Tablets are compressed by compression machines using punches and dies. Punches are used to apply pressure on powder or granules to form tablets. Two types of punches are used
- Upper punch
- Lower punch
Upper Punches are in direct contact with upper punch guiding cam and due to direct contact, friction is produced, so lubrication is required at regular time intervals at this contact point.
Sometimes excessive use drips downward along with a punch barrel and is mixed in powder or granules and contaminate the product.
Due to the poor dust collection system of compression machine, fine powder in the granules is suspended in the turret chamber and settles down over the upper punch holders and guiding cam.
This fine powder is mixed with lubricant and due to friction and upward and downward movement of punches in punch holders, this fine powder is converted into black particles.
These black particles shredded from punch barrel settle down over the rotating die table and contaminate the product. So back particles are produced on compressed tablets.
How to prevent black particles and lubricant leakage problems?
To prevent tablet contamination with dripping lubricant and black particles dust cups are used.
Dust cups may also known as dust holders and act as a reservoir for dripping lubricant. Dust cups are usually made of silicon material. Dust cups are attached to the tips or barrels of the upper punches and collect the black powders or dripping lubricant and safeguard the product from contamination.
Types of the Dust cup
Dust cups are of two types
- Conventional or Standard dust Cup
- Barrel dust cup
Conventional or Standard dust Cups
These dust cups are also known as tip dust cup. These dust cups are attached to the tips of the upper punch. These dust cups are not pre-cut. These dust cups are cut according to the tip size of the upper punch. After cutting tip of upper punch is passed through the hole of the dust cup.
How to cut tip dust cup
- Conventional Method
- Advance Method
In this method tooling for which tip dust cups are required is installed on compression machine.
Place dust cups over the dies.
Machine turret is rotated manually or at jog speed.
Punch tip makes a hole in dust cup according to the size of the tip.
In this way, the hole is made in all dust cups and dust cups are attached to the tip of each upper punch.
In this method, the compression machine is not used to make holes in dust cups.
A specific cutting machine is used in which a punch and die is used to make holes in dust cups according to the punch tip size
Barrel dust cup
These dust cups are for punch barrel. These are pre-cut according to barrel size. Barrel dust cup is inserted in the barrel and is used for the same purpose as tip dust cup.
Advantages of the dust cups
Dust cups collect dripping lubricant.
Dust cups collect black powder shredded from punch barrels.
Dust cups are easy to use.
The dust cups are washable.