The Tablet Coater Process

Tablets remain the dominant oral dosage form because they combine accurate dosing, very high stability and acceptance, and cost-efficient, high-throughput manufacturing. Tablet coating or film coating further expands this platform by adding functional performance (e.g., enteric protection, modified release), stability (light/moisture barrier), and patient-centric attributes (taste masking, smoother swallowing, visual identification).

Spraying, Mixing and Drying in Perfect Balance
 

Tablet coating is one of the most critical and demanding process steps in pharmaceutical tablet production. The coating process must deliver a uniform film layer while protecting the tablet cores from excessive mechanical stress, minimizing material loss and ensuring reliable, reproducible results from batch to batch.

L.B. Bohle coating systems are designed to optimize the three core operations of tablet coating: spraying, mixing and drying.  

Each step must be precisely coordinated with the others to achieve high coating uniformity, efficient processing and excellent product quality. 

Efficient spraying begins with optimal exposure of the moving tablet bed. The BTC Tablet Coater's optimized drum geometry creates a large spray area, allowing the coating suspension to be applied evenly and efficiently.

Several factors influence spraying performance, including coating suspension, nozzle type, number of nozzles, and nozzle spacing. The BTC is designed to support high spray throughput while maintaining a smooth, controlled spray pattern. This improves coating efficiency and contributes to uniform film applications across the entire batch. 

Uniform and gentle movement of the tablet cores is essential for high-quality coating. The tablets must consistently pass through the spray zone without being exposed to excessive mechanical stress, as this could lead to chipping, breakage, or other defects.

L.B. Bohle uses an extended coating drum with a length-to-diameter ratio greater than one and integrated mixing spirals. This design ensures the tablet bed moves continuously and gently throughout the process. Homogeneous mixing is quickly achieved and maintained throughout the entire coating cycle.

The flat tablet bed reduces pressure within the product bed, and the controlled guidance of the mixing spirals prevents the tablets from accelerating too quickly. Consequently, the BTC facilitates gentle handling of tablets, reduces the risk of breakage, and helps prevent twinning. 

Drying is critical to both coating quality and process efficiency. The goal is to introduce energy directly into the tablet bed to ensure effective mass transfer without unnecessarily heating the coater housing or peripheral components.

The BTC Tablet Coater´s optimized air guidance system smoothly and efficiently directs process air into the tablet bed. This allows for the rapid drying of the sprayed suspension while maintaining stable process conditions. Since the spray nozzles are not directly exposed to the supply air stream, they stay cool during spraying, which helps reduce the effects of spray drying.

Controlled airflow and a smooth spray pattern contribute to excellent coating uniformity of  97% or better. At the same time, coating suspension loss is minimized to support efficient material use and high process profitability.