Research On The Forming Trajectory Alignment Of Sheet Metal Incremental Forming Technology Based On Machine Vision

Sheet metal incremental forming technology adapts the theory of "Layered Manufacturing"of Rapid Prototyping(RP) technology,dividing the complicated three-dimension shape into a series of two-dimension layers,using three-axis NC forming facility to drive a forming tooling head manufacturing the workpiece with layered plastic improvement manner along the forming trajectory, which derives from the contour line of the two-dimention layer. When manufacture the workpiece, it is necessary to place a bolster model under the sheet, layer and layer forming trajectory will encircle the bolster model. If the forming trajectory can not inosculate with the bolster model accurately, it will has a seriously negative influence on the forming precision, even destroy the tooling head and the bolster model. So, it is extremely important to harmonize the forming trajectory with the bolster model precisely. Based on the theory and the method of machine vision, this paper creatively develops a non-touch forming trajectory coordinates orientation system by combining monocular vision with sheet metal incremental forming technology. In order to get the high accuracy aberration coefficient of the CCD camera, the calibration model considering the aberration of the lens is established, with the method to get the calibration parameters being studied. This paper emphasizes on the way to harmonize the forming trajectory with the bolster model precisely. After a series of image processing steps, provides a measure to get the subpixel precision of the objective features parameters such as alignment hole by combining the Hough transform with the least square method. According to these parameters, deduces the formulas and the process to achieve the positional connection between the machine coordinates and the bolster model coordinates, and inosculates the machine coordinates with the bolster model coordinates by accomplishing the offset and rotation of the machine coordinates through programmable multi-axis controller. All of these methods and steps result in the rapid and precise self location of the sheet metal incremental forming facility. The precise orientation of the forming trajectory effectively decreases the disadvantages influence coming from the coordinate adaptation between the forming trajectory coordinates and the bolster model coordinates during the forming process, and it is very useful to make a more precise technical analysis on the forming technics, which includes several kinds of usually occurred defects, such as breach, material accumulation, etc.