Cracking defects caused by residual stress during injection molding

1. Overfilling

Overfilling may result in uneven compression and stretching of the material within the mold, resulting in residual stress. Therefore, the following measures can be taken:

Because the pressure loss of the direct gate is the smallest, if the crack is mainly produced near the direct gate, it can be considered to use the multi-point distribution gate, side gate and handle gate.

On the premise of ensuring that the resin does not decompose and degrade, appropriately raising the resin temperature can reduce the melting viscosity, improve the fluidity, and ensure that the material is evenly cooled in the mold. It can also reduce the injection pressure to reduce the stress.

When the die temperature is low, it is easy to produce stress, so the temperature should be raised appropriately. However, when the injection speed is higher, the stress generation can be reduced even if the mold temperature is lower.

Injection and pressure retention time is too long will also produce stress, and it is better to shorten or switch the pressure retention time appropriately.

Non-crystalline resins, such as AS resin, ABS resin, PMMA resin and other crystalline resins such as polyethylene, polyformaldehyde are easy to produce residual stress, which should be paid attention to.

2. Drelease out and mold design

The design and structure of the injection molding tool will directly affect the flow and cooling of materials during the molding process. If the design is not reasonable, it may produce excessive thermal stress and strain in the molding process, thus leading to cracking. Due to the small slope of the release, the rough mold glue and convex mold, the push force is too large, producing stress, and sometimes even the whitening or rupture phenomenon around the push rod. Therefore, it is necessary to ensure that the mold design and structure are reasonable to reduce the flow resistance and inhomogeneity of the material during the molding process.

3. Embedded metal parts

When the metal parts are embedded in injection molding, the stress is generated due to the difference of the thermal expansion coefficient between the metal and the resin, which may produce residual stress in the cooling process, which may lead to cracking after a long time, causing great harm. The wall thickness and the outer diameter of the embedded metal parts are basically not suitable for the inlay, and the inlay has the least impact on nylon. Because of the thermal expansion coefficient of glass fiber reinforced resin material is small, it is more suitable for embedded parts. The metal insert before molding also has a good effect.

4. Material properties

If the strength and toughness indexes of the injection material do not meet the requirements, or the thermal stability is poor, it may produce excessive residual stress during the molding process, leading to cracking. Therefore, the injection materials with excellent strength and toughness and good thermal stability should be selected.

5. condition of molding

If the injection and pressure retention time is too long, and the mold temperature is not appropriate, the residual stress may also occur in the molding process. Therefore, it is necessary to shorten the injection and pressure retention time, and avoid the stress concentration caused by too long pressure retention time. Timely conduct pressure retaining switch to reduce residual stress.

Finally, allow me to introduce our factory, a leading manufacturer specializing in Injection Molding Machine , Injection molds, and Injection Molding Auxiliary Equipment.

Our Injection molding machine is designed for precision and efficiency, ensuring high-quality outputs in every production cycle.Coupled with our Auxiliary machine , Injection Machine Electric Motor, Injection Machine Nozzle . They enhance the overall performance of the molding process, our solutions are tailored to boost productivity and reduce downtime. Additionally, our Injection Mold is precision-crafted to ensure consistency and accuracy in the finished products.

We also offer Recycled Plastic Raw Material such as PET, PP, PVC, PS, PA, PE ,ABS pellets. To ensure precise and consistent results, we offer a wide selection of Mold Temperature Control Machines. These machines play a crucial role in regulating mold temperatures, ensuring optimal conditions for the molding process and enhancing the quality of finished products.

Our High Precision Injection Mold is precision-crafted to exacting specifications, ensuring that every detail of the finished product meets the highest standards of quality and accuracy.We offer a wide range of special injection molding machines such as: Water Pail Injection Molding Machine, Fruit Box Injection Molding Machine, Mobile Phone Case Injection Molding Machine,Garbage Can Injection Molding Machine, Injection Molding Machine for Needles, Chair Injection Molding Machine and Basket Injection Molding Machine cater to the needs of our customs, providing them with efficient and cost-effective solutions for mass production.

Injection molding machine Plastic Products cover a number of industry areas: Automobile manufacturing, electronic and electrical industry, packaging industry, daily necessities manufacturing, medical device manufacturing, construction industry, furniture manufacturing, sports and outdoor equipment, aerospace, textile and clothing industry, wire and cable industry, agriculture and horticulture, environmental protection and sustainable development, with the continuous progress of technology and the expansion of the market, the application field of injection molding machine will continue to expand.

Whether you're looking to upgrade your existing equipment or establish a new production line, we have the perfect solution for you. Contact us today to learn more.