Bemould Plastic News

We will periodically update Bemould's latest updates, sharing our work experience with all the person in need ,and to answer the most common topics and questions that come up when working on new plastic part designs.

Injection molding defects : Clod flow lines

 Tuesday, 24 August 2021

Cold flow lines, also known as sun spot and fog spot, refers to the circular color change near the gate, which is usually determined by the pouring method and gate size. The reason is melt fracture

1.Causes ,Too much injection pressure ,The mold temperature is too low, which will cool the plastic too fast, resulting in too much cold material, and then rush to the product surface . The gate setting is unbalanced, the gate is too small or the cavity at the glue inlet is too thin, the material flow is large and the cross-sectional area is small. High shear rate will cause melt rupture and gate halo, resulting in flow marks, color change, fog spots and other defects.
2.optimization scheme Molding process:

reduce the injection speed, injection pressure, increase the mold melt temperature and mold temperature to improve the fluidity of the material.

As for mold: reasonable gate size, reduce material flow resistance and reasonable cold well design.

For example, the gate cold flow lines of new energy power equipment accessories, non appearance parts and products started in the morning is obvious , as the running time of the machine increases, the mold temperature and material temperature of the machine rise gradually, and the defect will be improved slowly.

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