Whatever machine is used by the manufacturers, it is necessary that accurate procedures must be used to securely lock in place the casting; this includes the die halves, the cores, and other moveable sections during the casting cycle. Usually the clamping force of the machine is determined by the surface area of the casting needed which is measured by the parting line of the die, and the pressure needed to inject the right amount of metal into the die. Most of these machines use toggle type mechanisms actuated by hydraulic cylinders to achieve the perfect locking. Other machines use air pressures generated from other parts of the machine while others use direct acting hydraulic pressure which is different than the normal hydraulic pressure itself. There are safety interlock mechanisms in place to prevent the opening of the die during the die castings cycle.
Whatever the die casting machine used, whether it is big or small, varies fundamentally on how the molten material is injection into the die. There are two main machines used in diecasting, these are usually called hot or cold chamber machines.
To elaborate, this is what happens in the machine:
The Hot Chamber Machines
These machines are primarily used for zinc and other alloys that have low melting points and do not erode or attack other metal pots, plungers, and cylinders needed in the casting. Other technologies and more advanced equipment materials are used for magnesium alloys since they require higher temperatures and sophisticated methods of casting.
In the unique method of casting in hot chamber machines, the injection mechanisms immerse the molten metal in a furnace which is attached to the machine. As the plunger moves down, it seals the port and then forces the molten metal to go through the gooseneck nozzle and then into the die castings.
Although there are many processes that happen inside the hot chamber machines, still, cycle times are still short ranging from one second to thirty seconds depending on the several pounds of casting that is manufactured.
The Cold Chamber Machines
The way cold chamber machines differ from hot chamber machines is the way the injection plunger and cylinders not being submerged in the molten metal. In this process, the molten metal is poured through a port or pouring slot by automatic or robotic hands or ladles. The plunger which is hydraulically operated advances forward and then seals the port forcing the molten metal to lock with the die at high pressures. It requires around 3,000 to 10,000 psi for alloys of aluminum and magnesium to be properly casted. The operation in cold chamber machines are slower than hot chambers; this means lesser alloys are produced in cold chamber machines during diecasting. This machine normally lasts longer than hot machines due to the non-submersion of the molten metals to the parts of the other parts in the “cold machines”.