Shenzhen Alu Rapid Prototype Precision Co., Ltd.

The required vacuum pressure for casting metal varies significantly depending on the specific process, metal type, part complexity, and desired quality (e.g., reducing porosity or improving detail fill). There is no single universal value, as "vacuum casting" encompasses several techniques.

1.Vacuum-Assisted Investment Casting (Common for Jewelry, e.g., Lost-Wax for Gold/Silver)

This is prevalent in small-scale and jewelry applications. The vacuum pulls air from the porous investment mold during/after pouring to help molten metal flow into fine details and reduce gas entrapment.

Typical levels: 20–29 inches of mercury (inHg) at sea level.Many machines aim for a good seal at ≥20 inHg before pouring.

Full vacuum is often ~29 inHg (near atmospheric pressure differential, equivalent to ~0 psi absolute or -14.7 psi gauge).

2.Vacuum Die Casting (Industrial, e.g., Aluminum/Magnesium Automotive Parts)

Air is evacuated from the die cavity before high-pressure injection to minimize gas porosity.This is a partial vacuum; full vacuum isn't needed due to the high injection pressure.

A.Typical levels:<50–300 mbar absolute pressure (higher vacuum is better for quality).Standard vacuum-assisted: 60–300 mbar.

B.High/super vacuum:<50 mbar or lower for heat-treatable/weldable parts.

3.Vacuum Pressure Casting or Counter-Pressure Variants

Combines vacuum on the mold with overpressure on the melt.

Differential pressures:Often 50 kPa (500 mbar) added on the metal side, with vacuum below.Used for complex thin-walled parts.

General Notes

A.Higher vacuum (lower absolute pressure, e.g., closer to 0 mbar or 29+ inHg) generally improves fill, reduces porosity/oxidation, and enhances detail—especially for intricate or thin sections.

B.For hobby/jewelry lost-wax: A basic vacuum pump achieving 20–25 inHg is often adequate and common in commercial machines.

C.Industrial/aerospace (e.g., titanium/superalloys): Much higher vacuums (low micron levels) in full vacuum melting/casting chambers to prevent oxidation.

D.Units conversion: 29.92 inHg ≈ 1013 mbar (atmospheric) → full vacuum gauge reading of -29 inHg ≈ 0 mbar absolute.