Press forming is one of the most suitable paperboard converting techniques to produce deep trays. However, during the forming, severe deformations occur in the tray corners, which can cause cracks and other defects that deteriorate the tray. Formability can be enhanced with creases which assist the folding of the paperboard blank. In this paper, we study the press forming process with the aid of finite element simulations. We focus especially on the effect of creases on the formability. The effects of different materials are also compared. The finite element model consists of a male die, female die, blank holder and paperboard blank. The paperboard is modeled as an orthotropic elastoplastic material. Hill's yield criterion with isotropic hardening is used to define the plastic behavior. Hinge connector elements are used to model the creases. The modeling is complemented by experimental studies. The results obtained from the finite element analysis show that high localized strains occur in paperboard tray corners during forming and that the intensity and areal size of the strains can be decreased with creases. It is concluded that the developed model can be used to compare different crease patterns which, in turn, enables better crease pattern design.
- Finite element method
- Press forming