In everyday life, we usually encounter someone who has an illness and has been prescribed tablets/pills to be taken. Common discomforts such as headaches and stomach pains are fixed quickly by taking pills or tablets. We rarely contemplate where these pills come from or how they are made despite them being so vital in our lives. Pills and tablets are among the most common pharmaceutical medications that are sold to the general public.

Pill pressing machines are mechanical devices that are designed to mass produce pills. Due to different innovations and improvements, it is possible to produce up to 500,000 tablets per hour. The working principle is the compressing of an upper and lower punch in a die hole with the help of hydraulic pressure. This pressure is applied is transmitted through static fluid. This pressure on the powder forces it to form a hard tablet.  Typical pill pressing machines are constructed with five main components which consist of a hopper that holds and feeds the granules, dies that shape the size and thickness of the tablet. In addition it has punches, cam tracks and a feeding mechanism. These machines accomplish high production rates by a powder compaction process which can be divided into three distinct stages:

Filling  

This stage involves the transfer of raw materials into the required position for compression.  The raw materials, prior to compression undergo processing by wet and dry granulation, and sizing. The processing produces a homogeneous blend which is ready for filling. The powder is then deposited into the die cavity which has a volume appropriately designed with the type of tablet in mind. The die is composed of two punches, one lower and upper. The powder is then overfilled on the die table to ensure the die cavity is completely filled.

Metering

The metering stage is concerned with the removal of the excess powder granules from the compressing region.  The exact weight and volume of the granules to be compressed into tablets is determined by the height of the lower punch in the die. A metering cam in turn controls the height of the lower punch. The lower punch is raised to the appropriate height in the die to provide the exact volume of granules in the die cavity, and thereafter the excess granules are scraped from the surface of the die table.

Compression

The compression stage compresses the powder granules into tablets. This involves bringing the upper and lower punches together under pressure to form the tablet shape.  As the granules move from the metering cam to the compression region, the punches move between two large pressure rollers that resemble wheels. These rollers push the punches closer together and thereby raising the pressure to form the tablet. The distance between the punches determine the thickness and hardness of the resulting tablet.

Ejection

The ejection stage of the compressing process involves the removal of the tablet from the lower punch die. In this stage the upper punch retreats from the die cavity and rises above the die table. When this happens, the lower punch rises, pushing the tablet out of the cavity and onto the die table surface. A scraper then pushes the tablet off the die table and away from the compression region into the collection container.

The best pill presses around:

  • TDP 5 pill press
  • TDP 0 pill press
  • TDP 1.5 pill press

In the manufacturing process of tablets/pills it is essential to select the most efficient pill pressing machine. By selecting the proper machine it will ensure cost effective production of the tablets. When selecting the pill pressing machine the aim should be to improve with the following characteristics:

  • Minimize the production cost
  • Ensure the required powder content for the process
  • Tablets should be easy to administer and swallow

The pill pressing machines can be categorized into 4 main types depending on the shapes of dies and punches –

  • Round shape die and punch set – these are found mainly in pharmaceutical and veterinary industries.
  • Oval shape die and punch set – these types can also be found in pharmaceutical applications.
  • Capsule shape die and punch set – these types of sets are found in pharmaceutical industries.
  • Geometric shape punch and die set – these types are applicable in confectionery, chemical and metallurgy industries.

The pill pressing process is not without its faults and the following is a set of problems and troubleshooting methods:

  • Capping – this is when the upper and lower segment  of the pill separates dring ejection or during handling.
  • Chipping – this occurs when the edges of the tablet breaks while it leaves the die.
  • Cracking – This is when small but observable cracks appear on the lower and upper central surface of the tablets.

The problems encountered by the pill pressing machine can be fixed by doing the following:

  • Polishing dies properly, and using flat punches
  • Reducing speed and increasing pressure.
  • Reducing depth and sharpness.