How it Works
The Original Three Roll Mill
When ROSS produced the first Three Roll Mill in 1869, we revolutionized pigment dispersion — with superior consistency and finer dispersion than ever before. Today, thousands of ROSS Three Roll Mills are in operation and producing high quality coatings, paints, ink, pharmaceutical ointments, cosmetics and advanced materials all over the world. Suitable applications include medium to high viscosity materials that cannot be adequately dispersed in conventional high shear mixers.
Benefits of Choosing a ROSS Three Roll Mill
What does a ROSS Three Roll Mill do?
A Three Roll Mill is composed of three horizontally positioned rolls rotating in opposite directions and at different speeds. The material to be milled is placed between the feed and center rolls, quickly adhering to the rotating surfaces and spreading out evenly. Available in bench and floor models ranging from 2.5” x 5” to 9”x 24”, these mills can accommodate a wide range of products and production lines. Fully compliant with ANSI 2017 safety standards, ROSS SyCon Control Panels supplied on ROSS Three Rolls Mills include emergency braking (stops the rolls in less than 1 revolution), a wash mode feature and a proximity switch that ensures a nip guard is in place during the cleaning cycle.
How does a ROSS Three Roll Mill work?
Shear forces between the adjacent rolls break up the agglomerates in the product. When the apron roll is engaged, the material transfers to it while being subjected to additional shear forces at even higher intensities. The distance between each roll is adjustable and impacts both shear level and throughput. Gap size is typically set at 0.005" and as tight as 0.001" in some cases. Milled material is scraped from the apron roll by a take-off knife. The cycle can be repeated to improve dispersion quality or until an equilibrium particle size distribution is reached. Optional features include explosion-proof configuration, hardened steel rolls with ceramic coating, hydraulic roll pressure monitoring devices, rotary pressure joints for forced heating or cooling of rolls, and Teflon or bronze end plates.
Across the process industries, Three Roll Mills are used to achieve a high quality dispersion in pastes, gels and other semi-solids. Suitable applications include medium to high viscosity materials that cannot be adequately dispersed in conventional high speed mixers.
The mixing technologies utilized in the production of specialty inks vary from one custom formulation to another. Mixer selection is based on a number of factors but primarily viscosity profile and shear input.
The three roll mill remains to be one of the best methods for preparing very fine particle dispersions. This bulletin discusses some best practices to help users operate the three roll mill safely and efficiently.