Investment casting, also called lost wax casting, is a precision metal manufacturing process used to make complex parts with smooth surfaces and high accuracy.

Here is how the process works step by step.

1) Create the Wax Pattern

The first step is to make a wax model that has the exact same shape as the final metal part.

This is usually done by injecting wax into a metal mold.

Examples:

• valve body
• pump impeller
• machine bracket
• automotive part

The wax pattern must include all details, holes, and dimensions.

2) Assemble the Wax Tree

If multiple parts are produced in one batch, the wax patterns are attached to a central wax runner.

This looks like a tree, so it is called a wax tree.

This step improves production efficiency and reduces cost per piece.

3) Build the Ceramic Shell

The wax tree is dipped into ceramic slurry and then coated with fine refractory sand.

This dipping and drying process is repeated 5–9 times until a strong ceramic shell is formed.

The shell becomes the mold for the molten metal.

4) Remove the Wax (Lost Wax)

The ceramic shell is heated in a furnace or autoclave.

The wax melts and flows out, leaving a hollow cavity inside the shell.

This is why it is called lost wax casting.

5) Pour Molten Metal

Next, molten metal is poured into the empty ceramic mold.

Common materials include:

• stainless steel
• carbon steel
• alloy steel
• aluminum
• brass

The metal fills every detail of the cavity.

6) Cooling and Shell Removal

After cooling, the ceramic shell is broken away.

Now the metal part is visible.

The gate and runner system are cut off.

7) Finishing and Machining

The final part is then:

• ground
• polished
• CNC machined
• inspected

This ensures the casting meets tolerance and surface requirements.

Simple Process Flow

Wax pattern → Wax tree → Ceramic shell → Dewax → Metal pouring → Cooling → Finishing

Why Use Investment Casting?

Main advantages:

• high precision
• smooth surface finish
• complex shapes
• less machining
• suitable for stainless steel parts