Why we use Vacuum Investment Casting

We use 2 primary casting methods for non-ferrous metals. Firstly lost wax vacuum investment casting and ceramic shell casting. Both of these methods lend themselves to different types of products, Vacuum Investment Casting enables us to work in very fine jewelry level detail and with complex castings.

 

In this section we would like to explain a little of what the Vacuum Investment process of casting metal is.

​

Lost wax vacuum investment casting is a specialised form of investment casting, a process also known as cire perdue, or "lost-wax" casting. It uses a vacuum to pull molten metal into a ceramic mold, ensuring it fills all the intricate details of the mold cavity. This technique is used to produce high-precision metal parts with a smooth surface finish and minimal internal defects.

 

What is vacuum investment casting?

​

This method is an enhancement of traditional investment casting, which typically happens in open-air conditions. The key difference is the use of a vacuum during the crucial pouring and filling stages. 

​

Why vacuum?

​

Using a vacuum environment offers several advantages: 

• Reduced defects: It prevents air bubbles and trapped gases from forming within the mold. This significantly reduces the risk of porosity and other internal defects, resulting in a stronger and more reliable final component.

• Enhanced detail: The vacuum helps pull the molten metal into every fine detail of the mold, even filling intricate and thin sections that might be missed in open-air pouring. This results in superior accuracy and surface quality.

• Minimal oxidation: A vacuum environment prevents oxidation of the metal as it is being poured, which is especially important for casting reactive metals and high-performance superalloys.

​

The process

​

The steps for lost wax vacuum investment casting follow the standard lost-wax process, with the addition of a vacuum during the investing and casting stages. 

1. Wax pattern creation: A wax model of the desired object is created. For mass production, this is often done by injecting molten wax into a master mold.

2. Assembly: Multiple wax patterns can be attached to a central wax "sprue" to form a tree-like assembly, allowing multiple parts to be cast at once.

3. Investment: The wax assembly is placed inside a flask, which is then filled with a ceramic plaster (investment). A vacuum is applied at this stage to remove any air bubbles trapped in the investment before it hardens.

4. Burnout (Dewaxing): After the investment has set and hardened, the flask is placed in a kiln. The heat melts and vaporizes the wax, leaving a perfect negative cavity inside the ceramic mold.

5. Casting: The mold is heated in a vacuum furnace to prepare it for pouring. The molten metal is then poured into the flask while under a vacuum. The vacuum ensures the metal flows evenly and completely fills the mold cavity.

6. Quenching and shakeout: Once the metal has solidified, the cast is cooled, and the ceramic mold is broken away to reveal the finished parts.

7. Finishing: The individual parts are separated from the central sprue and are then cleaned and finished through processes like grinding and polishing. 

​

Applications

​

Vacuum investment casting is used in industries where extreme precision, high quality, and minimal defects are critical. 

• Aerospace: For high-performance engine components and turbine blades.

• Medical: For precision surgical tools.

• Jewelry: To reproduce highly detailed and intricate jewelry designs in various metals.

• Automotive and industrial: For components like turbocharger parts and valves. 

​