The two types of die casting machines are a hot chamber machine
and cold chamber machine.
Hot chamber die casting machine - Hot chamber machines
are used for alloys with low melting temperatures, such as zinc,
tin, and lead. The temperatures required to melt other alloys
would damage the pump, which is in direct contact with the
molten metal. The metal is contained in an open holding pot
which is placed into a furnace, where it is melted to the
necessary temperature. The molten metal then flows into a shot
chamber through an inlet and a plunger, powered by hydraulic
pressure, forces the molten metal through a gooseneck channel
and into the die. Typical injection pressures for a hot chamber
die casting machine are between 1000 and 5000 psi. After the
molten metal has been injected into the die cavity, the plunger
remains down, holding the pressure while the casting solidifies.
After solidification, the hydraulic system retracts the plunger
and the part can be ejected by the clamping unit. Prior to the
injection of the molten metal, this unit closes and clamps the
two halves of the die. When the die is attached to the die
casting machine, each half is fixed to a large plate, called a
platen. The front half of the die, called the cover die, is
mounted to a stationary platen and aligns with the gooseneck
channel. The rear half of the die, called the ejector die, is
mounted to a movable platen, which slides along the tie bars.
The hydraulically powered clamping unit actuates clamping bars
that push this platen towards the cover die and exert enough
pressure to keep it closed while the molten metal is injected.
Following the solidification of the metal inside the die cavity,
the clamping unit releases the die halves and simultaneously
causes the ejection system to push the casting out of the open
cavity. The die can then be closed for the next injection.
 
Hot
chamber die casting machine - Opened
Hot chamber die casting machine - Closed
Cold chamber die casting machine - Cold chamber machines
are used for alloys with high melting temperatures that can not
be cast in hot chamber machines because they would damage the
pumping system. Such alloys include aluminum, brass, and
magnesium. The molten metal is still contained in an open
holding pot which is placed into a furnace, where it is melted
to the necessary temperature. However, this holding pot is kept
separate from the die casting machine and the molten metal is
ladled from the pot for each casting, rather than being pumped.
The metal is poured from the ladle into the shot chamber through
a pouring hole. The injection system in a cold chamber machine
functions similarly to that of a hot chamber machine, however it
is usually oriented horizontally and does not include a
gooseneck channel. A plunger, powered by hydraulic pressure,
forces the molten metal through the shot chamber and into the
injection sleeve in the die. The typical injection pressures for
a cold chamber die casting machine are between 2000 and 20000
psi. After the molten metal has been injected into the die
cavity, the plunger remains forward, holding the pressure while
the casting solidifies. After solidification, the hydraulic
system retracts the plunger and the part can be ejected by the
clamping unit. The clamping unit and mounting of the dies is
identical to the hot chamber machine. See the above paragraph
for details.
 
Cold chamber die casting
machine - Opened Cold chamber die casting machine - Closed
Machine specifications
Both hot chamber and cold chamber die casting machines are
typically characterized by the tonnage of the clamp force they
provide. The required clamp force is determined by the projected
area of the parts in the die and the pressure with which the
molten metal is injected. Therefore, a larger part will require
a larger clamping force. Also, certain materials that require
high injection pressures may require higher tonnage machines.
The size of the part must also comply with other machine
specifications, such as maximum shot volume, clamp stroke,
minimum mold thickness, and platen size.
Die cast parts can vary greatly in size and therefore require
these measures to cover a very large range. As a result, die
casting machines are designed to each accommodate a small range
of this larger spectrum of values. Sample specifications for
several different hot chamber and cold chamber die casting
machines are given below.
Type Clamp force (ton) Max. shot volume (oz.) Clamp stroke (in.)
Min. mold thickness (in.) Platen size (in.)
Type |
Clamp force
(ton) |
Max. shot
volume (oz.) |
Clamp stroke
(in.) |
Min. mold
thickness (in.) |
Platen size
(in.) |
Hot chamber |
100 |
74 |
11.8 |
5.9 |
25 x 24 |
Hot chamber |
200 |
116 |
15.8 |
9.8 |
29 x 29 |
Hot chamber |
400 |
254 |
21.7 |
11.8 |
38 x 38 |
Cold chamber |
100 |
35 |
11.8 |
5.9 |
23 x 23 |
Cold chamber |
400 |
166 |
21.7 |
11.8 |
38 x 38 |
Cold chamber |
800 |
395 |
30.0 |
15.8 |
55 x 55 |
Cold chamber |
1600 |
1058 |
39.4 |
19.7 |
74 x 79 |
Cold chamber |
2000 |
1517 |
51.2 |
25.6 |
83 x 83 |
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