What is the reason for the brittleness of injection molded products?

The brittleness of some injection molded products is caused by internal stress. Generally speaking, we analyze the reasons for the brittleness of injection molded products from the following aspects.

1: Selected molding equipment

(1) There are obstacles in the barrel of the injection molding machine, which can easily cause melt degradation.

(2) If the plasticizing capacity of the injection molding machine is too small, the plasticization in the barrel is insufficient; if the plasticizing capacity of the machine is too large, the heating and shearing time of the plastic in the barrel is too long, the plastic is easy to age, and the product is brittle.

(3) The ejector device of the injection molding machine is unbalanced, and the cross-sectional area of ​​the ejector pin becomes smaller.

Two: Mold aspect

(1) The gate of the injection mold is very small, and it is necessary to consider adjusting the gate size or adding an auxiliary gate.

(2) The runner is too small, try to balance it reasonably or increase the size of the runner.

(3) Poor mold structure leads to abnormal injection cycle.

Three: injection process

(1) The barrel and nozzle temperature are too low. If you want to improve, you need to increase the injection temperature.

(2) Reduce the pre-plastic back pressure and rotational speed of the screw to reduce plastic degradation caused by shear overheating.

(3) The plastic mold should have an appropriate draft angle. When it is difficult to demould, the cavity temperature should be increased and the cooling time should be shortened.

Four: Design of plastic products

(1) The product has sharp corners with stress cracks, gaps or large thickness differences.

(2) The product design is too thin or too hollow.

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