Dry Lube for Ball Screws

[Andrew22]

Has anyone had long term sucess using a dry lube like silicone or graphite for ball screws? I've had issues with a thin grease film being a dust magnet, and have had to clean a mix of grease and compressed dust off of the screws several times. There's a real potential for this to cause problems, so I'm either going to have to figure out a pre wiper system or use a dry lube so fine dust won't stick.

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[wizard]

You are right that grease and dust will cause problems. it can infect cause the ball ways to gunk up and cause a ball screw failure. To guard against this you need frequent cleaning and lubrication of the ball screw nut. by the way this applies to you linear bearings too.

I've never tired dry lubes so can't give advice there.

At work we run some linear bearings absolutely dry due to issues of contamination of product. I can't really recommend this either unless you need have a budget for frequent replacements.

[handlewanker]

Hi, as I've just started out in CNC but have been machining you ages, I realised the problem that ball nuts and screws have with lubing and dirt.........this is a theoretical solution so I think it would solve the problem, especially is someone is thinking up ways to lube and dirt exclude in one hit etc with long term benefits and no constant maintenance.

Basically, what is involved is a constant low pressure air supply with an oiler, the same as you would have on rotary pneumatic tools etc,......the air supply would be plumbed into the ball nut to produce a positive pressure all the time....not much but a constant flow....with lubricant.

This would blow out any dirt and prevent any dirt that lands on the screw from being screwed into the nut as it traverses along and the thin oil will keep the nut/screw lubed which is more than it gets in normal use

The small amount of oil is a constant lube source and is total loss so that there is no need to change it when it gets dirty, that is it's maintenance free....the small amount used won't make a mess in the coolant as you normally get more waste oil from hand lubing anyway.

This idea is for someone who wants to try a method but is stuck for ideas.
Ian.

[Andrew22]

I've been regularly cleaning the screws, but it builds up quick enough that I want to find a better solution. At first I was re-lubing with white lithium grease as recommended, but that creates a dust magnet. My linear bearings are working perfect, the seals are tight enough that no dust gets through. I definitely don't have a budget to be replacing them frequently either, so I'm hoping I can find a dry lube that will work. I've done some testing with graphite, which seems to be flaking off so I'm not too confident about that. Silicone goes on clear so I can't really see how well its holding up.

[Andrew22]

Air pressure or oil pressure would work to keep debris out, unfortunately there's no easy way to hook up a hose to my ball nuts, there's very little clearance even for regular maintenance and lubrication.

I have a feeling the dirt on these screws is screwing up the alignment on my machine too. Normally my servos would fault if anything caused a jam, however the couplers that joint the motor shaft to the screws are a weak link. They rely on clamping force alone to not slip, and this dust and grease could be enough to cause a temporary jam. The servos keep on spinning and I get the equivalent of lost steps.

[louieatienza]

I wish I remembered the thread, but someone here a long while back took strip brush, rolled it into a circle, and used that as a wiper. Other than that, the only other way is to fabricate or buy bellows (they make round ones to slip over ballscrews) and pump air in them. Doesn't have to be a lot of air either; just enough that it has some light pressure, to keep the dust out...

[Bubba]

I wish I remembered the thread, but someone here a long while back took strip brush, rolled it into a circle, and used that as a wiper. Other than that, the only other way is to fabricate or buy bellows (they make round ones to slip over ballscrews) and pump air in them. Doesn't have to be a lot of air either; just enough that it has some light pressure, to keep the dust out...

I am one of the ones that made/uses a brush rolled into a circle for a wiper on my mill/drill. That was somewhere back around 2000 and it still works just fine. The biggest help though is having some sort of shielding (way cover) to keep most of the swarf out of the screw to begin with.

[louieatienza]

I am one of the ones that made/uses a brush rolled into a circle for a wiper on my mill/drill. That was somewhere back around 2000 and it still works just fine. The biggest help though is having some sort of shielding (way cover) to keep most of the swarf out of the screw to begin with.

Bubba, do you have a pic of your setup? My mini-mill has way covers so the screws stay really clean, but on my router table rebuild, it would be tough...

[RCaffin]

I made up some felt wipers, reinforced with Al shim, and stuck them around the ball screws. Then I soaked the felt with oil.
So far - very good.
Ah - I also put covers over all the ways etc so that 99% of the swarf never comes near the rails or screws. That helps!

Cheers
Roger

[wizard]

While this may seem obvious, paling to your ball screw manufacture might help as they would be aware of these sorts of issues. There may very well be a "dry" solution available that we don't know about.

Beyond that maybe the real option is to go wet, not as in grease but rather oil. I've seen some machines that have ran the one shot lubricator to the ball nut. Given a fresh supply of oil you will likely wash out the gunk before it builds up too much. As someone else sated above a total lost Lub system.

A third option would be to go to an industrial bearing / automation supply house like Kaman. Describe what is going on and then ask for suggestions. Just be careful, it would be very easy for them to suggest something that cost more per once than gold. Case in point we use a lubricant on some bearings at work the tis call Krytox (spelling maybe) which is an insanely expensive way to lubricate bearings.

A fourth option would be a pressurized system. Here we are talking about using an oil mist system or maybe a drip oiler in line with an air line going the ball nut. The idea here is that you supply the bearing continuously with a tiny amount of oil under pressure.The air pressure helps to blow out dust. The problem with such solutions is the high oil usage.

A fith possibility is a ring around the nut that blows the screw off just before entering the screw.

[Bubba]

Bubba, do you have a pic of your setup? My mini-mill has way covers so the screws stay really clean, but on my router table rebuild, it would be tough...

I'll do some hunting around today to see if I can find anything. That was many computer crashes ago so am not sure if anything has survived and I have no plans at this time to tear the machine down to that level to get any new pic's!

[handlewanker]

While this may seem obvious, paling to your ball screw manufacture might help as they would be aware of these sorts of issues. There may very well be a "dry" solution available that we don't know about.

Beyond that maybe the real option is to go wet, not as in grease but rather oil. I've seen some machines that have ran the one shot lubricator to the ball nut. Given a fresh supply of oil you will likely wash out the gunk before it builds up too much. As someone else sated above a total lost Lub system.

A third option would be to go to an industrial bearing / automation supply house like Kaman. Describe what is going on and then ask for suggestions. Just be careful, it would be very easy for them to suggest something that cost more per once than gold. Case in point we use a lubricant on some bearings at work the tis call Krytox (spelling maybe) which is an insanely expensive way to lubricate bearings.

A fourth option would be a pressurized system. Here we are talking about using an oil mist system or maybe a drip oiler in line with an air line going the ball nut. The idea here is that you supply the bearing continuously with a tiny amount of oil under pressure.The air pressure helps to blow out dust. The problem with such solutions is the high oil usage.

A fith possibility is a ring around the nut that blows the screw off just before entering the screw.

Hi, I like the idea of the pressurised nut with oil mist as in air power tools etc....would work for linear way bearing blocks too.

A ballscrew drive is almost the same as an open ball race....one spec of gunge and it goes tight.

I suppose if it was designed right a small moving vane type rotary air compressor attached to the end of the ball screw would work as it then only blows when the screw turns....saves on having a noisy big air compressor.....it's flow not pressure that you need.

I think something on those lines would work better if it was driven by a small electric motor as the screw turned, that would save on wasting oil when the screw or linear bearing block was stationary.

Anyone who's into live steam engines like locos or traction engines will be familiar with the cam operated oiler system that metered a small squirt of oil to the steam line each time the crank rotated.

A clean room works on the principle of a positive air pressure inside....not much, but dust does not work its way into a pressurised interior.......I'm thinking on those lines for my garage too as it keeps getting a layer of dust on everything that's not covered up......day time the air warms up and blows out while at night it cools down, contracts and sucks everything that floats inside.
Ian.

[underthetire]

Hi, as I've just started out in CNC but have been machining you ages, I realised the problem that ball nuts and screws have with lubing and dirt.........this is a theoretical solution so I think it would solve the problem, especially is someone is thinking up ways to lube and dirt exclude in one hit etc with long term benefits and no constant maintenance.

Basically, what is involved is a constant low pressure air supply with an oiler, the same as you would have on rotary pneumatic tools etc,......the air supply would be plumbed into the ball nut to produce a positive pressure all the time....not much but a constant flow....with lubricant.

This would blow out any dirt and prevent any dirt that lands on the screw from being screwed into the nut as it traverses along and the thin oil will keep the nut/screw lubed which is more than it gets in normal use

The small amount of oil is a constant lube source and is total loss so that there is no need to change it when it gets dirty, that is it's maintenance free....the small amount used won't make a mess in the coolant as you normally get more waste oil from hand lubing anyway.

This idea is for someone who wants to try a method but is stuck for ideas.
Ian.

Your on the right track here. Mori Seiki and other high end machines have been using this method for more than a few years now. Even on the thrust bearings. Very little service, and very few failures.

Sent from my SM-T813 using Tapatalk

[handlewanker]

Well that's nice to know....at least it's a viable solution if the big boys are already using it......just needs some form of air supply that doesn't need a big compressor switching on and off all the time..........I don't think there would be much pressure involved as long as it created a positive flow.
Ian.

[ger21]

Are you still having issues with the seals on this? All you should really need to do is give it a shot of grease once week, and it should keep the dust out, if you have decent seals.