Classification & Types of Tablet Coating Machine (Learn How to Choose the Right Tablet Coater)

Today, I want to show you how to choose a new tablet coating machine.

I know it is one of the most difficult processes, especially for newbies in the pharmaceutical industry.

I will make the process simple by giving it a completely new approach.

That is, to classify all the existing tablet coating equipment, depending on the working principle and coating process/technique.

This way, you will get to know the type of tablet coater machine that is suitable for your unique applications.

Types of Tablet Coating Equipment (Main Focus Being the Working Principle)

Depending on the working principle, you may classify all the existing tablet coating machines as:

• Standard Coating Pan
• Perforated Coating Pan
• Fluidized Bed Coater

As you will learn later in this article, every type of tablet coating machine tends to have a unique working principle.

Basically, this implies that the structural design will also be different.

I am sure with this knowledge, you can choose a suitable tablet coater, depending on your unique specifications.

Let’s evaluate each of these machines:

Standard Coating Pan

Standard coating pan, which is also known as the conventional pan system is a popular accessory in most pharmaceutical industries.

Basically, the design of this type of tablet coating machine is such that there is a circular metal pan whose diameter may range from 6 to 80 inches (15 to 200 cm). The pan is slightly tilted to an angle of about 45°C to the bench top.

The standard coating pan has an electric motor that rotates the circular metal pan horizontally to its axis.

It is the motion of this pan that causes a batch of tablets to tumble.

Again the conventional pan system has an inlet air supply.

This inlet port supplies heated air.

NOTE: You must ensure that the air temperature does not initiate any chemical reaction on the tablets from the tableting machines.

At times, very high temperature may decompose or degrade essential chemical constituents of the tablets.

Remember, it is this hot air that dries the coating solution.

Again, during the process, all exhaust air will exit the system through the front section of the standard coating pan. This air leaves by means of the duct system.

This machine uses spraying or ladling mechanism to supply the coating solution.

That is, as the circular metal pan rotates, the standard coating pan system will begin to supply the coating solution.

Why Do I Recommend Spraying System?

For faster coating and an even distribution of the coating solution, the spraying gun will atomize the solution.

That is, the coating liquid will be “split” into very fine particles.

Furthermore, with this will reduce the drying time significantly and allows for continuous coating.

In short, the spraying mechanism ensures the efficiency of the tablet coating process.

Even though this type of tablet coating machine is popular among many pharmaceutical industries, it has some drawbacks.

Drawbacks of Conventional Pan Systems

When you choose this type of pill coating machine, some of the main challenges include:

• Improper balance of inlet and exhaust air that may further complicate the process. In fact, this can be risky whenever you’re using inorganic solvents.

Therefore, you must know the chemical composition of both the tablets and coating solution.

• Since a greater percentage of the drying takes place on the surface, the process may not be efficient.
• Tablets may not mix properly and this may cause uneven coating.

This does not imply that you should ignore the standard coating pan.

For a fact, by adopting spraying system, you can solve improper mixing and uneven coating. However, to improve the drying efficiency, you must modify the conventional pan system

Here’s how to go about this process:

Improving the Drying Efficiency of Standard Coating

With this type of tablet coating machine, you can improve drying efficiency using:

• Immersion tube system
• Baffled pan and diffuser
• Immersion sword

Also, you should note that this may form the basis for classifying tablet coating machines.

Let me show you how to improve the drying efficiency of standard coating pan.

a) Immersion Tube System

Here, the tablet coating machine manufacturer includes a tube that you will immerse in the tablet bed.

This tube has a spray nozzle that delivers both the hot air and coating solution.

As you can see, the immersion tube system delivers heated air and coating solution simultaneously.

It is basically a long tube with a spray nozzle at its tip.

The design is such that the drying air (heated air) flows upwards and leaves the system by conventional duct.

By incorporating an immersion tube system in standard coating pan, you will increase the drying efficiency.

It is a technique that is handy for both sugar coating and film coating machines.

Apart from this, you can opt for:

b)  Baffled Pan and Diffuser

A baffled pan and diffuser, which is also called the pellegrini, also improves the drying efficiency of standard coating pan. In this process, the tablet coater can distribute drying air uniformly on the coated tablets.

However, the standard coating pan with baffled pan and diffuser are only suitable for a  sugar coating process.

This is due to the limited drying capability.

Again, in case the two are not available, you can try:

c) Immersion Sword System

This is basically a perforated metal sword that you can immerse in the tablet bed.

The working principle is such that:

During the drying process, you will introduce drying air which flows through perforated metal sword then upwards through the bed.

This way, you can improve the drying efficiency in standard coating pan systems.

Clearly, you can see we have 3 different types of standard coating pan machines.

The variation is mainly due to the process of drying the coated tablets.

Apart from the conventional coating system, another type of tablet coating machine is the:

Perforated Coating Pan

Perforated coating pan is also popular among many pharmaceutical companies.

In most cases, this type of tablet coating equipment has either a full or partial perforated drum.

Like the standard coating pan, the drum of this tablet coater rotates on a horizontal axis.

You can see this in the video below:

As you can see, the coating drum is an enclosed housing with various spray nozzles.

It is these spray nozzles that atomize the coating solution.

However, unlike most conventional pan machines, perforated pan coaters have an efficient drying system.

Besides, they are high capacity tablet coating machines.

Again, whenever you’re buying this type of tablet coating systems, you can choose any of the following:

• Accela-cota system
• Dria coater pan
• Hi coater system
• Glatt coater

Don’t worry I will highlight the key features of these machines shortly.

This information will help you to choose the right tablet coater.

a)  Accela-cota System

First, I want you to review the image below. It illustrates important aspects of an accela-cota tablet coating machine.

As you can see, there are a number of processes that take place within the drum.

• Baffles ensure the tablets mix freely within the drum as it rotates
• Spray gun atomizes the coating solution and directs it to the tablets
• Dry inlet air flows from the upper section of the drum, passing in between the tablets. It leaves the drum through the perforations.

This increases the overall efficiency of this type of tablet coating machine.

b) Dria Coater Pan

When you look at the figure below, the difference between accela-cota system and dria coater pan is quite clear.

A dria coater pan has hollow perforated ribs, which are locate on the inside periphery tablet coating drum.

Therefore, as the drum rotates, the spray nozzle atomizes coating solution and directs it to the tablets from the top section.

Of course, this is the same scenario like for the accela-cota machines.

However, the drying air enters the coating drum from below the tablets and flows upwards, then exits the system through the back of tablet coating pan.

Remember, this is not the case in the accela-cota.

Basically, in dria coater, the drying air fluidizes the tablets. You can see the tablets suspended in air.

c) Hi-coater System

Although the design of hi-coater systems may be different, the working principle is similar to that of the accela-cota.

The machine directs both the coating solution and drying air downwards.

The drying air, then leaves the coating system through the perforations below the coating drum.

d) Glatt Coater

The design of a Glatt coating pan machine resembles that of the accela-cota.

This type of tablet coating machine is known for:

• High spray rates
• Extremely short processing time

Its design is such that you can direct the drying air from inside the tablet coating drum.

Normally, the air passes through the tablet bed and leaves via exhaust duct.

Its unique design minimizes turbulence that may occur around the spray nozzle.

This ensures an even distribution of the coating solution on the tablets.

Moreover, its drum has unique geometrical shapes with baffles on the periphery.

This ensures an effective mixing of tablets while protecting the products from damage at the same time.

So far, it is one of those tablet coating machines that ensures consistent and accurate coating.

As you can see, the working principle of all these tablet coating machines is the same.

For instance, in all the perforated pan systems, the spray nozzle atomizes coating fluid.

Also, the spraying nozzle is in the tablet coating drum.

The only difference is how the machine supplies and removes the drying air.

Now, with this information, am sure you can easily choose a suitable perforated pan system for your tablet manufacturing process.

Again, in case you don’t need these two, there is another tablet coating machine available in the market.

This is the:

Fluidized Bed Coater

A few weeks ago, I did an article on different types of spray systems in fluid bed equipment.

You should spare some time to read this article.

It will give you more insights on this subject.

Well, the working principle of fluidized bed or air suspension system is basically similar to that of the other spraying systems.

Normally, the key aspects about these coating machines are:

• It has a vertical cylinder
• A column of drying air flows upwards suspending all the tablets. This causes the tablets to move upwards, outwards and then downwards, a process we refer to as fluidization.
• Spray nozzle atomizes and introduces the coating fluid into a fluidized bed. The nozzle’s position can either be at the top or bottom of the fluidized bed coater.

This process will continue until you achieve the right coating on your tablets.

Basically, you are at liberty to choose any of the three types of tablet coating machines.

But, before I proceed to the next section, you should remember that the degree of coating fluid atomization in any of these machines will depend on:

• Type, design and size of the nozzle
• Fluid pressure
• Orifice size

With these in mind, we can have a quick overview of the next classification criteria:

Types of Tablet Coating Machines (Focusing on Coating Process)

Well, you can choose a tablet coater system depending on the following key processes:

Sugar coating: It is the process of covering tablets with a sugar layer that can either be colored or uncolored.

This coating is soluble, masks bad taste, acts as a protective layer and enhances appearance.

Film coating: Most drug manufacturers are switching to film coating.

It is basically the process of adding a very thin layer to tablets.

Film coating process is easy to automate, involves few procedures and increases the overall weight of tablets by only 3%.

This is not the case for sugar coating where a tablet may weight more that 30%.

Enteric coating: It mainly protects tablet core from the acidic environment in the stomach. With enteric coating, the tablet will not disintegrate.

As you can see, these are basically tablet making processes.

For the scope of this article, I may not be able to discuss each of these tablet coating processes.

In case you want to learn more on this subject, I have several links at the end of this article.

Conclusion

Whenever you’re shopping for any type of tablet coating machine, it is important to know the working principle, design, structure, air capacity, coating composition and efficiency.

By doing so, you will obviously optimize all operations in your tablet coating process.

I know this process may be overwhelming at times.

This is why SaintyCo team offers free consultation on pharmaceutical equipment.

Again, if you want to learn more about tablet coating equipment, below are useful sources of information:

• Types of Tablet Coating Processes – By Dr. M. Gohel
• Tablet Coating – By Kiranmai
• Film Coating Machine Buying Guide – By SaintyCo.
• Techniques of Tablet Coating – By A. Basu , A. De, and S. Dey
• Types of Tablet Coating Machines – By SaintyCo