23 Jan

Milling: Milling in the Laboratory

A centrifugal or rotor mill  is a grinding mill which uses impact and cutting or shearing for the comminution of laboratory samples to small uniform sizes for analysis.  Sharp cutting teeth use impact forces to initially reduce the size of the sample.  The sharp cutting teeth are revolved within a sieve; the shearing forces between the trapezoidal shape of the sieve opening and the sharp teeth reduce the sample size further.  As soon as the sample is reduced to the size of the holes in the sieve the sample leaves the cutting chamber.  Cutting heads and sieves are ordered separately and are specific for the sample.  Rotor or centrifugal mills are for medium hard or brittle samples. Manufacturers such as Fritsch offer accessories which make the mill more universal – handling samples which may be oily or have residual moisture.  The rotary or centrifugal mill is a good choice for temperature sensitive samples such as powder coatings as the design of the mill allows for air cooling.  Other accessories include vibratory feeders and specially designed collection containers for handling high volumes.

Robin Prymula