Types of tab mfg

dear sir
what is requirement of these three types of mfg wet graulations, dry granulation,direct compaction methods.why we choose not one for all?

Generally, tablet manufacturing method is decided by several factors such as type of API and excipients used with respect to their particle size, bulk density, compressibility, crytallanity, compatibility with granulating solvents to be used and most importantly chemical stability during processing (drying at higher temperatures) etc. For example, some of the sensitive antibiotics and vitamins products can not be manufactured by using wet granulation and drying the granules at higher temperature because of their poor stability at high temperatures (thermolabile nature). Potassium clavulenate tablets can not be manufactured using aqueous granulation process as it gets degraded in presence of moisture. Similarly, for Amoxicillin and Amoxicillin products, these are very moisture sensitive and thermolabile.
Therefore, the most suitable method to ensure above aspects is selected for manufacturing the tablets.

One method can not be used for all.
Dry Method is used for heat sensitive and moisture products.
Wet method is used for products not degraded by heat and moisture.
Direct method is used for materials having better compaction properties or req granular type exceptients.