Aim:

The aim of this experiment is to prepare a sand mould for casting a solid bearing.

Materials Required

• Pattern: A replica of the desired solid bearing, typically made of wood or metal.

• Moulding Sand: A mixture of silica sand, clay (bentonite), and water, which holds its shape after compaction.

• Parting Sand: Fine, dry sand used to prevent the moulding sand from sticking to the pattern and the cope and drag sections.

• Core: A pre-formed shape, usually made of sand, placed inside the mould to create an internal cavity in the casting. (While a solid bearing typically doesn't have a core, it's a key component in more complex castings.)

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

Tools Required

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

• Riddle/Sieve: Used to sieve the moulding sand to remove impurities and lumps.

• Shovel: For mixing and moving the moulding sand.

• Rammer: A tool with a flat or peen end used to compact the sand around the pattern.

• Strike-off Bar: A flat metal bar used to scrape off excess sand from the top of the flask, ensuring a level surface.

• Vent Rod: A thin, pointed rod used to create vent holes in the mould for gases to escape during pouring.

• Sprue Pin: A tapered pin used to create the vertical channel (sprue) through which molten metal is poured into the mould.

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

• Lifter: A flat, thin tool used to lift loose sand from the mould.

• Moulding Trowel: Used for smoothing and repairing the mould surface.

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

• Bellows: Used to blow away loose sand particles from the mould cavity.

Experimental Procedure

Step 1: Preparing the Drag

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

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

• Sieve a layer of moulding sand over the pattern using a riddle, and then fill the drag with sand using a shovel.

• Compact the sand with a rammer. The ramming should be uniform to ensure the mould is firm.

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

• 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 the 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 sand.

• 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 lift it out of the drag cavity.

• Using a gate cutter or a spoon tool, 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 or weights to prevent them from separating when the molten metal is poured.

Precautions

• Ensure the moulding sand has the correct moisture content to avoid defects like blows and scabs.

• Ramming should be uniform; over-ramming can make the mould too hard, while under-ramming makes it weak.

• Use parting sand generously to prevent the pattern from sticking and the cope and drag from fusing.

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

• Make sure there are enough vent holes to allow trapped gases to escape, preventing porosity in the final casting.

• Align the cope and drag perfectly before clamping to ensure the two halves of the mould cavity are correctly positioned.

Result

The final result of the experiment is a prepared sand mould with a clean, well-defined cavity in the shape of a solid bearing, ready for the pouring of molten metal. The mould's integrity and the clarity of the internal details determine the quality of the final casting. The mould should be free from cracks, loose sand, and other defects.

Line Diagram

Figure A: Drag preparation showing the pattern, moulding box (drag), and sand. Figure B: Cope preparation showing the sprue pin, cope, and vent holes. Figure C: The completed mould assembly, showing the pouring basin, sprue, runner, gate, mould cavity, and vent holes.