Comparative Study of a Novel Micro-feeder and Loss-in-weight Feeders

Purpose: Accurate and reliable feeding of small quantities of powder is crucial in many industries. It is particularly true in the case of pharmaceutical manufacturing. First, the exact dosage of highly potent active pharmaceutical ingredients (APIs) is essential. Second, due to the shift towards continuous manufacturing, processing agents must be supplied continuously. Last, with regard to personalized medicine products, small doses of API have to be processed with high flexibility. In all these applications, a few grams of powder or less per hour have to be fed, which makes processing very challenging. The common route of pre-blending causes additional effort in processing and quality control compared to direct continuous feeding, while material properties influence the performance of conventional feeders with conveying screw elements. Methods: In this study, a novel micro-feeding system based on active volumetric displacement is investigated and compared to commercial LIW feeders of various scales. In the micro-feeder, the powder is filled into a cylindrical cartridge and pushed towards the process by a piston in a controlled manner. Tests are carried out with a free-flowing grade of lactose and croscarmellose sodium as an example of cohesive powder. Results: At feed rates of a few grams per hour, for the investigated materials, the system has at least the same performance as conventional feeders at significantly higher feed rates. Especially at low feed rates, less fluctuations are obvious and accuracy and precision of the micro-feeder are at the same level as for the established feeding technology at rates ten times higher. Conclusion: For the two types of investigated materials (free-flowing and cohesive), the micro-feeding system shows similar or better performance than conventional and commercially applied LIW feeders. The technology offers the potential for highly accurate, continuous feeding in the low-dose range.