Investment Casting Process Steps

When manufacturing any product, you may discover that certain crucial parts are missing. You will then have to create those missing parts from scratch. There are several ways to do that, one of which is investment casting. In this article, I will show you the investment casting process steps. This might be useful if you want to replicate the process yourself.

What is Investment Casting?

Investment casting is one of the oldest means of casting metals. You may know it as precision casting or lost wax casting.

Typically, in investment casting, you dip a wax mold in a liquid material. You do this repeatedly while allowing the liquid material to cool off and harden on the mold.

After this, you burn off the wax, leaving a cavity where the wax previously was. You can then fill this space with molten liquid. To complete the process, you will need to remove the mold to reveal the product inside.

You may be wondering why this process is called investment casting. In truth, it does sound a little peculiar. Some people believe that the name reflects the fact that the mold is “invested” into the refractory material. This is because you deep into the material a few times to complete the process. Hence, you could replace the term with “clothed” to get a clearer understanding.

Investment casting has a very sketchy beginning. It has ties to the ancient Egyptian and Persian dynasties. Artists during those times sculpted works using the process. However, due to the oral history that mostly characterized that period, many were lost.

The most comprehensive record of the period is from a man called Theophilus Presbyter. From his records, we can glean that he inspired famed Italian sculptor Benvenuto Cellini.

Modern investment casting started around the 19th century. Dentists employed the process to create crowns for their patients.

Applications of Investment Casting

Investment casting is one process you can use for a variety of purposes. In fact, it is currently being applied across several industries. The popular ones are the aerospace and automotive sectors. This is because of the multiple small parts these industries typically need. This process is also used in firearms production (specifically for producing triggers). Those in the food and beverage industry also make use of it to produce utensils.

Investment Casting Process

Generally, there are five steps you take when manufacturing a product using investment casting. It is possible to expand these steps. However, in the direction below, I will examine all the steps fully.

The five stages are:

  1. Creating the Master Pattern
  2. Applying Refractory Materials
  3. Dewaxing
  4. Filling Up the Hollow Space
  5. Breaking the Mold

 

1. Creating the Master Pattern

This is where you create the wax pattern that will eventually form the shape of the product you want. The reason you use wax is because of how easily you can melt it. However, this comes with a unique problem, too: You will be able to use each wax pattern just once.

Some people have found ingenious ways of getting around this challenge. They create some sort of ‘master’ mold. These could be reused several times. The downside to this is that it is quite expensive.

There are two methods of creating the wax pattern. The first is through building a wax injection die. You can create this from aluminum.

Alternatively, you can create a 3D print pattern of the wax model. You may have to outsource this part if you choose this option.

 

2. Applying the Refractory Materials

 

After you create the master pattern, you then need to apply the materials that would form the mold. The materials you apply here are called refractory or heat resistant. Some of the options include silica, zircon, or aluminum.

Here, the first step is to dip the master pattern into the refractory material. It (the refractory material) should be in slurry form at this stage to thoroughly coat the master pattern.

Afterward, you can also add more of the refractory material to the master pattern by hand. You may decide to add sand particles to the wet master plan. This will help thicken it. The last stage is leaving the wet master plan in the sun (or any other source of heat) to harden.

The ideal thickness of the master pattern at this point should be 5 millimeters or more. Furthermore, you can introduce binders to the refractory material to make it tougher.

3. Dewaxing

This step follows immediately after you’ve completed the one above. Here, you turn the pattern upside down and introduce a great deal of heat. This would melt the wax, leaving a hollow space behind.

4. Filling Up the Hollow Space

You will have to do this while the pattern is still hot. This step involves filling the hollow space previously occupied by wax with molten metal. Since the pattern is already hot, the molten liquid can enter into the smallest crevices. This, in turn, makes sure there is fine detailing at the end.

5. Breaking the Mold

This final step is just as easy as it sounds. You will need to break the mold to reveal the molten liquid inside. At this point, the liquid would have hardened into the shape of the product you had in mind.

Pros of Investment Casting

As we come to the end of this article, it will be necessary for you to note the pros and cons of investment casting. You may find it invaluable while making a decision.

  1. One of the first things anyone with experience in investment casting will tell you is that it is highly accurate. When you go through this route, you will hardly need any machining afterward. This saves you both money and time.
  2. Another benefit of this process is that you can produce a wide variety of items with it. Whatever the design is, you can run it with investment casting.
  3. Even more so, you can use a wide range of metals for investment casting. You will not develop grey hairs while searching for compatible metals.

Cons of Investment Casting

Every good process definitely has its downsides. Hence, in this section, I will be discussing some of the downsides you may experience while using this process.

  1. One peculiar challenge you may experience is the fact that this process is most suitable for small castings. Of course, some manufacturers go right ahead to produce large objects with it. These don’t always turn out fine. Hence, for large products, this may not be the best process for you.
  2. Investment casting is a relatively more expensive procedure than the average. The increased cost is usually at the initial stages, even though you get to save some funds in the long run.
  3. Investment casting takes time. The production cycle is longer than the average. At the moment, you can automate some parts of the process using a machine. However, on the whole, it still takes a long time.  If you are working with a strict timeline, you may have to explore alternative options to investment casting.
  4. Investment casting may not work if the design isn’t purely solid.

Conclusion

In this article, I discussed the investment casting process steps. The pictures are to serve as visual aids, helping you along as you carry out the steps. Good luck!

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