Two molds for die casting; one called "cover half mold" […]
Two molds for die casting; one called "cover half mold" and the other called "top mold half". Where they meet is called a lane line. The cover mold comprises a runner or an orifice which allows the molten metal to flow into the mold; the feature is matched with the ejection chamber in the ejector nozzle or the cold chamber machine on the hot chamber machine. The injector mold comprises a top pin, typically a flow path, which is a path from the gate or the injection hole to the mold cavity. The cover mold is fixed to the fixed or front platen of the casting machine while the injector mold is attached to the movable platen. The mold cavity is cut into two cavity inserts, which are separators which can be relatively easily replaced and inserted into the mold halves, respectively.
The mold is designed such that the finished casting will slide out of the lid half of the mold and remain in the ejector half as the mold is opened. This ensures that the casting is ejected on each cycle because the ejector consists of a thimble and the casting is pushed out of the mold. There must be enough thimble to keep the overall strength on each pin low because the casting is still hot and may be damaged by excessive force. These needles still leave traces, so they must be located where these marks do not hinder the purpose of the casting.
Other mold components include cores and sliders. There are three types of cores: fixed, movable and loose. The fixed cores are cores oriented in parallel with the direction of pulling of the mold so that they are fixed or permanently attached to the mold. The movable core is a core oriented in any other manner parallel to the pulling direction. After the injection is solidified, but before the mold is opened, a separate mechanism is used which must be removed from the mold cavity. These vents are usually wide and thin, so when the molten metal begins to fill them, the metal quickly solidifies and minimizes the waste. Do not use riser, because high pressure ensures continuous entry from the gate into the metal.
The most important material properties for the dies are thermal shock resistance and softening at elevated temperature; other important properties include heat checking resistance, weld ability, availability, and cost. The longevity of a die is directly dependent on the temperature of the molten metal and the cycle time. The dies used in die casting are usually made out of hardened tool steels, because cast iron cannot withstand the high pressures involved, therefore the dies are very expensive, resulting in high start-up costs. Metals that are cast at higher temperatures require dies made from higher alloy steels.