复杂曲面加工误差补偿方法与关键技术研究

发布时间：2019-06-20 14:23

【摘要】：随着我国航空航天、国防、运载和能源等领域不断的发展,精密复杂零件对加工效率、成形的精度以及成品率等指标提出了更高要求。鉴于复杂曲面类零件的几何结构复杂性,该类零件一般都由五轴数控机床加工完成。本文围绕复杂曲面加工误差补偿的关键技术,系统研究了五轴加工铣削力预测、刀具变形误差补偿、在机检测技术和误差反馈补偿的相关理论与策略,并将涉及到的模型、方法和系统进行了实验验证。实现了对复杂曲面加工过程中“预补偿-检测-反馈补偿”的分步补偿过程,这对提高零件型面加工精度和降低报废率等方面都具有重要的意义。基于五轴数控机床的运动学理论,建立了加工过程中刀具相对于工件的空间转换关系,提出一种五轴加工未变形切屑厚度的计算模型。根据所提出的球头铣刀微元铣削力模型,综合考虑了耕犁力对铣削力预测模型精度的影响,建立了基于刀刃运动轨迹分析的五轴加工铣削力预测模型,并给出了耕犁力和剪切力系数的识别方法。基于悬臂理论分析了刀具在加工过程中的受力变形规律,提出了一种应用于五轴加工的刀具变形误差补偿策略。将误差“镜像”反变形补偿方法扩展至五轴加工刀具变形误差补偿中,分别对刀位点和刀轴矢量进行“镜像”反变形误差补偿。考虑到误差补偿参考基准对补偿效果的影响,建立了五轴加工刀具变形误差补偿的参考基准模型。完成五轴数控机床在机检测复杂曲面测量软件系统的开发。通过对系统各功能模块的设计,实现了对复杂零件曲面检测点规划、检测点信息提取、检测路径自动规划、检测代码生成和检测路径仿真的一体化过程。对复杂曲面在机检测数据进行误差评定处理,提出了一种基于五轴数控机床在机检测的误差反馈补偿策略。该补偿策略以测量点相对于理论曲面的法向偏差为依据,基于“镜像”反变形的思想,计算获得测点云对应的“镜像”补偿点位置,利用NURBS曲面拟合理论,对“镜像”点云进行曲面插值,从而得到补偿加工曲面轮廓。在三维软件中对补偿零件模型进行重构,以重构模型作为加工驱动几何体规划刀具加工路径,指导后续补偿加工。本文的研究成果对丰富和完善复杂零件曲面“加工-检测-补偿加工”一体化的质量控制过程提供了可行、科学的理论依据和技术支撑。
[Abstract]:With the continuous development of aerospace, national defense, transportation and energy in China, precision and complex parts put forward higher requirements for machining efficiency, forming accuracy and yield. In view of the complexity of the geometric structure of complex curved surface parts, this kind of parts are usually machined by five-axis NC machine tools. In this paper, the related theories and strategies of five-axis machining milling force prediction, tool deformation error compensation, in-machine detection technology and error feedback compensation are systematically studied around the key technologies of complex surface machining error compensation, and the related models, methods and systems are verified by experiments. The step-by-step compensation process of "pre-compensation, detection-feedback compensation" in the process of complex surface machining is realized, which is of great significance to improve the machining accuracy of parts profile and reduce the scrap rate. Based on the kinematic theory of five-axis NC machine tool, the spatial conversion relationship between cutting tool and workpiece in machining process is established, and a calculation model of undeformed chip thickness in five-axis machining is proposed. According to the proposed micro-element milling force model of ball end milling cutter, considering the influence of ploughing force on the accuracy of milling force prediction model, a five-axis machining milling force prediction model based on blade trajectory analysis is established, and the identification method of ploughing force and shear force coefficient is given. Based on the cantilever theory, the force and deformation law of the tool in the machining process is analyzed, and a tool deformation error compensation strategy applied to the five-axis machining is proposed. The error "mirror" anti-deformation compensation method is extended to the five-axis machining tool deformation error compensation, and the "mirror" anti-deformation error compensation is carried out for the tool position and the tool axis vector, respectively. Considering the influence of the reference of error compensation on the compensation effect, the reference model of tool deformation error compensation for five-axis machining is established. Complete the development of five-axis CNC machine tool in-machine detection complex surface measurement software system. Through the design of each functional module of the system, the integrated process of surface detection point planning for complex parts, detection point information extraction, automatic detection path planning, detection code generation and detection path simulation is realized. The error evaluation and processing of complex surface in-machine detection data is carried out, and an error feedback compensation strategy based on five-axis NC machine tool in-machine detection is proposed. The compensation strategy is based on the normal deviation of the measured point relative to the theoretical surface, and based on the idea of "mirror" anti-deformation, the position of the "mirror" compensation point corresponding to the measuring point cloud is calculated, and the surface interpolation of the "mirror" point cloud is carried out by using NURBS surface fitting theory, so as to obtain the compensation machining surface outline. The compensation part model is reconstructed in three-dimensional software, and the reconstruction model is used as the machining driving geometry to plan the tool machining path and guide the subsequent compensation machining. The research results of this paper provide feasible, scientific theoretical basis and technical support for enriching and perfecting the integrated quality control process of machining, testing and compensation machining of complex parts.
【学位授予单位】：天津大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TG659

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