Ball Mill.
Principle:
Works on the principle of Impact and Attrition.
Diagram:
Construction:
The mill consists of a hollow cylinder fixed on a metallic frame in such a way that it can rotate around its horizontal axis.
The cylinder contains metallic balls occupying around 30 to 50% of total capacity.
The balls are usually made up of rubber, porcelain or metal.
The metallic balls are coated with chrome.
The weight of balls is kept constant and size of balls depends upon the size of feed and mill.
Working:
speed of ball mill
The material to be reduced in size is entered into the machine through a hopper.
The electrical supply to the machine is started after a careful closure of the machine feed.
The mill is rotated at optimum speed.
For effective size reduction, the speed of the machine plays a very important role.
If the machine is rotated at low speed the balls collide with each other and no or negligible size reduction takes place.
If the machine is rotated at very high speed the balls rotate along the cylinder wall due to centrifugal force and no size reduction takes place.
If the machine is moved at an optimum speed (two third speed)
Size reduction takes place as balls move at the top and fall down crushing the material by impact and attrition.
After sufficient time the mill is stopped and the product is collected.
Advantages:
One of the most efficient mills can produce very fine powders.
Suitable for both wet and dry grinding.
As operation takes place in a closed environment, the mill is useful for potent materials.
The mill, after some modifications, is useful for continuous operation.
Disadvantages:
Not suitable for sticky products.
Very noisy.
Balls and casing material may wear off and can compromise the purity of the product.
Applications:
Useful for a variety of materials to produce fine powders.
Commonly Asked Questions.
What is size reduction. Write Principle, Construction and working of Ball Mill.
Write a note on Operation speed for Ball Mill.