五轴数控机床进给系统组成结构复杂，特别是在复杂曲面加工过程中其动态刚度不断发生变化，成为制约其加工精度的主要因素。研究过程中以五轴机床运动产生的弹性变形为出发点，建立了A/C双摆头机床进给系统动力学模型，推导了因进给系统弹性变形导致的轮廓加工误差，并基于一种新型的自由曲面检验试件，给出了其数控加工过程的运动控制策略，分析了轮廓度误差与试件曲率间的关系，得到了数控机床进给系统刚度特性对自由曲面轮廓误差的影响机理，最后在机床上进行了切削验证。上述研究成果有助于完成复杂曲面加工过程中机床工作性能评估，为利用检验试件分析机床动态刚度特性提供了原理性支持。

The complex structures of feed system are the main components of five-axis CNC machine tool. Particularly during the processing,the dynamic stiffness of feed system change with the motions of each axis,which present the performance limit of cutting free-form surface. The model of the elastic deformation of the feed system on an A/C machine tool is established. Based on a new free surface specimen,the contouring errors caused by deformation are analyzed. The motions of five axes are simulated by a cross constraint control strategy then the contouring errors on different curvature of the specimen are obtained. The mechanism of elastic deformation of feed rate on courting errors is explained and verified by the cutting experiments. Presenting,measuring and evaluation these limits are easy for the user to understand the challenging of elastic deformation of the machine tool. It also provide a new way to evaluating the performance of machine tool by S part specimen.