基于热力耦合影响的高精机床静动态精度性能研究

发布时间：2018-01-20 21:23

本文关键词： 高精机床热力耦合数值模拟接触刚度进给单元动态精度　出处：《哈尔滨工业大学》2016年博士论文　论文类型：学位论文

【摘要】：高速、高精数控机床是影响和制约电子制造业水平和电子信息产业基础配套能力的重要因素。近年来,随着信息、通讯、医疗、航空航天等领域的电子产品向高功能、高密度及高可靠性发展,对数控机床加工精度、效率及稳定性提出了更高要求。热误差是影响高精机床动态加工精度的决定性因素,占全部加工误差的70%。因此,开展工程热误差机理的研究对于解决高精机床普遍存在热稳定性差的技术瓶颈具有重要意义。整机热动态性能是温度场在结构上产生的复杂热应力、非线性变形及构件间热力耦合效应的综合体现,因此不能孤立研究局部系统的热现象。本文从全局角度分析了机床系统内部结构单元及整机在热力耦合效应下的静、动态精度特性及演变规律,主要内容如下:直线滚动导轨非线性刚度分析。基于Hertz接触理论,考虑接触体弹性变形及预紧效应建立了导轨初始刚度模型,量化了上、下滚道初始刚度随外载呈相反趋势的非线性变化特性。通过对导轨滚珠差动滑动、弹性滞后及自旋运动的摩擦能解析,计算了滚动界面的等效热源强度,并基于Achard磨损理论建立了导轨接触界面磨损量计算模型。基于导轨热力耦合数值模拟及磨损深度解析建立了最终刚度模型,结果显示,上、下滚道接触刚度在摩擦热传递、热弹接触变形及磨损综合作用下随行程而呈现不同程度的非线性递减。通过LMS振动测试完成刚度模型的频域验证,成功探测到导轨由于接触刚度下降刚体模态由(2.36-6.58)k Hz迁移至(2.05-5.66)k Hz,并基于提出的刚度模型建立了更为精确的导轨刚体模态频率解析式,实测频率与解析值最大误差为15.2%。同时,结果表明,摩擦热和磨损效应对导轨刚度变化的影响具有时序性。将热影响研究拓展至整机基础结构,分析了环境热波动下新型矿物铸件材料机架的热力学性能及结构静态精度。通过平面度测试和线性模态分析验证了此材料替代传统材料应用于精密机床的可靠性。结果表明,矿物铸件结构静态刚度可满足精密机床大型基础构件50μm平面度的精度要求,其动力学特性优于铸铁,模态特性略逊于天然花岗石,低阶自然振动频率高于90Hz,保证了其在系统典型激振频率下的动力学稳定性。基于有限元法推导了矿物铸件结构温度场解析方程,通过热传递及热力耦合数值模拟结合激光干涉仪测试,量化了矿物铸件机架在外部热源波动、表面对流及热力耦合效应下的非线性变形机理,揭示了恒温控制对保证大型构件在环境热波动下结构精度的至关重要性。进一步将热研究拓展至进给系统,量化高精平台在复杂热环境下的热力学行为及动态精度。通过建立结合部混合支撑下进给系统动力学微分方程,揭示了重心驱动的重要性。为避免孤立平台结构,建立了包含完整进给系统的热力耦合数值模型,考虑了电机热、导轨摩擦热及环境热波动。通过动力学冲击分析量化了平台在热力耦合作用下的非线性变形及动态偏摆机制,并通过激光干涉仪进行了验证。结果显示,平台动态误差随环境温升非线性递增,温变4°C-8°C,平均偏摆误差达5.12-10.67μm/m,且保证高精平台理想动态精度的温度波动上限为4℃。同时,从电机多通道温度测试和导轨热通量解析发现,外部环境热波动是影响进给系统动态精度的最关键热源,而非系统内部热源。从全局角度定量研究了高精机床在真实工况下加工精度的变化机理。通过整机热力耦合建模及求解,量化了系统在综合热源波动、接触热阻及热力耦合效应下的温度场分布及结构的非线性变形。结果表明,环境温升5℃,平台呈二阶弯曲变形,显著影响其动态精度。基于运动结构的动力学冲击热力耦合数值模拟,得到了TCP(刀具中心)点在内、外部热源及热力耦合效应下的动态位置精度。数值和测试结果一致表明,孔位精度随外界环境温升而衰减,温升5℃时,部分轴位已经无法达到25.4μm的孔位精度要求。通过微孔钻实验进一步分析了不同热环境下机床动态钻孔精度的CPK(制程能力指数)值及变化规律,再次揭示了环境热波动对其自身加工精度的极端重要性。
[Abstract]:High speed, high precision CNC machine tool is an important factor affecting and restricting the level of electronic manufacturing industry and electronic information industry base supporting capacity. In recent years, along with the information, communications, medical, aerospace and other fields of electronic products to high function, high density and high reliability, the machining accuracy of NC machine tool, put forward higher requirements the efficiency and stability. The thermal error is the decisive factor affecting the dynamic high precision machining precision of the machine tool, the total error of 70%. therefore, to carry out research on engineering thermal error mechanism to solve the high precision machine tool exists is important technical bottleneck of poor thermal stability. The thermal and dynamic properties are complex temperature field in the structure of production the stress, comprehensive reflection of nonlinear deformation and thermo mechanical coupling effect between components, so the thermal phenomena cannot be isolated to study local system. This paper analyzes the machine system from a global perspective The internal structure of the unit and in the thermal coupling effect under static and dynamic accuracy characteristics and evolution, the main contents are as follows: the analysis of nonlinear stiffness of linear rolling guide. Based on Hertz contact theory, considering the contact elastic deformation and preload effect established rail initial stiffness model, quantization, initial stiffness of raceway the nonlinear change characteristics with loads. The contrary tendency ball differential sliding friction, elastic hysteresis and spin energy analysis, equivalent heat intensity calculation of the rolling interface, and Achard wear theory calculation model was established based on wear of rail contact interface. Numerical simulation and thermodynamic coupling rail wear depth analysis was established the final results show that the stiffness model based on lower raceway contact stiffness transfer in friction heat, thermal elastic contact deformation and abrasion with different degree of stroke The nonlinear decreasing vibration test by LMS. Complete the verification frequency stiffness model, successfully detected guide because the contact stiffness decreased by rigid mode (2.36-6.58) k Hz (2.05-5.66) k migrated to Hz, and the stiffness model is put forward based on a more rigid guide mode frequency analytical precision, the measured frequency with the analytical value of the maximum error is 15.2%. at the same time, the results show that the effect of friction heat and wear effect of track stiffness change with time. The effect of thermal expansion to the basic structure, the new type of mineral casting material under dynamic thermal environment frame thermodynamic properties and structural static analysis. The reliability of precision materials to replace conventional materials used in the precision machine tool is verified by the flatness measurement and linear modal analysis. The results show that the mineral casting structure static stiffness can meet the precision machine tool large foundation member 50 m flatness The precision, the dynamic characteristics of the modal characteristics were better than cast iron, natural granite, low order natural vibration frequency is higher than 90Hz, which in a typical vibration system under dynamic stability. The temperature field of mineral casting structure based on the finite element method is deduced by means of heat transfer and thermal mechanical coupling numerical simulation combined with laser interferometer testing, to quantify the mineral casting frame in external heat wave, the deformation mechanism of nonlinear surface convection and thermal coupling effect, reveals the temperature control to ensure the vital importance of large dynamic structure in the environment. The accuracy of thermal wave will further expand to the hot research feed system, thermodynamic behavior quantitative high precision platform in complex thermal environment and the dynamic precision. Dynamic differential equation of mixed feed system supported by establishing a connection, and reveals the importance of gravity driven. Avoid isolated platform structure, established the thermal mechanical coupling numerical model including complete feed system, considering the motor heat, friction heat and thermal environment fluctuation. Through dynamic impact analysis to quantify the nonlinear deformation and dynamic platform under thermo mechanical coupling deflection mechanism, and through the laser interferometer was verified. The results show that the platform the dynamic error with the environment temperature increasing, temperature of 4 DEG C-8 DEG C, the average yaw error reached 5.12-10.67 mu m/m, and ensure the maximum temperature fluctuation and high precision platform ideal dynamic accuracy is 4 DEG C. At the same time, found from the motor multi-channel temperature testing and guide heat flux analysis, thermal fluctuation is the external environment the pivotal effect of the drive system dynamic accuracy, rather than the internal heat source system. The change mechanism of processing in the real working condition of high precision precision machine tool research from a global perspective. Through the quantitative thermodynamic Ou Hejian Model and solution, quantitative fluctuation of system in heat deformation, thermal contact resistance and thermal coupling effect under the nonlinear temperature field distribution and structure. The results show that the environment temperature is 5 DEG C, platform two order bending deformation, significantly affect the dynamic precision. Dynamic motion of structure impact thermo mechanical coupled numerical simulation based on the obtained TCP (tool center point), the dynamic position precision of external heat source and thermal coupling effect. The numerical and test results show that the accuracy of hole position with the external environment temperature rise and decay, the temperature rise of 5 degrees, some axis has been unable to reach 25.4 mu m. Through the micro hole drilling hole position accuracy the further analysis of the machine tool dynamic precision drilling in different thermal environments CPK (process capability index) value and change the regulation, once again reveals the extreme importance of environmental thermal fluctuations on its machining precision.

【学位授予单位】：哈尔滨工业大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TG502.13

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