Issue link: https://www.e-digitaleditions.com/i/1138630
32H July 2019 Tablets & Capsules Additionally, when working with rough nutraceutical formulations, the gap or clearance between the punch-tip edge and the die bore is critical. If abrasive particles become trapped between the punch tip and the die, they'll accelerate wear of both tools. Trapped particles can create wear rings in the die bore and cause claws or j-hooks to form on the concave face of the upper punch, resulting in flashing or possible decapitation of the tablet. The correct tablet and tooling design can mitigate or even eliminate these potential problems. An expert tooling designer will be able to add appropri- ate strengthening features to the tablet design such as blended lands and profile changes, resulting in a strong tablet that can be quickly and cost-effectively produced. The land on a tablet is the flat lip or ridge around the perimeter of the tablet face perpendicular to the tablet's edge. Figure 2 shows examples of punches with and with- out lands. Often, tablet manufacturers elect not to apply a land because it is perceived to be aesthetically undesirable on the finished product. However, skillfully blending the land can minimize its visual impact on the final tablet while increasing the tooling strength and performance, resulting in higher production volumes. Incorrectly blend- ing the land, on the other hand, can result in a range of problems during compression, including chipping of the land during tablet take-off, or issues during coating, such as coating buildup on the tablet edge, which will eventually chip off. To correctly blend the land, ensure that the flat area on the tip edge is maintained while applying a radius to the intersection between the flat perimeter of the punch tip and the concave cup that forms the tablet profile. Also consider the tablet profile, especially if the tablet will be coated. Successful tablet coating is dependent on the tablet profile. A tablet is softer at its core than at its perimeter, so the core can erode during coating from con- tact with the coating pan and other tablets (Photo 2). You can prevent this weakness by avoiding tablet designs with very round profiles. This type of wear can lead to various production problems, such as the removal of details or break lines embossed into the punch cup, resulting in poor tablet definition and potential functional tablet failure. Another common issue is capping and delamination, which is when the top of the tablet separates from the tablet body after compression during ejection from the die or take-off from the lower punch. When compressing abrasive materials, consider using a flatter, shallower tablet profile such as the one shown in Figure 1b or a profile specially designed to reduce potential friction and wear. Figure 2 Punch tips with and without land No land Unblended land Land with a blended radius edge Photo 2: Core erosion is a common defect for tablets with very round profiles, especially when put under strain during coating. The tooling should be redesigned with a less concave profile to help the tablets withstand the coating process. Sign up now by emailing kmyers@cscpub.com your name, company, and email address. To see a sample, please visit our website.