During production of tablets, defects arise with finished tablets, which may be due to fault in the formulation or in the tableting equipment and sometimes due to both of these reasons. Table 5.2 details few common production problems that arise during manufacturing.

 

Table 5.2 Production Problems with Tablet Quality

Tablet Problems	Possible Causes	Corrective Action
1. Non-uniform tablet weight	Feeders starved or chokedGranulation lost or gained after proper filling of dieDies not fillingLower punch pulled down before die is filledWide variation in thickness of lower punch	Excessive recirculation of granulationExcessive vacuum pressure, or nozzle improperly locatedCheck speed or shape of feeder paddleInadequate recirculation of granulationCheck that head thickness of lower punches is within ±0.10 inch of TSM specification
2. Non-uniform tablet thickness	Non-uniform tablet weightNon-uniform punch lengths	Same as aboveCheck that working length is within ±0.001 inch of TSM specification
3. Non-uniform tablet density (friability)	Non-uniform tablet weight and thicknessLow moisture content	Same as aboveAdd moisture to aid bonding
4. Dirt in product (black specks)	Dust, dirt, or press lubrication in the granulation	Clean press more frequentlyUse proper punch dust cups
5. Capping and lamination	Air entrapmentRapid expansion of tablet upon ejectionWeak granulationExcessive dry granulationPunch cavity too deep	Reduce press speedReduce quantity of fine particles in the granulationEnsure that punch to die clearance is correctTaper diesIncrease quantity of binder; use strong binderIncrease level of lubricantUse punches with less concave depth
6. Picking and sticking	Excessive moisturePoor embossing design	Check moisture content of granulationCheck room humidityRedesign embossing as per TSM guidelines
7. Mottled or marked tablets	Contamination of granulation usually by grease or oil or chutes or feed hoppersHigh moisture content of granulationHigh drying rate	Clean and reset components correctlyRe-dry granulationOptimize drying rate
8. Chipping or splitting	Poor surface finish on punch tips, worn punches, and diesPoor tooling design(e.g.: sharp embossing or bisect line)	Polish punch tips, replace punches and dies
9. Splitting of layered tablets	Excessive pressureExcessive lubrication of granules	Decrease pressureReduce the amount of lubricant
10. Indistinct break line or embossing	Incorrect embossing designWorn punch tipsExcessively coarse granulationInadequate binderPicking	Redesign embossing as per TSM guidelinesReplace punchReduce particle sizeIncrease binder strengthCompress granulation at lower pressure
11. Double impression of embossing	Rotation or jerk of the punches during compression	Adjust anti-turning deviceUse keyed punches

Some more problems that give rise to defective tablet quality are discussed below:

Binding in the die: During binding in the die, the ejection of tablet is difficult and is accompanied by a characteristic noise. The edges of the tablet become rough. This defect occurs due to poor lubrication of granules, under dried granules and worn out dies.

Capping and lamination of tablets: In capping or splitting, the upper or lower surface of the tablet is partially or completely separated out from the main body of the tablet. In lamination, the tablet separates out into two or more layers.

Causes: Capping occurs due to the following reasons:

1. Entrapment of air in the granules during compression
2. Presence of excess of fine powder in granules
3. Use of too soft granules leads to capping
4. Wear and tear of punches and dies
5. Incorrect setting of dies and punches

Picking: The surface of tablet material is removed by punches and adheres to the surface of the punches.

Causes: Picking occurs due to the following reasons:

1. Presence of scratches on punches
2. Use of wet granules

Sticking: Granules adhere to the die and lower punches cannot move freely.

Causes: Sticking occurs due to the following reasons:

1. Use of damp granules
2. Worn out dies or punches

Mottling: It occurs in colored tablets. Due to the unequal distribution of color in the tablet, different shades appear on the tablet.

Causes: Mottling occurs due to the following reasons:

1. Difference in color used, drug and the excipient
2. Migration of dyes during drying

Weight variation: This problem arises during filling of granules into die cavity.

Causes: Weight variation occurs due to the following reasons:

1. Poor flow of granules into die cavity
2. Presence of fines in granules
3. Non-uniform separation of granules
4. Improper mixing of lubricants

Hardness variation: Hardness of the tablets varies due to variation in weight of material, pressure applied on upper punches, improper space between upper and lower punches and excessive use of fatty lubricants like magnesium stearate.

Double impression: This occurs in tablets when a monogram is printed during compression.

Cause: The defect may be due to loosening of the punches in the socket grooves.