The development of an instrumented tamp-filling capsule machine II - Investigations of plug development and tamping pressure at different filling stations

A previously described [Eur. J. Pharm. Sci. 10 (2000) 267] pneumatic tampin g head with attached instrumentation, capable of recording tamping forces g enerated on a Bosch GKF tamp-filling machine with high precision was employ ed to investigate the development and density of plugs during capsule tamp- filling of two soft, ductile powders. The study aimed to make a contributio n to control capsule fill weight by monitoring the tamping force. The resul ts indicated that the tamping station utilised to measure the tamping force and that involved in the regulation of the pressure of the pneumatic chamb er of the tamping head should preferably not be the same. A possible soluti on would be to install the instrumented pneumatic tamping head on tamping s tation 4, after which in all cases plugs had formed to their maximum length and density. A second pneumatic tamping head, without instrumentation, cou ld be installed on tamping station 3, which would receive signals from the instrumentation, and as a result the inner chamber pressure of this second pneumatic tamping head could be changed to adjust fill weight. The cumulati ve tamping distance should be large enough to produce a force reading well above the limit set by the inner chamber pressure, but small enough to avoi d overfilling of the capsules. The latter can be detected monitoring the va riability of the tamping farces recorded. A larger standard deviation of th e tamping forces obtained from tamping station 4 was found to be a strong i ndicator of overfilling. (C) 2001 Elsevier Science BN. All rights reserved.