Relationship between Microcellular Foaming Injection Molding Process Parameters and Cell Size

In order to study the relationship between the main process parameters and the cell size, the mathematical model of cell growth of microcellular foaming injection process is built. Then numeric simulation is employed as experimental method, and the Taguchi method is used to analyze significance of effect of process parameters on the cell size. At last the process parameters are focused on melt temperature, injection time, mold temperature and pretidied volume. The significance order from big to small of the effect of each process parameters on cell size is melt temperature, pre-filled volume, injection time, and mold temperature. On the basis of above research, the effect of each process parameter on cell size is further researched. Appropriate reduction of the melt temperature and increase of the pre-filled volume can optimize the cell size effectively, while the effects of injection time and mold temperature on cell size are less significant.

Effects of heat treatment on the properties of powder injection molded AlN ceramics

The effects of two different heat-treatment atmospheres,nitrogen atmosphere and reducing nitrogen atmosphere with carbon,on the properties of Y2O3-doped aluminum nitride（AlN） ceramics were investigated.The AlN powder as a raw material was synthesized by self-propagating high-temperature synthesis（SHS） and compacts were fabricated by employing powder injection molding technique.The polymer-wax binder consisted of 60 wt.% paraffin wax（PW）,35 wt.% polypropylene（PP）,and 5 wt.% stearic acid（SA）.After the removal of binder,specimens were sintered at 1850°С in nitrogen atmosphere under atmospheric pressure.To improve the thermal conductivity,sintered samples were reheated.The result reveals that the heat-treatment atmosphere has significant effect on the properties and secondary phase of AlN ceramics.The thermal conductivity and density of AlN ceramics reheated in nitrogen gas are 180 W·m^-1·K^-1 and 3.28 g·cm^-3 and the secondary phase is yttrium aluminate.For the sample reheated in reducing nitrogen atmosphere with carbon,the thermal conductivity and density are 173 W·m^-1·K^-1 and 3.23 g·cm^-3,respectively,and the secondary phase is YN.

Intelligent Setting and Optimization of Process Parameters for Plastic Injection Molding

An intelligent model employing case-based reasoning（CBR） and fuzzy inference was constructed in terms to the system characteristics of plastic injection molding and considering the molding personnel＇s thought during the molding trial-runs. The model describes the complex process of injection molding with a view to the characters and advantages of CBR and fuzzy theory. And it can be used to determine the initial process parameters and optimize the process parameters on-line. The key implementation technologies of the model are described in detail, including determining the initial process parameters based on CBR, correcting defects, optimizing process parameters based on fuzzy inference, etc. A corresponding intelligent system was developed which is integrated with injection machine by communicating with the controller.

Influence of the Compacts Homogeneity on the Incidence of Cracks during Thermal Debinding in Ceramic Injection Molding

During thermal debinding in ceramic injection molding, the inhomogeneity of green body is a key origin of cracks. In this study, the impact of low molecular weight binders on the homogeneity of the green body was investigated. Incidence of cracks during thermal debinding indicated that the volume ratio of wax to stearic acid should be out of high viscosity and incompletely wetting region. In these two formulation regions, typical inhomogeneous microstructures were observed. By mercury intrusion method, it was shown that pore size distribution of the debinded compacts was determined by thermal degradation of low molecular weight binders. A particle-rich region model was established to predict the nucleation of cracks caused by solid loading fluctuation. The criterion of cracks nucleation was that local capillary force from solid loading fluctuation was larger than the suction force from the surroundings.

Constitutive model and numerical simulation for injection molding of MgTiO_(3) ceramic parts

In order to predict the powder flow law of the injection molding process of MgTiO3 ceramic parts with complex structures,a constitutive model and numerical simulation method for MgTiO3 ceramic injection molding were established based on the Hunt method.The material parameters of MgTiO3 such as elastic modulus,Poisson ratio,glass transition temperature,thermal conductivity and specific heat capacity were measured.Based on the fitting curve and the material parameters measured,the cross-WLF viscosity model and P-V-T model required for MgTiO3 ceramic injection molding were optimized.Furthermore,the influence of process parameters on mold filling flow and distribution of parts defects was researched.It was found that the gate position,injection speed and melt temperature have greater influence on mold filling flow and the packing process has an obvious effect on parts’defects.On this basis,the MgTiO3 ceramic parts injection molding experiment verification was carried out.By comparing the experimental results with the simulated results,it is found that the deformation error is within 1.5%and the density error is within 1%.Therefore,this research provided theoretical guidance for the engineering application of MgTiO3 ceramic parts fabricated by injection molding.

A strategy to obtain a high-density and high-strength zirconia ceramic via ceramic injection molding by the modification of oleic acid

Despite its unique high efficiency and good environmental compatibility, the water-soluble binder system still encounters problems achieving a desired sintered part via ceramic injection molding because of the poor compatibility and the powder-binder segregation between ceramic powders and binders. The objective of this study was to obtain a sintered part with excellent properties by introducing a small quantity of oleic acid to the surface of zirconia powders before the mixing process. As opposed to many previous investigations that focused only on the rheological behavior and modification mechanism, the sintering behavior and densification process were systematically investigated in this study. With the modified powders, debound parts with a more homogeneous and smaller pore size distribution were fabricated. Also, a higher density and greater flexural strength were achieved in the sintered parts fabricated using the modified powders.

Effects of different backbone binders on the characteristics of zirconia parts using wax-based binder system via ceramic injection molding

In this work,various backbone binders were used in wax-based binder system to formulate zirconia parts by ceramic injection molding (CIM).The effect of different backbone binders on the molding,debinding,and sintering behaviors was investigated.After blending process,the feedstock using multi-polymer components exhibited more homogeneous structure compared with that using the mono-polymer ones due to the synergistic effect of multi-polymers.During solvent debinding,some defects such as 'slumping' and 'peeling' appeared in the parts containing ethylene-vinyl acetate copolymer (EVA),but they were not found in the parts with other thermal polymers.Also,as for the parts after sintering,the one using low density polyethylene (LDPE) and high density polyethylene (HDPE) as backbone binders presented a more uniform microstructure with finer zirconia grains among all the investigated compositions,and thus obtained the highest flexural strength (～949 MPa) and relative density (～98.9％).

Injection molding of ultra-fine Si_3N_4 powder for gas-pressure sintering

The ceramic injection molding technique was used in the gas-pressure sintering of ultra-fine Si3N4 powder. The feedstock＇s flowability, debinding rate, defect evolution, and microstructural evolution during production were explored. The results show that the solid volume loading of less than 50vol% and the surfactant mass fraction of 6wt% result in a perfect flowability of feedstock; this feedstock is suitable for injection molding. When the debinding time is 8 h at 40°C, approximately 50% of the wax can be solvent debinded. Defects detected during the preparation are traced to improper injection parameters, mold design, debinding parameters, residual stress, or inhomogeneous composition distribution in the green body. The bulk density, Vickers hardness, and fracture toughness of the gas-pressure-sintered Si3N4 ceramic reach 3.2 g/cm^3, 16.5 GPa, and 7.2 MPa·m^1/2, respectively.

Intelligent methods for the process parameter determination of plastic injection molding

Injection molding is one of the most widely used material processing methods in producing plastic products with complex geometries and high precision. The determination of process parameters is important in obtaining qualified products and maintaining product quality. This article reviews the recent studies and developments of the intelligent methods applied in the process parameter determination of injection molding. These intelligent methods are classified into three categories： Case-based reasoning methods, expert sys- tem-based methods, and data fitting and optimization methods. A framework of process parameter determination is proposed after comprehensive discussions. Finally, the conclusions and future research topics are discussed.

Effect of sintering parameters on powder injection molded Ti(C, N)-based cermets

Effect of two-stage sintering parameters such as heating rate, top sintering temperature and holding time, sintering temperature and holding time at the second stage on relative density, transverse rupture strength(TRS) and microstructures of powder injection molded Ti(C, N)-based cermets were investigated, by means of Archimedes’s method, three-point bending test and micrographic analysis. The results show that the optimum sintering cycle for powder injection molded Ti(C, N)-based cermets comprises rapid heating (10℃/min) at low temperatures, slow heating (5℃/min) at intermediate temperatures, holding at the highest sintering temperature (1420℃) for a short time (10min), and holding at the second stage (1360℃) for a longer time (6h) to avoid grain coarsening, and that its TRS reaches 624MPa, and there are little pores in their microstructures.

Determination of Optimal Manufacturing Parameters for Injection Mold by Inverse Model Basing on MANFIS

Since plastic products are with the features as light, anticorrosive and low cost etc., that are generally used in several of tools or components. Consequently, the requirements on the quality and effectiveness in production are increasingly serious. However, there are many factors affecting the yield rate of injection products such as material characteristic, mold design, and manufacturing parameters etc. involved with injection machine and the whole manufacturing process. Traditionally, these factors can only be designed and adjusted by many times of trial-and-error tests. It is not only waste of time and resource, but also lack of methodology for referring. Although there are some methods as Taguchi method or neural network etc. proposed for serving and optimizing this problem, they are still insufficient for the needs. For the reasons, a method for determining the optimal parameters by the inverse model of manufacturing platform is proposed in this paper. Through the integration of inverse model basing on MANFIS and Taguchi method, inversely, the optimal manufacturing parameters can be found by using the product requirements. The effectiveness and feasibility of this proposal is confirmed through numerical studies on a real case example.

聚碳酸酯气体辅助注射成型制品内应力分布及改善工艺

聚碳酸酯(PC)注塑制品出模后在无外加约束条件下内部应力得不到松弛释放,易导致制品产生开裂,严重影响制品的服役性能。为探究PC制品内应力分布规律,找到有效降低内应力的工艺措施,基于气体辅助注射成型(GAIM)工艺和自行设计制造的带有半圆形加强筋的平板试验模具,结合光弹法和溶剂检测法,研究GAIM制品内应力的分布特点,讨论注气压力和气体保压压力两种工艺参数对GAIM制品内应力的影响规律,提出两种改善制品内应力的工艺方法。研究发现:通过光弹法观测到的应力条纹分布与溶剂浸泡后的裂纹开裂区域一致,即GAIM制品末端及边缘处内应力较大,沿气道两侧应力分布较均匀;较高的注气压力和较低的气体保压压力可以更加有效减小GAIM制品的内应力;通过对GAIM制品24 h即时退火和延长二次注气的卸压时间可以有效降低制品内应力。

工艺参数对微结构注塑制品重量和复制精度的影响

微结构注塑制品的重量重复精度及微结构复制精度是衡量微结构注塑制品成型质量的重要指标。通过实验研究了熔体温度、模具温度、注射压力、保压压力和保压时间等重要工艺参数对制品重量及微结构复制精度的影响。实验结果表明,各个工艺参数均对微结构注塑制品存在不同程度的影响,熔体温度和注射压力是影响制品重量的主要因素,保压时间是影响微结构复制精度的主要因素。当熔体温度从270℃增大至310℃时,制品平均重量从4.9406 g提高到5.4431 g,当注射压力从110 MPa增大至150 MPa时,制品重量重复精度从1.6494%提高到0.1240%,当保压时间从5 s增大至8 s时,微结构复制精度从89.771%提高至96.188%。

基于多基因遗传规划的注塑过程参数关联预测方法

鉴于传统注塑过程参数选择与设置依赖于人工经验,且过程参数与输出参数之间存在着非线性、强耦合的关系,文中提出了一种基于多基因遗传规划的注塑过程参数关联预测方法。该方法基于数据生成初始多基因树种群,随后迭代进行选择,高、低级树交叉及两类树突变操作,以获得最适应数据的模型,并演化出一个能清晰描述过程参数与输出参数关联的代数方程,确定控制输出的关键参数。在设置选择指标时,针对模型方程的复杂性会影响到实际使用效率的问题,引入复杂性维度作为评估指标进行多目标选择。以注塑过程为例,试验结果表明了所提方法的有效性。此外,参数和灵敏度分析验证了模型的鲁棒性,揭示了参数间隐藏的非线性关系,对后续注塑过程参数设置及优化提供了依据。

高比表面积3YSZ粉体注射成型工艺参数优化及制品力学性能

为解决高比表面积的3YSZ陶瓷粉末难以应用于注射成型工艺的问题,以比表面积为18 m^(2)/g的3YSZ陶瓷粉末为原料,以生坯质量为正交试验的评价标准,优化得到了最优注射参数,并对烧结制品的力学性能进行了研究。结果表明:参数影响力的顺序为注射压力>保压时间>注射速度>注射温度,适用于该粉体的最优注射参数为注射温度165℃,注射压力110 kg,注射速度为85 g/s,在70 kg下保压1 s。将使用该工艺得到的生坯脱脂后,于1350℃下烧结即可得到相对密度为98.5%,维氏硬度为13.42 GPa,断裂韧性为6.47 MPa·m^(1/2)的四方多晶氧化锆陶瓷。

基于BP-SSA神经网络模型的中框塑件翘曲变形优化

为减小挂壁风机中框在注塑成型中的翘曲变形,运用Moldflow软件对中框进行仿真,以模具温度、熔体温度、注射时间、冷却时间、保压时间和保压压力6个工艺参数进行正交试验设计,基于试验结果建立工艺参数与翘曲变形量之间的反向传播(BP)神经网络模型,利用麻雀搜索算法(SSA)对模型进行全局参数寻优。结果表明,当模具温度为80℃、熔体温度为250℃、保压压力为82 MPa、保压时间为20 s、注射时间为3 s、冷却时间为26.25 s时翘曲变形量最小,预测翘曲变形量为2.483 mm。利用Moldflow软件对寻优得到的工艺参数进行验证,结果显示仿真计算的翘曲变形量为2.449 mm,与优化算法结果误差为1.3%,并将寻优获得的参数进行试模验证,试模翘曲结果与优化算法结果误差为2.6%,证明了优化算法的准确性,且注塑件外观无飞边缩痕等缺陷,装配效果符合预期要求。研究结果表明BP神经网络结合麻雀搜索算法优化工艺参数的技术方法具有可行性。

基于机器学习与遗传算法的注塑产品工艺参数优化

注塑成型工艺可以高效成型高精度产品,被广泛使用。通过优化注塑产品工艺参数,可以获得更高的表面质量和尺寸精度。为了获得最佳工艺参数组合,设计了基于关键工艺参数组合的极端梯度提升决策树模型。为了解决训练数据不平衡问题,引入尺寸加权修正方法,提高对不合格产品尺寸的预测精度。使用遗传算法对改进极端梯度提升决策树模型以产品尺寸误差最小为目标进行全局寻优,得到最佳工艺参数组合。最佳工艺参数组合为模腔压力39.4 bar、切换压力33.8 bar、射嘴压力49.4 bar、回水温度72.6℃、模温机水流量58.7 cm^(3)/s。

浅谈注塑车间工艺参数标准化

本文围绕注塑车间注塑工艺标准化展开深入探讨,详细分析注塑参数的设定及其对工艺的重要影响,深入研究当前注塑车间工艺不标准的具体表现及引发的问题,系统阐述实施注塑工艺标准化的策略,并通过实际案例进行验证和分析。旨在为注塑行业提升生产水平和产品质量提供全面的理论指导和实践参考。

基于CAE分析的电池盖注射模设计

利用华塑HsCAE3D7.5模流分析软件对电池盖注射模进行仿真,对比两种不同浇口类型方案,通过对剪切力以及流动结束时的温度场分析,确定了浇注系统采用点浇口进胶。设计了两种冷却水路方案,通过对冷却时间和流动前沿温度的对比,最终确定了方案一的冷却效果较好。结合产品结构特点,最终设计了具有斜顶推出机构以及侧向分型抽芯机构的点浇口双分型面注射模。