Question(s) for all you Engineers here, about linear bearings
I am going to preface this with the comment that in all my years working machines, not one had linear bearings. So there is some mysticism surrounding them.
- Prusa says to mount the bearings so 1 row rides on top of the Y-axis rail. What are the Pros and Cons of doing this way versus mounting it rotated 45 degrees?
- I have seen some referred to as having recirculating balls. Do the ones shipped by Prusa have them? I cannot tell, even under magnification ( see opening comment ).
- Would it be a good idea to immerse them in IPA and use ultrasonic cleaner while they are in the IPA before greasing them? I see absolutely no indication that they came with even shipping oil/grease.
- I was at one bearing site and they listed both an EU and a Japan version of the LM bearings. check here! What?
Help! My brain is exploding. Has exploded?
Quality is the Journey, not the Destination. My limited prints->
RE: Question(s) for all you Engineers here, about linear bearings
1. Prusa recommendations are usually worth following. They run hundreds of their own printers making parts so they know first hand what works best on their machines.
2. I believe all of these linear bearing have recirculating balls.
3. Yes. Follow this article - https://prusacommunity.com/set-your-bearing-straight/
4. LM is the series used on the Prusa's which I believe are the japanese metric shown on that site.
Finally, I strongly recommend Misumi bearings and rods. They are not cheap but are good quality.
RE: Question(s) for all you Engineers here, about linear bearings
I also prefer Misumi Linear bearings and working with them since 2 years on my MK3. I never used the Prusa bearings and rods.
An alternative would be the SKF bearings. To do this, you have to change the bearing bushes on the printer (no U-hook)
https://www.zitec-shop.com/de/lbbr/p-G1635000070
Statt zu klagen, dass wir nicht alles haben, was wir wollen, sollten wir lieber dankbar sein, dass wir nicht alles bekommen, was wir verdienen.
RE: Question(s) for all you Engineers here, about linear bearings
The PRUSA supplied bearings work adequately for most users (Hobby users) and will last quite a long time if assembled correctly and looked after which means cleaning and lubrication.
If your planning to run your printer day and night most of the time, then maybe you should consider upgrading the rods and bearings to misumi and continue a maintenance regime.
Here is a link to a post which discusses lubrication which may be of use to you.
Normal people believe that if it ain’t broke, don’t fix it. Engineers believe that if it ain’t broke, it doesn’t have enough features yet.
RE: Question(s) for all you Engineers here, about linear bearings
I would be very wary of using the SKF bearings shown, on a prusa printer since the metal strip you see is the back of the actual bearing surface and floats to allow some degree of self alignment and it will not be held all around the bearing when fitted to the prusa, these bearings are intended to be used in a bearing housing which has a bored hole which the bearing sits in, thus holding all 4 bearing strips in place.
Normal people believe that if it ain’t broke, don’t fix it. Engineers believe that if it ain’t broke, it doesn’t have enough features yet.
RE: Question(s) for all you Engineers here, about linear bearings
@chocki
Closed bearing bushes with the correct bore diameter are of course required. I made and installed such bearing bushes made of aluminum on my Y-axis (4 pieces). The Y-axis runs absolutely smoothly and precisely, even at heated bed temperatures around 130-140 degrees C. These bearings are rather unsuitable for the X-axis and not neseccary for the Z-axis.
Statt zu klagen, dass wir nicht alles haben, was wir wollen, sollten wir lieber dankbar sein, dass wir nicht alles bekommen, was wir verdienen.
RE: Question(s) for all you Engineers here, about linear bearings
@olef
Thanks for the info and link. The link looks like the site has wasted away ( no updates f0r loonngg time ) but the info was interesting and I will keep it for when I schedule an upgrade.
Company recommendations are usually safe and if followed things do work. My suggestion to everyone is to follow them unless you know what you are getting into... and don't complain if it doesn't work 😀
Quality is the Journey, not the Destination. My limited prints->
RE: Question(s) for all you Engineers here, about linear bearings
@chocki
The link you provided filled in a lot of gaps that will help me make an informed decision. I thought grease was ...well grease. Learned something today. Thanks
Quality is the Journey, not the Destination. My limited prints->
RE: Question(s) for all you Engineers here, about linear bearings
@karl-herbert @chocki
Thanks for the input. I am not in position to machine my own housings. But there are alternatives. I am leaning to getting matched Misumi rods and bearings ( and grease ). I am looking at other bearing manufactures as well. The more info and experience I get, the less the Prusa RepRap solution (LM8UU ) looks like the one I would prefer. If I cannot find something I like and can implement, then upgraded rods/bearings. Whatever I choose, it will be the one that works for me and not "THE" one for all
Quality is the Journey, not the Destination. My limited prints->
RE: Question(s) for all you Engineers here, about linear bearings
1 – partially answered
I am still not clear if rotating the bearings is good idea or not. I am prepared to deviate from Prusa recommendation if I can perceive a benefit. I will venture into that end f the pool and see what happens. Just need to figure out how 'measure'.
2 – answered
3 – I conclude that ultrasonic cleaner with IPA should be OK. Just a lazy man's way ( my way ) to swirl bearings in IPA.
4 answered
To everyone that has replied, I appreciate you taking the time to reply and I will consider all of it as I move forward.
Quality is the Journey, not the Destination. My limited prints->
RE: Question(s) for all you Engineers here, about linear bearings
My only comment:
If you have two bearings on a rail, rotate one of them so the balls don't line up with the other.
Wear only occurs at the point of ball contact.
And if you do wear a groove - get new bearings and rotate them away from the groove.
RE: Question(s) for all you Engineers here, about linear bearings
@kennd
My only comment is on the ultrasonic cleaner with IPA. Dont. If you use IPA in an ultrasonic bath you will create a very flammable vapour. One spark and, well you can guess the rest.
RE: Question(s) for all you Engineers here, about linear bearings
My only comment is on the ultrasonic cleaner with IPA. Dont. If you use IPA in an ultrasonic bath you will create a very flammable vapour. One spark and, well you can guess the rest.
I do all my ultrasonic cleaning outdoors because I don 't always use soap and water ( and I can't afford to replace my house ). Your comments are great for reminding people that using products "off-label" is not recommended.
Quality is the Journey, not the Destination. My limited prints->
RE: Question(s) for all you Engineers here, about linear bearings
@kennd
Another option would be to use bronze-graphite slidebearings. They are maintenance-free and run very smoothly. No problems with ball orientation and no grooves on the rods.
Statt zu klagen, dass wir nicht alles haben, was wir wollen, sollten wir lieber dankbar sein, dass wir nicht alles bekommen, was wir verdienen.
RE: Question(s) for all you Engineers here, about linear bearings
@robert-rmm200
If you have two bearings on a rail, rotate one of them so the balls don't line up with the other.
👍
Quality is the Journey, not the Destination. My limited prints->
RE: Question(s) for all you Engineers here, about linear bearings
@kennd
Another option would be to use bronze-graphite slidebearings. They are maintenance-free and run very smoothly. No problems with ball orientation and no grooves on the rods.
Cool. I am open to suggestions for upgrade. I have seen non roller bearing solutions that lasted for a decade in high speed rotational and linear applications without integrated seals providing they are properly maintained. Maintained is key. If things are sealed, people tend to forget them.... until they fail. $$$$
Quality is the Journey, not the Destination. My limited prints->