温度对挤出吹塑制件壁厚分布及性能的影响

为实现挤出吹塑制件壁厚均匀分布和提高制件性能,国内外学者从挤出吹塑过程的3个阶段:型坯成型、型坯吹胀以及制品冷却与固化阶段,研究了温度对制件壁厚分布及其性能的影响情况.分析了温度对其成形及性能的影响,综述了前人研究成果.     

改善挤出吹塑制件壁厚均匀性的几种方法

概述了近年来改善挤出吹塑中空制件壁厚不均匀的方法及其进展,包括新牌号的树脂,新的型胚壁厚控制技术及新的挤出吹塑成形工艺。型胚控制技术主要介绍了异型口模和可调机头;新成形工艺包括3D中空吹塑,真空吸塑与挤出吹塑相结合的技术,型坯温差法及高压低温挤出吹塑技术。     

IBC 内胆型坯初始尺寸预测与试验

目的鉴于壁厚控制的复杂性,建立基于有限元型坯尺寸的预测方法。方法采用WorkbenchPOLYFLOW分析软件模拟型坯吹胀的过程,获得均匀的型坯尺寸吹胀成型的IBC内胆壁厚分布;分析型坯初始尺寸对制件最终壁厚分布的影响;确定制件壁厚的薄弱部位及其相对应的型坯位置;调整型坯轴线方向控制点的初始尺寸,获得改善制件最终壁厚的型坯轴线方向的初始壁厚曲线。结果该曲线仿真壁厚极差为2.27 mm,通过大型中空成型机试生产,确定了型坯初始壁厚实验曲线,验证了预测型坯曲线的正确性。结论该尺寸预测方法缩短了生产周期,准确性高,具有较好的实际应用价值。     

局部抽真空对优化挤出吹塑中空工业制件壁厚均匀性的研究

从挤出吹塑中空工业制件壁厚不均匀原因分析出发,提出挤出吹塑成型中局部抽真空的方法,建立了抽真空系统。然后,通过挤出吹塑成型中局部抽真空工艺优化制件壁厚,使制件壁厚的方差由0.4739减小到0.1303,制件壁厚均匀性大大提高,为中空工业制件的壁厚优化提供了一种有效方法。     

型坯壁厚多点控制系统通过鉴定

新一代计算机实时监控,能确保各种产品灌装塑料瓶(桶)表面质量、降低材耗的型坯壁厚多点控制技术,已由上海市轻工机械技术研究所试制成功并通过鉴定,目前已配套应用于上海市塑料制品三厂SC—50/90塑料吹塑成型机上,性能稳定,工作可靠,塑料制品的中空壁厚控制效果特别显著。     

中空成型容器壁厚均匀性探讨

随着塑料工业的技术迅猛发展,中空容器以其优异的耐化学性、良好物理特征等优点,被化妆品企业广泛应用。同时,随着计算机技术的快速发展,吹塑瓶的成型设备也由前几年单料双模挤出机械发展到目前由电脑76点控制坯管壁厚、双料双模的成型机械设备,使中空容器整体质量有了显著的发展。然而由于容器造型的多样化,使得中空容器在成型过程中对容器壁厚控制,尤其是异型容器壁厚的控制突现成为较难的课题。特别是在提倡环保和节约资源的今天是一个应当重视的课题。     

Y型三通管内高压成形机理及补料比的影响研究

由于Y型三通管结构不对称,内高压成形过程中左右冲头的轴向补料比对成形有较大的影响。利用数值模拟,基于Dynaform软件平台,建立了Y型三通管弹塑性模型,并利用该模型研究了镁合金Y型三通管热态内高压成形过程、塑性变形规律、失稳行为、各种成形缺陷以及补料比对成形的影响。结果表明:成形后零件左侧圆角过渡区壁厚最大,支管顶部壁厚最薄;随着补料比的增加,支管高度也随之增加,并在一定程度上能改善支管的壁厚减薄,但过度加大补料比会使支管顶部减薄严重。     

Y型三通管内高压成形壁厚分布规律

为了解Y型三通管内高压成形时的壁厚分布及成形压力对壁厚的影响规律,通过数值模拟和实验对Y型三通管的内高压成形过程进行了研究,分析了3个不同成形阶段零件的壁厚分布规律和成形过程中零件典型点壁厚随内压的变化规律.研究表明,成形后零件左侧过渡区圆角处壁厚最大,右侧过渡区圆角处次之,枝管顶部壁厚最薄.利用数值模拟,研究了不同终成形压力对零件壁厚分布的影响,研究发现随着终成形压力的提高,零件的最大增厚率变化不明显,但零件的最大减薄率有显著的增加.     

带横向内筋张紧轮旋压成形分析

目的解决某型号带横向内筋张紧轮旋压成形困难的问题。方法运用有限元模拟软件,建立了张紧轮的有限元模型,选取了不同的坯料壁厚和旋轮圆角半径,对张紧轮旋压成形过程进行了数值模拟。结果获得了旋压成形过程中坯料壁厚大小和旋轮圆角半径大小对旋压力和成形质量的影响,并对结果进行了总结。结论通过分析壁厚和预成形轮形状对张紧轮旋压成形质量的影响,得出了最优的工艺参数值,对实际生产具有指导意义。     

支管直径大小对 T 型三通管充液成形的影响

目的研究支管直径大小对T型三通管在充液成形过程中的影响。方法在Dynaform软件中建立了有限元模型,对T型三通管的成形过程进行了数值模拟,并进行了相关实验对比。结果随着支管直径的减小,主管端部的壁厚增大,主管壁厚最厚处逐渐从主管背部转移到主管侧壁处,支管直径越小,壁厚最厚处位置越靠上。支管直径较小的T型三通管的壁厚分布更加不均匀,壁厚变化更为剧烈。充液成形第一阶段的轴向补料量对于T型三通管成形的影响较大,支管直径较大的T型三通管补料量增大有助于减小减薄率;支管直径较小的T型三通管补料量增大,减薄率减小不明显,反而会大幅增加增厚率。结论 T型三通管的支管直径越小,其充液成形的难度越大,起皱和破裂的风险越大。支管直径越大,应增加第一阶段的补料量,支管直径越小,在满足减薄率的条件下需减少补料量。     

Modeling of Industrial Polymer Processes: Injection Molding and Blow Molding

In the last twenty years injection molding and blow molding have seen a rapid growth due to the development of new application areas in the automotive, sports and leisure, electronics, transportation and packaging industries. This success can be traced to the optimization of existing processes and to the development of new processing techniques employing novel concepts such as gas-assisted injection molding, co-injection, and 3D and sequential blow molding. The complexity of these new molding techniques calls for a much better understanding of the material behavior during the basic stages of the process and its relation to the properties and performance of the final part. These characteristics are directly dependent upon die and mold designs and on the operating conditions during extrusion, injection, inflation and cooling in the mold.In this paper we will demonstrate how the numerical simulation of the individual steps of the process can be used to optimize the process and product performance of industrial parts. In the case of injection molding, special interest will be devoted to the numerical prediction of the filling phase for both thin and thick parts. For blow molding the prediction of material behavior during clamping and inflation will be shown and related to final part thickness distribution, parison programming and preform design.     

面向壁厚均匀性的拉深成形TRB板形设计及神经网络预测模型

目的 研究连续变截面板拉深成形过程中圆筒件的壁厚均匀性问题。方法 基于正交试验设计和极差分析方法,研究连续变截面板结构参数对圆筒件拉深成形壁厚均匀性的影响,并结合SSA–BP神经网络预测并验证连续变截面板成形的壁厚均匀性。结果 通过正交试验及极差分析,得到连续变截面板各结构参数按对最大壁厚影响由大到小的顺序依次为薄区厚度>厚区厚度>左侧过渡区长度>右侧过渡区长度;按对最小壁厚影响由大到小的顺序依次为薄区厚度>厚区厚度>右侧过渡区长度>左侧过渡区长度;按对最大壁厚差影响由大到小的顺序依次为薄区厚度>左侧过渡区长度>厚区厚度>右侧过渡区长度。综合考虑最大壁厚、最小壁厚及最大壁厚差,得到最优参数组合如下:厚区厚度为1.1 mm,薄区厚度为0.8 mm,左侧过渡区长度为2.5 mm,右侧过渡区长度为29.5 mm。基于正交试验分析结果建立的SSA–BP神经网络模型具有良好的预测能力,正交试验外5组数据的预测值与真实仿真值的最大误差均在11%以下。结论 基于正交试验分析结果建立的SSA–BP神经网络模型能够实现对TRB板圆筒件拉深成形壁厚的准...     

带壁厚偏差管坯液压胀形加载路径的研究

建立了带壁厚偏差管坯液压胀形的力学模型,揭示了不同轴向应力状态下壁厚偏差对管坯成形的影响规律,给出了带壁厚偏差管坯液压胀形加载路径设计的标准.针对某重型卡车桥壳预成形管坯的液压胀形工艺,进行了3种不同壁厚偏差管坯在不同典型加载路径下的有限元模拟,结果表明:内压升高至最大保持恒定,管坯薄壁侧均在合模前发生开裂且薄壁侧与厚...     

The Internal Pressure Test in Experiment and Simulation—Influence of the Wall Thickness Variation and the Change of the Packaging Behavior after the Impact of Standard Liquids

The effect of the wall thickness variation of blow‐moulded bodies made of high‐density polyethylene on an internal pressure test after prestoring the packaging with standard liquids was evaluated in experiments and simulations. The objects of the investigation were jerrycans used for the transportation and storage of dangerous goods. The wall thickness was determined using two alternative methods to the magnetostatic measurement. These alternative methods are used for research purpose to get a volumetric model of the jerrycan wall as a geometric model for the simulation. The comparison of the experiments and the simulations of the internal pressure test were performed using the digital image correlation method. The integral strain and deformation of the whole jerrycan was detected by measuring the total mass of the jerrycan being filled with water during the internal pressure test. This is a suitable alternative to the optical measurements of local deformation by the digital image correlation method. Prestorage at 40 °C without the influence of chemicals strengthens the jerrycan, whereas the swelling effect of butyl acetate and hydrocarbon mixture softens the jerrycan. The comparison with the experiment is necessary to verify the accuracy of the simulation. It shows that the deformation can be simulated more precisely by using the actual measured geometry. The weakening of the high‐density polyethylene caused by a hydrocarbon mixture can be simulated using the Arrhenius equation. The aim of the simulation was to discover whether it is possible to use specimens to predict the behaviour of a packaging both after the influence of standard liquids. Copyright © 2012 John Wiley & Sons, Ltd.     

5A06 铝合金板材超塑气胀成形数值模拟

目的改善5A06铝合金板材超塑性气胀成形件壁厚分布。方法采用MARC有限元分析方法,对商业供货态5A06-O铝合金板材(原始厚度为2 mm)的超塑性成形进行数值模拟分析。结果优化后的反吹预减薄变形,使杯形件最终壁厚分布大大改善,最薄处壁厚从单纯正吹胀形时的0.65 mm提高到了0.94 mm,壁厚均匀性指数达到0.079。结论合理的反胀形模具可以增加最小壁厚,达到提高壁厚均匀性的目的。     

正方形自填充蜂窝结构异面平台应力的研究

目的 为了促进正方形自填充蜂窝的合理使用，研究其异面平台应力随冲击速度、壁厚边长比和自填充级数的变化规律。方法 利用ANSYS/LS-DYNA建立基于胞元阵列的正方形自填充蜂窝异面冲击分析的有限元模型。对自填充级数为0的正方形蜂窝进行异面压缩试验和相应的仿真分析，证明有限元模型的可靠性。基于简化的超折叠单元理论，建立蜂窝准静态平台应力的理论模型，并证明理论模型的可靠性。结果 正方形自填充蜂窝在大的壁厚边长比和冲击速度下拥有更高的动态平台应力;在自填充级数由0变为1时，动态平台应力增长率最大。结论 在其他因素不变的情况下，正方形自填充蜂窝的异面动态平台应力与冲击速度的平方呈线性关系，与壁厚边长比呈幂指函数关系，其增长率随自填充级数逐级递减。基于数值模拟结果，得到了不同自填充级数下正方形自填充蜂窝异面动态平台应力的经验公式。     

Optical measurement and modelling of parison sag and swell in blow moulding

Blow moulding is a process whereby a cylindrical parison is extruded first, then pinched between the two halves of a mould and, finally, blown into the product. Parison size and shape result from complex interactions between mandrel and die geometries, processing parameters and viscoelastic properties of the polymeric material. Moreover, parison size changes with time due to sag. An innovative, contactless and online measurement technique of the parison is shown to be an effective tool to measure precisely parison diameter and thickness and to capture dimensional changes with time. This technique employs laser lighting of the parison and hinges on the refractive properties of molten polymer. Images taken with a digital camera are processed to give a precise measurement of diameter and thickness, at different time step during extrusion. Thus, parison swell and sag have been recorded for a commercial HDPE. Influence of processing parameters such as the rotational screw speed or die gap width can be brought forward. From the measurements, thickness swell is found to possess a different behaviour from diameter swell. Moreover, sag has been measured and can be modelled from a Newtonian perspective using one dimensional convected coordinates. Parison sag is shown to be governed by two parameters: an extrusion velocity and a a single coefficient of sagging susceptibility which value has been deduced from experiments.