Injection Molding Defects Prevention and Remediation
Injection molding is a popular method of manufacturing components and assembled products. Its versatility is a major advantage, as its potential applications include almost any plastic part imaginable. However, there are several common issues that may occur when injection molding parts, including premature plastic degradation, airflow problems, and inadequate cooling. This article discusses these and other injection molding defects, as well as how to prevent and remediate them.
Premature Plastic Degradation
Plastic parts are often made with a variety of different materials, each with its own unique properties. Different resins may be used in the same part, and different types of additives may also be used. These materials and additives can have a significant influence on the properties of the parts and the injection molding process. If the resin is not properly selected and tuned for the part is being molded, premature plastic degradation can occur. This can occur for several reasons, such as inappropriate choice of resin, the use of incompatible additives, and improper drying of the material.
When premature plastic degradation is identified, it must be remedied quickly to avoid irreparable damage. Often, resin selection and proper drying of the materials are enough to prevent this issue. In some cases, additives may be necessary to help reduce the degradation.
Airflow Issues
The injection molding process relies on several steps to ensure successful molding of a part. First, a plastic material is placed into the barrel of an injection molding machine and heated, in order to melt the material. The melted material is then injected into a mold and cooled. During each step of the process, air must flow freely through the material to ensure part quality and integrity.
If airflow is impeded during the injection molding process, several issues may arise. Poor gating of the part, sink marks and warping, gas entrapment, and inadequate cooling all may result. To prevent air flow issues, the material must be heated and purged properly, the barrel must be clean, and the gate must be designed properly. Additionally, a vacuum should be applied to the mold during injection to aid in the evacuation of trapped air.
Inadequate Cooling
Injection molded parts must be cooled in order to maintain the desired shape and structure of the part. Poor cooling of the part can lead to dimensional irregularities, cracking, and warping. To ensure proper cooling, a mold must be properly designed and manufactured. Additionally, the mold temperature, cooling medium temperature, and flow of the cooling medium all must be adequate.
Conclusion
Injection molding is an effective and popular method of manufacturing parts and products. As with any manufacturing process, however, injection molding can have its own set of defects. Defects such as premature plastic degradation, airflow issues, and inadequate cooling all can have a negative effect on the quality of the molded part. By understanding the causes of these defects and taking the necessary steps to prevent or remediate them, it is possible to ensure the success of an injection molding process.
