What is Investment Casting and How does it work?

What is Investment Casting and How does it work?

​Investment casting is a widely used industrial process for remaking metal parts. There are several casting procedures available and investment casting is one among the many of these casting processes.
There are a lot of diverse factors that are responsible for determining which casting process will be deemed fit for the manufacturing of a specific metal part.
Some of these diverse factors are – design requirements, feasibility, and cost to manufacture are the important ones that are considered beforehand in determining the type of casting process that will work best.
If the process to be is used is investment casting, then it will be better to know the details of this process. Let’s get to understand the process of investment casting and how does it work?
In this brief write up first the process of investment casting is explained and then how does it work? So, let’s get started with the first question that’s what is investment casting? And after that how it works is also explained in this blog

What is Investment Casting?

​The word investment denotes surrounded and the procedure depicts the formation of a shell made up of ceramic, plastic, or plaster and this shell surrounds a wax pattern.
With the help of Investment casting, the metal parts that are produced are of complete precision. To start the process first, a wax pattern is made and then this wax pattern is coated with a ceramic material.
The ceramic material is then hardened. The wax is melted out of the ceramic mold leaving an empty cavity behind it. Now, the molten metal will be poured in this space.
After pouring, the metal gets solidified within the mold. At the end of the process, the shell is broken out and the metal part is subjected to finishing.
Now, let’s understand how the process of investment casting works?

How does Investment Casting work

Pattern creation

First and foremost a wax pattern is created that has similar details and intricate design as the finished part the only difference is that there is an allowance for thermal contraction.
These wax patterns can be made from specific wax and by the process of wax injection.

Mounting the wax pattern

​After numerous wax patterns are made these are joined with other wax patterns through a channel of gate and runner delivery system.
Later in the process, this gate and runner system will be used in filling molten metal in various molds at the same time. 

Formation of the tree

​Multiple wax pattern may be processed with the help of a single tree depending upon the size and configuration of the finished component. 

Shell creation

​Now, comes the formation of the shell and for this, the entire wax pattern is dipped in ceramic slurry and covered by sand stucco.

This process of shell formation by ceramic slurry coating on the wax patterns is repeated multiple times until the desired thickness of the shell is achieved.

After multiple repetitions of wet dipping and stuccoing, the desired product size is achieved. The desired thickness of the shell is dictated and dependent on the final product size and configuration.

The thickness of the shell should be enough to be able to hold the amount of molten metal poured into it without the shell breaking because of the pouring.

Now, the shell is dried so it becomes sufficiently strong for the further procedure.

Wax removal

​The entire assembly is now placed in a steam autoclave. This is done to melt away and remove most of the wax.

If there is any residual wax left in the entire assembly, then it is burned in the furnace.

After getting treated in the furnace, any residual wax is completely removed leaving behind an empty cavity in the shape of the desired cast part.

The high-temperature is essential to increase the strength and stability of the ceramic material. High-temperature also favors by minimizing any reaction of the shell and metal during pouring. 

Melting of metal and casting

To create the metal casting, the mold is preheated to a specified temperature and then filled with molten metal.

The benefit of using the investment casting process is that you can easily produce any metal alloy. Depending upon the alloy chemistry, either air melting or vacuum melting may be employed.

The use of vacuum melting is suggested if the alloy contains any reactive material in it. 

Finishing of the produced metal cast

​After the metal casting is sufficiently cooled, the shell mold is broken away in a knockout operation.

In the finishing stage, the gates and runners are cut from the casting. The final process of sandblasting, grinding, and machining are done on the metal casting to give it the perfect finishing.

Investment casting is a great method to design intricate contours and passages. Many of these designs can’t be achieved by any other method.