Classification of injection molding defects

Classification of injection molding defects

Injection molding process is a complex process involving materials, molds, injection machines, molding processes and other factors. Defects of injection molded products are inevitable. Therefore, it is particularly important to seek the internal mechanism of defects and predict the location and types of possible defects, which can be used to guide mold design and formulate more reasonable process operation conditions.

1. Injection molding and its working process
The injection molding machine is mainly composed of clamping system, injection system, heating and cooling system, hydraulic system, lubrication system, electric control system, safety protection and monitoring system. The injection cycle is mainly composed of procedures such as mold closing, forward movement of injection seat, injection pressure maintaining, pre plastic metering, cooling, mold opening, ejection of products, etc.
Injection molding process is a complex process involving materials, molds, injection machines, molding processes and other factors. Defects of injection molded products are inevitable. Therefore, it is particularly important to seek the internal mechanism of defects and predict the location and types of possible defects, which can be used to guide mold design and formulate more reasonable process operation conditions.

2. Typical defects of injection molding

Generally speaking, there are three aspects to evaluate the performance of plastic products:
Appearance quality, including integrity, color, luster, etc;
Accuracy between size and relative position, i.e. size accuracy and position accuracy;
Mechanical properties, chemical properties, electrical properties, etc. corresponding to the purpose, i.e. functionality.
Therefore, if there is a problem in any of the above three aspects, it will lead to the generation and expansion of product defects.

3. Classification
According to the above three evaluation criteria, the common defects of injection molded products can be divided into two categories:
Appearance problems: including under injection, flash, filling imbalance, shrinkage mark, shrinkage cavity, fusion mark, wave flow mark, spray mark, gate halo, coke mark, bubble, crazing, color difference, whitening, cracking, surface floating fiber, warping deformation, etc;
Performance problems: embrittlement, residual stress, dimensional instability, overweight and underweight, i.e. poor weight repetition accuracy, etc.