Learn the working and principle of tablet coating machine used for different types of coatings on tablets.

A tablet coating machine is an equipment that coats the external surface of a tablet using a thin film of coating material. Working principle 

of tablet coating machine is relatively simple where the application of coating material is done on a moving bed of tablets and removing 

rapidly the solvent using a current of hot air.

For the tablets to be coated they are placed in a closed drum which is made to rotate continuously in an orbital manner under the influence 

of a streamlined plate. During the orbital motion of the tablets, the coating medium sprays automatically in a rational manner in order to 

avoid excess coating on the tablets.

Angled baffles are also fitted into the drum and also air flow is provided which acts as a means to mix the tablets. The baffles cause the tablets 

to be lifted and turned from the sides of the drum and onto the center exposing all the sides of the tablets to the sprayed coating. Whilst the 

spraying is going on, hot air is introduced from the 50% perforated tablet bed which causes rapid drying of the coating medium. The hot air 

comes from inlet fan and is regulated in terms of temperature and volume.

The regulation of the air allows for maintenance of the drum pressure relative to that of the outside room for the purpose of providing a completely 

isolated process atmosphere. The regulation of the air also provides controlled drying and tablet extraction rates. It also allows for an evenly 

spread medium on the tablets giving the tablets a smooth solid surface. Tablet coating machine may include coating pans, spraying guns, exhaust 

and heating pipes. The process may include film coating or sugar coating.

The process is also done in batches which include several phases such as batch identification and selection of the recipe to be used. Loading of 

the required raw materials, warming, spraying of the coating which is coupled with rotation of the tablets, drying, cooling and lastly unloading 

of the coated tablets.

One would wonder what the importance of coating tablets is. Coating machine allows the drug release to be regulated. This ensures that the 

drug is supplied to the body in safe amounts that the body can handle and also optimizes their effect on the body. The coating also increases 

the stability of the tablets which prevents oxidative degeneration caused by factors that may react with the drug such as light and air.

Another advantageous factor of tablet coating is that the tablets can easily be swallowed as they overcome the poor taste the tablets may have. 

The coating may be flavored or tasteless. This is because some tablets taste bitter or may not have a very pleasant taste.

The coating also gives the tablets its signature color which allows for easy identification and also compatibility with other drugs. The coating also 

protects the drug from a gastric environment allowing it to reach the area in which it is intended for absorption.

There are parameters which are considered in coating machines. These parameters include air capacity, coating composition, the surface area of 

the tablet and lastly the efficiency of the equipment.