That would depend on many things including the material and feed rate. For plastic/wood you can get pretty decent precession on these machines within 200-300 m

That would depend on many things including the material and feed rate. For plastic/wood you can get pretty decent precession on these machines within 200-300 microns or so since it should be rigid enough to not deflect much with these materials. For smaller parts any issues of gantry squareness would also not translate to the milled part as much. You can also cut aluminum as long as you are going slow to avoid deflection but don’t expect excellent surface finish and sub 500* micron tolerances. *High end industrial machines can do tolerances within 10 microns when they are operated by an experienced machinist. 100 microns off spec not to mention 500 microns would result in parts being binned normally at least for critical tolerances.