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What should I do if there are cold spots in the gate area of injection molded products?

Mar 28, 2018

Plaque mainly refers to the smears with fog or bright color near the gate of the part or the curved scars from the gate that resemble the squeaky scars on the top. They are caused by plastic forwards entering the cavity or by excessive pressure retention. It was caused by the cold material that was later squeezed into the cavity.

The scutt material transfers heat due to the cooling effect of the nozzle or runner, and is cooled and solidified before entering the cavity. When the cavity is expanded and injected into the cavity through a narrow gate, a melt fracture occurs, followed by subsequent heat. The molten material pushed and it became a cold spot.


1. Cold wells should be well opened. Also consider the form, size, and location on the gate to prevent material cooling speeds from varying.

2. The center of the nozzle should be adjusted well. The fitting size between the nozzle and the mold should be designed to prevent leakage or cause cold material to be brought into the cavity.

3. Mold exhaust is good. Gas interference can cause turbid markings on the gate.

4. Increase the mold temperature. Slow down the injection speed, increase the injection pressure, reduce the holding pressure and injection time, and reduce the holding pressure.

5. Dry the plastic. Use less lubricant to prevent the powder from being contaminated.