Investment Casting… Making the Unmakable Part

One of the most ancient and widely used industrial processes in human history is metal casting. The process was mainly used to make jewelry and ornaments using molten metal and predesigned molds.

In modern-day manufacturing, standard procedures have been developed to manufacture more intricate parts through a process known as investment casting. The investment casting process uses wax, ceramic slurry, and molds to create metal components with low-tolerances, high-quality surface finishes, and high dimensional precision. This article will help you get more insight into the investment casting process and how it is used to make parts thought to be unmakable.

What Is Investment Casting?

Investment casting is one of the industrial manufacturing processes based on the lost wax casting concept. The process uses mold created with wax patterns to design metal parts. Also known as precision casting, investment casting is widely used due to its ability to produce parts with precision, repeatability, material integrity, ad versatility.

The wax patterns used in investment casting must withstand extreme pressure and forces from the mold-making stage.

The Investment Casting Process

The entire investment casting process can be summarized in the following steps:

• Pattern making: in this stage, a 3D model of the required part is designed using CAD data and technology. The tool designed here is used to create the wax pattern. A thermosetting wax injection molding machine is often used in this process.
• Assembling the wax pattern: the resulting wax pattern is connected to a tree during the pattern assembling stage.
• Ceramic shelling: the entire wax assembly is then dipped into a ceramic slurry and then left to dry. The process may be repeated severally to achieve the desired thickness and strength.
• Dewaxing: the ceramic shell is heated to melt away the wax.
• Shel firing: the resulting shell is fired at a high temperature to enhance its mechanical strength.
• Casting: molten metal is poured into the mold and left to cool until complete solidification is achieved.
• Shell removal: after solidification, the shell is broken to reveal the final component.
• Final operations: the metal casting is removed from the assembly through cutting or plasma techniques.

After the removal of the final piece, it can be subjected to various post-processes to achieve the desired specifications. However, machining is not always done since investment casting produces an excellent surface finish.

Inspections and testing ma be done to ensure that the final part meets all the required standards and specifications.

Investment Casting as A Lean Manufacturing Process

From a manufacturing perspective, efficiency is one aspect that makes investment casting such a widely used technique. With the near-net efficiency, investment casting eliminates the need for post-processes.

The investment casting process can ensure up to 90 μin surface finish. However, some parts may require machining, such as heat treatment, to achieve the desired specification.

Additionally, investment casting allows manufacturers to deal with a wide range of material selections. The process is also material-efficient, meaning that it reduces wastage as much as possible. This aspect is very important when considering the overall cost of production.

Precision casting can also achieve tight tolerance of ± 0.003 in./in. This is essential for intricate parts, such as jet engine components. Finally, investment casting can also produce intricate parts with thin walls of up to 0.025 inches.

Investment casing is also a very versatile casting process. Investment casting manufacturers can use a wide range of ferrous and non-ferrous materials with the precision casting process. Alloys are mainly used to improve the material strength of the final parts.

Applications of The Investment Casting Process

The applications of investment casting are far-reaching. This is mainly because investment casting is reliable in projects that require detail, repeatability, and large production volumes.

While precision casting can be expensive compared to other casting processes, it is the most reliable and fastest for producing small parts with complex designs and shapes. Therefore, investment casting can be used in many applications, especially in the aerospace and automotive industries. Power, oil and gas, military, and medical sectors also rely on investment casting to produce intricate parts.

Investment casting applications are limitless. Therefore, you can rely on investment casting if dimensional accuracy and part volume are two important specifications for your project.

Advantages and Disadvantages of Investment Casting

Advantages of Investment Casting

The benefits of investment casting include:

• Precision casting makes it easier to produce intricate parts.
• It ensures smooth surface finishes that eliminate the need for machining and other post-processes.
• Investment casting allows manufacturers to work with a wide variety of materials. The process uses both ferrous and non-ferrous metals and alloys. This aspect makes it very versatile and reliable.
• The process ensures high dimensional accuracy.
• Investment casting is perfect for producing small parts.
• Precision casting is cost-effective because it eliminates the need for machining after the final operation.
• The process reduces wastage.
• With investment casting, manufacturers can customize parts and add names and logos.

Investment casting has many benefits, and that is why it is widely used in industrial manufacturing processes. However, it also has its drawbacks.

Disadvantages of Investment Casting

Away from advantages, investment casting also falls short in some aspects. The following are disadvantages of the investment casting process:

• Investment casting is limited in terms of size. For instance, the process cannot be used to produce larger parts of more than 75lbs.
• The investment casting process is complex and can be very expensive, considering the initial investment required.
• The process is only cost-effective for high production volumes. Otherwise, you may be forced to try other casting processes for low production volumes.
• Investment casting cannot manufacture parts with holes smaller than 1.6mm or deeper than 1.5 times the diameter.

While investment casting is precise and highly reliable, it also has disadvantages that may force you to look for alternative casting methods. Therefore, you have to determine if your needs necessitate using investment casting.

The Bottom Line

The investment casting process has evolved from the lost wax casting process over the years due to advanced technologies. The technique is mainly driven by global demands and trends that make it widely applicable in different industries.

Advanced technologies, such as additive manufacturing or 3D printing, make investment casting more reliable. With these technologies, investment casting can make parts you thought are unmakable.