What is Investment Casting?

Investment Casting Overview

Investment casting is a lost wax precison casting technique with decades of history. It is mainly suitable for producing complex metal parts in various shapes with mass production. Investment casting begins by developing a wax model which accurately represents what will eventually become part of 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 offers many advantages for producing parts with superior surface finishes, tight tolerances and complex designs, making it suitable for numerous industries such as marine engineering, aerospace manufacturing and automobile assembly production. 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. Below are the basic steps involved in investment casting 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 step, the pattern assembly is dipped into ceramic slurry until multiple layers of refractory materials are applied. Pls note each layer should be dry enough before adding the next layer. This can creat 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. For example, heat treatment may be necessary to improve the mechanical properties, CNC machining for more precise dimensions, shot blasting for clean and fine surface finish, or polishing to achieve the desired bright surface.

5 Advantages of Investment Casting Process

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

The Importance of Investment Casting in Today’s Industries

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 offers smooth surface finishes that require minimal post-production finishing. CFS Foundry can achieve a fine surface finish ranging from Ra6.3-Ra12.5, which mainly depends on the casting method selected. While it is not available by other casting processes, such as sand casting.

Wide Selection of Materials

Another advanced advantage of investment casting is that, it can cast different types of metal materials. This technique can accommodate the material needed for 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.

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 Types of Investment Casting

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?

With a long history in China, the investment casting technique has become quite mature now. Compared with investment casting companies in America and Europe, there is a great price advantage to produce custom investment cast parts from China companies like CFS Foundry, while maintaining same good quality.  Take CFS Foundry for example, we are one of the largest precision investment casting companies located in Ningbo, China. With investment casting production nearly 30 years, we are constantly expanding our production scale to meet the increasing order volume. Meanwhile, hiring professional casting technicians with high salaries to improve our soft power. Therefore, both in terms of production equipment and technical experience, China’s investment casting capacity is far beyond India and Vietnam. Below are the detailed advantages to explain why you should order investment casting services from China.

Great Price Advantage: Due to the complex production process of investment casting, many workers are needed to complete efficient production. China has a large population, and many foundries have driven a large number of people to employment. At the same time, due to the sufficient labor force, compared with European and American countries, the labor cost in China is much lower. In addition, together with lower material costs, China’s investment casting production has a superior price advantage. This is the main reason for attracting overseas companies to purchase investment casting products in China.

Mature Casting Experience: Investment casting technology has a history of thousands of years in China. As time goes on, this technology becomes more mature and automated. For example, at CFS Foundry, our wax pressing and shell making processes have been transformed from manual operations to automated production. This not only improves production efficiency, but more importantly, it ensures production quality to avoid quality defects caused by manual errors.

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. In addition to investment casting companies, China has many supporting CNC machining and surface finishing companies. It greatly meets the various production requirements of investment casting products.

Convenient Transportation: For long-term export transportation, especially sea transportation, convenient transportation is particularly important. For investment casting factories in port cities, this not only saves transportation time, but also greatly reduces transportation costs. CFS Foundry is located in Ningbo, China’s second largest port city, it is very convenient for us to deliver goods to our overseas customers.

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

When Should You Consider Investment Casting for Your Design?

Part Weights Between 200g And 50kg

While investment casting can also be used for larger castings, it is more suitable for medium and small-sized parts. On one hand, maintaining dimensional accuracy becomes challenging with larger cast parts; on the other hand, the mold and processing costs tend to be higher. Sand casting is a better option for larger castings. Investment casting is ideal for smaller parts as it easier to maintain dimensional accuracy and the costs are within a reasonable range.

Medium to Large Production Volumes

Investment casting requires the processing of wax pattern molds and other fixtures, necessitating a significant fixed asset investment, making it more suitable for medium to large production runs.

High Dimensional Accuracy Requirements

Compared to other casting processes, investment casting provides the highest dimensional accuracy.

When Reduction or Elimination of Machining is Needed

Due to the high dimensional accuracy and good surface finish of investment castings, machining can often be reduced or eliminated. Even when machining is necessary, the amount of work required is less than that of other casting processes.

For Parts With Complex Internal Structures

Investment casting may be the optimal choice for parts with complex internal structures. This process can make extremely complex parts because there are no issues with mold release—the molds used for pouring the molten metal are ceramic and easily shed after cooling and solidification. Creative mold designs, soluble wax cores, or ceramic cores can be used to easily achieve the internal structures of the wax patterns, which are later covered to form ceramic shells. Therefore, there are no limitations on the internal details of parts in investment casting.

CFS Foundry: Your Trusted Investment Casting Manufacturer in China

Investment Casting Manufacturer in China

At CFS Foundry, we are a leading casting manufacturer specializing in lost wax investment casting process. 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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