Tablet Thickness Adjustment: Optimizing Your Tablet Manufacturing Process

Tablet thickness is one of the three core parameters in tablet manufacturing, alongside tablet weight and hardness. These three parameters are interconnected in press operations, where adjusting two will affect the third. Specifically, tablet thickness measures the vertical height of a tablet from its lowest to highest point. This article covers key aspects of tablet thickness adjustment, including setting thickness for a soft start, determining minimum and maximum thickness values, understanding the impact of thickness on hardness, and calculating theoretical adjustment thickness for Automatic Weight Control (AWC) systems.

Core Principle: Adjust One Parameter at a Time

To maintain consistency, only one core parameter should be adjusted at a time. For instance, if you keep the tablet weight constant and adjust the thickness, the hardness will change accordingly. Up to the maximum density point of the formulation, reducing tablet thickness increases hardness, while increasing thickness decreases hardness.

Importance of a Soft Start

A soft start is crucial for protecting tooling and minimizing stress on the tablet press and its components. This is achieved by setting the initial tablet thickness to be greater than the target thickness. Pre-compression is usually best set first without main compression engaged where tablets are barely formed. ?Additional thickness for main compression can vary from 5% to 100% of the final tablet thickness, depending on the formulation's flowability and bulk density. Fluffy formulations and poorly flowing powders require a larger initial thickness than denser or better-flowing powders. If the first tablets are too soft and fall apart, gradually reduce thickness until sufficient hardness is achieved. Allow the feeder to run briefly between test samples to ensure it fills with enough powder. Once a steady flow is established, reduce the tablet thickness to the final target value.

Minimum and Maximum Tablet Thickness

Tablet presses typically restrict how thin you can set tablet thickness to prevent accidental contact between the upper and lower punch.? Regardless it is never a good practice to run a press dry (without formulation).? Tablet presses typically have a minimum thickness setting to prevent accidental contact between the upper and lower punches, typically ranging from 0.01” (0.25mm) to 0.04” (1mm). This restriction can be modified for special cases, such as micro-tablet production. The maximum thickness achievable depends on factors like the tablet press, tooling type, fill cam, and the compressibility of the formulation.

The proportions of a tablet within these thickness limits significantly impact its swallowability, aesthetics, and packaging requirements. For guidance in selecting the ideal tablet size and shape, contact Natoli Engineering.

Theoretical Adjustment Thickness for AWC Systems

Some AWC systems offer an optional parameter for proportional adjustment of thickness, known as the theoretical "Adjustment Thickness." This value represents the tablet thickness for the same volume as if the tablet were flat-faced. It is calculated as the tablet sideband height plus 2 * (cup volume / die hole surface area).

Troubleshooting Thickness Variation

If tablet thickness varies beyond the target range, consider the following:

· Check for formulation segregation, as particle size distribution may be uneven.

· Inspect compression rollers for bouncing or eccentricity.

· Ensure legacy machines are not operating in an overload condition.

· Verify that the pressure applied does not exceed the elastic limit of the formulation (Natoli Scientific offers USP <1062> services to measure this limit).

· Check that punch overall length variations are within specification.

For further information on press setup and operation, or if you need assistance, contact us at Natoli Engineering. We are here to help you. 636-926-8900.

TDM 8/27/2024