Gravity Die Casting vs. Sand Casting for Aluminum Parts

When metal parts have a requirement of excellent corrosion resistance and light weight, aluminum alloy is a good option to consider. Casting of aluminum alloys can creat complicated products with good strength.

Gravity Die Casting and sand casting are the two aluminum casting methods to produce parts by pouring aluminum alloys into molds. Although both methods has a long history, they have been refined over the years to improve the quality and production volume. But there still exists differences between these two methods of making aluminum parts. Now, let’s look at these two processes in below.

Gravity Die Casting

Gravity Die Casting vs. Sand Casting for Aluminum Parts

Gravity die casting is a casting process used for aluminum parts, sometimes referred to as Permanent Mould Casting.

In gravity die casting, the molten aluminum alloy is poured into channels in the tool to allow the material to fill the entire mold cavity. The metal is either dosed or hand poured by using ladles.
After solification of the metals, the die is opened by either using a mechanical tool or manually to get out of the solid parts.

In CFS Foundry, commonly applied aluminum alloy in gravity die casting process is A356 aluminum alloy. Gravity die casting is the ideal process for maufacturing aluminum castings when there is a requirement of high volume production with consistent accuracy.

Sand Casting

Sand casting is another casting process to produce aluminum parts. Aluminum sand casting is the process of pouring molten aluminum alloy into a mold cavity formed in sand. There are really only two basic requirements: that the sand has a cavity in the shape of the object you wish to cast, and that there is a channel you can pour metal into that will lead to the cavity.

In sand casting, the molds are created by compacting sand—most often mixed with clay as a bonding agent and moistened with water—around a pattern or model of the final product. The mold is split apart and the pattern removed. The two halves of the mold are put back together and the void is filled with molten metal. Once the metal cools sufficiently, the mold is opened, the sand removed, and the part taken out.

Sand Casting is an excellent solution for low to medium runs of aluminum parts that do not require precise shape repeatability, as well as being the only solution for very large objects which cannot be produced with gravity die casting or pressure die casting techniques.

Advantages of Gravity Die Casting Over Sand Casting

Unlike sand casting, the mold is made from steel, allowing for one or more cavities depending on the geometry of the part. The process is best suited for mid to higher volumes, when the part configuration dictates this type of casting, or the process is best suited for the application of the casting. The molds are in, most cases, fully CNC machined with the parting surfaces aligned with a locking system that provides good repeatable casting dimension conditions.

When compared to sand castings, gravity die casting have below advantages:

  • Good dimensional accuracy and less machining allowances required
  • A smoother cast surface finish than sand casting
  • Improved mechanical properties, especially higher strength, compared to sand casting.
  • High production effeciency compared to sand casting process.

Any inquiry on gravity die casting process for your aluminum items, pls feel free to contact our foundry!

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