Machinery's Handbook, 31st Edition
1498 SAND CASTING Features of Sand Molds.—Major features of sand molds (most shown in Fig. 2) are:
Cope: The top half of the flask, mold, or core. Drag: The bottom half of the flask, mold, or core.
Core: A core part is inserted into the mold cavity to produce a hole within the mold. Core Print: The region added to the pattern, core, or mold to locate and support the core. The prints are made of such a size and shape that it would be impossible to set the core in any position except the proper one. Mold Cavity: The combined open area in the molding material and core, where the liquid metal solidifies to produce the casting. Gating System: The network of connected channels that allows molten material to flow into the mold cavity; it includes the sprue, riser, runners, and gates. Pouring Cup or Basin: The part of the gating system that initially receives the molten metal from the pouring vessels and controls its delivery to the rest of the mold. Sprue: The vertical part of the gating system that connects the pouring cup and runners. The liquid metal enters into the mold cavity through the sprue. Runners: The horizontal portion of the gating system, cut into the drab part of the mold, which connects the sprues to the gates. Riser: This part of the gating system normally is used to identify the filling position of the liquid metal in the mold. It also acts as a reservoir for extra molten metal to compensate for shrinkage during solidification. Gates: The controlled entrances from the runners into the mold cavities. Properly de- signed gates admit liquid metal into the mold cavity without turbulence. Vents: These small holes, in all parts of the mold, provide passage for gases to escape during pouring and solidification of mold metals. Parting Line or Parting Surface: The interface line between the cope and drag halves of the mold or flask. Draft: The taper on the pattern that allows it to be easily withdrawn from the mold. Core Box: This is the mold or die used to produce the cores. Patterns.—Patterns are used to mold the sand mixture into the shape of casting. They may be made of wood, plastic, or metal. Because patterns are used repeatedly to make molds, the strength and durability of the materials selected must reflect the number of castings that the mold will produce. Patterns usually are coated with a parting agent to facilitate their removal from the molds. There are four types of patterns: solid one-piece patterns, split patterns, match-plate patterns, and cope-and-drag patterns. One-Piece Patterns: Also called loose or solid patterns , one-piece patterns are used for simple shapes and low-quantity production. They usually are made of wood and are inexpensive. Split Patterns: These two-piece patterns are made so that each part forms a portion of the cavity for the casting, enabling casting of complicated shapes.
Fig. 6. Match-Plate Pattern Match-Plate Patterns: These two-piece patterns are constructed by securing each half of one or more split patterns to the opposite sides of a single plate (Fig. 6). The gating sys- tem can be mounted on the drag side of the pattern.
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