How Are Investment Casting Parts Made?

Posted on Dec 24, 2020

Investment casting is also known as lost wax casting. As the name suggests, it is the process of casting the final products through the removal of wax, and the products, or the investment casting parts, would be almost the virtual prototypes of the wax mold that is made depending on the requirements.

What Are Investment Casting Parts?

The investment casting parts are the products that are made by undergoing investment casting and are usually used as the components or accessories of the larger or more sophisticated machines or devices. The investment casting parts can be ferrous or non-ferrous, including cast iron, stainless steel, titanium, or carbon steel, to name a few. The capability of the investment casting outperforms other casting methods, as it allows for a variety of materials to cast, and is able to make various products with intricate forms at the same time, which results in the versatility of the investment casting parts.

In addition to the versatile materials that the investment casting can work for, the investment casting parts can be made at a wide weight range, which can be at least a few grams and up to almost one metric ton. This expands the number of the available applications of the investment casting parts even more. In short, the available materials and weight range of the investment casting parts both make this casting method common as well as practical in the industries that produce a variety of components and accessories.
 

What Is Investment Casting?

Investment casting is also known as lost wax casting. As the name suggests, it is the process of casting the final products through the removal of wax, and the products, or the investment casting parts, would be almost the virtual prototypes of the wax mold that is made depending on the requirements.

Before the wax is lost or removed, there are some processes that make up the wax mold, including wax pattern casting, wax pattern assembling, ceramic shell configuration, and wax assembly removal. Once these processes have been conducted, the wax pattern assembly would be covered by a ceramic shell, which would then be transferred into the ceramic mold.
 

Wax Pattern Casting

During this process, the wax is poured into several aluminum-injection dies, which are the partial sections of the investment casting parts. Once the wax in the aluminum injection dies is solidified, then the formed patterns of the wax would be removed from these aluminum-injection dies and transferred to the nest working site.
 

Wax Pattern Assembling

This process can be regarded as the initial formation of the investment casting parts since the assembly that is made with the wax patterns being attached together would be the prototype of the final product. The solidified wax patterns would be dipped into hot iron in order to allow these patterns to be attached to other parts, until the final prototype is completed, which is called the metal delivery system.
 

Ceramic Shell Configuration

Once the prototype is made, then it would be immersed into a ceramic solution that is called the slurry, and strengthened with sand stucco. This process would be repeated a few times until the desired thickness is achieved. After the wax assembly impregnated with slurry and sand stucco is dried off after about five days, the ceramic shell configuration is finished.
 

Wax Assembly Removal

This process is the real lost-wax process, which is to remove the wax inside the ceramic shell by heating and melting the wax in the autoclave, and the ceramic shell would be revealed afterward.

When the wax assembly is removed, then the casting process would follow that. The removed wax assembly is the prototype of the investment casting part, so the space that is left behind inside the ceramic shell would then be filled with molten metal. Once the molten metal is cooled and hardened after a few hours, the exterior ceramic shell would be broken off, and then the rough form of the investment casting part would be presented. In this process, the investment casting parts are usually free from further machining works except for the smoothing of surface finishes, as they are almost what they are supposed to be.
 

:: Read More: What Are Investment Casting Products?

What Can the Investment Casting Parts Be Used for?

The materials that can be used to make up the investment casting parts may be cast iron, stainless steel, titanium, carbon steel, or other alloys based on iron, aluminum, nickel, cobalt, titanium, and copper. The cast iron is electrically conductive, which makes the investment casting parts that are made of cast iron or the alloys that contain iron suitable for being applied to other electric energy-oriented machining works, such as the production of electrodes.

The investment casting parts that are made of stainless steel are various since stainless steel is capable of resisting high temperature and high pressure. This led to the stainless steel investment casting parts being widely used in the automotive, aerospace, and medical industries, or the plumbing and pumping systems. As for the titanium investment casting parts or the parts that are made of titanium alloys are good at corrosion resistance, which means that they are durable without being easily corroding by water or other fluids. This allows these investment casting parts to be applied in the vehicle parts, musical instruments, medical, oil, and gas industries.

Besides, the investment casting parts that are made of carbon steel or the alloys that contain carbon can be separated into three levels depending on the amount of carbon and the different features that they have, including low-carbon steels (< 0.20% C), medium-carbon steels (0.20 to 0.50% C), and high-carbon steels (> 0.50% C). The low-carbon steels contain the least amount of carbon, but the tensile strength, ductility, abrasion resistance, and hardness of them can be enhanced after being heated. 

The medium-carbon steels contain more carbon than the former, and the features that are mentioned are strengthened even more, which allows for secondary machining works to be conducted. In addition, the high-carbon steels, which contain the largest amount of carbon, are suitable for making springs or other heavy-duty applications.
 

What Are the Advantages of Investment Casting?

The Integrity of Investment Casting Parts

Since the final ceramic shell is formed by the assembling of several wax patterns, although the processes take more time and effort, the investment casting parts are formed with one of investment casting. In other words, the parts that are made of investment casting are free from being formed by combining several sections of the mold, which may leave partial lines on the products. Instead, the investment casting offers the optimal integrity for the products it makes.
 

Wide Ranges of the Sizes and Weights of the Final Products

As the various investment casting parts that are available for being cast by this method, the size and weight ranges of the products that investment casting is able to make are very wide, which means that either a small component or a larger and complete part of the application can be made by investment casting.
 

Allows for Intricate or Sophisticated Casting Parts

This is related to the shapes of the investment casting parts. Despite the fact that the processes of investment casting are relatively more complicated than other methods, this method allows for casting more intricate or sophisticated parts accordingly, which is one of the best advantages of investment casting.

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