With the increasing requirement of injection moulding accuracy, besides the correct selection of materials and modification, it is very important to choose the right conditions and analyze the relationship between shrinkage rate and production, especially shrinkage rate, which seriously affects the quality of products. There are many factors that affect the quality of products.

1.Shrinkage of injection moulding

Resin pressure has a great influence on the shrinkage of metal injection moulding. If the resin pressure is high, the shrinkage decreases and the size of the product is large. Even in the same mold cavity, the resin pressure varies with the shape of the product, resulting in shrinkage difference. In the case of multi-cavity dies, the resin pressure in each cavity is prone to be different, and the shrinkage of each cavity is also different.

2.Temperature of die.

Whether it is non-crystalline resin or crystalline resin, if the die temperature is high, the shrinkage rate will increase. Precision moulding should keep the mould temperature at a certain temperature. In die design, attention must be paid to the design of cooling circuit.

3.Generally speaking, the shrinkage rate changes when the gate cross-section area is changed. The shrinkage decreases with the increase of gate size, which is related to the fluidity of resin.

4.Thickness of product wall.

The thickness of the product wall also affects the yield. For non-crystalline resins, the shrinkage of wall thickness is different because of the influence of resin on the shrinkage of wall thickness. The shrinkage of non-crystalline resins is larger than that of non-crystalline resins. On the contrary, the shrinkage of non-crystalline resins decreases. For crystalline resins, it is necessary to avoid a particularly large change in wall thickness. In the case of multi-cavity mode, if the wall thickness of the cavity is different, the shrinkage rate will also be different.

5. Reinforcement material content.

The shrinkage rate of metal injection moulding in flow direction is smaller than that in transverse direction. According to the difference of resin, in order to prevent distortion and warpage, it is necessary to consider gate shape, gate location and gate number.

Injection Moulding Process

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