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1. Weighing the building material Here, formulation ingredients are dispensed in proper quantities. The excipients and active ingredient(s) must be in finely divided form, otherwise, the particle size should be reduced.
2. Mixing of building materials The dispensed formulation ingredients are mixed in a powder mixer until a uniform powder mixture is achieved. It is worth noting that half the amount of lubricant is added to the formula at this stage to increase powder flow during slugging and to prevent compacted powder from sticking to the die during pre-compression.
3. Compression of mixed powder in slugs Here, the mixed ingredients are compressed into flat large tablets or pallets. This step is called pre-compression (slugging) and the compacts formed in the process (typically 25 mm in diameter by about 10-15 mm thick) are called slugs. Compaction of mixed powders in slugs can be achieved by slugging technique or roller compaction. The pressure used to form the slug is generally lower than the pressure used for final compaction.
4. Milling and sieving slugs After slugging, the next stage of tableting by dry granulation is usually crushing the slugs into small pieces using a hammer mill or other conventional milling equipment. The milled slugs are screened to produce uniform pellets.
5. Disassemble and mix with lubricant After screening, the remaining lubricant and other extragranular excipients such as disintegrants, glidants, etc., are added to the granules and mixed gently to achieve a uniform mixture.
6. Compression of granules into tablets The mixed granules are compressed into tablets using a single or rotary tablet press fitted with suitable punches and dies.
As with wet granulation, tablets prepared by the dry granulation method can be coated if required.
