在加工汽车覆盖件模具复杂曲面时，机床-刀具刚度、刀具位姿变化、模具型面变化都会影响加工系统综合刚度，进而影响模具加工精度。以四轴数控加工中心为例，针对模具曲面特征设置相应采样点，依据多体小变形理论，通过点传递矩阵、雅可比矩阵等完成该采样点的加工系统综合刚度建模，并引入了力椭球。在刀具不同的空间姿态下，通过力椭球分析了机床横梁、刀柄、刀具、模具曲面特征等对加工系统综合刚度性能的影响，揭示了曲面模具加工系统综合刚度的分布规律。最后通过试验证明，该理论模型可以有效地优化复杂型面模具加工工艺，减小模具的加工误差。

When producing the mould complex curved surface of the cars’outer covering parts , machine-cutting tool rigidity,cutting tool position change and distribution of workpiece rigidity will influence rigidity of machining systems and influence the processing quality of mould. A four-axis machining centers as example is set corresponding sampling points on the mould surface,based on multi-body theory of small deformation and space force ellipsoid,the system comprehensive rigidity modeling is completed through the point of transfer matrix and the Jacobian matrix. The comprehensive stiffness properties of machining system under the different tools space posture are revealed by using the force ellipsoid to analysis the machine tool beams,cutting tool posture,cutting tool,combinations parts of cutting tool spindle and the mould surface characteristics. And the processing system integrated stiffness distribution is studied. In the end,through the experiments,it proves that the theoretical model can effectively optimize the complex surface mold processing technology and reduce the processing error.