工艺参数对动态注塑成型制品品质的影响

采用聚丙烯(PP)材料,应用Taguchi DOE技术进行振动注塑成型正交实验,研究了工艺参数对制品成型收缩率和制品质量的影响。利用各振动频率段的较优参数组合,比较了振动条件下和稳态下的制品收缩率和制品质量。结果表明:制品的成型收缩率随着熔体温度的升高而降低,随着注射速率的增加而降低;制品质量随着熔体温度的升高而减小,随着注射速率的增大而增加;振动降低了制品成型收缩率,提高了制品质量。     

注塑成型工艺对显示器结构件力学性能的影响

以某显示器结构件为研究对象,注塑件在工作状态下的Mises应力值为评价指标,结合注塑成型数值仿真和结构分析数值仿真,采用正交设计、极差和方差分析方法,获得了最佳工艺参数组合。进行了单因素变动实验,研究了单工艺参数对注塑件力学性能的影响。结果表明:随熔体温度的升高、模具温度的降低、保压压力降低和保压时间的减少,该结构件在工作状态的Mises应力会增大。研究结果对提高注塑件的结构分析精度和指导注塑工艺参数的选取具有一定的参考价值。     

塑料制品注塑工艺参数的合理配置

介绍了塑料注塑工艺中影响制品质量的主要工艺参数及选用原则,并阐述了采用流动模拟技术对模具结构设计和工艺参数优化装置的指导作用。     

注塑制品残余应力测定方法

残余应力对制品的形状、表面质量及使用性能有重要影响，本文针对注塑制品，介绍了4种残余应力的测定方法、测定原理及计算方法，其中包括双折射法、剥层法、钻孔法、应力松驰法。评述了各种测试方法的优缺点。     

工艺参数对微注塑制品重量重复精度的影响

注塑制品的重量重复精度是衡量注塑制品质量精度的重要技术参数。通过Taguchi试验设计方法,研究了熔体温度、模具温度、保压压力、保压时间、峰值型腔压力对微注射成型制品重量的影响。实验结果表明,保压压力是影响制品重量最主要的工艺参数。无论样条受到拉伸还是冲击,其重量均会随着保压压力的增大而增加,保压时间对制品重量的影响较小。当拉伸样条峰值型腔压力为65 MPa,冲击样条峰值型腔压力为68 MPa时,随着峰值型腔压力增加,制品重量显著增加。当保压压力从85 MPa增加到100 MPa,拉伸样条的重量从0.544 g提高到0.559 g,增加了2.7%,冲击样条的重量从0.418 g提高到0.425 g,增加了1.7%。     

工艺参数对溢流法水辅注塑残余壁厚的影响

残余壁厚是影响短纤维增强复合材料水辅助注射成型塑件力学性能的重要指标,与工艺参数存在非线性关系。对溢流法水辅助注射成型进行了数值模拟,中心复合设计方法进行实验设计并获取了残余壁厚的样本数据,采用线性回归方法建立残余壁厚与工艺参数间的响应面多元二次代理模型,通过方差分析研究了残余壁厚对熔体温度、模具温度、延迟时间、注水压力及注水温度的敏感性,并分析参数交互作用对残余壁厚的影响。研究结果表明,注水压力、延迟时间及注水温度是影响残余壁厚的主要参数;随着注水压力的增大,残余壁厚值逐渐减小,但是,随着延迟时间的延长和注水温度的升高,残余壁厚值逐渐增大。     

工艺参数对微孔注塑PC制品泡孔形态的影响

采用正交试验法研究了微孔注塑成型工艺参数(熔体温度、模具温度、注射速度、超临界流体(SCF)比例、背压和预塑量)对制品不同截面泡孔密度、泡孔直径的影响。结果表明:影响泡孔尺寸和泡孔密度的主要因素是SCF比例和背压;优化后的工艺组合为熔体温度290℃、模具温度60℃、注射速度70 cm~3/s、SCF比例0.6%、背压15 MPa、预塑量29 cm~3。     

工艺条件对夹芯注射制品残余应力的影响

采用Moldflow公司MPI软件中的Co—injection分析模块，对ABS／PS夹芯注射成型过程进行动态模拟分析，以揭示工艺参数对夹芯注射成型过程中残余应力影响的规律。结果发现：在各种成型工艺参数中，保压条件对残余应力影响较为突出，模温条件对残余应力影响次之；最大残余应力主要分布在浇口位置和芯层最厚处，芯层前缘处残余应力次之，壳层最厚处残余应力最小。     

工艺条件对夹芯注射制品残余应力的影响

采用Moldflow公司MPI软件中的Co-injection分析模块，对ABS／PS夹芯注射成型过程进行动态模拟分析，以揭示工艺参数对夹芯注射成型过程中残余应力影响的规律。结果发现：在各种成型工艺参数中，保压条件对残余应力影响较为突出，模温条件对残余应力影响次之；最大残余应力主要分布在浇口位置和芯层最厚处，芯层前缘处残余应力次之，壳层最厚处残余应力最小。     

注塑件残余应力的分析研究

根据注射成型的工艺特点，分析了注塑制品残余应力的产生原因和影响因素。     

A study on the distinguishing responses of shrinkage and warpage to processing conditions in injection molding

A challenging task in injection molding industry is to minimize shrinkage and warpage (S&W) through optimal setting of molding conditions. In determining the relationship between molding conditions and product dimension, most existing literature considered S&W as a whole entity or focused on only one of them. The intention of this study was to distinguish these two terms, and perform a thorough analysis on the effect of operative conditions on S&W during injection molding process through a combination of experimental and numerical methods. Six process parameters with five levels were examined on a box-shaped product, and the single factor analysis of variance (ANOVA) was adopted in identifying the significance of each variable in the experiment. Results indicated that the effect of processing conditions on shrinkage is different from that on warpage. Specifically, packing pressure affects shrinkage most while packing time is the dominant factor in determining warpage. The reaction of shrinkage to packing pressure is monotonic, whereas the plot of warpage shows a U-shaped variation. A differential treatment of S&W can therefore help to enhance product quality. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

注射成型薄壁制品收缩与翘曲因素

介绍了薄壁注射成型的充填、保压、冷却和残余应力的数值模型,并将集成的模拟程序对收缩翘曲问题进行定量地模拟分析.采用Taguchi 实验优化设计理论,用L₂₇（3¹³）正交表设计实验并进行了统计分析.研究了因素如熔体温度、模具温度、保压时间、保压压力、浇口尺寸和注射速率对收缩与翘曲的影响的显著性.得出优化工艺参数如熔体温度、模具温度、保压时间和压力能减少残余热应力;保压压力和熔体温度是影响收缩与翘曲的最显著因素.     

Effect of processing conditions on shrinkage in injection molding

A systematic study on the effect of processing conditions on mold shrinkage was undertaken for seven common thermoplastic polymers. It turned out that the holding pressure was always the key parameter. The effect of the melt temperature is slightly less important. Injection velocity and mold temperature do not show a general trend for all polymers. It was shown that at least for amorphous polymers a simple thermoelastic model could describe all experimental results. For semi-crystalline materials the model overpredicts shrinkage.     

成型工艺参数对MBS、PP注塑件收缩率的影响

运用Taguchi技术研究了成型工艺参数对甲基丙烯酸甲酯-丁二烯一苯乙烯共聚物(MBS)和聚丙烯(PP)注塑制品收缩率的影响,并获得优化的成型工艺参数以使制品的收缩率最小.以碱性蓄电池壳为例,利用L9(34)正交矩阵进行实验,研究对比了成型工艺参数对制品收缩率的影响程度.结果表明,所选成型工艺参数中冷却时间和注射时间对MBS制品的收缩率影响较大.熔体温度和冷却时间对PP制品的收缩率影响较大.     

Effect of micro-lamellar talc on dimensional accuracy and stability in injection molding of PLA/PBSA blends

The present work is aimed at developing innovative solutions to enhance mechanical and physical properties of Poly(Lactic) Acid (PLA) blends, specifically designed for melt processing applications. Attention is drawn on dimensional accuracy and stability of PLA-based components manufactured by injection molding. PLA belongs to the class of bioplastic materials, entirely relying on renewable resources. It is a semi-crystalline linear aliphatic polyester, highly prone to recrystallize in harsh temperature conditions that can arise during transportation or storage of injection-molded components. Recrystallization is known to cause shrinkage of polymeric materials and, consequently, a marked warpage of components produced from them, causing scraps or parts that do not conform to the functional requirements. In this context, the experimental investigation deals with the effect of increasing amounts of micro-lamellar talc in PLA and Poly(butylene) Succinate Co-Adipate (PBSA) blends. In particular, the role of talc aliquot on dimensional accuracy and stability of injection-molded coffee capsules manufactured by PLA/PBSA blends is studied, with emphasis on the key role of recrystallization. For that purpose, commercial grade PLA and PBSA are compounded with micro-lamellar talc and several processing additives by a twin screw co-rotating extruder. The resulting compound is reprocessed to form coffee capsules by injection molding. Characterization tests include Differential Scanning Calorimetry (DSC), Attenuated Total Reflection Fourier Transform Infrared (ATR FT-IR) spectroscopy and Field Emission Gun Scanning Electron Microscopy (FEG – SEM). Measurements of the characteristic dimensions of the molded components reveals the effect of increasing amounts of talc in PLA/PBSA blends on dimensional accuracy and stability properties of coffee capsules. Brewing tests allowed to identify the formulations that can ensure the utmost geometrical accuracy of the coffee capsules and their suitability for brewing in instant coffee machine. Based on experimental evidences, lowest shrinkage and improved stability are found on components manufactured by polymeric blends that involve the highest amount of talc.     

No‐flow temperature in injection molding simulation

Most injection molding simulation packages use the no‐flow temperature (NFT) as a means of determining whether the polymer flows or is solid. The NFT is not well defined, and a standard method for measuring it does not exist. A sensitivity analysis of the filling stage has been carried out with two different packages [VISI Flow (Vero Software Limited, Gloucestershire, UK) and Moldflow (Autodesk, Inc., San Rafael, CA)] to estimate the influence of the NFT on the main processing parameters. The NFT has a large influence on the thickness of the frozen layer, but it does not appreciably affect the filling pressure. Because the NFT affects the frozen layer, an effect on the estimation of shrinkage and warpage is expected. Software packages have also been compared, and similar simulations have been found to produce contrasting results. A simple correlation for NFT estimation, derived from the Cross–Williams–Landel–Ferry equation, is proposed for both amorphous and semicrystalline polymers. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Theoretical and experimental studies of anisotropic shrinkage in injection moldings of various polyesters

A novel approach to predict anisotropic shrinkage of slow crystallizing polymers in injection moldings was proposed, using the flow‐induced crystallization, frozen‐in molecular orientation, elastic recovery, and PVT equation of state. In the present study, three different polyesters, polyethylene terephthalate, polybutylene terephthalate, and polyethylene‐2,6‐naphthalate (PEN), are used. The anisotropic thermal expansion and compressibility affected by the frozen‐in orientation function and the elastic recovery that was not frozen during moldings were introduced to obtain the in‐plane anisotropic shrinkages. The frozen‐in orientation function was calculated from the amorphous contribution based on the frozen‐in and intrinsic amorphous birefringence and crystalline contribution based on the crystalline orientation function determined from the elastic recovery and intrinsic crystalline birefringence. To model the elastic recovery and frozen‐in stresses related to birefringence during molding process, a nonlinear viscoelastic constitutive equation was used with the temperature‐dependent viscosity and relaxation time. Occurrence of the flow‐induced crystallization was introduced through the elevation of melting temperature affected by entropy production during flow of the viscoelastic melt. Kinetics of the crystallization was modeled using Nakamura and Hoffman‐Lauritzen equations with the rate constant affected by the elevated melting temperature. Numerous injection molding runs were carried out by varying the packing time, packing pressure, flow rate, melt and mold temperature, and anisotropic shrinkage of moldings were measured. The experimental results were compared with the simulated data and found in a fair agreement. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3526–3544, 2006     

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。     

Real‐time diagnosing polymer processing in injection molding using ultrasound

Ultrasonic diagnosing technique with a new high‐temperature ultrasonic transducer is developed to real‐time diagnose polymer processing and its morphology changes in injection molding processing. Compared with the previous researches, the new technique can provide more and accurate information. In this study, ultrasound diagnosis shows that longitudinal wave can real‐time characterize the data of the injection process and polymer morphology changes, including melt flow arrival time, the part ejection time, filling and packing stages, polymer solidification process, and the morphology changes during polymer crystallization. Shear waves can real‐time diagnose Young's and shear storage modulus, anisotropy property of polymer in injection molding. During our research, real‐time ultrasonic diagnosis shows that the storage modulus along the vertical direction is larger than that of the parallel to the melt flow direction under our setup injection conditions. Scanning electron microscopy and dynamic mechanical analysis measurements present that it is because the crystalline lamellas of HDPE are parallel arrangement and grow in a vertical to melt flow direction owing to injection shear force under a certain injection conditions. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Toward a viscoelastic modeling of anisotropic shrinkage in injection molding of amorphous polymers

A novel approach to predict anisotropic shrinkage of amorphous polymers in injection moldings was proposed using the PVT equation of state, frozen‐in molecular orientation, and elastic recovery that was not frozen during the process. The anisotropic thermal expansion and compressibility affected by frozen‐in molecular orientation were introduced to determine the anisotropy of the length and width shrinkages. Molecular orientation calculations were based on the frozen‐in birefringence determined from frozen‐in stresses by using the stress‐optical rule. To model frozen‐in stresses during the molding process, a nonlinear viscoelastic constitutive equation was used with the temperature‐ and pressure‐dependent relaxation time and viscosity. Contribution of elastic recovery that was not frozen during the molding process and calculated from the constitutive equation was used to determine anisotropic shrinkage. Anisotropic shrinkages in moldings were measured at various packing pressures, packing times, melt temperatures, and injection speeds. The experimental results of frozen‐in birefringence and anisotropic shrinkage were compared with the simulated data. Experimental and calculated results indicate that shrinkage is highest in the thickness direction, lowest in the width direction, and intermediate in the flow direction. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 2300–2313, 2005