Causes and Remedies of Capping in Tablet Manufacturing

When the top of a tablet separates from rest of its body, it is called tablet capping. It happens when the air in the tablet is not being released properly. The following are some of the common factors which can cause tablet capping;

1. Formulation related

2. Excipient related

3. Machine related
In this article, we will be discussing five major causes of this problem and remedies for them.

1. Fines

This is the problem faced in the formulation of the granules. Fines are small dust particles which are found in the tablets. These particles do not compress or flow very well and as a result, the tablet faces many problems.

Cause: A number of fines in the granules are more than the normal amount. If the amount of fines increases in the granules, it can further result in weight variation and segregation during compression of the tablet. This will lead to improper flow or even blockage of the flow of air.

Remedies: You need to remove all or some of the fines by using 100 to 200 mesh screen. By removal of fine particles, the air will flow properly in the tablet and the compression of the tablet will also improve.

2. Dryness

This is also a common problem which is faced in the formulation of the tablets.

Cause: When the moisture content of the tablet is kept very low, it leads to dryness of the tablet. The dryness results in the weak bonding of the granules which will cause the tablets to fall apart or create fractures in the cap.

Remedies: Adjust the moisture content so that tablets are not too dry and not too wet. There is no specific percentage of moisture content needed to make a tablet. It depends on the quantity of water which will be needed to bond the granules together. So, the moisture content needs to be perfect.

3. Upper Punch Penetration

This is a capping problem that emanates from the machine.

Cause: It happens when the penetration controls for the tablet are not set according to the ideal conditions. The ideal range of the control is from 1.5 mm to 2 mm. The main cause of this problem is the entrapped air. When the air is punched too deep in the die, it will not have sufficient room to escape from the tablet, which will later form fractures in the tablet.

Remedies: You can change the punching levels of the machine i.e. set punch penetration to 3 mm or less. You can use tapered dies.

4. Pre-compression

This problem is also found in machine controls and is caused by machine operators working on the tablet press.

Cause: Pre-compression is used to remove the entrapped air in the tablet which we discussed earlier. However, too much pre-compression will lead to manufacturing of thin tablets. Too thin thickness can lead to fractures or creation of another layer of the tablet.

Remedies: The pre-compression values or controls of the machine should be changed accordingly.

5. Tooling

Tooling is brought about using wrong controls in the machine. It is of various kinds like flat-faced, extra deep, shallow, modified ball and much more.

Causes: When the upper punch cup of the tablet curls inward, it is called j-hooking. This phenomenon can pull the tablet apart. It happens when the upper punch of the cap is not polished properly.

Remedies: Polish the tablet surface properly. You can also use tapered dies.