Slides v Rollers

[Jonathan]

One advantage of a linear guide system with sliding contact (e.g. dovetails) is that you get large areas in contact with an oil layer in between, which is much better for damping than bearings with point contact. But as irving said, most modern machines seem to use rails now as there's other ways to alleviate problems with resonance.

[m_c]

It all depends on how much money you spend. Lots of top end machines still use box ways combined with turcite, as they give a sturdier setup with the natural damping of cast iron and the turcite reduces stiction compared with conventional metal on metal. The issue with linear ways is you effectively introduce a bit springy steel into the machine, however linear rails implemented correctly it's not that big an issue.

Off course linear rails have the advantages of having less stiction, require pretty much no maintenance over their life, and are far easier to replace if they do happen to wear out.