【作者】 陈良；

【导师】 赵国群；

【作者基本信息】 山东大学 ， 材料加工工程， 2009， 硕士

【摘要】 注塑成型技术具有生产效率高、成本低、产品多样化等特点,是塑料制品的主要成型方法之一。然而,随着家电、通讯、电子、汽车、光电等行业的迅速发展,人们对塑料制品提出了壁厚更薄、结构更复杂、表面更美观、强度更高等方面的要求,传统注塑成型技术已经很难满足这种发展的需求。快速热循环注塑工艺(Rapid Heat Cycle Molding,RHCM)采取动态模温控制方法,在加热阶段加热模具表面到很高的温度,使得熔体可以在高模温下充模,从而提高熔体的充模能力和流动能力;在冷却阶段采用低温冷却介质快速冷却塑件,以缩短成型周期。利用该技术,可在保证生产效率的前提下,生产外观优越的塑料制品,例如:无熔接痕、无流痕、高光泽度等。此外,快速热循环注塑技术还可应用于薄壁件和具有微结构的塑料制件的成型。对于快速热循环注塑工艺,模具的加热冷却效率及温度均匀性,直接影响到其成型周期和最终产品的质量。因此,探讨如何提高加热冷却效率,并改善温度均匀性对快速热循环注塑工艺的生产应用具有重要意义。本文主要研究了蒸汽辅助加热和电热式RHCM工艺的关键技术,利用有限元数值模拟方法,分析了RHCM工艺加热、冷却过程的热响应规律,讨论了影响加热冷却效率和温度均匀性的因素,最后通过试验生产验证分析结果的有效性。通过与常规注塑工艺对比,研究了RHCM注塑工艺的原理,分析比较了各种动态温度控制方法的优缺点,分别制定了蒸汽辅助加热和电热式RHCM注塑工艺的流程和工艺方案。构建了蒸汽辅助加热RHCM模具的有限元分析模型,利用有限元分析软件ANSYS,对加热冷却过程进行了热响应分析,研究了加热/冷却管路尺寸及布局对加热冷却效率和温度均匀性的影响。结果表明,蒸汽辅助加热RHCM工艺的有效加热、冷却时间分别为30s、40s,其对应的平均加热、冷却速率分别可达4.3℃/s和4.9℃/s;利用180℃高温蒸汽加热时,模具表面温度存在一个温升极限,其值约为170℃;通过采用小直径密排的加热/冷却管道布局,可以有效改善RHCM注塑工艺的加热、冷却效率和温度均匀性。以液晶电视机面板的蒸汽辅助加热RHCM生产为例,通过构建模具的热响应分析模型,分别对该工艺的加热、冷却过程的热响应进行数值模拟,分析了整个模具系统的热响应过程。分析发现,液晶电视机面板模具的加热时间约为20s,加热结束时模具表面温度可达110℃;其冷却时间约为35s,冷却结束时塑件温度在85℃以下,可以被顶出。最后,通过将模拟数据用于液晶电视机面板的实际注塑生产,验证了分析结果的有效性。研究了利用电加热和冷却水冷却的RHCM注塑技术,设计了相应的电加热模具,构建了热响应分析的有限元模型,利用有限元分析软件ANSYS进行了瞬态传热分析。研究结果表明,利用电加热技术,型腔表面的平均升温速率可达7.3℃/s,模具表面可被持续加热故不存在温升极限;冷却过程中,熔体的平均降温速率约为4.1℃/s,冷却过程中熔体的温度均匀性较好。更多还原

【Abstract】 Due to the high productivity, low cost and the flexibility to wide variety of shapes, injection molding has become one of the most widely used processing technologies in plastic manufacturing industry. However, with the rapid growth of home electronics, communications device, electronics products, automotive, optoelectronics products, people have the requirement of much thinner and more complex parts which should also meet the high demand of the consumer on their appearance and strength and the conventional injection molding has been unable to meet this trend. Rapid Heat Cycle Molding (RHCM) is a new injection molding technology which uses the dynamic mold temperature control method. During the heating stage of RHCM, the mold surface is heated to a high temperature to make the melt fill cavity at this temperature and hence facilitate the filling and flowing of the melt. During the cooling stage of RHCM, the shaped melt is cooled down quickly by coolant to reduce the cycle time. The RHCM technology could produce plastic parts with high surface quality, such as no weld line, no flow mark, high surface gloss, on basis of guaranteeing the productivity. Furthermore, RHCM could be used in producing thin-wall parts and parts with microstructure.For RHCM, the heating/cooling efficiency and the temperature uniformity of the mold could affect productivity and the quality of the final part significantly. Therefore, research on how to improve the heating/cooling and the temperature uniformity has great significance in the application of RHCM. This thesis mainly studied the key technology of Steam-assisted heating Rapid Heat Cycle Molding (SRHCM) and Electric-heating Rapid Heat Cycle Molding (ERHCM). The heating and cooling thermal response rule were evaluated. Discussed the factors influenced the temperature uniformity through finite element analysis. Finally, the numerical simulation results were verified through experimental producing.The process principle of RHCM was studied through comparing RHCM with conventional injection molding. The advantages and disadvantages of various dynamic temperature control methods were studied and compared. The processes of Steam-assisted heating Rapid Heat Cycle Molding and Electric- heating Rapid Heat Cycle Molding were designed.The finite element analysis model of Steam-assisted heating Rapid Heat Cycle Molding mold was constructed. The thermal response during heating and cooling stage was simulated based on ANSYS. The influence of heating/cooling channels’ diameters and arrangements to heating/cooling efficiency and the temperature uniformity was evaluated. The results showed that the effective heating time, cooling time, heating speed, cooling speed of SRHCM are 30s, 40s, 4.3℃/s and 4.9℃/s respectively. When the mold was heated by steam of 180℃, its temperature had an upper limit value and the upper limit temperature was about 170℃. Furthermore, heating/cooling efficiency and the temperature uniformity could be improved by channels with small diameters and tight arrangements.The SRHCM technology used in producing liquid crystal display panel was studied as an actual example. The thermal response during heating and cooling stage was simulated respectively through constructing the thermal response analysis model. It could be concluded that the heating time of SRHCM mold is about 20s when the temperature of the mold surface was 110℃. The cooling time of the SRHCM mold is about 35s when the melt was cooled to 85℃. Finally, the simulation results were applied to practical SRHCM producing to verify its veracity.The Electric-heating Rapid Heat Cycle Molding with electric heating and cold water cooling was studied. The ERHCM mold was designed and the finite element analysis model was constructed. The transient thermal transfer was studied based on ANSYS. The simulation results showed that, when the mold was heated with electric, the average heating speed could reach 7.3℃/s and the mold surface could be heated with no upper limit temperature. During the cooling stage, the average cooling speed of the melt was about 4.1℃/s and the melt had good temperature uniformity.更多还原