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RHCM成型制品高光面形成微观机理研究 总被引:3,自引:0,他引:3
根据快速冷热成型技术(RHCM)成型塑料熔体在型腔内的填充流动规律,在普通注射成型机理研究基础上,从微观角度对RHCM技术在提高制品对模具的复原性,消除熔接痕、凹痕、银丝纹、流纹、表面浮纤等表观缺陷以及改善制品表面色差等方面的成型机理进行研究。结果表明,正是由于RHCM高温快速成型这一工艺特点,一方面确保熔体在型腔内的充分扩展与汇合,另一方面最大程度的限制制品的成型收缩,从而确保制件的最终成型品质。 相似文献
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注塑成型工艺试验优化设计 总被引:1,自引:0,他引:1
针对注塑成型工艺中存在的缺陷,引入正交试验设计方法,进行模具结构和工艺参数的优化设计。以模具温度、保压压力、保压时间和模内冷却时间作为影响因素,以体积收缩率、缩痕指数和熔接痕长度作为评估指标,通过利用Moldflow软件模拟熔体在型腔内的流动,得到各工艺参数影响制品成型质量的趋势图。通过正交试验设计分析,得到各工艺因素对体积收缩率、缩痕指数和熔接痕影响的程度,结合极差分析、方差分析法综合比较各组试验模拟结果,获得最优化的工艺参数组合。 相似文献
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本文介绍以透明模注射成型制品时,喷射充模流动和形成熔接痕的观测结果。利用改变型腔厚度、浇口尺寸和位置。以及在不同位置安放特殊形状嵌件的方法,探讨产生喷射现象和熔接痕形成的规律,提出防止喷射及改善熔接质量的建议。利用在透明模上装置偏振光镜片,分析注射制品浇口区附近及熔接痕的内应力分布规律。 相似文献
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为提高空调面板注射成型时熔接痕的力学性能及表观性能,针对提出的模具差温控制策略,对空调面板的浇口进行了优化设计。利用CAE分析软件Moldflow,对不同浇口位置及形式的空调面板注射成型过程进行了模拟,分析了型芯和型腔进行差温控制时熔体的充模流动状态,研究了充填时间、熔体温度及熔体流动前沿温度等对熔接痕力学性能及表观性能的影响,指导了最佳浇口位置及形式的选择。研究结果表明,在空调面板液晶框处采用同侧向下的两个扇形浇口进胶,且型腔比型芯温度高的模具差温控制策略,可以显著提高熔接痕的结合强度及塑件的外表面质量。 相似文献
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针对用聚碳酸酯/丙烯腈-丁二烯-苯乙烯三元共聚物注塑成型的带孔薄板,在用Moldflow软件模拟注塑成型过程的基础上,利用Taguchi法设计了L25(56)的正交试验,用信噪比衡量制品的熔接痕长度,采用方差分析法分析型腔温度、型芯温度、熔体温度等工艺参数对制品熔接痕长度的影响,并预测了最佳注塑工艺参数。结果表明:在所选择的工艺参数中,对熔接痕长度的影响程度由大到小依次为熔体温度(34.52%)、型腔温度(20.36%)、保压压力(19.43%)、保压时间(13.54%)、型芯温度(6.42%)、注射时间(5.73%)。在最佳工艺参数条件下注塑薄板塑料制件,不仅可以减小熔接痕长度,也有利于提高塑料制件的外观质量。 相似文献
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Thermotropic liquid crystal polymers consist of rod-like molecules and are often called “self reinforcing thermoplastics.” Their rheological behaviors as well as orientation development during processing are often very similar to those of short fiber-filled composites. Without reinforcement, the polymer shows superior mechanical properties to conventional glass fiber-reinforced engineering resins. The orientation distribution in the crosssection as well as flow patterns in the molded thermotropic polymers are clearly visible to the naked eye due to color differences. This makes it particularly convenient to study the orientation distribution as well as the flow patterns of packing, back flow, jetting, flow instabilities, and weld line formation in injection molding. This paper discusses physical properties of a typical ther motropic polymer and their relationship to mold filling process in the injection molding. 相似文献
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《应用陶瓷进展》2013,112(4):178-181
AbstractA multi-thickness mould cavity incorporating replaceable mould face plates of differing thickness was constructed for assessing the integrity of large section mouldings. The jetting phenomenon, which leads to a moulding replete with weld lines, was overcome for 15 mm thick mouldings by adjusting the nozzle and sprue diameters and by changing the angle of impingement of the melt on the opposite face of the cavity. However, for 25 and 35 mm cavities the formation of multiple weld lines during mould filling could not be completely eliminated. The emergence of cracks near the surface in some sintered parts could be traced back to the formation of weld lines in the injection stage. 相似文献
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Shixun Zhang Shaozhen Hua Wei Cao Zhiyu Min Yongzhi Liu Yaming Wang Changyu Shen 《Polymer Engineering and Science》2019,59(Z2):E397-E405
A three‐dimensional model and algorithm were proposed to simulate the jetting phenomenon in injection molding. The Giesekus model was employed to describe the viscoelastic behavior of the incompressible, non‐isothermal polymer flow, and the volume of filling method was used to track the jetting free surface and advancing melt front. The governing and constitutive equations were discretized by finite volume method. To improve the precision and stability of the numerical method, a modified pressure implicit with splitting of operator algorithm was proposed to solve the pseudo Navier–Stokes problem, and an iterative scheme was constructed to determine the solution of the coupled nonlinear equations. Numerical results showed this method successfully predicted the snake‐like flow in thin‐wall cavities and buckling flow in thick‐wall cavities. The viscoelastic characteristics of polymer influenced the reptile swing frequency and amplitude. Finally, a suitable nonlinear parameter in the Giesekus model improved the precision of simulation. POLYM. ENG. SCI., 59:E397–E405, 2019. © 2019 Society of Plastics Engineers 相似文献
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Yutaka Kobayashi Gensei Teramoto Toshitaka Kanai 《Polymer Engineering and Science》2011,51(3):526-531
In this article, a weld line placed behind an obstacle in an injection‐molded plaque made of metallic mold‐in‐color polypropylene (PP) was investigated. A broad uneven glossy section was visually observed along the weld line after the v‐notch weld disappeared. Although disk‐shaped metallic pigments were oriented parallel to the wall according to laminar flow, the pigment particles at the weld behind the obstacle were ordered vertically at the center of the depth direction. In PP molded without pigment, a black line was observed at the same position in the metallic weld. Based on a measurement of the crystal structure, the black line was caused by the rapid cooling of molten PP. Elongational flow occurred along the weld line after the diminishing v‐notch weld. The unique flow ordered the pigments obliquely at the advancing flow front and disturbed the subsequent flow of hot PP which transferred heat to the crystallizing mass. POLYM. ENG. SCI., 2011. © 2010 Society of Plastics Engineers 相似文献
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Koji Yamada Kiyotaka Tomari Umaru Semo Ishiaku Hiroyuki Hamada 《Polymer Engineering and Science》2005,45(8):1059-1066
Fracture toughness of adjacent flow weld lines, defined as weld lines that occur when two flow fronts meet and continue to flow together in the same direction (meld line or hot weld line), was evaluated by the single‐edge notched‐bend (SENB) method using three differently‐shaped obstructive pins. Although the fracture toughness varied depending upon the shapes of the pin, the values could be standardized as the distance from the meeting point of the two flow fronts flowing around the pin. The fracture toughness decreased drastically from the meeting point along the weld line and then slightly increased. These characteristic features could be explained by flow‐induced molecular orientation at the weld line interface. The molecules around the meeting point that were initially oriented parallel to the weld line due to fountain flow were able to relax, and then entanglement across the weld line interface developed because the flow stopped in the middle of the filling process, resulting in high fracture toughness. In contrast, the material at the downstream side of the weld line continued flowing during the filling process, being stretched along the flow direction. So, the molecular orientation at this area could not relax. In addition, the V‐notch shape, i.e., the depth and length at the surface of the weld line, which also varied depending on the shape of the obstacles, was considered to be identical when the meeting point was allowed to be a datum point. Thus, the meeting point was found to be a significant factor when the properties of weld lines are investigated. POLYM. ENG. SCI., 45:1059–1066, 2005. © 2005 Society of Plastics Engineers 相似文献
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Jung Seop Lim Soo Hyung Ban Dong Sup Kim Kwang Yeol Kwon Sang Hoon Lee Jong Kwan Lim Sung Hwan Cho 《应用聚合物科学杂志》2020,137(37):49084
We investigated the appearance of flow and weld lines when metallic pigments are used in polymer blends and how such lines can be eliminated by improving the pigment particle shape and optimizing pigment loading. Acrylonitrile butadiene styrene copolymer and two types of aluminum flakes, lamellar and three-dimensional (3D), were blended in a twin-screw extruder with a screw diameter of 25 mm. The temperatures from the hopper to the nozzle were 140, 180, 220, 220, 220, 220, and 220°C. Weld and flow lines were observed using field-emission scanning electron microscopy and energy dispersive X-ray spectroscopy of specially manufactured injection specimens. In the flow line region, traditional lamellar flakes were randomly oriented, while 3D flakes exhibited a distinct and stable orientation. Based on these observations, flow and weld lines in a finished metal/polymer blend can be minimized by using 3D metal particles in place of lamellar flakes. We also investigated the effects of aluminum flake loading on weld and flow line visibility. At low loading, weld lines were clearly visible due to the lack of pigmentation in the front of the polymer flow. Conversely, high loading resulted in relatively high concentrations of pigment near the weld line area, reducing weld line visibility. These findings suggest that there is an optimum metal loading level where the visibility of flow and weld lines is minimized. 相似文献
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Lingyun Wang Xiaohui Du Yipan Li Zhiwei Luo Gaofeng Zheng Daoheng Sun 《Journal of Adhesion Science and Technology》2013,27(1):53-64
In this paper, fundamental equations for jetting dispenser are presented to express the influence of adhesive pressure, nozzle diameter, and needle movement law, and the equations are then verified by flow behavior simulation. Subsequently, a novel jetting dispenser system is built to finish experiments about the mentioned influence parameters, and simulation results verify the regularities from experiment are correct. Flow velocity in the central nozzle will be faster and radius of the droplet will be bigger if the pressure in the chamber became higher, flow velocity in the central nozzle will be constant and the radius of the droplet will be bigger if the dead time became longer, and bigger nozzle diameter can lead to faster flow velocity in the central nozzle and bigger droplet. Besides, these mentioned works prove that our designed jetting dispenser is practical and useful for adhesive jetting. 相似文献
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The polymer injection products produced by using the current injection molding method usually have many defects, such as short shot, jetting, sink mark, flow mark, weld mark, and floating fibers. These defects have to be eliminated by using post-processing processes such as spraying and coating, which will cause environment pollution and waste in time, materials, energy and labor. These problems can be solved effectively by using a new injection method, named as variotherm injection molding or rapid heat cycle molding (RHCM). In this paper, a new type of dynamic mold temperature control system using steam as heating medium and cooling water as coolant was developed for variotherm injection molding. The injection mold is heated to a temperature higher than the glass transition temperature of the resin, and keeps this temperature in the polymer melt filling stage. To evaluate the efficiency of steam heating and coolant cooling, the mold surface temperature response during the heating stage and the polymer melt temperature response during the cooling stage were investigated by numerical thermal analysis. During heating, the mold surface temperature can be raised up rapidly with an average heating speed of 5.4°C/s and finally reaches an equilibrium temperature after an effective heating time of 40 s. It takes about 34.5 s to cool down the shaped polymer melt to the ejection temperature for demolding. The effect of main parameters such as mold structure, material of mold insert on heating/cooling efficiency and surface temperature uniformity were also discussed based on simulation results. Finally, a variotherm injection production line for 46-inch LCD panel was constructed. The test production results demonstrate that the mold temperature control system developed in this study can dynamically and efficiently control mold surface temperature without increasing molding cycle time. With this new variotherm injection molding technology, the defects on LCD panel surface occurring in conventional injection molding process, such as short shot, jetting, sink mark, flow mark, weld mark, and floating fibers were eliminated effectively. The surface gloss of the panel was improved and the secondary operations, such as sanding and coating, are not needed anymore. 相似文献