Hot Chamber Die Casting & Cold Chamber Die Casting

Hot Chamber Die Casting & Cold Chamber Die Casting

 Die Casting 

           Die casting is commonly used for permanent moulding process. In Die casting the molten metal is injected into a permanent metallic mould under high pressure and held under pressure during solidification. This high pressure, forces the metal into intricate details, produces smooth surface and excellent dimensional accuracy. Die casting operations are carried out in special die casting machines.

There are two main types of die casting machines.

• Hot Chamber Die casting

• Cold Chamber Die casting.

 Application, Advantages & Disadvantages of Die Casting 

Application of Die Casting:

• Used for small and medium castings.

• Used for low melting point non-ferrous alloys.

Advantages of Die Casting:

• Large number of identical parts can be quickly produced

• High finish & close dimensions.

• Very complex shapes, can be casted.

• Superior mechanical properties.

• Thin sections are obtained.

Disadvantages of Die Casting:

• High tooling cost.

• Metals of high melting point are not suitable

• Size is limited.

• No flexibility of processing.

 Hot chamber Die Casting 

Hot Chamber Die Casting Operated by Plunger:

           The molten metal for casting is placed in the holding furnace at the required temperature adjacent to the machine.[sometimes as part of the machine itself]. The injection mechanism is placed within the holding furnace and most of its part is in constant touch with the molten metal. When pressure is transmitted by the injection piston, the metal is forced through the goose-neck into the die. On the return stroke, the metal is drawn towards the goose-neck for the next shot. This process ensures minimum contact between air and the metal to be injected. The tendency for entrainment of air in the metal during injection also minimized. The hot-chamber process is applicable only for low melting point metals like zinc, tin, lead. Also this process limited to some metals that does not chemically attach the metal pots cylinder and plungers.

Hot Chamber Die Casting Operated by Compressed Air:

           The molten metal is forced by air. The air pressure is about 4.2 MPa. The goose neck is lowered. The molten metal enters into goose neck. It is raised up. The compressed air is blown. The molten metal passes into die cavity. After solidification casting is ejected. Low melting alloys like lead and tin are casted.

 Cold Chamber Die Casting 

Cold Chamber Die Casting Process:

           The difference of this process with the hot-chamber process is that the injection system is not submerged in molten metal. In cold chamber process the molten metal is poured into the piston sleeve by manually or automatically. The metal is pushed into die by a hydraulically operated plunger. After solidification the plunger is withdrawn and ready for next shot. Cold chamber machines are typically used for casting aluminum, brass, and magnesium alloys. Compared to hot chamber cycle rate, this process is not usually as fast because of the external source of molten metal.

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