foundry molds

Pattern Definition

The pattern is a replica of the final product, minus any necessary machining or surface finishing needed prior to assembly of the final product.  A sand cast foundry creates a pattern or mold from wood, aluminum, steel, or other materials to make a shape that will eventually make an impression in the sand.  The pattern makes its impression in the sand, the molding machine adds pressure to the sand squeezing the sand around the pattern.  The pattern is vibrated loose from the now hard sand, leaving the desired shape in the sand. This impression is subsequently filled with molten aluminum.  And when the aluminum is solidified, the casting is shaken out of the mold.

Types of foundry Patterns

There are different kinds of foundry patterns depending on the complexity of the final casting and the casting method. Common types include:

  • Solid Patterns – Single-piece patterns ideal for simpler designs without intricate cavities.
  • Split Patterns – Two-part patterns that are separated to help in producing detailed shapes.
  • Match Plate Patterns – Patterns mounted on a plate to allow for high-volume production by aligning with the mold’s top and bottom sections. Each pattern type serves a specific casting need, depending on factors like the complexity of the shape, volume of production, and precision required.
foundry pattern
engine parts aluminum casting foundry

Pattern Allowances in Casting

Patterns are not exact replicas of the final product but incorporate certain allowances:

Cores & Core Boxes for Internal Features

For castings that require internal cavities or hollow sections, cores or core boxes are used alongside the main pattern. Cores are placed inside the mold cavity to block out specific areas where metal should not flow, creating hollow sections within the final casting. Core patterns are carefully designed to match the overall casting dimensions and ensure that internal shapes are as precise as external ones.

foundry pattern

Learn More Aluminum Foundry Terms