ROLLER MILL
Roller mills are also known as reduction mills. Roller mills are mills that use cylindrical rollers, either in opposing pairs or against flat plates, to crush or grind various materials, such as grain, ore, gravel, plastic, and others.
Roller mills consist of two to five smooth five rollers operating at different speeds, thus the size reduction is effected by the a combination of compression and shearing action.
The particle size reduction is mainly occurred by the pressure between the two or more rollers present in the mill.
By the attrition of the rollers the reduction in the size takes place and shows free flow properties.
Different roller mill
HISTORY
The invention of the rolling mill is attributed from Leonardo da Vinci. Earliest rolling mills were slitting mills, which were introduced from what is now Belgium to England in 1590. These passed flat bars between rolls to form a plate of iron, which was then passed between grooved rolls (slitters) to produce rods of iron. Later this began to be rerolled and tinned to make tinplate.
The slitting mill was adapted to producing hoops (for barrels) and iron with a half-round or other sections by means that were the subject of two patents in 1679.
Some of the earliest literature on rolling mills can be traced back to Christopher Polhem in 1761 in Patriotista Testamente, where he mentions History of the is wanted to tilt only one bar with a hammer.
Thomas Blockley of England in 1759 for the polishing and rolling of metals got the pantent. Another patent was granted in 1766 to Richard Ford of England for the first tandem mill. A tandem mill is one in which the metal is rolled in successive stands, Ford’s tandem mill was for hot rolling of wire rods.
Rolling mills...
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DISADVANTAGES:
If the temperature of the work piece is not uniform the flow of the material will occur more in the warmer parts and less in the cooler.
If the temperature difference is great enough cracking and tearing can occur.
Roll deflection
Maintaining a uniform gap between the rolls is difficult because the rolls deflect under the load required to deform the work piece.
Little or no effect on fiber materials.
REFERENCES:
1. Lieberman, Herbert A, Lachman, Leon (2009), Industrial pharmacy: Pharmaceutical dosage form-milling. Banglore, Pune. ISBN: 978-81-239-1679-8.
2. Mehta RM, Pharmaceutics-I: Size reduction (1996), Page no: 90.
3. http://www.feedmachinery.com/glossary/equipment/roller_mills.
4. http://en.wikipedia.org/wiki/Rolling_(metalworking).
5. http://www.directindustry.com/prod/neuhaus-neotec/roller-mills-pharmaceutical-industry-3759.
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