Rotary Tablet Press Production Cycle

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Rotary Tablet Press Production Cycle
Unit4
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Tablet production

• Powders intended for compression into tablets
  must possess two essential properties.
• Powder fluidity
• The material can be transported through the
  hopper into the die
• To produce tablets of a consistent weight
• Powder flow can be improved mechanically by the
  use of vibrators, incorporate the glidant.
• Powder compressibility
• The property of forming a stable, intact compact
  mass when pressure is applied.

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Tableting procedure
Filling
Compression
Ejection

• In this stage compressing powder or granules are
  measured out.
• Exact measurement
• Keep the granule free-flowing
• Do not run the machine without granule.

• In this stage pressure is applied to form the
  granule into a solid.
• Protect over compressing
• Pre- compress the tablet to reduce pressure
  before fully compressing to ensure that all air
  is removed from granule.

• In this stage the tablet is ejected and ready to
  form next tablet.
• Carefully adjust the height
• Low the tablet crush between the take-off plate
  and the bore of the die
• High the tip of the punch may come into contact
  with the take-off plate

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Tablet compression machines

• Hopper for holding and feeding granulation to be
  compressed.
• Dies that define the size and shape of the
  tablet.
• Punches for compressing the granulation within
  the dies.
• Cam tracks for guiding the movement of the
  punches.
• Feeding mechanisms for moving granulation from
  the hopper into the dies.

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Tablet Presses

• Single Punch Tablet Press
• Rotary Tablet Press
• High Speed Rotary Press
• Multi-layer Rotary Press

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Single punch Tablet Press
Single Punch Tablet Press
Upper andLower Collar
Collar locker
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Rotary tablet press
How a Rotary Tablet Press Works?
Play
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Play
A Tablet Press in Operation
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The compression cycle of a rotary press
Step 1
The head of the tablet machine that holds the
upper punches, dies and lower punches in place
rotates.
Step 2
As the head rotates, the punches are guided up
and down by fixed cam tracks, which control the
sequence of filling, compression and ejection.
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Step 3
The pull down cam (B) guides the lower punches to
the bottom, allowing the dies to overfill.
Step 4
The punches then pass over a weight-control cam
(D), which reduces the fill in the dies to the
desired amount.
Step 5
A swipe off blade (C) at the end of the feed
frame removes the excess granulation and directs
it around the turret and back into the front of
the feed frame.
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Step 6
The lower punches travel over the lower
compression roll (E) while simultaneously the
upper punches ride beneath the upper compression
roll (F).
Step 7
The upper punches enter a fixed distance into the
dies, while the lower punches are raised to
squeeze and compact the granulation within the
dies.
Step 6
After the moment of compression, the upper
punches are withdrawn as they follow the upper
punch raising cam (G).
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Step 9
The lower punches ride up the ejection cam (H)
which brings the tablets flush with or slightly
above the surface of the dies.
Step 10
The tablets strike a sweep off blade affixed to
the front of the feed frame (A) and slide down a
chute into a receptacle.
Step 11
At the same time, the lower punches re-enter the
pull down cam (B) and the cycle is repeated.
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A typical production press
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• As described elsewhere in more detail the
  die-fill mechanisms in addition to gravity fill
  also include
• Force feed
• the feeding wheel has profiled paddles that
• stir and transfer the powder towards the die
• opening
• Suction fill
• the lower punch is moved downwards using
• a fill cam to create the die cavity while the
  
• top of the die is exposed to powder

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• Weight-control mechanism
• after the die is filled, the lower punch is
  
• moved upwards and part of the powder is
• ejected (weigh uniformity is critical for
• pharmaceutical tablets)
• For larger rotary presses, such as that
  illustrated in Fig.4.3a, weight uniformity is
  assisted further by the presence of a second
  paddle wheel (metering wheel)
• Additional effects include
• centrifugal forces and vibration of the system
  
• during the operation of the press.

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The fill ratio
The fraction of the die-filled after a single
pass of the shoe plotted against the shoe
velocity for a microcrystalline cellulose powder.
The critical velocity is the velocity above which
incomplete filling occurs.
Fig.4.4 The fill ratio
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• Fig.4.4 indicates that suction filling improves
  the critical velocity by a factor of 2.5. Use of
  this higher velocity gives a more accurate
  prediction of the die-fill behavior of the powder
  in the rotary press. Also, under suction filling
  the fill ratio drops less steeply at velocities
  in excess of the critical velocity and over 80
  of the die is filled at the highest shoe
  velocities used in the experiment.

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Compression schedule
The reference for punch displacement is the top
of the die table.
Fig.4.5 Compression schedule
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• Fig.4.5 shows a set of force-displacement data
  for microcrystalline cellulose obtained using a
  compaction simulator. The top-punch displacement
  was ramped linearly. The lower punch was
  maintained stationary in order to facilitate data
  analysis for model calibration as described in
  the following section.

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Die-fill on Rotary Presses

• Quality Control
• Accountability
• unique identifier
• security

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• The dominant driving force for this configuration
  is gravity.
• On rotary presses, the die-fill system consists
  of a mass flow hopper connected to a feed frame.
• The feed frame consists of a gravity hopper and
  can include motor-driven powder-transfer
  mechanisms depending on the size of the press and
  flow properties of the material that is being
  compressed.

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