面向接触式原位测量的复杂曲面加工精度检测方法研究

Components with complex surfaces are widely used in aviation, aerospace and other industries. However, due to the adverse influence of physical factors, single-layer cutting strategy is often difficult to meet the accuracy requirements. In conventional machining, operations of part machining and accuracy identification are separated and conducted in different facilities, which make it impossible to feedback the measurement result to machining process, as well as to eliminate the machining error. Based on the accumulation of technologies and experiences on on-machine measurement (OMM) with a touch-trigger probe, the project aims to develop an integrated OMM-based methodology on measurement path planning and machining error evaluation, avoiding bringing in the re-clamping error caused by off-line detection. It will provide a credible basis for machining error compensation. An algorithm to determine the density of sampling point is designed firstly while considering the geometric characteristics of the surface and the distribution of the machining error. Secondly, a sampling point distribution planning method is implemented while considering the machining information. Then, the 5-axis OMM path is planned with the advantages of high measurement efficiency, simple motion control. At last, a surface reconstruction algorithm based on T-spline surface is carried out while considering the constraint of finite set of measurement points. Finally, a complete OMM path planning and machining accuracy evaluation system for complex surface is implemented. This project is the foundation of the new machining method of measurement data feedback based closed-loop control of machining accuracy by integrating the machining and measurement on 5-axis machine tool. The research results will provide important theoretical and technical support for digital machining and detection.

复杂曲面类零件被广泛应用于航空航天等领域，然而受铣削过程中物理因素的影响，单次加工往往难以达到其精度要求。传统铣削工艺中零件加工与精度测量过程相分离，难以将测量数据反馈到加工过程，实现加工误差的补偿与修复。本项目以前期在原位测量技术方面的技术积累为基础，研究基于接触式测头的复杂曲面加工精度快速检测与评价的理论和方法，避免因离线检测而带来的二次装夹误差，为加工误差的原位补偿提供依据。研究曲面几何特征与加工误差分布等多约束影响下的采样点密度计算方法，建立考虑加工信息的高效接触式测量的采样点规划模型，开发具有测量效率高、运动控制简单等特点的五轴原位测量路径规划算法，探索有限测量点集下的T样条曲面拟合算法，最终形成一套完整的复杂曲面原位测量路径规划与加工误差评价体系。本项目是实施基于测量数据反馈的复杂曲面加工-测量一体化闭环精度控制新方法的基础，研究成果为数字化加工与检测提供重要的理论与技术支撑。

航空航天汽车能源等领域采用大量结构复杂，具有深腔或薄壁特征的结构件，以实现减重和增加强度的目标。结构件深腔特征加工更加注重加工效率，例如Φ3330mm火箭整体筒段包含上千个异形网格型腔，提高型腔加工效率对于提高整体筒段产能具有重要作用。现有CAM软件能够生成多种型腔加工刀具路径，导致生产企业更加依赖于加工装备而忽略了对加工工艺的重视程度。另一方面，受铣削过程中物理因素与机床几何误差等误差源的影响，结构件薄壁特征的单次加工往往难以达到其精度要求。传统铣削工艺中零件加工与精度测量过程相分离，难以将测量数据反馈到加工过程，进而实现加工误差的补偿与修复。综上，本报告以前期在数控加工与原位测量技术方面的技术积累为基础，提出了一种基于三角网格简化的复杂曲面检测自适应采样方法，将简化后的网格顶点作为测量点，实现原位测量采样点规划。研究了一种基于加工试验的旋转轴几何误差和装夹误差的识别方法，并通过实验验证了该测量方法的可行性。提出了基于原位测量的箱底减薄铣削工艺，利用接触式测头测量薄壁件外型面，用超声波测厚仪测量薄壁件在各采样点处的厚度，建立考虑毛坯几何变形的平底刀端铣刀轴方向优化方法。研究插铣刀具磨损机理及其影响因素，提出了基于最大切削包角约束和分区加工的型腔插铣刀具路径规划方法。提出基于中轴变换的螺旋刀具路径生成方法，通过提高型腔实际平均切宽，提高加工效率。项目研究成果对于实现薄壁件数字化与智能化制造具有重要意义。