Chapter 11 Flashcards
Define: Sand Casting
Or “Sand-Mold Casting,” consists of pouring molten metal into a sand mold, allowing the metal to solidify, and then breaking up the mold to remove the casting.
Define: Pattern
A full-sized model of the part, enlarged to account for shrinkage and machining allowances in the final casting. Generally made of wood, plastics, or metal.
Define: Solid vs Split vs Match Plate vs Cope-and-Drag Patterns
Solid: Same geometry as casting (enlarged for shrinkage and machining)
Split: Split into two pieces, dividing the part along a plane of coinciding with the parting line of the mold.
Match-Plate: the two pieces of a split are attached to opposite sides of a wood or metal plate (used for higher production quantities)
Cope-and-Drag: Similar to match plate other than that the two pieces are attached to separate plates. Includes a gating and riser system.
Define: Core
A full-scale model of interior surfaces of the part which is inserted into the mold cavity prior to pouring. Used for complex internal geometry.
Define: Chaplet
Supports for the internal cores, that are made of metal with higher melting temperature than the casting. Cut off from casting at the end.
Define: Flask
The container used to house the pattern and compacted molding sand for casting.
Define: Green Sand vs Dry Sand Molds
Green Sand: Molds made of a mixture of sand, clay, and water. “Green” refers to the moisture in the sand at the time of pouring.
Dry Sand: Molds made using organic binders rather than clay and then the mold is baked to add strength to the mold and harden the cavity surface.
Define: Shell Molding
Casting process in which the mold is a thin shell made of sand and held together by a thermosetting resin binder.
Define: Expandable Polystyrene Process (Lost Foam)
Or “Lost Foam Process, Lost-Pattern Process, Evaporative-Foam Process, and Full-Mold Process;” In which sand is packed around a foam pattern that vaporizes when the molten metal is poured into the mold.
Define: Investment Casting (Lost Wax)
In which a pattern is made of wax, which is coated with a refractory material to make the mold, after which the wax is melted away prior to pouring the molten metal.
Define: Pattern Tree
Series of several separate wax pieces attached to a wax sprue to form a geometry that will be cast out of metal
Define: Plaster vs Ceramic Mold Casting
Plaster: Similar to sand casting except that the mold is made of plaster instead of sand. Additives such as talc and silica flour can be mixed to control contraction and setting time, reduce cracking and increase strength.
Ceramic: Similar to plaster molding except that the mold is made of refractory ceramic materials that can withstand higher temperatures than plaster.
Define: Die Casting
A permanent-mold casting process in which molten metal is injected into the mold cavity under high pressure, which is maintained during solidification. Two types: hot and cold/
Define: Cold vs Hot Chamber Machines
Hot: metal is melted in a container attached to the machine and a piston is used to inject the liquid metal under high pressure into the die.
Cold: molten metal is poured into an unheated chamber from an external melting container and a piston is used to inject the metal under high pressure into the die cavity.
Define: Flash
When liquid metal under high pressure squeezes into the small space between the die halves at the parting line or into clearances around the cores. Must be removed once the casting is cooled.
