Cracking often occurs in the molding process of plastic mold, which is a common defect of plastic products. The main reason is the stress deformation. There are mainly residual stress, external stress and stress deformation caused by external environment. Let's talk about the causes of cracking and the corresponding solutions:

塑料制品产生龟裂现象

Cracking of plastic products

一、残余应力引起的龟裂：

1、 Cracking caused by residual stress:

残余应力主要由以下三种情况，即充填过剩、脱模推出和金属镶嵌件造成的。作为在充填过剩的情况下产生的龟裂，其方法主要可在以下几方面入手：

The residual stress is mainly caused by the following three conditions: excess filling, ejection and metal inlay. As the crazing in the case of excess filling, the solution can be carried out in the following aspects:

1、由于直浇口压力损失小，所以，如果龟裂主要产生在直浇口附近，则可考虑改用多点分布点浇口、侧浇口及柄形浇口方式；

1. Because the pressure loss of the straight gate is the least, if the crack mainly occurs near the straight gate, the multi-point gate, side gate and handle gate can be used;

2、在保证树脂不分解、不劣化的前提下，适当提高树脂温度可以降低熔融粘度，提高流动性，同时也可以降低注射压力，以减小应力；

2. On the premise that the resin does not decompose and deteriorate, properly increasing the resin temperature can reduce the melt viscosity, improve the fluidity, and reduce the injection pressure to reduce the stress;

3、—般情况下，模温较低时容易产生应力，应适当提高温度，但当注射速度较高时，即使模温低一些，也可减低应力的产生；

 

3. In general, the stress is easy to occur when the mold temperature is low, so the temperature should be increased appropriately. However, when the injection speed is high, even if the mold temperature is lower, the stress can be reduced;

4、注射和保压时间过长也会产生应力，将其适当缩短或进行Th次保压切换效果较好；

4. If the injection time and holding time are too long, the stress will be produced. It is better to shorten the injection time or carry out th time pressure maintaining switch;

5、非结晶性树脂，如AS树脂、ABS树脂、PMMA树脂等较结晶性树脂如聚乙烯、聚甲醛等容易产生残余应力.

5. Non crystalline resin, such as as as resin, ABS resin, PMMA resin, is easier to produce residual stress than crystalline resin such as polyethylene and polyoxymethylene

二、外部应力引起的龟裂：

2、 Cracking caused by external stress:

这里的外部应力，主要是因设计不合理而造成应力集中，特別是在尖角处更需注意。

The external stress is mainly caused by the unreasonable design, especially at the sharp corner.

三、外部环境引起的龟裂：

3、 Cracking caused by external environment:

化学药品、吸潮引起的水降解，以及再生料的过多使用都会使物性劣化，产生龟裂。

Chemicals, water degradation caused by moisture absorption, and excessive use of recycled materials will lead to deterioration of physical properties and cracking.