High-speed milling - a low cost avenue for increasing milling capacity?

In Australia, high milling throughputs have been achieved by improving mill feeding and replacing small milling units with larger milling units. In other parts of the world such as Brazil, high milling throughputs have been achieved in small milling units by increasing mill speed. This paper explores the benefits and costs associated with highspeed milling. The results of laboratory and factory experiments, conducted to investigate the effect of mill speed on extraction, are presented. While the laboratory experiments show a reduction in extraction at higher mill speeds, the factory experiments do not conclusively show an effect. However, it is likely that an effect exists. Brazil's experience with high-speed milling is discussed. Much more emphasis is placed on the protection of the roll surface in Brazil. Picots (knobs of hard facing) are required for satisfactory mill feeding. The milling train performance and roll shell maintenance requirements of a Brazilian factory and an Australian factory are compared. The results indicate that higher mill speed in the Brazilian factory results in lower extraction and increases the costs of maintaining the roll surface.