吨包装内胆挤出吹塑成型型坯吹胀的数值模拟

针对吨包装内胆挤出吹塑型坯吹胀阶段的成型工艺,采用Workbench-Polyflow分析软件实现型坯吹胀模拟。建立型坯及模具的几何模型和网格模型;利用Polyflow中的参数渐进方法建立型坯吹胀阶段中的模具闭合运动模型。获得型坯在吹胀过程中的型坯轮廓曲线分布以及吹胀完毕后的型坯壁厚分布;分析了模具运动速度和吹胀压力对型坯与模具的接触时间、吹胀时间及壁厚的影响。     

医用床头板挤出吹塑成型工艺参数优化

为改善复杂非轴对称挤出吹塑制品的壁厚均匀性,以医用床头板为例,基于Polyflow软件模拟了医用床头板的非等温吹胀过程,并用目标函数评估最终制品的壁厚均匀性。根据正交实验分析了吹胀压力、吹胀时间、型坯初始温度及型坯初始壁厚4个成型工艺参数对制品壁厚均匀性的影响,得到最佳工艺参数组合为A3B3C1D1,即吹胀压力0. 7 MPa、吹胀时间5 s、型坯初始温度180℃、型坯初始壁厚3 mm,最后对最佳工艺参数组合进行了模拟验证。结果表明,优化后的工艺参数可使最终医用床头板的壁厚更加均匀,为在实际生产过程中复杂非轴对称挤吹制品的成型工艺参数改进提供有效指导,提高生产效率。     

PET注拉吹制品壁厚分布的研究

通过注射拉伸吹塑实验分析了二次吹胀压力、拉伸杆速度以及吹胀延迟时间对瓶子轴向壁厚分布的影响。实验结果表明：吹胀压力的改变对瓶子轴向壁厚分布影响不大，拉伸杆速度与吹胀延迟时间的变化对瓶子轴向壁厚分布有显著影响。吹胀延迟时间的改变会形成不同的型坯轮廓发展模式，在注拉吹可视化实验结果的基础上，结合应力和温度场两方面的因素解释了型坯轮廓发展模式的成因。     

挤出吹塑中型坯自由吹胀的动力学分析

聚合物挤出吹疗程 型坯的自由吹胀受到多方面因素的影响。采用动力学方法对此进行了研究。模拟了史胀过程听型坯轮廓变化， 吹胀压力，材料模量，型坯初始壁厚对此过程的影响。     

太阳能热水系统中水箱内胆保温结构的性能优化研究

以太阳能内胆为研究对象,通过Ansys Workbench软件对其吹塑成型过程进行模拟仿真,对制件的壁厚分布进行研究。通过建立响应面模型,以吹胀压力、型坯初始温度以及型坯初始壁厚为设计变量,以制件最终的壁厚均匀性函数值为响应目标,获得较佳的成型工艺参数组合。结果表明:当吹胀压力0.461 MPa,型坯初始温度213.169℃,型坯初始壁厚0.003 m,该成型工艺条件下制件的成型质量最好,壁厚均匀性函数值最小值为0.384×10~(-5)mm~2,较未优化前降低了0.024×10~(-5)mm~2,相对偏差为3.13%。通过响应面法能够有效地改善太阳能水箱内胆的保温性能。     

基于DOE设计与MOPSO算法的PVC建筑排水管多目标优化分析

以建筑排水管为研究对象,采用DOE设计中的最优拉丁超立方抽样法随机均匀的抽取样本,以吹胀压力、吹胀时间、型坯初始温度以及型坯初始壁厚为设计变量,以壁厚均匀性函数值为响应目标,建立代理模型以替代CAE的模拟仿真。利用多目标粒子群优化算法(MOPSO)对代理模型进行内部寻优,从而获得较为理想的成型工艺参数。结果表明:吹胀压力0.6 MPa、吹胀时间3 s、型坯初始温度169.09℃以及型坯初始壁厚2 mm时制件成型质量较为理想。该工艺条件下,壁厚均匀性函数值实际模拟值为0.320 18×10~(-5) mm~2,预测值为0.319 9×10~(-5) mm~2,两者相对偏差为0.087%,小于5%。     

基于Polyflow仿真和Isight汽车油箱多目标工艺优化研究

为减小吹塑制件壁厚不均导致的翘曲问题,采用Polyflow软件对汽车油箱吹塑成型过程进行了模拟仿真,但是由于软件仿真计算过程极为缓慢,因此通过Isight软件首先对制件采用最优拉丁超立方抽样法随机采样,随后建立Kriging代理模型,减少软件仿真模拟时间,提高计算效率,并且通过模拟退火算法对代理模型进行全局寻优,对制件吹胀压力、吹胀时间、初始型坯温度以及初始型坯壁厚进行了多目标优化,以最终壁厚均匀性函数值为响应目标,从而获得一组最佳的工艺参数组合。结果表明:代理模型R2为0.977 75,预测值与模拟值基本一致,模拟退火算法优化后最佳的成型工艺参数吹胀压力为0.304 MPa,吹胀时间为3.008 s,型坯初始温度为199.020oC,型坯初始壁厚为4.998 mm。为改善制件翘曲提供了一定的参考。     

塑料挤出吹塑的机理问题

采用不同的方法对挤出吹塑过程的型坯成型、型坯吹胀与制品冷却三阶段的机理问题进行了研究.采用人工神经网络方法预测了受模口温度和挤出流率影响的型坯成型阶段的膨胀.利用建立起来的神经网络模型预示的膨胀与实验结果很吻合,且可在一定范围内,预示不同工艺条件下型坯的直径膨胀和壁厚膨胀,为型坯的直径和壁厚的在线控制提供了理论依据.基于薄膜近似和neo-Hookean本构关系,建立了描述型坯自由吹胀的数学模型,并通过实验方法获得了型坯吹胀的瞬态图象.     

挤出吹塑成型初始型坯温度的数值模拟优化

为改善挤出吹塑过程中制件壁厚不均现象,在型坯壁厚非均匀优化方法的基础上,使用计算流体力学软件Polyflow数值模拟了HDPE油桶的非等温吹胀,并利用初始型坯温度优化程序,通过改变初始型坯局部温度来控制吹胀制品的壁厚。结果表明,使用初始型坯温度优化程序对非均匀初始壁厚型坯进行5次优化后,吹塑制品的壁厚均趋近于目标壁厚值0.003 m,且达到壁厚平均函数最小值3.6×10~(-6)m~2。     

基于响应面法PE吹塑用汽油瓶工艺参数优化分析

为改善塑料制件壁厚不均造成的产品成型质量问题,以PE汽油瓶为研究对象,通过Polyflow软件模拟了其吹塑过程,研究了吹胀压力、型坯初始温度以及型坯初始壁厚对汽油瓶制件壁厚均匀性的影响,并且以最终制件壁厚均匀性为评判标准,建立二次多项式响应面模型,将响应面模型与有限元法相结合来优化汽油瓶吹塑成型工艺参数。实验表明:优化后的工艺参数吹胀压力为0.29 MPa,型坯初始温度为189℃,型坯初始壁厚为0.004 m时,该条件下制品壁厚均匀性较好,通过该法可以为后续吹塑制品成型提供一定的理论指导。     

Integrated numerical modeling of the blow molding process

The numerical modeling of the extrusion blow molding of a fuel tank is considered in this work. The integrated process phases are consecutively simulated, namely, parison formation, clamping, and inflation, as well as part solidification, part deformation (warpage), and the buildup of residual stresses. The parison formation is modeled with an integral type viscoelastic constitutive equation for the sag behavior and a semi-empirical equation for the swell behavior. A nonisothermal viscoelastic formulation is employed for the clamping and inflation simulation, since parison cooling during extrusion strongly affects the inflation behavior. Once the parison is inflated, it solidifies while in the mold and after part ejection. Warpage and residual stress development of the part are modeled with a linear viscoelastic solid model. Numerical predictions are compared with experimental results obtained on an industrial scale blow molding machine. Good agreement is observed. A process optimization based on a desired objective function, such as uniform part thickness distribution and/or minimal part weight, is performed. The integrated clamping, inflation, and cooling stages of the process are considered. The optimization is done by the systematic manipulation of the parison thickness distribution. Iterations are performed employing a gradient based updating scheme for the parison thickness programming, until the desired objective of uniform part thickness is obtained.     

Measurement and calculation of parison dimensions and bottle thickness distribution during blow molding

Experimental data are reported regarding the dynamics of the blow molding process, including parison formation, growth, and inflation. These data have been obtained with the aid of high speed cinematography and pinch mold experiments, in conjunction with two commercial blow molding polyethylene resins. It is shown that pinch mold experiments alone do not yield accurate data regarding thickness and diameter swell. Furthermore, the inflation process involves decreasing rates of inflation with time, as a result of the rise in viscosity due to the cooling of the parison during inflation. Mathematical procedures are proposed for a first-order estimation of parison length and swell as a function of time and the inflation behavior after clamping. In the absence of more dependable basic procedures, the proposed treatment is employed to estimate the effective transient swell functions for the parison using experimental data obtained under the specified conditions. The mathematical treatment is extended to determine the thickness distribution of the bottle. Good agreement is obtained between experimental and calculated results.     

Experimental and theoretical investigation of the inflation of variable thickness parisons

In today's blow molding of complex parts, an optimal resin distribution is critical to a successful operation. These goals are mostly attained through a technique known as parison programming. The process involves varying the die gap during extrusion and therefore results in a parison having a variable thickness along its length. The subsequent inflation of a variable thickness parison is a complex phenomenon involving the interaction of many process variables. The final thickness distribution and inflation patterns were obtained for various programmed parisons. Constant, one step, two step, and sinusoidal thickness parisons were studied. The inflation patterns were monitored by employing a transparent mold in conjunction with a video camera. The experimental data indicated the presence of an oscillatory inflation pattern for some of the variable thickness parisons. The experimental final part thickness distribution for these cases was highly nonlinear. Theoretical predictions of the final thickness distribution were also obtained for some of the cases. The simulation is based on the inflation of a Mooney-Rivlin hyperelastic material. A wide range of deformation is accounted for by introducing an evolutionary Mooney constant, dependent on the level of deformation.     

Confined parison inflation behavior of a high-density polyethylene

An analysis of the confined parison inflation step associated with the extrusion blowmolding of a high-density polyethylene is presented. Based upon simple geometrical considerations and material conservation principles, relationships describing the wall thickness variation have been obtained for various mold configurations. The experimentally measured part thickness distribution is found to be in good qualitative agreement and reasonable quantitative correspondence with the theoretical predictions. Furthermore, the expressions for the thickness variation have been utilized in order to estimate the confined inflation time for the case of a power-law constitutive equation. In addition, a brief discussion of some practical mold design considerations is given based upon the theoretical analysis.     

New Strategies for Predicting Parison Dimensions in Extrusion Blow Molding

In this work, two new strategies were proposed for predicting the parison thickness and diameter distributions in extrusion blow molding. The first one was a finite-element-based numerical simulation for the parison extruded from a varying die gap. The comparison of simulated and experimental parison thickness distributions indicates that the new method has certain accuracy in predicting the parison thickness from a varying die gap. The second one was an artificial neural network (ANN) approach, the characteristics of which are in sufficient patterns that can be obtained without doing too many experiments. The diameter and thickness swells of the parisons extruded under different flow rates were obtained by a well-designed experiment. The obtained data were then used to train and test the ANN model. The dimension of one location on the parison can provide one pattern to train the ANN model. Trained and tested ANN model can be used to predict the dimensions at any location on the parison within a given range. The proposed two strategies can help search the processing conditions to obtain optimal parison thickness distributions.     

The dynamics of parison free inflation in extrusion blow molding

Parison free inflation behavior, associated with the extrusion blow molding process, is considered both experimentally and theoretically. Experimental observations indicate1 that the parison assumes a rather complex shape under conditions of unrestricted inflation. In particular, the time-dependent shape is markedly ellipsoidal rather than cylindrical in nature. This nonuniform behavior, however, becomes more prominent in relation to the entire length as the parison-length-to-diameter ratio is decreased. Based on the experimental observations, a simplified analytical treatment of the free inflation of a viscoelastic parison is presented. The theoretical results illuminate the influence of material properties and process conditions on the inflation process. Expectedly, inflation is enhanced by an increase in the pressure driving force as well as by a decrease in viscosity. However, melt elasticity is also found to exert a significant influence on the inflation behavior. Moreover, the theoretical analysis suggests that the initial parison dimensions play a central role in controlling the inflation process.     

Overall numerical simulation of extrusion blow molding process

This paper focuses on the overall numerical simulation of the parison formation and inflation process of extrusion blow molding. The competing effects due to swell and drawdown in the parison formation process were analyzed by a Lagrangian Eulerian (LE) finite element method (FEM) using an automatic remeshing technique. The parison extruded through an annular die was modeled as an axisymmetric unsteady nonisothermal flow with free surfaces and its viscoelastic properties were described by a K‐BKZ integral constitutive equation. An unsteady die‐swell simulation was performed to predict the time course of the extrudate parison shape under the influence of gravity and the parison controller. In addition, an unsteady large deformation analysis of the parison inflation process was also carried out using a three‐dimensional membrane FEM for viscoelastic material. The inflation sequence for the parison molded into a complex‐shaped mold cavity was analyzed. The numerical results were verified using experimental data from each of the sub‐processes. The greatest advantage of the overall simulation is that the variation in the parison dimension caused by the swell and drawdown effect can be incorporated into the inflation analysis, and consequently, the accuracy of the numerical prediction can be enhanced. The overall simulation technique provides a rational means to assist the mold design and the determination of the optimal process conditions.     

Optical on-line measurement of the thickness distribution of blow molding parisons

An optical sensor has been developed which can measure the thickness profile of the parison on line just prior to its enclosure in the mold. The device determines thickness by striking the parison at an angle with a laser beam and measuring the separation between the beams that are reflected from the outer and inner surfaces of the parison wall. A prototype was built and tested. The prototype uses three lasers at different angles and can make up to 250 point measurements during a one second scan. A personal computer uses specially developed software to reconstruct the profile of the parison wall from the raw data with an accuracy of ±5%.     

型坯温差法优化挤出吹塑中空工业制件壁厚分布的研究

以典型复杂中空工业制件为研究对象,根据聚合物流变学原理,提出了用型坯温差法来优化挤出吹塑中空工业制件壁厚分布的均匀性：在型坯挤出或型坯吹胀之前,采用水或者空气强制冷却变形较大部位对应的型坯,使局部温度迅速降低,使型坯具有一定的温度梯度。结果表明,用型坯温差法优化后的吹塑成型油箱壁厚分布标准差由0.7249减小为0.4475、0.4582,壁厚均匀性明显得到改善,验证了利用型坯温差法优化油箱制件壁厚分布均匀性的方法是可行的。