Three roll mill
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A three roll mill is a machine that uses shear force created by three horizontally positioned rolls rotating in opposite directions and different speeds relative to each other, in order to mix, refine, disperse, or homogenize viscous materials fed into it.
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[edit] Operation of a three roll mill
The three adjacent rolls of a three roll mill (called the feed roll, centre roll and apron roll) rotate at progressively higher speeds. Material, usually in the form of paste[disambiguation needed 
], is fed between the feed roll and the center roll. Due to the narrowing space between the rolls, most of the paste is rejected to the feed region. The part that makes it through the first in-running nip experiences very high shear force. Upon exiting, the material that remains on the center roll moves through the second nip between the center roll and apron roll, which subjects it to even higher shear force due to the higher speed of the apron roll. A knife blade then scrapes the processed material off the apron roll and transfers it to the apron. This milling cycle can be repeated several times to maximize dispersion[disambiguation needed ].
The gaps between the rolls can be mechanically or hydraulically adjusted and maintained. Typically, the gap distance is far greater than the particle size. In some operations, the gap distance is gradually decreased to achieve the desired level of dispersion.
[edit] Application
Three roll mills are widely used to mix electronic thick film inks, high performance ceramics, cosmetics, plastisols, carbon/graphite, paints, printing inks, pharmaceuticals, chemicals, glass coatings, dental composites, pigment, coatings, adhesives, sealants, and foods. With the recent development in technology, they are also utilized in the production of cable cover, electronics, soap, and artificial plastics.
Small bench models are used for bench-top development work, laboratory work, and low volume production. Larger bench and floor models are built to meet different production needs from pilot plants to large volume productions.
[edit] Production run rate
The larger diameter rollers provide more shear force and a higher production run rate.
| Roller Diameter X Roller Effective Length | RPM on Exit Roll | Gallons/hr | Lbs/hr |
|---|---|---|---|
| 2.5″X5″ | 174 | 0.25-1.25 | 1.0-5.0 |
| 6″X12″ | 217 | 1.8-8.8 | 9.0-44.0 |
| 9″X20″ | 170 | 3.5-17.2 | 14.0-68.8 |
| 12″X30″ | 170 | 7.1-34 | 28.4-136 |
| 16″X32″ | 157 | 9.0-45 | 36.0-180 |
[edit] Manufacturers of three roll mills
Torrey Hills Technologies
Mikrons
Charles Ross & Son Company
Sigma Equipment Corp.
[edit] References
- ^ Harper, Charles A. Electronic Materials and Interconnection Handbook (New York: The McGraw-Hill Companies, Inc., 2004), pp. 570-571.
- ^ Prudenziati, M. (editor). Thick Film Sensors (Handbook of Sensors and Actuators) (Amsterdam: Elsevier Science B.V., 1994), pp. 121-123.
- ^ http://www.threerollmill.com/specifications.html
- ^ http://www.sigmaus.com/3_roll_mill/index.html
