Frederik Detobela, Martin Bennettb, James Holmanc
a GEA Process Engineering nv, Halle, Belgium
b Huxley Bertram Engineering Ltd, Cambridge, United Kingdom
c GEA Process Engineering Ltd, Eastleigh, United Kingdom
During compression on a conventional rotary tablet press, the distance between the compression rollers remains fixed during compression. Any variation in tablet weight will therefore result in a variation in compression force, while the thickness of the tablets remains about constant (=“equal thickness tableting”). In addition to this compression method, the GEA compression machines have the option to compress tablets at equal force thanks to the use of air compensators on the top compression rollers. Using the latter compression method, any variation in tablet weight will result in a slight variation in thickness, while the density of the tablets remains about constant. This technology can hence be used to reduce hardness variation between tablets, thereby also reducing the risk of under- or over-compressing tablets and the associated effect of sticking or capping. The roller displacement technology also allows for a dual tablet control, where tablet weight and hardness are controlled by the press in an independent manner. In addition and as a side effect, roller displacement increases the load rate and prolongs the compression dwell time which in turn may have a positive effect on powder de-aeration and on the compressibility of visco-plastic products.
The goal of this study is to evaluate whether the advanced compression methods of the GEA compression machines can be accurately mimicked on a compaction simulator. To be able to simulate the effect of an air compensator, the compaction simulator should be able to switch from a displacement-based control to a force-based control within a single compression event. Thanks to its fast hydraulics, the latest generation of compaction simulators of Huxley Bertram has this capability.
In the presented study, a direct comparison is made between the compression profiles and resulting tablet properties generated on a ModulP rotary tablet press (GEA) and a HB50 (Huxley Bertram), mimicking the same press. The most relevant process variables like pre-compression force, pre-compression roller displacement, main compression force, main compression roller displacement and turret speed were varied for a set of products with different deformation characteristics and the resulting force and displacement curves were analysed. A good correlation was obtained between the compression profiles and tablet properties generated on the HB50 and Modul P. The HB50 was capable of mimicking the advanced compression modes of the Modul P tablet press, even at rotation speeds up to 100 rpm (corresponding to a linear speed of 1.5 m/s).
Biosketch: Frederik Detobel
Dr. Frederik Detobel is a process engineer at GEA Process Engineering and has nine years of experience in tablet compression. More recently, he also gained expertise in tablet coating. As a subject matter expert within the R&D team of the pharma division of GEA, Frederik is mainly focusing on the equipment-related challenges of the tablet compression and coating process.
Since 2005, Frederik holds a Master degree in Bio-engineering from the Vrije Universiteit Brussel and in 2010, he received a PhD in chemical engineering on the topic of on-chip chromatography.