超声微注塑机合模-锁模-顶出机构的设计与分析

提出一种由直线超声电机驱动合模的新型超声微注塑机。首先对超声微注塑机的结构和工作原理进行分析,其次对合模-锁模-顶出机构进行了设计,最后利用ANSYS Workbench软件对合模系统中质量最大的动模板进行拓扑优化以减轻其质量,并对优化后的动模板进行静力学分析。结果表明,该超声微注塑机的合模-锁模-顶出机构能够实现特定的运动,拓扑优化后合模系统总质量满足要求,且其材料强度满足要求。     

微流控芯片超声振动注射成型模具设计

针对目前微流控芯片注射成型中微通道充填困难、成型精度低等问题,研究超声振动辅助注射成型微流控芯片的方法,设计出微流控芯片超声振动模具。创新性地引入热流道系统,实现了超声振动系统与注射成型模具的有效集成;独特的流道和型腔布置实现了芯片的基片和盖片同模同时成型;改进的二次顶出机构实现了芯片的无损脱模。     

超声外场对微圆柱阵列结构制件填充质量的影响

针对微小尺寸或局部带有微小结构的制件模塑成型时熔体充模流动困难而影响制件质量的问题,以典型的带有微圆柱阵列结构的薄板型制件为对象,提出将抽真空排气和超声振动技术集成应用到自行设计制造的微注塑模具中,并采用单因素成型实验方法,研究了高密度聚乙烯(HDPE)和聚丙烯(PP)两种聚合物材料在施加与不加超声外场以及不同工艺参数和超声功率变化条件下填充薄板型制件上微圆柱圆角曲率半径的变化规律.结果表明,不加超声外场时提高熔体和模具温度及增大注射速率可使两种材料填充的微圆柱圆角曲率半径逐渐减小,施加超声外场时填充的微圆柱圆角曲率半径可进一步减小,从而有效提高了制件的填充质量;同时发现,无论有无超声作用,HDPE材料填充的微圆柱圆角曲率半径均明显小于PP材料.     

桌面型微注塑机锁模机构设计与分析

为了设计桌面型微注塑机的锁模机构,在对注塑机锁模肘杆机构的运动学特性和力学特性进行理论分析的基础上,确定了最佳的肘杆几何参数,对肘杆机构进行了运动学仿真分析和静力学分析.结果表明,设计的桌面型微注塑机的肘杆锁模机构能够满足慢—快—慢的理想速度特性,并且在能够提供100 kN锁模力的前提下,满足刚度和强度的要求.     

基于表面活性剂的纳米包膜微泡超声造影剂

采用声空化的方法,以3种酯类表面活性剂作为微泡的纳米包膜材料进行了静脉注射微泡超声造影剂的制备研究,实验研究了超声功率与超声时间的选择、磷酸盐缓冲溶液pH值对微泡产量的影响、通气方式的选择、稀释液对微泡流动性的影响、振动对微泡的影响,研究了微泡的保存方式,并对制备出的微泡超声造影剂进行了体外及动物体内造影成像效果研究,给出了实验犬肾脏造影灌注的结果.     

基于SIMP理论的注塑机固定模板的拓扑优化

运用ANSYS软件对塑料注塑机固定模板结构进行拓扑优化。将不同体积约束下拓扑优化的结果进行了研究对比,获得了模板在强度和刚度不变乃至增加的前提下材料的最优分布结构。按照分析结果所作的合理设计不仅可以节省材料,还可以通过减小模板最大挠度来提高注塑产品质量。     

二板式注塑机微开技术在发泡注射成型中的应用

随着工业的发展,各行各业对塑料制品的要求越来越高,既要求保证产品尺寸精度,又要求能保证产品的强度和刚度,最重要的还要达到轻量化的目标,节约投资成本。微发泡注塑成型技术是一种革新的精密注塑技术,突破了传统注塑的诸多局限,同时二板式注塑机由于其许多与生俱来的优势,被越来越多的客户所接受,应用越来越广泛,发泡注塑成型技术同二板式注塑机微开技术的结合为上述制品的要求提供了一套很好的解决方案。介绍了发泡注射成型的原理,总结了现阶段发泡注射成型的优缺点;介绍了二板式注塑机的结构特点;提出了一种应用在发泡注射成型中的二板式注塑机新技术,详述了其工作原理、系统配置要求以及应用优势。     

微量注塑机的现状与发展趋势

微注射成型技术是微结构零件最主要的成型方式,受到了人们高度重视,微结构零件迅速发展对微量注塑机带来了新的挑战。阐述了微注射成型技术的产生背景,分析了微注射成型技术对注射设备的特殊要求,从微量注塑机的螺杆式、柱塞式和螺杆柱塞混合式塑化与注射单元机构和液压、电动和电液复合驱动方式等方面介绍了当前微量注塑机的发展现状并比较了它们的优缺点,分析了微量注塑机面临的挑战并展望了微量注塑机的发展趋势。     

基于表面活性剂的微泡型超声造影剂

综述了可用于超声造影剂微泡的表面活性剂的材料及制备方法,介绍了形成表面活性剂微泡中的气体材料的选择及其于表面活性剂类微泡超声造影剂。     

液压脉动注塑机能耗分析

对新研制的液压脉动注塑机进行了介绍;在其它加工工艺不变的条件下,分别调节预塑和注射过程中的振幅和频率,通过能耗分析仪,直观地观察到动态加工过程的能耗与稳态加工能耗的区别;研究比较了直接加热与纯振动场作用下,两种不同换能方式对聚合物固体材料塑化性能的影响,得出了纯振动场作用比直接加热更能促进聚合物材料塑化的结论.并用黏弹性理论解释了振动强度对能耗的影响.     

换能器结构参数对聚合物超声塑化黏弹生热的影响

为研究超声换能器结构参数对聚合物超声塑化过程黏弹性生热的影响,首先确定超声黏弹性生热系统的组成,进行纵振超声换能器结构设计;然后分析超声黏弹性生热过程及超声黏弹性生热原理;最后采用单一变量法分析超声换能器的主要结构参数对其纵振频率及工具头前端质点最大振幅的影响,将其实际输出的纵振激励加载于熔融聚合物,研究其结构参数对聚合物超声黏弹性生热过程及达到聚合物玻璃化转变温度所用时间的影响。结果表明,随纵振激励作用时间的增加,聚合物温度非线性升高;放大比对聚合物温度变化影响最大,前盖板厚度和工具头长度次之,影响最小的是变幅杆长度。     

微注塑成型机的研究现状与进展

在阐述了微注塑成型技术特点及定义的基础上,提出了微注塑成型技术对成型机的特殊要求,介绍并分析了微注塑成型机的市场现状。根据结构特点,对微注塑成型机进行分类,并对其技术参数做出说明,同时,展望了微注塑成型机的发展趋势。     

Wall Slip of Linear Polymer Melts During Ultrasonic‐assisted Micro‐injection Molding

The wall slip of linear polymer melts under ultrasonic vibration is investigated by correcting the slip mechanism, and melt flow behaviors in ultrasonic‐assisted micro‐injection molding (UμIM) method are discussed. Based on the effect mechanism of ultrasonic vibration on the melt, theoretical models of the critical shear stresses for the onset of weak and strong wall slip during UμIM are established, and the change in rheological properties due to the onset of wall slip under ultrasonic vibration is experimental investigated by a built measurement system. The results show that the onset of weak and strong wall slip of the melt in micro cavity are promoted by ultrasonic vibration, which agree with the built theoretical models, and the melt filling capability in micro cavity is enhanced by reducing apparent viscosity and releasing shear stress of the polymer melt, which improves the molding quality of micro polymer parts via UμIM method. POLYM. ENG. SCI., 59:E7–E13, 2019. © 2018 Society of Plastics Engineers     

Polymer–Metal Interfacial Friction Characteristics under Ultrasonic Plasticizing Conditions: A United-Atom Molecular Dynamics Study

Understanding the properties of polymer–metal interfacial friction is critical for accurate prototype design and process control in polymer-based advanced manufacturing. The transient polymer–metal interfacial friction characteristics are investigated using united-atom molecular dynamics in this study, which is under the boundary conditions of single sliding friction (SSF) and reciprocating sliding friction (RSF). It reflects the polymer–metal interaction under the conditions of initial compaction and ultrasonic vibration, so that the heat generation mechanism of ultrasonic plasticization microinjection molding (UPMIM) is explored. The contact mechanics, polymer segment rearrangement, and frictional energy transfer features of polymer–metal interface friction are investigated. The results reveal that, in both SSF and RSF modes, the sliding rate has a considerable impact on the dynamic response of the interfacial friction force, where the amplitude has a response time of about 0.6 ns to the friction. The high frequency movement of the polymer segment caused by dynamic interfacial friction may result in the formation of a new coupled interface. Frictional energy transfer is mainly characterized by dihedral and kinetic energy transitions in polymer chains. Our findings also show that the ultrasonic amplitude has a greater impact on polymer–metal interfacial friction heating than the frequency, as much as it does under ultrasonic plasticizing circumstances on the homogeneous polymer–polymer interface. Even if there are differences in thermophysical properties at the heterointerface, transient heating will still cause heat accumulation at the interface with a temperature difference of around 35 K.     

Ultrasonic characterization of the crystallization behavior of poly(ethylene terephthalate)

On the basis of the previous observations that the ultrasonic signals are sensitive to the crystallization of polymers (Tatibouet and Piché, Polymer 1991, 32, 3147), we have expanded our efforts to study the detail relationship between the ultrasonic signals and crystallization process in this work. The nonisothermal and isothermal crystallization of virgin poly(ethylene terephthalate) (PET) and PET samples after degradation were studied by using a specially designed pressure‐volume‐temperature (PVT) device, with which an ultrasonic detector was combined. The results showed that the evolution of the ultrasonic signals not only can be used to probe the crystallization process but also can qualitatively characterize the crystallization rate, crystallinity, crystallite size, and amorphous. DSC measurement was used to verify such results. Ultrasonic signals could be as a complementary tool to polymer chain movement and well be applied to characterize the crystallization behavior. Furthermore, the ultrasonic measurement has the potential use to characterize crystallization of products in‐line during processing (i.e., injection molding, micromoulding). © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Ultrasonic measurement of orientation in HDPE/iPP blends obtained by dynamic packing injection molding

The orientation of polymer chain has a great effect on its mechanical properties, therefore, it is always an important issue on how to characterize, accurately and quickly, the orientation of polymer chain during processing. In this article, according to the property that ultrasound travels in different velocities in anisotropic media, normal incident shear wave was utilized to explore the orientation structure of HDPE/iPP blends obtained by dynamic packing injection molding. The ultrasonic technique is consistent with the 2D-WAXS in charactering the orientation degree of polymer chains, although ultrasonic technique focuses on the overall orientation of polymer blends while the 2D-WAXS reveals the crystalline orientation of each component. Our work demonstrates that ultrasonic technique might be a reliable, fast and easy way to characterize the orientation structure of crystalline polymer blends. The ultrasonic measurements were performed off-line, but the achievement provides the possibility for on-line detection of orientation structure in injection molding by using ultrasonic technique.