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Open AccessArticle

The Challenge of Die Filling in Rotary Presses—A Systematic Study of Material Properties and Process Parameters

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Institute for Particle Technology, Technische Universität Braunschweig, Volkmaroder Str.5, 38104 Braunschweig, Germany
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Center of Pharmaceutical Engineering (PVZ), Technische Universität Braunschweig, Franz-Liszt-Str. 35A, 38106 Braunschweig, Germany
*
Author to whom correspondence should be addressed.
Pharmaceutics 2020, 12(3), 248; https://doi.org/10.3390/pharmaceutics12030248
Received: 25 February 2020 / Revised: 3 March 2020 / Accepted: 5 March 2020 / Published: 10 March 2020
(This article belongs to the Special Issue Powder Processing in Pharmaceutical Applications)
For the efficient and safe production of pharmaceutical tablets, a deep process understanding is of high importance. An essential process step during tableting is the die filling, as it is responsible for a consistent tablet weight and drug content. Furthermore, it affects the results of subsequent process steps, compaction and ejection, and thus critical quality attributes. This study focuses on understanding the influences of process parameters and material properties on die filling on a rotary tablet press. By the systematic variation in process parameters as the turret and paddle speeds as well as the fill and dosing depths, five formulations with differing properties are processed. Analysis of the normalized tablet weight, called filling yield, revealed different limitation mechanisms of the filling process, i.e., incomplete filled dies for certain parameter settings. Kinetic limitations occur due to a short residence time under the feed frame (filling time) caused by high turret speeds, which additionally induce high tablet weight variation coefficients. Characteristic maximum turret speeds at certain paddle speeds can be found to still achieve complete filling. At low turret speeds, densification of the powder inside the dies takes place, induced by two mechanisms: either high paddle speeds or high overfill ratios, or a combination of both. The challenge to fill the dies completely as well as avoid densification is dependent on material properties as the flowability. The mass discharge rate from an orifice was found to be in a linear correlation to the filling results of different formulations below complete filling. View Full-Text
Keywords: tableting; die filling; rotary tablet press; process understanding; paddle feeder; turret speed; paddle speed; filling efficiency; kinetic filling limitations; densification tableting; die filling; rotary tablet press; process understanding; paddle feeder; turret speed; paddle speed; filling efficiency; kinetic filling limitations; densification
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MDPI and ACS Style

Schomberg, A.K.; Kwade, A.; Finke, J.H. The Challenge of Die Filling in Rotary Presses—A Systematic Study of Material Properties and Process Parameters. Pharmaceutics 2020, 12, 248.

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