It is possible to optimize existing technologies, such as the Universal Cutting Mill PULVERISETTE 19, by making a few improvements. The new rotor, with notched edges, has shown its potential on a variety of samples in an impressive manner.
Different Versions of the PULVERISETTE 19
To provide the most suitable mill for each application, the new models were fitted with a variety of powered motors and with changeable rotational speeds. This enables the user to choose an instrument that precisely matches their application needs.
For fine comminution, the faster Universal Cutting Mill PULVERISETTE 19 with variable rotational speeds of 300-3000 rpm should be selected. For powerful comminution, the slower PULVERISETTE 19 is recommended, with its variable rotational speed of 50-700 rpm.
Fast or Slow Running - Which is the Right One?
The characteristics of the sample are the main factor in choosing rotational speed. 
- Fracture behavior: brittle, fibrous, ductile or visco-elastic
- Feed size and final fineness
- Component leakages, such as moisture or essential oils
Figure 1: PULVERISETTE 19 with 300 – 3000 rpm with the new rotor with notched edges made of hardened stainless steel. Image Credit: FRITSCH GmbH - Milling and Sizing
The Benefits of a Continuous System
In comminution technology, there is a distinction to be made between batchwise (e.g. Planetary Ball Mills) and continuous comminution (e.g. Cutting Mill with Cyclone).  A huge benefit of continuous comminution is the ostensibly named “In Process” Control.
It allows sensitive parameters, such as temperature or fine dust development, to receive better monitoring and regulation. If, for example, the output on the Cyclone is distinctly reduced, this may indicate possible adhesions on the sieve cassette. These adhesions are favored due to high temperatures during this process.
The new rotor with notched edges never closes the grinding chamber entirely, which enables optimal airflow. This notably increases the throughput and makes it possible to use extremely fine sieves for bigger amounts. This effect is particularly pronounced for samples with residual moisture (foodstuffs, feed or plants) and samples with a low melting point (plastics).
Direct Comparison of Temperature and Particle Size
Comminuted were 100 g hops at 3000 rpm, with the new rotor with notched edges built from hardened stainless steel, sieve cassette 0.5 mm trapezoidal perforation and high-performance cyclone separator.
Figure 2: Comparison of the temperature of the rotors. Image Credit: FRITSCH GmbH - Milling and Sizing
Figure 3: Distribution comparison. Image Credit: FRITSCH GmbH - Milling and Sizing
Larger Throughput and Less Cleaning Effort
In the future, it will also be possible to process difficult samples, such as greasy rabbit feed pellets, in significantly larger batches. The test series conducted in the FRITSCH laboratory with a variety of samples has, on the whole, shown a highly positive result.
Figure 4: Samples of plastic, wood- and feed pellets: Comminuted with the rotor with notched edges and a sieve cassette with 0.75 mm trapezoidal perforation. Image Credit: FRITSCH GmbH - Milling and Sizing
References and Further Reading
 H.G. Hirschberg: Handbuch Verfahrenstechnik und Anlagenbau: Chemie, Technik und Wirtschaftlichkeit, 1.Auflage 2014
 K. Schwister, V. Leven: Verfahrenstechnik für Ingenieure: Ein Lehr- und Übungsbuch, 2.Auflage, 2014
Produced from materials originally authored by Leos Benes, B.Sc. Pharm. Technologie from Leiter Anwendungstechnisches Labor Fritsch GmbH.
This information has been sourced, reviewed and adapted from materials provided by FRITSCH GmbH - Milling and Sizing.
For more information on this source, please visit FRITSCH GmbH - Milling and Sizing.