基于快速测量的曲面多点成形精度控制

Forming error control in multi-point forming based on 3-D shape feedback

在板类件多点成形中,由于板料回弹、工件定位等因素,成形后的工件曲面与目标模型之间存在误差。文章通过激光快速扫描测量获得成形后工件的三维形状点云数据,经平滑去噪后,用对异常点不敏感的鲁棒最小二乘法进行B样条曲面拟合。将重构的曲面与目标模型配准计算后将曲面误差反馈到多点CAD系统,根据该误差进行回弹补偿、闭环修正工件曲面误差,并给出应用实例。结果表明,基于快速测量的曲面多点成形精度控制技术充分利用了多点成形的快速性的特点,通过三维空间形状反馈,来提高多点成形的精度。

In process of multi-point forming （MPF） for sheet metal parts, there is shape error between the formed workpiece and the objective model due to springback and positioning error. In this paper, the three-dimension shape of the formed workpiece is measured by laser scanning method. After the data points is denoised, 3D-shape expressed with B-Spline is reconstructed with them by robust least squares method which is not sentitive to outlier. Through comparing the feedback shape with designed one in CAD system, the shape error is obtained. With it, the new shape contours of the two element groups is computed to reform the workpiece. Multi-point forming experiments of titanium cranid protheses show that precision of the workpiece is improved significantly via the closed-loop multi-point forming method. And precision digital forming for sheet metal parts is accomplished based on multi-point forming techniques and rapid laser scanning measurement.