nhi has been producing various kinds of mills since 1950s, especially in the 1980s, by taking the opportunity of national reform and opening-up policy, nhi began to cooperate with foreign famous ball mill manufacturers to produce and introduced technology, such as the united states a - c company, foster wheeler, mpsi company and france stene alstom. by means of cooperative production and technology introduction, the advanced technology of foreign ball mill is digested and absorbed, combined with the technical advantages of our company, the mill with large diameter and large specifications with independent intellectual property rights is gradually produced on the basis of the original innovation. from the original φ0.9m～φ3.6m series, the ball mills are gradually developed intoφ4m、φ4.5m、φ5m、φ5.5m、φ6m、φ6.4m、φ6.7m、φ7.3m andφ8m diameter series etc.