Common defects that can occur during tablet production include capping and lamination, picking and sticking, mottling, weight variation, hardness variation, and double impressions. Capping and lamination involve the separation of the tablet layers, while picking and sticking involve material adhering to the punches. Mottling is uneven color distribution. Weight and hardness variations result from issues like poor granule flow and inconsistent compression. Double impressions occur when the lower punch rotates during ejection and makes a second impression. Care must be taken to properly formulate and process the granules, operate the tablet press correctly, and maintain the equipment to minimize these defects.

1. TABLETS

2. Common tableting problem
During the routine production of tablets so many
defects arise with the finished tablets may be due to
either some faults in tablet formulation or in the
tableting equipment and sometimes due to both
reasons.
The defects are as follows:
1. Capping and Lamination
2. Picking and Sticking
3. Mottling
4. Weight variation
5. Hardness Variation
6. Double impression

3. Capping and Lamination:
Capping is the partial or complete separation of
the top or bottom crowns of a tablet from the main
body of the tablet.
Lamination is the separation of a tablet into two or
more distinct layers.
Usually, these processing problems are readily
apparent immediately after compression; however,
capping and lamination may occur hours or even
days later.
Subjecting tablets to the friability test is the
quickest way of revealing such problems.

4. Reasons
1. Due to the entrapment of air among the particles
or granules during the compression
2. Too much pressure on compression.
3. Presence of either excess of fine powders of
granules or less amount of fines in granules.
4. A granulation that is too dry tends to cap or
laminate for lack of cohesion.
5. Often deep concave punches produce tablets that
cap.
6. The wear and tear of punches and dies is also
responsible for capping.
7. The wrong setting of dies or punches also causes
capping and lamination.

5. Recover
1. Slowing tableting rate.
2. By reducing the pressure adjustments.
3. By addition of hygroscopic substance e.g.
sorbitol to maintain a proper moisture level.
4. By replacing the worn out dies and
punches.
5. By correcting the level of the top of the
lower punch so as to coincide with the level
of the upper surface of the die.
6. By using proper granules and required
amount of fine powders.

6. Picking and Sticking:
In picking a small surface of the tablet
material is removed by the punches and
adheres to the surface of punches therefore
the resulting tablets show a pitted surface
instead of smooth surface.
In sticking the tablet material i.e. the
granules adhere to the die wall and thereby
the lower punch cannot move freely.

7. Reason:
1. For the presence of scratches or engraving
or embossing on the punches.
2. For using wet granulation during
compression.
3. Sticking may be happened due to the use of
damp granules or, due to worn out dies and
punches.
4. Excessive moisture may be responsible.
5. Low melting point substances, either active
ingredient or additives may soften from heat of
compression and thus can cause sticking and
picking.

8. Recover:
1. Lettering should be designed as large as possible.
2. By using chromium plated punches for producing a
smooth non-adherent face.
3. By using dry granules and by adding a lubricant to
the granules.
4. In some cases colloidal silica added to formula acts
a polishing agent and makes the punch faces smooth
sometimes additional binder or a change in binder
may make the granules more cohesive and therefore
less adherent.
5. By using higher melting point materials as diluents.
6. In case of excessive moisture further drying of the
granules.

9. Mottling:
Mottling is an unequal distribution of color on a
tablet, with light or dark areas standing out in an
otherwise uniform surface.
Causes:
1. Due to the difference of colors in the drugs
and the added excipients.
2. Due to the colored degraded products of the
drug.
3. Due to the migration of dyes during drying of
granules.
4. Due to the use of colorants in direct
compression formulation.

10. Prevention:
1. By using a dye which can mask the color
of tablet ingredients.
2. By changing the solvent system of the
granulation.
3. By drying the granules at a low
temperature.
4. By changing the binder system.
5. By grinding to a smaller particle size.

11. Weight variation:
Weight varies beyond the specifications.
Causes:
1. Poor flow of granules to the die; size separation
of granules i.e. small and large size granules.
2. Presence of too fines in the granules.
3. Separation of the mixed ingredients of granules
4. Less quantity of poor mixing of lubricants.
5. Due to automatic change in the adjustment of
punches.
6. In rotary tablet making machines this defect is
due to unequal length of lower punches.

12. Overcome:
1. Making granules of good flow properly.
2. Proper granulation
3. Removing the too fines from the
granulation etc. according to the causative
factors.

13. Hardness variation:
The tablet varies greatly in hardness.
Reasons: The reasons for this variation are the
same as discussed under weight variation. Apart
from these reasons other factors include:
1. Density of material.
2. Space between the upper and lower punches at
the time of compression.
3. Inappropriate pressure applied on the upper
punches
4.Excessive proportions of fatty lubricant such as
magnesium stearate.
5. Some times on normal storage of tablets.

14. Problem: It is important to note that the
tablets should not be harder than required.
The hard tablets may not disintegrate in the
required period of time and to soft tablets
may not withstand the hazards during
handling, transporting and dispensing.
Overcome:
This defect should be made up by addressing
the causative factors.

15. Double impression:
This defect occurs in those tablets on which
letters are printed. This involves only lower punch
which has a monogram to produce a impression
on the tablet during compression.
On some machines the punch travels uncontrolled
upward to a short distance to push the tablet out
of the die. During its free travel it rotates and
makes second impression on the tablet. This
impression is generally lighter than the original
impression.
The new tablet making machines are fitted
with devices which prevent the rotation of the
lower punch.

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