Choosing Resin Sand Casting: When and Why It’s the Right Process

Sand casting is a metal forming process in which a mold is formed from a 3-dimensional pattern of sand. Molten metal is poured into the mold cavity, and the sand shell is removed after the metal components have cooled and hardened. Some secondary machining processes may be required after casting to improve product accuracy.

Sand casting is excellent for small production runs. It also offers a great deal of versatility in final product design. There are two types of sand which might be used in the sand casting process, either resin sand or green sand. This article looks at when to select the resin sand casting process.

What is Resin Sand Casting?

In resin sand casting, quartz sand is mixed with a resin material. The sand component has very high quartz levels, a very high melting point in the range of 1700° Celsius, and extremely high hardness levels. The grain shape and surface smoothness of the sand are also important factors. These combined characteristics make raw sand well suited for casting purposes.

A chemical reaction created by the resin serves to bind and stiffen the quartz sand, resulting in quite solid, hard, and strong molds. The resin sand can be used to create the entire mold or just a part of the mold. The final mold can create a wide variety of shapes, configurations and sizes. Typical products made with resin sand castings include cylinder blocks, cylinder heads, hydraulic valve bodies, hardware, electrical contact parts, pulleys, gearbox parts, and landing gear components.

What to Consider When Selecting a Sand Casting Process

Engineers and product specifiers work with foundry specialists to determine which type of sand casting process is best for their specific application. Key factors to take into consideration include:

• Strength: This refers to the sand’s ability to hold its shape during the casting process.
• Permeability: The specific physical makeup of the sand in terms of size and shape will determine whether trapped gases will be allowed to vent through it during casting. Using a sand mixture that is more permeable will help to reduce porosity in the molds, but less permeable sand will often result in a higher quality surface finish.
• Thermal stability: As the molten metal is poured into the mold, the sand must be stable enough to resist damage such as cracking from the heat.
• Collapsibility: The casting must be allowed to shrink freely in order to avoid cracking. To accomplish this, the sand must be able to compress as the casting solidifies.
• Reusability: Some sands have the ability to be reused for future projects, such as other sand molds.

When to Choose the Resin Sand Casting Process

Resin sand casting offers the capability of making complex parts in smaller production runs in a very cost-effective manner; however, longer production timeframes might be required. Foundries also have to keep an eye on the cost of the resin, as prices may fluctuate due to global economic factors. Benefits which can be realized from this process, as compared to other casting methods, include:

• Results: Resin sand casting will produce accurate dimensional results that are superior to other sand casting methods. The sand is generally easy to shake off and clean up, resulting in a cleaner end component.
• Surface strength: Resin sand has an increased surface strength which allows it to better retain its shape during the casting process.
• Few defects: With its combined chemical make-up, the molten material can flow into every mold crevice, meeting dimensional specifications and reducing defects such as sand holes, air holes, and shrinkage.
• Sizing: There is much more flexibility in sizing with resin sand casting. Castings can range from a smaller component that requires customization up to a large casting weighing several tons.
• Variety: Because of its tolerance to high temperatures, resin sand casting can be used for a wide variety of metals, such as iron, titanium and nickel alloys.
• Finish: Because of the sand’s collapsibility, the resin sand casting process creates a very smooth mold surface.

Learn More About When to Select the Resin Sand Casting Process

Impro is a leading global manufacturer of complex and high value-added sand castings using the resin sand casting process. Our knowledgeable staff can assist you in selecting from a wide range of casting processes to find the one best suited to your specifications and budget criteria. If you are interested in finding more information about our resin sand casting process and capabilities, please contact our team of experts today.