Punch Penetration is also known as upper punch penetration, and it is defined as the measurement of how far the upper punch moves in the die cavity to compress powder into a tablet.
It can also be defined as how deeply the upper punch moves in the die bore during pre-compression and main compression to compress the tablet.
Upper punch penetration determines the position where the tablet will be compressed in the die bore.
The concept of upper punch penetration is used to control the tablet hardness, and it helps to prevent defects like capping and lamination by dealing with entrapped air.
Types of Machines
Some compression machines are available with fixed settings of upper punch penetration, meaning we don’t have the option to increase or decrease the punch penetration, and many machines have the option to adjust punch penetration manually or from the HMI. The machines having options to alter the punch penetration are of good choice because all product properties are not the same & we can utilise the punch penetration options to adjust the tablet hardness or to prevent the tablet capping & lamination.
Role of upper punch penetration
The control of upper punch penetration is helpful for following
- Overcome tablet capping and lamination
- Prevent tablet sticking
- Hardness/Thickness
- To reduce product loss
- Die bore protection
Overcome tablet capping and lamination
The main reason for tablet capping and lamination is trapped air in powder or granules during the compression process.
The trapped air reduces the interparticle binding and results in reduced tensile strength of the tablets.
The shallow or less upper punch penetration is helpful to overcome tablet capping and lamination, as tablets are compressed in the upper portion of the die bore by reducing the punch penetration, and trapped air has to travel a shorter distance to escape.
Increased punch penetration may result in tablet capping or lamination, as air has to travel a large distance for escape.
Prevent tablet sticking
Heat generation is commonly observed due to higher load on the punches, and this heat results in tablet sticking or picking.
The shallow punch penetration results in less heat generation and can be used to overcome sticking or picking.
Hardness and Thickness
Upper punch penetration is helpful to control the thickness of tablets, which ultimately affects the tablet hardness.
The increased upper punch penetration is helpful to reduce the tablet thickness and to increase the tablet hardness.
Product line loss
Some portion of the powders or granules is lost in the form of a puff when the upper punch enters the die bore, and this puff results in yield loss of the product.
The fluffy products having low bulk density result in puff on a shallow punch penetration, so increased punch penetration results in the prevention of product loss in the form of puff due to higher compaction pressure.
Die Bore Protection
A wear ring may develop in the die bore when tablets are compressed at the same position in the die bore.
By changing the punch penetration, the tablet compression position is altered in the die bore, and it is helpful to extend the die life.
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