摘要
注射成型的冷却过程对最终成型制品的质量、性能起着至关重要的作用。而温度是注塑冷却过程中最重要的工艺参数,不合理的温度和温度分布会使产品产生缺陷,并影响生产的效率。因此,如何准确地对冷却过程进行分析就显得极为重要。然而以往人们在研究注塑成型的冷却过程时,往往认为模具和制品在冷却过程中完全接触。实际上,高温的聚合物熔体在冷却时会产生收缩,造成注塑件的体积减小,模具型腔表面和注塑件之间就会出现一个间隙,这样在冷却时,模具和注塑件介面处就会形成接触热阻(TCR),如果忽略接触热阻,就会对热传导过程的分析产生影响,造成结果的不准确。本文在处理此问题时,借鉴了材料边界的思想,将注塑件和模具看成是一个整体,假设两者之间完全接触,但是要考虑接触热阻的影响。本文在基于传热学基本知识的情况下,推导了平板塑件一维瞬态热传导方程解析解,得到了冷却时间的表达式,接着将其扩展到简单的二维、三维情况。然后通过对注塑冷却过程的具体分析,推导出了冷却过程的三维热传导温度场数学模型的控制方程,并运用有限元方法进行分析。最后用具体实例进行模拟分析,结果表明：在考虑了接触热阻后,制品的冷却时间明显增加,而且,注塑件越薄,其影响程度越大。
The cooling process plays an important role in the quality and performance of the products in injection molding, The temperature is the most important process parameters in injection cooling process. Temperature and temperature distribution which is unreasonable may cause product defects and influence productivity. Therefore, how to accurately analyze the cooling process becomes extremely important. However, when people research the cooling process of injection molding in the past, they often thought that molds and products were close contact in the cooling process. In fact, polymer melt which was very hot will shrink while it is cooling. Resulting in reduced volume of injection molded part, a gap will be produced between the cavity and the surface of the part. The thermal contact resistance (TCR) will appear in the interface of the mold and the part when they were cooled. It will impact on the analysis results if the thermal contact resistance is ignored. In this paper,,The auther considered the part and mold as a whole while dealing with this issue and presumed that the part and mold was close contact all the time, but the thermal contact resistance was not ignored. In this paper, using the basic knowledge of the heat transfer, one-dimensional analytical solution of transient heat conduction equation was obtained when deal with the cooling question of a flat plastic parts.It also obtained the formula of the cooling time of the problem. Then it was extended to a simple two-dimensional, three-dimensional case. Furthermore, on the analysis of injection molding cooling process, control equation of three-dimensional mathematical model about the cooling process was derived. Finally, examples of simulation analysis shows that, the cooling process in the mold temperature changes while considering the thermal contact resistance. The cooling time was increased when TCR was existed. It also find that it was more serious when the thinner part was cooled.
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