A ball mill is a type of grinder that consists of a hollow cylindrical shell rotating about its axis. The shell is filled with balls that grind the materials through impact and attrition. Ball mills are used to grind materials in processes like mineral dressing, paints, pyrotechnics, and selective laser sintering. The ball mill works on the principle of impact, where size reduction is done by the balls dropping from near the top of the shell onto the material being ground. Factors like feed rate, properties of the material, ball size, and rotation speed affect the size of the final product from the ball mill.

2. Topic
BALL MILL
Presented by:-
Ali Haider 13-NTU-1005
Adil Naeem 13-NTU-1002
Hameed Ullah Bhatti 13-NTU-1022
Teacher:- Sir Muzammil
Mehmood SB.
Department of Polymer Engineering.

3.  A ball mill is a type of grinder used to grind
and blend materials for use in mineral
dressing processes, paints, pyrotechnics,
ceramics and selective laser sintering etc.
Introduction to Ball Mill

4.  Ball mill consist of a hollow cylindrical shell rotating about its axis.
 It is partially filled with balls made up of Steel, Stainless steel or rubber.
 Inner surface of the shell is lined with abrasion resistant materials such
as Manganese, Steel or rubber.
 Length of the mill is approximately equal to its diameter
 Balls occupy about 30-50% of the volume. Dia of the ball 12 mm-125
mm.
 Shell is rotated through a drive gear (60-100 rpm) and large mills, shell
might be in 3m in dia and 4.25 m in length.
 Operation may be batch or continuous, wet or dry…in a continuosly
operated ball mill outlet is normally covered with coarse screen to
prevent the escape of the balls..
Construction

5. Wet or Dry ball mill consist of:-
1. Feeding part
2. Discharging part
3. Turning and driving part
( gear, motor etc.)
4. Rotating balls
Ball Mill

6. Working Principle
 Ball mill works on the principle of
impact.
 Size reduction is done by impact as the
balls drop from near the top of the
cylinder..

7. Product Size
0.075-0.4mm
Feed Size
≤25mm

8. Factors influencing the size of the
product
 Feed rate:-With a high feed rate, less size reduction is effected since in this
case the material is in the mill for a shorter time.
 Properties of the feed material:- With a hard material, a smaller size
reduction is achieved.
 Level of the material in the mill:- A low level of material in the mill results
into a reduction in the power consumption. If the level of material is
raised power is wasted by the production of under size material.
 Weight of the balls:- With a heavy discharge of balls, we get a fine
product. We can increase the weight of the charge by increasing the
number of balls or by using a ball material of high density
 Speed & rotation of Ball mill:- low speeds, the balls simply roll over one
another and little grinding is obtained while at very high speeds the balls
are carried along the walls of the shell and the mill is said to be
centrifuging.

9. Critical Speed of a Ball Mill
 The point where the mill becomes a centrifuge is called the "Critical
Speed“.
 Ball mills usually operate at 65% to 75% of the critical speed.
Nc = Critical Speed
R = Radii of mill
r = Radii of ball
g = Acceleration due to gravity

10. Problam for Understanding

11. Problam # 02

12. Advantages of Ball Mill
 The cost of installation is low.
 The cost of production is low.
 It is suitable for materials of all degree of
hardness.
 The grinding medium is cheap.
 Suitable for both batch and continuous
operations.
 Used for the grinding of explosive materials.

13. Disadvantages of Ball Mill
 Rotational ball loading difficulty
 Mill efficiency is low
 The mill feed size range is wide
 Not easy to get thinner end product

14. Applications
 Metallic powders
 Carbon and coal
 Phosphate rock
 Gypsum grinding
 Limestone milling
 Cement processing
 Fertilizers
 Silicate products
 Dressing production
 Granite

15. Video