Uniformity of powder die filling using a feed shoe: A review

The process of die filling for achieving a uniform fill is a critical unit operation that is far from being sufficiently understood. Factors influencing powder flow from a feed shoe and powder deposition into a die are reviewed in this article. The factors include feed shoe speed, feed shoe holding time over the die, particle shape and size, powder size distribution, die shape and size, die configuration, filling intensity, filling direction, and the height of powder in the feed shoe. Devices suitable for evaluating the quality of powder deposition in dies need to be more: (1) specific to simulate the filling process, (2) versatile to encompass different filling parameters, and (3) able to provide quantitative evaluation. Recommendations to improve die deposition and density uniformity are given with respect to powder characteristics and die and feed shoe properties. New devices using load cells, pressure sensors, or tactile sensors to investigate powder deposition are important for further the investigation of the deposition process and spatial density uniformity. These primary measurement devices have the potential to bridge the knowledge gap and enable the development of discrete and/or continuum-concept computational models for the dynamic die-fill process.