How Does Sand Casting Work?
The sand cast molding process includes several steps. It is a type of casting-based manufacturing that involves the use of sand to create a mold. This process is used to create metal products in a wide range of shapes and sizes.
The sand casting process starts with the creation of a mold pattern and a gate system. Each pattern requires a new mold designed to the exact size and shape of the intended part. The setup also requires a two-part casting flask, referred to as cope and drag.
The mold pattern is placed in sand and the gate system is set up with a series of tunnels and a pouring cup. After packing sand around the pattern, the pattern is removed, leaving a mold cavity. Metal is then heated to a high temperature, turning the metal into a liquid state. The temperature needed to melt the metal depends on the alloy. Some metal takes longer to heat.
The molten metal is poured into the mold cavity. After the metal is poured into the mold, the metal starts to cool and solidify. To remove the part, the sand mold is separated along a parting line. During this process, the mold cavities are destroyed. However, the mold pattern is typically reusable.
Is Sand Casting Right for Your Product?
Sand molded castings are cost-effective but may not provide the best solution for every product or part. The main advantages of this casting process include:
- Lower costs for low-volume production runs
- Suitability for fabricating large components
- Ability to use ferrous or non-ferrous metals
- Shorter lead time compared to other processes
Using sand to cast metal is the oldest metal casting method and one of the most versatile. One of the most attractive features is that It has the lowest initial setup cost. The process is also easier to modify and reduces the cost of changes to the mold.
Due to these features, this method of casting is ideal for the fabrication of low- to medium-volume production runs, prototype castings, and the conversion of welded components to castings.
What Is Green Sand Casting?
Greensand casting refers to a method involving moist sand for forming the molds. The sand used for this process is not green. It is called “green” due to the moisture but is usually silica sand.
The moisture comes from the clay that is added to the sand. Combining bentonite clay and sand provides a stronger mold as the moisture helps the sand stick together. The sand remains uncured and “green” when the molten metal is poured into the mold.
Air set casting (no-bake casting) and resin sand molding are two other common casting processes. With air set casting, chemical binders are used to bond the molding sand. Heat is not needed for this process.
Using green sand provides cost reductions compared to other casting processes. However, each process has its advantages. For example, the air set casting method allows for a better surface finish and greater consistency compared to green sand. It is also more costly.
Resin sand molding involves a mixture of quartz sand and resin. The mixture creates a hard mold and requires no heating. As with air set casting, resin casting increases costs and production time compared to greensand casting. However, it also produces fewer defects and a smoother finish.
Die Casting vs. Sand Casting
Sand casting is not the only metal casting solution. Die casting is also a viable option for certain parts. Compared to sand casting, die casting may reduce the need for additional tooling.
Die casting also relies on liquid metal. Instead of forming a mold cavity in the sand, a steel mold is created in the size and shape of the product; this mold is also referred to as the “die.” The molten metal is forced into the die. After the metal cools and solidifies, the die may be reused, which allows for a quicker cycle compared to casting with sand.
Possible defects include pores, hot tearing, and surface projections. These defects are often caused by issues with the manufacturing processes. For example, porosity often occurs when the liquid metal is heated too high or the sand has a low permeability.
Raw castings may also require additional finishing. The surface finish often has a rough texture and with die casting, the finish is smoother. The die also allows for more complex shapes.
Sand casting is more cost-effective, especially for low-volume runs. When creating thousands of castings, cost-effectiveness tends to decrease. With die casting, the reusable mold allows for faster production and lower costs, especially when dealing with high-volume orders.
Our Sand Casting Process
We offer a variety of sand casting methods and materials to suit your project, including:
- Greensand molding
- Resin sand molding
- Air set molding
Along with these processes, we offer a complete metallurgical analysis. With our state-of-the-art lab, we can prepare metals for analysis to help reduce casting defects and process inefficiencies.
Our solutions also allow for the use of a wide range of materials including stainless steel, alloy steel, iron, aluminum, magnesium, brass, bronze, and copper. Our equipment includes magma solidification software to reduce or eliminate porosity. We also utilize a coreless induction melting furnace to increase productivity.
Our Sand Casting Equipment
- Magma Solidification Software: Using this software results in better pattern making and gating to reduce or eliminate porosity.
- Coreless Induction Melting Furnace With a fast heat-up time, this combines high productivity with maximum alloy flexibility.
- Channel Holding Furnace: The channel holding furnace combines high productivity with the economical operation and provides a continuous supply of ready-to-pour metal 24 hours a day.
- Automatic Sand Molding Machine: Made with mechanical automation and used for high volume casting, all molds have the same dimensions, tension, moisture content, and other properties.
The Federal Group’s Sand Casting Capabilities
Our capabilities have a wide range from 1 lb to 30,000 lbs per piece. Different materials and methods can be used to achieve the ideal result for your project needs:
Green Sand Molding
Castings are made using sand molds formed containing water and organic bonding compounds (typically clay).
Resin Sand Molding / Shell Molding
Castings are made with resin sand, which is a mixture of quartz sand and resin. Also known as a hard mold, the resin sand becomes very hard and solid after mixing and burning.
No-Bake/Air Set Molding
This sand casting process involves the use of chemical binders to bond the molding sand. Heating is not necessary for this process.
Complete Metallurgical Analysis
- Our state of the art lab is fully capable of preparing metals for analysis.
- Microscopic and Macroscopic Analyses: Sectioning, mounting, polishing, and micro etching are done to prepare the metal for analysis.
- X-Ray Diffraction Analysis: We are also capable of preserving the specimen: This is a nondestructive technique for characterizing crystalline material or minerals.
- Fully Equipped Sand Testing Lab: Capable of testing all of the characteristics of prepared sand for casting, we have maximum control over processes. This identifies casting defects and process inefficiencies, resulting in superior products at a lower cost of operation.
Our Sand Casting Materials
We use the following materials in our sand casting projects.
- Stainless Steel/ Duplex 2205, 2507 & Zeron
- Alloy Steel
- Grey, Ductile & White Iron
- Brass, Bronze & Copper
If you’re interested in getting a quote for your upcoming sand casting project, contact The Federal Group USA today. We’re happy to talk through our processes and any other metal fabrication solutions you may be interested in.
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