Medicine, and in particular tablet making is one of the oldest professions in existence.
Having started with a manually operated-one tablet at a time—machine, we have now evolved to a stage wherein an operator is required to only punch a few keys, and the machine produces close to 320 tablets per second.
However, in the past few years, we have really witnessed a revolution, in terms of the technology being implemented to its optimum level. The levels of automation and control are constantly on the rise. With each tablet being thoroughly scrutinised for the smallest defect, it is only natural that a tablet manufacturer would like to be rest assured that the machine he has procured is capable of producing the highest quality tablet. With a rise in the number of tablet manufacturers, there is a lot of competition and alternatives are aplenty.
But a tablet manufacturer must primarily understand which are the critical factors affecting the quality of the tablet being produced. Also, if one parameter is changed, does this create a chain reaction which in turn results in a tablet that is completely out of specification?
How does the diameter of the turret affect the speed, and thus the output?
How many stages of compression are required to ensure the tablet retains its required properties?
How much time is required to clean the machine once a batch is completed?
What are the safety features in place on the machine?
Finally and probably the most important question, what is the total cost involved with the ownership of a machine?
All these questions, while being quite elementary, unfortunately are still not thoroughly checked and verified.
India has established itself as the global pharmaceutical hub. Countries like the US, the UK, EU, Japan, Africa, Australia and others procure a lot of their medicines from India. With such high volumes of tablets being produced, close to 400-600 billion tablets/annum in the country, it is essential that the tablet manufacturers understand some of these elementary issues, before choosing their machine.
Tablet press operation and in particular, high-speed operation is a huge challenge. Each one has their own theory and specification, which they regard, will facilitate the definition of high-speed operation.
In order to choose a high-speed tablet compression machine that works efficiently, the major factors that need to be considered are:
Size of the turret
The machine must have an optimum balance between the size of the turret and the number of stations. More importantly, the turret should be fabricated within very close tolerances. If the turret diameter is too high, the machine cannot operate at high speeds, and having a few extra stations does not compensate for the lack of speed. Only a turret that has a very close tolerance and number of stations proportionate to its size can consistently operate at high speeds, without sustaining any long-term damage.
Compression stations
Nowadays, pre-compression and main compression are must. Pre-compression is important to remove the air gaps to prevent expansion of the tablet upon ejection.
Feeder
A lot depends on the ability of the feeding system in filling the powder. Studies have shown that a three chamber system has proved to be most efficient.
Dwell time
This is defined as the amount of time for which the punch head is in contact with the compression rollers. In the case of critical formulations that are difficult to compress, dwell times play a major role in determining the outcome. In order to achieve higher dwell times, the compression rollers must be large enough and robust enough to withstand a high compression pressure for an extended period of time.
Method of compression
This also plays a crucial role in order to ensure the reliability and consistent performance of the machine.
Accuracy of the load cell
This is used in measuring the compression force, and also determines whether the tablet is within its specified parameters of weight, thickness and hardness. Load cells can be accurate only if they measure compression forces in the fine and coarse range. This is possible only by having a reduced least count error.
Quality of the tooling used
This is another relevant point to be considered. The tooling used should have a long life, and the machine operation should in no way contribute in lowering the life of the tooling being used. Punch tip breakage, key angles, quality of finish, tolerances are some of the factors to be considered. Multi-tip tooling is another option that can be exercised. However, multi-tip tooling in some occasions has proved to be quite unreliable in high-speed operation due to the lack of accurate control at the time of rejection. The quality of the material used to make the tooling, and whether proper cleaning procedures are being followed, punch head angles and so on are also some of the key issues to be considered.
Rejection of a single tablet
The ability to reject at high speeds depends on factors like accuracy of load cell, speed of operation of the processing unit and so on.
Machine downtime
This is another important factor that should be taken into account. Questions such as, is the turret interchangeable? How large are the cleaning surfaces? Is there any alternative available to regular tooling? How easy is it to dismantle the parts? If these questions can be answered, it helps to save a lot of time.
Safety measures
Human life must be valued. In an industry which is dedicated to saving lives, safety norms must have top priority over and above anything else. The machine operators are the ones who are constantly working on the machines and one small error in judgment could result in the loss of a limb or worse. The machine should be capable of differentiating between various issues and displaying the errors subsequently. It should also be capable of corresponding diagnoses and performing the required corrective actions if possible automatically. If not it should have the capability to instruct a shutdown, thus manual corrections can be made. If a containment project is being implemented, all the risks associated with regard to the exposure to toxic materials should be taken into account, and appropriate operating procedures should be in ensured. Machines should be capable of complying with these safety norms as well as with those set down by the regulatory authorities.
In short, it must be appreciated that there is much more than what meets the eye while choosing/ selecting a compression machine. A good selection ensures a good tablet is on its way to the consumer with the right proportions.
The team can be contacted at [email protected]
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