Investment casting, also called lost-wax casting, is a manufacturing process that produces metal parts by creating a wax pattern, coating it with ceramic to form a shell, melting out the wax, and pouring molten metal into the resulting cavity. It is one of the oldest known metal-forming processes (used for thousands of years in art and jewelry) and one of the most versatile for producing complex metal parts in a wide range of alloys.
The process steps:
| Step | What Happens | Temperature |
|---|---|---|
| 1. Wax injection | Wax is injected into an aluminum or steel die to form the pattern | 40-80°C |
| 2. Pattern assembly | Multiple wax patterns are attached to a central wax sprue (forming a "tree") | Room temperature |
| 3. Shell building | The wax tree is dipped in ceramic slurry, stuccoed with refractory sand (5-8 layers) | Room temperature |
| 4. Dewaxing | The ceramic shell is heated; wax melts out and is recovered | 100-200°C |
| 5. Shell firing | The ceramic shell is fired to full strength | 800-1100°C |
| 6. Pouring | Molten metal is poured into the hot shell | 1400-1650°C (steel) |
| 7. Shell removal | Ceramic shell is broken away from the cast parts | Room temperature |
| 8. Cut-off & finishing | Parts are cut from the tree, gates ground flush, surfaces finished | Room temperature |
The key difference is the ceramic shell mold. Unlike sand casting (where the sand mold is destroyed after each pour), the investment casting shell is a precision ceramic replica of the wax pattern — it reproduces fine details, surface textures, and complex internal geometry that sand casting cannot match.
Typical part size range:| Weight | Feasibility | Example Parts |
|---|---|---|
| 1-50 g | Excellent — fine detail | Jewelry, dental brackets, small medical components |
| 50-500 g | Excellent — sweet spot | Valve bodies, pump impellers, brackets, fittings |
| 500 g - 5 kg | Good | Machine parts, automotive components, aerospace brackets |
| 5-25 kg | Possible with specialized handling | Large valve bodies, turbine blades, structural components |
| > 25 kg | Difficult — shell strength limit | Requires other casting methods |
Investment casting (lost wax) is a precision metal casting process that uses a disposable wax pattern coated in ceramic to form a mold. After the wax is melted out, molten metal is poured into the ceramic cavity. It produces complex parts with good surface finish (Ra 3.2-6.3 µm) and moderate dimensional accuracy (±0.5% of dimension). It is used for stainless steel, carbon steel, aluminum, titanium, and nickel superalloys across medical, aerospace, automotive, and industrial applications.