【作者】 魏静；

【导师】 张光辉；

【作者基本信息】 重庆大学 ， 机械工程， 2008， 博士

【摘要】 由于双螺杆啮合几何学以及物料输送行为的复杂性,造成双螺杆捏合挤出过程研究的困难。因此研究具有集输送、捏合、建压及自清洁功能于一体,且能对被加工物料产生高剪切力的新型捏合机具有重要意义。差速双螺杆捏合机是一种新型的可对高粘度物料进行输送、混合、捏合及塑化等操作的双螺杆挤出混炼机构。差速双螺杆捏合机核心部件是一对相互啮合的阴、阳转子,如何有效地设计和加工阴、阳转子螺旋副是提高差速双螺杆捏合机性能的关键。论文从捏合机关键技术出发,系统地研究差速双螺杆捏合机阴、阳螺杆转子螺旋副型线设计、优化,模拟及高效高精度加工等原理与技术。利用齿轮啮合理论和双螺杆泵设计原理建立差速双螺杆捏合机螺杆转子型线设计数学模型;研究了差速双螺杆捏合机阴、阳螺杆转子啮合几何学。对阴、阳螺杆转子型线参数进行分析及优化,利用优化设计方法建立阴、阳螺杆转子型线参数优化模型,给出输送效率最高、剪切捏合能力最强的阴、阳螺杆转子螺旋副组成齿曲线及其设计参数,并利用型线设计理论对设计实例进行分析和评价。对剪切捏合性能进行研究,推导出剪切性能最优的安装中心距的计算式。给出组合性能最优的阴、阳转子螺旋副组成齿曲线参数方程及设计结果。以差速双螺杆捏合机中输送的非牛顿流体为研究对象,利用有限元分析软件,对输送物料的速度场、压力场等流场特性进行模拟和分析。从螺旋曲面的参数方程出发,利用空间解析几何理论将差速双螺杆捏合机阴、阳转子三维螺旋面坐标转化为对应不同压力腔的二维积分区域,利用数值积分求解作用在转子上的轴向、径向受力以及力矩,为螺杆转子强度计算及捏合机轴承选取提供理论依据。阴、阳转子高效精度加工是差速双螺杆捏合机关键技术。论文在分析螺杆转子加工技术现状及加工特点基础上,提出利用基于CBN等超硬刀具材料的螺杆转子高效高精度成形磨削加工方法。根据齿轮空间啮合原理及微分几何理论建立成形加工刀具求解计算理论;利用等距齿面法对成形刀具的实际廓形进行设计以及利用双圆弧样条理论对成形刀具廓形进行光顺处理。建立螺杆转子螺旋面成形磨削加工误差分析数学模型,研究分析安装角误差、安装中心距误差、轴向位置上砂轮半径误差等因素对螺杆转子齿形误差的影响。对螺杆转子成形磨削CBN砂轮修整进行研究,分析利用金刚石修整轮进行CBN砂轮修整设计及修整特性。结合当前CBN、PCD等硬质合金刀具材料发展起来的干切削、硬切削等加工方式对螺杆转子螺旋面进行切削加工研究。建立利用指状成形刀具加工螺杆转子数学模型。建立基于多自由度法和空间齿面法线法的精确滚刀轴向截形,揭示出利用滚削法加工螺杆转子螺旋面滚刀基本蜗杆与螺杆转子螺旋面的啮合规律。为实现基于CBN、PCD等硬质合金刀具的螺杆转子高效高精度切削加工奠定基础。提出差速双螺杆捏合机CAD/CAM系统需求分析及体系结构、设计流程和加工控制流程;分析CAD/CAM系统设计关键技术;基于以上设计及加工理论,利用C#语言和.NET平台开发出一套可用于差速双螺杆捏合机设计、分析与阴、阳螺杆转子高效高精度加工的CAD/CAM系统。根据差速双螺杆捏合机CAD/CAM系统,利用指状成形铣刀以及基于CBN刀具材料的成形砂轮对差速双螺杆捏合机阴、阳螺杆转子进行加工实验。利用三坐标测量仪对螺杆转子精度进行测量,检测结果表明本文方法可以满足螺杆转子高效高精度加工要求。论文中螺杆转子加工方法可以推广应用于其它类型螺杆转子、圆柱蜗杆、斜齿轮等螺旋曲面高效高精度加工。更多还原

【Abstract】 It is difficult to study the twin-screw extrusion because of the complexity of geometry and the conveying performance of screw rotors. Differential twin-screw kneader is one kind of novel twin-screw mixing extruder which can be used for high viscosity material conveying, mixing and malaxating, kneading, voltage buildup and self-cleaning functions as well as can generate high shear stress for high viscosity material. The key parts of the differential twin-screw kneader are one couple of intermeshing screw rotors. And how to design and machine the screw rotors is the key problem to enhance the performance of whole machine. This dissertation investigates the theories and applications on the profiles design, optimization and simulations as well as high-performance and high-precision machining of screw rotors from analyzing the key technology for the differential twin-screw kneader.The theories of profiles designing and mathematical model for the differential twin-screw kneader are established using theory of gear engagement as well as design method of twin-screw pump. The geometry and meshing properties of the differential twin-screw kneader are studied. The optimization model is built using optimum design method. The design parameters of female and male screw rotors are analyzed and the variable proportions of volumetric efficiency Cn are studied with distance A and tooth number ratio Imf changed. The equation of optimal distance A is deduced when the shivering and crumbing performance are considered. The equations of the profile curves of the female and male screw rotors as well as practical examples are put forward.The research is performed for the non-Newtonian fluid transported by the differential twin-screw kneader based on Finite element analysis (FEA) software. The performance simulations, velocity field and pressure field of the fluid, are analyzed. The static load of twin-screw kneader is introduced and a mathematical model on the force and torque moments is presented using numerical integration method based on differential geometry theory. The calculations of the force and torque moments of the twin-screw kneader are given. The static load calculated by the method presented is inclined to be conservative compared with the traditional methods and the results can provide theoretical basis for the strength calculation of screw rotors and the bearing selection.The high-performance and high-precision machining is the key technology of the screw rotors for differential twin-screw kneader. After analyzing the current manufacturing technology status, form shaping grinding method is presented based on superhard tool materials diamond/Cubic Boron Nitride(CBN). The theories on solving form shaping tool are established using space gears engagement and differential geometry theory. The contact properties between the helicoids and the shaping tool are analyzed. Offset surface method is used to calculated the actual profiles of shaping tool. Smoothing treatment of the base body of CBN grinding wheel is performed using biarc spline method. The mathematical model of error analysis for CBN shape grinding maching of screw rotors is proposed. Influence curves of tooth errors with mouting angle error and mounting distance error as well as grinding wheel wear are presented. CBN grinding wheel trimmings for machining screw rotors are analyzed. The trimming errors using single diamond pen and diamond dressing gear are induced. The design of diamond wheel for CBN grinding wheel and the dressing characteristics are discussed.The mathematical models of milling and hobbing are established aimed at the high-performance and high-precision machining of screw rotors based on cemented carbide tool materials CBN and PCD. The mathematical model of figure shaping tool and hob accuracy design theories of axial section for screw rotors using engagement principles of helical gear drive based on multi-degree-of-freedom theories and normal method of space tooth surface are established, respectively. Above theories demonstrate the engagement features between the helicoids of screw rotors and the basic worm face of hob and provide a theoretical basis for other hob design method so as to lay a theoretical foundation by using reversible carbide tool.The requirement analyses, system structure, design and control flows of CAD/CAM system for differential twin-screw kneader are put forward. The key technologies on how to design the CAD/CAM system are analyzed. According to above design and machinine theories of screw rotors for differential twin-screw kneader, one CAD/CAM system using C# language and .NET framework which can be used to design, analyze and machine the screw rotors for differential twin-screw kneader is developed. Corresponding experiments using figure cutter and CBN grinding wheel for female and male rotors as well as precision measurement in three-Coordinate Measuring Machine (CMM) are performed based on the CAD/CAM system. The detection results show that the machining methods can meet the high-performance and high-precision requirement for screw rotors, colomn worms, helical gear, etc.更多还原