Moulding tools, equipment and hand moulding practice
Domain 4 - Moulding tools, equipment and hand moulding practice
This domain tests the hand tools of a moulder, the sequence of making a green-sand mould, and the reasons behind each step.
Tools and equipment
Shovel, riddle, rammer, trowel, slick, lifter, swab, sprue pin, vent wire, gate cutter, draw spike, mallet, strike-off bar and bellows are hand tools. The flask has a cope and a drag; clamps or weights hold it closed. Moulding machines include jolt, squeeze, jolt-squeeze and sand slingers. A muller prepares sand; a core oven cures oil-sand cores.
Hand moulding sequence
- Place the drag on a board, set the pattern, and dust with parting sand.
- Cover the pattern with facing sand, then fill with backing sand.
- Ram in layers, vent the drag, and roll it over.
- Fit the cope, set the sprue pin and riser pin, ram, and vent.
- Lift the cope, draw the pattern with a draw spike, repair the mould, and cut the gate.
- Set cores, close the mould, clamp or weight it, and pour.
Worked example
A moulder rams the sand next to the pattern with heavy blows until the sand is very hard. The resulting mould has low permeability and the casting shows blows. Reason: permeability depends on the voids between sand grains; over-ramming closes them. The correct practice is firm, even ramming in layers, harder away from the pattern and lighter near it, with vent holes taken through to the mould surface but not through the pattern face.
Traps
Do not vent through the pattern cavity. Rap the pattern before drawing it, but do not enlarge the mould excessively. A sprue should taper downward, not upward. Swabbing adds water, so use it sparingly. Forgetting weights or clamps allows the cope to lift when metal enters.