Issue link: https://www.e-digitaleditions.com/i/648486
or ceramic. (Ask your tooling vendor to recommend ways to combat troublesome products.) These options can also reduce the amount of force required to eject tablets from the die, which will reduce friction, minimize premature cam wear and, most importantly, improve tablet quality by reducing sticking to the lower punch cup, chipping at tablet take-off, and tablet lamination. Inspecting the dies begins with a visual check for wear rings (photo). While you can unusually see a wear pattern with the naked eye, you'll need a tool to determine the extent of wear. Options include a split-ball bore gauge con- nected to an indicator and a digital handheld gauge. The amount of allowable deviation within a die bore depends on the characteristics of the powder, which varies from product to product. If, for example, you know that a wear ring of 0.004 inch doesn't prevent you from manufac- turing a quality tablet—perhaps with a bit of flashing but no negative effect on the tablet press—then you may deem that amount of wear acceptable. However, if a split-ball gauge shows that the wear exceeds that tolerance, then the best option is to replace the die. Should wear occur high enough in the die, it's possible to flip it over and compress tablets in its other half. Keep in mind, however, that if the die has a single taper, flipping it over either won't work or will lead to tablets of poor quality and/or other production problems. Last, don't wait for problems. By checking punch and die wear regularly, you'll spend less money replacing tools and less time fighting production issues. For the best results, write your inspection procedures into your SOPs so that everyone inspects the tools in the same way and uses the same criteria to make decisions about repair and replacement. T&C Further reading 1. Understanding the importance of punch length and cup depth. Dale Natoli. Tablets & Capsules, July 2006, pp. 40-3. 2. Maintain tablet quality by inspecting these critical points. Stephen Natoli. Tablets & Capsules, April 2014, pp. 33-5. 3. Cup depth and tablet consistency. Dale Natoli. Tablets & Capsules, July 2015, p. 44. Stephen Natoli is replacement parts and catalog manager at Natoli Engineering, 28 Research Park Circle, St. Charles, MO 63304. Tel. 636 926 8900. Website: www.natoli.com. The wear pattern in a die is often visible to the naked eye, but you need a tool to determine the extent of wear. This die shows similar wear patterns at the top and bottom, indicating that it was flipped over in the die pocket to extend its service life. Tablets & Capsules March 2016 23