Selecting the Proper Mill for Your Product

Milling is a mechanistically driven process that breaks solid material into smaller pieces. Selection of the optimal mill is a daunting task that often leaves engineers relying on vendor suggestions to decide which mill is right for their job. This article addresses a methodology to score and rank the various mills for use with a particular material. In milling, a materials are broken up due to a few basic breakage mechanisms. Some particles tend to split, creating smaller particles that are one-half to one-third the size of the original particles. This type of breakage is termed fracture. In some cases, particles break as corners are knocked off or subsurface cracks form particles that are considerably smaller than the original particles. This type of breakage is termed abrasion. Some materials require many impacts or stress-strain events to induce breakage. This is termed fatigue and can result in the formation of both small and large particles. The rate of breakage always changes during a fatigue-driven event. Some particles require large strains before breakage occurs. These large strains may be due to plastic deformations, such as in the case of plastic, rubber and ductile metals, separation of fibers and internal structures as…