文档介绍：成型不良- BS(黑点)-Black Spec
何谓黑点(外观)?What is Black spec ? (appearance)
黑点是指成型品中出现黑色的点或条纹的现象。
成型品表面上出现的黑色的点便是BS(黑点)。由于某些原因,其成分估计是焦化树脂或碳化树脂。
BS is a molding defect where (a) black point(s) or line(s) appears on the surface of a molded product.
黑点的生成原因Causes of Black spec Generation
position of resin由于塑料是化学物质,因此当在熔点以上继续加热时,塑料便会逐渐分解。温度越高,时间越长,分解就进行得越快。而且机筒内部还有止逆环和螺纹槽等容易滞留树脂的部位。持续滞留在这些部分的树脂发生焦化或碳化后会按某种节奏脱落并混入到成型品中,从而形成黑点。Since a plastics is a chemical substance, it poses little by little on heating over the melting point. position proceeds as temperature is increased and time is prolonged. Inside the cylinder there are places where resin is likely to stagnate such as check ring and screw grooves. When the stagnation continues, the resin is changed to tar or is carbonized. If this es off by any chance and is mixed in a molded product, it es BS.
・清洗不足
(2-2) Shortage of purging
因清洗不充分而使以前使用的树脂残留在成型机内的情况也是黑点的生成原因。如上一项所述,由于存在止逆环和螺纹槽等容易滞留树脂的部位,因此对该部分进行置换时需要使用相应的清洗量和次数,此外还必须采用适合每种材料的清洗方法。如果是PBT→PBT等同类树脂的清洗,则比较容易进行,但如果是不同种类的材料的清洗,则由于熔点或分解温度各不相同并且树脂之间也存在相容性(亲和性),因此即使清洗,很多情况下也无法完全排出。When purging is insufficient and the resin used before remains in a molding machine, the remaining resin es a cause of BS. As described above, there are parts where resin is likely to stagnate such as check ring and screw grooves, and the replacement of these parts requires a certain level of purging quantity