In a hot chamber, die casting is placed directly in the molten bath. The part of the channel (metal line) located above the level of the melt is additionally heated by gas or electricity. At the same time, the melt jet does not freeze and easily flows through the metal wire and the die into the metal mold, which is especially important in the production of castings from zinc and tin-lead alloys with a low pouring temperature.
Operating principle
The melt is poured into a cast-iron crucible; to maintain a constant temperature, the crucible is heated from below. The melt in the upper position of the piston through the hole fills the channel and the cavity of the cylinder. Before pouring the melt, the mold is closed and the end of the mouthpiece enters the channel, connecting the cavity of the mold with the channel.
When the cylinder is automatically turned on, the piston descends, presses on the melt in the cylinder, and displaces it from the channel into the mold cavity. After the casting has solidified, the piston is lifted, the mold is opened, and the solidified casting is pushed out of the mold. Then the mold is blown and the working cycle of the machine is repeated again.
What about performance
The productivity of semi-automatic machines is up to 250, and of automatic machines – up to 1,000 castings per hour when servicing several machines by one person. Working pressure in different designs of machines ranges from 10 to 75 atm.
The main disadvantage of the hot chamber die casting machines is the rapid wear of the piston pair under conditions of a high melt temperature (about 500 C). The machine is designed for the manufacture of parts from zinc-based alloys in mass and large-scale production.
The main units: bed, pressing and locking mechanisms, oven, fencing, cooling unit, lubrication mechanism, hydraulic unit, electrical equipment. All units are located on the bed or inside it. The electrical cabinet is installed separately from the machine. The general layout of the machine is made in such a way that the bed is unloaded from all the forces arising in the locking and pressing mechanisms. The machine adopts the lower position of the pressing chamber relative to the casting and the center of the plate.
The hydraulic lever mechanism for locking the molds during the injection of the melt is adjusted to the required height of the mold using a jack located between two movable plates. The hot bale chamber enables the machine to operate in automatic mode.
The pressing mechanism provides a stepped pressing speed and a high final pressure on the melt after filling the mold, helping to remove air from the mold cavity and increase the density of the casting.
The casting is pushed out by a hydraulic pusher located in the movable plate. The manifold allows you to adjust the intensity of the water cooling of the pressing plunger, the mold (at four points), and the stationary plate. The discharge of water from each point can be observed visually.
The safety of working on the machine is ensured by interlocks that prevent incorrect activation of mechanisms, a protective door on the working side of the machine, and a cover around the locking mechanism. Push-button control, automatic mode of operation in combination with rational placement of controls and main service points minimizes the fatigue of the caster, which allows him to service several machines at once.
