Sand casting is the oldest and most widely used casting process. Investment casting is often seen as its higher-precision cousin. Here is a practical comparison.
Head-to-head comparison:| Factor | Investment Casting | Sand Casting |
|---|---|---|
| Mold material | Ceramic shell (fired) | Sand + binder (compacted around pattern) |
| Pattern | Wax (disposable) | Wood, metal, or plastic (reusable) |
| Minimum wall thickness | 1.0-2.0 mm | 3.0-6.0 mm |
| Tolerance | ±0.5% of dimension | ±1.0-2.5% of dimension |
| Surface finish Ra | 3.2-6.3 µm | 6.3-25 µm |
| Draft angle required | 0° possible | 1-3° minimum |
| Tooling cost | $3,000 - $15,000 | $1,000 - $10,000 |
| Minimum quantity | 50-100 parts | 1-10 parts |
| Part weight range | 1 g - 25 kg+ | 100 g - 1000 kg+ |
| Secondary machining | Often needed | Almost always needed |
| Post-processing cost | Lower | Higher |
- Thin walls (under 3 mm) — sand casting cannot reliably cast them
- Tight tolerances (±0.5% vs ±1.5%) — reduces or eliminates machining
- Complex internal geometry — ceramic cores create passages impossible in sand
- Zero draft — sand casting requires draft for pattern removal
- Fine surface detail — for cosmetic or flow-critical surfaces
Investment casting produces better surface finish (Ra 3.2-6.3 vs 6.3-25 µm), tighter tolerances (±0.5% vs ±1.5%), thinner walls (1.0 vs 3.0 mm minimum), and more complex geometry including zero-draft features and internal passages. The trade-off is higher tooling cost and longer lead time. Investment casting is chosen when the quality and complexity justify the premium over sand casting.