High Pressure Die Casting

To enhance our aluminum casting capability, Dolin Casting started high pressure die casting in 2002. By now, we have 9 die casting machines ranging from 125-ton to 1650-ton. Our products covers automotive parts, medical devices parts, electrical enclosures/housings, lighting fixture parts, heat sinks, hardware tool parts, etc., with the weight ranging from 20G to 20KG. Our yield reaches to 1 ton each day.

Mold is as known as ‘the mother of industry’. The quality of die castings is closely related to the molds in designing, material selection, standard parts selection, heat treatment, accuracy of machining and assembly. We have established strategic partnership with several qualified mold venders nearby our foundry, who regard us as their priority and give us full support in terms of quality, costs, lead time and after-sale service. To ensure the mold quality, we also have our own mold engineers who work closely with our mold venders to monitor every single step of mold manufacturing.

Pressure die casting covers high die cating and low pressure die casting. When people mention die casting, it usually refers to high pressure die casting.

The high pressure die casting process, developed in the early 1900s, is a further example of permanent-mold casting.Typical parts made by this process are motor housings, engine blocks, business-machine and appliance components, hand tools, and toys. The weight of most castings ranges from less than 100g to about 25kg. Equipment costs, particularly the cost of dies, are somewhat high, but labor costs are generally low, because the process is now semi or fully automated. Die casting is economical for large production runs.

In this process, the molten metal is forced into the die cavity at pressure ranging from 0.7 to 700MPa. There are two basic types of die casting machines: hot-chamber and cold-chamber.

The hot-chamber process involves the use of piston, which traps a certain volume of molten metal and forces it into die cavity through a gooseneck and nozzle. Pressure range up to 35MPa with an average of about 15MPa. The metal is held under pressure until it solidifies in the die. To improve die life and to aid in rapid metal cooling (thereby reducing cycle time) dies usually are cooled by circulating water or oil through various passageways in the die block. Low-melting-point alloys (such as zinc, magnesium, tin, and lead) commonly are cast using the process. Cycle time usually range from 200 to 300 shots (individual injections) per hours for zinc, although very small components such as zipper teeth can be cast at rates of 18,000 shot per hour.

In the cold-chamber process, molten metal is poured into the injection cylinder (shot chamber). The chamber is not heated, hence the term cold chamber. The metal is forced into the die cavity at pressure usually ranging from 20 to 70MPa, although they may be as high as 150MPa.

The machines may be horizontal (as in the figure) or vertical, in which case the shot chamber is vertical. High-melting-point alloys of aluminium, magnesium, and copper normally are cast using this method, although other metals (including ferrous metals) also can be cast. Molten-metal temperatures start at about 600 degree Celsius for aluminium and some magnesium alloys, and increase considerably for copper-based and iron-based alloys.

• Mold Manufacturing
  High pressure die casting mold consists of mold base and mold core, and the structure is the most complicated among the permanent mold casting processes. That’s why the manufacturing cycle is so time-consuming. Besides, the die has to withstand both repeat thermal shock and repeat high pressure. That requires the mold material with even higher mechanical properties. Typically, the die casting mold core is made of H13, SKD61, etc.
• Metal Smelting
  Metal smelting is carried out by utilizing smelting furnace to smelt metal alloy. The aim of smelting process is to get pure molten metal alloy with qualified chemical property and right pouring temperature.

• High efficiency — High efficiency is what an aluminum casting company is always pursuing, unfortunately it’s time-consuming to manufacture a die. But once the die has been done, it will be efficient to produce thousands or even millions of identical parts with little machining work, as die casting process has achieved full automation in mass production.
• High quality — Parts produced by die casting process are with some excellent characteristics as tight tolerance, smooth surface, good mechanical properties.
• Economical —It’s possible to produce thousands to millions of castings with only one die, while it’s unimaginable with sand casting or gravity die casting. That makes the cost of die casting parts are lower relatively.
• This process can be simulated—With the assistance of simulation software, the possible die casting defects will be intuitively presented to die designers. This will help designers to optimize the die designing and thus save time and money.

• Long Mold Manufacturing Cycle — It’s time-consuming to manufacture die casting mold.
• Higher Cost of Mold — Die casting mold cost is higher than other casting process, which makes die casting process only suitable for big run production.
• Application limitation — Die casting process only suitable for non-ferrous metal instead of ferrous metal.