The common problems encountered in die-casting production include:

1. Pouring system, overflow system

(1) Requirements for the sprue of the die-casting mold on the cold chamber horizontal die-casting machine:

① The inner diameter size of the pressure chamber should be selected based on the required specific pressure and chamber filling degree. At the same time, the inner diameter deviation of the gate sleeve should be appropriately enlarged by a few threads compared to the inner diameter deviation of the pressure chamber, so as to avoid the problem of punch jamming or severe wear caused by the different axes of the gate sleeve and chamber inner diameter, and the wall thickness of the gate sleeve should not be too thin. The length of the gate sleeve should generally be less than the delivery lead of the injection punch to facilitate the release of the coating from the pressure chamber.

② The inner holes of the pressure chamber and gate sleeve should be finely ground after heat treatment, and then ground along the axis direction, with a surface roughness of ≤ Ra0.2 μ M.

③ The splitter and the concave cavity that forms the coating have a concave depth equal to the depth of the transverse gate, and its diameter matches the inner diameter of the gate sleeve, with a slope of 5 ° along the demolding direction. When using a coating guide type sprue, the volume of the effective length of the pressure chamber is shortened, which can improve the filling degree of the pressure chamber.

(2) Requirements for the transverse runner of die-casting molds

① The entrance of the transverse sprue of the cold horizontal die casting mold should generally be located at the upper part of the pressure chamber with an inner diameter of more than 2/3, in order to prevent the metal liquid in the pressure chamber from entering the transverse sprue prematurely under the action of gravity and starting solidification earlier.

② The cross-sectional area of the transverse sprue should gradually decrease from the vertical sprue to the inner sprue. In order to expand the cross-sectional area, negative pressure will occur when the metal liquid flows through, which is easy to absorb gas on the parting surface and increase the vortex entrapment in the metal liquid flow. The cross-section at the outlet is generally 10-30% smaller than that at the inlet.

③ The transverse sprue should have a certain length and depth. The purpose of maintaining a certain length is to stabilize and guide the flow. If the depth is not enough, the metal liquid will cool down quickly. If the depth is too deep, the condensation will be too slow, which not only affects productivity but also increases the amount of return material used.

④ The cross-sectional area of the transverse gate should be greater than the cross-sectional area of the inner gate to ensure the speed of metal liquid entering the mold. The cross-sectional area of the main runner should be greater than the cross-sectional area of each branch runner.

⑤ The bottom sides of the transverse runner should be rounded to avoid early cracks, and a slope of about 5 ° can be made on both sides. The surface roughness of the transverse runner is ≤ Ra0.4 μ M.

(3) Inner gate

① After the metal liquid enters the mold, the parting surface should not be immediately closed, and the overflow groove and exhaust groove should not directly impact the core. The flow direction of the molten metal after injection into the mold should be as close as possible to the ribs and heat dissipation fins that are cast in, and should be filled from thick walls to thin walls.

② When selecting the position of the inner gate, try to keep the metal flow as short as possible. When using multiple internal gates, it is necessary to prevent the merging and mutual impact of several strands of molten metal after injection, resulting in defects such as eddy current aeration and oxidation inclusions.

③ The thickness of the inner gate of thin-walled parts should be appropriately smaller to ensure the necessary filling speed. The setting of the inner gate should be easy to cut and not cause defects (meat eating) in the casting body.

(4) Overflow tank

① The overflow groove should be easy to remove from the casting and try not to damage the casting body as much as possible.

② When opening an exhaust groove on the overflow groove, it is necessary to pay attention to the position of the overflow port to avoid premature blockage of the exhaust groove, making it ineffective.

③ Multiple overflow ports or a very wide and thick one should not be opened on the same overflow channel

Compiled from an academic library for reference in learning.

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