TM2 NO-NONSENSE TOOL INSPECTIONS [PDF Version]

With every measurement you include in your inspection SOP, the FDA may want see evidence of: training; validation; calibration; etc. In other words, why open a can of worms? The TM2 system recommends that you ONLY INSPECT CRITICAL DIMENSIONS!

The following represents the recommendations of Natoli Engineering Company, Inc. for the proper approach to dimensional inspections of upper and lower punches in order to assure tablet quality. The recommendations are based on dimensions that provide consistency with regard to tablet hardness, weight and thickness.

Punch Inspection Critical Dimensions – We believe there are three (3) critical dimensions that should be included in a dimensional inspection of an upper or lower punch. Measuring any other dimension is either A) unnecessary because it rarely, if ever changes and therefore is not worthy of the time and expense of measuring or B) cannot be properly measured with current equipment and is better served by a visual inspection.

The three (3) critical dimensions include the following:

1.) Working Length – The working length is the most critical punch dimension because it determines tablet thickness and hardness. Tolerances should be based on the measurement of a punch in relation to other punches as opposed to being based on a specific length. Uniformity of punch working lengths is the key. In other words, as long as the punches are the same length (or within the specified tolerance) it doesn’t matter how they compare in relation to a specific pre-defined length.

2.) Cup Depth – To find the cup depth, subtract the measured working length from the measured overall length. Cup depth is not a critical dimension with regard to controlling tablet weight.

3.) Overall Length – The overall length is not critical except that it is necessary to accurately calculate Working Length and Cup Depth. In other words, you should not always assume a 5.250” overall length measurement.

For additional reference, please see the “Encyclopedia of Pharmaceutical Technology” Volume 15 pp. 168 –169 and “Tableting Specification Manual” Sixth Edition pp. 13, 14 & 15.

We hope this will be of help to you in understanding our recommendations with regard to dimensional inspections of upper and lower punches. Please feel free to call us if you have any questions.