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After the product is produced, cracks appear, including surface filamentous cracks, micro cracks, top whitening, and product loss. According to the cracking time, demolding cracks and application cracks are mainly caused by the following aspects.

① In terms of processing

Increased processing pressure, too fast speed, excessive injection of materials, and prolonged holding time can all cause excessive internal stress and cracking

2. Adjust the mold opening speed and pressure to prevent rapid and forceful pulling of the product from causing demolding cracking.

3. Adjust the mold temperature appropriately to make the product easy to demold, and adjust the material temperature appropriately to prevent decomposition.

4. Prevent cracking due to reduced mechanical strength caused by fusion marks and plastic degradation.

5. Use release agents appropriately and pay attention to regularly eliminating substances such as mist attached to the film surface.

② In terms of molds

1. The ejection should be balanced, with sufficient number and cross-sectional area of ejector rods, sufficient demolding inclined ejection, and smooth enough cavity surface to prevent cracking due to residual stress concentration caused by external forces.

2. The product structure should not be too thin, and the transition department should use transitions as much as possible to avoid stress concentration caused by sharp corners and chamfers.

3. Minimize the use of metal inserts to prevent increased internal stress caused by different shrinkage rates between the inserts and the product.

4. The main channel is sufficient to facilitate demolding of the sprue material before it can solidify.

③ Machine aspect

The plasticizing capacity of the injection molding machine should be appropriate. If the plasticizing capacity is too small, it will not be fully mixed and become brittle. If it is too large, it will degrade.