Hammer Mill

Hammer Mill: Uses, Types, Operating Principle:

Hammer Mill: Hammer mill is one of the oldest and highly used grinding mills that consist of a series of hammers. It is also hinged on a central shaft and a rigid metal is used for enclosing it.

It is used to crush the materials which are done in two stages, i.e., by size reduction that mainly occurred by dynamic impact and by sizing that occurs with the help of attrition and shear in the second zone.

The hammer is repeated again and again and when the material collides with the walls of the grinding chamber the material gets crushed. After that, the coarse material will be retained by a screen that is fitted at the bottom of the hammer mill. However, it allows the properly sized materials to pass and that is used as the finished product.

Classifications of hammer mills:

Based on the director of the motor the hammer mills are classified into the following types:

  • Reversible hammer mill
  • Non-reversible hammer mill

Although the mills are classified into the above two different types their working and grinding actions of both these types of mill are almost similar. However, their construction differs in various respects.


Pharmaceutical uses of Hammer Mill:

There are various applications of hammer mill in the pharmaceutical industry and some of the essential ones are given as follows:

  • Processing wet or dry granulations and dispersing the mixture of the powder
  • Milling any kind of pharmaceutical raw materials, herbal medicines, and sugar
  • Powdering of leaves, barks as well as roots of medicinal plants 
  • Milling of Active Pharmaceutical Ingredient (API), excipients, etc.

Advantages of Hammer mill:

Hammer mill comes up with several advantages and some of the advantages are listed as follows:

  • It helps in producing a particular top size and you do not need any kind of closed-circuit crushing system.
  • It also helps in producing numerous size distributions that have a number of minimum fine dues for self-classification.
  • No matter whether you use it for primary or secondary or tertiary grinding it always comes up with a high reduction ratio and high capacity.
  • It does not require too much energy for grinding.
  • It comes up with blunt hammers and as such, it can fracture the brittle materials finely.
  • It is possible to grind any type of material.
  • It is easy to install and operate and it can produce continuous operation
  • It occupies less space
  • It is easy to maintain
  • It is also easy to clean
  • It is not so costly and you will get it at a cost-effective rate
  • It is possible to construct locally as it is easy to use 

Disadvantages of Hammer mill:

Although a hammer mill comes up with a lot of advantages still it is not without any kind of disadvantages. Some of the major disadvantages of hammer mills are given as follows:

  • It is not so useful when it comes to grid very hard and abrasive material because of excessive wear. 
  • It is not so useful for low-melting sticky materials or plastic-like materials since heat is generated in the head of this mill because of mill fouling.
  • If you cannot control the feed rate then the mill can be choked due to which the material can be damaged.
  • It consists of some kind of foreign materials such as stone or metals because of which the garbling process is inadequate. 
  • While grinding in this mill there is a huge possibility of clogging the screen.  


Thus, with the help of this type of mill, it becomes possible to reduce the bulk material into smaller pieces. This machine has been used for nearly a century but still, it is an essential part of grinding.

The mill either crushes or shreds the bulky material and its application is found in various industries that include pharmaceutical, mining, waste management, lumber, etc. Nowadays, you will get the modern type of hammer mill in the market that comes up with various rotating speeds.

With the help of this type of modern mill, it becomes possible to shatter any kind of materials into small pieces, and hence it is highly useful in the pharmaceutical industry. Once the materials are processed thoroughly they can be easily tumbled with the help of screens that are fitted in the mill.