|1. What is tablet
|2. How does the
powder stick together due to compaction ?
|3. Tablet press
|4. Tablet press manufacturers|
Tablet presses, and more generally rotary punch and die presses, are used in various industries to compact powder and granulates and then produce a tablet that can be easily handle, sold, and absorbed by the customer. Those machines are of course widespread in pharma industry and also now in the growing food supplement industries. The same compaction principle is however found in heavier industries for example producing refractory bricks although the machine size is different and is rather not of the rotary type but more a single stroke machine.
A tablet press machine is an equipment which allows to agglomerate powder or granules thanks to compaction. The process, dry, consists in having a blend of powder or granules (powder which have been submitted to a prior step of granulation such as wet agglomeration), introduce the powder in a die, and apply a high pressure with a couple of punches. The pressure is compacting the powder, deforms it, and makes it adhere together.
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Compaction is basically a dry process during which solids particles are made to stick together and keep a certain shape thanks to the action of a high pressure. When compacting the powder, different phenomena take place that allows to get a tablet or a briquette (for bigger machines), those phenomena are listed below, although only some of them may be at play for a given application [Pietsch] :
In any case, the compression forces must be such that the solids particles are withstanding a plastic deformation [Perry] which is leading to a very intimate contact in between particles leading to some of the bonding phenomena mentioned previously. A typical compression cycle and its effect on the solids particles is represented in graph 1. It should be noted that the materials, after compaction, and once the pressure is released are usually slightly expanding due to the release of compressed air and / or a form of elastic recovery of the material [Pietsch].
Graph 1 : the mechanisms of pressure agglomeration with the different stages reached and impact on the material
In some cases, the addition of a binder is required if compression of the bulk solids is only yielding weak bonding that do not give enough mechanical strength to the compact (tablet, briquette...) produced.
The compaction process in a tablet press machine is done following these steps :
Figure 1 : working principle of a rotary punch and die press used for tabletting
These different actions can be done on a single punch and die
press, for example for lab machines, or for compressing a large
amount of materials, but the different components can also be
arranged on a turret that allows to increase a lot the punching
frequency, albeit with a small amount of material, as it is the
case in pharma. The figure below is showing the working principle
of a rotary punch and die press to produce tablets in
pharmaceuticals or food supplement industries.
Tablet presses are found in major industries such as pharmaceuticals, food supplements or ceramics, thus many manufacturers have developped tablet presses to compete in this extensive market.
When contacting a manufacturer, whether for a new or second hand
(used) tablet press, make sure to check its references and engage
in a detail conversation with the sales and technical staff to
understand the degree of knowledge of the vendor and how best he
will be able to support you when operating and maintaining the
[Pietsch] Agglomeration Processes (Phenomena, Technologies, Equipment), Pietsch, Wiley-VCH, 2004
[Perry] Perry's Chemical Engineer's Handbook, Section 21 Solid-Solid operations and processing, page 21-105, McGraw-Hill, 2008