Requirements and Constraints for a Robotized Roll Hemming Solution
The objective of this study is the design of a new roller hemming tool. For this purpose, main parameters affecting the final quality of the rolled hemmed part have been studied in order to identify and outline the key factors in roller design as well as in roller hemming process stages. A preliminary set of experiments has been carried out to study the pre-hemming force and springback relation in an aluminium sheet. Experiments showed the required forces in first pre-hemming stage and allowed to calculate a stiffness coefficient based on the springback deformation angle.
Influence of prestrain on the numerical simulation of the roller hemming process
Abstract This study focuses on the numerical simulation of roller hemming of an aluminium alloy sample with a curved geometry; this non-planar geometry is obtained by a prestrain procedure similar to deep drawing process. Material characterization was performed through tensile and simple shear tests at different orientations on the sheet plane. The influence of considering the Bauschinger effect, anisotropy, and the strain history on the final geometry was studied. A specific laboratory device for roller hemming was designed to forward an experimental database. The numerical simulation of the roller hemming of these samples is presented here, as well as the correlation between the calculations and the experimental tests, notably the roll-in value and the prediction of wrinkling.
Experimental investigation of forming defects in flat surface–convex edge hemming
Abstract In this paper, flanging and convex edge hemming of aluminum killed draw quality steel was investigated. The investigation was focused on the study of the radius flat hem with an inner sheet. The objective of the study was to determine the influences of the contour radius and flange length on wrinkling, hem-out, roll-in (creep or creepage) and roll-out (growing). A set of complete factorial experiments was designed and conducted in order to determine the effects of the selected experimental parameters. Experimentation provided a design map of failure zones for wrinkling and hem-out as well as fundamental knowledge of important factors in convex edge hemming and factor interactions during different process stages. Results of the experiments were summarized for the use of process and die designers. A future experimental study will focus on pure roll and warp without any wrinkling and hem-out.