应用于模具自由曲面的新型弹性磨具抛光技术研究

发布时间：2018-12-13 01:42

【摘要】：模具作为制造业的核心技术之一,是工业生产中用来制造成型物品的重要工艺装备,有着极为广泛的应用。抛光是制造模具型面过程中最终也是最为关键的工序,对模具的使用寿命和用其加工产品的质量有重要影响。近年来,为了提升产品竞争力,自由曲面的设计和使用越来越多,对模具抛光提出了更高的要求。目前,模具自由曲面还主要依赖人工抛光,费时费力,抛光轨迹均匀性差,且抛光质量难以保障,影响我国模具行业的快速发展。因此,深入开展模具自由曲面自动化抛光的理论与技术研究工作迫在眉睫。本文针对模具自由曲面自动化抛光的这一热点问题,在国家自然科学基金项目(51375361)资助下,提出一种应用于模具自由曲面的新型弹性磨具抛光技术。该技术所使用的弹性抛光轮工具,在抛光过程中能与模具自由曲面形成较大面积仿形接触,可随时改变磨粒切削方向,进行变轨迹抛光,在保证材料去除效率的同时,提高抛光轨迹均匀性,获得高质量加工表面,其定量可控的材料去除特性,可实现模具自由曲面高效稳定的自动化抛光。本课题的主要任务是深入研究弹性抛光轮工具的材料去除理论及抛光工艺问题。首先根据弹性抛光轮磨头的运动特点和抛光工艺要求,设计一款具有公转自转复合运动的弹性抛光轮工具,该工具可调整磨粒切削方向,进行变轨迹抛光;其次基于赫兹接触理论建立抛光接触区的压力分布模型,结合运动学理论建立速度分布模型;再次分析抛光轨迹的均匀性,根据多颗磨粒相对运动模型,建立任意一点磨粒相对于抛光接触区的运动轨迹方程,并引入变异系数对抛光轨迹均匀性进行评价,揭示转速比对抛光轨迹均匀性的影响规律;然后基于Preston理论建立材料去除函数的理论模型,并进行仿真分析;接下来通过实验设计验证材料去除函数理论模型的正确性,通过正交实验探讨自转速度、转速比、下压量、磨粒粒度这四个主要工艺参数对表面粗糙度与材料去除率的影响规律,并进行抛光综合实验验证所优选工艺参数组合的正确性和该抛光方法的高效性;最后探讨弹性抛光轮工具实现自动化抛光的关键技术问题。
[Abstract]:As one of the core technologies in manufacturing industry, mould is an important process equipment used to manufacture molding products in industrial production, and it has been widely used. Polishing is the final and most critical process in the process of manufacturing die surface, which has an important effect on the service life of die and the quality of products processed with it. In recent years, in order to improve the competitiveness of products, the design and use of freeform surface is becoming more and more, which puts forward higher requirements for die polishing. At present, the free surface of mould mainly depends on manual polishing, which is time-consuming and laborious, poor uniformity of polishing track, and difficult to guarantee the quality of polishing, which affects the rapid development of mould industry in China. Therefore, it is urgent to carry out theoretical and technical research on automatic polishing of die free surface. In order to solve the hot problem of automatic polishing of die free surface, a new type of elastic abrasive polishing technology applied to die free surface is presented in this paper, supported by the National Natural Science Foundation (51375361). The elastic polishing wheel tool used in this technology can form a large area of copying contact with the free surface of the die during the polishing process, and can change the cutting direction of the abrasive particle at any time and carry out the variable trajectory polishing, which can ensure the material removal efficiency at the same time. By improving the uniformity of polishing track and obtaining high quality machined surface, the automatic polishing of die free surface with high efficiency and stability can be realized by means of quantitative and controllable material removal characteristics. The main task of this paper is to study the material removal theory and polishing process of elastic polishing wheel tools. Firstly, according to the motion characteristics of elastic polishing wheel and the polishing process requirements, an elastic polishing wheel tool with rotation compound motion is designed. The tool can adjust the cutting direction of abrasive particles and polishing with variable trajectory. Secondly, the pressure distribution model of polishing contact area is established based on Hertz contact theory, and the velocity distribution model is established based on kinematics theory. The uniformity of polishing trajectory is analyzed again. According to the relative motion model of multiple abrasive particles, the motion trajectory equation of any point abrasive particle relative to the polishing contact zone is established, and the coefficient of variation is introduced to evaluate the uniformity of polishing trajectory. The effect of rotational speed ratio on the uniformity of polishing trajectory is revealed. Then, the theoretical model of material removal function is established based on Preston theory, and the simulation analysis is carried out. Then, the theoretical model of material removal function is verified by experimental design, and the rotation speed, rotational speed ratio and pressure drop are discussed by orthogonal experiment. The influence of the four main process parameters on the surface roughness and the material removal rate is studied. The polishing experiments are carried out to verify the correctness of the selected process parameters and the efficiency of the polishing method. Finally, the key technology of automatic polishing with elastic polishing wheel tools is discussed.
【学位授予单位】：西安建筑科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG580.692;TG76

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