Automation of a dosing-disc capsule filler from the perspective of reliability and safety

Abstract

The aim of this paper is to explore the possibility to develop an automatically adjustable, reliable, and safe capsule filling operation. Process parameters that are critical for the tamping pin process were reviewed based on the literature and via experiment. Dosing disc height, powder bed height, machine speed, pressure on the tamping pin, and immersion depth were reviewed. Two investigations were performed on a GKF 702. In the first one, the powder feed rate onto the dosing disc was examined and modified. A distance sensor with a PID controller enabled a constant powder bed level with an online changeable set point. For a bad flowing product an improvement of the fill weight variation could be achieved by automatically adjusting the feed rate to the correct speed and matching the actual process conditions of the capsule filler. The second part of the study concerned the safety of the filler operation. Introducing a force transducer on the transfer station is a promising option for running the capsule filler safely within its process specifications. The tamping pin pressure was used to provoke different transfer forces. A deviation from a defined process specification led to a safe stop of the machine. In summary, the automated adjustment of several critical process parameters appears to be feasible and supports the rational development of efficient production processes using a dosing disc capsule filler. This is especially relevant for continuous production of pharmaceuticals.