A study of multi-pass scheduling methods for die-less spinning

The multi-pass scheduling method is a key issue in die-less spinning for determining the quality of the final products, including their shape deviations and wall thicknesses, and has drawn increasing interest in recent studies devoted to trying to improve the accuracy of the formed parts. In this paper, two main parameters, roller path profiles and deformation allocations in each pass, are considered in newly proposed multi-pass scheduling and optimizing methods in die-less spinning. Four processing methods with different roller path profiles and with three deformation allocation methods are proposed for investigating the influence of scheduling parameters on product qualities. The ‘similar geometry principle for restraining shape deviation’ and the ‘small curvature principle for maintaining wall thickness’ are presented for optimal design of roller path profiles; in addition, the ‘uniform allocation principle for maintaining wall thickness’ and the ‘large deformation principle for restraining shape deviation’ are brought forward as suggestions for deformation allocations. Based on these principles, a scheduling method denoted by RF+(FP & EHS) is presented to improve the comprehensive quality of a product of die-less spinning.摘要目 的通过优化无芯模旋压轨迹提高成形件形状精度,同时保持壁厚以防止过度减薄。创新点针对轨迹形状设计,提出利于形状误差抑制的“几何相似性原则”和利于壁厚保持的“小曲率原则”。针对道次间距设计,提出利于形状误差抑制的终道次“大变形量原则”和利于壁厚保持的“变形量均匀分配原则”。方法首先,根据不同的前道次轨迹形状与目标件复杂轮廓形状的结合衍生出四种成形方式(表1)。通过试验比较不同成形方式对成形件形状精度和壁厚的影响。而后比较等道次倾角差(EPA)、等外径差(EDD)和等平均环向应变(EHS)成形量分配方法对成形质量的影响(图13~16)。最后,根据终道次对成形质量的关键性影响,提出基于终道次优先的等平均径向应变道次轨迹规划方法。结论基于终道次优先的等平均径向应变道次轨迹(RF+(FP & EHS))规划方法,能够在有效抑制形状偏差和提高形状精度的同时较好地保持壁厚以防止过度减薄,是一种较优的道次轨迹规划方法。