Pharmaceutical Compaction and Compression Guide

BPH 4202
Pharmaceutical Technology III
Md. Imran Nur Manik
Lecturer
Department of Pharmacy
Primeasia University

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Compaction and Compression
Prepared By: Md. Imran Nur Manik; M.Pharm. (R.U.) Page 1
manikrupharmacy@gmail.com; Lecturer; Department of Pharmacy; Primeasia University.
Definitions
Compression
Compression means a reduction in the bulk volume of a material as a result of the
removal of the gaseous phase (air) by applied pressure.
Consolidation
Consolidation is an increase in the mechanical strength of a material resulting from
particle-particle interactions.
Compaction
Compaction of powders is the general term used to describe the situation in which these
materials are subjected to some level of mechanical force.
The physics of compaction may be simply stated as "the compression and consolidation
of a two-phase (particulate solid-gas) system due to the applied force."
Derived Properties of Powders or Granules:
Some derived properties which help in quantification of important variables are
1.Volume
2. Density
3. Porosity
4. Flow properties.
Volume: Measurement of volume of powder is not easy as the measurement of mass of
powders, because in powders there will be inter and intra- particular voids. Hence
three types of volume can be considered for a powdered mass, they are,
1. True volume
2. Granular volume Interparticulate
Open
3. Bulk volume Closed
Volume is the quantity of three-dimensional space enclosed by a closed surface, for example, the space that a
substance (solid, liquid, gas, or plasma) or shape occupies or contains. Volume is often quantified numerically
using the SI derived unit, the cubic metre.
Mass-Volume relationships
1. Open intraparticulate voids-those within a single
particle but open to the external environment.
2. Closed intraparticulate voids-those within a single
particle but closed to the external environment.
3. Interparticulate voids-the air spaces between the individual particles.

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Therefore, at least three interpretations of "powder volume" may be proposed:
True Volume of the powder (Vt): True volume is the total volume of the solid particles.
It is a volume of the particles excluding the inter and intra particulate spaces in a
powder. Or it is volume of powder itself
Granular Volume of the powder (Vg): It is the cumulative volume occupied by the
particles, including all intraparticulate (but not interparticulate) voids. Or it is the
volume of powder itself and volume of intraparticulate spaces.
Bulk Volume of the powder (Vb): It is the total volume occupied by the entire powder
mass under the particular packing achieved during the measurement.
It comprises the true volume and inter and intra particulate voids.
Relative volume (VR): It is the ratio of the the volume, V of the sample under specific
experimental conditions,to the true volume Vt.
VR = V / Vt
VR tends to become unity as all air is eliminated from the mass during the compression
process.
Density
The ratio of mass to volume is known as the density (ρ) of the material
By considering the three types of volume of powders, we can define the respective
densities as,
True density (ρt): Mass of the powder/ True volume of the powder.
True density, ρt = M / Vt
Granular density (ρg): Mass of the powder/ granule volume of the powder.
Granular density, ρg = M / Vg
Bulk density (ρb): It is the ratio of total mass of the powder to the bulk Volume of the
powder. It is measured by pouring the weighed powder into a measuring cylinder and
the volume is noted.
It is expressed in gm/ml and is given by: ρb = M / Vb
Where, M is the total mass of the powder
Vb is the Bulk Volume of the powder
Porosity
The voids present in the powder mass may be more significant than the solid components in certain studies.
For example, a fine capillary network of voids or pores has been shown to enhance the rate of liquid
uptake by tablets, which in turn increases the rate of their disintegration. For this reason, a second
dimensionless quantity, the ratio of the total volume of void spaces (Vv) to the bulk volume of the material, is
often selected to monitor the progress of compression. This is known as porosity.

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The spaces between the particles in a powder are known to be voids. The volume
occupied by such voids is known to be void volume.
Void volume (Vv) = Bulk volume –True volume
The porosity of the powders is defined as ratio of the void volume to the bulk volume of
the packing. Or, the ratios of the total volume of void spaces (Vv) to the bulk volume of
the material.
Porosity (E) = void volume /bulk volume.
=Vv/Vb
= [Vb - Vt / Vb] (As, Vv= Vb - Vt)
= 1-(Vt/bt)
Porosity is frequently expressed in percent
E = [1- Vt / Vb] x 100
The relation between porosity and compression is important because porosity
determines the rate of disintegration, dissolution and drug absorption.
Question: A cylindrical tablet of 10 mm diameter and 4 mm height weighed 480 mg and
was made from material of true density 1.6 g Cm-3
. Clculate the bulk volume Vb .
Flow Properties: To get uniformity of the weight of the tablet, the powder should
possess a good flow property. Flow properties of the powders depend on the-
 Particle size,
 Shape,
 Porosity and density,
 Moisture of the powder.

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Particle size
The rate of flow of powder is directly proportional to the diameter to the particles.
Beyond particular point, flow properties decreases as the particle size in
increases. Because in small particle (10µ) the vanderwaal‟s, electrostatic and
surface tension forces causes cohesion of the particles resulting poor flow.
As the particle size increases, influence of gravitational force on the diameter
increases the flow property. But appropriate blends of fines & coarse improves
flow characteristic, as the fines get absorbed and coarse particle reduce friction.
Particle shape
Spherical, smooth particles improves flow properties, surface roughness leads to poor
flow due to friction and cohesiveness , flat and elongated particles tend to pack loosely,
obstructing the flow
Density & porosity
Particles having high density and low internal porosity tend to posses good flow
properties.
Moisture
The higher moisture content, the flow property will be poor owing to cohesion and
adhesion.
Angle of repose
The flow characteristic is measured by angle of repose. Angle of repose is defined as
the maximum angle possible between the surface of a pile of powder and the horizontal
plane.
tan Ø= h/r
Ø = tan-1(h/r)
Where, h = height of pile
r =Radius of the base of pile.
Ø = Angle of repose .
The angle of repose is calculated by measuring the height and radius of heap of powder
formed.
The frictional forces in a loose powder can be measured by Angle of repose.
The lower the angle of repose better will be flow property.

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The values of angle of repose are given below:
Angle of repose (in degrees) Type of Flow
<25 Excellent
25-30 Good
30-40 Passable
40> Very poor
Carr’s consolidation (Compressibility) Index (CI)
It indicates powder flow properties. It is expressed in percentage.
It is defined as:
Consolidation Index = I = Tapped density-Poured density /Tapped density
Therefore = (Dt- Db/Dt) × 100
Where, Dt is the tapped density of the powder
Db is the Poured density of the powder
Determination of Tapped density & Poured density.
It is determined by passing a fixed quantity of powder into a measuring cylinder and the
volume is noted .CI can be calculated by founding out by tapped density and Poured
density of powder.
Grading of the powder for their flow properties according to Carr‟s index:
Carr’s index (%) Type of flow
5-15 Excellent
12-18 Good
18-21 Fair to passable
23-35 Poor
33-38 Very poor
>40 Very very poor
Compression properties
This involves compressibility and compactability.
Compressibility can be defined as the ability of a powder to decease in volume under
pressure. Powders are normally compressed into tablets using a pressure of about
5.0kg/cm2.

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Compactibility can be defined as ability of powder to be compressed in to a tablet of a
certain strength or hardness.
These two relate directly to the tableting performance.
For proper compression to occur the tablet should be plastic i.e., capable of permanent
deformation and it should also exhibit certain degree of brittleness.
If the drug is plastic, then the excipients chosen should be brittle (lactose, calcium
phosphate) and if the drug is brittle, then the excipients should be plastic
(Microcrystalline cellulose).
In the absence of external force, molecules are in their equilibrium positions with lowest free
energy as determined by the inter-atomic and intermolecular forces. In response to an applied
stress, molecules or their parts will change their mutual positions from their original equilib-
rium positions to new positions with higher free energy. Thermodynamics then compels (
) molecules to return to the original positions with the lowest free energy, resulting in a
returning elastic force that counterbalances the applied stress. At the new equilibrium position,
the internal elastic force equals to the applied external force.
Within a limited extent, the deformation of a solid body is reversible. This type of deformation
is referred to as the elastic deformation. Elastic deformation obeys the Hook’s Law, which
states that the deformation is proportional to the applied stress.
Plastic Deformation
Plastic deformation refers to irreversible changes in the internal molecular structure (or
microstructure) of a material subject to applied stress.
Consolidation
An increase in the mechanical strength of the material resulting
from particle or particle interaction. (Increasing in mechanical
strength of the mass)

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Consolidation Process
Cold welding: When the surface of two particles approach each other closely enough,
(e.g. at separation of less than 50nm) their free surface energies result in strong
attractive force, this process known as cold welding.
Fusion bonding: Contacts of particles at multiple points upon application of load,
produces heat which causes fusion or melting. If this heat is not dissipated, the local rise
in temperature could be sufficient to cause melting of the contact area of the particles.
Upon removal of load it gets solidified giving rise to fusion bonding & increase the
mechanical strength of mass.
Factors affecting consolidation
Both the “cold" and "fusion" welding, the process is influenced by several factors,
including:
1. The chemical nature of the materials
2. The extent of the available surface
3. The presence of surface contaminants
4. The inter-surface distances
Properties of tablet influenced by compression
1. Density and porosity:
The apparent density of a tablet is exponentially
related to applied pressure
(or compressional force) until the limiting
density of the material is achieved.
As compressional force increases the density of
tablet also increases as a result of decrease in
bulk volume.
Fig.1.1: Influence of compressional force on apparent density

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Fig.1.2: Effect of compressional force on porosity
As the porosity and apparent density are inversely proportional, the plot of porosity
against log of compression force gives linear plot with a negative slope (Fig.1.2.).
Therefore the relation between density and porosity is
E=1-(1/Vr) [Where, E=Porosity and Vr= Relative volume)
2. Hardness and tensile strength
Tensile strength :( In the General Physics) a measure of the ability of a material to withstand a longitudinal stress,
expressed as the greatest stress that the material can stand without breaking. Tensile strength measures the force
required to pull something such as rope, wire, or a structural beam to the point where it breaks.
There is a linear relationship between tablet hardness & the logarithm of applied pressure
except at high pressure.
Fig.2.1: Influence of compressional force on the tablet hardness.
The strength of tablet may be expressed as tensile strength. As shown in the following figure
(Fig.2.2). The tensile strength of crystalline lactose is directly proportional to the compressional
force .i.e. Increase in the compressional force increases the strength of the tablet.
0
20
40
60
80
100
120
0 10 20 30 40
Porosity
Log of Compressional Force (C.F)
0
20
40
60
80
100
120
0 10 20 30 40
Hardness
log of C.F.

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Fig.2.2: Influence of compressional force on the tensile strength of a tablet.
3. Specific surface area:
Specific surface area is the surface area of 1 gm material. Specific surface area initially
increases to a maximal value as the compressional force increases, indicating the
formation of new surface due to fragmentation of granules.
Fig.3.1: Influence of compressional force on the Specific surface area of a tablet.
Further increase in force produce a progressive decrease in surface area due to
bonding of particles.
4. Disintegration
Usually as the applied pressure used to prepare a tablet is increased, the disintegration
time increases (lactose/aspirin alone).
Frequently, there is exponential relationship between disintegration time and pressure
(aspirin-lactose).
0
5
10
15
20
25
30
35
40
45
0 5 10 15 20
Tensilestrength
Compressional force

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Fig.4.1: Influence of compressional force on the Disintegration time of a tablet.
In some formulation there is minimum value when applied pressure is plotted against
log of disintegration time (with 10% and 15% starch in sulfadiazine tablets)
For tablets compressed at low pressure, there is a large void, and the contact of starch
grains in the inter-particular space is discontinuous. Thus there is a lag time before the
starch grains, which are swelling due to imbibitions of water, contact and exert a force
on surrounding tablet structure.
For tablets compressed at certain applied pressure, the contact of starch grains is
continuous with the tablet structure, and the swelling of starch immediately exerts
pressure, causing the most rapid disintegration.
For tablets compressed at pressures greater than that producing minimum
disintegration time, the porosity is such that more time is required for the penetration of
water into the tablet, hence increase in disintegration time.
5. Dissolution
The effect of applied pressure on dissolution rate may be considered from viewpoint of
disintegrating and non-disintegrating tablets.
For a conventional tablet (uncoated) dissolution depends on
a. Temperature
b. The properties of the API
c. The properties of the excipients etc.
d. Properties of solvent
The effect of applied pressure on dissolution of disintegrating tablet is difficult to
predict.
If fragmentation of granules occurs during compression, the dissolution is faster as the
applied pressure is increased, because of increase in specific surface area.
0
20
40
60
80
100
120
0 10 20 30 40
DisintegrationTime
log of C.F.

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If bonding of particle predominantly occurs during the compression, then it decreases
the dissolution.
Pressure
(N/cm2)
t50% (min)
Starch paste Methylcellulose solution Gelatin solution
200
400
600
800
1000
2000
54.0
42.0
35.0
10.0
7.0
3.3
0.5
0.8
1.1
1.2
1.4
1.8
10.0
4.5
3.0
4.6
4.9
6.5
Table: Effect of compressional force on dissolution of Sulfadimide tablets prepared with various
granulating agents
Heckel Equation
The changes in the volume with the applied pressure ids defined by various equations
among them the “The Heckel Theory” is the most important. Heckel considered that the
reduction in the voids obey the first order kinetics relationship with the applied
pressure. Where pores are reactant & densification is the product.
For the compressional process Heckel has proposed the following equation known as
the “Heckel Equation”
-----------------------(1)
Where, V= Volume at the applied pressure “P”
Vₒ=Original volume of the powder including the voids
Vα=Volume of the Solid Powder excluding the voids
K=A constant related to the “yield pressure” of the powder
P=Applied pressure
We know that, porosity “E” is the ratio of the total volume of the void space to the bulk
volume of the powdered material.
i.e.
Or, --------------------------(2)
From the equation 1 and 2 we get
--------------------------(3)
This is the rearranged or moderate form of Heckel Equation.

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Heckel Plot
When or is plotted against the applied pressure P, we get a plot known
as Heckel Plot. The nature of the plot depends on the characteristics of the material to be
compressed. The Heckel plot explains the mechanism of bonding.
Materials that are comparatively soft and that readily undergo plastic deformation retain
different degrees of porosity, depending upon the initial packing in the die. This in tum
is influenced by the size distribution, shape, etc. of the original particles. Heckel plots
for such materials are shown by type a in Figure 4-17; sodium chloride is a typical
example.
Conversely, harder materials with higher yield pressure values usually undergo
compression by fragmentation first, to provide a denser packing. Label b in Figure 4-17
shows Heckel plots for different size fractions of the same material that are typical of this
behaviour. Lactose is one such material.
Fig. 4-17: Examples of Heckel plots. Curves i, ii, and iii represent decreasing particle size fractions of
the same material. Type a curves are typical of plastically deforming materials, while those in which
fragmentation occurs initially tend to show type b behaviour.
Application of Heckel Plot: The plot is used
i. To check lubricant efficacy.
ii. For interpretation of consolidation mechanisms.
iii. To distinguish between plastic and elastic deformation characteristics of a
material.

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Limitations
1. The plot is linear only at high pressure.
2. The plot can be influenced by time of compression and degree of lubrication.
Processes of Compression
In pharmaceutical tableting an appropriate volume of granules in a die cavity is
compressed between an upper & lower punch to consolidate the material in to a single
solid matrix, which is subsequently ejected from the die cavity as an intact tablet. The
subsequent events that occur in the process are:
1. Transitional repacking or Particle
rearrangement.
2. Deformation at the point of contact.
3. Fragmentation.
4. Bonding.
5. Deformation of the solid body.
6. Decompression.
7. Ejection.

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Transitional repacking or Particle rearrangement
The particle size distribution and shape of granule determines initial packing.
In the initial stages of compression, the punch and particle movement occur at
low pressure.
During this, particle move with respect to each other & smaller particles enter the
voids between the larger particles. As a result the volume decreases and bulk
density of granulation increases.
Spherical particles undergo less rearrangement than irregular particles as
spherical particle tend to assume a close packing arrangement initially.
To achieve a fast flow rate required for high speed presses the granulation is
generally processed to produce spherical or oval particles; thus, particle
rearrangement and energy expended in rearrangement are minor consideration
in the total process of compression.
Deformation at the point of contact
When a stress is applied to a material,
deformation (change of form) occurs. If the
deformation disappears completely (returns
to original state) upon the release of stress,
then it is called an elastic deformation. If the
deformation that does not completely
recover after release of stress is known as
plastic deformation.
The force required to initiate plastic deformation is known as yield stress. When the
particles of the granulation are so closely packed so that no further filling of the void can
occur, a further increase of compressional force causes deformation at the point of
contact.
Both plastic and elastic deformation may occur although one type predominates for a
given material.
Fragmentation
As the compressional load increases the deformed particle starts undergoing
fragmentation. Because of the high load, the particle breaks into smaller fragments
leading to the formation of new bonding areas. The fragments undergo densification
with infiltration of small fragments into voids.

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In some materials where the shear stress is greater than the tensile strength, the
particles undergo structural break down. This is called brittle fracture.
Example: sucrose – shear strength is greater than the tensile strength.
With some materials fragmentation does not occur because the stresses are relieved by
plastic deformation. Plastic deformation may be thought of as a change in particle shape and as the
sliding group of particles in an attempt to relieve stress (viscoelastic flow). Such deformation produces
new, clean surface that are potential bonding areas.
Irrespective of behaviour of large particles, small particles may deform plastically, a process known as
microsquashing, and the proportion of fine powder in a sample may therefore be significant.
Fragmentation do not occur when applied stress-
• Is balanced by a plastic deformation.
• Change in shape.
• Sliding of groups of particle (viscoelastic flow).
Bonding and Consolidation
After fragmentation of the particles, as the pressure increases, formation of new bonds
between the particles at the contact area occurs. The hypothesis favouring for the
increasing mechanical strength of a bed of powder when subjected to rising
compressive forces can be explained by the following theory.
Bonding/Consolidation Mechanism
There are three theories about the bonding of p[articles in the tablet by compression
I. Mechanical theory
II. Intermolecular force theory
III. Liquid-Film surface theory
The mechanical theory
It occurs between irregularly shaped particles.
The mechanical theory proposes that, under pressure the individual particles undergo
Elastic / Plastic deformation and the particle boundaries that the edges of the particle
intermesh forming a mechanical Bond.
Mechanical interlocking is not a major mechanism of bonding in pharmaceutical
tableting.

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Intermolecular force theory
The Molecules at the surface of solids have unsatisfied forces which interact with the
other particle in true contact.
According to this theory, under compressional pressure the molecules at the points of
true contact between new clean surfaces of the granules are close enough so that
vanderwaals forces interact to consolidate the particles.
Material containing plenty OH group may also create hydrogen bond between
molecules. E.g. microcrystalline cellulose is believed to undergo significant hydrogen
bonding during tablet compression
The intermolecular forces theory and the liquid-surface film theory are believed to be
the major bonding mechanisms in tablet compression
Liquid-surface film theory
Due to the applied pressure, the particles may melt (due to lowering of M.pt.)
or dissolve (due to increased solubility).
Many pharmaceutical formulations require a certain level of residual moisture to
produce high quality tablets. The role of moisture in the tableting process is supported
by the liquid-surface film theory. Thin liquid films form, which bond the particles
together at the particle surface.
The energy of compression produces melting or liquefaction of the particles at the
contact areas. As the pressure is withdrawn the melted ingredients solidifies causing
fusing of the particles.
In addition the solubility of the solution at the particle interface under pressure is
increased and as the pressure is released it gets super saturated and followed by
subsequent solidification or crystallization thus resulting in the formation of bonded
surfaces.
Deformation of the Solid Body
On further increases of the pressure, the non- bonded solid is consolidated towards a
limiting density by plastic or elastic deformation.
Decompression
As the applied force is removed, a set of stresses within the tablet gets generated as a
result of elastic recovery. The tablet must be mechanically strong enough to
accommodate these stress, otherwise the tablet structure failure may occur.
If the degree and rate of elastic recovery are high, the tablet may cap or laminate. If the
tablet undergoes brittle fracture during decompression, the compact may form failure

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planes as a result of fracturing of surfaces. Tablets that do not cap or laminate are able to
relieve the stresses by plastic deformation.
*The tablet failure is affected by rate of decompression (machine speed).
Ejection
Finally as the lower punch rises and pushes the tablet upward, there is continued
residual wall pressure and considerable energy May be expanded due to the die wall
Friction.
Strength of the Tablets
The tablet should be sufficiently strong to withstand the mechanical shocks during the
subsequent handling and transport. The mechanical strength of tablet is described by
the following parameters.
a. Crushing Strength
b. Friability
c. Hardness
d. Bonding Strength
e. Fracture resistance.
Crushing Strength
The most popular estimate of tablet strength has been crushing strength, Sc, which may
be defined as "that compressional force (Fc) which, when applied diametrically to a
tablet, just fractures it.”
It may then be described by the equation=
Where ST is the tensile strength, Fc is the compressional force and D & H are the
diameter and thickness of the tablet, respectively.
Friability
The crushing strength test may not be the best measure of potential tablet behaviour
during handling and packaging. The resistance to surface abrasion may be a more
relevant parameter. For example by the friability test.
These test measure the weight loss on subjecting the tablets to a standardized agitation
procedure. The most popular (commercially available) version is the Roche Friabilator,
in which approximately 6 g (Wₒ) of de-dusted tablets are subjected to 100 free falls of
6 inches in a rotating drum and are then reweighed (w).
The friability, f, is given by:

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Factors Affecting Strength of the Tablets
The following factors affect the strength of tablet
1. Particle size
2. Particle shape & surface roughness
3. Compaction pressure
4. Binders
5. Lubricants
6. Entrapped air
7. Moisture content
8. Porosity
Particle size
Smaller particles have larger surface area & when these are exposed to atmosphere
may be prone to oxidation and moisture absorption takes place which affects the
strength of tablet.
Extensive fragmentation during compaction of a brittle material may result in a large
number of interparticulate contact points, which in turn provide a large number of
possible bonding zones. The tablets made of these materials can have a high
mechanical strength.
The increase in mechanical strength is attributed to an increase in the surface area
available for interparticulate attractions, as the particles become smaller.
Particle shape & surface roughness
The mechanical strength of tablets of materials with a high fragmentation tendency are
less affected by particle shape and surface texture. Particle shape affects the inter
particulate friction & flow properties of the powder. Spherical particles are considered
to be ideal.
General particle shapes and their effect on powder flow are as follows:
Spherical particles - Good
Oblong shaped particles - Poor
Cubical shaped particles - Poor
Irregular shaped particles - Medium
Compaction pressure
The compaction pressure and speed affects the strength of the resulting tablet.
A fragmenting material has been shown to be less affected by variations in compression
speed. The behaviour of granules during compaction, the extent to which they bond
together & the strength of the inter granule bonds relative to the strength of the granules
determine tablet hardness.

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Binders
A binder is a material that is added to a formulation in order to improve the mechanical
strength of a tablet. In direct compression, it is generally considered that a binder
should have a high compactibility to ensure the mechanical strength of the tablet
mixture. Addition of a binder which increases elasticity can decrease tablet strength
because of the breakage of bonds as the compaction pressure is released.
Lubricants
Lubricants are used to improve granule flow, minimize die wall friction & prevent
adhesion of the granules to the punch faces. Lubricant decreases the strength of the
tablets. When lubricants are added as dry powder to granules, they adhere & form a
coat or a film around the host particles during the mixing process. The Lubricant film
interferes with the bonding properties of host particle by acting as a physical barrier.
When the tablet is blended lightly, the lubricant is present as a free fraction. Prolonged
mixing time will produce a surface film of lubricants over the drug particles due to
which inter particulate bonding is reduced.
Entrapped air
When the air does not freely escape from the granules in the die cavity, the force
created by the expansion of the entrapped air may be sufficient to disrupt the bonds.
The presence of entrapped air will produce a tablet which can be broken easily & it
lowers the tablet strength.
Moisture content
A small proportion of moisture content is desirable for the formation of a coherent
tablet. At low moisture content there will be increase in die wall friction due to
increased stress, hence the tablet hardness will be poor. At high moisture level the die
wall friction is reduced owing to lubricating effect of moisture. At further increase in
moisture content there will be decrease in compact strength due to reduction in inter
particulate bond.
Optimum moisture content is in the range of 0.5 – 4%.
Porosity
When particles of large size are subjected to light compression the tablet will be highly
porous–low tablet strength. Reduction in porosity is due to granule fragmentation giving
smaller particles which may be more closely packed & plastic deformation which allows
the granules to flow into the void spaces.

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Parts of a Tablet Press
Tablet presses are designed with following basic components:
1. Hopper for holding and feeding granulation
2. Dies that define the size and shape of the tablet.
3. Punches for compressing the granulation within the dies.
4. Cam tracks for guiding the movement of the punches.
5. A feeding mechanism for moving granulation from hopper into the dies.
Auxiliary Equipment’s
1. Granulation Feeding Device: In many cases, speed of die table is such that the time
of die under feed frame is too short to allow adequate or consistent gravity filling of die
with granules, resulting in weight variation and content uniformity. These also seen with
poorly flowing granules. To avoid these problems, mechanized feeder can employ to
force granules into die cavity.
2. Tablet weight monitoring devices:- High rate of tablet output with modern press
requires continuous tablet weight monitoring with electronic monitoring devices.
3. Tablet Deduster: In almost all cases, tablets coming out of a tablet machine bear
excess powder on its surface and are run through the tablet de-duster to remove that
excess powder.
4. Fette machine: Fette machine is device that chills the compression components to
allow the compression of low melting point substance such as waxes and thereby
making it possible to compress product with low meting points.

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Instrumented tablet machines and tooling
The tablet press is a high-speed mechanical device. It compresses the ingredients into
the required tablet shape with extreme precision. It can make the tablet in many shapes,
although they are usually round or oval. Also, it can press the name of the manufacturer
or the product into the top of the tablet.
Tablet punching machines work on the principle
of compression.A tablet is formed by the
combined pressing action of two punches and a
die.
Punches & Dies
Tooling Station: - The upper punch, the lower
punch and the die which accommodate one
station in a tablet press.
Tooling Set: A complete set of punches and dies
to accommodate all stations in a tablet press.Tooling
Tablet compression machines are made in keeping in view the type of dies and punches
will be used on them, the dies and punches and their setup on compression machine is
called tooling, it is classified as B and D mainly.

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The B tooling dies and punch can be further
have specifications as BB and D tooling can
also be dies and punches can be utilised on B
tooling machine which is called as DB
Mainly there are two standards, D and B.
Difference between B and D tooling
Different Shapes of Dies and Punches
1. Round shape punch die set
2. Oval shape punch die set
3. Capsule shape punch die set
4. Geometric shape punch die set
5. Irregular shape punch die set
6. Core rod tooling punch die set
Round shape Punch Die Set
Used by pharmaceutical and veterinary industry. Fig: Round Shape
Can manufacture following type of tablets:
 Shallow Concave Ball Shape
 Deep Concave Flat Faced
 Concave with Edges Flat with Bevel Edges
 Normal Concave
Oval Shape Punch Die Set Fig: Oval Shape
Applicable to pharmaceutical and ayurvedic industries.
Can manufacture following types of tablets:
 Flat Faced Flat with bevel edges
 Concave/Deep/Deep Concave with bevel edges.
Capsule shape punch die set Fig: Capsule Shape
Applicable to pharmaceutical and ayurvedic industries.

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Can manufacture following types of tablets:
 Concave with Edges
 Deep Concave Flat Faced
 Normal concave Flat with Bevel Edges.
Geometric Shape Punch Die Set
Applicable to pharmaceutical, confectionery, chemical, industrial powder metallurgy
industries. Can manufacture following types of tablet:
 Triangular
 Benzene
 Rhombus
 Rectangular Square
Irregular Shape Punch Die Set
Are applicable to confectionery industries.
Available with different size, concavity, and flat in plain or
engraved break line.
Problems associated with large scale manufacturing of tablets.
In olden days tablets were initially punched on small scale with hand operated
machines, which suffered the problem of varied strength and integrity.
But now the tablet punching machines are all mechanized, the mechanical feeding of
feed from the hopper into the die, electronic monitoring of the press, but tablet process
problem still persist.
The Imperfections known as: „VISUAL DEFECTS‟ are either related to Imperfections in
any one or more of the following factors.
1. Formulation design,
2. Tableting process,
3. Machine.

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The defects related to Tableting Process.
• CAPPING: Partial or complete separation of the top or bottom of tablet due to air-
entrapment in the granular material.
• LAMINATION: Separation of tablet into two or more layers due to air-entrapment
in the granular material.
• CRACKING: Small, fine cracks observed on the upper and lower central surface
of tablets, or very rarely on the sidewall.
• CHIPPING: Breaking of tablet edges.
The defects related to Formulation.
• STICKING: The adhesion of granulation material to the die wall.
• PICKING: The removal of material from the surface of tablet and its adherence to
the face of punch.
• BINDING: Sticking of the tablet to the die and does not eject properly out of the
die.
The defect related to Machine.
• DOUBLE IMPRESSION: Due to free rotation of the punches, having some
engraving on their faces.
The defect related to more than one factor.
• MOTTLING: Unequal distribution of colour on a tablet with light or dark areas.

Pharmaceutical Compaction and Compression Guide

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Pharmaceutical Compaction and Compression Guide