Determination of the required punch force in hemming

Hemming is a mechanical joining process by folding, which is usually accomplished in three steps, i.e. flanging, pre-hemming, and hemming. In both of designing and operating the hemming machine, the information about the required punch force is important. It has been a rather experimental one so far. In this paper, the required punch force for hemming of a front door in passenger car is obtained by finite element analysis using MARC. In the analysis, the friction between the punch and the sheet metal is considered. Effect of the thickness of a sheet metal on the punch force is examined for some possible combinations of thicknesses.