Shenzhen Alu Rapid Prototype Precision Co., Ltd.

Metal casting is a manufacturing process where molten metal is poured into a mold to create a desired shape, which solidifies into a part. It's one of the oldest techniques for producing complex metal components, used for everything from jewelry to engine blocks. Common methods include sand casting (versatile and beginner-friendly), die casting (for high-volume production), and investment casting (for precision parts). 

Materials and Tools Needed

Pattern: A replica of the part (e.g., wood, plastic, or 3D-printed model).

Molding sand: Green sand (sand + clay + water) for the mold.

Mold frame (flask): Two-part box (cope and drag) to hold the sand.

Crucible: Heat-resistant container (graphite or clay-graphite) for melting metal.

Furnace: Propane torch, charcoal forge, or electric melter.

Tongs and ladle: For handling hot metal.

Metal: Aluminum, bronze, or lead for beginners (lower melting points ~660°C for aluminum).

Parting dust or talc: To prevent sand sticking.

Tools: Rammer (for packing sand), vent wire (for air holes), and finishing tools (files, sandpaper).

Step-by-Step Guide to Sand Casting

Here's a detailed process for creating a simple metal part, like a bracket or gear blank. Total time: 2–4 hours per cast, plus cooling.

1.Prepare the Pattern

Create or obtain a pattern slightly larger than your final part (to account for shrinkage, ~1–2% for most metals). Coat it with a release agent like wax or petroleum jelly to ease removal.

2.Set Up the Mold Frame

Place the bottom half of the flask (drag) on a flat surface. Position the pattern in the center, core side up if using a core (for hollow parts). Dust the pattern with parting compound to prevent sand adhesion. 

3.Mix and Pack the Sand (Molding)

Mix molding sand to a damp, peanut-butter-like consistency (typically 90% sand, 7% clay, 3% water). Sift it evenly over the pattern in the drag, then ram (pack) it firmly with a tool to avoid voids. Add a second layer if needed for depth.

Flip the drag, add the top flask (cope), and pack sand around a matching pattern impression or runner/gate system (channels for metal flow). Use a vent wire to poke holes for gas escape. 

4.Remove the Pattern and Assemble the Mold

Carefully lift the cope, remove the pattern from the drag, and add any cores (sand inserts for internal shapes). Realign and clamp the cope and drag together. Seal edges with more sand or loam to prevent leaks.

5.Melt the Metal

Load scrap or ingot metal into the crucible. Heat in your furnace to the melting point (e.g., 700–800°C for aluminum—use a pyrometer for accuracy). Skim off impurities (dross) from the surface. Stir gently to ensure even temperature. 

6.Pour the Molten Metal

Using tongs, remove the crucible and pour steadily into the mold's sprue (pouring hole). Fill completely but avoid overflowing. The metal will flow through gates into the cavity. Do this quickly to minimize cooling.

7.Cool and Solidify

Let the mold cool naturally for 10–30 minutes (depending on size). Metal shrinkage may create a slight contraction—insulate the mold if needed for slower, even cooling to reduce cracks.

8.Break the Mold and Finish the Casting

Separate the flasks and break away the sand (it can often be reused). Remove the rough casting with a hammer or chisel. Trim excess (sprues, gates) with a hacksaw, then file/sand for smoothness. Heat-treat if required for hardness (e.g., annealing).