Does rail grease type actually matter?

[RhyminGarFunkle]

Obviously lubrication is important, but is it really crucial to use a specific formulation? Everywhere I've looked says to use white lithium grease for the linear rails, but I've never actually seen anyone explain why that in particular over other kinds of grease.

I'm getting ready to build my first Voron, and my inclination is just to use the same stuff I use on motorcycle bearings and axles, Bel-Ray waterproof grease - if it's good enough for thousands of miles at 60+ MPH, surely it's good enough for the 1-3 MPH my printer rails will be moving at? I've considered that grease made for parts that move at 65+ MPH might be too thick for the much slower printer parts, but I use the same grease on the triple-tree bearings (where the front fork and handlebars meet the frame of the bike) which move much more slowly and in a limited range, and it works great there too.

Is there a reason for white lithium grease specifically, or is that just kind of what everyone says to use because if you say, "Most anything will work" someone will end up slathering their rails in Crisco?

 

[fionoz]

Don't slather your rails in anything PLEASE. There are way too many factors to consider.
I wouldn't recommend white lithium grease either.

Just buy some ep2. It's pretty cheap.

If you can't get that, or have some really cheap rails that you just want to get working, use white lithium.

 

[RhyminGarFunkle]

Okay, buy why EP 2? Why not lithium or aluminum/barium complex grease (like the Bel-Ray I brought up)? What makes one type of grease best for this particular application, and other types completely unsuitable?

 

[NoGuru]

Okay, buy why EP 2? Why not lithium or aluminum/barium complex grease (like the Bel-Ray I brought up)? What makes one type of grease best for this particular application, and other types completely unsuitable?

It's simple. It comes down to what is required from the parts and motion system.

Would you put 0W-30 in your motor cycle? Probably not since that is intended for colder temps. So some Grease is better at doing a certain job better then others.

So the EP2 is recommend based on longevity, viscosity, and chemical resistance. Sure you can use other grease but you might have to re-apply it more often.

 

[RhyminGarFunkle]

So the EP2 is recommend based on longevity, viscosity, and chemical resistance. Sure you can use other grease but you might have to re-apply it more often.

That's what I'm asking, what about those properties make it a good choice? For example, many (seemingly) knowledgeable people recommend oiling rails instead of greasing them, because with thick grease the balls can't roll across the rails, so they instead slide which increases friction and wear over time. The downside of oiling is that it definitely needs to be reapplied more frequently. When I compare the data sheets of the EP2 to the Bel-Ray, one of the few major differences is the Bel-Ray is significantly less viscous (but still plenty thick to stay in place). Wouldn't this decreased viscosity be a plus, allowing for easier rolling without needing be reapplied as frequently as oil? Why or why not?

I'm not trying to be difficult about this, and I'm certainly not trying to say, "My grease is a better choice than what everyone else has successfully used for years." But all of the info I see about grease selection - including in this thread - basically comes down to, "Use this because it works well." I want to know why it works well, and why alternatives work less well.

 

[Dave]

There are a ton of opinions on grease, and most of them are just opinions. We have lots of data that EP2 works well in printers with lower chamber temps, but we also know that if you get above about 60 degrees C, then EP2 will fail prematurely. One of the Voron Crew members who runs a print farm is evaluating higher temp greases so that we can make a better recommendations. I’m currently testing Valvoline Cerulean, and others are looking at Mobilith high temp formulations. I still want to test out Red and Tacky in a hot chamber, but haven't yet.

What you want to avoid is greases with solid additives like molybdenum disulfide or Teflon. Will they work? Sure! But they aren’t optimized for use with bearings. You want an Extreme Pressure (EP) grease for that. Plus, the solids aren’t great for many bearings. They are really intended for sliding, not rolling interfaces.

In general, any EP2 grease will work for most printers. We recommend the mobilux just because it’s available and because we know it works. It’s DEFINITELY NOT optimized for higher temps, and I can personally verify that it fails prematurely with 70 C chamber temps. So, do you need to panic? Not really. Just lube and clean more often. For a legacy, Mobilux EP2 will work perfectly for a long time. For a Doom Cube running at 75 C, it will fail at the Tap after a few dozen hours (if you are running Tap).

So, what about a recommendation? I can say is that the Valvoline Cerulean grease has been pretty good for me for a few dozen hours with no problems yet. It’s about $8 for a full sized tube, so the cost is pretty cheap. The Mobilith is a synthetic that will probably hold up at high temp better. The Mobilith is probably a better bet, but is a whopping $20 for a giant tube. (So expensive!!! ) We (Voron Crew) may be making a change to the official recommendation at some point, but for now, we still recommend Mobilux EP2 for most printers with chamber temps below 60 C.

 

[Yaaj]

I use Kluber NBU15 because I have some left after a milling machine spindle rebuild. Barium soap, synthetic, low viscosity. Max temp 130°C, dropping point 220°C. Very easy to apply with a syringe.
Probably overkill. IIRC it was hyped for printer leadscrews like 5-10 years ago, and was available from eBay in Europe at this time (50g tubes).
I wouldn't use a waterproof grease. They tend to be extremely sticky.

 

[vinnycordeiro]

There are a ton of opinions on grease, and most of them are just opinions. We have lots of data that EP2 works well in printers with lower chamber temps, but we also know that if you get above about 60 degrees C, then EP2 will fail prematurely. One of the Voron Crew members who runs a print farm is evaluating higher temp greases so that we can make a better recommendations. I’m currently testing Valvoline Cerulean, and others are looking at Mobilith high temp formulations. I still want to test out Red and Tacky in a hot chamber, but haven't yet.

What you want to avoid is greases with solid additives like molybdenum disulfide or Teflon. Will they work? Sure! But they aren’t optimized for use with bearings. You want an Extreme Pressure (EP) grease for that. Plus, the solids aren’t great for many bearings. They are really intended for sliding, not rolling interfaces.

In general, any EP2 grease will work for most printers. We recommend the mobilux just because it’s available and because we know it works. It’s DEFINITELY NOT optimized for higher temps, and I can personally verify that it fails prematurely with 70 C chamber temps. So, do you need to panic? Not really. Just lube and clean more often. For a legacy, Mobilux EP2 will work perfectly for a long time. For a Doom Cube running at 75 C, it will fail at the Tap after a few dozen hours (if you are running Tap).

So, what about a recommendation? I can say is that the Valvoline Cerulean grease has been pretty good for me for a few dozen hours with no problems yet. It’s about $8 for a full sized tube, so the cost is pretty cheap. The Mobilith is a synthetic that will probably hold up at high temp better. The Mobilith is probably a better bet, but is a whopping $20 for a giant tube. (So expensive!!! ) We (Voron Crew) may be making a change to the official recommendation at some point, but for now, we still recommend Mobilux EP2 for most printers with chamber temps below 60 C.

Also, if we consider Hiwin's recommendations for lubrication, as seen on page 10 of their linear guideway catalog, they recommend:

Linear guideway must be lubricated with the lithium soap based grease before installation. After the linear guideway is installed, we recommend that the guideway be re-lubricated every 100 km. It is possible to carry out the lubrication through the grease nipple. Generally, grease is applied for speeds that do not exceed 60 m/min faster speeds will require high-viscosity oil as a lubricant.
(...)
The recommended viscosity of oil is about 30~150cSt. The standard grease nipple may be replaced by an oil piping joint for oil lubrication. Since oil evaporates quicker than grease, the recommended oil feed rate is approximate 0.3cm3/hr.

 

[3dCase]

As long as I have been a professional machine builder, designer and maintenance engineer, this exact question has never failed to divide the audience to the maximum level. It is virtually the same as starting political or religious conversations on social media.
First thing is, you are lubricating, that is always better then not lubricating. Yes maybe not the ideal stuff but that is not always instantly fatal.
Second question should be "do I need to improve how I lubricate?" And this depends on the situation and what you use right now.
We can talk long and short about these things, but one statement remains always true. If you stick to the manufacturers guidelines you will not need to worry about any warranty implications.
For all else, one simply needs to follow some best practices, and to do those correctly, you need to know about the basics of lubrication. One such is explained in this blog (not affiliated).

The Basics of Industrial Lubricant Selection

There are several factors to consider when selecting the right industrial lubricant. A manufacturer’s recommendation is a great starting point, but it doesn’t have to be the only option. Most manuals are written for ideal conditions, but these guidelines don’t address the real environment in...

blog.chesterton.com

I know their examples are not 3d printers but the principles of lubrication are the same. Read this and I hope it helps you to understand the criteria used for correct lubrication choice and all the other related things such as frequency and quantity.
In the mean time keep doing what you do and keep it clean as well. Those two things will prove a massive boon for the performance of your moving things. Just stay away from obviously wrong things like abrasive solid lubricants or utterly not fit for purpose types such as super high tack high viscosity high temperature high pressure grease for tracked vehicles for instance.