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The Secrets Behind Pressure Die Casting

by Nice Rapid | Aug 05,2022 | Pressure Die Casting

Pressure die casting is a permanent mold manufacturing procedure created in the early 20th century that uses increasing pressure to send molten metal through a mold. This manufacturing procedure can produce castings with excellent surface detail and the best dimensional accuracy along thin walls as low as half an inch, thanks to the extreme pressure.

Pressure die casting has a wide range of presentations regarding sizes. You can get products that are nearly weightless to something commanding heftier builds. All parts created with this procedure require heavy tooling, and it’s the best way to develop specific products such as machinery parts, carburetors, motors, housing parts, and even toys.

Pressure die casting parts

How does it work?

With pressure die casting, molten metal is heated in a casting machine. These casting machines, called gooseneck, have a built-in furnace able to heat metal until it has a liquid state. This procedure uses hydraulic-powered pistons to force the metal from the furnace into the die. It’s a die casting process that is carried out relatively quickly since the hot chamber pressure die casting process is used for applications requiring large outputs.

There’s a cold chamber casting alternative. Molten metal must be poured into the chamber manually using ladles or automatic ladle systems. Once the metal has been poured, hydraulic pistons force the metal into the die using high pressure. In this process, the casting machines don’t heat any metal.

Materials Used in Pressure Die Casting

For pressure die casting, machining manufacturers recommend material with low melting points. This ensures metals won’t be dissolved or eroded when heated or placed under high pressure. Machine parts like plungers are always under molten metal. If the metal has a high melting point, it causes damage to the plunger and loses functionality, which warrants costly replacements.

Materials such as aluminum have high melting points at 1,220 F° when compared to zinc, which melts at 786 degrees. Aluminum is not the best you can use for Pressure die casting. The most suitable materials for these procedures are zinc or various magnesium alloys.

Pressure Die Casting Step-by-Step

It all begins when the hot chamber is filled up with liquid metal. A shot cylinder powering the injection stroke is located over the metal supply. This shot cylinder connects to a plunger and makes contact with the molten material. At the beginning of a casting cycle, the plunger is placed on top of the hot chamber; in this position, liquid metal can be poured using intake ports to fill them up.

After the plunger goes down, the cycle starts- The shot cylinder brings down and pushes the plunger, making it go past the intake ports to prevent the liquid metal from going into the hot chamber. Once the right amount of metal gets inside the hot chamber and fills the mold, pressure can be applied to make the casting.

When the plunger gets pushed down further, this forces the liquid metal inside the die. With Pressure die casting, the pressure exerted on the molten metal to fill the die needs to range from 700 to 5,000 pounds psi. The pressure must be held for as long as is required to get the casting to solidify.

After the final form is solid, the plunger goes back to its original position, and then it gets ready to begin the cycle anew. Once the plunger reverses and to its original position at the top of the hot chamber, the intake ports are exposed to allow more molten metal to come in and fill up the enclosure.

Advantages of Pressure Die Casting

Pressure die casting works pretty well, one of the most important benefits being the faster build cycle. This gives die casting companies the opening to create more products in less time, which translates into more efficiency, productivity, and client satisfaction. More benefits attached to this manufacturing method include diminished loss of raw materials, increased efficiency thanks to the machine containing, and using internal melting pots. You also get reduced porosity and extended machinery life since only low-melting-point metals are used.

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