【作者】 董红军；

【导师】 祝铁丽；

【作者基本信息】 大连理工大学 ， 机械制造及其自动化， 2012， 硕士

【摘要】 注塑模内装配技术是将注塑成型过程和塑件的装配过程结合在一起的技术。该技术能够有效减少或避免塑料组件的模外装配工作,减少工人的劳动量,缩短产品生产周期,降低成本,提高企业的经济效益,目前已经在汽车、玩具、电器、航空等领域得到应用。然而,注塑模内装配技术在微注塑领域的研究和应用刚刚处于起步阶段,尚有许多难题未得到充分的解决。因此,本文以微小塑料铰链的注塑模内装配技术为研究对象,对其成型工艺和成型装置进行了较全面的研究和探索。首先,分析研究了采用注塑模内装配技术成型微小塑料铰链的技术原理,提出了塑料铰链不发生粘接的前提条件,进行了塑料铰链运动间隙获得方式的理论分析。认为采用注塑模内成型微小塑料铰链时,塑件之间是否发生粘接与后成型的塑件传递给先成型塑件的热量有关,铰链的运动间隙取决于塑料微轴与塑料微孔的相对收缩量。其次,对微小塑料铰链的结构进行了优化,使其更适于采用注塑模内装配技术成型。在此基础上,对其成型工艺进行了分析,提出了先成型微孔塑件、后成型微轴塑件的成型方案。再次,在原理分析和成型工艺分析的基础上,设计了一套能够在单筒注塑机上进行微小塑料铰链模内装配注塑成型的模具。该模具不仅能够在单筒注塑机上实现多阶段注塑成型,而且有效地保护了微细型芯,使其在高压聚合物熔体的高速冲击下不发生弯曲变形。最后,采用高密度聚乙烯(HDPE)和聚丙烯(PP)分别进行了同种聚合物和不同种聚合物的微小塑料铰链装配实验。实验结果表明,在采用注塑模内装配技术成型微小塑料铰链时,只要满足不粘接的前提条件,无论是采用同种聚合物还是不同聚合物,都可以装配出可以灵活转动的铰链。实验还表明,第二阶段塑件的注射成型压力对微轴与微孔的形状有一定的影响,当第二阶段的注射压力较大时,塑料微轴和塑料微孔呈现锥状,微小塑料铰链的运功间隙减小,甚至使塑料微轴与塑料微孔之间为过盈配合,无法发生相对转动。此外,在第二阶段注塑成型过程中过于追求较低的成型温度是不可取的,因为较低的成型温度需要配合较高的注射压力才能使塑件填充完整,而较高的注射压力会对微小塑料铰链装配质量带来不良的影响。更多还原

【Abstract】 In-mold assembly technology integrates assembly of plastic parts into injection molding. This technology can effectively reduce or even avoid the work of assembly after molding, shorten the cycle time of production, lower the cost and enhance the economic benefit of enterprise. Now, it has been extensively used in making parts of cars, toys, electrical equipments and military. But application of in-mold assembly technology in micro-injection molding is just on start. There are many questions to be resolved. So this master thesis takes in-mold assembly of the mesoscale polymeric joint as the research object, and makes deeply study on the molding process and molding equipments.At first, theoretical analyses are carried out for the technique principles of in-mold assembly injection molding of the mesoscale plastic hinge. The precondition for eliminating adhesive bonding is put forward, and the approach of acquiring the clearance required for rotation of the mesoscale plastic hinge is analyzed. It is inferred that whether adhesion of plastic parts appears depends on the heat transferred from the later molded plastic part to the earlier molded plastic part. And the clearance between plastic parts is decided by shrinkage of both the plastic micro pin and the plastic micro hole.Secondly, the structure of the mesoscale plastic hinge is optimized to make it more suitable for injection molding by in-mold assembly technology. Then the molding process is analyzed, and the molding sequence of making the plastic micro hole before the plastic micro pin is chosen.Thirdly, based on the theoretical analyses, the mold for assembly of the mesoscale plastic hinge by using the single cylinder injection molding machine is worked out. This mould makes multi-stage injection molding become possible on the single cylinder injection molding machine, and effevtively protects the very thin core from bending under the high pressure of the polymer melt that flows into the mold cavity with high speed.Finally, the experiments for in-mold assembly of the mesoscale plastic hinge are carried out with HDPE and PP. The experimental results show that the mesoscale plastic hinge can be successfully molded by both single kind of polymer and multi kinds of polymers as long as the precondition for no adhesive bonding is meeted. Meanwhile, the injection pressure of the later molding stage has significant influence on shapes of the plastic micro pin and the plastic micro hole. With higher injection pressure of the later molding stage, tapers of the plastic micro pin and the plastic micro hole become bigger, and the clearance between the plastic parts becomes smaller even minus to form interference fit that makes the plastic hinge can not move freely. Moreover, it is not a good idea to pursue lower temperature of polymer melt at later molding stage, because lower temprature of polymer melt needs higher injection pressure which would bring undesirable influence.更多还原