Simulation of die filling for powders with complex rheology
Die filling is the first step of the powder technological process chain which is followed by the subsequent steps of compaction, debinding, and sintering. Due to the complexity of these steps, defects can occur during the process chain, which may evolve to excessive variations in the final stages and lead to off-specification batches and severe waste of resources. The process of die filling is of particular importance, as it defines the starting conditions of the follow-up processes. An inhomogeneity in the powder distribution can lead to warpage during sintering or inhomogeneous final properties. Therefore, understanding and controlling the die filling process is a key requirement for the optimization of the process parameters such as shape, acceleration and speed of the shoe. Predicti ve modelling of the complete die filling process, including effects of powder handling history on the rheology can immensely assist in optimizing the whole manufacturing process and reduce costs. Numerous studies employing the discrete elements method have been done in the past. However, the vast majority of these studies assumes rather homogeneously flowing powders and excludes effects like sticking, caking, and flow separation. In this work, we will demonstrate the application of enhanced contact force models to die filling process simulations, which is an important step towards the predictive simulation of the filling behaviour of powders with unfavourable flow properties as an engineering tool in the process development.