随着消费者对汽车性能与个性化要求的不断提高，汽车生产厂商需要不断更新汽车外观，汽车覆盖件模具的设计、制造时间约占整个汽车研发周期的2／3。为了保证汽车覆盖件高品质生产，如何提高模具耐用度和加工精确度显得尤为重要。本文针对汽车覆盖件模具生产过程中遇到的实际问题，将提高加工精度与生产效率作为研究目标，通过构建复杂型面加工铣削力预测模型，分析加工过程稳定性、加工系统综合刚度场分布规律，结合在线测量技术完成对加工误差的预测与补偿，进而指导汽车覆盖件模具加工过程中加工参数的优选与加工路径的合理规划，其具体研究内容包括： (1)针对模具型面铣削载荷不平稳的问题，基于机械模型法对球头铣刀曲面铣削过程中刀具与工件切削空间接触情况进行描述，总结了型面曲率变化对刀具—工件切削接触轴、径向浸没角的影响规律，完成对瞬时切削厚度、切削宽度模型的修正。综合考虑型面曲率、刀具几何尺寸、加工参数等多因素的影响，构建模具型面瞬时铣削力预测模型，该模型在曲率变化较大的型面区域仍可保证较高的预测精度。运用分形维数铣削力数据及对应加工区域的表面粗糙度值的非线性特征进行评价，为控制模具型面铣削加工载荷变化趋势、提高加工精度提供理论基础。 (2)针对模具曲面铣削加工过程中出现切削颤振的问题，综合考虑模具曲面曲率、刀具倾角等对动态未变形切削厚度的影响，建立动力学方程。提出一种将全离散法与动、静态切削厚度的比值作为铣削加工稳定性判定阈值的方法。 以淬硬钢模具曲面铣削加工振动信号为研究对象，基于相平面法、Poincare截面图和频谱分析了不同加工参数时的振动信号，以此确定不同参数下铣削过程是否发生颤振，对所提出的方法进行验证。通过汽车覆盖件模具铣削加工实验与稳定性预测对比发现，稳定性边界自身具有不确定性，且所提出的铣削稳定性预测方法有较高的预测精度。 (3)针对加工系统综合刚度性能对加工质量影响，结合模具曲面特征设置相应的采样点，提出一种基于多体小变形理论的加工系统综合刚度场预测模型，并引入力椭球进行刚度性能分析。在刀具不同的空间姿态下，通过力椭球分析加工系统中机床横梁、刀具-主轴结合部、铣削刀具、模具曲面等对加工系统刚度性能有影响的关键部分，研究发现更换刚度性能更好的刀具、尽量使四轴机床上刀具的进给方向与模具曲面的法线相垂直是提高加工系统综合刚度性能的有效手段，这为提高模具型面加工精度和加工效率提供了理论指导。 (4)提出了一种基于曲面自适应采样的NURBS曲面重构方法，并通过在线测量技术对被加工型面的法向加工误差进行计算。该方法基于高斯曲率弯曲模型的自适应采样法可以准确的反应曲面的弯曲程度，在模具型面曲率变化较大的区域布置较为密集的采样点面，在保证检测精度的前提下，该方法可大幅提高检测效率。 (5)构建了模具型面加工系统加工误差模型，该模型综合考虑了刀具轴偏心、刀具系统变形、型面曲率、切削振动等因素对加工误差影响，此模型对汽车前盖板模具型面加工误差的预测具有较高的精度。在充分考虑了铣削加工系统综合刚度场、铣削加工稳定域等对加工误差影响的前提下，基于该模型的预测结果进行离线加工误差补偿可有效控制加工误差。 关键词：汽车覆盖件模具；铣削力；铣削动力学；综合刚度场；在线测量；加工误差

With the continuous development of economy, cars have become the necessities of daily life for people. With the continuous improvement of consumers’ demand for automotive performance and personalization, car manufacturers need to constantly update the appearance of the car. As one of the most important parts of the automobile production process, its design and manufacturing process accounts for 2/3 of the entire automotive R & D cycle. In order to ensure the high quality production of automotive panels, how to improve the durability and accuracy of the die is particularly important. This paper aims at improving the precision and efficiency of automobile panel die by using complex surface milling force prediction model, analysis of stability in machining process and analysis of machining system stiffness distribution. Then, machining error prediction and compensation is completed base on on-machine inspection. The above research can be used to guide the optimization of machining parameters and the reasonable planning of the machining path. The specific research contents include: (1)In order to solve the problem of uneven load on the die surface milling, the spatial contact between cutting ball-end milling tool and workpiece during the milling process is described by using the mechanical model method. The axial immersion angle and radial immersion angle in the milling process are redefined. The influence of the curvature of the surface on the cutting contact axis and the radial immersion angle of the tool workpiece are analyzed. The prediction model of instantaneous milling force under the influence of many factors such as curvature of surface, tool geometry and machining parameters is built. Then, the milling force of hardened steel dies is predicted based on the model. At the same time, the fractal dimension is used to analyze the nonlinear characteristics of cutting force. (2)In order to solve the problem of chattering in milling process of die surface, dynamic equations are established by considering the influence of die surface curvature and tool rake angle on the dynamic undeformed chip thickness. The stability of milling under parameters near the stability boundary (which obtained by the full discrete method) are explored by taking the ratio between dynamic cutting thickness and static cutting thickness as the threshold. The vibration signals of different processing parameters are analyzed based on phase plane, Poincare cross section and spectrum, in order to determine whether flutter is occurring in the milling process under different parameters. Subsequently, the stability prediction method is verified through the milling experiment of automobile panel die. (3)In order to analyze the influence of the comprehensive stiffness of the machining system on the machining quality, according to the theory of multi body small deformation, through the point transfer matrix and Jacobi matrix, the comprehensive stiffness field modeling of the sampling system is completed base on the sampling points of the die surface. At the same time, the force ellipsoid is introduced. The force ellipsoid is used to analyze the key parts of the rigidity performance of the machining system, such as the beam of machine tools, the joint of the tool spindle and milling cutter, milling cutter and the surface of die. Subsequently, the influence of milling cutter space position and die face curvature on the comprehensive stiffness field of the machining system is analyzed. It can guide the tool's spatial position and cutting path planning during the milling process of automobile panel die. (4)A surface reconstruction method for NURBS surface based on adaptive surface sampling is established, and the machining error is calculated by the machine measurement technology. The method which is based on the adaptive sampling method of the Gauss curvature bending model can accurately reflect the bending degree of the surface. The denser samples are arranged on the region with larger curvature change of the die surface. Under the premise of ensuring the detection accuracy, the method can increase the detection efficiency. (5)The machining error in the process of automobile panel die was predicted by using the processing system error model for complex surface which considering the cutting tool shaft eccentricity, tool system deformation, surface curvature, cutting vibration factors and milling system stiffness field analysis. This model has a high accuracy for predicting the machining error of automobile front panel die surface. The machining error can be effectively controlled by off-line machining error compensation based on the model by considering the influence of the comprehensive stiffness field of milling system and the stability domain of milling process. Key words: Automobile panel die; Milling force; Milling dynamic; Comprehensive stiffness field; On Machine Inspection; Machining error