1. Working Length
Working length is one of the most important punch dimensions, especially in rotary tablet presses. It directly affects tablet weight, hardness, and thickness. A variation greater than 0.0508 mm between upper and lower punches can lead to inconsistencies. Regular measurement of both in-use and new punches helps maintain uniformity and compliance.
2. Die Bore Wear
Die bore wear is often overlooked but can cause tablet defects such as capping, flashing, or lamination. Using advanced inspection tools like a Tooling Condition Monitor allows you to detect wear early, track changes over time, and prevent production issues.
3. Punch Tip and Cup Wear
Punch tip wear, particularly the common “J-hook” condition (where the edge of the punch curls inward), can cause defects like picking and sticking. Since standard micrometers cannot capture this wear accurately, use optical comparators or monitoring systems to identify and resolve issues before they affect batches.
4. Punch Retainers
Worn punch retainers lead to variations in tablet weight and inconsistency during compression. Regular inspection and timely replacement ensure stable punch alignment and prevent unnecessary weight variation.
5. Pressure Rolls
Pressure roll wear or run-out results in differences in tablet hardness and weight. A dial indicator is recommended to measure roll wear and verify that tolerances are within acceptable limits, ensuring proper compression force.
6. Cam Track Wear and Depth of Fill
Cams determine punch motion and fill depth. If worn or improperly set, they result in material waste and weight variation. Conduct both visual inspections and detailed maintenance checks to ensure accurate tablet fill and consistent quality.
7. Ejection Cams
Improperly aligned ejection cams can chip or damage tablets during ejection. Using a straight edge, confirm that the punch tip aligns smoothly with the cam to ensure trouble-free takeoff from the die.
Final Thoughts
A structured inspection routine is essential for pharmaceutical manufacturers aiming to improve tablet quality, reduce defects, and extend tooling life. By monitoring these seven areas—working length, die bore, punch wear, punch retainers, pressure rolls, cam tracks, and ejection cams—you can significantly enhance efficiency and maintain consistent production standards.
