Investment Casting Spare Parts

Process Steps of Investment Casting

1. Mold Design & Manufacturing

A metal mold (or "die") is designed and machined from steel, with its cavity being the exact shape of the desired final part.

2. Wax Pattern Injection

Molten wax (e.g., paraffin-based) is injected into the metal mold under pressure to form a "wax pattern."

3. Wax Pattern Assembly

Multiple wax patterns are attached to a central wax "sprue" or "tree" to form a cluster, allowing for the production of many parts in a single casting.

4. Shell Building (The Core Step)

This is the defining step of the process.

Step 1: Slurry Dipping - The wax assembly is dipped into a ceramic slurry based on colloidal silica (SiO₂) binder and fine refractory flour (e.g., zircon, fused silica).

Step 2: Stuccoing - While the slurry is still wet, the assembly is sprinkled or rained with coarse, granular refractory sand (e.g., zircon sand, mullite).

Step 3: Drying & Curing - The coated assembly is placed in a controlled environment (temperature and humidity) to allow the colloidal silica to gel and bind the ceramic particles into a hard layer.

This "Dip-Coat-Stucco-Dry" cycle is repeated 5 to 9 times to build a ceramic shell thick enough (typically 6-12 mm) to withstand the molten metal.

5. Dewaxing

The completed shell is subjected to high-pressure steam (autoclave) or intense flash fire. The wax inside melts and runs out, leaving a hollow, precise ceramic mold (the "cast").

6. Shell Firing

The dewaxed shell is fired in a high-temperature furnace (~900°C - 1100°C) to remove any residual wax and moisture, strengthen the shell, and bring it to the required temperature for pouring.

7. Melting & Pouring

The specific metal alloy is melted in a furnace to the desired temperature and chemistry. The molten metal is then poured directly into the pre-heated ceramic mold.

8. Knock-out & Cleaning

After the metal has solidified and cooled, the ceramic shell is mechanically broken away, often using vibration hammers, to reveal the raw casting tree.

9. Cutting & Finishing

Individual castings are cut off from the sprue using high-speed abrasive wheels. The cut-off points are ground and finished smooth. Shot blasting is often used for final cleaning.

10. Final Inspection

Castings undergo rigorous quality control, including dimensional checks, visual inspection, chemical analysis, mechanical testing, and NDT (e.g., X-ray, LPT), to ensure they meet all specifications.