Seven Steps to Solving Tabletting and Tooling Problems---Step 4: Measure

The PharmaCare seven-step process is a logical, planned, and professional approach to tooling maintenance, measuring, and storage that has been adopted by many companies as a standard operating procedure. Over the last three weeks, we have been looking at each step and the benefit of adopting the process. This week, we look at Step 4, Measure.

Step 4: MEASURE 
Measuring is essential after repair to ensure that critical tooling dimensions have been maintained within an acceptable working tolerance. The equipment for measuring can range from simple hand-held micrometers, vernier callipers, and height gauges, to semi-automatic, computerized digital gauging systems. One such tool is the Holland Die Condition Monitor (HDCM), which can measure  the condition of die bores, ensuring that optimum life is achieved from the dies to prevent the production of damaged tablets. Die bore wear, or ‘ringing,’ is a common defect that can lead to problems, such as tablet ‘capping’ and tablet ejection issues, which result in wasted product and reduced tablet output. Ringing is caused by abrasive wear and deformation from continuous forces acting on the face of the die bore. This is accelerated when compressing hard and abrasive granules found in some formulations, particularly vitamins and minerals. This wear can be identified using visual assessment, but precise equipment should be used to measure and monitor this wear. This physical die condition monitoring can result in early diagnosis before the defect has a negative effect on tablet output.
Measuring should be carried out at regular intervals (even if repair has not been necessary) to check for natural wear during the compaction process. The essential measurement is the critical working length of the punch, as this controls tablet thickness, weight, and ultimately, dosage. The control of tablet weight and thickness is important as these parameters influence the thickness of the tablet ingredients, and one of the most common causes of tablet weight/thickness variation is inconsistent punch lengths. The critical working length of the punch can be easily measured and monitored to ensure consistency across the tool set. Any slight variations from the tolerance range can be addressed using the repair equipment to bring the lengths into range.

By following the previous steps in the process, including Clean,Assess, and Repair, measurement of the critical working length during Step 4 ensures that the punches are within an acceptable tolerance range for good tablet weight and thickness control. Importantly, as the punches are already clean and assessed, outside influences to measurement, such as oil or compacted granule on the punch tip face, will not interfere with measurement data.

Andy Dumelow is PharmaCare manager at I Holland.