Aluminum pour- All about die casting

What Is High and Low-Pressure Die Casting?

What is Die Casting?

Die casting is a type of metal casting that uses the process of forcing molten metal into two steel dies that make up a cast. Die casting is typically used in a high-volume production setting and is known for producing a high-quality, consistent product. The equipment used for the die casting process typically has a higher initial cost compared to processes that use sand molds. However, the day-to-day cost of manufacturing using die casting tends to be on the lower end, producing a lower cost per item.

History of Die Casting

The die casting process was originally devised in 1838 to create “movable type” machines (think of a giant stamp with movable letters). The first patent related to the die casting process was eventually received in 1849 about 20 years later. When die casting equipment became available to the North American market the applicable uses spread as well. In the 1900s, a mixture of tin and lead were used for die casting and would go through several different trends before the use of aluminum became the best option.

Modern Methods

Low-pressure die casting is performed using a vertical process that shoots the molten metal upward against gravity. The metal travels from the furnace below by a piston using low pressure through a shot chamber into the two molds. The two molds are made of aluminum alloys; one is fixed while the other is able to be pulled away to let the casting free itself from the mold once cooled. The pressure is maintained in the mold while the metal cools to ensure an even and accurate fill. As the metal cools, further molten metal can be added to fill any missed or shrinking cavities. The only downside to low-pressure is the slower casting cycle, however, this die casting process is a cheaper, less-complicated technology as compared to high-pressure die casting, and lends itself to automation.

Pros: 

  • Good strength values
  • No complicated machinery and die technology
  • High material utilization, No feeders needed
  • Well-suited for automation 
  • High dimensional accuracy

Cons: 

  • Slow casting cycles
  • Has a minimum wall thickness of 3mm (in die)

High-pressure die casting is the new craze when it comes to this method of metal casting. As opposed to low-pressure die casting, high-pressure die casting has a shorter casting cycle and utilizes a horizontal casting process instead of vertical. High-pressure die casting is created by two machine plates on either side that lock together to create a mold in the middle, like a die casting sandwich. The molten metal is pushed through the chamber with a piston at high speed and high pressure to fill the mold. Once the metal has solidified, the die is opened and the casting removed. Because of the expensive nature of the machine and its dies, high-pressure die casting should be reserved for high-volume production runs.

Pros:

  • Short casting cycles
  • Good for thin-walled components
  • Smooth surfaces
  • Good for automation

Cons: 

  • Complicated and expensive dies
  • Lower strength values
  • Die-cast weight limited by the locking force of the machine

While this new trend speeds up the process, there are a few drawbacks to using high-pressure die casting. High-pressure die casting is a big investment while low-pressure die casting is a cheaper option. The process is also limited to smaller parts as the locking mechanism can only handle up to a certain weight. However, this has prompted the ability to make stronger castings of lesser weight using aluminum alloy, a change that has brought great benefits to other industries looking to minimize the weight of their cast parts and components, including automotive, aviation, electronics, and general hardware.

Why Choose Vibratory For Die Casting?

After the die casting process, castings are moved for further processing or checked for quality. In some cases, if the standards are not met the casting will be sent back to the furnace to be melted and recreated. This process requires a system of vibratory conveyors and feeders to move the castings where they need to go.

Why is vibratory better? Belt conveyors simply cannot handle as much volume and wear quickly, while vibratory conveyors and feeders can handle larger castings and scrap without being damaged or melting from the heat. General Kinematics offers a wide range of die casting equipment, including the V-TROUGH® Vibratory Inclined Conveyor, TRENCHVEYOR™, and TWO-WAY™ Vibratory Feeders. Each of our pieces of equipment is customizable to fit your needs.

To learn more about what vibratory equipment can do to fit your die casting needs, call today and talk to a GK engineer!

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