A study on forming limit diagram and laminated stamping of paperboard

Abstract Coated paperboard not only has the advantages of traditional paper such as low density and cleanliness, but also overcomes its disadvantages such as poor barrier performance and sensitivity to moisture. It is more and more widely used in forming packaging containers. The current research on mechanical performance and inelastic deformation of paperboard mainly focus on its physical properties and simplified single-blank forming, but the studies on the forming limit diagram (FLD) of paperboard are relatively rare. In this paper, Nakajima tests have been carried out to determine the FLD curves of the polyethylene-coated paperboard blank along the machine direction, cross direction, and diagonal direction. A laminated stamping method for multi-blank is proposed and investigated by experiment and numerical simulation. Up to 5 blanks can be overlapped and stamped in a single punch stroke, and 5 bowl-shaped packaging containers can be formed simultaneously. Compared with the single-blank stamping process, the production efficiency can be greatly improved, but the flange area of the forming parts is easier to wrinkle. However, the wrinkling risk can still be controlled by optimizing the process parameters, such as friction factor and blank holder gap.