Untersuchung der Tablettiersimulation mit dem PressterTM in Abhängigkeit von der Formulierung, Chargengrösse und der Tablettenpresse

After completion of the studies using the PressterTM it can be concluded that comparative
results between PressterTM and rotary tablet presses can be achieved if the compression
parameters are correctly set up. Firstly manufacturing of tablets with the same mass is
important for the comparison. In addition the studies revealed that tablets need to have the
same thickness because otherwise they were differently densified. Thickness is often
specified for packaging of tablets being an important parameter for this reason.
To achieve the same thickness the same band height needs to be set up on both tableting
machines. The PressterTM offers the possibility to measure punch displacement to find out
the actual punch gap. If tablet presses are not instrumented only the out-of-die thickness
can be measured and the band height can be adjusted accordingly.
The set up of two presses to the same compression force is not reliable because the
compression force is a result of the tablet mass and the punch gap and therefore only an
indirect parameter. Calibration of the strain gages is complicated and subject to failures e.g.
with temperature changes.
Recalibration of the PressterTM strain gages using Pfizer Freiburg calibration equipment
revealed excellent results.
When the experiments were performed using the same resulting compression force, the
band height set up on PressterTM partly deviated significantly from the band height set up
on a rotary tablet press, leading to differently densified tablets. If materials are compressed
to the same thickness different compression forces are produced depending on material
and/or batch variability. Thus the height of compression force indicates material properties
and compression force variability points out differences in material properties.
The experiments of this study confirm that precompression of the tablets is very important
regarding the tablet properties. This is even more important if materials show a high
tendency to elastic relaxation in order to prevent capping. PressterTM offers the instrumented
die as a very useful tool to measure the radial die wall pressure.
The mainly directly compressible formulations tested in this study were robust and
compressible on PressterTM and rotary tablet presses without any issues. Only at extreme
conditions: short dwell time, high main compression force and no precompression force
capping occurred with a 90 % (w/w) paracetamol containing directly compressible
formulation compressed on PressterTM simulating the IMA Comprima tablet press. As
PressterTM showed this failure it reliably fulfilled its function to indicate compression
problems.
As the goal of production is short machine run times high compression speeds respectively
medium to short dwell times were tested. No dwell time effect on the tablet properties was
detectable in the tested speed ranges.
In the current work different formulations, batch sizes and tablet presses were tested. In all
cases valuable knowledge about the properties of the tableting formulations was gained
using PressterTM. PressterTM is a useful tool to predict processibility of different formulations
on diverse rotary tablet presses and in varying production scales. The hypothesis postulated
at the beginning of this work is confirmed.