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The Difference Between Die Casting Molds & Plastic Injection Molds

The Difference Between Die Casting Molds & Plastic Injection Molds

  • 2021-11-15

The difference between die-casting molds and plastic injection molds

Plastic mold is an abbreviation for a combined plastic mold like compression molding, extrusion molding, injection molding, blow molding and low foam molding.

The die-casting mold is a method of casting liquid die forging, a process performed on a dedicated die-casting die forging machine.

The difference between plastic injection molds and die-casting molds are as follows :

1. To design the plastic injection mold design needs to consider the shrink according to the shrinkage rate of different materials, and the die-casting mold has no shrinkage basically basically , the size of the mold cavity is the same with the product;

2. The injection pressure of the die-casting mold is large, so the template requirements are relatively thicker to prevent the deformation.

3. The gate of the die-casting mold is different from the injection mold, and the high pressure of the split cone decomposition flow is required;

4. Molding process inconsistent , the speed of die casting tools injection is very fast, with only one  section of injection pressure, plastic mold is usually divided into several injections, pressure holding ;

5. The plastic mold is generally vented by ejector pins, the parting surface, etc., however the die-casting mold must be opened with a venting groove and a slag collecting bag (collecting a cold material head);

6. The die-casting mold opens the mold as two plate at a time. The plastic molds differ according to the different product structures. The three-plate mold is common, and the number of times of opening and the order are matched with the mold structure;

7. The parting surface of the die-casting mold has higher requirements, because the fluidity of the alloy is much better than that of the plastic. It is very dangerous if the high-temperature and high-pressure stream fly out from the parting surface.

8. Die-casting molds do not need quenching, because the temperature in the cavity is normally exceeds 700 degrees during die-casting process, so each molding is equivalent to the quenching once, the cavity will become harder and harder, and the general plastic mold should be quenched to above hardness of HRC52;

9. Comparing with the plastic mold, the movable matching part of the die-casting mold (such as the core-pulling slider) has larger clearance because the high temperature of the die-casting process causes thermal expansion, and if the gap is too small, the mold may stuck.

10. The strength of die casting products is better than that of plastic parts, but like the plastic parts, the wall thickness should be even. BOSS column thickness is 1.2MM.

There is no need to add ribs on the top, but the bottom must be added with an R angle, and the corner should also be added with an R angle.

In addition, the plastic injection molds and die-casting molds are different in the steel use as well,  plastic molds are generally manufactured with steel 45#, 718H, S136 and other steels, and the die casting temperature is high (about 670 degrees), the mold material with higher cooling requirements, generally use 3Cr2W8V, 8407, DAC55, SKD61 heat-resistant steel.

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