Shenzhen Alu Rapid Prototype Precision Co., Ltd.

Sand casting is one of the oldest and most versatile metal casting processes, used to create parts by pouring molten metal into a mold made of compacted sand. It's ideal for beginners or small-scale projects, like backyard foundries, but requires safety precautions due to high temperatures (often 1,200–1,500°F or 650–815°C). Always wear protective gear: heat-resistant gloves, face shield, apron, and work in a well-ventilated area away from flammables.

Materials and Tools Needed

Sand: Fine, dry silica sand mixed with a binder like clay (greensand) or resin for strength.

Pattern: A replica of the part you want to cast, made from wood, plastic, or metal (slightly oversized to account for shrinkage).

Flask: A two-part metal frame (cope and drag) to hold the sand.

Gating system components: Sprue (pouring hole), runners, and risers (vents for gases and shrinkage).

Metal: Low-melting alloys like aluminum, bronze, or zinc for beginners.

Melting equipment: Crucible, furnace (propane or electric), tongs, and ladle.

Other: Rammer (for compacting sand), parting dust (to separate mold halves), and finishing tools (files, grinder).

Step-by-Step Process

1.Create or Prepare the Pattern

Design and carve your pattern to match the desired final shape, including draft angles (2–5°) for easy removal. If using cores (for internal features like holes), make them separately from sand or resin. Place the pattern on the drag (bottom flask half) on a flat surface.

2.Prepare the Sand Mold

Mix your sand to a moist, workable consistency. Dust the pattern and flask with parting powder to prevent sticking. Fill the drag with sand around the pattern, compact it firmly using a rammer (tap evenly to avoid voids). Flip the drag, add the cope (top half), and align with dowel pins. Repeat filling and compacting for the cope, then cut a sprue hole (pouring channel) at one end and runner/gate channels to direct metal flow. Add risers if needed for even cooling. This creates a cavity matching your pattern.

3.Remove the Pattern and Assemble the Mold

Carefully lift the cope, remove the pattern from the drag (wiggle gently if stuck), and place any cores into the cavity. Realign and clamp the cope and drag together securely with straps or weights to prevent shifting during pouring.

4.Melt the Metal

Load your chosen metal into a crucible and heat it in a furnace until fully molten (check with a pyrometer or by skimming dross—impurities). Skim off oxides for clean metal. Preheat the mold slightly (100–200°F) to reduce thermal shock.

5.Pour the Molten Metal

Using tongs, transfer the crucible to a ladle. Pour steadily into the sprue, filling the cavity through the runners. Avoid turbulence to minimize defects like porosity—pour quickly but controlled. Fill risers last to compensate for shrinkage as it cools.

6.Cool and Remove the Casting

Let the mold cool undisturbed for 10–60 minutes (depending on size and metal). Once warm (not hot), break apart the flask and dig out the casting. Knock off sand residue with a brush or air blast.

7.Finish the Casting

Cut off the gating system with a hacksaw or cutoff wheel. File, grind, or sand rough edges. Inspect for defects (e.g., cracks or incomplete fills) and heat-treat if needed for strength. For complex parts, secondary machining may be required.