Determination Of The Cross-sectional Area Of The Inner Gates
The cross-sectional area of the gates directly determines the inner gates' speed and filling time.
When the inner gates speed is selected, if the cross-sectional area of the inner gates, If the cross-sectional area of the gate is too large, the metal liquid fills the cavity too fast, so that the gas in the cavity is not discharged in time to produce pores and other die casting defects.
If the cross-sectional area of the inner gates is too tiny, it prolongs the filling time, and in the filling process, part of the metal liquid cools too fast, resulting in the cavity filling is not satisfied with the phenomenon.
In order to obtain the ideal filling time, the inner gates cross-sectional area remains unchanged, adjust the action on the liquid metal pressure and pressure injection punch speed, can also change the liquid metal filling time, but the adjustment range is minimal, in addition, to consider the bearing capacity of the die-casting machine.
Therefore, in the design process, predetermine the inner gates' cross-sectional area is a critical design content.
At present, in die casting practice, is the metal liquid at a certain speed and predetermined time to fill the cavity is the primary basis of calculation.
Design Of The Thickness Of The Inner Gates
In the inner gates cross-sectional area, the thickness of the inner gates has a more significant impact on the formation of a good filling flow state. Therefore, it is appropriate for thin-walled complex die castings to use thin inner gates to ensure the necessary speed of the inner gates. However, when the inner gate thickness is too thin, the metal liquid flow of tiny impurities, such as segregation, inclusions, oxides, and other impurities, will lead to local blockage of the inner gates, reducing the effective flow area of the inner gates.
At the same time, the metal liquid entering the cavity is easy to produce an atomization phenomenon, thus blocking the exhaust channel, and then wrap the gas in the cavity to produce die casting defects.
When the thickness of the inner gates is thicker, it helps to reduce the filling speed. At the same time, the inner gate's solidification time is the almost quadratic increase in the thickness of the inner gates, which is conducive to the transfer of the complementary shrinkage pressure. Therefore, without affecting the surface of die casting without increasing the cost of removing the inner gates, the thickness of the inner gates can be increased as much as possible.
The width of the inner gates should also be selected appropriately, and the width is too large or too small will cause the metal liquid to rush straight to the opposite side of the wall, resulting in vortex flow to wrap the air and impurities and produce scrap. The length of the inner gates directly affects the quality of the casting.
If the inner gates are too long, it will affect the pressure transfer, cooling, and casting surface will be easy to form a cold partition pattern.
If the inner gates are too short, the temperature at the inlet will rise quickly and speed up the wear of the inner gate, and it is easy to produce a spraying phenomenon.
Key Points For The Design Of The Position Of The Inner Gates
When designing the inner gates, the most crucial thing is determining the inner gates' location, form, and direction. According to the shape and structure characteristics of die casting, wall thickness change, shrinkage deformation, and mold parting surface, and other factors, the flow pattern and filling speed change of metal liquid in the filling, as well as the expected filling process, may appear in the dead corner area, wrapped gas and complex partition parts, and arrange the appropriate overflow and exhaust system.
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