Aim

The aim of this experiment is to prepare a sand mould for casting a flange coupling.

Materials Required

• Pattern: A replica of the desired flange coupling, usually made of wood.

• Moulding Sand: A mixture of silica sand, clay (bentonite), and water.

• Parting Sand: Fine, dry sand to prevent the moulding sand from sticking to the pattern.

• Facing Sand: Fine, new sand placed directly next to the pattern for a smooth casting surface.

• Core: A pre-formed sand shape used to create the internal bore of the flange coupling.

• Chaplets: Small metal supports used to hold the core in place.

Tools Required

• Moulding Box (Flask): A two-part container consisting of the drag (bottom half) and the cope (top half).

• Riddle/Sieve: To sieve the moulding sand and remove lumps.

• Shovel: For mixing and moving the moulding sand.

• Rammer: A tool to compact the sand around the pattern.

• Strike-off Bar: A flat bar to scrape off excess sand.

• Vent Rod: A pointed rod to create vent holes for gas to escape.

• Sprue Pin: A tapered pin to create the vertical channel for pouring molten metal.

• Gate Cutter: A tool to create the horizontal channel (gate) connecting the sprue to the mould cavity.

• Lifter: A flat, thin tool to lift loose sand.

• Moulding Trowel: For smoothing and repairing the mould surface.

• Draw Spike: A tool to pull the pattern out of the sand mould.

• Bellows: To blow away loose sand from the mould cavity.

Experimental Procedure

Step 1: Preparing the Drag

• Place the drag on a moulding board, pin-side down.

• Place the flange coupling pattern in the centre of the drag. Sprinkle parting sand over the pattern and board.

• Sieve a layer of facing sand over the pattern, then fill the drag with moulding sand.

• Compact the sand with a rammer, ensuring it is firm and uniform.

• Scrape off the excess sand with a strike-off bar to make the surface level.

• Create vent holes using a vent rod, piercing the sand down to the pattern.

Step 2: Preparing the Cope

• Flip the drag and place it on the moulding board. Place the cope on top of the drag, aligning the pins.

• Insert the sprue pin and riser pin (if required) at a suitable distance from the pattern.

• Sieve a layer of facing sand over the pattern and surrounding areas.

• Fill the cope with moulding sand, compact it with the rammer, and strike off the excess.

• Carefully remove the sprue pin and the riser pin.

• Make vent holes in the cope.

Step 3: Finishing the Mould

• Separate the cope from the drag by lifting it carefully.

• Use a draw spike to gently tap the pattern and then pull it out of the drag cavity.

• Place the core, which will form the internal bore, into the core print of the mould. Use chaplets to support it if necessary.

• Using a gate cutter, create the runner and gate channels connecting the bottom of the sprue to the mould cavity.

• Blow away any loose sand particles from the mould cavity and channels using bellows.

• Close the mould by carefully placing the cope back on the drag, ensuring the pins are aligned.

• Secure the cope and drag with clamps.

Precautions

• Ensure the moulding sand has the correct moisture content to avoid defects.

• Ramming should be uniform; under-ramming leads to weak moulds, while over-ramming makes the mould too hard.

• Use parting sand generously to prevent the pattern from sticking and the two flask halves from fusing.

• Handle the pattern carefully during withdrawal to prevent damage to the mould cavity walls.

• Ensure there are enough vent holes to allow trapped gases to escape, preventing porosity.

• Align the cope and drag perfectly before clamping to ensure the mould cavity is correctly positioned.

• Secure the core firmly in place to prevent it from shifting during pouring.

Result

The final result is a prepared sand mould with a clean, well-defined cavity in the shape of a flange coupling. This mould is now ready for the pouring of molten metal. The integrity of the mould, the clarity of the cavity details, and the secure placement of the core are essential for a successful casting.

Line Diagram

Figure A: Drag preparation showing the flange coupling pattern and sand. Figure B: Cope preparation showing the sprue pin, riser, and vent holes. Figure C: The completed mould assembly, showing the pouring basin, sprue, runner, gate, mould cavity, core, and vent holes.