How to Distinguish Sand Casting, Die Casting, and Investment Casting for Aluminum Parts?

Choosing the right casting method for Aluminum Die Casting Parts can mean the difference between a high-performance product and a costly failure. Sand casting, die casting, and investment casting each have distinct advantages—but misapplying them leads to wasted resources.
1. Process Mechanics: How Each Method Shapes Aluminum
Sand Casting uses expendable sand molds formed around a pattern. Molten aluminum is poured into the cavity, cooled, and then the mold is broken to retrieve the part. This method leaves a rough surface finish (typically Ra 12.5–25 μm) and requires post-machining for precision.
Die Casting forces molten aluminum under high pressure (10–200 MPa) into reusable steel molds. Rapid cooling yields near-net-shape parts with smooth surfaces (Ra 0.8–3.2 μm) and tight tolerances (±0.1 mm).
Investment Casting (lost-wax casting) builds a ceramic shell around a wax pattern. After melting the wax, aluminum is poured into the cavity, creating intricate shapes with fine details (±0.05 mm tolerance) and surface quality (Ra 1.6–6.3 μm).
2. Cost vs. Volume: Matching Method to Production Scale
Sand Casting: Ideal for low-volume, large parts (e.g., engine blocks). Tooling costs are low (500–5,000), but per-unit costs rise with manual labor. Cycle times range from hours to days.
Die Casting: Optimized for high-volume runs (10,000+ units). Initial tooling costs are steep (20,000–100,000), but per-part costs drop sharply due to fast cycles (30–300 shots/hour).
Investment Casting: Best for medium volumes (100–10,000 units) of complex, small-to-medium parts (e.g., aerospace brackets). Tooling costs fall between sand and die casting (5,000–30,000), with slower cycles (2–8 hours per shell).
3. Performance Trade-Offs: Strength, Detail, and Finish
Porosity: Sand-cast parts have higher porosity (4–8%), limiting their use in high-stress applications. Die casting minimizes porosity (1–3%) through pressurized filling. Investment casting achieves 2–4% porosity, suitable for aerospace tolerances.
Detail Resolution: Die casting struggles with undercuts and thin walls (<1 mm). Investment casting excels at producing features like turbine blades with 0.5 mm wall thicknesses.
Material Waste: Sand casting generates 15–30% scrap; die casting recycles 95% of excess material. Investment casting wastes 10–20% due to ceramic shell breakage.
4. Industry Applications: Where Each Method Shines
Sand Casting: Construction machinery, marine components.
Die Casting: Automotive transmissions, consumer electronics housings.
Investment Casting: Medical implants, defense hardware.
A recent study found that 34% of aluminum part failures stem from mismatched casting methods。