TABLETING AND LAB CONSUMABLES
Extended head flat vs. standard head flat
Pressing
Power C
speed, the pitch circle diameter of the turret, and the head flat’s diameter (Figure 1). Increasing the diameter of the head flat is the easiest way to prolong dwell time without switching
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A guide to understanding how head dwell time can impact tablet compression
ompressing difficult tablet formulations can be achieved via a range of punches or dies. One punch modification,
the extended head flat, increases the diameter of the flat area atop the punch head. Typically, this doesn’t require any modifications to the press, and it can be used with cam tracks to meet the Tableting Specification Manual (TSM) or European Union (EU) standards. Dwell time is dependent on press
to a press with a smaller turret pitch circle and generally with fewer stations, or without decreasing the turret speed, both of which would decrease production. For example, a Fette 2090 press has a pitch-circle diameter of 410 mm, and assuming an operating speed of 50rpm, a standard B-type punch, TSM domed head flat of 9.525mm (0.375in) would have a dwell time of 8.87 milliseconds.
B-TYPE PUNCH WITH TSM DOMED HEAD Meanwhile, on that same press, a B-type punch with TSM domed head with extended head flat (13.59mm, 0.535in) would have a dwell time of 12.66 milliseconds (Figure
2). Figure 3 illustrates the differences in dimensions between a standard B-type TSM domed head and TSM extended domed head. The larger head flat increases dwell time by more than 43% without reducing the turret speed. The extended head flat punch can
also reduce the amount of compression force needed to form a tablet at a given breaking force, also known as hardness. Tablet hardness and density are related to both compression force and dwell time. If the amount of time spent under compression increases, the amount of force necessary to maintain the same tablet hardness may decrease. The reduction in required compression force depends on the characteristics of the granulation being compressed. Since the required compression
force is dependent on the product being compressed, it’s impossible to
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