Investment Casting Guide
Investment casting (lost-wax casting) produces complex metal parts with excellent surface finish and tight tolerances, without draft requirements or parting lines.
Process Steps
- Wax injection: Wax pattern injected into metal die. Tolerances ±0.05mm on pattern dimensions.
- Tree assembly: Multiple wax patterns attached to a sprue system for batch casting.
- Shell building: Ceramic slurry dip + stucco. 6-10 layers. Inner layer: fine zircon. Outer: coarse mullite.
- Dewax: Flash-fire at 900-1100°C. Wax melts out leaving ceramic shell.
- Pouring: Molten metal poured into preheated shell (800-1100°C).
- Knockout & cut-off: Ceramic shell broken, parts cut from sprue.
- Finishing: Grinding, heat treatment, inspection.
Capabilities vs Other Casting Methods
| Feature | Investment | Sand Casting | Die Casting |
|---|---|---|---|
| Tolerances | ±0.1mm | ±0.5-2.0mm | ±0.05-0.2mm |
| Surface finish | Ra 1.6-3.2 | Ra 6.3-12.5 | Ra 0.8-3.2 |
| Min wall thickness | 0.5-1.0mm | 3-5mm | 0.5-2.0mm |
| Max weight | ~50kg | Unlimited | ~25kg |
| Tooling cost | 3567835$ | $ | 35678353567835 |
Material Options
- Carbon & low-alloy steels: 1020, 4140, 4340 — most common
- Stainless steels: 304, 316, 17-4PH, 410
- Tool steels: D2, H13, M2
- Aluminum: A356, 6061, 7075
- Copper alloys: C95200, C95400, C95800
- Superalloys: Inconel 718, 625, Hastelloy, Stellite
Design Guidelines
- Avoid sharp internal corners — use R1mm minimum, R3mm preferred
- Uniform wall thickness prevents hot spots and shrinkage defects
- Holes as small as 1.5mm can be cast directly
- Thicker sections need risers for feeding — adds cost
- For cored holes, taper at 1-2° for ceramic core removal