I am attempting to construct model tank tracks with accompanying wheels and sprockets. All parts will be printed in PLA. The tracks will be driven by electric motors.
What would be a suitable grease for this project to minimize friction without damaging the plastics.
I use cosmetic vaseline - petroleum jelly. Usually it is white to transparent and odorless. It's cheap and available in all drugstores and cosmetics stores.
As suggested by Tom van der Zanden I'm adding additional info about interactions of vaseline and plastics. I've found many web sites which claim that vaseline can damage plastics but none of them really proved that statement. There is nothing about it neither on producers sites nor wikipedia or any other believable sources I've found. So according to it and my practice I'm pretty sure that vaseline won't damage popular plastics (including common filaments).
The only information I've found is that vaseline can damage natural rubber but I cannot confirm that on my own.
Of course it might not be true for some materials so be careful and check the interactions first on invisible side or on refuses.
You may find a solution with the common lubricant containing PTFE, often called Super Lube. It is described in manufacturer's literature as non-reactive with virtually everything. It is available at a reasonable price as plumber's grease (look for either Teflon or PTFE in the ingredients) in various quantity containers. When used on metal, you may get black residue. With plastic, some color of the plastic will appear as the surfaces wear. It has good sticking power too.
I have been using sewing machine oil for my 3D printed extruder gear for a couple of years, without any noticeable wear so far.
In general, I believe any kind of low viscosity oil would do, but then again, it also depends on the environment in which you plan to use the model. If you plan on using it outside, for instance, you probably should get some grease that does not attract dirt, as the dirt itself will grind down the gears quickly.
