What is Investment Casting?

Investment Casting Overview

Investment casting is a precison casting process with long history, it allows for the production of complex, small to medium metal parts in different shapes. Investment casting process starts from the creation of a wax model, which accurately copies the design intended for the final product. This wax model is then enclosed in a durable ceramic. After the outer shell is solidified, the inner wax layer is melted off and removed to create an empty ceramic mould. This cavity is then filled with molten steel, which assumes the exact shape and size of the desired part. Once the metal cools, it solidifies and forms the intricate component. In the final step the ceramic is removed to reveal the completed metal piece.

Investment casting has its advantages for producing parts that have a superior surface finish, tight tolerances and complex designs. This makes it well suited in various industries, such as marine industry, aerospace industry, automotive industry, and more. Due to its ability of producing precisely detailed parts with reduced secondary operations, investment casting is one types of casting processes suitable for creating essential components.

The Investment Casting Process

Investment casting is an intricate manufacturing process that creates high precision metal components. These are the basic steps in the process.

1. Wax Pattern Creation

The journey of investment casting begins with the creation of wax patterns. Skilled workers inject wax material into the aluminum mold, which perfectly forms the desired final product in both shape and size. This wax model is the foundation for the entire casting process.

2. Assembly

In the assembly stage, the wax patterns are meticulously attached to a central wax sprue. This is usually known as a pattern assembly or tree. The central sprue plays a important role as it will serve as the channel through which the molten metal will ultimately flow into the intricately shaped wax patterns.

3. Shell Building

The pattern assembly is now ready to proceed the transformative shell-building stage. In this intricate process, the pattern assembly is dipped in a ceramic slurry. Over time, multiple layers of refractory materials are applied, and each layer should be dry before the next one is added. This meticulous repetition results in the creation of a durable and thick ceramic shell that wraps the delicate wax patterns.

4. Dewaxing

Once the ceramic shell fully formed, it’s time to start a critical step known as dewaxing. The entire assembly, now encased in the ceramic shell, is subjected to a furnace in high temperature. This heating process causes the wax inside the ceramic shell to melt and drain away, a process that gives “lost-wax casting” its name. The result is a hollow ceramic mold with precisely defined cavities that mirror the original wax patterns.

5. Burnout/Preheating

Following dewaxing, the ceramic mold undergoes a burnout process, subjecting it to extreme temperatures. This process can ensure that the residual wax is complete removed, the mold is hardeded, which prepares for the next pouring process. The preheated mold is now ready to receive the molten metal.

6. Pouring

The pouring step is the heart of the whole investment casting process. Molten metal, which is selected to match the required metal grade, is carefully poured into the preheated ceramic mold. The metal flows into the intricately shaped cavities quickly to fill each corner of the mold. As the metal cools and solidifies within the mold, it forms the desired shape and dimensions same as the original wax patterns.

7. Shell Removal

Once the metal has fully solidified, the ceramic shell must be removed to achieve the cast metal component. Vibratory methods are often employed to break away the ceramic shell, unveiling the intricately crafted metal casting within.

8. Cut-off

Following shell removal, the individual metal castings are separated from the central sprue using saws or cutting tools, ensuring a clean and precise separation.

9. Finishing

The final step of investment casting involves any necessary finishing operations to meet the specific requirements of the component. This may include heat treatment for enhanced material properties, machining for precise dimensions, shot blasting for clean and fine surface finish, or polishing to achieve the desired luster and aesthetics.

The Importance of Investment Casting in Today’s Industries

Investment casting holds a pivotal role in today’s industries, with its importance stemming from its ability to produce high-quality, intricate, and precision components. Below are some key reasons why investment casting is important:

Design Flexibility

Design freedom is especially important for complex and intricate parts that may have multiple internal and external shapes. Investment casting is not limited by size, thickness, or configuration. It has the ability to adapt and shift to meet any challenge.

Tighter Tolerances

For investment casting, tighter tolerances are the most important advantage comparing with other manufacturing methods. When a part is engineered, it has to be manufactured to meet the exact specifications of the design so it will easily integrate with other parts. With investment casting, tolerances vary according to part design, with symmetrical shapes with uniform walls having tighter tolerances than non-uniform and non-symmetrical shapes.

Superior Finish

Investment casting produces superior surface finishes that require less after-production finishing. The surface finish of investment casting parts ranging from Ra6.3-Ra12.5, which depends on the investment casting method used. The quality of surface finishes is much better than those of other casting processes. No other production method can match the combination of tight tolerances and exceptional finishes found in investment casting.

Wide Selection of Materials

Another advanced advantages of investment casting is that, it can cast a variety of materials. This technique can accommodate the material needs of many industries, including stainless steel, alloy & carbon steel, nickel based alloys, aluminum alloys, brass & copper alloys, and so on.

Cost Effectiveness

in Small-Batch Manufacturing Despite the initial set-up costs, investment cast is a cost-effective method for producing small to medium production quantities. This advantage is most pronounced in the production of intricate and complex parts.

Given these advantages, investment casting is extensively used in various sectors, including:

The Importance of Investment Casting in Today’s Industries

  • Aerospace: Used for manufacturing components like engine parts, landing gear components, and parts for the interior cabin of aircraft.
  • Automotive: Used for producing complex parts like engine components, gearboxes, and brake system components.
  • Medical: Used in the production of intricate surgical instruments, implants, and medical device components.
  • Energy: Used in the manufacturing of turbine blades, burner nozzles, and other components for the oil, gas, and renewable energy industries.
  • Defense and firearms: Used for the production of various components for firearms, as well as parts for military vehicles and equipment.
    Overall, the versatility and precision of investment casting make it a crucial manufacturing process in today’s industries.

The Metals Used in Investment Casting

Investment casting is a versatile process that can be used with a wide range of metals and alloys. Here are some of the most commonly used metals in investment casting:

Stainless Steel

Due to its high strength, good corrosion resistance and machinability, stainless steel is an excellent choice for investment casting. Depending on the application, different grades of stainless steel are used, such as 304, 316, 17-4 PH, 2205 duplex, and more. Some applications of stainless steel castings are: marine hardwares, pipe fittings, automotive components, glass fittings, etc.

Carbon Steel

Carbon steel is also a common material for investment casting. Examples of carbon steel alloys for investment casting include: AISI 1020, AISI 1030, AISI 1045, etc. Carbon steel is used for its mechanical properties in many applications, including automotive components, industrial equipment and construction.

Alloy Steel

Investment casting often uses alloy steels. These materials include AISI 4140, AISI 8620, AISI 8630, etc. These materials are a good balance between strength and toughness. Alloy steel is widely used for investment casting of some typical components, like bucket teeth, agricultural wear parts, and so on.

Nickel Based Alloys

Nickel based alloys, such as Inconel or Hastelloy, are used in investment casting process that have excellent heat and corrosion resistance. Due to its high nickel content, the cost of nickel based alloy castings is much higher than stainless steel castings. Nickel based alloys are suited for creating cast parts in special environments, which require high corrosion resistance or high heat resistance.

Aluminum Alloys

Aluminum alloys have many advantages, including being lightweight, strong and resistant to corrosion. These alloys are also easy to cast, and have a good thermal and electric conductivity. They are therefore perferred for automotive and aerospace applications.

Copper Alloys

Investment casting is often done with copper alloys such as bronze and brass. These materials are good for corrosion resistance, thermal conductivity and aesthetic appeal.

Titanium Alloys

Investment casting is used to produce titanium alloys for applications that demand high strength, low weight and corrosion resistance. These include aerospace and medical industries.

Precious Metals

Investment casting can be used to create jewelry and other artistic pieces using precious metals such as gold or silver.

The choice of metal used in investment casting depends on the specific requirements of the component being produced, including its mechanical properties, corrosion resistance, heat resistance, cost, and more.

Two Kinds of Investment Casting Methods

Both silica-sol investment casting and water glass investment casting are distinct investment casting methods used to produce intricate and complex metal parts. Each method offers its own advantages and characteristics.

Water Glass Investment Casting

Water Glass Investment Casting

Water glass casting is an old-fashioned casting technique that creates a ceramic mould around a wax pattern using a mixture sodium silicate, water glass, and refractory material. The mold is heated to remove all the wax and leave a cavity. The cavity is filled with molten metal. This method is cost-effective, which makes it ideal for large-scale production. It may not be as accurate as other methods such as silica-sol investment casting.

Silica Sol Investment Casting

Silica Sol Investment Casting

Silica sol casting is a method that is more precise and advanced. The mold is made by mixing a water-based solution of colloidal silica with a refractory substance. The particles of silica sol are so fine that they produce a more refined surface finish for the cast part. Silica sol casting is well-known for its high dimensional accuracy. It is used in industries such as aerospace and medicine where fine details and tight tolerances are important. It is more expensive than water glass casting, despite its superior precision.

The main differences between silica-sol investment casting and water glass investment casting are their precision and costs. Water glass investment casting may be more cost-effective, but it is not as accurate and detailed as silica sol casting. Silica sol investment casting is more expensive but offers superior precision and finish. This makes it the best choice for intricate components that need high quality. Both methods are suitable for different projects, depending on their specific needs and the balance between cost and accuracy.

Surface Finishing Options of Investment Castings

Surface Finishing Options of Investment Castings

Investment castings are produced with a near-net shape, but they may have a slightly rough surface after the dewaxing stage. This roughness is a result of the patterns left by the primary core of the ceramic mold. Typically, the surface finish is around 125 Ra, which may vary slightly based on the material and mold quality.

To achieve a smooth surface, various surface finishing treatments are available, each aimed at achieving the desired surface quality. These treatments can involve material removal or applying a coating to conceal and smoothen the rough surface.

The selection of a suitable surface finish technique depends on factors such as dimensional tolerance, desired appearance, and mechanical properties. The following are some of the surface finish operations that can be chosen:

  • Anodizing: Anodizing is a surface treatment method primarily used for investment castings made of aluminum. It creates a protective oxide layer on the surface, enhancing corrosion resistance and offering a range of color options.
  • Polishing: Polishing is a process that involves removing imperfections and achieving a smooth, reflective surface on investment castings. It improves the appearance and aesthetic appeal of the parts.
  • Painting: Painting is a surface finishing technique where a layer of paint or coating material is applied to the investment castings. It allows for customization in terms of color, texture, and protection against environmental elements.
  • Powder Coating: Powder coating provides a durable and visually appealing finish. It involves applying a dry powder to the surface of the castings, followed by curing under heat. Powder coating offers a wide range of colors, textures, and finishes.
  • Passivation: Passivation is a chemical process that helps remove surface contaminants and enhances the corrosion resistance of investment castings, particularly for stainless steel and other corrosion-prone materials.

These surface finish options allow for achieving the desired appearance and performance of investment castings. The appropriate technique can be selected based on specific requirements and considerations such as dimensional precision, desired aesthetics, and functional properties.

Investment Casting vs. Other Manufacturing Processes

When selecting a manufacturing method for your components, it’s essential to consider various factors such as design complexity, accuracy, surface finish, material versatility, cost effectiveness, production volume, complexity of tooling, weight range, and intricacy of details. In this table, we compare investment casting with other popular manufacturing methods, including sand casting, die casting, CNC machining, and forging, highlighting the advantages of investment casting.

Manufacturing Method Investment Casting Sand Casting Die Casting CNC Machining Forging
Complexity of Design ✅ High ✅ Medium ❌ Low ✅ High ✅ High
Accuracy and Precision ✅ High ❌ Low ✅ High ✅ High ✅ High
Surface Finish ✅ High ❌ Low ❌ Low ✅ High ✅ High
Material Versatility ✅ High ✅ Medium ✅ High ✅ High ✅ High
Cost Effectiveness ❌ Medium ✅ High ✅ High ❌ Medium ❌ Low
Production Volume ✅ High ✅ High ✅ High ❌ Low ✅ High
Complexity of Tooling ❌ Low ✅ High ✅ High ❌ Low ✅ High
Weight Range ✅ Wide Range ✅ Wide Range ✅ Wide Range ✅ Limited ✅ Wide Range
Intricacy of Details ✅ High ❌ Low ✅ High ❌ Low ❌ Low

Note:

✅ High: Indicates a strong advantage or suitability

✅ Medium: Indicates a moderate advantage or suitability

❌ Low: Indicates a disadvantage or limited suitability

Why Investment Casting in China?

Investment casting has gained significant popularity in China as a highly efficient and precise manufacturing process. China has become one of the leading countries in investment casting production, offering a wide range of capabilities and expertise. When comparing investment casting services in different areas, here are some key advantages in China:

Lower Production Costs: China generally has lower labor costs compared to the USA, which can result in more cost-effective production of investment castings. This can be particularly advantageous for larger production runs or cost-sensitive projects.

Vast Manufacturing Capacity: China has a vast manufacturing capacity and a large number of investment casting foundries. This means there is a wider range of options and more flexibility when it comes to selecting a suitable manufacturer to meet specific production needs.

Skilled Workforce: China has a large pool of skilled workers with expertise in investment casting techniques. Many Chinese foundries have years of experience and possess the necessary knowledge and skills to produce high-quality castings.

Advanced Equipment and Technology: Chinese investment casting facilities often employ modern equipment and technologies, including advanced molding equipment, quality control systems, and computer-aided design and manufacturing (CAD/CAM) capabilities. This allows for efficient production processes and high precision.

Material Options: China offers a wide range of material options for investment casting, including various metals and alloys. This flexibility allows for the selection of materials that meet specific requirements, such as strength, corrosion resistance, and temperature resistance.

Supply Chain Integration: China has developed a well-integrated supply chain ecosystem that supports investment casting. This includes readily available raw materials, tooling, and machining capabilities, which can contribute to streamlined production processes and shorter lead times.

It is important to note that while investment casting in China offers these advantages, there can be variations in quality among different manufacturers. There is a great significance to choose a reliable investment casting manufacturer before ordering.

CFS Foundry: Your Trusted Investment Casting Manufacturer in China

Investment Casting Manufacturer in China

At CFS Foundry, we are a leading manufacturer specializing in investment casting. With years of experience and a commitment to excellence, we provide high-quality investment casting solutions for various industries. Our expertise and dedication have made us a trusted partner in the field.

Our Capabilities of Investment Casting:

Design
Our team of skilled engineers and designers work closely with clients to develop customized designs that optimize the functionality and performance of cast components. We leverage the latest CAD and CAM technologies to ensure precision and efficiency throughout the design process.

Mold Making
CFS Foundry possesses state-of-the-art facilities for mold making. We employ advanced techniques and tools to create high-quality molds that guarantee accurate and consistent casting results. Our meticulous approach to mold making ensures superior product quality and dimensional accuracy.

Investment Casting
As experts in investment casting, we employ the lost wax casting process to produce intricate and complex components. With our precision casting techniques, we can achieve tight tolerances and excellent surface finishes. Our commitment to quality ensures that each casting meets the highest standards.

Machining
To provide fully finished components, CFS Foundry offers machining services. Our advanced machining capabilities enable us to perform precise operations such as milling, turning, drilling, and threading. This ensures that the cast components are ready for immediate use upon delivery.

Surface Finishing
We understand the importance of aesthetics and functionality, which is why we offer a range of surface finishing options. Whether you require polishing, sandblasting, powder coating, or other surface treatments, our skilled technicians can deliver the desired appearance and enhance the performance of the cast components.

Quality Control
Quality is our top priority at CFS Foundry. We have implemented stringent quality control measures at every stage of the investment casting process. Our dedicated quality assurance team conducts rigorous inspections and tests to ensure that each casting meets or exceeds the required specifications and industry standards.

Custom Packaging and Global Delivery
We provide customized packaging solutions to ensure the safe transportation of your cast components. With our global delivery network, we can ship your products to any location efficiently and securely. Our logistics team ensures timely delivery, allowing you to meet your project deadlines.

 

 

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