Punches of tablet compression machines play an important role for the compression of tablets in pharmaceutical or nutraceutical industries.The size and shape of the tablet is dependent on the dimensions of the punches that are installed on the compression machine.
Different pairs of punches are installed on the compression machine and one of these punches is known as an upper punch and the other one is known as a lower punch.
Upper punches are installed in the upper punch holders above the turntable, meaning upper punches are on the upper side of the die table and lower punches are installed on the lower side of the die table.
In this article we will learn the most important facts about the upper and lower bunch and the fact is that the stem of the lower punch is longer than the upper punch and we will learn why it is so.
Punch stem is the part of the punch which extends below the barrel of the punch and end up
before the cup depth of the punch tip.
By physical observation of the upper and lower you have noticed that the stem of the lower punch is always larger than the stem of the upper punch.
Following main reasons,
- The upper punch only enters into the die bore when the powder is filled in the die cavity and it is ready to compress.Tip or stem of the upper punch counter the pressure applied from the lower side.
- The lower punch remains inside the die cavity even after the tablet is compressed and plays an important role for tablet ejection.
- The upper punch is pulled out from the die cavity with the help of lifting cam after tablet compression and now the tablet is ready to come out of the die cavity.
- The tablet is pushed out from the die cavity with the long stem of the lower punch as the head of the lower punch rides over the ejection cam.
- The long stem of the lower bunch is used to push the tablet in upward direction in the die cavity and in this way the tablet comes out from the die cavity when it is compressed with the help of the long stem of the lower punch.
Summery
The lower punch has a long stem because it has to push the tablet out from the die cavity after compression and the stem of the upper punch is short because it has only a role to counter the pressure applied from the lower punch during tablet compression process.