【作者】 张华伟；

【导师】 夏伟；

【作者基本信息】 华南理工大学 ， 机械制造及其自动化， 2014， 博士

【摘要】 压铸技术是材料制备与零件成形一体化的先进制造技术，压铸机是压力铸造的基础设备，技术含量较高，属机、电、液一体化的精密、复杂设备。我国压铸设备尤其是大型压铸设备在设计方法、制造工艺、工作效率、能耗、可靠性等方面与发达国家相比还存在较大差距。针对国内压铸设备落后的现状，结合国家智能制造装备发展专项“高效智能压铸岛系统”、粤港关键领域重点突破项目，本文以25000kN大型压铸机为研究对象，以高效节能压铸机的关键技术为主要研究内容，结合目前压铸机设计和产品制造过程中存在的突出问题，采用数值模拟技术，从合模机构运动学仿真、优化设计、整机结构强度分析、整机模态、冲击响应、热传导和热-结构耦合等动态特性分析、重要结构部件轻量化设计、控制系统关键节能技术等方面进行理论研究、计算机模拟和实验研究；最终完成了样机开发，并取得以下研究成果：基于运动学仿真开展压铸机双曲肘合模机构优化设计与研究。系统全面地分析了双曲肘合模机构的运动特性和力学特性，建立了相应的数学模型，推导出了合模机构的各部件几何尺寸、位置与扩力系数、模板行程之间的关系，结合实际样机设计要求，选取行程比和扩力系数为目标函数，确定了适宜的设计变量和约束条件；利用ADAMS软件对双曲肘五铰点斜排列合模机构进行运动和力学特性分析，并对合模机构进行了优化设计，将扩力系数由18.93提升至23.59，提升了24.6%，达到国外同类先进水平，锁模力由25.89MN提高到了32.27MN，液压系统选用低功率的液压马达和阀在更短的建压时间输出更小的压力可满足合模力25000kN要求，动型座板行程减少了26.3%，与优化前比较发现：合模过程的冲击和振动减小，在一定程度上可以节能降耗，提升工作效率。为提高压铸件的品质和压铸机的可靠性提供了技术依据。基于多体动力学进行压铸机整机强度分析。对比研究了多刚体系统和多柔性体系统仿真结果，获取了合模机构关键部件速度、加速度及力学性能时间历程曲线，研究发现柔性体系统的仿真结果能真实反映机构的运动和力学特性。基于多柔性体动力学分析方法对25000kN压铸机进行强度分析和校核，并通过CAE软件对合模机构进行了强度分析，分析结果有效验证了柔性体动力学分析结果。进行整机综合动态特性分析。采用改进的Craig-Bampton方法计算出了包含大量高度非线性接触副的25000kN压铸机合模机构装配体的约束模态，获取了前20阶模态的共振频率和对应的阵型。识别出整机各部件对振动激励响应的敏感程度以及抗振薄弱区，避免共振，为压铸设备优化设计和压铸件生产提供了依据；对合模机构进行冲击响应分析，发现动型座板、长铰、钩铰及尾板和哥林柱受冲击载荷影响大；对“热冲击”载荷和结构载荷共同作用下的模板和模具系统进行温度场分析、热-结构耦合特性分析，动型座板和定型座板局部最大应力分别为254.1MPa和181.6MPa。校核冲击载荷、热-结构载荷耦合作用下各部件的强度，均满足要求。可以对动型座板进行适度优化，对定型座板和尾板进行轻量化设计。对压铸机重要结构部件进行轻量化设计研究。运用连续体结构的变密度拓扑优化方法和尺寸优化方法对压铸机重要部件—尾板、定型座板、动型座板和底座进行了优化，研究了约束体积百分数和惩罚因子对拓扑优化结果的影响，确定了适合压铸设备模板连续体结构轻量化设计的约束体积百分书和惩罚因子分别为0.7和3。经过结构拓扑和尺寸优化后整机总重量由91.10t减少至79.75t，减重率达到12.5%，其中运动部件减重率达到6.4%。轻量化设计后可以有效降低液压系统油泵负荷，节能降耗，提高工作效率。开展压铸机控制系统关键节能技术研究及测试。在研究压铸机耗能原理的基础上，提出采用变频控制技术结合嵌入式实时控制器的实现压铸设备节能的技术方案，即在控制系统硬件和软件设计基础上，应用双DSP专用能效系统中央处理器和无感矢量闭环转矩控制技术，配合压铸设备专用程序软件，大幅度降低循环生产过程中的小流量状态下的电力消耗。进行实验测试，发现节能效果最大达到41%，工作效率基本保持不变，实现节能降耗的目的，与国内外常规压铸机相比，可节电25%~35%。该技术在周期性变负荷运行机械设备节能研究方面具有通用性和指导意义，具备较大的推广应用空间。更多还原

【Abstract】 Die casting is one of advanced manufacturing techniques that enables component to beformed in one piece for specific materials. The casting machine is the fundamental equipmentof pressure die casting. It is sophisticated with high technique and involves mechanical,electrical and fluid flow dynamic properties. There is a wide gap between China anddeveloped countries in the design method, manufacture technique, work efficiency, energyconsumption and reliability of die casting equipment especially in large scale.Since the die casting equipment developed in the country is far behind advanced, a25000kN large scale die casting machine has been studied. The project is in combination ofnational intelligent manufacture equipment development project in ‘high efficiency diecasting island system’ and breakthrough project in key area in Canton and Hong Kong. Thereport is focus on crucial technique that could provide higher work efficiency and lowerenergy consumption using numerical simulation. Final model has been developed based ontheoretical, numerical and laboratorial research have been done in dynamic properties such askinematic simulation of mould clamping device, design optimization, mechanical strengthanalysis of complete machinery, modal of the machinery, impact respond, heat and thermalconduction structural coupling, lightweight design for main structural components and controlsystem for crucial techniques of energy consumption reduction.Double-toggle clamping device in the die casting machine based on kinematic modellinghas been researched and optimised designed. System kinematic and dynamic properties of thejoint-double clamping device have been analysed and a mathematic model has been set up.Relations between coefficient of expanding force, distance of the dies movement andgeometries are derived and practical variables and constraints have been determined in thefunction with stroke ratio and coefficient of expanding force. By analysing the kinematic anddynamic property of joint-double, five-hinge-joint, inclined-array clamping device withADAMS and optimising the design, the coefficient of expanding force is increased by24.6%from18.93to23.59, matching the world leading level and results in growing locking force from25.89MN to32.27MN.The25000kN clamping force can be provided using low power hydraulic motor andvalve in the hydraulic system with less pressure and time. Working efficiency and energyconsumption are therefore improved. The driving base plate has reduced its stroke by26.3%which lessen the impact and oscillation during clamping. It also enhances the quality andperformance of the die casting machine.Die casting machinery strength has been researched based upon multi-body dynamicanalysis. The curves of velocity, acceleration and load property of the key components withinthe die casting machine against time have been derived. Result showed that by modellingflexible body system similar kinematic and dynamic properties with the one in reality can besimulated. Strength of the25000kN die casting machine has been analysed and modifiedbased on flexible body kinematic study as well as that of the clamping device using CAEsoftware. Results showed significantly that the flexible body analysis had given validoutcomes.Dynamic property analysis of the whole machine has been studied. ImprovedCraig-Bampton method has been used to calculate the constraint model of the25000kN diecasting clamping device assembly with large amount of highly non-linear contact pair.However, finite element method can hardly solve it. Resonant frequency in the first20phaseswith corresponding formations heaved also been obtained. Degree of sensitivity of theassembly responds to the vibration excitation and the weakness of vibration resistance havebeen identified to prevent resonance. It also gives evidence to improve design andmanufacture of die casting. According to the shock respond analysis of the clamping device,the main impact effcts are on the driving base plate, long hinge, hock hinge, fixed plate andthe Gelin Columns. By analysing thermal field and thermal structural coupling properties ofthe casting plates and the mould system with ‘thermal shock’ loading and mechanical loading,the maximum pressures applied to driving base plate and the fixed plate have been set to254.1MPa and181.6MPa, respectively. Work conditions of every assembly under theseconditions are acceptable. However optimization should be done to the driving base plate and should lighten the fixed plate and the transom plate.Crucial assemblies have been lightweight designed for the die casting machine.Topological and geometrical optimizations for continuum structure have been used tooptimise the crucial assemblies of the die casting machine such as fixed plate, transom plate,driving base plate and the base. The percentage of the bound volume and the penalty factor ontopological optimization are significant therefore they are determined to be0.7and3,respectively. Result after optimizations showed that total weight of the mould plates and thebase has reduced from91.10tons to79.75tons. With a12.5%drop in weight of the wholemachine and6.4%drop in weight of moving parts. Therefore, the work load of the hydraulicdriving system has reduced dramatically. As result the working efficiency of the wholemachine can be improved and energy consumption can be lowered.Key technique on energy saving for the die casting machine control system has beenstudied. A technique of using variable frequency control with real time monitor embedded tosave energy has been purposed. Above the hardware and software in the control system,non-inductive vector close-loop torque control technique, specific double DSP energyefficient system CPU together with specific die casting software have been introduced. Theelectricity cost during the small discharge in periodic manufacturing has been dramaticallydecreased.41%of the electricity cost can be saved using this technique and25%~35%ofelectricity can be saved when comparing with normal die casting machine. Thus the goal oftechnical innovation and energy saving can be achieved. This technique can be introduced tothe analysis of energy saving for periodical variable loading operation devices and can beused broadly in the future.更多还原