注塑塑料制品的收缩特性

论述了注塑塑料制品的收缩机理和收缩过程,讨论了影响塑料收缩率与制品后收缩的主要因素,通过P-V-T状态图描述了塑料在注塑过程中的收缩特性。     

材料颜色对光聚合模塑制品尺寸精度影响的研究

研究了材料颜色对光聚合模塑制品尺寸收缩的影响规律。结果表明,光聚合模塑成型制品的收缩变形取决于材料颜色对光能的吸收作用,以及非活性组分对聚合的阻碍作用;材料对365 nm紫外光的透射率越高,材料的总收缩率越大,但最大收缩速率差异不大;材料的色深越高,材料的总收缩率与最大收缩速率越小。以此为基础,分析了不同颜色光聚合模塑成型制品的工艺特性。     

自动收缩测量仪

陶瓷、砖瓦、耐火材料等非金属材料制品,在干燥脱水过程及烧成过程中都会发生体积收缩,是这些制品在生产过程中一个最重要和显著的特性。制品干燥收缩率(即干燥敏感性大小)与烧成收缩率的大小直接决定生产工艺过程控制的难易和制品的质量。据统计在卫生瓷和日用瓷厂由于干燥收缩造成制品开裂,变形损坏占半成品损坏率的98％,烧成收缩造成损坏占制品废品率的85％;墙地砖生产中干燥收缩造成制品开裂变形的损坏占半成品损坏率的90％以上,烧成收缩造成的废品占损坏率的80％。国内外专家一致认为收缩是导致制品开裂和变形的最主     

注塑成型制件的尺寸稳定性研究

注塑制品冷却时的收缩程度主要取决于加工材料的组份凡从事塑料加工者,均知道注塑制品冷却时会发生收缩。收缩程度主要取决于所加工材料的组份。半结晶材料的收缩率比无定形材料的收缩率大,填料可以降低各种聚合物的收缩率,降低程度取决于所添加填料的类型和添加量。制品几何结构也是影响收缩率的一大重要因素,薄壁制品要比厚壁制     

PA成型收缩率与注射工艺条件的关系

分析了注塑制品的收缩机理及收缩过程，并讨论了聚酰胺（PA）注射成型过程中模腔平均压力、熔体温度、模温、充模速率、成型时间等工艺条件对其收缩率的影响及制品后收缩率的因素，给出了减小制品收缩率，提高制品尺寸稳定性的方法。     

PA成型收缩率与注射工艺条件的关系

分析了注塑制品的收缩机理及收缩过程，并讨论了聚酰胺（PA）注射成型过程中模腔平均压力、熔体温度、模温、充模速率、成型时间等工艺条件对其收缩率的影响及制品后收缩率的因素，给出了减小制品收缩率，提高制品尺寸稳定性的方法。     

基于MPI的注塑活塞收缩率预测分析

注塑行业的制品收缩率控制是控制产品质量的主要因素.通过分析注塑成品的收缩机理,掌握注塑成型制品的收缩规律,然后结合塑料供应商所提供的注塑材料平均收缩率,给出注塑成型制品各点的收缩率的预测值.     

注射成型温度对PP制品收缩率的影响

研究了影响聚丙烯（PP）制品收缩率的热膨胀、结晶和取向等因素，分别对制品模内收缩和后收缩的具体情况进行分析，揭示了注射温度和模具温度对PP制品收缩率的影响规律。     

基于有限元数值模拟技术的热固性塑料模压制品收缩率研究

以有限元数值模拟技术作为辅助手段,采用单独变量实验法对热固性塑料模压成型制品收缩率的影响因素、结构组成和变化规律进行了研究。结果表明:对制品收缩率影响较大的因素是模压成型过程中的成型压力、成型温度、保压时间等。制品的收缩率由模具弹性变形、模具热变形、制品弹性恢复、制品冷却收缩和"残余收缩"共同构成,其中权重最大的是"残余收缩"。模具弹性变形、模具热变形、制品弹性恢复、制品冷却收缩分别与成型压力和成型温度成线性相关关系,而当成型压力、成型温度、保压时间处于某一范围内时,"残余收缩"呈现出一定的稳定性。     

聚丙烯注射成型收缩研究进展

在介绍注射成型中浇日凝固前收缩、制品模内冷却讨程收缩及脱模后制品自由收缩的收缩讨程和热收缩、结晶收缩、取向收缩、负收缩及后收缩等注射成型收缩原因的笨础}一,详细回顾了聚丙烯(PP)分子结构、共混、填充及加入成核剂等因素对注射成型收缩率的影响。同时,还讨论了注射温度、成型压力、成型时间、模具温度、冷却时间、充模辣度等注塑工艺条件以及制品厚度对PP注射成型收缩率的影响,介绍了生产中注射成型收缩的控制方法     

一模两腔不对称薄壁塑件工艺参数对收缩的影响研究

以降低塑件收缩率为目标,运用模流分析技术和正交试验法,通过方差分析,研究了工艺参数对塑件收缩率的影响程度。结果表明,使用最优工艺参数组合得到的塑件收缩率值为4.3117 %,该值远小于25次正交试验得到的实验值;对于丙烯腈-丁二烯-苯乙烯共聚物(ABS)材料而言,各工艺参数对收缩率的影响程度排序为：注射时间>熔体温度>保压时间>模具温度>冷却时间>保压压力。     

Shrinkage behavior and optimization of injection molded parts studied by the taguchi method

Shrinkage behavior of a plastic plays a critical role in determining the final dimensions of an injection‐molded part. It is well known that process conditions affect many properties of plastic parts, including shrinkage. This study applies the Taguchi method to systematically investigate the effects of process conditions on the shrinkage (along‐ and across‐the‐flow directions) of three plastics: high‐density polyethylene (HDPE), general‐purpose polystyrene (GPS), and acrylonitrile‐butadiene‐styrene (ABS). The results show that HDPE, a semicrystalline plastic, shrinks more than GPS and ABS, two amorphous materials. The extent of anisotropic shrinkage in the along‐the‐flow and across‐the‐flow directions for HDPE is different from GPS and ABS. More shrinkage occurs in the across‐the‐flow direction of HDPE than in its along‐the‐flow direction. The reverse is true for GPS and ABS. Mold and melt temperatures, along with holding pressure and holding time, are the most significant influences on the shrinkage behaviors of three materials, although the importance of each is different for each plastic. The optimal conditions for reducing shrinkage identified by the Taguchi method are experimentally verified and validated by t‐statistic tests. The prediction matches very well with the experimental value for the along‐the‐flow shrinkage of GPS.     

新型扇形雾化喷嘴的实验研究

在对Y型喷嘴结构和雾化机理研究分析的基础上,设计了一种新型的扇形雾化喷嘴,并对该喷嘴进行了实验研究. 实验测量了不同气、液压力下扇形雾化喷嘴的流量、雾化角和索特尔平均粒径及其在空间上的横向和纵向分布. 通过对液流量用Y型喷嘴设计公式进行拟合,得到了公式中适合扇形雾化喷嘴设计的系数取值：m=0.39, b=0.98. 喷雾雾化角a大约在90o~98o之间,变化不大. 喷雾的索特尔平均粒径在空间横向呈类似"W"的分布,在空间纵向呈逐渐降低并趋于稳定的分布.     

Influence of polypropylene fiber geometry on plastic shrinkage cracking in concrete

Plastic shrinkage cracking remains a primary concern for placements with high surface/volume ratios that are subjected to early age drying. Polypropylene fiber reinforcement controls such cracking, but the exact influence of fiber diameter, length and geometry remains unknown. A test program was carried out to understand the influence of these variables. Four commercially available polypropylene fibers were investigated at dosage rates varying from 0.1% to 0.3%. A recently developed technique of plastic shrinkage testing using a fully bonded overlay was employed. In this technique, a fiber reinforced concrete overlay is cast on a fully matured subbase with protuberances and the whole assembly is allowed to dry in an environmental chamber. Cracking in the overlay is monitored with time and characterized. Results indicate that while polypropylene fibers in general are effective in controlling plastic shrinkage cracking in concrete, a finer fiber is more effective than a coarser one, and a longer fiber is more effective than a shorter one. Further, fiber fibrillations appear to be highly effective in controlling plastic shrinkage cracking.     

Quantifying part irregularities and subsequent morphology manipulation in stereolithography plastic injection moulding

Abstract

The direct use of moulds produced by stereolithography (SL) provides a rapid tooling technique which allows low volume production by plastic injection moulding. The greatest advantage of the process is that it provides parts that are the same as those that would be produced by metal tooling in a fraction of the time and cost. However, work by the authors demonstrates that the parts possess different characteristics to those produced by metal tooling. This knowledge defies the greatest advantages of the SL injection moulding tooling process – the moulded parts do not replicate parts that would be produced by metal tooling. This work specifically demonstrates that a different rate of part shrinkage is experienced and subsequently investigates the mechanisms in SL tooling that induce these different part properties. The work culminates in different approaches to modifying the moulding process which allow the production of parts whose key morphological characteristics are closer to those that have been produced from metal moulds.     

内球类型芯注塑模脱模结构设计

对于内球形(内圆柱)类结构的塑料件,脱模处尺寸小于直径尺寸,需要设计内球形(内圆柱)类型芯脱模结构,解决顶出塑料件常有干涉现象或顶坏塑料件的问题,详细阐述几种结构的设计.经过生产实践,脱模结构设计能满足脱模需求,保证塑料件的质量.     

同时实现两侧及斜下抽芯的注塑模设计

论述了该塑件的摆放方式及模具分型面选择，设计了实用的模具结构，论述了模具的结构特点和工作原理。模具的动模部分带齿-轮齿条抽芯机构，定模部分采用组合对分式滑块结构。利用斜销及齿轮-齿条抽芯机构同时完成塑件两侧抽芯和斜盲孔抽芯。模具结构紧凑，工作可靠，操作维修方便，成型塑件质量好，生产效率高。     

Fiber/Matrix load transfer in cyanate resin carbon fiber systems

Comparative single fiber fragmentation test measurements are used to charcterize cynate and epoxy resin interface load transfer with high modulus (HMS4) and high strength (AS4) carbon fibers. The HMS4 fiber forms a weak interface with a fiber controlled failure mode, and the AS4 fiber forms a strong interface with the resin properties, apparently determining the level of load transfer. The resin properties examined are critical surface energy for wetting, cure shrinkage, thermal shrinkage, and mechanical modulus and strength. The cynate and epoxy resins display no significant difference in critical surface energy. Cure shrinkage has a negligible effect on load transfer. The compressive force from thermal shrinkage is significant, but the larger Tg to testing temperature range of the cyanate resin is offset by the larger thermal expansion coefficient of the epoxy, resulting in a near equal compressive force for the two resins. There is little difference in modulus between the two resins but a significant difference in shear strength. This difference is reflected in the larger load transfer measurement for the cyanate resin. A comparison of simple one-dimensional elastic and plastic models for the fiber fragmentation experiment resulted in better conformity with the plastic model. This would indicate that interfacial failure occurs by plastic deformation of the resin for the systems of this study.     

基于气辅注射成型工艺CAE优化的汽车手柄模具设计

针对塑件壁厚大收缩变形大的成型问题,首先借助计算机辅助工程（CAE）分析确定了塑件的成型方式采用气辅注射成型（GAIM）工艺,经优化后,采用单点侧浇口进行浇注,两点注气口进行注气辅助成型。经注塑参数优化、注气参数优化后,能将塑件的收缩变形能控制在0.3 %~0.42 %之间。基于CAE分析,设计了塑件的一模两腔两次打开气辅成型两板模具,模具中,设置了一种复合式两次抽芯哈弗滑块机构、一种通用型斜导柱哈弗滑块机构来进行侧抽芯脱模。复合式机构中,先通过动模垫板与动模板之间的第一次打开,先实现斜型芯的抽芯,而后再通过定模板与动模板之间的第二次打开,来驱动哈弗滑块体进行侧抽芯。CAE优化分析对气辅注射成型模具结构的设计具有非常重要的指导作用,有利于整体设计效率的提升。     

基于MPI和灰色关联异型出风罩注塑参数优化

针对某异型出风罩注塑成型工艺,以聚碳酸酯/丙烯腈-丁二烯-苯乙烯共聚物(PC/ABS)工程塑料合金为填料,运用Moldflow软件对其注塑过程进行模流分析,通过田口实验设计研究了熔体温度、保压时间、保压压力、注射时间和模具温度对塑件收缩率和翘曲变形量的影响,得到它们对塑件收缩率的影响次序为:保压时间>熔体温度>保压压力>注射时间>模具温度,对翘曲变形量的影响次序为:保压压力>注射时间>熔体温度>保压时间>模具温度。基于灰色关联分析,获得了最优组合工艺参数,即:熔体温度280℃、模具温度为65℃、注塑时间2.1 s、保压时间11 s、保压压力21 MPa。优化后的仿真结果表明,塑件的体积收缩率为6.523%、翘曲变形量为0.80 mm,比灰色关联次序中位组合的样本数据分别降低6.9%和15.8%,并获得最大注射压力为20.34 MPa、最大锁模力为3.25×10^5 N,为后期模具的设计和注塑参数设定提供了有力的参考,缩短了模具开发周期。