(408c) Using Multi-Level Coarse-Grained Simulation for Design Studies: The Case of Tablet Press Feeder

DEM simulations often produce only qualitative predictions. One of the reasons for this limitation is the inability to use particles of appropriate size. Coarse-grained particles are used in most cases for DEM simulations to save computation time. However, a recently published method can enable us to use resolved (actual size) particles in crucial regions of the machinery and thereby obtain quantitative predictions [1].

In this presentation, we shall apply multi-level coarse-graining for simulating high speed tableting machines which are frequently used in the pharmaceutical industry. The critical quality attributes of tablets depend on various design parameters such as paddle wheel shape and feed frame design and the effect of these parameters on performance of this machine will be studied using both multi-level coarse-graining and fixed coarse-graining technique and these two will be compared.

It is observed that major change in the prediction occurs when very small particles are used in the critical region using adaptive coarse graining. However, this change does not alter the design decisions since the trend predicted by the uniform coarse-grained simulation is preserved in the multi-level coarse-grained simulations [2].

Figure 1A. shows the results for the prediction of the mean tablet mass for two different paddle wheel designs. It can be seen that like the case of fixed coarse-grained simulations, the mean tablet mass does not change significantly upon change of paddle wheel. However, the absolute value is 15% higher for both cases. Similar trend can be seen for the tablet mass variation as shown in Figure 1B. Comparisons with resolved simulations will also be shown for a few cases as shown in Figure 1.

1. T. De, J. Chakraborty, J. Kumar, A. Tripathi, M. Sen, W. R. Ketterhagen, “A particle location based multi-level coarse-graining technique for Discrete Element Method (DEM) simulation", Powder Technology, vol. 398, 117058, 2020.
2. W. R. Ketterhagen, “Simulation of powder flow in a lab-scale tablet press feed frame: effects of design and operating parameters on measures of tablet quality,” Powder Technology, vol. 275, pp. 361–374, 2015.