Laser Heat Treatment Effects on Roller Hemming in Aluminum Alloys

Abstract

Especially for bending/hemming operations, aluminum alloys lack sufficient formability. The aim is to use them in the same way as other structural materials such as conventional steel. In this study, a combined laser-assisted roller hemming process is set up. For this, a 4000 W Nd:YAG-laser with a wave-length of 1096 nm is used. Several parameters are defined and the effects of heat treatment on the hemming ability of AA6014 were investigated. Taking into account the kinds of components that are expected to be formed, the experiment is set up with two flexible robots that can rotate on six axes. One moves the roller for the forming process and the other guides the laser system. Radiation tests by the laser were conducted before the forming processes. Sheets were irradiated with a laser energy level between 10 J/mm and 40 J/mm. The heat-treat condition was confirmed by micro-hardness tests. Roll (in/out) for straight contours after final hemming were measured and the effect from the heat treatment was investigated. Furthermore, the influence of the applied heat on the final hem geometry was investigated. Limitations of the conventional roller hemming process were highlighted and the transition to laser-assisted roller hemming defined.

Improving Local Formability of Aluminum 6xxx and 7xxx Alloy Sheets using Friction Stir Processing for Automotive Applications

“…The blank at specific locations also could be heated by a laser to soften targeted regions where large draw depths are required and to improve surface quality [8,[16][17][18]. The laser heating technique, or induction heating in some cases, also has been paired with the hemming and flanging processes to locally soften material before forming [18][19][20][21]. These local heating techniques can be used to attain high drawability where needed rather than compromising the T6 strength of the whole part.…”

Vision-Based Path Guidance to Achieve Dies-Free Roller Hemming Process

“…For an example, Jimbert et al [8] used electromagnetic forming (EMF) for an aluminum sheet hemming process. Laser heating to assist the roller hemming process was proposed by Kleeh et al [9,10] who discussed the effect of increasing heat in the hemming process on aluminum sheet metal after forming. Dewang and Sharma [11] presented a systematic review of the sheet metal hemming processes.…”