Tablet compression experts at GEA are often asked how many punch stations their tablet presses have. It’s a good question, of course, and an important number; it helps to determine how many tablets per hour can be produced on a given piece of equipment.
But there’s more to output rates than just the number of punches. The properties of the feed material are, in fact, more important and, for most pharmaceutical applications, actually determine the tablet production rate.
In a perfect world with flawless feed materials, the number of tablets that can be produced per hour can be derived from the following equation: number of punch stations x maximum revolutions (usually 120 rpm) x 60 minutes.
In reality, however, it’s extremely difficult to operate even relatively small presses at maximum speed. Doing so leads to unacceptably high weight variations caused by the limited flow properties of the feed material. This can usually be addressed by running the press at a slower speed. In technical terms, the linear speed at which the dies move is reduced, which means that they spend more time beneath the filling unit.
Flow capacity versus speed
If the same formulation is used in a larger press with more punch stations, the flow capacity of the feed material will still influence the maximum speed. In fact, the larger press will have to be operated at the same linear speed (so the die will remain under the filling unit for the same period of time).
If the distance between two consecutive dies is the same, irrespective of the size of the press, the effect of the additional punch stations is offset by the larger diameter of the rotor: a slower speed (fewer revolutions per minute) must be used to obtain the same linear speed.
The gondola metaphor
To provide an analogy, imagine a cable car system going up and down a mountain. The number of people that can be transported depends on how many places there are per gondola (single or multi-tip tooling), the distance between the individual gondolas and, finally, the linear speed of the cable. Adding extra gondolas will not necessarily increase the overall capacity of the system because the linear speed of the cable determines how fast the passengers can board and alight.
So, to increase the number of people that can go up the mountain per unit of time, we have the following four options:
• increase the capacity of each gondola (which must be compensated by reducing the linear speed)
• alter the design: introduce double-level gondolas with two entry and exit levels, for example
• improve the “feed material,” so that only athletic people who can get in and out of the gondola very quickly are transported
• reduce the distance between the gondolas
Similarly, perhaps, to produce more tablets, the following options exist:
• introduce multi-tip tooling
• use a double-sided rotary press
• improve the feed material
• reduce the distance between the dies.
GEA has pioneered tablet compression technology for more than 100 years, driven by a passion for excellence. It has enabled pharmaceutical and industrial companies to prosper, produce extraordinary products and change people’s lives.
Its innovations include a technology that independently and simultaneously measures and controls both tablet weight and hardness, and a weight control system that provides increased sensitivity at lower forces. Its presses offer an extended dwell time – up to 300% – resulting in higher outputs and enhanced productivity. And that’s just the tip of the iceberg.
Customers benefit from technology advances and industry expertise
To meet its customers’ production challenges, the company has developed a higher level of understanding of ingredient and manufacturing variables. And by implementing the philosophy of Six Sigma to reduce critical process variation and lean manufacturing to eliminate waste, its technologies and expertise can help its clients to produce a better quality tablet, reduce the risk of product failure, improve their cash flow and increase their bottom line profit.
Contact its experts directly to discover how GEA’s products, processes and solutions can help to improve all aspects of the tableting production process.
Dr Harald Stahl is with GEA. www.gea.com
