Simulation of powder flow in a lab-scale tablet press feed frame: Effects of design and operating parameters on measures of tablet quality

• Powder flow in a lab-scale pharmaceutical tablet press is modeled using DEM.
• Effects of feeder design, process parameters, and powder cohesivity are examined.
• Powder flow pattern, residence times, and tablet mass variability are assessed.
• Work done on particles is used as a proxy to quantify potential particle attrition.
• Distances traveled by particles are used as a proxy for extent of lubrication.

The feed frame of a pharmaceutical tablet press is an important process component critical in defining both the total tablet mass and the amount of the active pharmaceutical ingredient (API) within the tablets. In addition to these quantities, the mechanical agitation of the feeder can cause attrition or over-lubrication of the powder blend or granulation flowing through the device. In order to better understand these effects, the discrete element method is used to model powder flow in a single paddle wheel feed frame of a laboratory-scale tablet press with varying particle, process, and equipment parameters. Results show that widely varying particle flow patterns and residence time distributions are achieved for varying paddle wheel shape, rotation direction, and rotation speed. Faster paddle wheel speeds generally lead to more uniform tablet masses whereas slower paddle wheel speeds perform less work on the particles (a surrogate for attrition) and move the particles a smaller distance (a surrogate for the extent of lubrication) in the feed frame before they enter a die and are compressed into a tablet. Finally, the effects of paddle wheel design and powder cohesion are also described.

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