Some builders do linear guide ways right and some don't. Bridgeport and Haas are examples of flimsy ways. On the other hand, Makino uses linear guides on some of their very impressive HMCs. Linear guide ways doesn't necessarily mean not rigid. Normally, a quick look at the "trucks" and rails will reveal how stout they are.
There are two reasons why some folks don't like box ways. The first is way lube consumption is much higher compared to linear guide machines which results in more tramp oil in the coolant sump. The second reason is what's sometimes referred to as "stick-tion". It is more obvious when using the handwheel and a very good indicator. Small moves are commanded in .0001" increments but the table doesn't move then suddenly jumps .0005". It can make setups annoying but has no effect on machining accuracy.
You keep repeating that precision and accuracy are important. Can you define more explicitly what you're aiming for? Most builders will quote positioning capabilities of +/- .0002" and repeatability of about half that. However, those numbers are only achieved with a properly installed machine. By comparision, the best knee mill would be rated at +/- .0005". Do you need roundness when interpolating a circle? Positioning for drilling?  |