Shenzhen Alu Rapid Prototype Precision Co., Ltd.

White metal casting, also known as centrifugal rubber mold casting (CRMC) or spin casting, is a manufacturing process primarily used in the jewelry industry to produce low-cost, high-perceived-value items from low-melting-point alloys known as "white metals." These alloys have a bright, silvery appearance and are valued for their malleability, ease of casting, and ability to be plated or finished for decorative purposes. The process is similar to lost-wax casting but employs vulcanized rubber molds and centrifugal force to fill intricate details efficiently, making it ideal for mass-producing small, complex shapes.

Key Materials

1.Alloys: Typically tin-based (e.g., pewter with 92% tin or lower blends like 36% tin), combined with lead (for malleability and cost), antimony (for hardness), bismuth (for luster and expansion), copper (for strength), or cadmium (for ductility and lower melting points). Alloys melt at around 450–600°F (232–316°C) and must use virgin metals to avoid contaminants like zinc or iron, which can cause defects such as porosity or dross.

2.Molds: Made from vulcanized rubber sheets (e.g., silicone or organic black/white rubber with 60–70 durometer hardness) for durability and detail retention.

3.Other Supplies: Models from wax, photopolymers, or brass; talc or mica for mold release; flux (e.g., ammonium chloride) to reduce oxidation.

The Casting Process

1.Model Creation: Sculpt or machine a prototype (e.g., using CAD/CAM, wax carving, or photopolymer UV curing).

2.Mold Fabrication: Embed the model in rubber sheets, vulcanize under heat and pressure (295–315°F for 1 hour per inch of thickness), then cut channels for metal flow (gates, runners) and gas escape (vents).

3.Preparation and Pouring: Preheat the mold, apply release agents, and melt the alloy to 50°F above its liquidus temperature. Pour into a central basin on a spin caster machine.

4.Centrifugal Casting: Spin the mold at 250–650 RPM for 1–5 minutes, using centrifugal force (up to 40 PSI) to force molten metal into cavities.

5.Demolding and Finishing: Cool, remove castings, clip excess metal, and finish via sanding, buffing, vibratory tumbling, or plating (e.g., nickel, gold, or silver for a premium look).

Applications

This technique is common for affordable jewelry (e.g., rings, pins, keychains), awards, figurines, model railroad parts, and novelties like ornaments or hatpins. It's also used in hobbies for casting miniatures and in industrial settings for bearings or bushings due to the alloys' low friction.