In search of a better lubricant!

The goal is always to reduce friction; low friction means quiet operation and faster speeds. To this end, I decided to experiment with comparing what I've been using for nearly two years now - 3-IN-ONE brand multi-purpose light machine oil - to a possible alternative of dry-film PTFE coatings. My personal preference is bronze bearings, and I can not stress enough that if you try this with LM*UU linear ball bearings you will very likely destroy them as the PTFE coating is liable to scratch off and clog the raceways.

That said, let's get right down to it...

The test uses three identical smooth rods and bearings. The first rod will use 3-IN-ONE oil only, the second rod will use a PTFE treated rod and 3-IN-ONE oil together, and the third rod will use only PTFE treatment. I started by wiping any existing oil off fo the rods and bearings as best we can so we can make a clean comparison.

The PTFE is applied in a nice, heavy coating as evenly as I could manage. Note the "frosted" look the rods have. The solvent is allowed to evaporate, and the rods are turned over and sprayed again to cover the entire surface. Everything was allowed to dry completely (including the napkins underneath) before picking touching them again.






I know from experience that the coating is quite a bit thicker than the clearance of the bearings. To remedy this, the rods were wiped with a clean napkin to remove excess - notice that even after some hard wiping some residue remains (last image).

For the next step, rods #1 (untreated) and #2 (treated) were both oiled using the method I use on my printer: One drop of oil on either side of the brearing, followed by running the bearing back and forth several times to distribute the oil and work it into the bearing-rod interface. Rod #3 (also treated) was not oiled.

As an initial test, I slowly raised one end of the rod assembly and noted which bearings slid first and easiest. For a second test, I quickly iverted the whole assembly to watch how the bearings slid under their own weight.



Noting that there were "sticky" spots at either end of the rods, it seems the unoiled, PTFE-coated rods have the least friction overall. I plan to treat another pair of rods and install them in my Prusa Mendel i2 to see how it fairs, and if it makes any difference. I'd much rather go with a durable, dry lubricant rather than have to deal with the oil slowly soaking into the machine's printed parts and making everything icky. Time will tell!