Accuracy of model force prediction in closed die coining process

In micro-forming processes, such as coining, the microstructure of the material and dimension scale of the coined geometry can have a substantial influence on the mechanism of material deformation. The influence of the grain size on the coining force and closed die filling is investigated experimentally, and a mathematical model for result prediction has been created according to the obtained experimental results. The material of the billet is 99.5 % aluminium, and the die geometry is relatively complex. The presented mathematical model takes into account the influence of size effect on the material flow curve through die cavity geometry and estimates the final coining force and corresponding associated displacement of the tool. This enables a controlled influence of the grain size of the specimen material on forming force and tool displacement in the coining process and a reliable prediction of the final coining force and related tool displacement associated with a completely filled die cavity. To determine the accuracy of model force prediction, the experimental and modelled data were statistically analysed and graphically presented.