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Why is the draft angle of die castings important?

2022-07-03 10:33:13

                                                           Why is the draft angle of die castings important?

The draft angle of die casting process refers to the taper or slope in the vertical direction of the casting. The surface of the die casting piece perpendicular to the parting line of the die needs to be drawn, so that the die casting piece can easily come out of the core or cavity.

The shrinkage stress of die castings in the process of molding cooling and shrinkage die casting causes the castings to stick to the mold core and generates demoulding resistance in the process of demoulding the castings from the mold. In order to reduce the resistance of demoulding from the castings, it is easier to pull out the cores and prevent the surfaces of castings and cores from being scratched due to friction caused by relative movement. In short, the mold release slope of die casting must be the same as the mold release direction on the side of the casting.

How to design draft angle?
1) Considering the problem of wall thickness, excessive thickness difference will affect the filling;

2) Considering the problem of demoulding is very important in die casting practice. In reality, such problems often occur, which is much more annoying than injection molding demoulding, so attention should be paid to the setting of draft angle and the calculation of demoulding force of medium dynamic fixed mold. Generally, the draft angle is 1 to 3 degrees. Generally, considering the smoothness of demoulding, the external draft angle is smaller than the internal draft angle, the external draft angle is 1 degree, and the internal draft angle is about 2 to 3 degrees;
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3) When designing the mold, consider the problem of mold design. If there are multiple positions of the core pulling position, try to put it on both sides, and it is best not to put it on the lower position. In this way, the lower core pulling will be easy to cause problems after a long time;

4) Some die castings may have special requirements for appearance, such as oil injection, powder spraying, etc. at this time, the structure should avoid important appearance positions to facilitate the setting of gate overflow grooves;

5) In the structure, try to avoid the structure that leads to the complex structure of the mold, such as having to use multiple core pulling or spiral core pulling, etc

6) For the parts that need surface machining, pay attention to the appropriate machining allowance in the part design, not too much, otherwise the machining personnel will scold you, and the pores inside will be exposed, not too little, otherwise after rough and fine positioning and machining, the black skin has not dried out, you will wait to spark on the mold. How much is it, and the allowance should not be greater than 0.8mm, There are basically no pores on the processed surface, because it is protected by a hard layer.

7) Another thing is to pay attention to the selection of materials. Whether to use ADC12 or A380 depends on the specific requirements

8) Aluminum alloy has no elasticity, and it can only be matched with plastic to make buckle

9) Generally, deep holes cannot be made! Only make some holes when opening the mold, and then process it later

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