立式加工中心主轴热误差预测及补偿

发布时间：2018-11-19 13:43

【摘要】：高速精密加工过程中,数控机床轴承、导轨、丝杠等摩擦产生的热量及环境温度的变化等引起机床零部件温度的变化,进而由于热胀冷缩现象导致机床零部件的热变形,使得热误差成为影响数控机床加工精度的主要因素之一。对数控机床进行热态特性分析,建立高精度的机床热误差补偿模型,可以达到减小加工误差,提高加工精度的目的。由于机床主轴高速运转下产生大量的热量,因此机床的加工精度在很大程度上依赖于机床主轴的精度。对主轴热变形影响最大的因素是主轴前后轴承的摩擦热。当主轴旋转时,主轴前后轴承摩擦生热,产生的热量传递到主轴、刀柄等,导致主轴系统的热变形,从而影响机床的加工精度。本文基于立式加工中心主轴系统的热态特性实验分析,分别建立了基于指数函数的机床主轴热误差补偿模型、基于时序分析的机床主轴热误差补偿模型及基于残差分析的机床主轴混合热误差补偿模型用于减少主轴热变形对主轴热变形量的影响。主要研究内容包括：(1)设计了机床主轴系统热态特性分析实验,测量机床主轴热变形量、主轴轴端温度及机床环境温度。对实验数据进行分析,研究了机床主轴温度场及热变形量的变化规律。(2)在对机床主轴进行热特性分析的基础上,建立了基于指数函数的机床主轴热误差补偿模型。通过验证实验证明该模型在主轴恒速运转和变速运转两种工况下均具有较高的精度,并且建模时间短、成本低,能够方便快速的应用到工厂生产环境中。但该模型为离线建模,需要进行多次建模,否则难以适应变化的加工条件要求和季节的交替变化,鲁棒性不足。(3)应用时间序列分析法建立的基于时序分析的机床主轴热误差补偿模型。论述了如何应用热误差时间序列建立热误差补偿模型,并通过验证实验证明该模型在主轴恒速运转和变速运转两种工况下均具有较高的精度。与基于指数函数的热误差补偿模型相比,该模型为在线补偿模型,能够反映热误差周期性变化规律及随机性变化规律,且鲁棒性好。但该模型不能对机床主轴前期热误差进行补偿。(4)充分利用基于指数函数的热误差补偿模型反映热误差趋势性的特点及基于时序分析的热误差补偿模型反映热误差随机性特点,建立基于残差分析的混合热误差补偿模型。通过实验证明该混合热误差补偿模型即能更准确的补偿机床主轴热误差,同时弥补了前两种热误差补偿模型的不足。本论文得到山东省自主创新专项“高精度重心驱动桥式五轴镗铣加工中心关键技术研发及产业化”(2013CXH40101)的资助与支持。
[Abstract]:In the process of high speed precision machining, the change of the temperature of machine parts caused by friction such as bearing, guide rail, lead screw and so on causes the temperature of machine tool parts to change, and then the thermal deformation of machine tool parts is caused by the phenomenon of heat expansion and cold contraction. The thermal error becomes one of the main factors that affect the machining accuracy of NC machine tools. By analyzing the thermal characteristics of NC machine tools and establishing a high-precision compensation model of machine tool thermal error, the machining error can be reduced and the machining accuracy can be improved. The machining accuracy of machine tool depends on the precision of machine spindle to a great extent because of the large amount of heat produced by the machine tool spindle under high speed operation. The most important factor affecting the thermal deformation of spindle is the friction heat of bearing before and after spindle. When the spindle rotates, the friction heat from the front and back bearings of the spindle is transmitted to the spindle and the knife handle, which results in the thermal deformation of the spindle system, thus affecting the machining accuracy of the machine tool. Based on the experimental analysis of thermal characteristics of spindle system of vertical machining center, the thermal error compensation model of machine tool spindle based on exponential function is established in this paper. The thermal error compensation model of machine tool spindle based on time series analysis and the compensation model of machine tool spindle mixed heat error based on residual analysis are used to reduce the influence of spindle thermal deformation on spindle thermal deformation. The main contents of this paper are as follows: (1) the thermal characteristic analysis experiment of the machine tool spindle system is designed to measure the thermal deformation of the machine tool spindle, the temperature of the spindle shaft end and the temperature of the machine tool environment. The experimental data are analyzed and the variation of the temperature field and thermal deformation of the machine tool spindle is studied. (2) based on the analysis of the thermal characteristics of the machine tool spindle, the thermal error compensation model of the machine tool spindle based on exponential function is established. The experimental results show that the model has high precision under both constant spindle and variable speed operating conditions, and the modeling time is short, the cost is low, and the model can be applied to the factory production environment conveniently and quickly. But the model is off-line modeling, which needs to be modeled many times, otherwise it is difficult to adapt to the changing processing conditions and the alternation of seasons. (3) time series analysis is used to establish the compensation model of machine tool spindle thermal error based on time series analysis. This paper discusses how to use the time series of thermal error to establish the model of thermal error compensation, and proves that the model has high accuracy under the two conditions of constant speed operation and variable speed operation of spindle. Compared with the thermal error compensation model based on exponential function, the model is an online compensation model, which can reflect the regularity of periodic variation and randomness of thermal error, and has good robustness. However, the model can not compensate the thermal error of the machine tool spindle. (4) the thermal error compensation model based on exponential function is fully used to reflect the trend of thermal error and the thermal error compensation model based on time series analysis is used to reflect the thermal error compensation model. Randomness of thermal error, A hybrid thermal error compensation model based on residual analysis is established. It is proved by experiments that the hybrid heat error compensation model can compensate the spindle thermal error more accurately and make up for the deficiency of the former two thermal error compensation models. This paper is supported by Shandong independent innovation project "key Technology Research and industrialization (2013CXH40101) of High Precision Center of Gravity driving Axle Type five Axis boring and Milling Machining Center".
【学位授予单位】：山东大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG659

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