All About High Pressure Die Casting

By Author: Ryan
Total Articles: 8
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For components of different sizes and shapes, high-pressure die casting (HPDC) is a high-volume manufacturing process and there are some specifics of the process which can be discussed. Within several milliseconds the casting of a molten alloy into a mold is complete. Therefore with high production rates, a significant quenching effect is possible.


Because of the application of high-pressure casting like zinc die casting there is good contact between molten alloy and die wall that enables: heat transfer coefficient at the die-melt interfaces the increase in cooling rate, the increase in heat flow and as well as the formation of a net shape casting.


During solidification casting defects such as shrink holes which are generated by the shrinkage are reduced. Directly from the liquid state, components with complicated shapes are produced even for a molten alloy with high viscosity. By taking these facts into account, it is expected that by the high pressure die casting process in various alloy systems much larger shapes and ...
... dimensions can be formed.


The characteristics of the HPDC process are the high solidification rate of the component and high velocity of melt during filling the die. During the HPDC process, such circumstances demand a more sophisticated approach to the study of phenomena.


For the production of complex, thin-walled near net shape castings, with part weights ranging from a few grams to more than 15kg, HPDC is a fully automatic, large volume, high productivity process. In the production of housings etc., it has traditionally been utilized, but this has been changed. Presently, in magnesium alloys and B-pillars in aluminum alloys, feasible products are automotive front end structures and instrument panels.


Aluminum, copper-base alloys, zinc, and magnesium are the four principal metals, with different alloy compositions, that are commonly hot-or cold chamber die cast. In the hot chamber machines, the injection system is immersed into the melt and the pressure is therefore limited. If exposed to aluminum the system also degrades quickly. The metal reservoir is separated from the injection system in the cold chamber process.


In HPDC a Production Cycle Consists of:

The casting is then ejected. By a computerized system, the hydraulic energy is provided that permits pressure during filling and solidification, control of metal position, velocity, and plunger acceleration to optimize the flow.


The die is Opened


During the solidification process, by the plunger to feed the solidification shrinkage the casting is pressurized hydraulically. To withstand the large pressures Locking forces up to 4000 tons are commercially available.


Plunger Movement

Metering of metal into the shot sleeve

During die filling the die cavity may be evacuated to reduce air entrapment, and by utilizing vacuum systems high integrity die castings from zinc die casting manufacturer can therefore be produced. Alternatively to reduce turbulence semi-solid metalworking (SSM) can be used. It results in fine grain size which provides decent mechanical properties. However, by the intimate interrelationship between product and process design, the properties can be improved.