How to Select Tablet Coating Machine

Tablet coating machines are an essential element of pharma manufacturing plants in their oral dosage forms. They give the tablets the final physical and chemical shape before being packed in the packaging material. Coating machines are specifically designed to retain pharma product characteristics, physical shape and transfer product therapeutic effects optimally.

However, it is necessary to select a tablet coating machine realistically that is tailored to individual pharma organization to deliver the required drug properties optimally. Otherwise, tablet products will cause a total loss for the pharmaceutical manufacturing organization.

Before purchasing a coating machine, it is helpful to work with the machine supplier to identify the requirements. It can help you to work on alternative, If these are not available at the machine manufacturer.

What is a Tablet Coating Machine?

A tablet coating machine applies coating material to pharma drug tablets for various therapeutic requirements. The amount of coating material can be controlled depending on the product requirements. The coating machine has multiple sub-systems and components, such as heating and spraying, to aid the coating process. This is in addition to different operation parameters, such as pan speed and spray rate, that determine the final product characteristics, which can be controlled through the central operating panel.

Some essential components of a tablet coating machine include but are not limited to

Coating Pan: a metallic half-ellipsoidal container with a central opening. Tablets are placed in the pan and rotate at a fixed speed. It size depends on the capacity of the coating machine

Spraying Nozzles: They are placed in the pan opening to spray coating liquid inside the pan. Commonly, more than one nozzle sprays liquid to be coated.

Peristaltic Pump: A peristaltic pump is used to deliver the liquid to the spraying nozzles and defines the spray rate of the coating machine

Air Inlet and Exhaust: In a tablet coating machine, hot air enters and then leaves through the exhaust system 9 (for various purposes)

In a typical coating process, tablets (to be coated) are placed in the pan, which rotates at fixed speed. The spray gun continuously sprays the liquid on the tablets in the rotating pan. As the pan rotates, tablets tumble over others, enabling them to receive spraying liquid from all sides. The spray rate depends on the peristaltic pump speed and is adjusted according to the product requirement. 

Hot air flows into the pan through the air inlet. Hot air is used to dry the tablets inside the pan of the sprayed liquid to ensure the protection of the sprayed liquid and the tablets. The air then flows out of the pan from the exhaust, which releases the air.

Quality and production continuously check the product and process during the operation to solve any issues that arise

After all liquid has been sprayed, the spray process is stopped, and the coating pan keeps rotating to cool down the tablets to ensure easy handling.

After cooling, the coating pan is stopped, and tablets are discharged for further processing.

What can go wrong if the correct coating machine is not selected

Let's discuss the disadvantages of choosing an incorrect coating machine.

Improper Tablet Characteristics

Selecting the suitable table coating machine is critical for the success of coating process. Otherwise, the final coated tablets will lack the necessary characteristics and result in a defective product.

Tablet defects, such as roughness, colour variation, and twining, are expected to result from improper machine selection. These tablet defects require re-processing, wasting critical resources and time. 

In some cases, re-processing is impossible, and the pharma manufacturer is forced to discard or destroy the product.

Limitation in customizing spray options

The spraying function is an integral part of the coating machine, and drives the success of the entire coating process and influences the liquid being sprayed.

Improper machine selection will affect the sprayed liquid's droplet size and size distribution as it reaches the tablet bed from the nozzle. When spraying the liquid, it will also affect the area covered by the nozzles.

Other factors that could affect include

● Inadequate spray rate affecting the ability of the coating machine to deliver liquid to each tablet in the pan

● Difficult for the nozzle to spray and reach the tablet bed.

● Failure to set and adjust the atomizing air pressure, which is critical in liquid spraying from the nozzle

Inadequate Tablet Movement

Tablet movement in the coating pan plays a significant role in the final characteristics of tablets. When they move or tumble inside a pan, they get the required quantity of sprayed liquid in an entire lot equally.

An improper coating machine will disrupt the tablet's movement inside the pan, resulting in several tablet problems, such as

● Mechanical stress on tablets due to volatile movement, causing them to break.

● Non – uniform distribution of coating material throughout the pan

● Failure to provide spraying liquid exposure to each tablet

● Failure of drying profile for every tablet

Inability to apply robust operational parameters

Operational parameters such as temperature, pressure and speed are pivotal in the success of the coating process. They allow pharma manufacturers to apply various machine instances during coating process. Especially during product development stage or working on problem solving issues

Improper coating machines will restrict the manufacturer's ability to apply various operational parameters, which will, in turn, limit the machine's benefits. The coating machine will have few options for customizing operational parameters, such as temperature, speed and spray rate, limiting the manufacturer's ability to diversify its product portfolio. It will also affect their ability to tackle and solve process-related problems during product life cycle stages.

Factors to consider when selecting a tablet coating machine

Some factors to consider when selecting a tablet coating machine include the following

Capacity

Total capacity is the most common factor when selecting any pharma equipment. It gives an overview of about how much a coating machine will produce tablets in a single run.

There are different methods to indicate the capacity of a tablet coating machine, and the most common is in kilograms - kg, which is the function of brimful volume and tablet bulk density.

When selecting a coating machine for your applications, calculate the required quantity of tablets, by considering your share in the market and visualize where you stand shortly. It is handy to perform market forecast studies with the help of your supply chain department.

Spray System

The spray system in the coating machine consists of a spray gun and a peristaltic pump.

Spray guns spray liquid on the tablet bed in a coating pan. In it, compressed air combines with the liquid, which

turns the flowing liquid into a stream of uniform drops. 

Select a spray gun that offers smooth liquid flow through its orifice and prevents problems such as blockage and drop dispersion. Because any blockage, drop dispersion, and any other issue will affect the spray pattern, disturbing the entire coating process.  The number of spray guns in a machine can also vary, depending on the coating speed and quantity of tablets in a pan.

A persistent pump is used to pump liquid through the nozzles via tubes. It allows the adjustment of spray rates according to product requirements.

The pump must match the machine's capacity requirements. Additionally, there are different techniques to control the pump operation. In some cases, it is manually controlled through the local panel on the pump. In another case, it is automatically controlled by the coating machine, which matches the coating process.

Clean In Place - CIP 

CIP is an automated cleaning system in which a machine is cleaned without moving it at other places, and the same option can also be provided with the coating machine.

This system provides all the utilities, such as water and compressed air, in the coating pan. When activated, all utilities automatically or manually clean all critical parts. Additional components, such as pumps and piping, are required for effective implementing CIP system. 

CIP systems come at an additional cost, which increases the base price. Consider your options, such as production rate and available budget, before selecting CIP. 

Available Area

The tablet coating machine consists of dedicated sub-components that require dedicated areas in both production and technical areas.

An area is required for coater placement and control panel in production. Space is also required for additional components, such as piping and peristaltic pumps, which are critical coating machine parts.

In the technical area, space is required for sub-components such as piping, AHU and CIP system. These components are bulkier and require considerable area.

When selecting a coating, determine if sufficient space is available in production and technical areas. It will help you execute the coating process safely and efficiently for your pharma product. 

Available Utilities

A coating machine requires several utilities to activate components and ensure efficient coating operation. Some critical utilities include but are not limited to 

● Compressed air for atomizing air in spray nozzles and activating various pneumatic components such as actuators and valves

● Purified water for the CIP system

● Hot air for heating the coating pan, depending upon the product requirements

About the Author:

Muhammad Asim Niazi

Muhammad Asim Niazi has a vast experience of about 11 years in a Pharmaceutical company. During his tenure he worked in their different departments and had been part of many initiatives within the company. He now uses his experience and skill to write interested content for audiences at PharmaSources.com.