Comparison of calculated and experimentally determined punch displacement on a rotary tablet press using both Manesty and IPT punches.

An indirect method of calculating punch displacement on a rotary tablet press from measurements of the change in punch force with the turret position was in good agreement with direct measurements of punch displacement made using a linear variable displacement transducer (LVDT)-slip ring system. The direct measurements were made during the compaction of three direct compression agents using Manesty punches. However, the agreement between calculated and experimentally determined punch displacements was unsatisfactory when IPT punches were used. The IPT punches have a much flatter punch head profile than the Manesty punches. Due to this difference, the analytic equation does not accurately describe the dynamics of the press under normal operating conditions. Terms in the analytic equation, determined originally under static conditions, were re-evaluated under dynamic conditions for both sets of tooling using the LVDT-slip ring system. Excellent agreement for both IPT and Manesty punches was found between punch displacement calculated using the revised analytic equation and direct experimental measurements. Punch displacements determined from punch head profile and machine geometry only, without taking machine deformations into account, were shown to differ widely from the calculated and experimental values.