In tableting it is common to compare different compression conditions by using the dwell time. By definition, this is the time in which the flat part of the punch head passes the compression roller.
Neither the tablet output per hour nor the turret speed can be used for different sized tablet presses because the number of punches and the pitch circle diameter are different.
A better way to ensure comparable tableting conditions is the dwell time which is calculated by the flat part of the punch head, the turret speed and the pitch circle diameter.
But sometimes during transfer or scale-up out-of-spec tablets are produced even when taking the dwell time into account.
There are many reasons for this like filling and the exact dimensions of the tablet press. Nevertheless, the dwell time is a good staring point when changing or comparing tablet presses.
Dwell Time (msec) = [flat part of punch head (mm) / {turret speed (rpm) × 60 × pitch diameter (mm)}] × 1000
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