Experimental Study On Flexible Roll Forming Process

The conventional roll forming process is capable of producing various kinds of products with constant cross-sections. Roll formed products with constant cross-sections are widely used as component parts especially in architecture and automobile manufacture industries. Profiled parts with variable cross-sections whose mechanical performance are excellent meet the light weight vehicle concept. Hence flexible roll forming process, capable of producing high-quality profiles with variable cross-sections economically and efficiently, becomes the international focus of the related research. The research on this innovative process is just beginning, most of which is confined within theory and simulations. Hitherto no experimental study has been reported in China.Under the project supported by the National Natural Science Foundation of China and Beijing Municipal Natural Science Foundation, experiments were carried out for the first time domestically, with the flexible roll forming machine with two motion axes invented by the roll forming research team of NCUT, to study the newly developed forming process. Some critical issues in the experiment such as the selection of the parameters of pre-cut sheets, the design of rolls, the distribution of bending angle, the adjustment of the machine, the center line's overlapping of the pre-cut sheet and the machine, and the test of the sheet's feeding velocity are involved in the thesis, and practical solutions are given according to the actual conditions. The generating mechanism and eliminating solutions of defect appearing on U channel with variable width cross-sections lengthwise formed via the experiment are also analyzed and concluded in this paper. Analysis on wrinkles on the convex part of the leg is performed both experimentally and theoretically. Beside this, it is also studied in this paper the flatness and the distortion of the web part. the wrinkles are stemming from buckling due to the excess of compression strain in the convex part of the leg; to alleviate or avoid this defect, measures such as reduction of the bending angle or the length of the leg, or increase of the radius of the convex edge or thickness can be taken separately or comprehensively; the nearer to the wrinkle area, the larger distortion of the web part will be; Ultimately conclusions can be drawn as below. The machine's working principle, mechanical structure and servo control system are correct and feasible; the flexible roll forming machine with two motion axes is with a larger range of products compared with the machine with single motion axis.To sum up, experimental study on the flexible roll forming process was executed in this paper, which is helpful to promote theoretical study and industrial application of this process.