Re: Linear rails smoothness, "sticky when carriage moved by hand"!
If they are preloaded, they may feel 'sticky' when trying to move by hand. I have some 30mm ones I plan to use for my build, and they are 'sticky' to move by hand because of the preloading. Also, as mentioned, the grease that they are shipped with to help prevent oxidation and rust will also not help for the movement of them and will make the linear bearings appear and feel 'sticky' even if they are not preloaded. I would clean them, but don't do it until you are ready to install. That grease from the factory is on their for a reason, to keep them from rusting and/or oxidizing.
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