Plastic Mold Manufacturer: How to Deal with Plastic Cracking

The issue of cracking in plastic molded products has always been one of the common defects in the injection molding process. The occurrence of cracking is often due to a combination of multiple factors. To address the problem of plastic cracking, it is essential to thoroughly understand the root causes and take appropriate corrective actions. This article will focus on the three main causes of cracking in plastic molded products and their solutions.

1. Residual stress is one of the primary causes of cracking in plastic molded products. Residual stress mainly arises from excessive filling, mold release, and metal inserts. To tackle cracking caused by excessive filling, the following measures can be considered: First, consider switching to multi-point distribution gates, side gates, and gate styles to reduce cracking near the direct gate. Secondly, under the premise of ensuring resin quality, appropriately raising the resin temperature can reduce melt viscosity and improve flow, thereby decreasing stress. Additionally, increasing mold temperature and shortening injection holding time are also effective ways to reduce stress generation.

2. External stress is another significant cause of cracking in plastic molded products. External stress is primarily caused by unreasonable design leading to stress concentration, especially at sharp corners where problems are more likely to occur. Designing product structures reasonably, avoiding excessively small sharp corners, and using appropriate R/7 ratios can effectively reduce cracking due to external stress.

3. External environmental factors can also impact the cracking of plastic molded products. Chemical agents, moisture-induced hydrolysis, and excessive use of recycled material may lead to a deterioration of the physical properties of plastic, resulting in cracking. When embedding metal components during the injection molding process, stress can easily develop, and over time, if the stress exceeds the strength limits of the resin material, cracks may form. Therefore, during the design phase, it is important to avoid significant differences in thermal expansion coefficients between metal components and resin, and to select appropriate material combinations to prevent cracking.

To resolve cracking issues in plastic molded products, a comprehensive analysis of the causes is necessary, along with targeted corrective actions. By reasonably adjusting process parameters, optimizing product design, and selecting appropriate material combinations, it is possible to effectively prevent and address cracking in plastic molded products, thereby improving product quality and production efficiency.