Pills have been produced since ancient times but the modern compressed tablet we would recognize was invented in 1843 in Britain by William Brockedon. Putting powder in a cylinder with a metal punch in the cylinder and hitting the punch with a hammer until the powder was compressed into a solid tablet. The modern tablet press is based on the same principle but mechanized.
In the late Nineteenth Century, Frank J Stokes of Philadelphia developed a rotary cam operated tablet press, at first powered with hand crank and later motorized. He invented the “B” (.75″) and the “D” (1″) tooling which became the standards still used today. As his company grew, Stokes contracted with a company in England to produce presses for the European market. When he ended his relationship with that company in the 1920’s, the British owners used what they had learned from Stokes to continue manufacturing tablet presses but under the name Manesty. After World War II, the market for tablets expanded beyond what Stokes and Manesty could accomodate and that created an opening for other companies such as Fette, Kilian and Korsch of Germany, Elizabeth-Hata of Japan and Cadmach of India to enter the field. They built presses basically on the Stokes model. A turret containing the punches and dies rotates between upper and lower circular cams which push the punches up and down creating the compression which produces the tablets.
Stokes and Manesty (Now owned by Bosch) remained leaders in the industry for decades and most of the used tablet presses on the market are either Stokes or Manesty. Some of the lower end presses on the market are quite old but the technology has not changed much over the years and the presses last a long time. It is not uncommon to find an old standby like a Stokes B2 that is 40 or 50 years old and still operational. Companies such as Natoli Engineering of St. Louis produce replacement tooling for these presses.
Every tablet press has the following features:
The cams on a standard tablet press normally produce a compaction pressure of 4 tons but some presses can be designed to have a compaction pressure of 10 tons or more.
There are single punch tablet presses, of which the Stoke F4 is a popular example, which are slow in speed but are often built for large size or specialty tablets. Even non-tablet items such as boluses for animal feed and even urinal cakes are made on these presses.
If a tablet is being made with more than one compound, such time release medicine, a multi-layer tablet presses is necessary. Most of the manufacturers have offered this as an option. If a non-round tablet, such as caplet, is being produced, the punches must be keyed to keep the correct orientation. Small tablets are normally made on a B-tooled or BB-tooled press and tablets larger than .945 inches in diameter are made on a D-tooled press. These are important factors to look for when choosing a tablet press. Sometimes tooling can be changed when a machine is rebuilt.
B-tooled or BB: less than 5/8”
D tooling : tablets sized to 1 3/16” – standard although special Slugging presses in can go to 2”
R tooling: to 4” – Bollas or Toilet deodorizers, or cosmetic compress.