元动作装配单元误差源及误差传递模型研究

Mechanism Analysis of Deviation Sourcing and Propagation for Meta-action Assembly Unit

机械产品装配误差源和误差传递规律分析,是装配精度预测与控制的前提工作。在对数控机床进行结构化分解至元动作的基础上,提出了元动作装配单元的概念。针对元动作装配单元层面影响装配质量的因素,将装配过程的误差源分为位置误差、形状误差、装配位置误差等五类误差源;建立各类误差源及其误差评价的统计模型;分析误差在零件间、零件内两特征间的传递和相互作用,构建误差传递链图、误差传递网络对五种误差源与配合误差进行形象化表达。综合误差传递链接图,建立面向整个产品误差传递及装配功能表达的装配误差网络图模型,为方便误差传递网络图中各类误差传递模型的计算与存储,又进一步构建了面向整个产品装配误差传递的链接矩阵。以某加工中心连续分度转台蜗杆转动元动作装配单元装配为例,验证误差源表达和误差传递模型的有效性。

Mechanism of error sourcing and propagation for rigid part assembly is the important work for mechanical precision predicting. The concept of meta-action assembly unit is proposed based on the structure decomposition using PFMA for CNC machine tool. The deviation source that affects assembly precision or accuracy is clustered into five types： Deviation of geometric location and orientation, variation of geometric form and deviation of part location and orientation etc. Error sources and statistical evaluation model is established. In addition, mechanism of deviation propagation between two mating surfaces or key characteristics is discussed. Propagation linkage graph and, the error propagation linkage network for five kinds of error sources are built to express the error in vision and cooperate with error in visual expression. Error transfer linkage figure is comprehensively considered, and build assembly linkage network model and error transfer function expression. To simplify the error transfer linkage in the network diagram calculation and save of all kinds of error propagation model, the linkage for the entire product assembly error propagation linkage matrix is built. Finally, an example with deviation sourcing and propagation is introduced to verify the effectiveness of each model.