Convert your Double Sided Tablet Press into a Bi-Layer Production Machine

Bi-Layer Tablets is suitable for sequential release of two incompatible drugs in combination. It is mainly for sustained release tablet in which one Layer is immediate release as initial dose and second layer is maintenance dose. The production of two layer tablets has been an increasingly popular method for increasing sales appeal. This is a good method to make a product instantly identifiable in the consumers mind. The popularity of these kinds of tablets has been on the rise
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It is possible to produce Bi-Layer Tablets on any double sided press with two separate compression stations and two separate feeders for each station. The change over process from single layer to bi layer process is fairly simple procedure with minor modifications. The main challenge lies in keeping the two colours totally separate during production and maintaining the correct weight of the two layers. The requirement of a two layer tablet needs two different colour materials that should be free of mixing and have a clearly defined demarcation line showing separate layers.

In a single layer tablet being produced on a double side tablet press, the two feeders compliment each other. Excess granules or overflow from one feeder normally flows into the feeder on the other side as mixing of the granules is not a problem.

In a Bi-Layer Tablet, since the 2 powders are of different material and colours, mixing cannot be allowed. The two layers have to be completely separate. This effects the look of the final tablet as it requires a definite separation line showing two different colours.

Below is a sketch showing the sequence of Bi-Layer Tablets production.

Procedure: In the sketch below the first layer has blue granules and the second layer has red granules.

1. Two special feeders are required that prevent mixing of the two colours. The granules from the first layer are allowed to go around the turret and renter in to the same feeder. The excess granules from the second layer are not allowed to move on to the turret and are collected through a separate outlet.
2. To avoid the ejection of the first layer, the ejection cam after the first layer feeder has to be removed. This is to enable the second colour to fill on top of the first colour.
3. Press must have a dust extraction system. The feeders have a dust suction facility that can be connected to the dust extraction system. This is extremely useful in preventing the two colours from mixing.
4. It is advisable to put the layer with the higher weight as the first layer and the layer with the lesser weight as the second layer. As the filling in the second layer is limited and it depends on the upper punch entry into the die. The maximum amount of fill of the second layer can be controlled by adjusting the upper penetration system.
5. It is always advisable to put in only the first layer and set its weight. Once the weight of the first layer is set then the second powder is to be introduced and we can set the weight of the final tablet.

If during production the weights of the separate layers need to be checked, then the pressure at the first layer needs to be slightly increased so that the first layer does not bond with the second layer and the two layers come out separate during final ejection.

Changeable Gear Ring

In a one piece turret there are always problems of the gear ring wearing out. 
The gear ring can wear out due to lack of lubrication, improper worm setting and overload.

If the turret is one piece and the gear ring wears out then it is very difficult to correct the situation.

A simple way to overcome this situation is to have a turret with a replaceable gear ring. In this case if the gear ring is damaged you need to simply replace it with a new one. 

Choose the right spares

Over a period of time your Tablet Press machine starts to get damaged due to wear and tear of some parts. Since Tablet production requires stringent quality control, it is imperative to have your Tablet Press running at the desired optimum quality level. To maintain your Tablet Press you need to get it checked occasionally. If there are any parts that require replacement or servicing then it needs to be done quickly before the repercussions of the damage spreads.

When you replace a certain part of your Tablet Press you need to be sure that it will fit correctly and have a good life. Spares should be checked for good quality and a reputed supplier. It is best to outsource the spares from companies that know Tablet Press. This way you are sure that they understand your requirement. 

Good fit and good quality are the two essentials when you are looking out for spares. 

For instance:

• The cams can be made of different type of steel. However if you use the ones made from alloy steel then you can be sure that they will outlive the cams made from other metals. 
• Similarly the gravity feeder, if it is made of brass then there are chances of metal contamination and black particles. These can be found in the final produced tablets. Instead, if you use a feeder that is made of polymer then you eliminate the risk of tablet contamination due to feeders.
• Precision is another important criteria. When you purchase spares many a times they need to be corrected as they do not fit into your Tablet Press. This happens due to lack of precision and accuracy by the supplier.

Selecting the right spare will enable your machine to have a longer and trouble free life. 

Avoid cracks between two die bores in your turret!

Over a period of time machines start to face wear and tear. However if proper care and precautions are taken then you will be able to extend the life of your machines.

We will look into various aspects in later blog posts. Here in this post let’s address the problem of cracks that develop between two die bores of turret. 

A crack between two die bores is a common problem. What needs to be given attention to is the fact that once the crack is developed there is no way to correct the problem as it will only increase on further use. Ultimately the entire turret has to be replaced.

The main causes of turret cracking between two die bores is over tightening of die locking screws. This can be taken care of by making your operator aware of why the cracks happen and how best you can avoid them.

The problem of cracks between two die bores can be completely avoided by:

·         Using a torque wrench to completely avoid over tightening

·         Using smaller size die locking screws for smaller dies.

·         Using a better grade of caste iron for the turrets. 

1997 – Small tablets large volume

In the year 1997, we introduced ‘A’ tooling. These toolings are much smaller in size having a body diameter of 12.7mm and can make up to 10mm tablets. The maximum permissible load of ‘A’ tooling is the same as ‘B’ tooling i.e. 6.5tons (65KN).

Since ‘A’ Tooling had smaller diameter we could accommodate more Punches and Dies into a single Turret. Hence we developed the 59 Station Press in the same year [1997].

One of the key advantage is that the 59 Station Press increases the volume of production. Though you can produce the tablets of the size 10mm and below with ‘B’ Punches, if ‘A’ Punches are considered then your production increases. This is because a regular Double Rotary Press can accommodate only 35 Stations of ‘B’ Tooling, whereas ‘A’ Tooling can go upto 59 Stations.

This also makes the 59 Station Tablet Press a very good alternative for Multi Tip tooling that run into higher expense and maintenance. 

Spring Plugs - An easy method to lock your lower Punches!

One of the reasons why weight variations occur in your tablets could be due to the lower punches not being held in place.

In order to avoid weight variations in your tablets it is essential to use anti turning device for your lower punches. This will also reduce the wear of your lower punches. If proper locking is taken care of then it can reduce the noise level of the press as well. Add to this, the double impression on embossed tablets can be completely avoided.

Using Spring Plug is a much better method to lock your punches instead of the nylon plugs.

The earlier method required 3 parts:

1) nylon plugs 

2) spring strip and 

3) screw. 

The nylon plugs wear out very fast and they have to be replaced frequently.  It is also important to monitor the length of plugs from time to time. During tooling change over you need to remove each plug and set it again which is time consuming.

To reduce all these time consuming hurdles the Spring Plug is a better option.

In the spring plug system you need to only tighten the plugs once and lock them with a grub screw. During changing the lower punch you just need to pull the punch and push it back in. This saves a considerable time in change over of toolings

The major advantages of Spring Plug over the nylon plug system are:. 

1. Decreases Tooling change overtime
2. Requires only one time setting
3. You can set the required pressure on the lower punches.