Tablet weight variation

The rate of tlie compaction process is another variable that should be considered throughout development, including scale-up. Typically, the development of a tablet formulation takes place on tablet presses that are relatively slow. The tableting rate is important to consider for several reasons. Blend flow is important to ensure bulk blend transfer into the tablet press (hopper) and consistent die fiU. Variation or difficulty in the bulk flow and die fill can contribute to tablet weight variation. As the compaction rate increases, the blended material must be able to... 

When manufacturing a tablet formulation by direct compression, the particle size and size distribution of excipients have a significant impact on blending homogeneity, powder segregation, and flowability. This can result in unacceptable content uniformity and high tablet weight variation. In such situations, control of excipients can be critical to product quality. 

Press Speed (Tablets/h) Compression Force (kN) Tablet Hardness (N) Tablet Weight Variation (%RSD) Mean Tablet Friability at 4 rpm (%) Mean Tablet Friability at 15 rpm (%)... 

First, the die is filled when it passes beneath a stationary feed frame and the lower punch is in the filling position. Tablet weight variation is dependent on uniform powder filling into the die cavity. Since the residence time of the die under the feed frame is very short, the formulation blend must flow easily and reproducibly. 

The most frequent problems occurring during the manufacture of tablets are high tablet weight variation, capping and lamination [200], and further picking and stick-... 

Frequently the maximum machine speed may depend on die fill characteristics due to excess tablet weight variation at high machine speeds. However, because the compression characteristics of most pharmaceutical products exhibit viscoelastic properties, the press speed may also have a major effect on the compressibility of the material. For this reason, the zability to compress a tablet adequately is often the overriding factor to consider in tablet compression. 

Lower Punch Brakes. Most rotary tablet presses are equipped with lower-punch brakes that are Teflon tipped and spring loaded to apply constant pressure to the lower punches. Alternatively, some manufacturers apply pressure to a friction belt that provides resistance on the lower punches. The lower-punch brakes act as a retention system for holding the lower punches in place during press setup. More importantly, these systems help to minimize lower-punch chatter at high press speeds thus minimizing tablet weight variation. Some press manufacturers use the lower punch seals to retain the lower punches. 

There are many reasons why it is imperative to control tablet weight variation ... 

A non-uniform feed density is not a primary concern. Since tablet presses operate as volumetric feeders, variation of the feed density into the press feed frame can result in tablet weight variation. A funnel flow bin will typically have a more non-uniform feed density than a mass flow bin, since the blend in the funnel flow bin will be subjected to different consolidation pressures depending upon where in the bin it is discharged from. For instance, the blend located at the bottom of the bin at the hopper walls, which is outside the flow channel, may be more consolidated and have a higher density than the blend within the flow channel. 

Curved surfaces, debossing, and scoring are factors that affect the spectrum of a tablet as positioning is varied, but the spectral effects of such factors can be reduced by the methods just discussed. Natural variations in tablet mass and hardness will affect a tablet s spectrum, primarily through spectral baseline shifting. Some work by Baxter [126] involved a unique method of normalizing tablet weight variations. 

---