Metal sheet spinning is an advanced near-net forming technology for the manufacture of thin-walled ellipsoidal heads. The exact control of dimensional accuracy, however, is a considerable problem for spinning thin-walled parts with large diameter-to-thickness ratios. In this work, a marginal-restraint mandrel-free spinning process with two passes is proposed for the fabrication of thin-walled ellipsoidal heads without wrinkling. A finite element model is established and verified to study the influences of spinning parameters on the dimensional precision of thin-walled ellipsoidal heads. It is found that the spinning parameters considerably influence the deviations of wall thickness and contour characteristics. A small forming angle or small roller fillet radius during the first pass spinning, as well as the small angle between passes or high feed ratio during the second pass spinning, can improve the wall thickness precision. Meanwhile, as the forming angle or feed ratio is increased during the first pass spinning, the contour precision initially increases and then decreases. During the second pass spinning, the contour precision can be improved at a small angle between passes, whereas it deteriorates at a larger roller installation angle. The optimized spinning parameters are obtained and verified by experiments.

中文翻译：

---

薄壁椭圆头无边际约束无心轴纺丝工艺

金属薄板旋压是一种先进的近净成形技术，用于制造薄壁椭圆头。然而，对于具有大直径/厚度比的薄壁零件，尺寸精度的精确控制是一个相当大的问题。在这项工作中，提出了一种具有两次通过的无边际约束的无心轴纺丝工艺，用于制造薄壁椭圆头，而不会起皱。建立并验证了有限元模型，以研究旋转参数对薄壁椭圆头的尺寸精度的影响。已经发现，旋转参数极大地影响壁厚和轮廓特性的偏差。第一次通过时的成形角较小或辊子圆角半径较小，在第二道纺丝过程中，道之间的夹角小或进给比高，可以提高壁厚精度。同时，随着在第一道纺丝过程中成形角或进给比的增加，轮廓精度首先增加，然后降低。在第二道次纺纱期间，可以在道次之间的小角度处提高轮廓精度，而在更大的罗拉安装角度下会降低轮廓精度。获得了优化的纺丝参数，并通过实验进行了验证。滚道之间的角度较小时，轮廓精度可以提高，而滚子安装角度较大时，轮廓精度会降低。获得了优化的纺丝参数，并通过实验进行了验证。滚道之间的角度较小时，轮廓精度可以提高，而滚子安装角度较大时，轮廓精度会降低。获得了优化的纺丝参数，并通过实验进行了验证。