Simulating Motion of Toner Using the Discrete Element Method

Abstract

The Discrete Element Method (DEM) is one of the most popular and powerful tools for simulating the motion of granular materials. However, the traditional DEM focuses only on cohesionless granular materials; that is, materials whose motion is dominated by extra forces without significant influence of particle to particle attractive forces. For this reason the DEM approach has seen limited application in the study of toner. This study, however, proposes a numerical DEM model that incorporates cohesive forces, namely Van der Waals' and electrostatic forces, in the study of toner movement. Van der Waals' forces are those which exist due to the polarization of molecules in the toner particles into dipoles of positive and negative charge. Electrostatic forces exist between charged particles such as toner and are directly proportional to the magnitudes of the charges and inversely proportional to the square of the distance between them. The DEM model was decomposed into three sub-models, and these decomposed sub-models were validated separately by comparing the simulation results with experimental results. Finally, the model was used to simulate the motion of toner in the developer nip of an electrophotographic imaging process. The simulation results were compared with experimental results, and the simulation results fit very well with experimental results. This work shows that it is possible to achieve quantitative agreement between DEM simulations using cohesive forces and experimental results.