4 defense methods for common problems in die casting production(1)

The defense method of the mold often encounters the problems of the pouring system, the overflow system, the horizontal runner, the gate and the overflow groove in the die casting production.
       Gating system, overflow system
       ① The inner diameter of the pressure chamber should be selected according to the required specific pressure and the fullness of the pressure chamber. At the same time, the deviation of the inner diameter of the gate sleeve should be appropriately enlarged by a few wires compared with the deviation of the inner diameter of the pressure chamber, so that the gate sleeve and the pressure can be avoided. The different diameters of the inside diameter cause the jamming or serious wear of the punch, and the wall thickness of the gate sleeve should not be too thin. The length of the gate sleeve should generally be shorter than the delivery stroke of the injection punch in order to allow the paint to escape from the pressure chamber.
      ② The inner hole of the pressure chamber and the gate sleeve should be finely ground after heat treatment, and then ground along the axis direction. The surface roughness is ≤Ra0.2μm.
      ③ The depth of the diverter and the cavity forming the paint is equal to the depth of the runner. Its diameter is matched with the inner diameter of the gate sleeve, and it has a 5 ° slope along the demolding direction. When using a coating-in-type sprue, the volume of the effective length of the pressure chamber is shortened, which can increase the fullness of the pressure chamber.
      2. Requirements for the mold runner
      ① The entrance of the horizontal runner of the cold horizontal mold should generally be located at more than 2/3 of the inner diameter of the upper part of the pressure chamber, so as to prevent the metal liquid in the pressure chamber from entering the horizontal gate prematurely under the action of gravity and starting to solidify in advance.
      ② The cross-sectional area of ​​the runner should be gradually reduced from the runner to the gate. In order to increase the cross-section, a negative pressure will appear when the metal liquid flows through it, which will easily inhale the gas on the parting surface and increase the liquid flow The eddy currents envelop gas. Generally the cross section at the exit is 10-30% smaller than the entrance.
     ③ The runner should have a certain length and depth. The purpose of maintaining a certain length is to stabilize the flow and guide. If the depth is not enough, the temperature of the metal liquid will fall quickly; if the depth is too deep, the condensation will be too slow, which will affect the productivity and increase the amount of regrind.
    ④ The cross-sectional area of ​​the runner should be larger than the cross-sectional area of ​​the gate to ensure the speed of the metal injection. The cross-sectional area of ​​the main runner should be greater than the cross-sectional area of ​​each branch runner.
    ⑤ Both sides of the bottom of the runner should be rounded to avoid early cracks, and the sides can be inclined about 5 °. The surface roughness of the runner area is ≤Ra0.4 μm.