How far can M1 reach with the slide rail?

A simple answer would be as far as the length of the slide rail.

With the slide rail, the M1 can be set free from its fixed mounting location and become moveable. In which case the M1 can pick and place object form one end to another end of the rail, draw large picture, engraving in bigger range, printing long object(longer than most the  3D printers we can find from the market). The slide rail does extend the capabilities in a great deal. The slide rail we provide is 1.2 M long, and you can replace it with a longer one.