【作者】 翟明；

【导师】 顾元宪； 申长雨；

【作者基本信息】 大连理工大学 ， 工程力学， 2002， 博士

【摘要】 注射成型是热塑性塑料和一部分热同性塑料最主要的成型加工方法。由于材料本身的特性以及复杂的加工条件，塑料注射成型过程加工过程相当复杂。长期以来，塑料注射成型过程的控制和模具设计与制造主要依赖工艺人员和设计人员的经验和技巧，设计的合理性只能通过试模才能知道，制造的缺陷主要靠修模来纠正，致使模具及塑料产品的设计与制造周期长、成本高、档次低。随着新材料和新成型方法的不断出现，问题更加突出。 建立塑料注射成型过程的物理和数学模型，构造有效的数值计算方法，对该过程进行数值模拟，预测制品的结构和性能，可以在设计阶段及时发现问题，避免了在模具加工完成后在试模阶段才能发现问题的尴尬。 但对注塑成型过程的数值模拟仅仅相当于数值实验，只能校核设计方案的合理性，无法“主动”给出合理的模具结构和成型工艺，最终的设计方案仍需设计者根据自己的经验和技巧，通过对多个方案的反复计算、分析、比较和判断来确定。设计方案的确定在很大程度上取决于数值模拟时设计者提供的输入数据以及对输出结果的正确判断与解释。将设计优化技术和数值模拟技术相结合，使计算机有了“主动”设计功能；自动确定最优成型工艺参数(如注射速率、保压压力、保压时间、模具温度等)；自动确定最优模具结构等。这就大大降低了对注塑成型设计人员的要求，提高了设计质量。注塑成型计算机辅助优化设计技术具有较高使用价值，对我国塑料工业的发展具有重要意义。 尽管对注塑成型过程进行模拟和优化可以得到好的成型工艺，但在实际加工过程中，由于机械磨损、摩擦或环境因素的变化，注射加工常常无法按照我们所期望的工艺进行。对注射机进行实时控制，使加工变量以一定的精度保持某一数值或按一定的规律发生变化，具有较高的实用价值。 本文对塑料注射成型充填过程的数值模拟、优化与控制进行了研究，研究工作由三部分组成：1、改进了注塑成型充填过程的数值模拟算法。2、根据对注塑制品常见质量缺陷及其形成原因的分析，建立了优化模型，采用与数值模拟方法结合的设计优化技术，对模具浇口设计和加工工艺进行了优化。3、将自动控制理论应用于注射成型加工，消除或减小外界干扰影响，使加工过程按照优化的工艺进行，保证了制品质量。 大连理工大学博士学位论文为了叙述方便，各章节的内容支排如下： 第一章在查阅人量文献的基础上，概述了注塑成型模拟、优化与控制技术的研究历史和现状；介绍了国内外主要的注射模分析和设计软件，并对其特点进行了比较分析；总结了注塑成型研究和注射模软件的发展趋势。另外，介绍了注塑成型的一些基本知识，总结了注塑制品常见缺陷及注塑成型设计的一些准则。 第二章研究了注塑成型充填过程数值模拟算法的改进。根据熔体在每个控制体积内质量守恒，建立了以结点压力和充填分数为未知量的控制方程；在每一时间步，对该方程进行迭代求解，得到压力场和充填分数场：根据充填分数场确定熔体前沿面的位置，得到熔体在型腔内的充填情况。 第三章到第五章对模具结构和充填阶段的加工工艺优化进行了研究。 第三章研究了注射模浇口位置的优化设计方法。通过对注塑成型过程进行分析，指出在加工条件和型腔结构相同的情况下，充填结束时注射压力最小的浇日位置设计能够实现塑料熔体的平衡充填；在此基础上，构造了浇日位置优化的数学模型，以充填结束时注射压力最小作为优化目标，对浇口位置进行优化设计，从而达到熔体平衡充填、减小塑件翘曲变形的目的；用有限差分法计算了设计灵敏度，用序列线性规划对优化模型进行求解；给出了确定单浇口位置可行设计空间的一种方法：以熔体同时到达型腔末端为目标，在总注射速率一定的情况下对给定浇口处的注射速率进行忧化，根据优化结果估计熔体在型腔中流动的流长和所受的阻力，从而确定单浇口位置的可行设计空间。 第四章给出一种同时对注射模浇口数口和位置进行优化设计的方法。通过对充填过程进行分析，为达到减少塑件翘曲变形和熔接线的目的，以平衡充填和浇口数目最少为忧化目标，以最大注射压力作为约束条件；将浇口位置作为连续变量处理，以其坐标为设计变量；在充填模拟计算中根据浇日之间的距离对浇口数日和注射流率进行处理，实现对浇日数目的优化；将充填过程的数值模拟和遗传算法相结合，对优化模型进行求解，同时得到最优的浇口数口及其位置。 第五章研究了注射成型工艺优化问题。通过对注射成型过程进行分析，指出熔体前沿流动速度变化造成的分子取向不均，是塑件发生翘曲变形的原囚之一。由此，给出一种注射成型工艺优化模型，以保持熔体前沿速度均匀、从而使分于取向均匀和减少塑件翘曲变形为目的，对注射速率进行优化设计。采用序列线性规划算法求解优化问题。 11 摘要 对注射成型过程进行模拟和优化可以得更多还原

【Abstract】 Injection molding is the mostly used processing technology for all thermoplastic materials and part of thermoset materials. The process of the injection molding is quite complicated because of the character of the material itself and the complexity of processing conditions. For a long time, the control of the injection molding process and the design of the mold mainly depended on the experience of the designers, and the reasonability of the design can only be verified by trial and error. The cycle was quite long and the cost was huge.By establishing the physical and mathematical model of injection molding process and adopting effective numerical algorithm, the process can be simulated numerically so that the structure and the property of the part can be predicted and the possible problems can be found at the design stage. The embarrassment of finding problems in the stage of mold trial after the manufacture of the mold can be avoided.However, the numerical simulation of the injection molding just behaves as numerical experiments. The designer’s experience is still required and the determination of the design is mainly based on the input provided by the user and his correct judgement and explanation on the output. Combining the design optimization technology and the numerical algorithm, computer can determine the molding parameters and the gate locations automatically. These can remarkably reduce the requirements to the design personnel of the injection molding and improve the design quality.Although the improved molding process can be obtained by simulating and optimizing the injection molding process, usually, the process still cannot be proceeded as what we expect because of the mechanical erosion, friction and the variation of the environment factors in the real process. The on-line control on the injection molding to make the manufacture variables vary according to what we expected is very valuable practically.This dissertation studies on the simulation, optimization and control of the filling stage in plastic injection molding. The research work is composed of three parts: 1. Implicit algorithm is utilized to track the movement of the melt front in the filling stage. 2. According to the mostly occurred injection molded part defects and the analyses on the factors that cause those defects, optimization model has been established and mold configuration and processing conditions are optimized subsequently. 3. Theory of automatic control has been involved intoinjection molding to make the molding process proceed according to the optimized processing conditions. The disturbance from the environment is eliminated or reduced and parts quality is guaranteed. The contents of each chapter are as follows:In Chapter 1, based on literature reviews, the history and current status of the simulation, optimization and control technology of injection molding is illustrated. The popular software on analysis and design of injection molding are introduced and comparison has been made among them. The development tendency of the injection molding software is concluded. In addition, some elementary knowledge on injection molding is introduced.In Chapter 2, implicit algorithm is employed to track the moving melt front to achieve the numerical simulation of injection molding. According to the mass conservation of each control volume, governing equation of which the variables are nodal pressure and fill factor is established. By solving the equation iteratively, the pressure field and fill factor field are obtained. The position of the melt front is therefore determined by fill the factor field. The filling situation in the cavity in each time instant can be obtained as well. The employed implicit algorithm can describe the transient process in filling stage more reasonable and avoid the limit of Courant condition. The calculation efficiency is improved.Chapter 3, 4 and 5 are focused on the optimization of mold configuration and processing conditions of filling stage.In Chapter 3, the optimizing design o更多还原