Sand casting is a manufacturing process for making metal parts, although it is suitable for making other materials such as glass. It involves a vat of molten metal material into an already prepared sand mold. The sand mold is a hollow cavity shaped like the desired product. On solidification, the molten metal takes the shape of the mold.

Sand casting products come in different shapes, sizes, and weights due to the process compatibility with the complex designs. Furthermore, the process is compatible with several metals, and using sand makes it a cost-effective option. The major cost in many sand casting foundry is incurred during the pattern-making process and the purchase of metal material.

Types of Casting Sand

Type of casting sand
Type of casting sand

The choice of casting sand depends on whether you want to dispose of the sand or not. Common sand for casting includes:

Green Sand

The green sand contains sand (75% to 85%), clay (5% to 11%), water (2% to 4%), and other additives. The clay and water acts as a binding agent. The sand itself is not green in color, with the moisture content being the reason for its “green” tag.

Green sand for casting is suitable for high-volume production and is reusable after casting. However, green sand casting is unsuitable for designs with tight tolerances, and the sand-casted parts need secondary finishing.

Dry Sand

Dry sand contains clay or another binding agent, shaped into a mold, and baked. The sand is suitable for ferrous and non-ferrous parts with intricate designs that require tight tolerance. Hence, its wide application in several sand casting foundry for making parts such as engine blocks and gearboxes. While very popular, dry sand is not reusable.

Resin Sand

Resin sand or furan sand is a mixture of silica sand or other aggregate materials and a synthetic resin binder that creates a stable and robust mold for sand-casted metal parts. Resin sand is stronger and has better dimensional stability, making it more suitable for making parts that need to be accurate and consistent. Furthermore, it has a shorter cure duration time, does not need a secondary finishing option due to lesser surface defects, and the mold is less prone to deformation when pouring the molten material.

Water Glass

This casting sand uses a sodium silicate binder to integrate the sand for mold formation. As a result, it is preferred for parts with intricate and delicate patterns. Mold created using water glass is less resilient in use and handling but is dimensionally stable, low cost, and requires shorter curing time.

Core Sand

This is a blend of silica sand, core oil such as mineral oil or linseed oil, and a binding agent such as dextrin and sodium silicate. It is applicable in making the core due to its compressive strength.

Loam Sand

This casting sand contains water and an equal amount of sand and clay. It is applicable in making big and heavy metal parts. Examples include hoppers and turbine parts.

There are other types of casting sands, each with unique properties and applications. They include the parting sand, backing and floor sand, system sand, and molasses sand. Choosing each one is better done with good research or by a reputable sand-casting service recommendation. At Zintilon, we have experts knowledgeable in sand casting materials to give you a quality product.

How Does Sand Casting Work

How does sand casting work
How does sand casting work

The sand casting process is like the die casting in terms of the use of mold and material. However, it differs in several ways, as highlighted in the steps below.

Pattern Making

The pattern is a reusable part made from wood, metals, plastic polymer, etc. It comes in two halves, with each half having a design that, when they come together, will form the complete product.

There is a slight adjustment in the design to cater to the contraction of the final sand cast part, incorporating metal pathways with the pattern often larger. Furthermore, for easier removal of the pattern, a draft allowance is incorporated, characterized by all surfaces parallel to the pattern removal direction being tapered slightly inward.

Molding and Core Making

The sand casting mold is made by packing the pattern with four components: base sand, binders, additives, and parting compounds. The base sand, such as silica sand, is used to make the mold and the core in its purest form. Binders such as clay and water help hold the sand together, and additives help improve the surface finish, strength, cushioning, or refractoriness. Lastly, the parting compounds can be a liquid or fine powder for easier removal of the pattern.

Like the pattern, sand molds for metal casting have two halves. There is the lower part called the drag and the upper part called the cope. After the sand sets and you remove the pattern, the halves are reassembled and clamped, creating a cavity that forms the product on pouring the molten material. A refractory coating is applied for a better surface finish so that the molten metal does not affect the mold. Furthermore, the mold can contain cores, which produce an internal passageway in the final product.

Melting and pouring

The material is melted using any suitable method. Afterward, the molten material is poured into the mold smoothly and quickly to remove turbulence, which can lead to casting flaws and prevent solidification. Some extremely reactive materials to oxygen need to use a shielding process, such as argon shielding, to prevent air from the molten metal.

Solidification and cooling

On proper solidification of the molten material, shakeout occurs. A shakeout operation involves splitting the sand and removing the metal casting in sand. Depending on the type of casting sand, you can reuse some.

Final processing

Final processing for sand casting products includes machining operations such as honing and grinding for removing the gates, runners, and risers. Furthermore, you can subject the part to heat treatment or other surface finishing options like sandblasting.

Advantages of Sand Casting

A sand casting product
A sand casting product

Sand casting is popular in many industries due to its high-volume production, unlike other methods, such as vacuum casting, known for low-volume production. Other advantages of the process include:

Design flexibility

The sand casting process is suitable for making a part of any dimension and weight. This is crucial in the early development stage where only 1-2 large prototypes are needed. The only restriction to this flexibility is the molten metal handling and supply.

High-complexity shapes

Unlike other casting techniques, sand casting is compatible with parts with highly complex designs and shapes. The hindrance to making a complex part is the pattern. Once a pattern is ready, you can make any type of part.

Wider material choice

The sand casting process is suitable for most engineering alloys so far, they are meltable. It is also suitable for materials such as glass. As a result, there is a wider application.

Low-cost tooling

It has a low tooling cost compared to other manufacturing process such as CNC machining, die casting, etc. As a result, many consider it one of the cheapest manufacturing methods for complex parts.

Short lead time

The sand-casting process has a fast production time, which means a short lead time. Furthermore, there is less waste as the scraps are recyclable.

Disadvantages of Sand Casting

Sand casting products
Sand casting products

Even though it has immense advantages, sand casting comes with several disadvantages. Nevertheless, these disadvantages should not deter your use of the process, especially when you trust reputable sand casting services:

Low dimensional accuracy

Due to material shrinkage during the cooling process, sand casted parts are not dimensionally accurate. As a result, they need a surface finishing process, which can incur extra costs or use an elaborate setup that accounts for the dimensional change.

Poor surface finishes

Sand casted parts are often exposed to surface finishing options because of the internal sand mold wall surface texture.

Defects unavoidable

Since shrinkage, porosity, and other defects are unavoidable, sand casted parts have several design flaws. Furthermore, porosity is higher on sand casting products than die casted products.

Higher risk

The lack of automation in the process makes humans more exposed to safety hazards and environmental problems

Not compatible with Mass Production

Sand casting requires a single mold for a product making it suitable for mass production of parts. Instead, it is a perfect prototyping option during product development.

Common Materials Used in Sand Casting

A sand casting foundry
A sand casting foundry

Sand mold casting is compatible with many materials; however, it is more common for metals. Choosing the right material depends on the casting properties, production volume, etc. The most common materials used in sand casting include:

Aluminum

Aluminum is one of the most common sand-casting materials due to its mechanical properties. It has a high strength-to-weight ratio, low density, corrosion resistance, and castability. Common aluminum sand casting alloys include ADC12, AL6061, and A356. Sand casting aluminum involves working with a base sand such as silica chromite, and chamotte.

Bronze

Bronze is an alloy of copper and tin, a common sand casting material. Sand casting bronze depends on its different alloys based on the percentage of copper and tin or the presence of other elements like aluminum, zinc, nickel, and iron.

Bronze alloys suitable for sand casting include aluminum bronze, manganese bronze, and silicon bronze. Each has its properties. For example, Aluminum and Manganese Bronze are strong, corrosion and wear-resistant, and toughness. Manganese Bronze has corrosion wear resistance and extraordinary mechanical properties. On the other hand, Silicon Bronze has high machinability and castability.

Brass

Brass is an alloy of copper and zinc known for its rust and corrosion resistance due to its elemental content. Furthermore, it does not have any iron or iron oxide. Brass has good conductivity and tensile strength. As a result, it is a very popular sand-casting material for parts that require such properties.

Zinc

Zinc is a strong material with high rigidity, corrosion resistance, and castability. Furthermore, its strength and hardness make it easy to make components with thinner walls when alloyed. Sand casting zinc is easier than aluminum.

Lead

Lead is one of the most popular sand casted materials from the Romans. It is heavy and corrosion-resistant. However, it poses some health dangers, necessitating using them under stringent conditions. Nevertheless, it applies to making small to medium parts like plumbing fittings.

Copper

Copper is a costly, high tensile strength and heavier material known for its electrical and thermal conductivity. Since it does not rust and is highly castable, it is applicable in making sand casted parts like plumbing fixtures.

Iron

Iron is common in sand casting due to its fluidity and low volume/linear shrinkage. However, its poor mechanical properties, characterized by high compressive strength and lesser tensile strength, make it suitable for parts with complex shapes or asymmetric structures. Examples include Gray Iron Castings with excellent castability and machinability, Ductile Iron Castings with good fluidity and large shrinkage, and Malleable Iron with excellent ductility, machinability, toughness, and corrosion resistance.

Mild Steel

Mild steel has a low carbon content (0.15% to 0.30%), hence its high malleability and ductility. It is common due to its low cost and easy castability. However, air holes, shrinkage, and cracks make it difficult to work with the material.

Stainless Steel

Stainless steel’s resistance to corrosion, durability, and strength makes it popular in sand casting. Furthermore, it has a low thermal expansion coefficient, improving its accuracy, high tolerance, and dimensional stability. However, it is an expensive metal, and its high strength and stiffness make it difficult to eject parts from the sand-casting mold.

Typical Applications of Sand Casting

Aluminum sand casting
Aluminum sand casting

Sand casting is an old manufacturing method that remains relevant in the current manufacturing world. Typical applications of the technique include:

Automotive Industry

Sand casting is a common method in the automotive industry for making automotive parts with complex designs. Sand casting products in the automotive industry include engine blocks and transmission housing.

Aerospace Industry

Sand casting is also popular in aerospace, with a common application in making aircraft engine components and structural parts such as turbine blades, housings, brackets, and fittings that demand strength and precision.

Construction

The common sand casted product in the construction industry includes pipe fittings, manhole covers, etc. Sand casting ensures the production of a durable and robust product, which ensures longevity in construction applications.

Plumbing

Sand casting is applicable in making parts with plumbing applications. These include valve bodies, pipe connectors, and couplings.

Metalworks

The sand-casting process is commonly applicable in making metal works in different parts of the world. This includes swords, pots, cauldrons, etc. While other manufacturing methods replace sand casting, its cost-effectiveness and high-volume production continuously make it more suitable.

ZINTILON Support for Your Custom Sand Casting Service

This article discussed the sand-casting process, introducing how it works so businesses can make more informed decisions. However, after choosing a part to cast, the success of such a project depends on the custom sand casting services you use.

At Zintilon, our expert teams and manufacturing capability are well-versed in the sand casting process. From the prototyping to the mass production stage, our experts can ensure you use the right process and material for your project. We also render other casting services, including die casting. Contact us today, and let us bring your project to life.

Conclusion

Sand casting is an old metal manufacturing technique that is versatile in design and material compatibility, hence its wide application. This article discusses the process so that businesses can make an informed decision. Looking for a sand-casting service? Zintilon is your trustworthy and reliable partner.

FAQs

How Durable Are Sand Casting Products?

The durability of a sand casted part depends on the material you use. For example, aluminum cast parts are durable but have poor bearing surfaces. As a result, they have lesser application in robust conditions. On the other hand, bronze casted parts are strong and applicable in robust applications.

What Is the Lifespan of Sand-Casting Products?

There is no unique life span for a sand casted product. The life span depends on the material, good design, and the integrity of the manufacturing process. Having control over these will ensure a long-life span.

How Does Sand Casting Differ from Other Types of Casting?

Sand casting and other casting techniques differ in the cavity’s formation. For example, in die casting, the cavity is made using machining. On the other hand, sand casting involves using a pattern

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