Abstract
Due to its high production flexibility, roller hemming has become the mainstream process for forming and joining metal sheets in the automotive industry. The traditional roller hemming process requires specific dies to support sheet metal parts and repeated offline manual adjustment of hemming routes, resulting in high die costs, high time consumption, and excessive labor inputs. The universal platform presented in this paper could replace specific dies to effectively reduce costs and expand production flexibility. To reach this objective, a vision-based automatic compensation path to achieve a dies-free roller hemming process is proposed and investigated in this paper. Hand–eye sensor modules assisted by multi-coordinate synchronization calibration for the roller hemming were designed to reconstruct three-dimensional (3-D) shape data of the incoming materials. Results from the proposed system were validated with experimental measurements for the sheet offset and the compensation of the arm hemming position, showing that the single-axis error can be reduced to ≤0.1 mm.
Highlights
Mechanical and Mechatronics Systems Research Labs, Industrial Technology Research Institute, Chutung, Department of Power Mechanical Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan
With the proposed method of vision-based automatic compensation path guidance that is discussed in detail a universal fixed platform replacing specific dies is feasible, which allows for a dies-free roller hemming process that further reduces costs and expands production flexibility
In order to understand how much positional deviation of the sheet metal work piece exists without a specific die, experiments using three car hood sheet metal parts of the same model were conducted
Summary
Sheet metal is the most commonly used component in automobiles, for which stamping is the main forming process. Hemming on the other hand is a sheet metal forming and joining process used in the automotive industry to join inner and outer closure panels and components. Such panels or components include hoods, doors, trunk-lids, tailgates, etc. This hemming processing is the process of bending/folding the edge of the outer part (skin) over the reinforcing inner one, which largely represents and determines the external quality of the final automotive products. Due to the high production flexibility of robotic roller hemming, it has become the mainstream process for joining metal sheets in the automotive industry. In present practice, even the highly flexible robotic roller hemming still requires specific dies to support the sheet metal parts. With the proposed method of vision-based automatic compensation path guidance that is discussed in detail a universal fixed platform replacing specific dies is feasible, which allows for a dies-free roller hemming process that further reduces costs and expands production flexibility
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