Precision Casting 101: Everything You Need to Know

What Is Precision Casting

Investment casting (also known as investment casting, lost wax casting, and cire perdue) is a metal forming technique that forms near-net-shape products. Compared with the traditional sand casting process, the castings obtained by precision casting are more accurate in size and have better surface finish. Its products are precise, complex and close to the final shape of the part. It can be used directly without processing or processing. It is an advanced near net shape process. And can be suitable for orders with small batch requirements.

And the technique has been used for centuries and is still widely used today in a variety of industries that require complex shapes and precision, including aerospace, automotive, jewelry and art.

Process Flow of Precision Casting

The investment casting process consists of several steps: mold design, production, housing construction, casting, pouring, finishing, and machining.

Phase  1: Mould engineering & production

Precision investment casting begins with the design and production of casting molds (also known as wax tools). By using casting molds, it is possible to paint wax models with very precise dimensions and excellent definition of contours. These wax models were glued onto so-called wax "trees" on which casting funnels were mounted. In a later stage of the process, the steel is poured into the funnel. Depending on the size of the series, the molds are mounted on manual or automatic presses.

Phase 2: Ceramics

After the wax models are glued together, the tree is given a fireproof ceramic shell. This shell is constructed by repeatedly submerging the tree (up to 7 or 9 times) in a slurry and sprinkling it with ceramic sand. The ceramic layers are then hardened in a drying chamber, and exposed to air.

After the layers have been formed and dried, the wax is melted out of the ceramic tree by using steam (120°C) in an autoclave. 

Phase 3: Casting process

The desired steel alloy is melted in a large furnace and brought to casting temperature. The ceramic tree is, at the same time, heated in an oven to prevent thermal shocks during the casting process. After the tree has been heated, it is removed from the oven by a robotic arm and the steel is poured in by means of counter gravity. When the trees have been cast, they have to be cooled on a cooling conveyor (with nitrogen). The trees are then removed from their ceramic shells, by breaking the shell with a fully-automatic knock-off hammer. This removes most of the ceramic.

Phase  4: Finishing  & Machining

The remainder of the ceramic is removed in the Finishing Department by means of steel, sand, and/or water blasting. The next step involves sawing or vibrating the products off of the steel tree. The steel leftovers are sorted on alloy and may be melted again during the next casting badge. Finally, the ingate is sanded off, the product is machined, calibrated, or heat-treated when necessary.

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What Are the Advantages of Precision Casting?

Precision casting offers several advantages over other manufacturing processes. For instance, the process eliminates the material wastage challenge common in subtractive manufacturing technologies like CNC machining, allowing you to reduce manufacturing costs. It also reduces the long production time common in metal fabrication processes like welding.

In addition, precision casting allows you to fabricate complex parts that might be challenging to create using CNC machines. So, suppose you’re looking to fabricate complex internal passages in a metal part, curved vanes of an impeller, or cooling channels in complex devices with great surface finishes. In that case, you must consider using precision investment casting.

Precision forging also allows you to create complex shapes, like the precision investment casting process. However, because the forging process requires specially designed tool dies, the associated tooling costs are higher than in precision casting. Additionally, precision casting offers greater design freedom, allowing you to produce larger and more complex geometries than other manufacturing technologies.

Which Materials Are Suitable for Precision Casting?

Some of the most common materials suitable for investment casting include:

Steel Alloys: Steel is one of the most widely used materials in investment casting due to its excellent mechanical properties, high strength and durability. Depending on the desired properties, different steel alloys are available, such as carbon steel, stainless steel, tool steel and alloy steel.

Aluminum alloy: Aluminum is a lightweight material with good corrosion resistance and thermal conductivity. Aluminum alloys are often chosen for parts where weight reduction is critical, making them ubiquitous in the aerospace and automotive industries.

Copper Alloys: Copper-based materials such as bronze and brass are used in investment casting when good electrical and thermal conductivity as well as corrosion resistance are required. These alloys are commonly used in various electrical components and decorative arts.

Nickel Alloys: Nickel-based alloys have excellent corrosion resistance, high temperature performance, and wear resistance. They are commonly used in industries such as chemical processing, marine and aerospace.

Cobalt Alloys: Cobalt based alloys are known for their excellent wear resistance and high temperature strength. They are commonly used in applications such as turbine blades for gas turbine engines.

Titanium Alloy: Titanium is a lightweight yet strong metal with excellent corrosion resistance, making it ideal for aerospace, medical and marine applications.

Superalloys: Superalloys are a group of high-performance alloys designed to withstand extreme temperatures and stresses. They are commonly used in aerospace and gas turbine engine components.

Precious metals: Precious metals such as gold, silver and platinum are also used in precision casting, especially in the jewelry industry or for the manufacture of high-end decorative pieces.

Which Industries Are Precision Castings Mainly Used For?

Aerospace: used to manufacture key components such as turbine blades, engine parts and structural components.

Automotive: Examples include engine components, transmission components, braking systems, and suspension components.

Medical: Surgical instruments, implants and medical devices require complex and custom components.

Oil and Gas: The oil and gas industry utilizes precision castings to produce parts used in drilling equipment, valves, pumps and other critical components.

Industrial machinery: Precision castings are used to produce gears, housings, and other components that require high precision and strength.

Defense: The defense industry relies on precision castings to create components for military vehicles, firearms and ammunition.

Ships: The ship industry utilizes precision castings to produce components such as propellers, ship accessories and ship engine parts.

Electronics: Precision castings are used in the electronics industry to make connectors, housings, and various other components that require complex designs and precise dimensions.

Art and Sculpture: Investment casting techniques are also used in the art and sculpture industry to create intricate and detailed metal artwork and sculptures.

Jewelry: In the jewelry industry, precision casting is used to produce intricate and delicate jewelry pieces with fine details.

When to Use Precision Casting?

Due to its complexity and labor requirements, investment casting is a relatively expensive process - but the benefits often outweigh the costs. Virtually any metal can be precision cast. Parts made by investment casting are usually small, but the process can be effectively used for parts weighing 70 pounds or more.

Investment casting is capable of producing complex parts with excellent as-cast surface finish. The investment casting process produces parts with excellent dimensional accuracy; net shape parts are easy to achieve and often require no secondary operations to produce the finished shape. Each unique casting requires a new mold to produce the wax pattern. Tooling for investment casting can be quite expensive; depending on complexity, mold costs can range from $1,500 to $12,000.

For high-volume orders, the time and labor saved by eliminating or reducing secondary operations can easily make up for the cost of new tooling. Minting in small batches is unlikely to make up for the investment. Generally, investment casting is a reasonable choice for 20 or more parts.

What Factors Will Affect the Precision of Precision Casting?

The following are factors that may cause precision defects in precision castings:

1. Tooling quality

Tooling is the first process to make precision castings, its quality is very important, a good tooling interior wall is smooth, and all the angles, radius, and transition section of structures is smooth too.

2. Filled pattern Wax quality

Filled pattern wax must have excellent flow properties and consistent dimensional stability with a superior surface finish, so the wax pattern is strong and flexible, with no shrinkage and the tiny line will be created during the wax is cooled at high temperature.

3. Slurry quality and coating process

Slurry must be heat resistant in order to resist the hot molten metal corrosion, a fine primary coat is critical to the surface finish of castings. The operation of slurry coating is also important, workers must break up every bubble during slurry coating and then coat the edges, angles, holes, grooves, and other important sections with fine brush carefully.

Are Precision Casting Services Expensive?

Although the up-front cost of investment casting is high, it is indeed cheaper than other casting processes under certain quantities. Depends on part count and complexity. For an accurate estimate of your project cost, it is recommended to contact multiple foundry service providers, share design specifications and request detailed quotes. This way, you can compare prices and choose the casting process service that is best for you.

How Much Does Precision Casting Cost?

The cost of investment casting can vary widely depending on factors such as the size and complexity of the part, the type of material used, the number of parts ordered, and the level of post-casting processing required. Therefore, it is difficult to provide an accurate cost estimate without knowing the exact details of the metal components.

However, to give you an idea of investment casting costs, here are some approximate estimates:

Small, simple metal castings: only a few hundred dollars each.

Each larger, more complex part can cost thousands of dollars.

Tooling costs range from $4,000 to $30,000, depending on the complexity of the tooling.

Therefore, the approximate budget you will need will depend on the size, complexity and quantity of the parts you need to produce.

In order to get an accurate quote, you should consult an investment casting company and provide them with detailed specifications of your project. They can provide you with detailed pricing so you can work out your final costs.

Top 10 Precision Casting Companies

Provides a list of the 10 best precision casting companies in the world. If you need investment casting services, you can contact them!

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Conclusion

The above is all about precision casting. If you need custom metal castings for your project, look no further than an investment casting company or fabricator.Of course, we can provide you with investment casting service, if you need it, you can contact us now. We will provide you with detailed solutions and quotations!

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