The knife mill uses sharp knives attached to a rotating impeller to cut aggregate materials into fine particles through shearing action. It has a feed hopper, casing, rotor, stationary knives, moving knives, and screening plate. Materials are fed into the hopper and the rotation of the rotor forces it between the stationary and moving knives where it is cut into small pieces. The screen retains the cut material until it reaches the desired size, then collects the product. Knife mills can produce ultra-fine particles and have applications in combine harvesters and lawn mowers.

2. AHMAD QAYYUM
M13-CE-04

3. KNIFE MILL

4. TABLE OF CONTENTS
Definition
Principle
Basic parts
Construction & Working
Applications
Advantages
Disadvantages

5. DEFINITION
A mill in which knifes are attached on the
impeller that crushes the aggregate material
and converts it into the fine range particles is
called Knife mill.

6. PRINCIPLE
The size reduction of the materials is done by
cutting with the help of sharp knifes which
provides shearing action rather than impact
or attrition and converts the feed into fine size
particles which is collected from discharge
chute.

7. WHY WE USE KNIFE MILL ?
Sometimes, the feed stocks are too tenacious or
too resilient to be broken by compression , impact
or attrition. And sometimes, feed must be reduced
to particles of fixed dimensions. So, these
requirements are met by knife cutter that cut,
chop and tear the feed into the product with the
desire characteristics.

8. BASIC PARTS
 Feed hopper
 Casing
 Rotor / Impeller
 Stationary knives
 Moving knives
 Screening plate

10. CONSTRUCTION
 There are two types of knifes, stationary which is fixed with casing
and other is rotating which is attached to the rotor.
 The upper part of casing also contains a hopper inlet, whereas
the lower part has screen of desired aperture size.
 The rotary knife cutter has 2 to 12 knives on its periphery that
rotates with 200 to 900 rpm and the cylindrical casing has several
knives.

11. WORKING
 The material to be cut is put into the hopper.
 The feed size should be less than 1 inch and should not exceed
the length of cutting knifes.
 Due to the rotation of rotor, feed comes very close between the
stationary and moving knives. It cuts down the material into the
small pieces.
 Screen retains the material in the mill until the desired product is
formed. The product is collected which comes out of the sieve.

12. APPLICATIONS
Combine Harvester/ Thresher Lawn Mower ( Grass cutting machine )

13. ADVANTAGES
 Knife mill produces ultrafine particles and yield narrow size
distribution.
 It is easy to install.
 The speed can rapidly changed by rotating the knives.
 Moreover, maintenance is easy and inexpensive.

14. DISADVANTAGES
 It is not easy to clean.
 Speed should be controlled.
 Wet preparation of the materials can not be sieved due to
clogging of the materials take place.
 Feed thickness should not be more than the thickness of
cutting knifes.