How Does Investment Casting Work?

At Protocast Inc. we have been providing the greater Denver area with prototype casting and industrial casting services for over 20 years. As we have grown in size, we have noticed more and more that while our customers really want a beautiful product that has gone through rapid prototype casting, they also want to get a better idea of how their prototype has been cast. After all, when people think of casting they simply think of pouring molten metal into a void to create a pre-measured mass.

While yes, in short, a prototype is made using molten metals, there is much more to the rapid prototype casting process than simply heating the metal and pouring it into a mold. In today’s blog post, we will be discussing the steps that are involved with the investment casting process.

Where Did Investment Casting Come From?

When you consider the major forms of product manufacturing, investment casting is distinctly different. But what person spent their time melting metals to discover this useful rapid prototyping application?

While investment casting might seem like a complex method of rapid prototyping, it is actually one of the oldest metal forming techniques and has been used in multiple different ways over the last 5,000 years.

Known as lost-wax casting during its inception, investment casting was once very different. Lost-wax casting used beeswax to form patterns and mold for the casting process. While today we might have more modern refractory materials, the beeswax used in early investment casting was rather efficient. That being said, we will happily still use our modern investment casting techniques instead of beeswax.

Investment Casting: The Process

1. Producing A Master Pattern

Like with any other casting methods, it is incredibly important to have an original pattern made. While in the past the initial prototype pattern was made by master mold-makers or artists, they are now commonly made using 3D printing.

2. Create A Mold

Once you have created a master pattern, it is important to make a master mold. Known as a master die, mold can be machined separately or made from an impression of the master pattern.

3. Produce Wax Patterns

Wax patterns can be made from a variety of different materials, as confusing as the name can be. The wax patterns can be manufactured by pouring the materials into the mold, creating an even layer of coverage, or by filling the mold completely with the wax materials.

4. Assemble Wax Patterns

Once the wax patterns have been produced, it is now time to assemble them, creating the prototype shape that you wish to rapidly cast. In this process, it is incredibly important that all of the imperfections of the wax patterns are corrected, as the official start of the investment casting process begins next.

5. Apply The Investment Materials

During the investment application process, three steps are repeated over and over until the layer of investment materials have reached their desired thickness. The investment will eventually become a ceramic mold that is created by a series of coating, stuccoing, and hardening the investment material on the finished wax pattern.

6. Dewax

Once the investment materials have reached the desired thickness, it is time to let it cure before dewaxing the investment. Once cured, the investment is placed upside down in a furnace or autoclave and heated until the wax is melted or vaporized. Any wax that is recovered from the mold can be used again to create future investments.

7. Burnout Preheating

One of the final steps of the process before the investment is actually used is known as the burnout, a period in which the mold is heated to between 850 and 1100 degrees Fahrenheit in order to remove any lost wax that is lingering from the mold and any moisture that might hinder the structure of the investment later in the prototype casting process.

8. Pouring

Once the investment has been tried and tested, it is time to pour metal into the investment. The investment is placed upside down in a tube filled with sand and is then prepared to be poured full of molten metal to create the prototype.

9. Divesting

Divesting is a fancy word for crushing or dissolving the investment — removing it from the hardened metals that filled it during the pouring process.

Finishing

Once the cast has been removed from the investment, the prototype is complete. That being said, there will be imperfections that must be cut off, as well as blemishes that might need to be ground or machined.

Why Use Investment Casting?

Investment casting is by no means the most common application or rapid prototype casting, but it does have its advantages — making it an optimal casting method for select prototypes. Some of the most noteworthy benefits that can be exploited by using this casting method are:

• High-quality surface finish
• High-dimensional accuracy
• Intricate parts are castable
• Most metals can be cast
• No flash or parting lines should exist

Where Is Investment Casting Used Most?

Investment casting can be used for a number of different projects, but among the most common are projects that need to be extremely precise. Both aerospace engineering and the power industries are known to be common customers of investment casting organizations because they require precision in their turbines and cooling system parts. Other common uses for investment casting include the rapid prototyping of firearms, golf clubs, and other tools that are made primarily of metal materials.

For Your Investment Casting Needs, Contact Protocast Inc.

At Protocast Inc. we have been providing leaders of multiple industries with high-quality cast prototypes for a variety of different functions and applications.

If you need a casting project completed we urge you to get in touch with a member of our team to discuss our various casting applications, methodologies, and techniques so that we can help you determine what type of casting can best provide you with the results that you seek.

we look forward to working with you and your team.