo and a half with speeds of 90km/h. Apart from the speeds and forces to which the bearings are subjected in the corners.

Anyway, according to what you're saying, the oil in the linear bearings would stay in the lower part of the bearing. Your theory can be applied to any bearing in any position, whether it is vertical or horizontal, be it an axial or linear bearing, the force of gravity tends to carry the oil downwards.

It makes me laugh when you talk about sealed bearings. If they really were sealed bearings, you couldn't grease them, because they would be totally sealed bearings. However, I can tell you that no bearing is completely sealed and even the specks of dust and any particulate found in the environment for a bearing is dirt. What you're talking about is a simple cover that you can lift with any blade.

You are effectively free to use grease that will certainly make you have more dirt on the bars that the bearings move through, I am only giving you advice of 10 years of use of "sealed" bearings.

RE: Comparison of original bearings, Misumi LMU8 and Vesconite polymer bushings

Posted by: paffendorf

I disagree with what you're saying. The first thing in a radio-controlled car is that you have many more loads on the X-axis and Y-axis for example on the bearings of a wheel. Don't compare a printer that maintains a bed of 400gr with a car of kilo and a half with speeds of 90km/h. Apart from the speeds and forces to which the bearings are subjected in the corners.

Anyway, according to what you're saying, the oil in the linear bearings would stay in the lower part of the bearing. Your theory can be applied to any bearing in any position, whether it is vertical or horizontal, be it an axial or linear bearing, the force of gravity tends to carry the oil downwards.

It makes me laugh when you talk about sealed bearings. If they really were sealed bearings, you couldn't grease them, because they would be totally sealed bearings. However, I can tell you that no bearing is completely sealed and even the specks of dust and any particulate found in the environment for a bearing is dirt. What you're talking about is a simple cover that you can lift with any blade.

You are effectively free to use grease that will certainly make you have more dirt on the bars that the bearings move through, I am only giving you advice of 10 years of use of "sealed" bearings.

When a bearing is a simple ball bearing, oil can pool at the bottom of the race, is collected by a passing ball and then is held in place by surface tension as it rolls around to the top of the race. A linear bearing has four rows of recirculating balls, only one of which will even be close to the bottom of the rod and may or may not have a pool of oil.  Apples & oranges. 

This is simple but basic fact about the linear bearing mechanics.  If one also considers your statement that seals on sealed bearings don't work.... well, cars on the road that use them to keep oil and greases inside the engine, transmission, axles, and dirt and water out, must all be untrue. 

Tell us how many RPM the motors on an RC car are spinning?  What about wheel speed in RPM?  How many meters per second are the bearings traveling?  If we assume a typical $100 RC model at 30 MPH (48 kPH) for a cheap 1/12 scale truck, and smallish 1/2" bearing, the RC bearing has a surface speed of about 2200 mm/s. Over ten times the speed of the printer linear bearings 200 mm/s.    If we use 100kph, and a 1" bearing, the different multiply another four fold.  Again, radically different operating conditions.  

Bearing manufacturers like Misumi and SKF sell linear motion bushings packed with grease for a reason. While there are cases where oil baths are used, they are immersion baths, not a few drops of oil added before use.

That said, some users are using no oil, some are using light oil, and some are using grease.  It's a personal choice.  I know light oil didn't protect my first set of bearings. Packing with grease extended the second set of bearings many times over light oil.  I can also say that in reading these forums people not using grease experience short bearing life similar to my own experience.  And by design, grease is better than oil for linear bearings because it sticks and remains where it is needed, as opposed to oil which migrates to places it isn't needed, and has no way to get back to where it is.

RE: Comparison of original bearings, Misumi LMU8 and Vesconite polymer bushings

I'm so totally confused now about things.

If one is using the Misumi LMU8 bearings.

What rods exactly should you be using with them for the MK3S?
I see reference for PSFJ8 and PSFU8. 

If one hasn't built their MK3S printer yet what should be ordered?  I know the rods would be:

RE: Comparison of original bearings, Misumi LMU8 and Vesconite polymer bushings

When you buy a kit, you get everything you need. Just clean and lube the OEM bearings BEFORE you install them onto the OEM rods and you'll be years ahead of most everyone else building the kits. I'm using Misumi bearings on OEM rods right now ... works fine ... but I had to swap bearings early on because I followed Prusa's lame guidance and didn't lube the original bearings properly.

ps: Misumi bearings were cheaper than paying Prusa to ship their OEM bearings ... some day I'll replace the rods, but there is no need right now.

RE: Comparison of original bearings, Misumi LMU8 and Vesconite polymer bushings

I used to just use light oil but did not lubricate enough during some long prints, it really needs a dripper arrangement or impregnated wiper on the rod. The result was eventual wear.

I now use a semi fluid grease which stays where it is put when a thin coat is put on the rods, bigger clumps would tend to migrate down to the bottom, but still leave a good coating on the rods, so I apply some drops of grease to the rods and slide the bearings over this which gets fresh grease into the bearings.

If the seals were oil tight, no grease would be left on the rods when they are first fitted when they have grease put into the bearing insides, to be honest the first week, I was wiping excess grease away from the ends of travel, so now we have established the seals are not double lipped seals, but merely dust seals, it means grease can move both ways, in and out, so greasing the rods periodically will allow the ball bearings inside to pick up grease and get re-lubricated.

The semi fluid grease I use is a bit smelly like in old car smells it can also be used as a steering box lube.

Whatever you use, make sure you do lubricate the bearings, not too much and not too thick a grease and you regularly grease the bearings.

The grease Prusa recommend is a pretty good specification but seems to be hard to source outside the Czech Republic.

RE: Comparison of original bearings, Misumi LMU8 and Vesconite polymer bushings

@chocki

What happens is the rods are parallel, but the extruder case bearing spacing doesn't match the rod spacing of the supports. So the rods flex as the extruder moves, the seals are compressed and leak grease. 

Just a 'cheap' design flaw Prusa made. The lower bearing in the extruder housing needs to float to match the actual rod spacing.

I've designed a new case I'll be printing later today to hopefully fix this issue. I am doing some major refurbishment of my printer: new rods, bearings, and high temp parts for the hot end. And new X-Carriage parts that allow the lower bearing to float (at least that's the plan). Woot!!!

ps: I've done some looking at my friction the past day or two, and yep - it really is time to use the new bearings and rods. My X-Axis is really worn out now.

RE: Comparison of original bearings, Misumi LMU8 and Vesconite polymer bushings

@Tim, keep me posted, I'm interested! 🙂

My parts are all skelestruder including X axis rod guides

RE: Comparison of original bearings, Misumi LMU8 and Vesconite polymer bushings

Any new guidance here years later?