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注塑模具冷却时要注意这些问题

来源: 日期:2020-12-09 发布人:liqiang 浏览次数:
塑料注塑模具件的冷却时间很重要,一般占整个注塑生产期的80%,如果冷却时间不当,会导致产品变形或表面缺陷,从而影响产品的性能。
The cooling time of plastic injection molding parts is very important, which generally accounts for 80% of the whole injection molding production period. If the cooling time is improper, it will lead to product deformation or surface defects, which will affect the product performance.
塑料注塑模具冷却时要注意这些问题
Pay attention to these problems when cooling plastic injection mold
制件冷却时间,一般是指塑料熔体自充满注塑模具型腔起到可以开模取出制件时止的这一段时间。可以开模取出制件的时间标准,经常以此制件已经充份固化,具有一定强度与刚性为限,于开模顶出时不至于变形开裂。即便是使用同一一种塑料成型,它的冷却时间亦随壁薄、熔融塑料的温度、成型件的脱模温度以及注塑模具温度而异。要于所有的场合之下能准确地计算出冷反而时间的公式目前未发表,因而只于合适假定的基础之上进行计算的公式。
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The cooling time of parts generally refers to the period from the time when the plastic melt fills the injection mold cavity to the time when the part can be taken out by opening the mold. The time standard for taking out the part by opening the mold is often based on the time standard that the part has been fully solidified, has a certain strength and rigidity, and will not deform and crack when the mold is opened and ejected. Even if the same kind of plastic is used for molding, the cooling time varies with the wall thickness, the temperature of the molten plastic, the demoulding temperature of the molded part and the temperature of the injection mold. The formula for calculating the cold reversal time with 100% accuracy in all cases has not been published, so it is only based on appropriate assumptions.
塑料注塑加工件断面之内的平均温度,冷却到规定制品的出模温度所要的时间,结晶性塑料成型件壁的为薄部分层温度,冷却到其熔点下列所需要的时间,或是达到规定的结晶化百分比所需的时间。成型腔之内的塑料和模腔密切接触,绝不由于冷却收缩因而分离,熔体和模壁栋的热传递与流动无任何阻力,熔料和模壁接触的瞬间其温度已经变得相近。乃如果塑料充入模腔之后,制件表面温度乃等于模壁温度,塑料注塑加工件冷却过程之中,注塑模具型腔表面的温度依旧保持皆一,注塑模具表面的热传导程度一定,(熔料充模过程视为等温过程,而且料温皆一),塑料的取向与热应力对于制件变形的影响可以忽略,制件尺寸对于凝固温度绝不发生影响。
The required cooling time from the injection molding temperature to the center of the mold is the required cooling time of the plastic part to the center of the mold. The plastic in the molding cavity is in close contact with the mold cavity, and will never separate due to cooling shrinkage. There is no resistance to heat transfer and flow between the melt and the mold wall, and the temperature of the melt has become close to the mold wall at the moment of contact. If the surface temperature of the part is equal to the mold wall temperature after the plastic is filled into the mold cavity, the surface temperature of the injection mold cavity remains uniform during the cooling process of the plastic injection molded part, and the degree of heat conduction on the surface of the injection mold is certain (the filling process of the molten material is regarded as an isothermal process, and the material temperature is uniform), The effect of plastic orientation and thermal stress on the deformation of parts can be ignored, and the size of parts has no effect on the solidification temperature.

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