A certain distance, that is, more than 0.0 1mm, because the precision of the manufactured equipment is not high, it is useless to have such high precision, as long as it meets the demand. Of course, there are also high-precision, which can reach micron level, but that is only used in specific occasions, such as aerospace and other precision industries. At present, the domestic rolling accuracy is constantly improving with the improvement of manufacturing level, and the efficiency is constantly rising. Rolling accuracy is an important index to measure the rolling level.