SAND-CASTING MOLDS

Sand casting is the most common casting technique. The phrase “sand casting mold” will be used to describe the main characteristics of the mold. Many of these characteristics and names may be found on molds used in various casting methods. A cross-section of a common sand casting mold is displayed with some text. The form is split into two sections: top and bottom. The top half is the top half of the mold, while the bottom half is the bottom half of the mold. These two mold components are stored in a box called the bottle, which is divided into two halves: one for the top mold and one for the bottom mold. The mold’s two halves are split at the dividing line.

The hollow is formed in sand casting using a mold made of wood, metal, plastic, or other materials and shaped like a molded component (and other consumable manufacturing techniques). The cavity is formed by sand filling the area surrounding the mold, with each upper and lower mold taking about half of the space, such that when the mold is removed, the remaining void is in the mold that must be cast. The pattern is usually made overly large to prevent the metal from shrinking as it hardens and cools. Mold sand is moist and contains a binder to maintain its shape.

The molding chamber provides the casting’s outer surface. The casting may also have an inner surface. A core that is placed in the mold chamber to define these surfaces determines the internal geometry of the component.

A sand casting’s core is usually formed of sand, although it may also be constructed of metal, gypsum, or ceramics.

A sprue system in a mold is a channel or network of channels via which molten metal flows into the cavity from the mold’s outside. A sprue (sometimes spelled sprue) is a ventilation system in which metal enters a trough leading to the main chamber. A drain cup is often used at the top of the sprue to minimize spatter and turbulence as metal flows into the sprue. The diagram depicts it as a simple cone-shaped funnel. Some of the nozzles are shaped like bowls and have open passageways leading to the gate.

In addition to the gating system, every casting with significant shrinkage requires a riser connected to the main cavity. The riser is a reservoir in the mold that serves as a source of liquid metal for the casting in order to compensate for solidification shrinkage. To serve its function, the riser must be designed to freeze after the main fill.

Before the metal flows into the mold, the air that was previously filled the cavity and the hot gas generated by the molten metal reaction must be removed. Sand’s intrinsic porosity, for example, allows air and gas to escape through the hollow walls used in sand casting. Tiny vents are drilled in the mold or small vents are machined on the connecting line to discharge air and gas from permanent metal molds.