Mold Requirements For Die Casting

① The inlet of the runner in a cold-pressed horizontal mold should generally be located at least 2/3 of the upper inner diameter of the pressure chamber to prevent molten metal from entering the runner prematurely under gravity and starting solidification early.

② The cross-sectional area of ​​the runner should gradually decrease from the sprue to the ingate. An enlarged cross-section would create negative pressure as the molten metal flows through, easily drawing in gas from the parting surface and increasing vortex entrainment during flow. Generally, the outlet cross-section is 10-30% smaller than the inlet cross-section.

③ The runner should have a certain length and depth. Maintaining a certain length serves to stabilize and guide the flow. Insufficient depth leads to rapid cooling of the molten metal; excessive depth results in slow solidification, affecting productivity and increasing remelted material usage.

④ The cross-sectional area of ​​the runner should be larger than that of the ingate to ensure the speed at which the molten metal enters the mold. The cross-sectional area of ​​the main runner should be larger than that of each branch runner.

⑤ The bottom sides of the sprue should be rounded to prevent early cracking, and the two sides can be sloped at about 5°. The surface roughness of the sprue area should be ≤Ra0.4μm.