Sand Casting: Mold, Pattern and Core

Distinguish a sand casting mold, pattern and core, understand their roles in shaping metal, and recognise where patternless methods differ.

In sand casting, a mold contains the space that liquid metal fills to form a casting. A pattern is an object used to shape that space when making a conventional sand mold. A core shapes a region that the main pattern cannot readily form, often an internal passage. The three names identify different objects and roles. SFSA foundry definitions · Reliance mold components

Mold and mold cavity

The mold is the surrounding form. The mold cavity is the space intended to become the casting when the metal solidifies. SFSA distinguishes that cavity from metal-delivery channels and feeding reservoirs. Those features may belong to the complete mold system without belonging to the finished part’s shape. SFSA Mold and Mold Cavity

Sand molds are normally broken apart to release the casting. A mold’s role in receiving the metal therefore differs from the pattern’s role in producing the mold. Reliance sand-mold explanation

Pattern and core

Object	Basic role	Relationship to the metal
Pattern	Forms the mold cavity	Removed before pouring
Mold	Holds the casting space	Surrounds the metal
Sand core	Forms a passage or other feature	Keeps metal out of that space

The table describes removable-pattern sand casting. A core is not the pattern itself, and neither is the finished casting. SFSA Pattern and Core · Reliance pattern extraction · Reliance core explanation

For example, consider a hypothetical hollow body. The mold can define its outside surfaces, while a placed sand core defines an internal passage. Metal fills the intended space around the core. This illustrates geometry only; it does not establish core supports, wall dimensions or a safe pouring procedure. Core function

Not every sand mold needs a physical pattern

The conventional relationship is not the only manufacturing route. ACTech describes both model-based and model-free sand-mold manufacture, including direct printing of mold sections and cores. A patternless route changes how the mold is made; a mold and a core still have distinct shaping functions. ACTech mold-making methods

Boundaries of these terms

This explanation concerns sand casting. It does not make every casting mold disposable, every core a sand core, or every pattern removable. Other casting routes need their own definitions. A familiar name also does not establish interchangeability with an injection-molding tool component.

Use the casting knowledge section for connected concepts. Detailed mold design, allowances and process conditions require separate evidence and engineering review.