How to eliminate Capping/Lamination


(Sajjad Ahmad) #1

1.Punch Penetration. Check if the tablet press has an adjustable punch penetration. Adjusting the upper punch penetration depth in the die can allow better air exhaust, which can often solve the issue quickly. The punch penetration setting for pre-compression penetration does not have to be the same as for the main compression step.

2.Pre-compression. New models of high-speed rotary tablet press incorporate pre compression, which is an initial compression step before the main compaction step. Pre-compression is a means of compact the powder but at a lighter pressure than the main compression step. It is used especially if there are dry dust fines or particles – it binds the particles together using a lighter force, so that they cannot migrate out during the final compression step. If the tablet needs more dwelling time, pre-compression can be done twice with a higher force the second pre-compression step.

3.Slow the Press Down. By decreasing the speed of the press, the dwell time or the time that the tablet is under pressure is increased. By slowing the press and extending the dwell time, air is allowed to evacuate, giving the particles time to bind themselves to each other, leading to a controlled hardness once tablets are released. It is important, however, to make sure that the dwell time is not too long as that may lead to particles becoming too dry and the tablets laminating. Clearly extending dwell time is one method of solving the capping issue but it needs to be managed so that it does not introduce a laminating issue.

4.Tooling Design. The design of the tablet tooling can influence capping and laminating. A dome headed tool can extend dwelling time and changing the cup depth and radius can help make air release faster during compression stage. Additionally, adding a taper to the die can help evacuate trapped air during compression and reduce the tendency of the tablet to cap. Tapering can also reduce the force that contributes to the tablets’ tendency to laminate. Remember that proper care and maintenance can eliminate other problems such as j-hook, compression wear rings within the die and premature punch tip wear.