Tablet Compression - How it works

The tableting process can be broken down into 4 parts.

The Filling Stage A powder mixture is added into the hopper which flows down into the fill tray whilst the lower punches are pulled downwards by the fill cam. The powder then falls into the die bores by gravity. On some tablet presses, a force feeder is used which moves the powder over the top of the die to fill the die bores more efficiently.

Metering, next the lower punches, will move over the metering cam, sometimes known as a dosage cam or weight adjustment cam, this will move the lower punches upwards to remove excess powder out of the die bore. The amount of excess powder will depend on the weight you’ve set your tablet press.

The excess powder is scraped off the top of the die flat and will stay in the fill tray. The purpose of metering is to set the exact amount of powder to be formed into a tablet ensuring your tablets are a consistent weight.

Compression The punches now move around to the compression stage. This is where both the upper and lower punches are brought together under high pressure to form a tablet. Both upper and lower punches move between two compression rollers which bring them together and compress the powder.

The pressure is adjusted by the technician which will determine the thickness and hardness of your tablet. If the punches are brought closer together the tablet will be harder and thinner, if they’re further apart the tablet will be thicker and softer.

Every tablet mix is different so your tablet press will have to be tuned to your mix, this is a process that should be done in small increments. Ejection Once your tablet has been formed inside the die, The upper punch is lifted out of the die bore by the upper tracking whilst the lower punch will go over the ejection cam.

The lower punch is raised in the die bore until it’s flush with the die, this pushes the tablet out of the die and flush with the die table. The table then rotates and pushes the tablet into a scraper, often known as the takeoff scraper which will move the formed tablet down an ejection tray into a container or the next stage of the process. Additional equipment may be used alongside a tablet press such as a tablet deduster to de-dust your tablets. A metal detector to detect metal inside the tablet or a tablet weight checker to ensure your tablets are staying a consistent weight.