Round Rail Linear Ball Bushings - Dry Lube Option?

[tommo]

Hello,

I have an application that uses Linear Round Rail Ball Bushings on a 1.0"shaft.

The process develops a powder that mixes with the grease used to lubricate the bushings. The operators like to liberally grease the bearings, resulting in greasy sticky shafts that this powder sticks to, and results in damaged bearings and shafts. The temperature of the process is about 140F / 60C

We are looking at a number of alternative arrangements to this, but we have a lot of machines in operation in this configuration.

Long story short - has anyone tried using a dry-lube on ball-bushings, such as graphite or PTFE?

I had an application a while ago with a chain in a bakery oven, they mixed graphite with water and painted it on the chain, the heat dried out the water and left the graphite behind.

I think graphite would be better than grease, as it would coat the balls and channels and allow the balls to roll freely around the channels.

The bearings are only loaded to about 20% of their rated capacity.

Any hints would be appreciated.

 

[unclesyd]

I've heard it discussed but have never seen anything put into practice. Here are three suppliers of dry film lubricants that you might want to give a call. All have been around for some time and did have good technical staffs.

http://www.metalimprovement.com/em_coating_services.php

http://www.sandstromproducts.com/index.htm

http://www.achesoncolloids.com/index.asp

 

[tommo]

Thanks UncleSyd, I have lodged an inquiry with one of the companies you mention. You gave me some excellent references!

I would love to read some if anyone else had had experience with ball bushings and dry-lubing.

Thanks

Tommo

 

[diskullman]

Pacific Bearing makes a teflon lined bushing to replace these. Lee Control has linear pillow blocks that use sealed cam followers

http://www.pacific-bearing.com/products/viewProduct.cfm?ID=1

http://www.linearmotion.com/linear_bearings.asp

Russell Giuliano

 

[tommo]

Thanks Russell,

Our new machines will use the Lee Control Linear Pillow Blocks, we are looking forward to the trial results. Very simple idea, someone is making a good profit on those units!

The linear bearings are not suitable for us as they need more power to drive, as the co-efficient of friction is 0.1, and the ball bushings are generally rated at 0.01. The motor power is maxed out currently and there isn't enough room to put in a larger motor.

Igus also offer an excellent bush with grooves thru the polymer to allow particulate to channel through the bearing an d not get stuck underneath it.

Would still be interested to see if anyone has used dry lube with ball bushings.

Tommo

 

[plasgears]

We had high temp applications that were lubed with milk/magnesia. Should be worth a try.

 

[tommo]

Thanks Plasgears,

That is extremely interesting, I have never heard of this before - but searching the web has indicated that this is indeed used as a high temp lubricant.

Does the "milk of magnesia" form a powdery, slippery coating?

Is it cleaner than graphite?

Thanks for a most interesting suggestion

Tommo

 

[unclesyd]

Here is a product "NanoLub" based on Nano technology that is being developed for mutiple uses. It is based on Nano particles of Tungsten Disulfide (WS2). WS2 in itself is an excellant lubricant and using it at the Nano level looks even better.

http://www.apnano.com/

Another thing you might look at is the drop in ceramic system. I would look at this system with the Nano Lub product.

http://www.lm76.com/prod01.htm

 

[tommo]

Thanks UncleSyd!

I will look into the nano-lube product, I have a lot of interest in dry lube at the moment. There are so many areas where wet lubes are limited by their wet properties.

Tommo

 

[plasgears]

tommo,

The exact mechanism that makes milk/magnesia work escapes me, but stability of the powder under high temp seems to be a factor. We used it in jet afterburner relative motion locations.

 

[ENG35UK]

igus makes a range of self-lubricating linear bearings. You seriously do not need to lubricate these bearings at all. You'd prob need to look at the DryLin R range.

 

[volpegrigia]

There are some product used succesfully in applications such as yours. Molykote 321R is a spray that air dries and is an effective solid lubricant. Also Klueber has a solid lube with similar charateristics to the 321R. You can also improve the performance in a linear baeraing application using chard chrome plated shafts which can, in conjunction with the solid lube, provide excellent results.

 

[beltingman]

I have been supplying recirculating linear ball bearings for over 15 years. I am not an engineer but I have helped many industrial users reduce their maintenance cost for linear systems. I have had many customers use a dry lube with great success. First you need to understand that any drylube that changes the shaft dimension (like a coating that lays on top of the shaft) is not recommended by any manufacturer. You also need to understand that the use of a traditional lubricant is to provide a thin film between the rolling elements. Doing this reduces friction and caused less heat. It also help move contaminants away from the surfaces. Using a drylube eliminates this film and if a proper drylube is not used, you may end up with a premature failure.

The dry lubes that I have seen work in this application have a PTFE particle but not just any PTFE. The particle has to be processed so the average particle size in the lube is under 1 micron. The particles need to fill into the low valleys in the shaft material only visible under a scope. Typically this type of lubricant can not be removed except by abrasion.

What you should expect is that the PTFE (which is inert and does not attract dust and dirt)will keep contaminate from sticking to the shaft and bearing. Because PTFE is one of the most lubricide natural substances, it should reduce friction and keep friction causing heat low.

One problem is that you might notice slightly more noise because your rolling elements are now making contact with the shaft. Another draw back is that you need to pay attention to relubrication intervals.

The lubes that I have seen work is a product called Tetralube, Superlube, and Thomson industries used to offer a linear lube with PTFE in it (although I'm not sure the linear lube is classified as a dry lube).

The plain bearings like the Simplicity bearing is a great alternate but you should review the application with their engineers cause as the bearing wears so does the tolerance and it could affect your process. The shaft alignments are also much more critical when using plain bearings on a two shaft system.

As always, you should test the lubricants and establish new relubrication schedules when changing lubes.

Good luck