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济南注塑模具加工的收缩现象

来源:http://www.sdlqmj.com 日期:2020-11-25 发布人:liqiang 浏览次数:
热塑性塑料的特性是在加热后膨胀,冷却后收缩,当然加压以后体积也将缩小。在注塑成形过程中,首先将熔融塑料注射入模具型腔内,充填结束后熔料冷却固化,从塑料模具中取出塑件时即出现收缩,此收缩称为成形收缩;塑件从模具取出到稳定这一段时间内,尺寸仍会出现微小的变化,一种变化是继续收缩,此收缩称为后收缩。
Thermoplastics are characterized by expansion after heating, shrinkage after cooling and, of course, volume reduction after pressure. In the process of injection molding, the molten plastic is first injected into the mold cavity. After filling, the molten material cools and solidifies. When the plastic part is taken out of the plastic mold, it will shrink, which is called forming shrinkage. During the period from the removal of the plastic part to its stability, the size of the plastic part will still change slightly, one of which is continuous shrinkage, which is called post shrinkage.
塑料模具注塑加工时,在塑料模具部件较厚位置,如筋肋或突起处形成的收缩要比邻近位置更严重,这是由于较厚区域的冷却速度要比周围区域慢得多。冷却速度不同导致连接面处形成凹陷,即为人们所熟悉的收缩痕。这种缺陷严重限制了塑料模具注塑生产产品的设计和成型,影响加工生产品质,并因此降低生产合格率,尤其是大型厚壁制品如电视机的斜面机壳和显示器外壳等。
In the process of plastic mold injection molding, the shrinkage formed in the thicker part of the plastic mold, such as rib or protuberance, is more serious than that in the adjacent position, because the cooling rate of the thicker area is much slower than that of the surrounding area. The different cooling rate leads to the formation of depression at the joint surface, which is known as shrinkage mark. This kind of defect seriously limits the design and molding of plastic mold injection products, affects the quality of processing and production, and therefore reduces the qualified rate of production, especially for large thick wall products such as inclined surface case of TV set and display shell.
事实上,对于日用电器这一类要求严格的产品上需完全消除收缩痕,而对于玩具等一些表面质量要求不高的产品允许有收缩痕的存在。
In fact, it is necessary to completely eliminate the shrinkage marks on the products with strict requirements for daily electrical appliances, while for toys and other products with low surface quality requirements, shrinkage marks are allowed to exist.
针对这种现象,需要从加工方法、部件几何形状、材料的选择以及塑料模具设计等多种环节进行考量,调整填充压力和时间等加工条件是解决收缩问题的一种方法。
In order to solve this problem, it is necessary to consider the processing method, the geometry of parts, the selection of materials and the design of plastic mold. One way to solve the shrinkage problem is to adjust the processing conditions such as filling pressure and time.

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