Create internal cavities Core‑Making Create internal cavities

Most common core materials 1. green sand cores ‑ little strength 2. dry sand cores ‑ sand and binders ‑ baked

Cores must be strong yet collapsible

base sand: silica

binders: Organic Inorganic flour, starch, resins, oils ‑ liquid binders Inorganic clays, cement

Two problems with making cores: 1. gas ‑ caused by excessive organic binders 2. moisture

Cores usually made in a core box made of wood or matel box is half, split, or booked type

Making a core: (p. 65) 1. sand and binder are mixed in muller so the grains of sand are coated with the binder 2. core sand rammed into core box 3. surface is struck off flat 4. flat plate clamped to flat surface of box 5. box and plate are rolled over together 6. box lifted off 7. sand core is left on the plate to be dried in oven

irregular ‑ shaped cores may be supported by a contoured metal plate called a "drier”

cores are rammed by: 1. Hand 2. Jolting 3. Squeezing 4. blowing (most common) ‑ core box requires vents for escaping air and flowability of sand is a factor

Some continuous cross section cores are extruded (CAT)

Positioning the core: Core pints ‑ recesses in the sand to support the core Chaplets ‑ (p. 66) metal props that become part of the casting ‑ made of same metal as casting

Mold must be vented to allow core oil binder gases to escape form the mold