This document discusses three common tablet manufacturing problems: weight variation, hardness variation, and double impression. Weight variation occurs when tablets do not have a uniform weight due to issues like poor granule flow, segregation of components, and non-uniform particle size. Hardness variation is caused by the same reasons as weight variation and depends on the weight of materials compressed and space between punches. Double impression results when the lower punch rotates during its travel after compression, making a second lighter impression on tablets. Controlling granule properties, lubricant concentration, and punch movement can help overcome these problems.

1. 4. Weight variation
This problem is encountered when the tablets do not have a uniform weight. The
problem is usually associated with:
a. Poor flow of granules b. Segregation of the different components of the granulation c.
Non uniform particle size distribution of granules d. Presence of excessive fines
e.Significant differences in the densities of different components of granulation f.
Incorrect lubrication of granulation
The problem can be overcome by:
a. Using granules of uniform particle size distribution b. Using ingredients of
approximately the same densities c. Decreasing the fines d. Using proper concentration
of lubricants, glidants etc. e. Replacement of defective punches
5. Hardness variation
This problem is encountered when the tablets vary significantly in their hardness. The
problem occurs due to the same reasons as weiht variation. Hardness of a tablet
depends on the weight of the materials being compressed and the space between the
upper and lower punches during the compression. If the weight iof the materials or the
distance between the the punches varies, the hardness will also vary.
6. Double Impression
This problem is generally evident in cases where the lower punches have a monogram
or other engravings on them. On some machines, the lower punch is free to drop and
travel for a short distance before ascending to eject the tablet out of the die. During the
free travel period, the punch may rotate and make a new, lighter impression on the
bottom of the tablet, resulting in a double impression. Similar problem may be
encountered in machines that have a precompression stage before the actual
compression.
This problem can be overcome by controlling the undesirable movement of the
punches.