Scratched rods from linear bearings  

Re: Scratched rods from linear bearings

My reading leads me to believe the UU type bearings need lithium grease... See A-549 in linked document.

https://www.thk.com/sites/default/files/documents/us_pdf/products/generalA/en_A_523_lbearing.pdf

Grease / oil type and NLGI grade are usually based on application, not bearing type. The rare exceptions are material types, but we are using steel here so it is not important. You can see that the document shows both are ok and used. For 3D printers, load is minimal and low friction is the priority. This means oil is best suited. This is why I mentioned grease will need less applications, but oil will be higher performance. This is across all mechanical applications.

From same page:

Oil Lubrication
Turbine oil, machine oil and spindle oil are com- monly used as a lubricant.
When oiling the Linear Bushing, drop oil on the LM shaft, or infuse it from the greasing hole on the housing as shown in Fig.1.

Re: Scratched rods from linear bearings

My reading leads me to believe the UU type bearings need lithium grease... See A-549 in linked document.

https://www.thk.com/sites/default/files/documents/us_pdf/products/generalA/en_A_523_lbearing.pdf

Grease / oil type and NLGI grade are usually based on application, not bearing type. You can see that the document shows both are ok and used. For 3D printers, load is minimal and low friction is the priority. This means oil is best suited. This is why I mentioned grease will need less applications, but oil will be higher performance. This is across all mechanical applications.

From same page:

Oil Lubrication
Turbine oil, machine oil and spindle oil are com- monly used as a lubricant.
When oiling the Linear Bushing, drop oil on the LM shaft, or infuse it from the greasing hole on the housing as shown in Fig.1.

I guess it depends on your interpretation...

Lubrication

The Linear Bushing requires grease or oil as a lubricant for its operation.

[Grease Lubrication]
When installing a type attached with seals on both sides (...UU) to the LM shaft, apply grease to rows of balls in the Linear Bushing.
When installing standard types (without seal), perform the same as above or apply grease to the LM shaft.
Afterward, replenish grease of the same type as necessary according to the service conditions.
We recommend using high-quality lithium-soap group grease No. 2.0

[Oil Lubrication]
Turbine oil, machine oil and spindle oil are com- monly used as a lubricant.
When oiling the Linear Bushing, drop oil on the LM shaft, or infuse it from the greasing hole on the housing as shown in Fig.1.

Re: Scratched rods from linear bearings

I guess it depends on your interpretation...

I have a fair bit of experience with machine lubrication, however to each their own.

this is the important bit

The Linear Bushing requires grease or oil as a lubricant for its operation.

The extra notation on sealed vs non sealed is only included because grease is applied differently to each type, but it does not mean that sealed bearing need grease over oil.

Re: Scratched rods from linear bearings

I guess it depends on your interpretation...

I have a fair bit of experience with machine lubrication, however to each their own.

this is the important bit

The Linear Bushing requires grease or oil as a lubricant for its operation.

The extra notation on sealed vs non sealed is only included because grease is applied differently, but it does not mean that sealed bearing need grease over oil.

I do a lot of heavy industrial stuff almost nothing this small. Our big stuff is all grease our smaller items, very very few, get Nyeoil II but they have bronze bushings... I'll hit the Motion Industries rep up next time he's in as I'm interpreting this as bearings sealed on both ends should be greased. I asked the wife to bring home a monoject syringe from her office so that I have a way of getting grease into such a small opening.

Are you saying the bearings should be oiled prior to putting them on the shaft or oiling the shaft directly as shown in the illustration? We apply the Nyeoil to the shaft. If applying to the shaft won't the seals keep the oil out of the bearing area?

Re: Scratched rods from linear bearings

I do a lot of heavy industrial stuff almost nothing this small. Our big stuff is all grease our smaller items, very very few, get Nyeoil II but they have bronze bushings... I'll hit the Motion Industries rep up next time he's in as I'm interpreting this as bearings sealed on both ends should be greased. I asked the wife to bring home a monoject syringe from her office so that I have a way of getting grease into such a small opening.

Are you saying the bearings should be oiled prior to putting them on the shaft or oiling the shaft directly as shown in the illustration? We apply the Nyeoil to the shaft. If applying to the shaft won't the seals keep the oil out of the bearing area?

Yes. Scale is the difference. Load is going to be big deciding factors in industrial equipment. However even semi-industrial mills and lathes use machine oil for tracks and so forth. This is why we have machine oil. Also when speaking to your rep, think desktop printer, sewing machine, etc. Sewing machine oil is actually a great lubricant for 3D printers. Internal gearing would warrant a grease, but oil is the way for a track (rod). The only reason for that case of grease is because many of these internal parts are not accessible and regular interval oil lubrication is difficult.

Now as for sealed bearings. This is deceiving. Traditionally, yes, a sealed bearing is used with grease. However, the seal of the bearing is really only there to keep contaminants out of the grease to reduce abrasion. Here is the thing, a sealed bearing isn't actually necessary for this application, (although we should never underestimate the amount of dust that gathers in our maker spaces :lol:) and given that the seals are just to keep out contaminants, these bearings can function just as non sealed would without a problem. That said, the principle still applies that oil and grease are dependent on application and not the parts.

If I had to compromise I could meet you halfway, but I would only suggest an NLGI #0 or NLGI #00. Not an over the counter #2. Similar to a mustard or ketchup consistency, but I wouldn’t even do that myself. Personally, I will use machine oil. You can even google “low torque, high speed lubricants.” We are not running very high speed, but this property of oil will help with rapid movement and direction change. Nerd reason, the shear force which creates the thinning action of grease to reach base oil lubricity requires energy. This energy produced by shear friction is not the biggest property of a ball bearing, however due to small size it makes a difference. By reducing the energy needed to overcome shear drag of grease, which is actually produced by the soap additive, we have less force and easier motion. The actual lubricating property of grease is created by the oil inside it and not the thickening soap.

As to application process. I will apply oil directly to ball bearings while building the kit and will rub down the rods. Once assembled, I will put a couple drops on the track and rub it with my fingers whenever dry. The faint of heart can apply it to a paper towel and simply rub the rod :geek: . An oily rag in a shop is the best actually. Just keep it away from flames.

EDIT: Just saw this, mate.

If applying to the shaft won't the seals keep the oil out of the bearing area?

No. unless those seals are incredible haha, they don't stand a chance against oil. They mainly keep dust and debris out. It will start by lubricating the contact edge of the seal, then it will get in and coat the bearings.

Re: Scratched rods from linear bearings

I've ordered Misumi rods and bushings while waiting for my MK3 to arrive.
Misumi advises in its technical documentation to clear the transport oil of the bushings and pack them with lithium grease.

So in your opinion I shouldn't pack them with lithium grease?
What about packing them with lithium grease and using oil for maintenance? (Since in my understanding it is a bit useless to apply grease on the rods since the seal would stop the grease to enter).

Re: Scratched rods from linear bearings

I've ordered Misumi rods and bushings while waiting for my MK3 to arrive.
Misumi advises in its technical documentation to clear the transport oil of the bushings and pack them with lithium grease.

So in your opinion I shouldn't pack them with lithium grease?
What about packing them with lithium grease and using oil for maintenance? (Since in my understanding it is a bit useless to apply grease on the rods since the seal would stop the grease to enter).

Haha, this always gets out of hand. It's funny because this is an age old debate. The short answer is the odds stack up on oils side far more when the machines get smaller. Grease is often a default answer with bearings though, because most bearings are neglected and buried behind car wheels, inside bicycles, in gearboxes and axels, and so forth, so you will run into that suggestion a lot. Lube nerds will suggest oil for this specific application though 😀

Here is the thing though. If you use lithium grease, you’re not going to hurt anything. It is a perfectly useful grease. I use it all the time actually. I was just going after optimal, because we all know how particular 3d printers are.

Unless you really know what you are doing though, dont mix oils with greases. Oils that are not compatible with greases can cause separation which causes the grease additives to clump and fail.

If you want to assemble your printer and don't want to touch it for an extended period of time (maintenance wise) use a grease. This is far better for long haul applications. If you want performance and cleanliness, and dont mind applying a couple drops of lube once a month or so (depending on your printing) use oil. Prusa also suggests using the good ole standby "3-in-1 machine oil” from what I’ve read. This is a great thin oil that will attract minimal dirt, prevent oxidation, and give great lubrication.

At the end of the day, the red pill… the blue pill… the choice is yours.

Re: Scratched rods from linear bearings

What @michael.a35 makes perfect sense to me and big thanks for the input michael.a35 by the way, I really appreciate your input. I'm 99% certain all of our machine shop equipment is lubricated via circulating oil, I'll pay closer attention when I walk through the machine shop today.

So in your opinion I shouldn't pack them with lithium grease?

What @michael.a35 about the shear forces of grease on such small parts is the best argument for oil as far as I'm concerned, or if grease is used it needs to be done so sparingly. Fortunately I have a bit of time to explore this as my printer isn't due to ship until next week so I'm still going to hit our rep up.

edit: @michael.a35 beat me to the answer, I started typing this at the start of the work day and got side tracked...

Re: Scratched rods from linear bearings

Whilst discussing don't lose sight of the fact that the balls need to roll not slide, the scratches I've seen images of couldn't be caused by a rolling ball ... indeed some of the pictures I saw looked like the cage had been rubbing the rod as in scuffed and scratched - doesn't detract from the fact that the rods are / were too soft. How many when in a hurry building are

a) Over tightening - especially the U bolts on the bed
b) Not paying attention to the ball race orientations
c) Not paying attention to tightening sequences on the rods etc - i.e. moving the bed etc whilst tightening

How many actually check the components work before committing to the build ?

Grease that is too viscous or simply too much grease will make them slide, there are plus and minus points for each. High grade linear bearings don't need much maintenance they have two seals - one to keep the lubrication in and one to keep dirt out, the lube is there for the balls and raceways NOT the rods, oiled bearings need a lot more maintenance, sewing machine oil is ideal, 3 in 1, if you're dead set on cleaning out the grease its hard to beat good old fashioned paraffin, the ultimate clean is in an ultrasonic tank with degreaser.

Re: Scratched rods from linear bearings

Whilst discussing don't lose sight of the fact that the balls need to roll not slide, the scratches I've seen images of couldn't be caused by a rolling ball ... indeed some of the pictures I saw looked like the cage had been rubbing the rod as in scuffed and scratched - doesn't detract from the fact that the rods are / were too soft. How many when in a hurry building are

a) Over tightening - especially the U bolts on the bed
b) Not paying attention to the ball race orientations
c) Not paying attention to tightening sequences on the rods etc - i.e. moving the bed etc whilst tightening

How many actually check the components work before committing to the build ?

Grease that is too viscous or simply too much grease will make them slide, there are plus and minus points for each. High grade linear bearings don't need much maintenance they have two seals - one to keep the lubrication in and one to keep dirt out, the lube is there for the balls and raceways NOT the rods, oiled bearings need a lot more maintenance, sewing machine oil is ideal, 3 in 1, if you're dead set on cleaning out the grease its hard to beat good old fashioned paraffin, the ultimate clean is in an ultrasonic tank with degreaser.

.
a) Over tightening - especially the U bolts on the bed
I'm having a hard time coming to terms with the U bolt design, surely there's a better way, ahem, pillow block, and would print a strap prior to my build if I had a printer...

Also, don't forget, not lubricating the bearings... I know Prusa says bearings are pre-lubricated but from what I see when purchasing new they only come with protective oil not pre-lubricated.

Re: Scratched rods from linear bearings

I've avoided going too nuts just yet (if you consider SKF bearings and rods not to be nuts) but the U bolt design isn't the best - in fact the whole bed mech.

I'm tempted to get dedicated alloy support blocks from somebody like SKF - those U bolts are easily capable of destroying the bearing. There also seems to be an assumption that the hole in which the bearings go on the X and Z axis are 'OK' - but these are printed parts and can be wildly inaccurate in engineering terms. If it takes too much force to insert the bearing this is an indication that something's not right - but how much force is too much will be the next question. Where two bearings are inserted back to back it is essential that the bearings are in line and perfectly aligned give or take a small allowance - and if the bearing can't handle that allowance then the hole needs sorting - basic engineering - the optimum would be to ream and sleeve them.

I do intend to redesign the bed assembly at some point and will probably put it on rails not rods with a ball screw not belt.

Before anyone says I'm attacking Jo I'm not, there are many issues that can be encountered that users may not realise are issues, they then have problems - not everyone is an engineer ....

Re: Scratched rods from linear bearings

One might also want to know what the manufacturer advises in the manual:

"Every couple hundred hours, the smooth rods should be cleaned with a paper towel. Then apply a little bit of general purpose machine oil on the smooth rods and move the axis back and forth a couple of times. This cleans the dirt and increases longevity.
If you feel the axis is not running smoothly anymore, bearings can be taken out and greased on the inside (they need to be removed from axis because the plastic lip will prevent the grease from getting inside). Super-lube, or any other multi purpose grease, will do."

So I will look at the bearings during rebuild and judge whether I see they are well greased. Later, I will use machine oil on the rods:-)

Re: Scratched rods from linear bearings

"Also, don't forget, not lubricating the bearings... I know Prusa says bearings are pre-lubricated but from what I see when purchasing new they only come with protective oil not pre-lubricated."

What's the difference between protective oil and oil?

Re: Scratched rods from linear bearings

"Also, don't forget, not lubricating the bearings... I know Prusa says bearings are pre-lubricated but from what I see when purchasing new they only come with protective oil not pre-lubricated."

What's the difference between protective oil and oil?

It’s used to protect from corrosion during shipping and storage not to lubricate

Re: Scratched rods from linear bearings

Can i use LIQUI MOLY LM 47 grease?
It says, that is good for Big Bearings... i dont know what to use now

Re: Scratched rods from linear bearings

Don't forget that these are recirculating ball type bearings and the tiny bearing balls need to roll freely to circulate in the tracks. Placing grease that is too thick will not allow the balls to properly circulate and slide on the rod. Any lightweight type Lithium grease or a 3-in-One type oil is what I see to be mostly recommended...not wheel bearing grease.

Re: Scratched rods from linear bearings

Don't forget that these are recirculating ball type bearings and the tiny bearing balls need to roll freely to circulate in the tracks. Placing grease that is too thick will not allow the balls to properly circulate and slide on the rod. Any lightweight type Lithium grease or a 3-in-One type oil is what I see to be mostly recommended...not wheel bearing grease.

Agree. The SuperLube I use is low viscosity and I had zero problems on thousands of hours on MK2s. The video I posted is surprisingly effective at replacing the shipping oil. I didn’t believe until I tried it.

Re: Scratched rods from linear bearings

Don't forget that these are recirculating ball type bearings and the tiny bearing balls need to roll freely to circulate in the tracks. Placing grease that is too thick will not allow the balls to properly circulate and slide on the rod. Any lightweight type Lithium grease or a 3-in-One type oil is what I see to be mostly recommended...not wheel bearing grease.

Agree. The SuperLube I use is low viscosity and I had zero problems on thousands of hours on MK2s. The video I posted is surprisingly effective at replacing the shipping oil. I didn’t believe until I tried it.

Not sure what video you're talking about but I planned on using naphtha or maybe taking the bearings into work and cleaning them with xylene, last resort as I can't stand the smell of the stuff... I'm still waffling on how I plan to lube bearings though.

Re: Scratched rods from linear bearings

https://www.thingiverse.com/thing:1974253/zip try this for packing the bearings

Re: Scratched rods from linear bearings

According to Josef's handbook, he suggests cleaning the smooth rods with a paper towel and using machine oil. If the carriage is not running smooth anymore he suggested using a grease on the bearings such as "Super-Lube" or any multi purpose grease.

So with that being said, Super-Lube sells machine oil and general purpose grease. I'll go that route and if I have any issues, I'll warranty it.