数控转塔刀架可靠性关键技术研究

发布时间：2019-06-29 07:05

【摘要】：随着科学技术的迅猛发展和国内制造行业的产业升级,国内数控机床市场逐步向高端化发展,中高档数控机床所占的比重连年上升。然而,由于国产数控机床的可靠性与国外先进水平存在较大差距,使得我国中高档机床大量依赖进口,这严重阻碍了我国制造业的发展。造成国产数控机床整体可靠性低的主要原因之一是其关键功能部件可靠性低。数控转塔刀架作为数控车床的关键功能部件之一,其可靠性高低直接影响到机床整机的可靠性状况,刀架发生故障必然导致机床加工中断甚至停机。因此对数控转塔刀架的可靠性进行系统的研究十分迫切。论文结合国家科技重大专项,以某系列数控转塔刀架为研究对象,对其可靠性关键技术进行了深入系统的研究,研究成果对提高数控转塔刀架的可靠性具有重要的指导意义。论文的主要研究内容如下:①依据数控转塔刀架产品结构和工作原理对其进行子系统划分,得到数控转塔刀架可靠性模型;分析数控转塔刀架可靠性分配的影响因素,综合考虑多领域专家的知识,利用模糊层次分析法对数控转塔刀架进行可靠性分配,得到可靠性分配指标,并与相似产品的故障部位频率做比较,验证分配指标的合理性。②首先采用结构分析和设计技术(Structured Analysis and Design Technique,SADT)对数控转塔刀架进行功能分析,将产品功能动作分解到元动作级,针对各元动作制定装配控制点和详细的装配可靠性控制措施,建立起数控转塔刀架可靠性驱动的装配工艺方案;然后将功能分析的SADT模型转化为对应的广义随机Petri网(GSPN)模型,使其具有动态分析与定量研究功能,再通过同构的Markov链对模型进行定量分析;为了获得准确的分析模型,利用灰色理论中的区间灰数对GSPN的变迁平均激发率进行处理;针对数控转塔刀架装配过程的可靠性特征,用装配可靠度指标对其进行评价;最后利用该模型对某系列数控转塔刀架进行实例分析,并提出控制改进措施,提高数控转塔刀架装配可靠性水平。③研究数控转塔刀架与主机适应性技术,包含数控转塔刀架安装在车床上的螺钉组联接可靠性和刀架与数控系统控制匹配两大内容。针对螺钉组联接可靠性,首先分析数控车床的工作状态,确定切削力的大小和方向,然后结合刀架固定在车床上的螺钉组联接方案分析螺钉组的受力情况,计算螺钉组的预紧力范围,并以此为依据做螺钉拧紧试验,最终确定拧紧工艺方案;针对数控转塔刀架与数控系统控制匹配问题,首先确定双向换刀逻辑的实现方式,编制换刀操作流程图,给出刀架控制模块与数控系统连接的接口线路图,然后设计高效的PLC程序,最后分析刀架换刀过程的常见故障,针对常见故障设计相应的PLC报警程序和处理程序。
[Abstract]:With the rapid development of science and technology and the industrial upgrading of domestic manufacturing industry, the domestic CNC machine tool market is gradually developing to the high end, and the proportion of middle and high grade CNC machine tools is increasing year by year. However, due to the big gap between the reliability of domestic CNC machine tools and the advanced level of foreign countries, China relies heavily on imports of medium and high grade machine tools, which seriously hinders the development of China's manufacturing industry. One of the main reasons for the low overall reliability of domestic CNC machine tools is the low reliability of its key functional components. As one of the key functional components of NC lathe, the reliability of NC turret tool holder directly affects the reliability of the whole machine tool, and the failure of the tool holder will inevitably lead to the interruption or even shutdown of machine tool processing. Therefore, it is very urgent to systematically study the reliability of NC turret tool holder. Combined with the major national science and technology project, this paper takes a series of CNC turretower tool holder as the research object, and makes a deep and systematic study on its reliability key technology. the research results have important guiding significance for improving the reliability of NC turretower tool holder. The main research contents of this paper are as follows: (1) according to the product structure and working principle of NC turretower tool holder, the subsystem is divided, and the reliability model of NC turretower tool holder is obtained. This paper analyzes the influencing factors of reliability distribution of NC turretower tool holder, comprehensively considers the knowledge of multi-domain experts, and uses fuzzy analytic hierarchy process (AHP) to distribute the reliability of NC turretower tool holder, and obtains the reliability distribution index, and compares it with the frequency of fault position of similar products to verify the rationality of the allocation index. 2 firstly, the function of NC turretower tool holder is analyzed by using structure analysis and design technology (Structured Analysis and Design Technique,SADT). The functional action of the product is decomposed into the meta-action level, and the assembly control points and detailed assembly reliability control measures are worked out for each element action, and the assembly process scheme of the reliability drive of the NC turretower tool holder is established. Then the SADT model of functional analysis is transformed into the corresponding generalized stochastic Petri net (GSPN) model, which has the function of dynamic analysis and quantitative research, and then the model is quantitatively analyzed by isomorphism Markov chain. In order to obtain the accurate analysis model, the interval grey number in grey theory is used to deal with the average excitation rate of GSPN. According to the reliability characteristics of NC turret tool holder assembly process, the assembly reliability index is used to evaluate it. Finally, the model is used to analyze a series of NC turret tool holder, and the control improvement measures are put forward to improve the assembly reliability level of NC turretower tool holder. 3 the adaptability technology between NC turretower tool holder and host computer is studied, including the connection reliability of screw group installed on lathe and the control matching between NC turretower tool holder and NC system. According to the reliability of screw group connection, the working state of NC lathe is analyzed, the size and direction of cutting force are determined, then the force of screw group is analyzed according to the connection scheme of screw group fixed on lathe, the pre-tightening force range of screw group is calculated, and the screw tightening test is carried out on this basis, and finally the tightening process scheme is determined. In order to solve the problem of matching between NC turret tool holder and NC system control, firstly, the realization mode of bidirectional tool changing logic is determined, the flow chart of tool changing operation is compiled, the interface circuit diagram between tool holder control module and NC system is given, and then an efficient PLC program is designed. Finally, the common faults of tool holder change process are analyzed, and the corresponding PLC alarm program and processing program are designed for common faults.
【学位授予单位】：重庆大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG659

【相似文献】