注塑冷却分析模内复膜数学模型建模

由于模内复膜工艺是在模具内将塑件表面增加一层薄膜,本文利用注塑冷却分析将模具型腔表面离散为平面三角单元的特点,将薄膜和塑件视为两层具有良好接触的平板,对于每一层平板,建立第一类边界条件下一维非稳态导热模型,并将该导热模型应用到冷却分析中,完成了模内复膜冷却分析的建模.     

聚丙烯/超临界氮气微孔注塑充模过程工艺参数研究

以聚丙烯(PP)为原料,超临界氮气(N2)为发泡剂,通过自行设计的一种扁平螺旋线形流道模具探究了注塑制品充模长度与减重比、泡孔结构之间的关系,并设计正交试验研究了注气压差、注气时间、注射压力和注射速率对制品充模长度的影响.结果表明,在一定范围内,熔体背压越高,制品充模长度越长,且随着充模长度增加,制品的减重比呈先缓慢增...     

注塑冷却快速边界元算法

在用边界元方法进行注塑冷却分析时,形成的矩阵方程为满阵,当单元数目超过一定值时,计算机则变得无能为力.针对这一问题,本文介绍一种新的计算方法,首先将单元分组,求出组内单元的平均温度,再利用得到的结果进一步计算组内每一个单元上的温度.采用这种方法,能够有效缩短计算时间,使计算时间仅为常规方法的1/4甚至更少.另外,通过单元合并减少了计算的数据量,改善了因计算机截断误差积累导致计算结果异常的情况,使得冷却分析能处理的单元数目较常规方法提高1倍以上.     

薄壁注塑制品模具设计及工艺研究

当前,在人们日常用品中,越来越多的使用到塑件,并且在电气和通讯设备的使用中,小型化和轻薄化都将会成为发展的关键。所以,在设计薄壁塑件磨具,并且分析其注塑工艺中,就需要考虑到厚度结构设计的改善,并且提升材料的实际性能,从而实现其结构和工艺等改进。在本文中,分析了薄壁塑件容易产生的典型问题,并提出了有效的解决对策,希望能够以满足日益增长的薄壁塑件的需要。     

The effects of gas counter pressure and mold temperature variation on the surface quality and morphology of the microcellular polystyrene foams

In this study, we developed a foaming control system using the Gas Counter Pressure (GCP) combined with mold temperature control during the microcellular injection molding (MuCell) process and investigated its influence on the parts' surface quality and foams structures. The results revealed that under GCP control alone when GCP is greater than 10 MPa, part surface roughness for transparent polystyrene (PS) improved by 90%. When GCP increased, the skin thickness also increased, the weight reduction decreased and the average cell size reduced to about 30 μm. For black PS parts, when GCP is greater than 10 MPa, the part gloss reaches the same value as that molded by conventional injection molding. By increasing gas holding time, the cell density decreased and the cell size distribution became more uniform. The increase in amount of supercritical fluid foaming agent also increased the cell density. Applying mold temperature control alone with temperature in the range of 90–120°C (near T_g), the surface roughness improved by 65%. Increasing mold temperature decreased the skin thickness; however, the cell size distribution became significantly nonuniform. It was found that thin skin, small and uniform cell size as well as good surface quality can be achieved efficiently by simultaneous combining of GCP and mold temperature control. The proposed innovative approach may lead to a significant improvement and a more broad application for MuCell process. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

注塑冷却分析BEM模型中积分项的计算

注塑冷却分析最终归结为求解模具表面温度场BEM方程组,方程组中存在大量的积分项,这些积分项很难用解析式表示,因此无法求得它们的精确解析解,多采用高斯数值积分获得近似数值解,计算精度较低。本文采用近似解析解和半解析解代替原来的数值解,使得关键部位积分计算的精度提高了10％以上,不仅有利于提高冷却分析的精度,也有效地改善了边界元方程组的性态。     

3D study on the effect of process parameters on the cooling of polymer by injection molding

Plastic injection molding (PIM) is well known as a manufacturing process to produce products with various shapes and complex geometry at low cost. Determining optimal settings of process parameters critically influence productivity, quality, and cost of production in the PIM industry. To study the effect of the process parameters on the cooling of the polymer during injection molding, a full three‐dimensional time‐dependent injection molding analysis was carried out. The studied configuration consists of a mold having cuboids‐shaped cavity with two different thicknesses and six cooling channels. A numerical model by finite volume was used for the solution of the physical model. A validation of the numerical model was presented. The effect of different process parameters (inlet coolant temperature, inlet coolant flow rate, injection temperature, and filling time) on the cooling process was considered. The results indicate that the filling time has a great effect on the solidification of the product during the filling stage. They also show that low coolant flow rate increases the heterogeneity of the temperature distribution through the product. The process parameter realizing minimum cooling time not necessary achieves optimum product quality and the complete filling of the cavity by the polymer material. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

微孔注塑制品表面质量改善和翘曲降低的技术

为拓宽微孔注塑制品的应用范围,需要改善其表面质量,降低其翘曲变形。模腔气体反压技术、模腔被动控温技术、微孔共注塑技术、泡孔成核速率控制技术、微孔注射压缩成型技术和快速热循环微孔注塑技术等可有效改善微孔注塑制品的表面质量。模腔气体反压技术、微孔共注塑技术和调整加工参数可进一步降低微孔注塑制品的收缩率和翘曲,提高制品的尺寸精度。本文较系统介的绍了这些技术和方法。     

微注射成型工艺的实验研究

设计了微注射模具的变温系统,加工了通道宽度分别为500μm和100μm的哑铃形微型腔。在此基础上,基于Taguchi实验设计方法进行了成型工艺实验。结合微尺度下熔体充模流动理论及微尺度效应,研究了工艺参数及其交互作用对微结构塑件成型质量的影响规律。实验结果表明,随着微结构塑件特征尺寸的减小,注射压力和模具温度对填充率的影响明显增强;熔体温度对填充率的影响程度有所增加;注射行程对填充率的影响程度有所降低;保压压力和保压时间对填充率的影响相对不明显。     

智能热水壶主体复杂抽芯及随形水路注塑模设计

根据智能热水壶主体结构特点和技术要求设计了一副复杂侧向抽芯及随形水路注塑模具。模具采用顺序侧向抽芯及延时侧向抽芯机构,有效改善了包紧力大、脱模困难塑件的注塑模具结构。定模型芯和动模型芯采用3D打印随形水路,有效改善了熔体热量多、成型零件温差大、温度高注塑模具的温度控制系统。模具采用了多项先进的创新技术,成型零件温差降低了50 %,注射成型周期缩短了约18 %,塑件变形量减小了75 %,尺寸精度提高了2级,达到了MT3（GB/T 14486—2008）。试模一次成功,成型塑件的外观质量和尺寸精度均达到了设计要求。     

Morphology and mechanical investigation of microcellular injection molded carbon fiber reinforced polypropylene composite foams

Employing microcellular injection molding technology, carbon fiber (CF)/polypropylene (PP) composite foams have been prepared. The influences of injection molding conditions and CF amounts relating to the flexural and impact performances have also been studied. X-ray computed tomography scanning has been used for morphological observation. For the flexural specimens, although the solid skin and foamed core layers can be confirmed significantly, the intermediate layer is indistinct. Moreover, the stretched cells can be confirmed dramatically for the Charpy impact specimens. The cell density increases to 12.0 × 10³ cell/cm² when the nitrogen content is 1%. By contrast, the cell densities decrease with the injection speed and CF content increasing accordingly. Further, the maximum specific flexural modulus and Charpy impact strength of the foams can achieve 14 GPa/(g/cm³) and 6.2 kJ/m², respectively, at the CF content of 30 wt%. Finally, the microcellular structure with the highest cell density can be confirmed with the nitrogen content of 1 wt%, the injection speed of 50 mm/s and the CF content of 10 wt%. Obviously, the CF contents have shown strong influences on the mechanical behaviors of the CF/PP composite foams compared with nitrogen contents or injection speeds.     

纵论注射成型技术

以注射成型技术在橡胶行业的发展现状为依据,从工作原理、生产工艺、产品质量、生产效率等几个方面着手,对模压成型技术和注射成型技术进行了比较,阐述了注射成型技术的优越性。同时,针对推广注射成型技术遇到的困难,提出了注射成型技术在橡胶行业的推广过程中所需要解决的一系列问题。     

注塑机肘杆合模机构弹性力学性能的探讨（四）

从注塑机肘杆合模机构弹性变形的运行特征进行分析研究,介绍了作者对弹性力学在注塑机肘杆合模机构中研究应用的一些成果。研究了拉杆和肘杆两者之间抗拉刚度的关系,提出了拉杆及肘杆根据拉伸刚度的设计方法及准则;研究了推力座导杆、销轴、模板支架、模板等抗弯挠度的特征及其相互之间的联系,提出了有关零件抗弯挠度的设计方法及准则;研究了有关零件的挠度和强度之间的内在联系,提出了根据挠度要求进行强度设计的准则。     

A physical model for a quality control concept in injection molding

In this work, a model is presented, which is the basis of a quality control concept for the injection molding process. Contrary to statistical methods, this model uses physical dependencies of two quality parameters on four influencing parameters. The influences of holding pressure, holding time, melt temperature, and mold temperature on part mass and dimensions are described based on the fundamental material behavior such as pvT‐data or energy equation. Furthermore, the influence of viscosity changes is indirectly taken into account using the injection work. Assuming only small deviations of the influencing parameters around an optimized operating point, the four parameters are treated as being independent from each other. With this assumption, a product ansatz was chosen with different functions for each influencing factor. Applying basic algebra, the starting equation was transformed into a form that describes either the change in part mass or characteristic part dimensions as a function of the influencing factors. The final equation for the part mass contains six model parameters, whereas nine model parameters are necessary for the equation for the part length. To obtain those model parameters some systematic experiments are required. Once the parameters are known, the model is able to calculate the change of the target values when the influencing factors vary around the operating point. The model was tested experimentally with focus on dimensions using a plastic cover made of an acrylonitrile butadiene styrene (ABS) grade. For the investigated part geometry and material grade, the process behavior was described well by the model. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Presentation of a novel sensor based on acoustic emission in injection molding

Injection molding is the most important process to produce plastic parts. Because of increasing complexity of the plastic parts and the aim to reach zero‐defect production it is a must to control the dynamic injection molding process. Therefore information from the inside of the mold, measured with sensors, is necessary. State of the art is to implement wired mold cavity pressure sensors as well as wired cavity temperature sensors. This article presents a novel wireless measurement setup which uses structure borne sound as transport medium. The sound is generated by an acoustic actor which is activated by the passing flow front at certain predetermined positions in the cavity (or cavities). Beside the mechanical setup of the sensor proof of concept measurements with a prototype setup are shown in this article. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

滑块驱动双色注塑模结构设计

本文重点介绍了通过滑块机构驱动完成两次注塑成型的双色注塑模。为双色注塑模向大型化发展做了一次有益的探索,对双色注塑模具设计、生产和使用和推广具有一定的借鉴价值。     

纤维增强塑料注射充模过程中纤维对模具的冲蚀磨损模拟

针对塑料模具在玻璃纤维冲蚀下造成的表面磨损问题,运用有限元软件ANSYS/LS-DYNA建立了模具材料多颗粒冲蚀有限元模型,进行三维显式冲击动力学计算,研究纤维在不同冲蚀速度和冲蚀角度下对模具的冲蚀规律,分析冲蚀机理。结果表明,玻璃纤维对模具的冲蚀过程以微切削为主;玻璃纤维对模具的冲蚀磨损率随着冲蚀速度的增加而增加,随着冲蚀角度的增加而呈现先增加后减小的趋势。     

A novel method for improving the surface quality of microcellular injection molded parts

Microcellular injection molding is the manufacturing method used for producing foamed plastic parts. Microcellular injection molding has many advantages including material, energy, and cost savings as well as enhanced dimensional stability. In spite of these advantages, this technique has been limited by its propensity to create parts with surface defects such as a rough surface or gas flow marks. Methods for improving the surface quality of microcellular plastic parts have been investigated by several researchers. This paper describes a novel method for achieving swirl-free foamed plastic parts using the microcellular injection molding process. By controlling the cell nucleation rate of the polymer/gas solution through material formulation and gas concentration, microcellular injection molded parts free of surface defects were achieved. This paper presents the theoretical background of this approach as well as the experimental results in terms of surface roughness and profile, microstructures, mechanical properties, and dimensional stability.     

Experimental investigation of infrared rapid surface heating for injection molding

A low cost and practical infrared rapid surface heating system for injection molding is designed and investigated. The system was designed to assemble on the mold and a control system was used to operate the motion of the lamp holder. Four infrared halogen lamps (1 kW each) were used as the radiative source to heat the surface of mold insert. The temperature increase is verified on the mold plate with a thermal video system. Two types of specular reflectors combined with different bulb configurations were applied to study the heating ability of radiation heating. A modified spiral flow mold was used to test the enhancing filling ability of the rapid surface heating system. Three resins, PP, PMMA and PC were molded in the spiral flow injection molding experiments. If spherical reflector and centralized lamp configuration are used, the temperature at the center of the mold surface is the highest. The temperature of mold center surface is raised from 83°C to 188°C with 15 s of infrared heating. Because the surface temperature of the mold insert is higher than the glass transition temperature of resins before filling, the flow distance of resins in the modified spiral flow mold will be increased. The location effect of the infrared surface heating system on a thin‐long cavity was studied to demonstrate the possibility of using smaller infrared heating area on a large mold surface. A microprobe cavity also demonstrated that with the assistance of infrared heating technology the formability of a microprobe can be greatly improved. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3704–3713, 2006     

注塑机筒外径设计的分析研究

探讨了影响注射机筒外径设计的主要因素,评述了几种具有代表性的注塑机筒疲劳强度理论设计准则,分析了其局限性和可用范围,提出了符合实际的注塑机筒的疲劳强度设计外径的准则,提出了根据加热功率配置的表面积设计外径的准则,提出了根据综合因素确定机筒外径的原则。