【作者】 张志强；

【导师】 宋满仓；

【作者基本信息】 大连理工大学 ， 机械设计及理论， 2016， 硕士

【摘要】 薄壁注塑成型技术近年来迅速发展,以其节能环保、降低成本、缩短成型周期等优点备受广大学者关注。薄壁制品以其体积小、质量轻、成本低等优势广泛应用于生物医疗、航空航天等多个领域。然而,薄壁注塑成型过程周期短、过程复杂,所以制品极易出现短射、收缩不均、翘曲等成型质量缺陷。本文从模具本身的浇口结构入手,通过改变浇口的形状和尺寸调节熔体在型腔中的流动行为,使熔体尽快达到流动平衡,进而提高薄壁制品的成型质量。首先,为开展后续相关注射成型实验,设计一套型腔尺寸连续可变的薄壁注塑成型模具。在模具设计过程中,提出运用T型滑块带动型腔滑板移动的方式,来实现型腔尺寸的连续可变,改变了传统模具通过更换镶块来实现型腔尺寸变化的方式,避免了拆卸模具、更换镶块的繁琐操作,降低了成本。其次,探究针对不同长宽比的薄壁制品,变截面浇口对熔体填充型腔时流动行为及制品成型质量的影响规律。运用相同材料和注塑工艺参数,分别用等面积等宽度的变截面浇口和传统扇形浇口进行数值模拟和注射成型实验,对比分析熔体前沿流程差,薄壁制品沿宽度方向收缩率不均现象和翘曲变形量。研究结果表明：随着薄壁制品长宽比不断减小,变截面浇口对熔体流动行为及薄壁制品成型质量影响效果逐渐减弱。再次,探究鼓包宽度和鼓包长度对熔体填充型腔时流动行为及薄壁制品成型质量的影响规律。运用不同鼓包尺寸的变截面浇口和传统扇形浇口进行数值模拟和注射成型实验,对比分析熔体前沿流程差,薄壁制品沿宽度方向收缩率不均现象和翘曲变形量。研究结果表明：鼓包宽度对熔体流动行为及薄壁制品成型质量基本没有影响；随着鼓包长度的减小,变截面浇口对熔体流动行为及薄壁制品成型质量影响效果逐渐减弱。最后,探究针对不同材料,变截面浇口对熔体流动行为及薄壁制品成型质量的影响规律。采用PP、PMMA、PC 3种成型材料进行数值模拟和注射成型实验,对比分析熔体前沿流程差,薄壁制品沿宽度方向收缩率不均现象和翘曲变形量。研究结果表明：相对于PP,成型材料为PMMA和PC时变截面浇口的分流效果更明显,对熔体流动行为的影响更大；相对于PP,成型材料为PMMA和PC时变截面浇口对薄壁制品收缩不均现象影响效果更明显；成型材料为PMMA和PC时,变截面浇口对薄壁制品翘曲变形影响基本一致。更多还原

【Abstract】 The thin-wall injection molding technology is emerging technology which develops from the traditional injection molding technology and is used for forming all types of thin-walled plastic parts. The thin-wall injection molding technology has a lot of advantages of saving energy and protecting environment, reducing cost and shorting the experimental period. The thin-walled plastic parts are widely used in many fields including biomedical field, aerospace, automobiles,home appliances and instrumetation for its advantages such as small volume, light quality and low cast. The process time of thin-wall injection molding is very short and the process is complicated.As a result a lot of quality problems such as short shot, uneven shrinkage and warpage appear. The structure and the size of the gate were changed, which could control the behavior of melt flow, achieve balanced filling process and increase the forming quality of thin-walled plastic parts.Firstly, thin-walled injection mold with continuous variable cavity size was designed to complete follow-up injection molding experiments. During the design of the mould, the method of using movable slider to get continuous variable cavity size was put forward,which could replace the traditional method of using cavity inserts to change cavity size. The thin-walled injection mold with continuous variable cavity size can reduce the cost, shorten the experimental period and ensure the follow-up injection molding experiments.Secondly, the effects of variable cross-section fan gate on the melt flow behavior and the forming quality of thin-walled plastic parts with different aspect ratio were researched. The injection molding experiments and numerical simulation were completed by variable cross-section fan gate and traditional fan gate.And during the experiments and numerical simulation the injection molding parameters and materials were the same.After the experiments, the melt front distance difference, uneven shrinkage and warpage of variable cross-section fan gate were contrasted with those of traditional fan gate.The results showed that with the decreasing of the thin-walled plastic parts’length-width ratio, the effects of variable cross-section gate would decrease.Thirdly,the effects of bulge length and width on the melt flow behavior and the forming quality of thin-walled plastic parts with different aspect ratio were researched. The injection molding experiments and numerical simulation were completed by variable cross-section fan gate and traditional fan gate.And during the experiments and numerical simulation the injection molding parameters and materials were the same.After the experiments, the the melt front distance difference, uneven shrinkage and warpage of variable cross-section fan gate were contrasted with those of traditional fan gate.The results showed that the bulge width has little influence on the melt flow behavior and the forming quality of thin-walled plastic parts, Besides with the decreasing of bulge length, the effects of variable cross-section gate on the melt flow behavior and the forming quality of thin-walled plastic parts would decrease.Finally, according to different materials the the effects of variable cross-section fan gate on the melt flow behavior and the forming quality of thin-walled plastic parts were researched. PP, PMMA and PC were used in the injection molding experiments and numerical simulation.After the experiments, the the melt front distance difference, uneven shrinkage and warpage of variable cross-section fan gate were contrasted with those of traditional fan gate.The results showed that compared to PP, if PMMA and PC were used, the diversion effect of variable cross-section fan gate could be more effective, but the effect of reducing plastic shrinkage unevenness would decrease. Besides according to PMMA and PC the effects of variable cross-section fan gate on warpage were basically the same更多还原