Issue link: http://www.e-digitaleditions.com/i/769284
Tablets & Capsules January 2017 32C But don't settle for a trial-and-error approach. Specifying tooling that way is expensive and time consuming. Instead, consider using a predictive coating model [5] that takes the guesswork out of tooling selection. It does so by taking into consideration the properties of the active ingredient(s) and excipients, as well as the effects of Van der Waals forces, capillary action, deformation mechanics, the compression environment, and the chemistries of different coatings. If sticking is the problem, for example, our proprietary predic- tive approach can identify which coating will best prevent your formulation's particle from adhering to the punch face. Design details Tablet design also affects susceptibility to wear, and a good design helps maintain high overall quality. If the tablet requires a punch with a deep concave face, it will wear quickly around the steepest areas because, during compression, the granules will tend to move laterally across the concave area and erode the tip face. That can lead to capping and delamination. In such cases, consider using a flatter tablet profile or one specially designed to reduce the effects of abrasive wear. Using a compound radius is often helpful. Also consider the gap between the periphery of the punch and the die wall. If abrasive particles get sandwiched there, they'll accelerate wear of both the die bore and punch tip. That can cause wear rings to form in the die, and the concave face of the upper punch will gradually curl inward to form a claw, causing flashing. T&C References 1. HPG-P from I Holland, Nottingham, UK. 2. HPG-TC from I Holland. 3. HPG-MP and HPG-MD from I Holland. 4. PharmaCote RS from I Holland. 5. TSAR Predict from I Holland. Michael Oxford is a research and design engineer at I Holland, whose US distributor is IPR, 1241 Hardt Circle, Bartlett, IL 60103. Tel. 630 823 4700. Website: www.tablettingscience.com. The company supplies compression tooling and accessories to the pharmaceutical and nutraceutical industries. A vitamin tablet containing abrasive and coarse ingredients This punch tip shows severe abrasion. A steel punch without coating (left) can wear quickly. With the addition of a resilient coating (right), the punch can last more than 900 percent longer. Granules tend to move laterally across a deep concave punch during compression (left). To reduce abrasive wear, consider using a flatter tablet profile (right). Further reading For more information about using tooling design and coatings to combat wear, see "Overcoming manufacturing challenges of nutraceutical tablets," in the January 2014 issue: bit.ly/TC0114NutraTablet.