Table of Contents
Ball Mill
Principal of Ball Mill
It work on the principle impact and attrition.
Construction of Ball Mill
- It consists of a hollow cylinder which is mounted on a metallic frame.
- In such a way that it can be rotated on it clockwise (Longitudinal axis) the cylinder contains balls that occupancy 30 to 50% of the mill.
- Volume the weight of cabal consists the ball size depends on the size of the feed and the diameter of mill the cylinder and balls are made up of metal and are usually Lined with chrome in pharmaceutical industry some time the cylinder of the ball mill is lined with rubber or porcelain.
Working of Ball Mill
In a ball mill, the material to be ground is placed inside a rotating cylinder along with grinding media (usually steel or ceramic balls). The efficiency of size reduction depends heavily on the rotational speed:
- Low Speed – If the mill rotates too slowly, the balls simply slide or roll over each other without sufficient impact, resulting in minimal size reduction.
- High Speed – If the mill rotates too fast, centrifugal force causes the balls to stick to the cylinder walls and fail to cascade, reducing grinding efficiency.
- Optimal Speed (~2/3 of Critical Speed) – At this speed, the balls are carried upward by the rotation and then cascade down due to gravity. This creates a combination of impact (from falling balls) and attrition (friction between particles), leading to effective grinding.
After grinding for a sufficient time, the material is discharged and passed through a sieve to obtain a powder of the desired particle size.
Advantages of Ball Mill
- It can product very fine powder.
- It can be used for continues operation.
- If sieve are classified classifier to attach to the balls.
- The suitable for both weight and drug grinding process
Disadvantages of Ball Mill
- The ball mill is a very noise.
- Wear occurs from the ball as well as from the cassing which may result contamination.