Evaluating and modifying Johanson's rolling model to improve its predictability.

The purpose of this study is to investigate if Johanson's rolling theory can correctly predict the maximum roll surface pressure during the roll compaction. Three model pharmaceutical formulations were roller compacted using the Gerteis Mini Pactor at multiple combinations of roll forces and roll gaps. The resultant ribbon density at each combination of roll force and roll gap was measured and the corresponding maximum roll surface pressure was predicted using Johanson's rolling model. The measured ribbon density and predicted maximum roll surface pressure from roller compactor was compared with the measured wafer density and maximum axial stress from die compression. The results indicate that predicted maximum roll surface pressure from roller compactor is higher than the axial stress from die compression to manufacture same density ribbons. The root cause of overprediction of maximum roll surface pressure from Johanson's model was found and corrected. The modified model offers reasonably accurate prediction of maximum roll surface pressure for all roller compaction experiments conducted in this study.