1.Capping:
In this there is partial or complete removal of top or bottom portion of tablet.
Reasons:
Excessive fine.
Defective punch die.
High speed of machine.
Granules too dried.
Defect can be removed:
Setting the die and punch properly.
Reduce % of fine.
Punches should be polished.
Maintain the desire moisture in granules.
Maintain the speed at optimum.
Regulate the pressure of punches.
2. Picking and sticking:
The material is removed or picked up by upper punch from the upper surface of the tablet.In the sticking he material stick to the wall of the die cavity.
Reasons:
Use of worn out die and punch.
Use of small quantity of lubricants.
Presence of excess moisture in the granules.
Scratches on the surface of the face of the punches.
Defect in formulation.
Defect can be removed:
Using new set of die.
Adding proper quantity of lubricants in granules.
Dry granules.
3.Mottling:
An unequal distribution of colour on the surface of a coloured tablet.
Reasons:
Migration of dye in the granules during drying.
Use of different coloration of medicaments and Excipients.
Defect can be avoided:
Drying the granules at low temperature.
Using the dye which can mask the colour of all medicaments.
4. Weight variation:
Weight variation occur during the compression of granules in a tablet machine.
The tablet do not have the uniform weight.
Reasons for this defect:
Granules are not in uniform size.
Presence of excess amount of powder in the granules.
No proper mixing of lubricants.
No uniform flow of granules.
During compression change in capacity of die.
Variation in the speed of the tablet machine.
5.Hardness variation.
The tablet do not have a uniform hardness.
It depends on the weight of the material and space between the upper and lower punch during the stage of compression.
If volume of the material varies and distance varies between punches, the hardness also varies.
6.Double impression.
This effect occur when the lower punch has a monogram or some other engraving on it.
During compression, tablet receive an imprint of the punch.
Due to some defect in he machine lower punch move slightly upward before ejection of tablet and give second impression.
This can be controlled by managing the movement of punch.