Problems and solutions for brittle cracking in plastic processing of electronic products

During the injection molding process of electronic product shells, brittle cracking is a common problem that may be caused by a variety of factors. The following are analysis and improvement suggestions for molds, equipment, raw materials, processes and product design.

1. Mold aspect

1. Gate size: If the gate is too small, consider adjusting the gate size or adding auxiliary gates to ensure that the molten plastic can be smoothly injected into the mold.

2. Runner design: If the runner is too small or improperly configured, the layout of the runner should be reasonably arranged to ensure flow balance, and the size of the runner should be increased if necessary.

3. Mold structure: Poor mold structure may lead to abnormal injection cycle, and the mold design should be checked and optimized.

2. Equipment aspect

1. Obstacles in the barrel: There are dead corners or obstacles inside the barrel, which are easy to cause molten material degradation and need to be cleaned and maintained regularly.

2. Plasticizing capacity: If the plasticizing capacity of the machine is too small, the plastic will not be fully plasticized in the barrel; on the contrary, if the capacity is too large, the plastic will be heated and sheared for too long, resulting in aging and brittle cracking.

3. Ejector: If the ejector is tilted or unbalanced, the ejector cross-sectional area is small or improperly distributed, it may affect the quality of the product.

III. Raw materials

1. Raw material impurities: impurities mixed in the raw materials, or improper or excessive solvents and additives, will affect the performance of the final product.

2. Moisture-affected plastics: Some plastics (such as ABS) will undergo catalytic cracking reactions with water vapor when heated under humid conditions, resulting in severe strain of the parts.

3. Recycled material problems: Too many regeneration times or too high recycled material content, or too long heating time in the barrel, will cause brittle cracking of the parts.

4. Plastic quality: The quality of the plastic itself is poor, such as large molecular weight distribution, too many non-uniform structural components such as rigid molecular chains, or contamination by other plastics, additives and impurities, which will cause brittle cracking.

4. Process

1. Temperature adjustment: When the barrel and nozzle temperatures are too low, the temperature should be appropriately increased. If the material is easy to degrade, the barrel and nozzle temperatures should be increased.

2. Back pressure and speed: Reduce the back pressure and speed of the screw pre-molding to make the material slightly loose and reduce degradation caused by shear overheating.

3. Mold temperature: Too high mold temperature will make demolding difficult; too low mold temperature will cause the plastic to cool prematurely, the weld seam will not be well fused, and it will be easy to crack, especially for high melting point plastics such as polycarbonate.

4. Demolding slope: The cavity and core should have an appropriate demolding slope. If the core is difficult to demold, the cavity temperature should be increased to shorten the cooling time; if the cavity is difficult to eject, the temperature should be lowered and the cooling time should be extended.

5. Use of metal inserts: Minimize the use of metal inserts, especially for brittle materials such as polystyrene, and avoid adding inserts.

5. Product design

1. Stress concentration: When designing products, avoid sharp corners, notches or areas with large thickness differences, as these areas are prone to stress cracking.

2. Design thickness: If the product is designed to be too thin or too hollow, it may lead to insufficient strength and increase the risk of brittle cracking.

As a manufacturer specializing in electronic product shell processing, it is crucial to understand and deal with brittle cracking. By optimizing mold design, equipment debugging, raw material selection, process parameters and product design, we can effectively improve product quality and ensure the performance and reliability of the final product.