A 101 Guide to Sand Casting

Molten iron being poured into mold during sand casting process

For millennia, sand casting has offered an indispensable way to create large volumes of similar products around the world. Manufacturing and engineering companies value sand casting for its ability to produce highly complex casts that work with many different metal alloys for large and small projects; more than 60% of all metal castings rely on sand casting process technologies.

Sand casting employs nonreusable sand molds to create metal castings. Sand casting produces parts ranging from very small (less than a pound) to very large and complex parts. Because sand casting can create products across a wide range of shapes, sizes, and materials, sand-casted products are:

  • Easily recyclable
  • Inexpensive
  • Able to withstand high temperatures
  • Suitable for low- and high-volume production
  • Able to work with almost any metal alloy 

Selecting the Proper Sand

Different types of sand offer different casting possibilities. The ideal sand should hold up under mechanical stress but also be permeable enough to allow gasses and steam to escape during sand casting. 

The chosen sand must also incorporate ideal flowability levels for your project, and its moisture content should be chosen with care—low moisture content breaks the mold apart, whereas too much could lead to trapped steam bubbles in the mold.

Sand grain shape and size also affect mold quality, as well as the sand’s ability to withstand extreme heat (also known as refractory strength), its ability to collapse under force, and its reuse capabilities (after sand conditioning).

Sand Casting Process

The sand casting process consists of six basic steps to create a metal cast: 

  1. Workers place the pattern into the sand mold 
  2. They then place the pattern and sand in a gating system 
  3. The gating system creates a cavity in the sand, after which the pattern is removed
  4. Molten metal is poured into the cavity 
  5. The metal cools and sets
  6. Workers break away the sand mold and remove the casting

Methods of Sand Casting

Sand casting typically employs one of three methods:

  • Green sand — Sand casters often use green sand to create a mold because of its solid performance and low costs. Typical green sand mixtures contain 7% clay, 4% water, and 89% sand, thus providing the proper levels of strength, permeability, reusability, and collapsibility desired for sand casting projects.
  • Cold setting processes — Cold setting uses nontraditional binders, resulting in a sand-casting process that does not rely on heat to perform well. Cold setting processes chemically bond at room temperature when mixed with sand. While relatively new, this process has grown in popularity because of its exceptional dimensional accuracy.
  • Shell molding — Shell molding uses a mixture of dry, fine silica sand to create casts with smooth finishes. Workers mix this sand with 3–8% thermosetting resin and minimal clay content and then drop it onto a heated pattern plate, creating a thick (6 mm) shell that they then heat for several minutes to cure the shell.

Sand Casting Solutions

A diverse range of facilities offer B2B sand casting services for large-volume projects at affordable prices. If you’re looking for a low-cost, easily recyclable, and flexible technology to create superior metal casting, sand casting offers an indispensable way to improve your production line.

 

Image credit: Mr.1 / Shutterstock.com

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