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A Guide to Tablet Presses

August 16, 2021

Tablet presses are machines designed to compress pharmaceutical powders and granules into tablets. They must be highly precise in order to create uniform tablets that each contain the same amount of active pharmaceutical ingredients and excipients. This page will cover some key essentials that you need to know about these vital machines.

Importance of Tablet Presses in the Pharmaceutical Industry

The pharmaceutical industry manufactures vast numbers of tablets every day, and the safety of patients can depend on the uniformity of each dosage unit. As such, the precision capabilities offered by modern tablet presses are invaluable for pharmaceutical companies.

Types of Top Tablet Presses

While most tablet presses function similarly in principle, the method of compression varies slightly depending on the type of press. There are two different classifications of tablet press machines: single punch presses and multi-station/rotary presses.

Single Punch Presses

Single punch tablet presses, also known as eccentric or single station presses, are the simplest form of tablet press. They utilize a single station of tooling that is composed of a pair of upper and lower punches and a die. For this type of press, the lower punch remains stationary while the upper punch exerts the entirety of the compression force to create the tablets. Due to their hammer-like motions, single punch tablet presses are categorized as a stamping process.

Multi-Station/Rotary Presses

Unlike single-punch tablet presses, rotary tablet presses contain multiple tooling stations. As the turret in which these stations are installed rotates, the punches move between a set of upper and lower compression rolls that exert enough compression to form uniform tablets, in large quantities. In this type of press, both the upper and lower punches move and the tablet compression occurs between the two. Rotary presses are thus categorized as a type of accordion compression.

The goal of this type of press is to increase the output of tablets. Depending on the different punch designs, rotary presses can create tablets of different shapes and dimensions.

Key Machine Parts for Tablet Presses

The two categories of tablet presses are each composed of a number of different parts. Single punch presses contain the following:

  • Hopper.The area that holds the powder mixture prior to compression.
  • Die Cavity.The area where compression occurs. Its shape determines the tablet’s size and diameter.
  • Punches.Components which compress the powder mixture.
  • Dosing plow. Pushes a small, precise amount of product into the die cavity.
  • Ejection Cam.Pushes the bottom punch upwards, ejecting the finished tablet from the die cavity.

Multi-station/rotary tablet presses have a significantly greater number of parts. In addition to the hopper, die cavity, upper and lower cam tracks, and punches, these presses contain:

  • Feeder System.A vital part of the compression process, the (normally) induced feeder system distributes product from the hopper into the die cavities, over-filling them prior to more precise control by the dosing station. Feeders are typically comprised of the exterior housing, any number of rotating, interior paddle wheels (that actually distribute the product), and a base plate.
  • Fill cams and Dosing station.Work in concert with one another to control the precise amount of product fed into the die cavities prior to compression, thus determining tablet weight.
  • Pre-Compression Rollers.Provide initial compression in order to remove any air trapped within the die cavity.
  • Main Compression Rollers.Exert the final compression force in order to form the finished tablets. Rollers must remain steady throughout the process in order to ensure tablet uniformity and repeatable quality.
  • Ejection Cam.Pushes the bottom punches upwards, ejecting the finished tablets from the die cavity.
  • Take-Off Blade.Guides tablets into the discharge chute after they have been ejected from the die cavity.
  • Discharge Chute.Directs completed tablets out of the press for collection.

Single Punch vs. Rotary Press Advantages & Applications

Each type of tablet press has its own unique advantages that make it well-suited for specific applications.

Advantages of the Single Punch Tablet Press

The single punch press is best for projects where minimal amounts of test material are available, and in cases where the user is simply looking to confirm compressibility and nothing more. They do not allow the user to replicate key principles affecting production-sized presses, such as centrifugal force, mechanical feeder behavior and dwell time. Its biggest advantages are:

  • Small size
  • Ease of operation
  • Low noise levels
  • Compression feasibility

Advantages of the Rotary Tablet Press Machine

Rotary tablet presses are ideal for applications requiring high batch production, as their design allows for significant output and precise control. Advantages include:

  • Ability to independently control weight, thickness and hardness of tablets, if equipped with available peripheral devices
  • The capability to produce up to 1,000,000+ tablets per hour, depending on press size and tooling configurations.
  • Ability to precisely control and manage the filling of die cavities, via an induced feeder
  • Interface capability with in-house network systems, for remote monitoring and data archiving
  • Greater cost efficiency than single punch presses

Rotary presses can essentially meet most tablet batch requirements in pharmaceutical, nutraceutical, confectionery and veterinary applications. They are also used with surprising frequency to produce catalysts, ceramics, powdered metals and other materials deemed suitably compressible.

Importance of Quality Spare Parts

Given the sheer capabilities of modern tablet presses, including not only the forces they generate but also the speeds at which they are typically operated, they include many components that require periodic replacement (i.e. “wear” parts). The quality of the parts used when replacing those at the end of their useful life is directly correlated with the machine’s long-term efficacy, and life expectancy.

Parts like punches and dies are particularly important, as they determine not only the size, shape and appearance of the tablets, but also the key attributes referenced earlier: weight, thickness and hardness. High quality tooling, and good preventive maintenance programs ensuring the same, are critical.