Many industries make use of hammer mill for size reduction purposes. Size reduction is applied to materials that can be crushed, shattered or pulverized into smaller pieces so that the production of products will be more economical and efficient. A hammer mill belongs to a much larger group of equipment that includes jaw crushers, roll mills, ball mills and shredders with the same functionalities.
How do hammer mills work
Industrial hammer mills have a rectangular chamber made from steel that houses a shaft where swinging hammers are attached. When the shaft rotates at high speed, the hammers strike at the material with force. Size reduction occurs from the impact of the hammers, collision with the walls of the chamber and through particle to particle contact. At the discharge opening of the hammer mill, a perforated screen is installed to allow properly sized particles to be released through the holes. Larger particles are retained for further grinding until the proper size is achieved. Discharge of particles work through the force of gravity but in pneumatic hammer mills, pneumatic suction is used to assist in the discharge of lighter materials like paper, wood and products with bulk density. In order to drastically alter the size of particles discharged, screen size, shaft speed and hammer configuration can be changed. For example, a smaller screen with faster speed and more hammers can produce a finer end product.
Hammer mills vs. ball mills
Due to the versatility of the hammer mill, the equipment is common in the pharmaceutical industry. However, there is equipment that also has the capability to perform the function of the hammer mill and it is referred to as the ball mill. Ball mills grind materials through the use of media. The equipment is typically used to pulverize materials like paint, pyrotechnics and ceramics. However, the milling process is quite long and tedious because it relies on tumbling ceramic balls to crush materials into powder form. The process of cleaning is also quite slow rendering the equipment unusable for days or even a week.
Requirements of the pharmaceutical industry are more readily met by hammer mills whether for continuous or batch production. Drug developers often make use of the hammer mill for R & D purposes that require precision particle reduction. The hammer mill is also the equipment used to reclaim broken tablets so that they can be reformed. When pharmaceutical products are mass produced, the industry requires the speed of the hammer mill. Hammer mills can operate at speeds ranging from 1,000 to 6,000 rpm while producing at least 1,000 kilograms per hour. Some of the more advanced hammer mills have the capability to increase the viability of dry and wet ingredients because of its dual side assembly. One of the blades performs the function of a hammer to shatter material into smaller sizes while the knife-life side slices through wet ingredients. Additionally, some of the mill rotor assemblies can be reversed to adjust according to specific product behavior while mill rotation remains unchanged.